Ottoman-based Subwoofer project
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 15th June 2008, 02:52 AM #1 p0lar   diyAudio Member   Join Date: May 2008 Ottoman-based Subwoofer project Hello all! I'm new to the DIY community, but want to try my hand at a few things and figured a subwoofer was a good place to start since I had some interesting demands from my home theater and current living conditions. I don't have much space in my loft, nor do I really want to audibly shake down the neighbors, so I've been considering building a subwoofer into my leather ottoman. The first step I took was to turn it over and see what kind of space was available for an enclosure. I had to cut off the nylon cloth backing, and discovered there was a structural support that divided the unit in half. I have essentially two chambers I can work with; one which is 14"x23"x6.5" and another which is 15"x23"x6.5". The main problem is that I can't extend more than about 8.5" to the floor, so I figure 6.5" is about as low as I want to go, which should give me approximately 2" of clearance between the driver/port and the floor. It's not a lot, but it makes the calculations look close. I'd like to use a (Bash 300 Watt Subwoofer Amplifier from PE and have to source a low-profile driver that will fit the space constraints. I'd like to be able to achieve at least 30 Hz on the lower extension, but realize this may be a difficult task given the space constraints. On the larger of the two chambers, building an enclosure from 0.75" MDF, I can roughly achieve 0.84 ft.^3. The BASH amp consumes approximately 0.06 ft.^3, leaving me with about 0.78 ft.^3 net volume. I've sourced a particular driver from Pioneer that was originally designed for car audio, but that has a shallow mounting depth, the [URL=http://www.pioneerelectronics.com/PUSA/Products/CarAudioVideo/Subwoofers/Shallow/TS-SW3041D[/URL]. Pioneer's spec'd box for a small truck or car is approximately 0.7 ft.^3 by my calculations though it's not ported. I can't find any T/S parameters on this driver, but this spec document doesn't show very promising results around the 30Hz range, either in a ported or sealed enclosure @ 0.8 ft.^3. Might anyone have any other driver suggestions that fit the bill? I'd like to stay with a single 12" if possible, and I'm sure with the right driver, 300 watts into 4 ohms is more than plenty, at least if it's even moderately efficient. I'll post updates here as I progress, please don't hesitate to make suggestions!
 15th June 2008, 03:29 AM #2 just a guy   diyAudio Member   Join Date: May 2006 That sounds like a pleasant little foot massager with great waf. But it sounds like space is the biggest issue. It might even be difficult to add a baffle without harming the aesthetics of the outside of this piece of furniture - or are you building a box to fit inside the ottoman? Other than that, it is a fine idea, as long as you realize that subwoofers generally have to be big OR expensive if you ever want it to get reasonably loud. That's a big generalization. .78 cubes is not much for a subwoofer driver, and it will have to be either a very small driver, or have low vas and low qts (and probably still have to be quite small sd) which = expensive to work in such a small space. And don't forget to subract the volume of the driver (and port if applicable) from the net volume. In the end it might be a whole lot easier, and probably cheaper and louder if you make a small coffee table or end table, or even build the thing under the couch.
 15th June 2008, 09:25 AM #3 hm   diyAudio Member     Join Date: Feb 2004 Location: near Hamburg Germany Ottomane, Armchair Hello, or a corner Horn as writing table, or the BASSEL an armchair as a horn, or a few studies double seater, look my hp the SUBLIE is something like your ottomane: big drivers have the problem of inertia, specially by low level, small driver in a horn are better, my favorit for your room is the KORNETT, no sub needed. __________________ http://www.hm-moreart.de
p0lar
diyAudio Member

Join Date: May 2008
Quote:
 Originally posted by just a guy That sounds like a pleasant little foot massager with great waf. But it sounds like space is the biggest issue. It might even be difficult to add a baffle without harming the aesthetics of the outside of this piece of furniture - or are you building a box to fit inside the ottoman? Other than that, it is a fine idea, as long as you realize that subwoofers generally have to be big OR expensive if you ever want it to get reasonably loud. That's a big generalization. .78 cubes is not much for a subwoofer driver, and it will have to be either a very small driver, or have low vas and low qts (and probably still have to be quite small sd) which = expensive to work in such a small space. And don't forget to subract the volume of the driver (and port if applicable) from the net volume. In the end it might be a whole lot easier, and probably cheaper and louder if you make a small coffee table or end table, or even build the thing under the couch.
I considered the sofas, but they've the same clearance issues as the ottoman (from the same manufacturer). WAF is important, but space considerations are my biggest concern at the moment and I don't even have room for a coffee table though an end table MIGHT be an option -- I'll poll the peanut gallery later to see what she thinks. The enclosure will actually be tucked up underneath the ottoman -- I'll try to attach a photo to illustrate what I have to work with. The biggest problem I have with that Pioneer driver is that I can't find any T/S parameters on it to make the necessary calculations. I don't need anything that will hammer the room since it's a loft at approximately 700 sq.ft., and with hardwood flooring throughout with 10' flat concrete ceilings. Acoustically, it could be very boomy if not for some dividers and furniture I've tried to place strategically.

Pioneer actually calls for a 3" x 8" port (0.033 ft.^3), but I can't fit 8" anywhere in that enclosure to make it downfiring unless I build a right-angled port. Even then, I'm not sure what that will do to the air velocity and/or cause it to resonate off-axis (if my simple studying is correct).

This may be a trial & error affair in futility, but to compliment the sub, I'm also debating adding a few Auro pro bass shakers to the sofas to emphasize the lacklustre subsonic performance from such a small enclosure.

p0lar
diyAudio Member

Join Date: May 2008
Re: Ottomane, Armchair

Quote:
 Originally posted by hm Hello, or a corner Horn as writing table, or the BASSEL an armchair as a horn, or a few studies double seater, look my hp the SUBLIE is something like your ottomane: big drivers have the problem of inertia, specially by low level, small driver in a horn are better, my favorit for your room is the KORNETT, no sub needed.
Wow, that is quite intricate! Though it is a fascinating design, I am quite certain it is well beyond my crafty capabilities at the moment.

 16th June 2008, 07:25 AM #6 Bjohannesen   diyAudio Member   Join Date: Jan 2005 Location: Copenhagen This might be an idea ? http://www.audioxpress.com/magsdirx/...nnesen2835.pdf My wife likes it Bjorn Wonderful Copenhagen
 25th June 2008, 08:09 PM #7 The golden mean   diyAudio Member   Join Date: Aug 2004 Location: Uppsala,Sweden There is a "flat-pak" sub described in the German Klang+Ton magazineīs current issue June/Juli. In fact there are two variants. One uses a closed box while the other and slightly bigger one is a Transmission Line one. They use a Monacor car woofer to keep the subs thin; only 12 cm. The woofer is called Pulsar 10 (Monacor) and has a "brother" in the Pulsar 12. The website for the magazine is slow so there isnīt any information about the issue I now hold in my hand. But hereīs a picture anyhow. Sorry, you have to click on the second link from above=Flachsub GES und TML http://www.lautsprechershop.de/hifi/...i/zeit_kut.htm __________________ Without wonderment,no life.

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