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A subwoofer journey...(CSS SDX12 + 3x APR12 Passive Radiators)

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  • A subwoofer journey...(CSS SDX12 + 3x APR12 Passive Radiators)

    As far as build stories go, this one will probably not yield much fruit for a little bit. That said, I have some questions for the community regarding subwoofer design before making any further purchases. I already have 4x Dayton UM15-22 subwoofers expected this Saturday for another application...I'm sure the subwoofer gods will eat me alive for not springing for the UM18-22 instead, but this is what I settled on for the home theater. Note that these purchases are largely made due to the current sale Parts Express has going on and the belief they will only be getting more expensive down the line.

    Here's the goal - I want one (or two) individual subwoofers for my music room (though they may be multi-component). The key here being they must have a small footprint, but can be relatively tall. I'm imagining something along the lines of a loudspeaker in terms of shape and dimension. Funding can be...mostly anything at this point, so I'll entertain most ideas though I'll probably stick with Dayton Audio products considering the value. I do not have an amplifier for this and have not settled on anything, though I am a bit enamored with the Hypex FA502 plate amplifier and, to a lesser extent, the Behringer NX series pro amplifiers. Given the small footprint I believe 10" or 12" front-firing subs would work the best...leaning towards the 10". I briefly modeled the UM15-22 in a side-firing situation but with only, say, a volume of 3-4 ft3 the box qtc is quite high (approaching 1).

    As this is primarily for music I tend to think I want a sealed box to keep the box qtc at a reasonable level and keep 'boominess' to a minimum, with a Linkwitz transform to bring up the lower bass a smidge. My initial thought was to have 2-4 subwoofer drivers per box in a vertical alignment, resulting in a box around 12 inches wide, 24-48 inches tall, and maybe 16-18 inches deep. The first two dimensions being required based on the physical size of the drivers and the depth being the control for volume.

    So, questions:
    1. First, am I missing something obvious about achieving reasonably deep, tight, effortless bass in a small footprint? I understand that in a sealed cabinet that would tend to require a lot of power.
    2. I have not decided on a driver at this time, though I imagine it'll either be an Ultimax or one from the RS line. I've only modeled the Ultimax right now but will be working with the others tonight. Are there any general considerations for the RS line that I should keep in mind? I know Jon likes the HF? Or was it the HO? But I think that was more for their upper bass capabilities than low bass?
    3. Keeping in mind the Ardents already employ four 9-10" sealed 'subwoofers', will I be able to achieve significant bass to justify the expense for this project when only using small drivers?
    4. I would like to ensure the quality of the subwoofers approach that of the Ardents themselves (in terms of distortion and delay). Will the Dayton products approach that, or should I explore other options? Perhaps the CSS SDX10? Or even the CSS SDX12? I like the idea of XBL2 (and am curious about the extreme weight of the SDX12) but I'm not sure I'd be ready to spring for 'new' Adire products at this point, especially since several have graphics on the cone.
    Anyway, I'm sure I'm missing some other things so please feel free to tear apart my thoughts and assumptions!

    Edit: It was decided to use the CSS SDX12 along with three CSS passive radiators. Read on below for the rationale and build log!
    Last edited by technodanvan; 17 January 2023, 19:20 Tuesday. Reason: minor updates
    - Danny

  • #2
    I'm churning on my To-Do list still today, but I'll get back to you with some thoughts and alternatives tomorrow at breakfast!
    the AudioWorx
    Natalie P
    M8ta
    Modula Neo DCC
    Modula MT XE
    Modula Xtreme
    Isiris
    Wavecor Ardent

    SMJ
    Minerva Monitor
    Calliope
    Ardent D

    In Development...
    Isiris Mk II updates- in final test stage!
    Obi-Wan
    Saint-Saëns Symphonique/AKA SMJ-40
    Modula PWB
    Calliope CC Supreme
    Natalie P Ultra
    Natalie P Supreme
    Janus BP1 Sub


    Resistance is not futile, it is Volts divided by Amperes...
    Just ask Mr. Ohm....

    Comment


    • #3
      Thanks Jon, your input is always appreciated!

      The more I model and read about the SDX12 the more I want to do something with it. Seems like it was made for small boxes - both sealed and ported. Very impressive driver, but comes at a cost (literally). Two of them with 1000 watts each would approach 117dB, (probably) more than enough headroom for my purposes. Slot ported at 1.6ft3 (45L) and 23Hz provides an f3 around 25Hz; cone excursion would only become problematic around 17Hz - a non-issue for music, though a 'rumble filter' would be advised.


      The SDX12 is quite deep at >8 inches, but it would still allow for a side-firing situation to keep the box reasonably narrow. The slot port (fairly long at 50+ inches, but necessary to reduce chuffing and fit in the box) could wrap around vertically.
      ​​​​​​
      But how musical would that be, I wonder, compared to a sealed box between 0.8 and 1.5ft3 (23-42L)?

      Also, I could have a pair of Dayton 12" subs for roughly the same cost as a single SDX12, though they tend to require larger boxes for similar output.
      - Danny

      Comment


      • #4
        Knowing Jon, I'm betting on the SDX12 and a PR or two ..... 😄
        Hold on to your butts - It's about to get Musical!



        WEBSITE: http://www.smjaudio.com/

        Comment


        • #5
          Originally posted by technodanvan View Post

          As this is primarily for music I tend to think I want a sealed box to keep the box qtc at a reasonable level and keep 'boominess' to a minimum, with a Linkwitz transform to bring up the lower bass a smidge. My initial thought was to have 2-4 subwoofer drivers per box in a vertical alignment, resulting in a box around 12 inches wide, 24-48 inches tall, and maybe 16-18 inches deep. The first two dimensions being required based on the physical size of the drivers and the depth being the control for volume.

          So, questions:
          1. First, am I missing something obvious about achieving reasonably deep, tight, effortless bass in a small footprint? I understand that in a sealed cabinet that would tend to require a lot of power.
          2. I have not decided on a driver at this time, though I imagine it'll either be an Ultimax or one from the RS line. I've only modeled the Ultimax right now but will be working with the others tonight. Are there any general considerations for the RS line that I should keep in mind? I know Jon likes the HF? Or was it the HO? But I think that was more for their upper bass capabilities than low bass?
          3. Keeping in mind the Ardents already employ four 9-10" sealed 'subwoofers', will I be able to achieve significant bass to justify the expense for this project when only using small drivers?
          4. I would like to ensure the quality of the subwoofers approach that of the Ardents themselves (in terms of distortion and delay). Will the Dayton products approach that, or should I explore other options? Perhaps the CSS SDX10? Or even the CSS SDX12? I like the idea of XBL2 (and am curious about the extreme weight of the SDX12) but I'm not sure I'd be ready to spring for 'new' Adire products at this point, especially since several have graphics on the cone.
          Anyway, I'm sure I'm missing some other things so please feel free to tear apart my thoughts and assumptions!
          Good additional information. BTW, I like the CSS drivers, have some of the 10's on hand for a future project. I'm all in favor of enhanced linearity drivers when possible- like the XBL2, PuriFi VC design, etc. Sometimes, like the E180HE parts, they come with drawbacks, like lack of attention to inductivity modulation above the LF range.
          • Some General thoughts and questions...

          Your initial questions are interesting but still raise further questions in my mind- having been a working engineer, though I like adjectives, I prefer numbers! They give useful targets for development.... So when you say reasonably deep, tight, effortless bass in a small footprint, almost every part of that raises question marks! Not trying to pick on you, but for example, for you,
          • What is reasonably deep bass?
          • What is adequate LF SPL at the listening position?
          • How far is the listening position from where you will have speaker cabinets?
          • What is a small foot print for you?
          • What is a lot of power?
          • Are you familiar with Hoffman's Iron law, and why that completely supersedes notions about sealed versus reflex alignments?


          Hofmann theorized that when woofers are mounted in speaker enclosures, the designer would have to accept that there are three trade-offs. Hofmann argued that the designer had "...three parameters that cannot all be had at the same time. They are low-bass reproduction, small (enclosure) size, and high (output) sensitivity." Hofmann stated that designers could pick two of these three parameters, but in doing so, it would compromise the third parameter.[5]

          For example, a designer who wants good, deep low-frequency sound and high sensitivity can obtain these goals, but they will have to use a large speaker enclosure. Similarly, if a designer is forced by space constraints to use a very small cabinet, and they aim to get good, deep low-frequency sound, the sensitivity will be compromised (i.e., a small cabinet with deep bass would need a very powerful amplifier).

          This is just basic physics. And there are driver parameters which will give you good clues about what is going to work and what won't regarding enclosure size and what kind of alignment is feasible. We'll discuss those shortly. (Ever heard the term "monkey coffins"? That's what happens when you pick a nice low Qts, low cone mass driver with good sensitivity... then you try to get LF extension- requires a big box. Sometimes VERY big box! This is a good example of Hoffman's Iron Law. The Natalie P was an interesting attempt to balance those issues; though the base design had decent LF extension in a bookshelf speaker, if one was willing to go from 28L to 48L, then the real magic could happen. Direct example of Hoffman's Iron Law.)

          And of course, if you want a small box with extended low end, you have to chose a driver with the right design and T/S parameters to achieve that- so understanding your end goals in detail is the first step in doing the driver selection.


          One other thing- that whole boomy bass thing... if you spend some time with Unibox or VituixCAD or other LF enclosure design programs, one can certainly see a lot of potential for creating poorly designed bass reflex system, whether using ports or passive radiators. This is at times done deliberately for commercial designs to appeal to a naive class of new customers.

          An enclosure style sometimes designated as one of the worst in regards to "boomy" bass is the bandpass enclosure, which these days is popular for competition car audio bass setups. But guess what... it's all about the designer's choices and actions. In the 70's and 80's I worked on bandpass enclosure designs for Hi-Fi subwoofers, using Audax Pro drivers, and currently I have stuff in storage and have build one POC example using B&C 15NW100. I like bandpass setups, but they have very unique driver and design requirements. IMO the ideal bandpass woofer is a long throw pro woofer with a reasonably compliant suspension and an ultra low Qts- a value so low that making it nearly unusable for a normal box speaker, due to the difficultly in getting an alignment with LF extended response. In the right design bandpass enclosure, the enclosure totally defines the transfer function, and the lower the Qts of the driver, the better the fit of actual response to design target. Of course, for car audio the design target is much different than for a HiFi style subwoofer- narrow band output and high gain are the order of the day.

          But, using a pro part like the B&C 15NW100, and intelligent design choices, a very different result is possible - and thank heavens for VituixCAD compared with the manual calculations I had to do in the early 80's!


          Click image for larger version  Name:	Janus W1 VB2 50Hz Info 7-26.png Views:	0 Size:	359.5 KB ID:	927562


          This is a design with a deliberate slight up tilt towards the low bass, to optimize the LF extension range to about 20Hz. The basic driver Qts is 0.22, and the nominal driver Fs is 33Hz. The nominal driver sensitivity is 97 dB, and you could say that we're throwing away a lot of that sensitivity to force the response curve and extension you see here. And for what it does, this enclosure is relatively compact- the POC build was even more compact than this design example, but was mainly done to prove out the concepts and the ability to match the modeling in the real world. With different design parameters, say, reduce the flat LF extension to 30 Hz, sensitivity can be increased to the mid or upper 80's dB range.




          I'm not suggesting this for you, this is an R&D project of sorts for Steve's SMJ organization, more of a "What if?" kind of thing right now for the future development pipeline- this Neodymium pro woofer is a somewhat expensive piece. But Steve was curious about things off the beaten track that required an "interesting" enclosure construction to realize... something of his specialty, you could say!

          My other comments about "boomy bass" stereotypes touches also on design, and further on room setup.

          On the design side, though passive radiators have a rep (due to poor design choices?) for boomy bass and sloppy step response (doing a good sixth order design isn't trivial) one of my favorite builds so far for the combination of bass extension and articulation and transient definition is the Ardent D. It's a good PR design implementation, IMO, of course, but I do acknowledge that some of that may be due to the Accuton AS168 drivers. How articulate and dynamic it is has renewed my desire to get the Kurosawa's out of storage, and put them together, given the AS190 drivers and what by analysis and comparison to the Stereophile Measurements of the Tidal Audio Akira seems to be a superior LF design implementation.



          This is why the project I started for Steve for a compact LF system in a three way, originally with the Dayton E180HE-44 but now with RSS210HF-4, is using passive radiators. Originally intended for a more compact form factor, with the 8" drivers it grew a bit, and the midrange is far more linear than the E180HE drivers can deliver. Curious when an 8" driver outperforms a 7", but while the dual magnet motor of the E180HE works nicely below 120Hz, the lack of attention to motor inductance cripples it in the midrange. However, for your application, that might not be a draw back, and they do offer a PR on the same chassis frame, but it's really too small- you need two for each woofer to optimize the design.


          4x RSS210HF-4 in 130L with RSS265PR.

          Click image for larger version  Name:	RSS210HF 1W 130L perfectioniat SPL.png Views:	0 Size:	162.0 KB ID:	927563



          now, some thoughts about driver selection for a sealed or reflex enclosure of more conventional characteristics. This seems possibly closer to what you're looking for...


          Here's a table of some of the main 10" offerings at PE, with key characteristics and some comments based on PE"s claims. Some are advertised as designed for smaller enclosures. This is where the whole HO and HF designation comes in, though I think it's a weak descriptor choice- "High Output" is not actually higher output, compared with the HF parts, and "High(er) Fidelity" is not specifically achieved by the HF parts- HO parts have higher MMS and adjusted Cms to achieve an in box Fb that works better with smaller enclosures; unavoidably, this also lowers the sensitivity. The HF parts have lower MMS and need a larger enclosure for a similar Fb and operating cutoff. Hoffman's Iron Law again.


          10" Subwoofer drivers (partial listing) from PE


          Click image for larger version  Name:	Driver Table.png Views:	0 Size:	107.3 KB ID:	927564



          Note the check box column for whether this part is a reasonable choice for a sealed approach without significant EQ. Note also that I've bold faced a few specs.

          All of these drivers have Fs suitable for hitting the 30Hz range in box, or a bit lower with the right design approach. OTOH, 20Hz would be a stretch, needing EQ. ALSO, very important, with declining frequency, the Vd, volume displacement, must go up substantially for the same SPL output. The redline in the Unibox plot above highlights this- the upper limit for the driver direct radiation drops by about 12 dB for every octave lower- note 40Hz max level versus 20Hz max level. This is where the port or PR's come in. To match the output level of a good PR design at the bottom octave with just a sealed driver, you need two drivers instead of one.


          Comments driver by driver:
          • RSS265HO-4: This is a single voice coil 4 ohm nominal driver that I would likely term a 6 ohm driver, certainly easier to drive than many 4 ohm drivers. The MMS is in about the middle, but much higher than the HF part, so it will have a reasonable Fb in a smaller enclosure than the HF parts. Like the other 265HO and 265HF parts, the Xmax on the lower side for a subwoofer- this is in the category of drivers I prefer for the LF in three way systems, as it sort of straddles the characteristics between a woofer and a subwoofer, just like the Wavecor SW223 does. Note, with Qts this slow, it really needs to be in a reflex system; in a box small enough to push the Qtc up to 0.6 or so, Fb will be too high.
          • RSS265HF-4: 120g cone puts it in the range I like for a woofer for three way system; for a sub approach it will need a larger enclosure. Motor is a bit lower inductance and impedance.
          • RS265HO-44: The HO-44 is a dual voice coil part which can be wired either in parallel (car audio) or series (home HiFi). Cone mass is sort of Malcolm in the middle, so not really optimized for smaller enclosures, but marginally better than the HF part. Note highish Qts; this means it will have a good in a larger sealed box that still gives a reasonable Fb.
          • RSS265HE-22: Another part that seems more automotive oriented on the surface, but interesting with VC's in series for home environment; Qts is borderline for doing a sealed alignment without the Fb climbing too much, unless you want to use EQ. The higher Xmax and Vd means it can put out a fair amount of SPL in a sealed box, and the higher MMS means that box won't have to be too big... Note, 32lb! Brutally large and heavy for a 10" driver.
          • UM10-22: Similar to the 265HE-22, but not as much Xmax, and not as much bucks. And not as brutally heavy! Just 22 lb.
          • CSS-SDX10: An XBL2 design motor with linearized BL force, this driver has a rather low mass cone and will require a larger enclosure or substantial EQ. Though rated in the spec sheet as 4.3 ohm Re, its working impedance is more like a typical 8 ohm driver, so paralleling two is not out of the question- but it will not be a petite enclosure, due to driver design, and the need for larger enclosure for a given Fb. The low cone mass may be part of an effort to keep the sensitivity higher with an XBL2 motor. Xmax similar to UM10-22. Price is the highest of those in this table, though. Pair it up with some RSS265PRs, and there are some nice possibilities. But forget compact.



          BTW, be careful about folded port designs going around corners- that leads to turbulence and velocity related output compression.


          Hope this gives you a bit to think about, and if you can respond with more specifics about your needs/desires, I'm sure you can get more focused responses than this one!



          the AudioWorx
          Natalie P
          M8ta
          Modula Neo DCC
          Modula MT XE
          Modula Xtreme
          Isiris
          Wavecor Ardent

          SMJ
          Minerva Monitor
          Calliope
          Ardent D

          In Development...
          Isiris Mk II updates- in final test stage!
          Obi-Wan
          Saint-Saëns Symphonique/AKA SMJ-40
          Modula PWB
          Calliope CC Supreme
          Natalie P Ultra
          Natalie P Supreme
          Janus BP1 Sub


          Resistance is not futile, it is Volts divided by Amperes...
          Just ask Mr. Ohm....

          Comment


          • #6
            Thanks Jon, lots to digest and more than a handful of thoughts rolling about in my head right now. Will probably respond piecemeal with a few more questions to keep it manageable. That said, in response to your questions:
            • What is reasonably deep bass? F3 of 35Hz (+/- 3Hz) with usable bass in the 20s. Perhaps an F10 of 20-25 Hz?
            • What is adequate LF SPL at the listening position? Ideally it would mirror that capabilities of the Ardents. I seem to recall that may be around 110 dB? I would want the headroom such that max xmax is not needed to reach those capabilities. Perhaps an additional 3-6 dB over the reference mark.
            • How far is the listening position from where you will have speaker cabinets? Three meters currently, but let's plan for four.
            • What is a small foot print for you? My primary limitation is width - I'd like to keep the cabinet no wider than 14", possibly a little wider for feet or a baseplate of some kind. Depth is a 'little' more flexible, I think I could handle 18" in that regard, perhaps more. Height can be as much as five feet as far as I'm concerned. Let's not go crazy if we don't need to though! Keep in mind that while the footprint dimensions are what they are, going smaller is preferable unless the 'max' size gets me to a place (output, extension, distortion, etc) that I otherwise could not reach. I'm essentially imagining two boxes that will be positioned outside of and slightly behind the Ardents. I understand that is not necessarily (or even likely) the ideal placement for subwoofers, but such are the constraints of life. DSP is expected to be used in some fashion, though hopefully minimally.
            • What is a lot of power? I suppose this depends on the driver and what it can handle in a given alignment. In general, I think I would want an amplifier capable of at least 800 (real) watts RMS.
            • Are you familiar with Hoffman's Iron law, and why that completely supersedes notions about sealed versus reflex alignments? I'm very familiar with Hoffman and his law! However, I'm not sure I understand what you mean regarding superseding notions about sealed and vented enclosures?
            Originally posted by Steve Manning View Post
            Knowing Jon, I'm betting on the SDX12 and a PR or two ..... 😄
            Interestingly, the PRs designed for the SDX12 don't appear to have enough excursion to handle the sub (at least when using only a pair). This is based on the late Jeff Bagby's analysis on the CSS website itself. Of course, Dayton options do exist...

            Edit: Scratch that last statement. When used in an appropriately sized box (i.e. generally on the smaller side), they do have enough extension when used as a pair. They do look kinda goofy though!
            - Danny

            Comment


            • #7
              OK, working on my To-Do agenda for today, but while my Pizza for lunch is cooking I came up with a quick slightly tongue in cheek response, one that adhere's to the idea of "keeping it in the family, Starship Trooper version"!


              Two cabinets, each with 2x SW223BD02 and 1x RSS315PR, F3 of 28 Hz and Fb of 24 Hz. Wavecor's are back in stock at PE since about Christmas.

              Click image for larger version

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              the AudioWorx
              Natalie P
              M8ta
              Modula Neo DCC
              Modula MT XE
              Modula Xtreme
              Isiris
              Wavecor Ardent

              SMJ
              Minerva Monitor
              Calliope
              Ardent D

              In Development...
              Isiris Mk II updates- in final test stage!
              Obi-Wan
              Saint-Saëns Symphonique/AKA SMJ-40
              Modula PWB
              Calliope CC Supreme
              Natalie P Ultra
              Natalie P Supreme
              Janus BP1 Sub


              Resistance is not futile, it is Volts divided by Amperes...
              Just ask Mr. Ohm....

              Comment


              • #8
                Two PR's per cabinet and we're looking at an F3 of 26 Hz and better excursion headroom.
                the AudioWorx
                Natalie P
                M8ta
                Modula Neo DCC
                Modula MT XE
                Modula Xtreme
                Isiris
                Wavecor Ardent

                SMJ
                Minerva Monitor
                Calliope
                Ardent D

                In Development...
                Isiris Mk II updates- in final test stage!
                Obi-Wan
                Saint-Saëns Symphonique/AKA SMJ-40
                Modula PWB
                Calliope CC Supreme
                Natalie P Ultra
                Natalie P Supreme
                Janus BP1 Sub


                Resistance is not futile, it is Volts divided by Amperes...
                Just ask Mr. Ohm....

                Comment


                • #9
                  OTOH, you could take the 4x RSS210HF with 4x RSS265PR, split it into two 8 ohm cabinets, and get about the same thing for less money, but larger cabinets. in both cases targeting 110 db at a meter or two, with some headroom left.
                  the AudioWorx
                  Natalie P
                  M8ta
                  Modula Neo DCC
                  Modula MT XE
                  Modula Xtreme
                  Isiris
                  Wavecor Ardent

                  SMJ
                  Minerva Monitor
                  Calliope
                  Ardent D

                  In Development...
                  Isiris Mk II updates- in final test stage!
                  Obi-Wan
                  Saint-Saëns Symphonique/AKA SMJ-40
                  Modula PWB
                  Calliope CC Supreme
                  Natalie P Ultra
                  Natalie P Supreme
                  Janus BP1 Sub


                  Resistance is not futile, it is Volts divided by Amperes...
                  Just ask Mr. Ohm....

                  Comment


                  • #10
                    For the RSS210HF solution, imagine either this cabinet, or chopping it in two, two short modules. Recommend having two cabinets to deal with room modes more uniformly.



                    Click image for larger version

Name:	SMJ-40 Front ISO View.png
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Size:	5.06 MB
ID:	927571




                    the AudioWorx
                    Natalie P
                    M8ta
                    Modula Neo DCC
                    Modula MT XE
                    Modula Xtreme
                    Isiris
                    Wavecor Ardent

                    SMJ
                    Minerva Monitor
                    Calliope
                    Ardent D

                    In Development...
                    Isiris Mk II updates- in final test stage!
                    Obi-Wan
                    Saint-Saëns Symphonique/AKA SMJ-40
                    Modula PWB
                    Calliope CC Supreme
                    Natalie P Ultra
                    Natalie P Supreme
                    Janus BP1 Sub


                    Resistance is not futile, it is Volts divided by Amperes...
                    Just ask Mr. Ohm....

                    Comment


                    • #11
                      I like that you're focusing on narrow! What are the box sizes for these propositions?
                      - Danny

                      Comment


                      • #12
                        The picture above is for the 2nd 3D concept model for an SMJ-40 POC woofer section. This is the design with 4x RSS210HF-4 and 4x RSS265PR in total per side, per cabinet. The cabinet is 12" wide, 40" tall, and 25-1/2" deep. For your application I would suggest splitting it in two, making it about 22" tall, and same depth and width, though height and depth could be adjusted as long as you retain about 65-70L NET for interior volume. With two LF sources you should have less problems with room modes.

                        Here, the intention is a short array, for good vertical pattern up through the midrange, and PR's towards the back near a wall pressure boundary. The woofers could be spaced further apart for a sub only configuration. An overall height of 24" might be good for two woofers and two PR'd, then the front to back depth could be reduced to about 20".
                        the AudioWorx
                        Natalie P
                        M8ta
                        Modula Neo DCC
                        Modula MT XE
                        Modula Xtreme
                        Isiris
                        Wavecor Ardent

                        SMJ
                        Minerva Monitor
                        Calliope
                        Ardent D

                        In Development...
                        Isiris Mk II updates- in final test stage!
                        Obi-Wan
                        Saint-Saëns Symphonique/AKA SMJ-40
                        Modula PWB
                        Calliope CC Supreme
                        Natalie P Ultra
                        Natalie P Supreme
                        Janus BP1 Sub


                        Resistance is not futile, it is Volts divided by Amperes...
                        Just ask Mr. Ohm....

                        Comment


                        • #13
                          But Jon, in a 12" wide cabinet I could fit 10" subwoofers. Perhaps I'll play around with scaling this model up by one size.😁

                          FYI, there is a fellow asking about your Daisy-Rey speakers in another thread...
                          - Danny

                          Comment


                          • #14
                            Originally posted by Steve Manning View Post
                            Knowing Jon, I'm betting on the SDX12 and a PR or two ..... 😄
                            Steve, this comment is killing me. Honestly all I can think about now is cramming the SDX12 into a small box with a pair of passive radiators. My cart at the CSS website is making my wallet nervous with anticipation. My first glance was on mobile so I didn't think the application would work, but second glance in a browser proves it to more than exceed my needs.

                            The SDX10 is another, perhaps more cost effective, possibility, but still seems to want a box around the same size and extension is reduced a few Hz.
                            - Danny

                            Comment


                            • #15
                              I'd run the numbers before going with two of the CSS PR's, for the volume and mass alignment you need.

                              An overlooked point for many PR's and PR designs I've seen is the working range and linearity of the passive radiator. Variation in Cms with excursion changes the actual tuning and amplitude from what a straightforward calculation indicates, and this means unexpected amplitude related nonlinearity at low frequencies, aka "Distortion".

                              A few manufacturers really work hard at addressing that with PR products- note, for example, the Seas SL26R. This is the updated version.


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                              You may note that the surround is a taller half round more like a UM series Dayton sub (and unlike Scanspeak or SB or CSS PR's) and fairly wide for this size PR; they also went to some lengths to ensure spider suspension linearity over the travel limit, and had to withdraw some lots of the earlier product due to QA failures on this factor. This part was designed to work with the Seas Extreme L26ROY woofer.



                              It does not come with weight kits for adjustment of tuning parameters; it's a one trick pony, to be paired with the L26ROY in a specific design. Of course, with a little effort, that issue can be solved. However, I'm not recommending you consider the SL26R, just pointing out an example of a company that has a serious design execution for this kind of component. It's my favorite execution 10" PR, followed closely by the RSS265PR.

                              For most PR's I've seen, I'd recommend using no more than 1/2 of the Xmech rating. For the Dayton RSS series, I'd extend that to 2/3, as they seem to have a well executed surround and spider compared to most. Note also that the CSS PR comes with a base mass of about 100g, with a max loading of 1200G. That's a lot, and as it turns out, you may need much of that.


                              Now, some details...

                              With some serious juice, you can get some serious SPL out of this subwoofer and 2 PR's.

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                              But, how does the excursion look for this configuration?




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                              Well, you can see that at this level of output, though the drier is within bounds, the PR has not only exceeded my preferred guidelines for excursion but also exceeded the mechanical limits. Not nice! Now, mind you, this is at the upper performance boundary, and it's likely that you may never be inclined to push it this far or this low. And of course, there is a solution... Three PR's, with more mass in the tuning.



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                              For the same NET enclosure volume (which means larger gross volume) we can hit the 2/3 Xmech limit, and most of the time you'll be operating under my preferred 50% of Xmech rating for relatively "conventional" construction PR's.

                              Note, you can achieve similar performance with a vented enclosure, but you will need a 6" ID port 60" long, (5ft stovepipe anyone?) and the first port resonance will be at about 120Hz, so you'll need to keep the crossover point well away from that frequency. This reminds me of a design I did for the Stryke HE15 subwoofer (long time HTGuide members may remember) in 100L, with a 6" ID port in SBB4 alignment. Due to the larger 100L enclosure the port "only" had to be 100 cm long (~40"). This enclosure was narrow, relatively short (tall enough for the 15" driver and the port below it) and quite deep. Using a planar port load this length could probably be reduced, but it would take some experimentation.





                              DFAL
                              Dark Force Acoustic Labs

                              A wholly owned subsidiary of Palpatine Heavy Industries

                              Comment


                              • #16
                                Now, as possibly interesting comparison, just to annoy and provoke thought, this is what a slightly more LF optimized version of the SMJ-40 bass module can deliver... with 200W, not 800W. Split into two cabinets, this may provide more uniform results in consideration of LF room modes. And this doesn't take into account boundary mode lift at the lower frequencies.


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                                DFAL
                                Dark Force Acoustic Labs

                                A wholly owned subsidiary of Palpatine Heavy Industries

                                Comment


                                • #17
                                  Question for you (or anyone familiar with Unibox): how do you handle multiple voice coils? It doesn't appear to be an option anywhere? Or are we not overly concerned about that, since it won't change the shape of anything, just the 'height' of the curves?

                                  I'm trying the SDX12, SDX10, and dual SDX10s with various Dayton Audio passive radiators but want to be certain I'm doing it correctly. I've also noted the RSS315HO produces very similar curves to the SDX12 (at least in WinISD for ported and sealed), so I'm playing around with that and the RSS265HO with PRs as a perhaps more cost effective alternative.

                                  I think all I can rule out right now is the Wavecor idea - they're just too expensive for what they are.


                                  I'm not opposed to passive radiators but I definitely want to make sure the model is well reviewed before going in that direction.

                                  I'm not sure I'm sold on using 8" subwoofers. The model looks nice, but I have a friend somewhere who might kick me if he finds out.
                                  - Danny

                                  Comment


                                  • #18
                                    The driver T/S parameters will be given for a specific VC wiring configuration- usually that is wired in series, but check based on the specified Re. Normally, dual 2 ohm or dual 4 ohm configuration is will have T/S parameters specified for serious connection.

                                    Note that RSS315PR are back ordered until early March.
                                    DFAL
                                    Dark Force Acoustic Labs

                                    A wholly owned subsidiary of Palpatine Heavy Industries

                                    Comment


                                    • #19
                                      That is a fair point, but I am in no huge hurry at the moment. I may also have a dozen already in storage...unless those were the RSS265-PR.
                                      - Danny

                                      Comment


                                      • #20
                                        So it's quite possible I'm deviating from the original intent of these 'music'-based subwoofers, but I'm having fun and doing silly things, so what the heck. Bigger is better, right? Well, it's loud at least! In a ~30" tall, 14" wide, 24" deep cabinet, something approximating 120L when crammed absolutely full...

                                        Edit: Man I cannot get the in-line image link to work, it always copies the photos as attachments as well. Wonder if it's because they're gifs?
                                        Attached Files
                                        - Danny

                                        Comment


                                        • #21
                                          One of the problems I was running into modeling 10" and 12" Dayton Audio subwoofers with passive radiators was driver excursion. Especially on the 10" models, they'd simply unload in the mid 20 Hz range. This is probably a given for many small subwoofers, and realistically my use case shouldn't have much (if any) material in that range, but it still bothered me. Enter the RSS315HE-22 and the RSS265HE-22. I couldn't get the latter to model well with passive radiators, but the former seemed pretty happy with several different arrangements. Something similar to the last post is shown here, with a bit lower extension and similar output (if it could handle the power the SDX12 can). No issues with driver excursion either, which is nice. PR excursion is a bit higher than Jon recommends, however that only happens in the 20-25Hz range at 500 watts per driver - I think I can live with that.

                                          There is a typo in these graphs - that is a pair of RSS390-PR (15") passive radiators instead of the RSS315-PR (12").

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                                          - Danny

                                          Comment


                                          • #22
                                            Note: Using a driver well below its free air Fs is tricky, though in some cases possible, depending on the T/S parameters. Note the extension in the RSS210HF design.

                                            But you cannot expect good driver loading below the Fb, as this is the tuning frequency that results in the enclosure with the PR and mass loading you've chosen. If you want to go lower, the Fb must be lower. There are tradeoffs with regards to the ratio of F3 and Fb, but a more conservative design shoots for a Fb below the F3 target, unless that F3/Fb combination is sufficiently low for the target. Most of the time with music sources, 30Hz is sufficient; for occasional recordings, 25 or less will be desired. For HT, 10Hz is a good working target, which is more challenging of course, and why large diameter drivers sealed with EQ often seem to be a more practical approach, because the demands of HFE are different from music, and it's assumed that the drivers won't be doing above 100hz.
                                            the AudioWorx
                                            Natalie P
                                            M8ta
                                            Modula Neo DCC
                                            Modula MT XE
                                            Modula Xtreme
                                            Isiris
                                            Wavecor Ardent

                                            SMJ
                                            Minerva Monitor
                                            Calliope
                                            Ardent D

                                            In Development...
                                            Isiris Mk II updates- in final test stage!
                                            Obi-Wan
                                            Saint-Saëns Symphonique/AKA SMJ-40
                                            Modula PWB
                                            Calliope CC Supreme
                                            Natalie P Ultra
                                            Natalie P Supreme
                                            Janus BP1 Sub


                                            Resistance is not futile, it is Volts divided by Amperes...
                                            Just ask Mr. Ohm....

                                            Comment


                                            • #23
                                              Thanks Jon, good stuff. I did note your RSS210HF design and was curious how it could extend so low compared to many of the subs I've been modeling, despite being so small in stature. In some cases, at least in the SDX12/RSS460PR combination, extension is limited because there just aren't enough weights for lower tuning. Even still though, it wouldn't be near flat down to 20 Hz, more like 25.

                                              I decided to bite the bullet and order a pair of Hypex FA502 plate amps, so I'm set for powering a pair of subs - either two individual powerful subs (like the SDX12) or two boxes each with a pair of less powerful subs (like the RS line or the SDX10). Now it's just figuring out what is best to pair with them. I chose these over some of the Dayton products for three reasons, 1) I already have a Hypex-based amplifier for the Ardents, which I like a lot, and 2) I trust the power rating of these amps much more than I do the Dayton offerings and 3) it has DSP built in. I briefly looked into the USA-made Speakerpower brand as well but it just seemed expensive for what it was. Good way to get lots of electrons flowing though, if your application requires it.

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                                              - Danny

                                              Comment


                                              • #24
                                                One of the difficulties I've encountered with a few of these models is actually building the thing. As with some subs requiring excessively long ports, sometimes things just don't fit well. Since I have elected to go with a plate amplifier (as opposed to a pro amplifier) I have effectively reduced the real estate on both the back and the sides of a given box in which a passive radiator could be placed. One solution to this is shown below - this would be for two SDX12s and four APR12 passive radiators. An imposing 55" tall, perhaps one should rethink the use of ports instead - especially considering the $100 per PR price of this particular arrangement.

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                                                Last edited by technodanvan; 12 January 2023, 11:14 Thursday.
                                                - Danny

                                                Comment


                                                • #25
                                                  Originally posted by technodanvan View Post
                                                  One of the difficulties I've encountered with a few of these models is actually building the thing. As with some subs requiring excessively long ports, sometimes things just don't fit well. Since I have elected to go with a plate amplifier (as opposed to a pro amplifier) I have effectively reduced the real estate on both the back and the sides of a given box in which a passive radiator could be placed. One solution to this is shown below - this would be for two SDX12s and four APR12 passive radiators. An imposing 55" tall, perhaps one should rethink the use of ports instead - especially considering the $100 per PR price of this particular arrangement.

                                                  Click image for larger version Name:	Ardent subs.png Views:	0 Size:	276.5 KB ID:	927788
                                                  You could always look at side mounting the PR's .... could reduce the overall height a fair bit.
                                                  Hold on to your butts - It's about to get Musical!



                                                  WEBSITE: http://www.smjaudio.com/

                                                  Comment


                                                  • #26
                                                    That is a consideration as we're probably talking 8-10 inches here, however I felt this first attempt would be more aesthetically pleasing. An alternative, only using one subwoofer and two passive radiators, would work in a similar fashion.

                                                    Edit: I was thinking on this last night and neglected to mention the volume. As shown, and including reasonable assumptions for the volume of the drivers and PRs, this cabinet would be about 100L. Technically a little on the small side for what I was shooting for, I think increasing the depth 1-2 inches plus making the mini-cab for the amp smaller would get me where it should be (closer to 120L).
                                                    Last edited by technodanvan; 12 January 2023, 11:16 Thursday.
                                                    - Danny

                                                    Comment


                                                    • #27
                                                      After booting up the Way Back machine (for those old enough to remember the cartoon) I pulled the modeling I did 6-7 years ago when I built my SDX10 sub. Jon also verified the numbers at the time. I used a pair of Scan Speak 26W/0-00 PRs mounted on the sides. The Dayton PRs didn't exist back then or I would have likely used them. I only use the Sub for music and in my listening room it does a nice job. The F3 was 26hz from a 46L enclosure. The enclosure is fairly petite and a pair would not dominate the room. I use a 500watt Oaudio plate amp no longer available and it energizes the room pretty well. If I was doing it over I would build a second sub which might be over-kill. Playing James Taylors Hourglass digital file on the cut Gaia pictures on the wall will dance if the volume gets a little too high. I attached the modeling file from 2015. I think the T/S parameters for the sub might have changed a little bit over time but it's a great subwoofer.
                                                      Chris

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                                                      Comment


                                                      • #28
                                                        Hey thanks! That is very helpful - very useful to have some anecdotal experience with these products since I have none - including no subwoofer for over a decade!

                                                        This 'may' help keep me grounded in reality a bit too. Maybe.

                                                        I still like my tall sub idea, but maybe at that point exploring a sonotube would be prudent.
                                                        - Danny

                                                        Comment


                                                        • #29
                                                          By the way Steve Manning, ​I may be interested in a little help on these in the form of some bamboo baseplates that match the ones you made for my Ardents. I'd do them myself, but I don't really want to buy a whole sheet of bamboo just for that.
                                                          - Danny

                                                          Comment


                                                          • #30
                                                            So, going back to JonMarsh's comment earlier in this thread, here is a box supporting a single SDX12 and 3x APR12 passive radiators. At 46" tall, it would still end up taller than my Ardents, though only by a few inches. Volume for this one would be around 78L, larger than required per Jon's model (70L). That would probably be balanced out if I modeled some bracing. This box is 1.5" all around, except for a 3" baffle. Inner 3/4" would be MDF, the rest Baltic Birch. Overkill? Perhaps, but I like my boxes solid.

                                                            I think this is approaching what I may actually do.

                                                            Note that the previous drawing had two passive radiators per sub, where this one has three. In the previous model each sub could only get ~500 watts, which meant the APR12 had enough Xmech for the full range of power. In the below scenario the single SDX12 could get ~1,000 watts, meaning an additional passive radiator was necessary.

                                                            One thing I don't much like about this model is the location of the driver itself (front bottom). Given it weighs nearly 50 pounds it may make more sense to locate closer to the bottom of the box to lower the center of gravity, however I was unsure if having the amp compartment so close to it would interfere with its operation.


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                                                            Last edited by technodanvan; 12 January 2023, 16:27 Thursday.
                                                            - Danny

                                                            Comment


                                                            • #31
                                                              I have settled on the SDX12/3x APR12 combination for my project. It exceeds my extension requirement handily while meeting my footprint needs. With a pair of them, output could be as high as 114dB +/- 3dB all the way to 20 Hz. Cost is a little high, both for the subs themselves and for the six passive radiators, but I should end up with two very capable subwoofers that could be used for both music and movies. Since I don't know what I'll be doing 10 years from now, I think that versatility is important.

                                                              Now comes the fun part - making them! Proposed design is below. The intent will be to place this box on a baseplate to match my Ardents (shown below). I considered trying to make the baffle the same as well (out of thick bamboo ply) but I don't think that expense is worth it. They should look just as good if they're white, though I may try to integrate small bits of bamboo and purpleheart here and there. Perhaps just a baffle 'cover' that hides the mounting screws for the driver/prs? We'll see.



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                                                              This latest model includes a ~3" baffle (2x 3/4 MDF inner, 2x 18mm baltic birch outer) and ~1.25" sides (1x 1/2" MDF inner, 1x 18mm baltic birch outer). Window bracing is either 18mm baltic birch or 3/4" MDF, whichever I have more scrap of - probably the MDF. Subwoofer driver placed at the bottom for overall stability. Fusion360 seems to think the box will weigh around 80 pounds as shown (without the top and side modeled). I think that all told, they'll approach 200 once complete. Good thing I've been going back to the gym of late...

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                                                              Last edited by technodanvan; 13 January 2023, 17:51 Friday. Reason: Added image
                                                              - Danny

                                                              Comment


                                                              • #32
                                                                I'm a CAD novice and I've been playing around in Fusion360 a little today. Seems pretty powerful, especially if I had developed this model as individual parts. Alas, I did not. Still though, this will certainly help when I'm in the garage making sawdust. I'm not sure why it isn't showing fractions here - the ID and OD are 10 7/8" and 12 9/32", respectively.

                                                                Edit: Parts have been ordered. Just need to get a couple sheets of MDF delivered...maybe some more baltic birch too, though I should have enough in my garage already.


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                                                                - Danny

                                                                Comment


                                                                • #33
                                                                  Are you gonna take a stab at spraying these cabinets white or whats the plan for finishing?
                                                                  Painter in training

                                                                  Comment


                                                                  • #34
                                                                    That's a secret!

                                                                    No not really...My plan for finishing is to find someone in town that can do fiberglass work, wrap them in 2-3 layers, then have them professionally painted. I really liked how that turned out on my Eros some 15 years ago and they look just as good as the day I picked them up from the shop. The downside of doing this is they probably won't match the more 'matte' finish I have on the Ardents.

                                                                    Taking the 'Y' out of DIY has some drawbacks (mostly cost) but with drooly dogs I want a durable finish that I don't have to worry about.
                                                                    - Danny

                                                                    Comment


                                                                    • #35
                                                                      Originally posted by technodanvan View Post
                                                                      That's a secret!

                                                                      No not really...My plan for finishing is to find someone in town that can do fiberglass work, wrap them in 2-3 layers, then have them professionally painted. I really liked how that turned out on my Eros some 15 years ago and they look just as good as the day I picked them up from the shop. The downside of doing this is they probably won't match the more 'matte' finish I have on the Ardents.

                                                                      Taking the 'Y' out of DIY has some drawbacks (mostly cost) but with drooly dogs I want a durable finish that I don't have to worry about.
                                                                      You had them wrapped vs putting an epoxy over all the wood and then sanding? Interesting! So many options to choose for finishing. The fiberglass will give a very nice finish. I would think they could use a matte clear coat for protection so it would not be glossy. I like the design of the cabinet and really looking forward to seeing the final painted cabinet.
                                                                      Painter in training

                                                                      Comment


                                                                      • #36
                                                                        Yup, seemed like a good idea at the time. Bonus - it helps further stiffen the cabinet a little!

                                                                        I'll reach out to some local companies once the boxes are underway to see what options exist for colors and finishes.
                                                                        - Danny

                                                                        Comment


                                                                        • #37
                                                                          Originally posted by technodanvan View Post
                                                                          Yup, seemed like a good idea at the time. Bonus - it helps further stiffen the cabinet a little!

                                                                          I'll reach out to some local companies once the boxes are underway to see what options exist for colors and finishes.
                                                                          FYI Danny, the finish on your Ardent's is satin.
                                                                          Hold on to your butts - It's about to get Musical!



                                                                          WEBSITE: http://www.smjaudio.com/

                                                                          Comment


                                                                          • #38
                                                                            Good to know Steve, thanks!
                                                                            - Danny

                                                                            Comment


                                                                            • #39
                                                                              One thing I've been thinking about is the weight of the passive radiators - the moving mass will be around one kilogram. Now, two of the passive radiators will offset each other since they move opposite directions at the same height in the cabinet, but the third has no such balancing mass (well the subwoofer driver would technically do this, but its mass is much lower, and it's lower in the cab). I'm not terribly worried about this given the expected weight of the finished cabinets, but should I be concerned about a 1 kg mass moving 2 feet off the base? That just seems like a lot, and could maybe cause a 'rocking' motion if the cabinet isn't heavy enough with feet spaced appropriately.

                                                                              Just curious if anyone has encountered this before, or if I'm overthinking it.

                                                                              CSS products are expected Thursday. Will update with photos then....I'm curious to compare the physical size of the SDX12 vs the UM15-22. Hypex amps are here now, I may unpack those Thursday for a photo session too. Waiting til tomorrow to order a few extra odds and ends from Madisound, some of which are for this project. I'll order the MDF tomorrow as well.

                                                                              Still want to source some binding posts...preferably 5-way plugs on BOTH ends. I don't know if anyone makes such a thing, but my searches have not been fruitful. Might just have to make something else work since it really isn't a big deal given the hidden nature of my application. Other than brass inserts (which I'll wait to order) I should pretty much be set by this weekend, I think - just need to get another large project out of my garage before I begin.

                                                                              Oh, what sort of glue are people using these days? I usually stick to Titebond II or III (which I'm sure I'll use for gluing faces together) but would there be something more appropriate for the inner skeleton? Gorilla glue, or something else that penetrates well?
                                                                              - Danny

                                                                              Comment


                                                                              • #40
                                                                                Is a 15 component bracing system a little too complex? Probably...but it's where we're at and gets the volume I need. Note several pieces at the top and bottom are solid - they're blanks creating voids in the speaker cabinet. It was either this or shorten the cabinet to get the correct volume, and I liked the outer dimensions as they were. I mean they look nice on a computer, hopefully they look good once manufactured. That said, while Fusion 360 does calculate volumes for me it can only do it with the data I have, and what I don't have is accurate data for the subwoofer driver and passive radiators. On the CSS website Jeff Bagby says to use 0.2 ft3 for the driver itself, so I used that and 0.1 ft3 for the PRs for lack of anything better. That (supposedly) gets me within 5L of the target volume.


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                                                                                - Danny

                                                                                Comment


                                                                                • #41
                                                                                  New stuff day!

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                                                                                  - Danny

                                                                                  Comment


                                                                                  • #42
                                                                                    The passive radiators deserve their own post, because there was a slight issue...

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                                                                                    The bay for the weights more or less looked like what I expected it to, though I hadn't seen any photos previously.

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                                                                                    The weights fell out when I picked up the box, but it seems everything is there.

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                                                                                    Since the little box fell apart, I decided to just load them in the PR for the time being. My application requires most of them anyway. You might see the problem here...that little bay is awfully full.

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                                                                                    Wait, I don't remember this gap being there previously...

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                                                                                    It was as I more or less suspected, the cap was hitting the wingnut. You can see the plastic has been gouged out a bit. This shouldn't be an issue for me since I "shouldn't" need to use all the weights, but it's probably worth noting if a designer thought they could cram a few more in there. Also of note, you can't add any weights to the back - the bolt head is inset in the plastic. You could probably pop it out with some effort and install a longer bolt, but that would be a headache and who knows if the PR would be happy with it.

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                                                                                    - Danny

                                                                                    Comment


                                                                                    • #43
                                                                                      Good pictures! I'd probably just grind down the wingnut a tad, or find a lower-profile nut.

                                                                                      Comment


                                                                                      • #44
                                                                                        Yeah, solutions definitely exist so I don't think it's a big deal.

                                                                                        Based on how the frames look on the sub and the PRs I think I'll definitely want to make some sort of beauty ring if they're to look as good as the Ardents.
                                                                                        - Danny

                                                                                        Comment


                                                                                        • #45
                                                                                          Let's see if this upload works... I remodeled the box making each individual part a 'component' in Fusion360, which enabled me to generate a part list and individual diagrams. I didn't really follow any conventions when adding dimensions to the diagrams so they're kind of all over the place, but you might notice some of them are pretty nice. Note there are no individual diagrams for the pieces made of baltic birch since I shouldn't need them - they're all simply rectangles that are adhered to the inner MDF box, so I'll probably just use actual measurements and cut just a little too large. They're shown on the parts list anyway, just in case.

                                                                                          Edit: I should also point out there are some very minor errors in this document, but none that are critical (that I'm aware of). I'll be using a printout to (hopefully) make some sawdust this weekend so if there are any major errors I can fix them.
                                                                                          Attached Files
                                                                                          - Danny

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