Secrets of Simple Sub, with Adire DPL 12

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  • JonMarsh
    Mad Max Moderator
    • Aug 2000
    • 15260

    Secrets of Simple Sub, with Adire DPL 12

    Just a tale about work in progress, who's only moral is to consider your options and choices carefully. This is about making a "simple sub" from stuff on hand- for testing with the development version of my monolith line array, and to use in my bedroom system.

    I'm getting ready to resume work soon on the RD50 based line array, and prior to building the final cabinets, especially the woofer boxes, I wanted something to work with them for the bottom end. Being my usual penurious self, I figrure I could toss something together with bits and pieces I have lying around... don't want to spend any moolah right now on this. Since I've got a few drivers on hand, seems like I have some choice to work with. Twelve inch drivers I have "in stock" include the Adire Shiva, the Blueprint 1203 (which I'm planning for the finished version of the monolith, using an LT equalizer), Titanic MkII's, and Adire DPL12's.

    It's times like these that I'm really thankful to Christian Ouugard and his wonderful program, "Unibox". IMO, it's the easiest and most power ful LF analysis program you can get, and what's even better, is it's free, as long as you have Excel 2000 or later to run it on. I have a copy of Bass Box Pro which has languished in the dust bin now for some time, since I started using Unibox 2.33, now up to version 4.03. You can get it here:






    Unibox

    Using Unibox is a breeze, because though it can handle advanced LF simulation parameters if you have them for the driver, it doesn't need much to get a good driver model- Fs, VAS, Qes, Qms, Xmax, and Sd, and you're in the ballpark. It calculates all the others from these parameters, so you can do a sanity check on the model as well as the T/S parameters. It's pretty amazing to see it come up within a couple of percent on the estimated cone mass, suspension compliance, Qts, etc., that are on the manufacturer's spec sheets.

    Anyway, for a simple sub, I don't need anything fancy- what I want is maximal LF extension in the NOS Woodstyle 62 liter sub cube I have in the original carton in my garage. And with Unibox you can readily calculate the response, including the limitation on acoustical output due to driver Xmax, Sd, etc.

    So which do I use in my simple sub, and why?

    Well, the choice is simple, really, after reviewing the data. I'm using the "dipole" driver, the Adire DPL12, in my sealed sub. Why? Well, though it's a couple of dB less efficient in midband sensitivity, for a sub, it's what you get down low that counts, and what the overall balance is. From the upper midbass, say 100 Hz, the -6 dB point is what's of interest to me, as well as the Q and roll off rate. With good room placement, and typical room gain, you can get the -6 dB point pretty much flat in room. The -6 dB point for the DPL12 in this box is 22 Hz!! For the other drivers, it's about 30 Hz. With a little more box volume, say, 75 liters, you can get the -6 dB point at 20 Hz, with a Bessel alignment on the roll off, which means the Q is pretty much minimum delay, and nearly critically damped.

    Frankly, if you don't have the room or architectural support for a true IB sub, using arrays of the DPL12 in 75 liter boxes will give you essentially the same thing. The F10 is 15 Hz in the 75 liter configuration. Light shelving EQ, and I mean lite, say, 4 dB, could bring you to in room flat to 15 Hz. With multiple drivers, we could have some serious fun tonight. OTOH, it doesn't roll off the tongue the same way as "Twelve Shiva's Dancing".

    Max anechoic output at 1 meter at 20 Hz is 98 dB. With room gain, about 104. Two would give you 110. Four would net in room about 116. You get my drift? No EQ required for that, either. Power required is about 150 watt per driver, allow 300 watts at four ohms for headroom on transients at higher frequencies- that would give you about 105 dB at 1 meter anechoic at 30 Hz. Call it 110 with room support.

    Bottom line? For ported systems, with EQ and HP filters, go ahead with your Shiva or Titanic MkII. For simple, wideband, excellent time domain performance in a sealed box, make it a good dipole driver- the Adire DPL12.

    I also evaluated Isobarik, and my conclusion was that the gain below 30 Hz in Fs wasn't worth the expense- the DPL12 has a curve a lot like Isobarik Shivas, but with 2 dB less sensitivity, and only a single driver.

    What's not too like?


    I'll be building this shortly, and document the process and the results. Let's see how Unibox predictions stack up against the real world on this one.







    Regards,

    Jon




    Earth First!
    _______________________________
    We'll screw up the other planets later....
    the AudioWorx
    Natalie P
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    Resistance is not futile, it is Volts divided by Amperes...
    Just ask Mr. Ohm....
  • Andrew Pratt
    Moderator Emeritus
    • Aug 2000
    • 16507

    #2
    Curious findings Jon. If you were starting freash though given that the DPL12 costs the same as the tempest would you still pick the DPL12? (assuming you were limited in box size)




    Comment

    • Dennis H
      Ultra Senior Member
      • Aug 2002
      • 3791

      #3
      Interesting, Jon. Are you comparing to the 12" Titanic or the 10"? When I plug the DPL-12 and the 12" Titanic Mk2 into a modified version of one of SL's spreadsheets, I get box sizes and 8 ohm equivalent power within a few percent of each other. The unequalized Fb is higher with the Titanic but it's slightly more efficient so, after EQ, they are about the same. I'd choose the Titanic just because of more Xmax rather than any real difference in small signal performance.

      Quicky numbers into 4pi space: no fiddling with stuffing or room gain or anything

      Titanic
      121 L, unequalized response: Q=.577, Fb=32Hz
      8ohm equivalent power for 100dB nominal, EQ'd to .577/20Hz
      100W at 20Hz, 47W at 40Hz

      DPL12
      127 L, unequalized response: Q=.577, Fb=24Hz
      8ohm equivalent power for 100dB nominal, EQ'd to .577/20Hz
      105W at 20Hz, 79W at 40Hz

      Comment

      • Dennis H
        Ultra Senior Member
        • Aug 2002
        • 3791

        #4
        As an aside, the T/S parameters look really similar for these two drivers with the exception of Mms and the effect that has on the others. I don't think Adire publishes the Mms of the DPL-12 (wonder why?) but I calculate it at a whopping 232 grams. Tape a 90 gram weight to the cone of your Titanic and you'll have a DPL-12. :LOL:

        Comment

        • sfdoddsy
          Senior Member
          • Sep 2000
          • 496

          #5
          Interesting. I have 5 DPL12s at the moment, four of whihc are in my dipoles. But I also replaced the Shiva driver in my EBS Shiva with a DPL12 (bolts straight in).

          I haven't measured it yet, but according to Unibox this produces a slight bass hump just above 20Hz, and it sounds that way.

          However, I've been thinking about sealing the port and running it as a 142L sealed sub, with maybe a bit of boost if necessary. Any thoughts on this?

          And, of course, what is the best way to plug a port?


          Steve




          Steve's DIY Dipoles
          Steve's OB Journey

          Comment

          • JonMarsh
            Mad Max Moderator
            • Aug 2000
            • 15260

            #6
            Hello Andrew,

            Well, especially if I was limited in box size, I'd think carefully about the choices, and what my goals were. Now, using this Woodstyle box that I have on hand, I've got a given- no way around that. And even the box I was planning for my line array system has the same planned volume- though I've been planning on using the BPD1203 in that enclosure.




            The tradeoffs can be substantial- for example, going from the DPL12 to the BPD1203, I gain the potential for 4 dB more output at 20 Hz- but the required power goes from ~150 watts to 1 kW at 4 ohms! And about 8 dB of EQ is required to overcome the higher Fs, as part of an LT network. Fortunately I have a pair of Aragon Palladiums that can handle that chore.... Is it worth it though? Tough call. Depending on the room you have, doubling up on the number of bass cabinets, wiring them in series, and using an amp good for 400-500 W at 8 ohm would accomplish the same thing- but be much bigger.

            Re the Tempest, let's see, a low Q net sealed design for a single Tempest is typically a 230 liter enclsore, (vs 75), and the Butterworth 0.707 (punchier, not as deep in the bass) is 160 liter. Neither of these is a small box, obviously. Vented things get even bigger, check out the EBS alignment. Who, mamma, 340 liters! I can do four DPL12's in two 140-160 liter boxes, which give me a lot of Sd and swept volume, but costs more. Now, because Thomas & I bought my DPL12's on the original introductory buy in volume, we got a pretty friendly price, and I do tend to forget what the normal MSRP is. But if you look at the driver construction and build quality, you don't have to be a rocket scientist to see you're getting a fair amount for your money. It's a beautiful cast frame, very well designed, all the things you MUST do to make it a good dipole driver help rather well in sealed applications.

            Now, the DPL12 really isn't designed for ported applications, whereas the Shiva and Tempest are designed to kind of bridge the two, so you can have your cake, or have your brownies, or have your cake style brownies- and that works pretty well up to a point. You CAN come up with a ported alignment for the DPL12 without peaking, but it's in a largish box, with the port tuned down to about 15 Hz. That will increase the sub 25Hz output capability substantially, until you go below the box tuning. But, even being a fairly well damped vented alignment (box stuffed in tuning I came up with), the step response takes over 60 milliseconds to settle out, where as the sealed 60-75 liter alignment takes a little less than 20 msec. This settling time is what differentiates "fast bass" from "slow bass" in my experience.

            So, it comes down to a few questions, as to one's preferences- if you have 160 to 300 liters to play with, how do you want to do it, how much money, how much power, etc?

            If you want to make the most SPL for the least money, then I think the Tempest might be your choice, especially if you can handle one of the larger boxes.

            Now, if you're space limited, things look different- I start to argue for the DPL12- in two 60-75 liter enclosures, a pair of these will move a pretty good bit of air, not as much as an EBS vented TEMPFEST, but very competitive with a sealed TEMPEST in a 230 liter box, and smaller.

            If one has the room for an EBS TEMPEST, and you have a few more sheckles to spend, and you DON'T want the big bucks amps that something like an HE15 or Tumult requires, then four DPL12's distributed between two 150 liter enclosures or four 65-75 liter enclosures look real promising. A cheap multi-channel amp could be used to drive them, wiring one driver to each channel. They'll go deep, and if you built the boxes well, the sound quality will surpass any vented box- you'll be the closest you can get to a big IB setup without getting into rennovations. But, at MSRP, you'll be out $600 in drivers. Not cheap, but geez, have you priced a Paradigm Servo 15? Peanuts, in comparison. And not expensive to drive.

            I'm actually considering extending my bottom end cabinets on the line array, to use dual DPL12's, just becuase I suspect it will be more relaxed sounding than a single BPD1203. But, I suppose the only way to know for sure, is do the time honored AudioWorx research technique, and build both. :yesnod: It's only MDF, right? And I've got the drivers... Then, the Palladium's would really be loafing, as at 8 ohms they're capable of 600+, but we only need ~ 300-400. Still leaves me with needing something to do with the BPD1203's. But then, I wouldn't have to build in a bass equalizer to my Sumo Delilah crossover. :B



            So, I'd say what this recommendation is about, is balance, a balance in tradeoffs. Ultimately, the correct choice depends on one's priorities.


            Hi Dennis!

            I was comparing to the Titanic 12" MkII; I model them for fixed size enclosures, using Unibox. In this case, the size was 62 liters (run what ya got). My lame point was NOT using EQ, wanting something simple and easy to work without going the extra mile with electronics.

            By my calc, the Mms of the DPL12 is up there- about 225 grams, which is pretty similar to your numbers- I doubt that Christian and Sigfried do the math much differently! :W

            And I'm too cheap and lazy to find a 90 gram weight to tape to my Titanic! Remember? :W Simple! (yeah, I must have had a stroke or something for me to be talking about "simple"!)


            Steve,

            With a 142 liter box, you should almost be going with TWO DPL12's! Though some folks try stuffing porst with foam, or towels, or other such things, that's akin to saying, "I'm going to make an acoustic suspension cabinet and leave a lot of leaks in it! " It changes the tuning, damps it of course, but with 140 liters, it's already more like an IB than acoustic suspension! I'd board it over; that's what I've done in the past.

            Interesting comments, all. Now after this discussion I'm seriously considering changing the size of the monolith line bass sections. Gotta see how big that would wind up, whether I can still keep the thing reasonable. Time to go play with AutoCAD- naw, dinner first! Maybe tomorrow!

            :later:

            ~Jon




            Earth First!
            _______________________________
            We'll screw up the other planets later....
            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-Saƫns 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

            • Dennis H
              Ultra Senior Member
              • Aug 2002
              • 3791

              #7
              My lame point was NOT using EQ
              Ah, gotcha, Jon.

              Steve, go to a plumbing store (one where real plumbers shop) and buy a plug. Around here we call them test plugs. Plumbers use them to temporarily seal drain pipes so they can pressure test them. It's a round rubber thing with metal plates on each side and a screw connecting the two plates. You insert it and then tighten the screw to expand the rubber.

              Comment

              • JonMarsh
                Mad Max Moderator
                • Aug 2000
                • 15260

                #8
                Hey, Dennis, that's a pretty good idea for sealing a port- if it's strong enough and wont' crack. IF the ports made with PVC plumbing tube, (schedule 40 is what I've used in the past) I bet that will work great. Precision ports and similar products may require some care in regards to the tightening phase, to avoid popping the tubes.

                Of course, what I don't know about plumbing would fill many, many books. :W

                Regards,

                Jon




                Earth First!
                _______________________________
                We'll screw up the other planets later....
                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-Saƫns 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

                • Dennis H
                  Ultra Senior Member
                  • Aug 2002
                  • 3791

                  #9
                  I wouldn't worry about cracking the port. It doesn't take much to seal one as there's only a small fraction of a PSI inside a sub. The rubber is pretty soft and has a lot of friction so just tighten it enough so you can't easily pull it out with your fingertips and call it good.

                  PS - plumbing's easy. About all you need to know is....

                  1. Hot on the left.
                  2. Cold on the right.
                  3. Sh!t runs downhill.
                  4. Don't chew your fingernails.

                  ;s@

                  Comment

                  • Jack Gilvey
                    Senior Member
                    • Aug 2001
                    • 510

                    #10
                    The DPL-12 (I've got four I grabbed at the original $75 a long time ago) does just about everything. I've recommended it in the past as my favorite sealed box woofer. I've used it sealed, vented, dipole, and IB.

                    However, I've been thinking about sealing the port and running it as a 142L sealed sub, with maybe a bit of boost if necessary. Any thoughts on this?
                    I've done the same, 142L tuned to 18Hz. When sealed this yields a Qtc of .5 or so, and sounds just about perfect (even powered with the el-cheapo Parts Express 300-800 150w plate amp with boost/filter completely defeated) . I used a towel stuffed in a plastic bag. I'm itching to try a 75L box now.

                    Comment

                    • JonMarsh
                      Mad Max Moderator
                      • Aug 2000
                      • 15260

                      #11
                      Yup, I'm in the process of redesigning my monolith line arrays so I can use a large bass section with two DPL 12's on each side. Cabinet will be 140 to 150 liters per two. Since I'll have these out from the walls aways for imaging, I expect it should be hard to tune the rear wall side wall lift for 6 dB or so below 30 Hz. Very slow roll off, and excellent settling time and group delay. Can you spell, "musical" ? :W

                      Got mine the same time you got yours Jack, one of the best speaker deals ever.

                      For both dipole and sealed use, I unequivocally recommend this part, even at it's "normal" price; it's a honey for deep, clean low end without EQ or special tricks.

                      ~Jon




                      Earth First!
                      _______________________________
                      We'll screw up the other planets later....
                      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-Saƫns 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

                      • Jack Gilvey
                        Senior Member
                        • Aug 2001
                        • 510

                        #12
                        Yup, I'm in the process of redesigning my monolith line arrays so I can use a large bass section with two DPL 12's on each side. Cabinet will be 140 to 150 liters per two.
                        Looks like I'll spend part of tomorrow cutting another hole in my 142L box. Methinks I'll put it on the opposite side, the antipodal mounting cancelling out those nasty reactive forces.

                        Comment

                        • Jack Gilvey
                          Senior Member
                          • Aug 2001
                          • 510

                          #13
                          The DPL12 is on sale here for $125 shipped:

                          Comment

                          • sfdoddsy
                            Senior Member
                            • Sep 2000
                            • 496

                            #14
                            Dennis,

                            Thanks for the test plug tip. I got a four inch one, shoved it up the port and it works like a charm.

                            Cheers

                            Steve




                            Steve's DIY Dipoles
                            Steve's OB Journey

                            Comment

                            • PMazz
                              Senior Member
                              • May 2001
                              • 861

                              #15
                              I got a four inch one, shoved it up the port and it works like a charm.
                              Yea, but what about the sub?
                              Pete
                              Birth of a Media Center

                              Comment

                              • sfdoddsy
                                Senior Member
                                • Sep 2000
                                • 496

                                #16
                                Now now, my girlfriend assures me that four inches is average.




                                Steve's DIY Dipoles
                                Steve's OB Journey

                                Comment

                                • Lex
                                  Moderator Emeritus
                                  • Apr 2001
                                  • 27461

                                  #17
                                  Jack, while I can appreciate you pointing to a sale on Adire products at AV, that does absolutely nothing for HTGuide, because anything bought there will not show up on the click through as a sale through HTGuide.

                                  PLEASE click on the sales banners above and below, purchase, and support the Guide! If you don't, who will? We stand a real risk of loosing all of our advertising support if our members don't do a better job supporting them.

                                  Nice post Jon

                                  Lex
                                  Doug
                                  "I'm out there Jerry, and I'm loving every minute of it!" - Kramer

                                  Comment

                                  • Jack Gilvey
                                    Senior Member
                                    • Aug 2001
                                    • 510

                                    #18
                                    Jack, while I can appreciate you pointing to a sale on Adire products at AV, that does absolutely nothing for HTGuide, because anything bought there will not show up on the click through as a sale through HTGuide.
                                    Don't know where my head was...my apologies, Lex.

                                    Comment

                                    • Lex
                                      Moderator Emeritus
                                      • Apr 2001
                                      • 27461

                                      #19
                                      Jack, no problem. I realize that not everyone thinks about our advertisers quite like I do. But that's why I have to inject a dose of reality every now and then. Please don't feel I was picking on you. I wasn't.

                                      Hey, if people want to go the sale route great. At least they bought Adire. But if a few bucks don't mean much, supporting HTG is appreciated.

                                      Lex
                                      Doug
                                      "I'm out there Jerry, and I'm loving every minute of it!" - Kramer

                                      Comment

                                      • peterpan
                                        Member
                                        • May 2004
                                        • 36

                                        #20
                                        How are you getting on with this secrete of a simple sub with Adire DPL12 ? I have my eyes glued on that.

                                        Comment

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