Ultra-compact dipoles

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  • gainphile
    Senior Member
    • Apr 2009
    • 107

    Ultra-compact dipoles

    I'm keen to find out how small a pair of open baffle speakers can be built.

    The full plan can be read here , but in summary the criteria are:
    - Full range (20hz - 20khz)
    - Compact, no larger than typical 5" floorstander. High WAF :P
    - Simple eq/xo, no more than bi-amp.
    Click image for larger version

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    The XO/EQ will be hybrid. Woofer and Tweeters are Zaph ZA5.2 kit, and the subs will use any reasonable 10" drivers.
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    Still not decided whether the subs will be force-cancelling (push-pull) like above or a simpler construction.
    Last edited by theSven; 03 May 2023, 21:43 Wednesday. Reason: Update image location
    gainphile.blogspot.com
  • gainphile
    Senior Member
    • Apr 2009
    • 107

    #2
    ... Most importantly the drivers/kit just arrived today!

    Individually measured Zaph ZA14 :T

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    Vifa DQ25

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    Passive ZA5.2 crossovers

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    Last edited by theSven; 03 May 2023, 21:44 Wednesday. Reason: Update image location
    gainphile.blogspot.com

    Comment

    • 5th element
      Supreme Being Moderator
      • Sep 2009
      • 1671

      #3
      Interesting approach it's going to be interesting to see how this pans out.

      I do think that opposing woofers would be a good idea if possible. What woofers do you have in mind?

      Edit - I see, the jaycars.
      What you screamin' for, every five minutes there's a bomb or something. I'm leavin' Bzzzzzzz!
      5th Element, otherwise known as Matt.
      Now with website. www.5een.co.uk Still under construction.

      Comment

      • jheizer
        Junior Member
        • Jul 2010
        • 23

        #4
        Semi OT, but I see serial number 074 on the woofer. Have there really been that few sold? I just happen to have ordered the MTM in wall kit this morning for my workout room. Curious now what the serial numbers on them will be. I would have thought the kits would have been more popular with the first time DIYers

        Good luck with the built.

        Comment

        • Face
          Senior Member
          • Mar 2007
          • 995

          #5
          You can probably add a zero to that number, if not two.
          SEOS 12/AE TD10M Front Stage in Progress

          Comment

          • JonMarsh
            Mad Max Moderator
            • Aug 2000
            • 15259

            #6
            Well, looks like good clean fun! Have you tried running numbers for extension and SPL for the drivers in SL's old spreadsheet? (good tool to get a handle on usable extension and SPL).
            the AudioWorx
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            Comment

            • gainphile
              Senior Member
              • Apr 2009
              • 107

              #7
              Originally posted by 5th element
              Interesting approach it's going to be interesting to see how this pans out.

              I do think that opposing woofers would be a good idea if possible. What woofers do you have in mind?

              Edit - I see, the jaycars.
              Yes, they are locally available woofers here, and I already have 4 of them.

              The Dayton Audio SD270A-88 10" DVC Subwoofer would make a great low-cost choice with Fs of 26hz and Qts 0.43. But shipping cost is prohibitive to Australia!

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              Last edited by theSven; 03 May 2023, 21:45 Wednesday. Reason: Update url to PE
              gainphile.blogspot.com

              Comment

              • gainphile
                Senior Member
                • Apr 2009
                • 107

                #8
                Originally posted by jheizer
                Semi OT, but I see serial number 074 on the woofer. Have there really been that few sold? I just happen to have ordered the MTM in wall kit this morning for my workout room. Curious now what the serial numbers on them will be. I would have thought the kits would have been more popular with the first time DIYers

                Good luck with the built.
                They actually did not come from Madisound. Zaph sent them as part of the design contest. I think he receives samples for every batch produced, so these could be some of them.
                gainphile.blogspot.com

                Comment

                • gainphile
                  Senior Member
                  • Apr 2009
                  • 107

                  #9
                  Originally posted by JonMarsh
                  Well, looks like good clean fun! Have you tried running numbers for extension and SPL for the drivers in SL's old spreadsheet? (good tool to get a handle on usable extension and SPL).
                  Yes. Here I compare with W22 on wider baffle.

                  I had been targeting 250-300hz, and 280hz seems to be the best compromise when the subs' quarterwave resonance is accounted for.

                  At 280hz, a single ZA14 on 23cm baffle can produce 102dB. Add +6dB to account the LR4 crossover and +6db for stereo, then we arrive at 124dB.

                  These are great (although optimistic) numbers and allow for some adjustment like lowering the xo frequency.

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                  The dipole subs will dictate the overall SPL though. And it would be much lower than the woofer.
                  Last edited by theSven; 03 May 2023, 21:45 Wednesday. Reason: Update image location
                  gainphile.blogspot.com

                  Comment

                  • AJINFLA
                    Senior Member
                    • Mar 2005
                    • 680

                    #10
                    Originally posted by gainphile
                    At 280hz, a single ZA14 on 23cm baffle can produce 102dB. Add +6dB to account the LR4 crossover and +6db for stereo, then we arrive at 124dB.
                    That's either pub/fishing math or you meant 114db.

                    cheers,

                    AJ
                    Manufacturer

                    Comment

                    • gainphile
                      Senior Member
                      • Apr 2009
                      • 107

                      #11
                      lol yes 114 :lol:
                      gainphile.blogspot.com

                      Comment

                      • gainphile
                        Senior Member
                        • Apr 2009
                        • 107

                        #12
                        Rear opening of the ZA14. Just begs to be driven as OB :T

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                        Last edited by theSven; 03 May 2023, 21:45 Wednesday. Reason: Update image location
                        gainphile.blogspot.com

                        Comment

                        • its_bacon12
                          Member
                          • May 2008
                          • 73

                          #13
                          Been looking forward to someone tackling this concept. I have not the wherewithal nor the time to do it myself

                          Comment

                          • Maldur
                            Junior Member
                            • Dec 2010
                            • 4

                            #14
                            What about different directivity of bass and midrange/treble range?

                            Comment

                            • 5th element
                              Supreme Being Moderator
                              • Sep 2009
                              • 1671

                              #15
                              Originally posted by gainphile
                              Yes, they are locally available woofers here, and I already have 4 of them.

                              The Dayton Audio SD270A-88 10" DVC Subwoofer would make a great low-cost choice with Fs of 26hz and Qts 0.43. But shipping cost is prohibitive to Australia!
                              It always pains me when I see all the fantastic deals on offer in the states, from both Mad and then PE. Why can't we ave something like that over here!

                              Those ZA14s do look mighty nice, I think your photos of them are the best I've seen from an aesthetic point of view. I guess I'll have to win a contest to get me a pair :-)
                              What you screamin' for, every five minutes there's a bomb or something. I'm leavin' Bzzzzzzz!
                              5th Element, otherwise known as Matt.
                              Now with website. www.5een.co.uk Still under construction.

                              Comment

                              • gainphile
                                Senior Member
                                • Apr 2009
                                • 107

                                #16
                                Originally posted by its_bacon12
                                Been looking forward to someone tackling this concept. I have not the wherewithal nor the time to do it myself
                                Well TIME and WEATHER is currently my biggest hurdle to do anything at the moment :lol:. And last night I think i broke my microphone .

                                Anyway, I'm off to camping this weekend so nothing will happen till next week, hopefully with better temperature too!
                                gainphile.blogspot.com

                                Comment

                                • gainphile
                                  Senior Member
                                  • Apr 2009
                                  • 107

                                  #17
                                  Originally posted by Maldur
                                  What about different directivity of bass and midrange/treble range?
                                  Bass and Midrange would have the same directivity as dipoles up to about 2k or higher, so no problems there. The 'issue' is with creating dipole response at higher frequencies with dome tweeters.

                                  I've built dipoles with single forward tweeters and quite fine with them. The higher the xo frequency, the better.
                                  gainphile.blogspot.com

                                  Comment

                                  • sfdoddsy
                                    Senior Member
                                    • Sep 2000
                                    • 496

                                    #18
                                    I think he meant about the bass nulls. From the look of the plan you'd be listening to the bass section at 90 degrees, ie where the nulls are.
                                    Steve's OB Journey

                                    Comment

                                    • gainphile
                                      Senior Member
                                      • Apr 2009
                                      • 107

                                      #19
                                      The dipole would be still front-back oriented (the air is pushed to the front and back).

                                      Very much like a "w-frame" woofer in Orion 4 or Phoenix.
                                      gainphile.blogspot.com

                                      Comment

                                      • gainphile
                                        Senior Member
                                        • Apr 2009
                                        • 107

                                        #20
                                        Originally posted by 5th element
                                        Those ZA14s do look mighty nice, I think your photos of them are the best I've seen from an aesthetic point of view. I guess I'll have to win a contest to get me a pair :-)
                                        They are beautiful drivers:
                                        - Very open rear (even the magnet part)
                                        - Rigid metal
                                        - even has gasket!

                                        Some photos on the web shows the cone as shiny (like jordan). But that's not the case as shown when taken from an angle. The phase plug is very nice and finely polished like mirror.
                                        gainphile.blogspot.com

                                        Comment

                                        • jheizer
                                          Junior Member
                                          • Jul 2010
                                          • 23

                                          #21
                                          I got mine today and I have to agree. They are real nice looking and well built.

                                          Comment

                                          • Juhazi
                                            Senior Member
                                            • May 2008
                                            • 239

                                            #22
                                            about dipole highs - I think you should try a rear firing tweeter, perhaps in 45deg. upwards. I'm quite sure that the quality of the element is not important, it just makes reflections from the back wall. The level of the rear tweet should be adjustable because rooms and placement vary so much. But then it's not so cheap and simple...

                                            About the bass - I just saw Nelson Pass's slot construction. How about opposing elements firing in a slot. Pass has long wings but I wonder how it would work without such - here

                                            I'm only dreaming of dipoles. Your concept is attractive!
                                            My DIY speaker history: -74 Philips 3-way, -82 Hifi 85B, -07 Zaph L18, -08 Hifitalo AW-7, CSS125FR, -09 MarkK ER18DXT, -13 PPSL470Dayton, -13 AINOgradient, -18 Avalanche AS-1 dsp, -18 MR183w

                                            Comment

                                            • cjd
                                              Ultra Senior Member
                                              • Dec 2004
                                              • 5568

                                              #23
                                              Mmmm. More info on slot loading. I think my lower end will be 24x24x54. Inches. Per channel. I don't have room for this.

                                              A compact dipole seems so much smarter.
                                              diVine Sound - my DIY speaker designs at diVine Audio

                                              Comment

                                              • Maldur
                                                Junior Member
                                                • Dec 2010
                                                • 4

                                                #24
                                                Originally posted by sfdoddsy
                                                I think he meant about the bass nulls. From the look of the plan you'd be listening to the bass section at 90 degrees, ie where the nulls are.
                                                Exatly.
                                                Otherwise very nice project, btw.

                                                Comment

                                                • Jonasz
                                                  Senior Member
                                                  • Nov 2004
                                                  • 852

                                                  #25
                                                  No the nulls are to the sides, not front and back. The drivers will push the air through the slots frint and back, like a w-baffle.

                                                  Comment

                                                  • Maldur
                                                    Junior Member
                                                    • Dec 2010
                                                    • 4

                                                    #26
                                                    Originally posted by Jonasz
                                                    The drivers will push the air through the slots frint and back, like a w-baffle.
                                                    Hmm, ok, my mistake.

                                                    Maybe four 8" instead two 10" and same (ordinary) direction as midrange produces less cavity coloration?

                                                    Comment

                                                    • cjd
                                                      Ultra Senior Member
                                                      • Dec 2004
                                                      • 5568

                                                      #27
                                                      Cavity issues are only a problem if you try to cross above the point where they exist; You also won't avoid cavity issues since it would have to be U or H baffle to keep the low frequency response vaguely similar.

                                                      If I were moving to 8" drivers, I'd simply do a stack of W baffles. You lose horizontal placement of the drivers that way, though.

                                                      C
                                                      diVine Sound - my DIY speaker designs at diVine Audio

                                                      Comment

                                                      • gainphile
                                                        Senior Member
                                                        • Apr 2009
                                                        • 107

                                                        #28
                                                        Some progress, .... the first dipole sub was completed today.

                                                        After much pondering, I decided to discard the push-pull idea because:
                                                        - Cavity is small enough as it is and additional barrier takes up space
                                                        - Operationally I want to be able to remove the woofers one day
                                                        - It is simpler to build, less time freezing in the cold :P

                                                        Click image for larger version

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                                                        This dipole sub is 22cm wide. It's actually 2cm narrower than those desktop OBs at the back!

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                                                        Measuring nearfiled, the quarterwave resonance is at 330hz, which is great as I had planned to cross at 280hz LR4.

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                                                        The blue graph shows raw nearfield response. The Black graph shows equalised response with LT target set at 20hz, Q=0.5 along with 300hz notch filter and 280hz LR4 lowpass XO.
                                                        Last edited by theSven; 03 May 2023, 21:46 Wednesday. Reason: Update image location
                                                        gainphile.blogspot.com

                                                        Comment

                                                        • sfdoddsy
                                                          Senior Member
                                                          • Sep 2000
                                                          • 496

                                                          #29
                                                          How does this affect force cancellation?

                                                          Do they rock?
                                                          Steve's OB Journey

                                                          Comment

                                                          • 5th element
                                                            Supreme Being Moderator
                                                            • Sep 2009
                                                            • 1671

                                                            #30
                                                            There is no force cancellation as both drivers move in unison. It would be beneficial to add in extra partitions/holes, so that with both drivers mounted in the same way, the rear output of the top driver is routed backwards, while the front output of the bottom driver is routed backward also. To keep the phase of the two coherent one driver would need to be wired in antiphase, this would give you both force cancellation plus the additional benefits of even order harmonic cancellation, but as gainphile mentioned it makes the box harder to construct and also makes it somewhat harder to install/remove the drivers.

                                                            At lower spls though I don't think it would give you that many benefits, so is a fair trade off for the narrow profile of a system that probably isn't being designed to reach very high SPLs anyway. My XLS containing H baffles, similar to the old orions used to rock quite considerably at high SPLs, which is probably why Linkwitz swapped to the current implementation.

                                                            I am highly intrigued by this approach mind you, it would make perfect use out of some of the Audax HT240G0s I picked up cheaply from ebay a few years ago, although this isn't going to happen any time soon!
                                                            What you screamin' for, every five minutes there's a bomb or something. I'm leavin' Bzzzzzzz!
                                                            5th Element, otherwise known as Matt.
                                                            Now with website. www.5een.co.uk Still under construction.

                                                            Comment

                                                            • cjd
                                                              Ultra Senior Member
                                                              • Dec 2004
                                                              • 5568

                                                              #31
                                                              I'll probably whip up a test W baffle somewhere in the next few months. For the frequencies I'm hoping to reach, opposed-mounted and firing is a must; I'll probably be directly coupling the drivers too (dowels from bolt to bolt between them or similar.) Definitely an interesting solution.

                                                              Two drivers that fired opposite ways but aren't directly facing each-other would still have torsional issues - that may even be more likely to cause a speaker to walk. No idea.

                                                              Can't wait to see how this turns out - so far looks like things are working to plan. Very cool.
                                                              diVine Sound - my DIY speaker designs at diVine Audio

                                                              Comment

                                                              • gainphile
                                                                Senior Member
                                                                • Apr 2009
                                                                • 107

                                                                #32
                                                                5th is correct there. The subs do not have the force on par to Peerless XXLS nor L26RO4Y so they are less of a problem. Also the vibration is lateral to the sides.

                                                                I did briefly try to drive it with 20-30hz signal to xmax, and even on my desk the vibration is not noticable.

                                                                Woofer maintenance is very easy with this approach. That right panel can be removed entirely (see unfinished screws there) and provide full access to the woofers.

                                                                Can't wait for the weekend to finish them ....
                                                                gainphile.blogspot.com

                                                                Comment

                                                                • Juhazi
                                                                  Senior Member
                                                                  • May 2008
                                                                  • 239

                                                                  #33
                                                                  Hi, looking more and more interesting! I like low extension and moderate spl capacity. Please check the effect of the distance to the back wall. I think that most people have only max 0,5m behind the speaker's front plane.
                                                                  My DIY speaker history: -74 Philips 3-way, -82 Hifi 85B, -07 Zaph L18, -08 Hifitalo AW-7, CSS125FR, -09 MarkK ER18DXT, -13 PPSL470Dayton, -13 AINOgradient, -18 Avalanche AS-1 dsp, -18 MR183w

                                                                  Comment

                                                                  • 5th element
                                                                    Supreme Being Moderator
                                                                    • Sep 2009
                                                                    • 1671

                                                                    #34
                                                                    Originally posted by gainphile
                                                                    5th is correct there. The subs do not have the force on par to Peerless XXLS nor L26RO4Y so they are less of a problem. Also the vibration is lateral to the sides.
                                                                    You make a good point there, both the SEAS and the original XLS have very high moving masses, it's not a surprise really to find that they would cause more of a problem then drivers with lighter cones.

                                                                    Two drivers that fired opposite ways but aren't directly facing each-other would still have torsional issues - that may even be more likely to cause a speaker to walk. No idea.
                                                                    You are right having the drivers like I described would cause a kind of catherine wheel effect about the mid point of the cabinet...Walking with the XLS H baffles wasn't a problem though as they were spiked into the carpet through to the floorboards beneath. The tops of the mid/tweeter baffle though would shake too and fro. I wonder if the cabinet is prevented from walking if the opposed firing would reduce this, I can't imagine it making it any worse though.

                                                                    I guess a quick test would be to wire one of the drivers with reversed polarity in a standard H baffle, only my XLSs aren't in the H baffles anymore so I can't give it a try.
                                                                    What you screamin' for, every five minutes there's a bomb or something. I'm leavin' Bzzzzzzz!
                                                                    5th Element, otherwise known as Matt.
                                                                    Now with website. www.5een.co.uk Still under construction.

                                                                    Comment

                                                                    • gainphile
                                                                      Senior Member
                                                                      • Apr 2009
                                                                      • 107

                                                                      #35
                                                                      Finally the woodworking is completed. So now I can move on to the fun part


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                                                                      I could add the dress panel and grill, but the looks of these things are just so "not loudspeakers" I really like them as it is.

                                                                      The final build is actually 2cm narrower and shorter than planned. It's now 21.5cm x 95cm x 30cm (yes the depth had increased by 3 cm). Here I make a comparison with linkwitz pluto clone.

                                                                      Quite petite dipoles!

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                                                                      The Zaph woofer is really stunning in real life with that oak baffle. They have just the right amount of shine!
                                                                      Last edited by theSven; 03 May 2023, 21:46 Wednesday. Reason: Update image location
                                                                      gainphile.blogspot.com

                                                                      Comment

                                                                      • JonMarsh
                                                                        Mad Max Moderator
                                                                        • Aug 2000
                                                                        • 15259

                                                                        #36
                                                                        Coming along nicely! :T How long till you can fire them up?

                                                                        I'm jealous of all you guys making progress on your projects- was working this Saturday, and getting ready for my business trip to Houston today- it's 6:30 AM at Starbucks and I'm getting ready to head out shortly.

                                                                        Watching your projects progress helps me psychologically... keep up the great work!
                                                                        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

                                                                        • gainphile
                                                                          Senior Member
                                                                          • Apr 2009
                                                                          • 107

                                                                          #37
                                                                          Well I've fired them up tonight!

                                                                          It will take some more time and lucky weather for the final xo to be posted, but the guestimate indoor measurement sounds good. Usually I miss by 100-150hz compared to the outdoor one.

                                                                          For the moment, the zaph kit is equalised using one 650hz notch and a shelving lowpass filter to compensate the dipole effects. The subs are eq'd as before at 20hz. I actually had to reduce the level to -2db.

                                                                          I really like how they dissapear very convincingly. I had tried this in the past and the narrower the baffle, the better it is.
                                                                          gainphile.blogspot.com

                                                                          Comment

                                                                          • 5th element
                                                                            Supreme Being Moderator
                                                                            • Sep 2009
                                                                            • 1671

                                                                            #38
                                                                            I'm liking the concept of this idea even more, especially as I've got drivers that need good homes. I am sure I will try something like this at some point down the line.

                                                                            I really do wish that Zaph would open up trading with somewhere like Europe Audio so us lot on the other side of the pond could get our hands on his awesome driver. There are a lot of us folk over here, I'm sure it would be profitable, just have madisound act as an intermediate distributor.
                                                                            What you screamin' for, every five minutes there's a bomb or something. I'm leavin' Bzzzzzzz!
                                                                            5th Element, otherwise known as Matt.
                                                                            Now with website. www.5een.co.uk Still under construction.

                                                                            Comment

                                                                            • gainphile
                                                                              Senior Member
                                                                              • Apr 2009
                                                                              • 107

                                                                              #39
                                                                              Some more picx detailing the speakers.

                                                                              ZA Driver

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                                                                              Passive ZA5.2 crossover tucked in nicely. I had to put foam below them to stop them from vibrating.

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                                                                              Last edited by theSven; 03 May 2023, 21:47 Wednesday. Reason: Update image location
                                                                              gainphile.blogspot.com

                                                                              Comment

                                                                              • its_bacon12
                                                                                Member
                                                                                • May 2008
                                                                                • 73

                                                                                #40
                                                                                Awesome work!! Very excited to see the final outcome!!!!

                                                                                Comment

                                                                                • Jonasz
                                                                                  Senior Member
                                                                                  • Nov 2004
                                                                                  • 852

                                                                                  #41
                                                                                  Looking good!

                                                                                  Can these play at louder than normal (whatever that is :B ) levels? Two tens down to 20 hz doesn't sound like a lot but maybe they surprise!?

                                                                                  Very interesting indeed this... :T

                                                                                  Comment

                                                                                  • owdi
                                                                                    Member
                                                                                    • Feb 2008
                                                                                    • 62

                                                                                    #42
                                                                                    Any reason why you chose the TM crossover rather than the in-wall? I would think you want to avoid the built in BSC of the TM version. 3db more sensitivity thanks to the smaller inductor and less padding on the tweeter.

                                                                                    Comment

                                                                                    • cjd
                                                                                      Ultra Senior Member
                                                                                      • Dec 2004
                                                                                      • 5568

                                                                                      #43
                                                                                      Originally posted by owdi
                                                                                      Any reason why you chose the TM crossover rather than the in-wall? I would think you want to avoid the built in BSC of the TM version. 3db more sensitivity thanks to the smaller inductor and less padding on the tweeter.
                                                                                      Dipole *adds* to the loss you already get from the 2pi>4pi transition, so starting with full BSC means he's only adding dipole correction to the mix.
                                                                                      diVine Sound - my DIY speaker designs at diVine Audio

                                                                                      Comment

                                                                                      • 5th element
                                                                                        Supreme Being Moderator
                                                                                        • Sep 2009
                                                                                        • 1671

                                                                                        #44
                                                                                        Well technically speaking there is no bafflestep loss in going from 2pi to 4pi with an open baffle loudspeaker. Bafflestep and OB losses do start at the same point, as governed by the baffles width, but with an OB you don't have to compensate for open baffle losses and then on top of that compensate for baffle step losses, you only need to compensate for the OB losses, which are 6dB/octave, rather then the 6dB bafflestep transition which occurs over the range of a couple of octaves.

                                                                                        What you do have to compensate for with an open baffle is the inherent Qts of the driver being used. Like with the original Orion where LW used the peerless XLS drivers, these have a Q of around 0.2 and a very low fs. Now when placed in an OB these exhibit the standard 6dB/octave roll off, but they also have the very low Q roll off added to this. In this case you need to use the Linkwitz transform circuit to equalise the driver, LW chooses a target of 40Hz with a Q of 0.5 iirc, after which you apply the standard 6dB/octave shelving filter. This is why it make sense to use a driver with a Qts of around 0.5-0.7, but even with this they still need the shelving filter.
                                                                                        What you screamin' for, every five minutes there's a bomb or something. I'm leavin' Bzzzzzzz!
                                                                                        5th Element, otherwise known as Matt.
                                                                                        Now with website. www.5een.co.uk Still under construction.

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                                                                                        • gainphile
                                                                                          Senior Member
                                                                                          • Apr 2009
                                                                                          • 107

                                                                                          #45
                                                                                          Well I had the chance to put them into moderate pace before work today. Played Herbie Hancock "Autodrive" and Kraftwerk's "Telephone Call", "Aero Dynamik" ... basically to push the woofers. Quite stunning really the output of these. I will need an empty house to push them louder though.

                                                                                          What strikes me most is how they simply dissapear and blend into the room. Much better than my 8" dipoles and I attribute this acoustically (and visually!) to the smaller baffle. It seems that they don't have the attack of their bigger brother, though but this is a very early crossover. Resolution is outstanding as I observed earlier.

                                                                                          I use the MT kit as they were the ones which Zaph sent . But I don't see any reason why the other types (even MTM) can't be used. The steps are quite simple:

                                                                                          - Pick a target frequency, in my case flat response from 20khz down to 20hz Q=0.5 (meaning -3db at 30hz and -6db at 20hz)

                                                                                          - Measure raw response of the sub and the Woofer-Tweeter panel, and equalise accordingly.


                                                                                          So my preliminary crossover is something like this:

                                                                                          For subwoofer I applied:
                                                                                          - Notch filter to compensate quarterwave resonance
                                                                                          - Driver EQ using linkwitz transform (to obtain 20hz Q=0.5)
                                                                                          - Dipole rolloff EQ to compensate -6db/oct rolloff

                                                                                          Click image for larger version

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                                                                                          And for Woofer-Tweeter Zaph kit I apply:
                                                                                          - Dipole peak notch
                                                                                          - Dipole rolloff EQ to compensate -6db/oct rolloff

                                                                                          Click image for larger version

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                                                                                          Quite simple really and the whole circuit (including 280hz xo) can also be realised by using 6 op-amps if desired. But why bother making PCBs when MiniDSP is $99 :T

                                                                                          The most critical is that dipole peak notch. The frequency, notch depth, and Q can only be obtained accurately by outdoor, elevated measurements. For that I need some good weather :P
                                                                                          Last edited by theSven; 03 May 2023, 21:47 Wednesday. Reason: Update image location
                                                                                          gainphile.blogspot.com

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