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Lab 15 Subwoofer Build - New Guy - Advise Appreciated

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  • Lab 15 Subwoofer Build - New Guy - Advise Appreciated

    Speaker building is very interesting and complex. Reading the posts has helped me appreciate the learning and science involved in sound and the complexity of reproducing sound and music. After reading hundreds of posts I decided to build Paul Camody's Classic II speakers. Awesome sound for my office of about 120 sq feet.

    A brilliant idea struck me...Build a sub woofer for my home and PA system. In review of hundreds of sub woofers and trying to understand the specifications I'm barely above understanding DB, Xmax, response charts, etc. So I decided to build a 12-15 inch sub which would be portable and produce excellent bass home and small PA use. I often speak to groups of 20-60 and play music before and after at modest levels with a Yamaha 600i. Bill Fitzmaurice's designs are excellent but I don't have the wood working skills to make that happen.

    2 months ago there was a post about a Eminence 4 ohm lab 15's on e bay that were selling very reasonably. I made an impulse buy and bought 2, as they had been mentioned in several posts as awesome and very durable.

    Next, I spent the last month or so trying to understand how to load the information into a couple of sub woofer enclosure programs and realized that I was over my head. That lead me to order the 3 cu ft Dayton 15 inch reference enclosure and 10 pounds of accustic-fill. This was based upon reading eminence's sealed design for the speakers.

    Please - no haters - before I begin putting this together I'd appreciate advise on if this will be successful. Second, will I need a cross over. Eminence suggests a steep high pass filter at 25hz. Some of my reading indicates maybe a low pass sub filter at 150hz. Should I attempt to port this or just build seal and connect. I'm using another buyout special I found a crown xls amplifier so I have some control of the system.

    Any Help Greatly appreciated. Click image for larger version

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  • #2
    Re: Lab 15 Subwoofer Build - New Guy - Advise Appreciated

    Well, they'll do about 50Hz in your 3cf stuffed box. Is that low enough for you? I've got a design that uses 4" woofers and they'll get down to 40, so, for me, it wouldn't be low enough.

    A vented box would be about twice that size (6 cf), but would go an octave lower, down to 25Hz. I'd put a pair of 4"id port tubes in there that were each 13" long. No stuffing or lining required.

    Most guys power these things with a "plate" (subwoofer) amp. Those typically have an HP filter built in, and have an adjustable LP filter - commonly set to between 50 and 80Hz or so. For a vented box like this, you'd most likely want an amp w/OUT any "boost".

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    • #3
      Re: Lab 15 Subwoofer Build - New Guy - Advise Appreciated

      Sorry to say it but unless horn loaded the Lab 15 lacks the sensitivity required for PA, and unless loaded in a fairly large ported enclosure they won't go low enough for HT. If I were you I'd load the Dayton enclosures with the correct drivers, sell the Lab 15s, and chalk up any loss you may take on the deal as a lesson learned.
      www.billfitzmaurice.com
      www.billfitzmaurice.info/forum

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      • #4
        Re: Lab 15 Subwoofer Build - New Guy - Advise Appreciated

        I have a pair of these also with an intended build in mind. Personally I would use ported as well. 5 cubes tuned to 28hz is where I ended up. If that is to big, there is the option of PRS with the 3 cube enclosures. Dual CSS APR15s will work and are easily tuneable. Another to consider is the AE18. Less money but you not as easily tuned.

        For hard core PA use they may lack (depending on your needs) but I have used a single lab15 for a small party and it did great! The owner of the sub and I are now working on a more HT based design for it that will have output down into the 20hz range easily. I believe we are looking at 117db with 1000w.
        https://www.facebook.com/Mosaic-Audi...7373763888294/

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        • #5
          Re: Lab 15 Subwoofer Build - New Guy - Advise Appreciated

          You can salvage your situation with a large power amp with built in digital processing to EQ your small sealed sub for deeper bass. And swapping your 15s for a better fit to the box isn't going to cost you that much more $$. If you're only asking for moderate output to a small crowd it'll be fine in fact you might appreciate the compact system.

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          • #6
            Re: Lab 15 Subwoofer Build - New Guy - Advise Appreciated

            There are two (one in particular) builds that are written up in the DIY Audio forum that impress me (the one in particular is the one I'll be building). The plans are very complete. There is also a build on AVS that is worth considering.

            If I have time later, I'll post the links - but the one in DIY is easy to find. IIRC - it goes down to 35 Hz.

            Here it is. 150L, 35 Hz

            http://www.diyaudio.com/forums/subwo...-order-56.html

            See post 552.
            Sausage With Meat Sause, Please

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            • #7
              Re: Lab 15 Subwoofer Build - New Guy - Advise Appreciated

              I would just try to sell the boxes. You need something bigger to port the 15". If you can accept not having 20hz bass then you can make a sub that will be PA capable, and better then many commercial home subs.

              You're going to want at least a 4 ft3 cabinet, here's a kit for one

              http://www.parts-express.com/knock-d...ffle--300-7088

              Dont be afraid to install handles and locking casters if that makes your PA application easier. For the port you will need 3 ea 3" round x 16" long ports. You can just grab a piece of PVC pipe from Lowes and cut it down. This will tune your box to about 28hz. For an amp get a Behringer EP4000. It is fairly low cost and legitimately puts out 650 watts per channel at 4 ohms, it also has a selectable 30hz high pass filter which you will need to turn on.

              All in all you will have a box that can get fairly loud without reaching xmax, and have an f10 of 25hz giving you a decent HT setup when corner loaded inside

              Click image for larger version

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              http://jaysspeakerpage.weebly.com/

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              • #8
                Re: Lab 15 Subwoofer Build - New Guy - Advise Appreciated

                Another option is to try and turn the 3 cu ft sealed box into a vented cabinet. Modeled performance in 2.5 cu ft tuned to 35 Hz really is not all that bad (~33 Hz F3), although it definitely models better in 4 cu ft plus.

                Modeled FR Graph (2.5 cf tuned to 35 Hz):
                Click image for larger version

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                EDIT: Never mind. The Lab15 in BassBox specs out very different than the parameters listed in the original post
                Last edited by Jethro; 12-20-2014, 04:07 PM.
                | there is no spoon... |

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                • #9
                  Re: Lab 15 Subwoofer Build - New Guy - Advise Appreciated

                  Originally posted by scholl View Post
                  You can salvage your situation with a large power amp with built in digital processing to EQ your small sealed sub for deeper bass.
                  There's no such thing as a free lunch. Every 6dB of EQ doubles excursion and quadruples power. In a 3 cu ft sealed box the maximum SPL that a LAB 15 can reach at 20Hz is 100dB, assuming that there's no such thing as power compression, but there is. A LAB 15 and a 3 cut ft sealed box is a mis-match, pure and simple.
                  www.billfitzmaurice.com
                  www.billfitzmaurice.info/forum

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                  • #10
                    Re: Lab 15 Subwoofer Build - New Guy - Advise Appreciated

                    I'd use the 3 cubic foot sealed boxes for another project.

                    DIY Sound Group has a 4.15 cubic foot ported sub box that works with the 6 ohm version of the Lab 15. I realize you have the 4 ohm version, but this would be a better option than the sealed boxes and wouldn't require any boost. Your Crown XLS Drivecore amp doesn't have a bass boost feature anyway so that would require another purchase.

                    http://www.diysoundgroup.com/ported-subwoofers-1.html

                    Not sure how to accomplish a 25 Hz subsonic filter that Eminence suggests for the 4 ohm versions of the Lab 15 drivers.
                    1: Sony DVP-S7000 | Denon DVD-2900 | Laptop > Parasound Zdac > Denon AVR-5700 > Focal 826V | Def Tech BP2000 | (2) DIY 15" Subs powered by Crown XLS2500
                    2: Computer > Schiit ‹bered Bifrost > Emotiva RCA Control Freak > Crown XLS 1500 > Focal 706V | Def Tech SM450 | Velodyne F-1000B Sub

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                    • #11
                      Re: Lab 15 Subwoofer Build - New Guy - Advise Appreciated

                      Well, live and learn!

                      I also picked up 2 of these and wondered at the time why not too many were interested.
                      Now I see. No substitute for carefully modeling before the purchase.
                      Oh well, I'm sure I"ll find a use for them. Maybe an isobaric design....

                      I think I hear a difference - wow, it's amazing!" Ethan Winer: audio myths
                      "As God is my witness I'll never be without a good pair of speakers!" Scarlett O'Hara

                      High value, high quality RS150/TB28-537SH bookshelf - TARGAS NLA!
                      SB13/Vifa BC25SC06 MTM DCR Galeons-SB13-MTM
                      My Voxel min sub Yet-another-Voxel-build

                      Tangband W6-sub

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                      • #12
                        Re: Lab 15 Subwoofer Build - New Guy - Advise Appreciated

                        Originally posted by donradick View Post
                        Well, live and learn!

                        I also picked up 2 of these and wondered at the time why not too many were interested.
                        Now I see. No substitute for carefully modeling before the purchase.
                        Oh well, I'm sure I"ll find a use for them. Maybe an isobaric design....
                        They should be fine for music, just not so much for home theater.
                        1: Sony DVP-S7000 | Denon DVD-2900 | Laptop > Parasound Zdac > Denon AVR-5700 > Focal 826V | Def Tech BP2000 | (2) DIY 15" Subs powered by Crown XLS2500
                        2: Computer > Schiit ‹bered Bifrost > Emotiva RCA Control Freak > Crown XLS 1500 > Focal 706V | Def Tech SM450 | Velodyne F-1000B Sub

                        Comment


                        • #13
                          Re: Lab 15 Subwoofer Build - New Guy - Advise Appreciated

                          Originally posted by donradick View Post
                          Well, live and learn!

                          I also picked up 2 of these and wondered at the time why not too many were interested.
                          Now I see. No substitute for carefully modeling before the purchase.
                          Oh well, I'm sure I"ll find a use for them. Maybe an isobaric design....
                          If you plug the specs into WinISD and let it go to the default maximally flat response it gives you a 2 cu ft ported cab with an f3 of 34Hz and 90dB sensitivity, which doesn't make a lot of sense from a driver of that size, as it doesn't go low enough for HT or loud enough for pro-sound. Load the specs into HornResp and see what it will do in a horn, its intended usage, and it's a very different story.
                          www.billfitzmaurice.com
                          www.billfitzmaurice.info/forum

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                          • #14
                            Re: Lab 15 Subwoofer Build - New Guy - Advise Appreciated

                            My personal plan for them is a 5cube section of 24" sonotube tuned to about 28-30hz. 150-200hz LP. That is only about 20 internal. F3/6/10 of 27/23/20 no eq, no ssf.
                            https://www.facebook.com/Mosaic-Audi...7373763888294/

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                            • #15
                              Re: Lab 15 Subwoofer Build - New Guy - Advise Appreciated

                              Originally posted by billfitzmaurice View Post
                              If you plug the specs into WinISD and let it go to the default maximally flat response it gives you a 2 cu ft ported cab with an f3 of 34Hz and 90dB sensitivity, which doesn't make a lot of sense from a driver of that size, as it doesn't go low enough for HT or loud enough for pro-sound. Load the specs into HornResp and see what it will do in a horn, its intended usage, and it's a very different story.
                              Hmm, I took a look at the thread over on DIY Audio, and I'm warming to the idea of a horn. I'm pretty sure whatever I build is going to end up in the corner, so I've got that to
                              model also (but I know that it will help efficiency a lot -- just worked it out in my head... it's 18 dB more efficient, right?)

                              Bill, I'd build one of your TTs and be done with it, but it's too big for my room. I'm thinking about 20 inches max.

                              Anyways, just googled for about 10 minutes and I can't find the HornResp software. Anyone got a working link?

                              I think I hear a difference - wow, it's amazing!" Ethan Winer: audio myths
                              "As God is my witness I'll never be without a good pair of speakers!" Scarlett O'Hara

                              High value, high quality RS150/TB28-537SH bookshelf - TARGAS NLA!
                              SB13/Vifa BC25SC06 MTM DCR Galeons-SB13-MTM
                              My Voxel min sub Yet-another-Voxel-build

                              Tangband W6-sub

                              Comment

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