Sofa Subwoofer

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I have been thinking about making a budget transmission line subwoofer for my room but I don't have a bunch of room for a 8 foot long 12" pipe and my mom may commit suicide if I even suggested it so I've been thinking of ways to hide a obnoxiously massive TL box. After a bit of pondering I came up with an interesting idea...

What if I built the thing sideways with the port and woofers on front, put a back on it, made it look all nice and stuck some cushions on it. I eventually came up with a few sketches with potential designs and then today I made the most promising one on Autodesk Inventor to see how this behemoth would would disappear. The design was based off of this conveniently well sized diy couch.

I wan't to use a push pull configuration with both drivers facing the same way but out of phase (i.e. one is mounted backwards) to help cancel out vibrations and bring down distortion, getting two woofers in that configuration and the port on front was a bit tricky, but I prevailed.

Since I've gotten home and seen my actual size limitations I've made a few small changes. First of all, the horizontal width of the line is decreased to 10" giving a total width of 43.75" which will fit into the space. To account for the decreased size the height has also been changed to 15" internal. The line length is 10' for a tuning of 28.1Hz.

Once this is done I can use it as my listening chair/ hulu viewing center. It will bring the thunder.

As I said I'm on a budget so I plan to use these Daytons and either sell my current subwoofer (for about $60) and buy an amp with that or just take its plate amp (120w, its a Sony SA WM40) and drop it in. I already have a cushion that will work so I would estimate a total cost of about $170 for me.

2 sheets 3/4" plywood/MDF = $70
2 woofers = $80
random hardware = $20

I'm very resourceful so that low price tag isn't too tall of an order for me :D

Obviously the rendering isn't totally accurate as far as finishing goes. There will grill cloth in front of the whole front part with the drivers and port (to keep my cat from crawling in :eek:) and the cushions will most likely look almost nothing like that.

Now comes the hard part, telling my mom I want to build a 12 cubic foot, 10 foot long transmission line, but not to worry because it will be utterly invisible and I wont break the windows or debone stray chickens with it.

I do believe that I have made the elephant in the room disappear :eek:

Has anyone seen anything similar to this? I sure haven't...
 

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Do you want to use this as a subwoofer?
What SPL output do you want?
What frequency range do you want to achieve?

I suspect the DC300-8 12" Classic Woofer will be limited because of Xmax In a TL.

Are you set on a TL, with that much volume you could make one heck of a BR box or a T-TQWP.
 
I would like it to be flat as possible down to around 20Hz. Infrasonic isn't as important to me but considering that I'll be sitting on top of it I should get a good effect from explosions or whatever. It won't be asked to play too high either, probably around 80 Hz or so.

I don't need massive SPL, I figure I should be able to get up to about 114 db with a 120w amp which should be enough for any transients I should have.

I'm trying to avoid a bass reflex for better transient response, clarity, and so that I don't have a great sounding range of 5Hz with everything else being blah.

I've heard some pretty good stuff about this kind of TL sub

Oh yeah and about the limited xmax I was thinking that having two would reduce the necessary excursion for each driver at the same levels, similar to what I did with my line arrays
 
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I did some more parts express digging and found these

T3 Audio T200-12S4 12" 200 Watt Subwoofer 4 Ohm 269-086

Specifications: *Power handling: 200 watts RMS/400 watts peak *VCdia: 1.75" *Le: 1.81 mH *Impedance: 4 ohms *Re: 3.89 ohms *Frequency response: 30-1,500 Hz *Fs: 32 Hz *SPL: 87.58 dB 1W/1m *Vas: 1.76 cu. ft. *Qms: 8.54 *Qes: 0.74 *Qts: 0.66 *Xmax: 12.7 mm *Dimensions: Outside diameter: 12.30", Cutout diameter: 11.20", Depth: 5".


The higher qts is good, better Xmax too. The problems I see immediately are the low Vas and high Fs. Which would be better overall? Keeping in mind that I will be driving them at around 120w total unless I buy a new amp which I don't want to do
 
It certainly seems to be a good use of space and a creative way to mask a giant line. My only concern is that my t-line sub (uses dual 8") has much more real bass presence when you are 8 or more feet from the enclosure. It sounds even better at 20 feet and beyond. while standing or sitting up close it is somewhat boomy with little real body. It could simply be my room. its 25'x50'x11' with brick walls (old factory loft). While I'm sure the bass won't go unnoticed while sitting on it, but your poor mother in the next room might be getting the brutal stuff. Keep us posted on your progress. I like the idea.
 
That sounds like it may be either room modes or maybe if yours is a straight t line with the opening far away from the woofer it could be some sort of near field-far field sort of thing, like how line arrays get louder as you move farther and then reach a max then decrease at 3 db/meter until you get to the far field you know, just a guess.

I'll keep that in mind though and see how it sounds in my significantly smaller room.

but your poor mother in the next room might be getting the brutal stuff

Haha I'll make sure to avoid that, she REALLY dislikes bass so I usually turn my sub way down when shes home and crank it a bit when shes gone.

I got permission to do the build last night so the hard part is over, I should make an order from parts express as soon as I sell the desktop speakers I just made. I already have a buyer so that should be in the next couple of weeks. I'll do build pics and everything, I imagine this thing will be about the same weight and size as an elephant so getting it to my room up the stairs from the garage will be a trick :eek: Ill probably build it in 3 pieces and assemble it in the room
 
Awww look at that someone beat me to it.

Thats pretty cool though, I want to get it flat to around 20-25 Hz and I'm trying to keep it a bit simple so I prefer the transmission line rather than the horn.

What drivers do you have on there?

I should be making the order in the next few days once I receive payment for the book shelf speakers I just made.

I'll make sure to document the build and post measurements and all that.
 
The room is pretty small (approx 15 by 12 I think) but the couch-woofer is going to be in a alcove of sorts. So I am expecting some room modes for sure given its close proximity to 3 walls and the main speakers pointing towards it into the alcove.

On the picture you can see the audio Flexy stand and speakers on either side of it pointing towards the couch. The two walls on either side of the couch (not including the one shared by the closet) have windows on them. When I am using the sound system I lower the curtains to minimize reflections from them and I plan to put some sound proofing on whatever bare wall is available to absorb some more.

I get quite a lot of room gain for my subwoofer in this configuration which is to be expected.

I don't mind this too much to be honest because I can just turn the sub down unless I'm listening to bass heavy music and I can pump it.

The room is pretty sealed when the door is open and windows are closed, I've noticed that if I close everything up the bass is quite a lot louder, presumably because its able to pressurize the room much more effectively
 

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I did some more parts express digging and found these

T3 Audio T200-12S4 12" 200 Watt Subwoofer 4 Ohm 269-086

Specifications: *Power handling: 200 watts RMS/400 watts peak *VCdia: 1.75" *Le: 1.81 mH *Impedance: 4 ohms *Re: 3.89 ohms *Frequency response: 30-1,500 Hz *Fs: 32 Hz *SPL: 87.58 dB 1W/1m *Vas: 1.76 cu. ft. *Qms: 8.54 *Qes: 0.74 *Qts: 0.66 *Xmax: 12.7 mm *Dimensions: Outside diameter: 12.30", Cutout diameter: 11.20", Depth: 5".


The higher qts is good, better Xmax too. The problems I see immediately are the low Vas and high Fs. Which would be better overall? Keeping in mind that I will be driving them at around 120w total unless I buy a new amp which I don't want to do

The Xmax and Pe ratings of the driver in question here are highly suspect. I would avoid these drivers if you want simulation to closely resemble reality.
 
The Xmax and Pe ratings of the driver in question here are highly suspect. I would avoid these drivers if you want simulation to closely resemble reality.

Yeah I'm going with the daytons. I tend to trust Dayton a bit more than T3. Plus I've heard some drivers that looked almost identical to those and they were really terrible, though that is probably most likely a cabinet design problem than anything.

I'm ordering the drivers soon (wednesday :xfingers:) along with some other stuff for my next bookshelf speakers (honestly this is a disease) and I should start the build the weekend after next, and hopefully finish by the weekend after that because I'll have 4 days off school to fool around in our garage with the saw.

Pictures should be coming soon. I love how my ridiculous idea of hiding a 10 cubic foot subwoofer masquerading as a couch in my relatively tiny room went from being just that to a legit plan in about a week.
 
I wouldn't personally use the dayton classic woofers for the project either. If you're going to go through all the trouble to build a piece of furniture, I would want to at least put drivers in it that are going to work as hard as you will work to build the box.

On the other hand, If keeping costs low is so important, 3-4 of these: 10" Ribbed Paper Cone Woofer Speaker 299-284 instead of 2 of the daytons. You'll save about $60. You mentioned that your box would benefit from a less dampened driver, and these fit that bill.

Just an idea :)
 
What would you use then? As long as the combined cost is below around 120 it should be ok. I know what you mean about putting drivers in that match the amount of work though

Other than cost I can't really see the benefit of using those drivers you mentioned. The Vas is huge at over 6 cubic feet and with 4 of them that would become an issue in this enclosure I think. Also the Xmax is less than the daytons, the Q is similar, and the Fs is higher so I wouldn't get bass as low.

Whats the issue with using the Daytons other than the excursion though? Considering that I will only be driving then at 120W as opposed to their max of 230W I don't think I will be maxing out the excursion as it is. I may some day upgrade amps of course but not for a long while

In general I like the idea of using even numbers of drivers so that I can cancel out vibrations and make any non linear response sort of deals in one direction even.
 

Wow thank you!

This is great, though I must admit I am a bit confused by what all that means.

Sorry theres quite a few abbreviations that I'm not sure what they pertain to (i.e. S1, S2..., Ang, Eg, Rg, Fta the list goes on) Also the picture of the horn is tapered but I'm not sure if that is just a representation and whats modeled is actually a straight horn.

Is that modeled after my enclosure or is it the optimal enclosure?

Those Daytons seem to perform better than the other ones, and the Xmax of the daytons is not exceeded until below 18 Hz which I would contend is good.

It looks like I could crossover at around 80 Hz to my main speakers which is right around when they roll off which is good.

If these are in fact modeled after my design that would make me really happy because I predicted something pretty similar with the alignment tables and some guestimating
 
.. Also the picture of the horn is tapered but I'm not sure if that is just a representation and whats modeled is actually a straight horn..

Hi kctess5,

The single driver enclosures should be folded once, the dual driver twice.

Is that modeled after my enclosure or is it the optimal enclosure?

No but I'm sure both the single driver suggestions would easily fit your sofa.

Those Daytons seem to perform better than the other ones, and the Xmax of the daytons is not exceeded until below 18 Hz which I would contend is good.

I'm in agreement!

It looks like I could crossover at around 80 Hz to my main speakers which is right around when they roll off which is good.

Yes, IME you will not notice the bass emitting when your sitting on your sofa but instead from your main speakers wherever they are located if using a 24 dB LPF.

[/QUOTIf these are in fact modeled after my design that would make me really happy because I predicted something pretty similar with the alignment tables and some guestimating

I also suggest you to place the terminating port facing the rear side of the sofa,that will be near a corner and the enclosure will be shaped like an L with a constant rectangular CSA = (2* wood +driver frame width) * X; X = (S1/dfw+S4/dfw+3*wood) where S1 is the larger area and S4 the terminating area.

The total internal length is 290cm that when folded once will be just 145 cm=
~57.087"+2x wood, thus the gross volume is~ CSA*L.

The folding expansion is Par = parabolic opposed to conical as shown in the HR program.

You can when *Exporting* the CSA from HR choose an arbitrarily section length to reflect your intentions.

You really need to consult the HR built in Help facility.

b:)
 
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