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  • Low Profile Subwoofer

    I've been tossing around the idea of a Boogieman remake that's a little less... subtle.

    I'm basically just theorizing due to budget problems preventing this from becoming a reality, and to learn the some of the different freewares available on the subject.

    Here's my basic idea:
    1. Take 2x Dayton 12" Subwoofers
    2. Put them in a low profile box.
    3. Strap a Bash 300w amp on it.
    4. Make noise.

    Pretty simple, right?

    Playing around with WinISD I've gotten this so far, and this is where I need help:

    Box Dimensions:
    24" x 60" x 9" (External) W/ volume of ~5.5 ft^3
    .75" mdf on sides/back, 1.5" on front.
    2x vents (similar to the boogieman in configuration) that are 7.25" (internal thickness) x 1", creating a vent mach of .06 ( I have no clue what a good mach is )

    Ask for pictures and you shall receive! I don't know what people would like to look at as far as phase/spl/gain/whatever.
    Last edited by Adam_G; 06-12-2012, 10:27 PM.

  • #2
    Re: Low Profile Subwoofer

    What does 'vent mach' mean, is it just velocity? Also what units is it in? And what is a good value if I want as little port noise as possible?

    Comment


    • #3
      Re: Low Profile Subwoofer

      I've been bored, and since I'm better with autodesk than I am with speaker sims, I've tossed together a box based on the dimensions I've been able to decipher from the simulations.





      Cool looking isn't it?!? (Braces + Ports are gray so they stand out a little better)

      Now if only I could figure out if it would work.

      Comment


      • #4
        Re: Questions about Subwoofer build

        I think your low-pro idea would be better with some of these....

        http://www.parts-express.com/pe/show...number=295-134

        http://www.parts-express.com/pe/show...number=295-136

        Later,
        Wolf
        "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
        "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
        "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
        "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

        *InDIYana event website*

        Photobucket pages:
        https://app.photobucket.com/u/wolf_teeth_speaker

        My blog/writeups/thoughts here at PE:
        http://techtalk.parts-express.com/blog.php?u=4102

        Comment


        • #5
          Re: Questions about Subwoofer build

          Originally posted by Wolf View Post
          I think your low-pro idea would be better with some of these....

          http://www.parts-express.com/pe/show...number=295-134

          http://www.parts-express.com/pe/show...number=295-136

          Later,
          Wolf
          Yeah, it's less low profile and more 'lowish' profile, it just has to fit under my couch (futon) which has a fair bit of clearance. It's also a budget project, which kinda eliminates tripling my driver budget unfortunately. Those are pretty boss looking though.

          Do you have any handy-dandy resources you feel work best for vented subs?

          Comment


          • #6
            Re: Low Profile Subwoofer

            Hi Adam,

            ~5ft^3 looks great for this. I'd suggest for your port, to just pick up one of these: http://www.parts-express.com/pe/show...number=268-352

            Use the full 17" included length, that will get you tuned in the ~20hz range. Good for movies or music that way. Peak particle velocity will occur @13hz and not be an issue. Driver excursion will hit 7mm @~125W input around 30-40hz. Translation: 300W bash is a tad overkill, but there aren't many other logical choices. I'd say consider the SPA250, save $50 or so that way (based on current pricing).

            I'm confused about where you're going to mount drivers on this thing... It's going under the futon?
            Pro/Fi Cinema Speaker project: "From the Ashes"

            Comment


            • #7
              Re: Questions about Subwoofer build

              Originally posted by Adam_G View Post
              Yeah, it's less low profile and more 'lowish' profile, it just has to fit under my couch (futon) which has a fair bit of clearance. It's also a budget project, which kinda eliminates tripling my driver budget unfortunately....
              May I assume that this is down-firing? Then you need all the height clearance you can get as you're missing one thing - clearance for the sound.

              The Boogieman has feet on the driver side, but they do nothing but protect the drivers. It's not a down-firing design, but rather a hide-behind-the-couch design.

              The rule of thumb I use is "skirt area same as cone area at the cone edge," the "skirt" being an imaginary cylinder extending from the circular cone edge to the floor. All the sound coming from the cone has to pass through this skirt, so the skirt area should be no smaller than the cone at the interface.
              - cone area is R^2*pi
              - skirt area is 2Rh*pi
              where R is the radius of the cone and h is the clearance under the sub.

              Setting these equal, pi and R cancel and you're left with R=2h - you need clearance under the sub equal to half the cone radius, 1/4 the diameter. Note that this isn't 1/4 the driver size, we're talking about Sd.

              For the RSS315HF-8, Sd is 507 sq. cm., the radius a little under 13 cm. and clearance is half that, or ~2.5" of free space between floor and sub baffle or you've violated assumptions of the simulator. It's not that the sub won't make sound, it just won't be what you expected, possibly better but potentially worse.

              Adding it up...
              2.5" of clearance in front of drivers
              6" of driver depth
              1.5" of building material (assume driver is flush mounted in front)
              And the answer is... 10" with zero driver clearance in the box for driver venting.

              Up-firing is also doable, and could potentially yield some interesting sensations for anyone sitting there. It would also allow the futon cushion to become a huge bass trap if it's air-permeable...

              If you can place it vertically, the clearance issue disappears and you can add enough depth for the driver to breath, not unlike the Boogieman!

              I should note there is a sub design that fits under your futon, only 8.25" tall, with no clearance issues... and it's a horn! I've built two...
              http://www.avsforum.com/t/1238398/re...ped-horn/0_100
              Drivers are on sale
              http://www.diycable.com/main/product...roducts_id=538
              And flat-packs are a steal; you won't save doing it yourself (I tried).
              http://www.diysoundgroup.com/flat-pa...narchy-th.html

              ... but it's still $300 for the pair, plus BASH 300, which won't compete price-wise with the SD315A-88 (Also pulls 10mm off the driver depth, but increases Sd and so skirt clearance compared with RSS315)

              Have fun,
              Frank
              Last edited by fbov; 06-14-2012, 05:58 PM. Reason: Corrections in text underlined; got math right then explained it worng.

              Comment


              • #8
                Re: Low Profile Subwoofer

                Originally posted by mdocod View Post
                ~5ft^3 looks great for this. I'd suggest for your port, to just pick up one of these: http://www.parts-express.com/pe/show...number=268-352

                Use the full 17" included length, that will get you tuned in the ~20hz range. Good for movies or music that way. Peak particle velocity will occur @13hz and not be an issue. Driver excursion will hit 7mm @~125W input around 30-40hz. Translation: 300W bash is a tad overkill, but there aren't many other logical choices. I'd say consider the SPA250, save $50 or so that way (based on current pricing).

                I'm confused about where you're going to mount drivers on this thing... It's going under the futon?
                I agree with the flared port idea. The flares will greatly reduce the "chuffing" noise. I would also vote for the SPA250 - will be a good match power-wise for the project, saves you some money, and (IMO) sounds better than the BASH.

                I presume you'd do the subs facing up into the cushion/frame of the futon. Should work just fine. Over time, there will be some cone sag and consequently a little output capability loss, but (IMO) not worth getting undies in a twist about it. The Dayton DVC paper cones are great bang-for-buck drivers.

                I would recommend powering both coils in parallel on each driver ("4 ohms" total per diver) and running the two drivers in series for a total of "8 ohms" load to the amp. The amp will thank you for it... and distortion will be about half as much as a 4ohm load out of the amp (shorting an unpowered coil on each driver for 8ohms per driver, and paralleling the two drivers for a total of 4ohm load on the amp). These two driver power configuration scenarios produce the same SPL: 89.6dB @ 2.83V/m... but are two very different loads on the amp for the same output drive voltage. Less load (higher ohms) = less distortion. Bonus Since the SPA250 is clearly not even close to a "load invariant" design (10x the THD for 8ohm and 4ohm when the 4ohm power rating isn't even double the 8ohm), distortion is probably even better than half for the 4ohm load under moderate power conditions. For even better performance, the Keiga 5150 would suit you well (much lower distortion). I find the Keiga amps to sound better as well, having a "tighter, more controlled" sound than the PE amps... but, the Keiga 5150 is $50 more than the SPA250 - back to the price price of the BASH but it sounds quite a bit better (IMO).

                I've rambled long enough. HTH...
                SEC DIY 2014 Speaker Show is on! *November 8th*
                Wanna win a set of Newform Research R30 ribbons?!?!
                SEC DIY 2014 Thread

                SEC DIY 2012 Speaker Show
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                Comment


                • #9
                  Re: Low Profile Subwoofer

                  What about front firing with 4-6 TangBand W5-1138SMF (the new ferrite version)?

                  Comment


                  • #10
                    Re: Low Profile Subwoofer

                    My intention is to have it firing upwards, towards the futon cushion. I think dropping in a flared port would be a pretty easy modification. I'll drop it in now into the cool picture. lol.

                    Thanks everyone for your advice so far.

                    Comment


                    • #11
                      Re: Questions about Subwoofer build

                      Originally posted by fbov View Post
                      Up-firing is also doable, and could potentially yield some interesting sensations for anyone sitting there. It would also allow the futon cushion to become a huge bass trap if it's air-permeable...

                      If you can place it vertically, the clearance issue disappears and you can add enough depth for the driver to breath, not unlike the Boogieman!

                      I should note there is a sub design that fits under your futon, only 8.25" tall, with no clearance issues... and it's a horn! I've built two...
                      http://www.avsforum.com/t/1238398/re...ped-horn/0_100
                      Drivers are on sale
                      http://www.diycable.com/main/product...roducts_id=538
                      And flat-packs are a steal; you won't save doing it yourself (I tried).
                      http://www.diysoundgroup.com/flat-pa...narchy-th.html

                      Have fun,
                      Frank
                      First off, thank you for all of the input. It is greatly appreciated!
                      1. That sub you linked is pretty awesome, but I like the boogieman type design because it's pretty cool looking when someone asks "WHAT IS THIS MAKING MY **** MOVE SO MAGICALLY!?" whereas the one you linked is a nice rectangular prism.
                      2. I'm definitely looking more towards the upward firing into the futon + the ability to have it stand on its side. I think it's a very versatile design option when moving furniture around.

                      What about front firing with 4-6 TangBand W5-1138SMF (the new ferrite version)?
                      Although I know it to be fictitious/flawed, I'm a fan of the 'bigger is better' mentality (although 15 is my limit, no bigger for me) when it comes to subwoofers. I've actually got a powered 12" vented woofer already, but it's bulky and the lady -hates- it. It's also not that great and I get a lot of port noise when it's turned up and it's sluggish etc. etc..

                      Comment


                      • #12
                        Re: Low Profile Subwoofer

                        Originally posted by scottq View Post
                        I agree with the flared port idea. The flares will greatly reduce the "chuffing" noise. I would also vote for the SPA250 - will be a good match power-wise for the project, saves you some money, and (IMO) sounds better than the BASH.

                        I presume you'd do the subs facing up into the cushion/frame of the futon. Should work just fine. Over time, there will be some cone sag and consequently a little output capability loss, but (IMO) not worth getting undies in a twist about it. The Dayton DVC paper cones are great bang-for-buck drivers.

                        I would recommend powering both coils in parallel on each driver ("4 ohms" total per diver) and running the two drivers in series for a total of "8 ohms" load to the amp. The amp will thank you for it... and distortion will be about half as much as a 4ohm load out of the amp (shorting an unpowered coil on each driver for 8ohms per driver, and paralleling the two drivers for a total of 4ohm load on the amp). These two driver power configuration scenarios produce the same SPL: 89.6dB @ 2.83V/m... but are two very different loads on the amp for the same output drive voltage. Less load (higher ohms) = less distortion. Bonus Since the SPA250 is clearly not even close to a "load invariant" design (10x the THD for 8ohm and 4ohm when the 4ohm power rating isn't even double the 8ohm), distortion is probably even better than half for the 4ohm load under moderate power conditions. For even better performance, the Keiga 5150 would suit you well (much lower distortion). I find the Keiga amps to sound better as well, having a "tighter, more controlled" sound than the PE amps... but, the Keiga 5150 is $50 more than the SPA250 - back to the price price of the BASH but it sounds quite a bit better (IMO).

                        I've rambled long enough. HTH...
                        Thank you for all of that!

                        I think you're right about the wiring, I was wondering if that would be a better move, but with the limited headroom on the dayton amp I was thinking that it would be better to have the added 50w of the bash system, that way if I have a higher ohm load as you describe I wouldn't run out of wattage to push my less distorted sound.

                        I'm still not sold on either amp yet, but that's another (-) for the bash 300w.

                        Comment


                        • #13
                          Re: Low Profile Subwoofer

                          Originally posted by Adam_G View Post
                          ...I'm still not sold on either amp yet, but that's another (-) for the bash 300w.
                          Be sure to check power ratings. PE's BASH 300 is a 150W amp at 8 ohms. It's one of the few that's not current limited into 4 ohms. What matters is the power rating at the expected load vs. the driver/box excursion capabilities. In general, you want more amp than the speakers can take, but not by a lot...

                          For example, my Anarchy horns are coil excursion limited at 75W, but have lots of extra travel (Xmech > Xmax) so the driver's safe with extra power. They're 8 ohm drivers, so a single sub gets 150W, but when I plug in the second, the pair get 300W.

                          Have fun,
                          Frank

                          Comment


                          • #14
                            Re: Questions about Subwoofer build

                            Originally posted by fbov View Post
                            The Boogieman has feet on the driver side, but they do nothing but protect the drivers. It's not a down-firing design, but rather a hide-behind-the-couch design.
                            Have fun,
                            Frank
                            Actually- I think Darren used it downfiring, or he would not have placed feet on it at all. In terms of heatsinking I know it goes against the typical method, but I asked him about it once and he said it didn't seem to matter in this case.

                            Boogieman coming from under the bed as the story goes, and hence the name.

                            Later,
                            Wolf
                            "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
                            "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
                            "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
                            "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

                            *InDIYana event website*

                            Photobucket pages:
                            https://app.photobucket.com/u/wolf_teeth_speaker

                            My blog/writeups/thoughts here at PE:
                            http://techtalk.parts-express.com/blog.php?u=4102

                            Comment


                            • #15
                              Re: Low Profile Subwoofer

                              Here's an idea for the amps:

                              Rather than having a built-in amp, I have a TOA 240w amp sitting around (got it from auction for $15, along with it's little brother the 120w... yeah). I just remembered that this brick is sitting in the corner doing nothing. Would that be a viable powering option? It's a full-range amp w/ selectable subsonic filter, I don't know how I would wire it into my sub-out on my receiver though.

                              Comment

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