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Old 25th January 2012, 10:54 PM   #1
kctess5 is offline kctess5  United States
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Default Sofa Subwoofer

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

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 ) 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

Has anyone seen anything similar to this? I sure haven't...
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File Type: jpg sub.jpg (113.7 KB, 872 views)

Last edited by kctess5; 25th January 2012 at 10:56 PM.
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Old 25th January 2012, 11:23 PM   #2
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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.
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Old 25th January 2012, 11:56 PM   #3
kctess5 is offline kctess5  United States
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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

Last edited by kctess5; 25th January 2012 at 11:59 PM.
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Old 26th January 2012, 12:41 AM   #4
kctess5 is offline kctess5  United States
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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
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Old 26th January 2012, 02:46 PM   #5
johnr66 is offline johnr66  United States
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Look at the proportions of an ordinary couch. This thing would be hell to sit on or you have very long legs!
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Old 26th January 2012, 03:53 PM   #6
kctess5 is offline kctess5  United States
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Haha while I'm sure that mdf is baby soft I generally prefer to use some cushions.

It's the same as a few other couches we have
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Old 26th January 2012, 06:56 PM   #7
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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.
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Old 26th January 2012, 07:11 PM   #8
kctess5 is offline kctess5  United States
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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.

Quote:
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 Ill probably build it in 3 pieces and assemble it in the room
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Old 28th January 2012, 06:27 PM   #9
hm is offline hm  Europe
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Default bass chair

hello kctess5,
nice try, make measurements if possible.

I made a few studies about bass horns:
studien bass
subsel

i realised the Bassel
Bassel
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File Type: jpg Bassel-Sessel1.jpg (42.9 KB, 718 views)
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Old 28th January 2012, 10:58 PM   #10
kctess5 is offline kctess5  United States
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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.
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