Sofa Subwoofer

[kctess5]

Alright heres a bunch of info I made today. Included is the input parameters I designed off of, the projected response, a screenshot of the spreadsheet, and the dimensioned drawing I took all of the info off of.

Note that all of the line lengths on the dimensioned drawing must be multiplied by 4 (because the scale of the drawing was 1/4) but I have done this for you in the spreadsheets so you shouldn't have to worry about it at all

Most of the corners have a 4in radius piece of sonotube on them to keep the area more constant and this is factored into the numbers

The drivers are offset about 7 inches (to the center, i.e. one inch from edge) from the beginning of the horn

Let me know if anything else would be helpful. Thanks again!

[kctess5]

Oh yeah I forgot to mention that the CSA/Sd ratio is for two woofers, as in CSA/(2*Sd), because I have two. Just trying to avoid confusion

[bjorno]

Originally Posted by kctess5

Oh yeah I forgot to mention that the CSA/Sd ratio is for two woofers, as in CSA/(2*Sd), because I have two. Just trying to avoid confusion

Great information! Now it's easy to plot/find out an MJK optimized stuffing scheme. It will take some time...Be patient!

b

[bjorno]

Originally Posted by bjorno

Great information! Now it's easy to plot/find out an MJK optimized stuffing scheme. It will take some time...Be patient!

b

Here is a preliminary result. It looks like it would be a good idea to invest in ~1 lb(more is IMO not needed) of commercial loudspeaker damping material besides to use cross bracings (like 12 or more dowels) at least for the five first of the sections seen in your drawing where also would benefit from felt of wool glued on the walls.

I need more time(1-2 days) before I have time to post a more detailed result..

b

[bjorno]

Originally Posted by bjorno

Here is a preliminary result. It looks like it would be a good idea to invest in ~1 lb(more is IMO not needed) of commercial loudspeaker damping material besides to use cross bracings (like 12 or more dowels) at least for the five first of the sections seen in your drawing where also would benefit from felt of wool glued on the walls.

I need more time(1-2 days) before I have time to post a more detailed result..

b

Late edit: 1lb of stuffing should read 2 lb's

b

[kctess5]

Originally Posted by bjorno

Late edit: 1lb of stuffing should read 2 lb's

b

Would soundproofing material like this work? I have TONS of it. I hate to pay $20 for stuffing material when the whole project cost me at this point like $130 and I already have that. If not what about polyester batting like in quilts, I can get that cheaper.

Here is a preliminary result. It looks like it would be a good idea to invest in ~1 lb(more is IMO not needed) of commercial loudspeaker damping material besides to use cross bracings (like 12 or more dowels) at least for the five first of the sections seen in your drawing where also would benefit from felt of wool glued on the walls.

What about denim? I've heard of people using that before and I now the local fabric store has it pretty cheap

Thank you! Take however long you need

[bjorno]

Would soundproofing material like this work? I have TONS of it. I hate to pay $20 for stuffing material when the whole project cost me at this point like $130 and I already have that. If not what about polyester batting like in quilts, I can get that cheaper.

Yes it should be good for attenuating wall reflexes but not as good as thick felt that also work like a energy sink for wood vibrations.

Quilt battings of polyester is a perfect material to substitute 'speaker polyester fibers' as long as the weight/ density is held for the section damping I will suggest later.
I guess a combination of denim+your egg crate foam would work well too.

What about denim? I've heard of people using that before and I now the local fabric store has it pretty cheap

Denim is perfect too: I've tested using two layers(~3/8") spray-glued to the walls in a 50 L TL made of 1/4 inch wood that had a XO at~1 .5kHz, this came out with very good result.

b

[bjorno]

Bump...

I'm still fiddling with the stuffing parameters until tomorrow.

b

[kctess5]

Sounds perfect. I've been using it as is for the last few days in my system and I can already tell this thing is insane. Even with the top unsealed and no stuffing it sound leaps and bounds better than my old sub. I can get some serious wall shaking bass with this thing.

I get a bunch of room gain when I'm sitting on top of the thing in the corner. It sounds almost 50% louder then in the rest of the room. Also I get noticeable room pressurization with all the doors and windows closed.

I'm powering it off of a 120w plate amp and theres no way I will need that much power. At levels where I'm worried about hearing damage after long term exposure I am still FAR from maxing out the amp, same goes for the woofer excursion.

My only real concern is the neighbors

[bjorno]

Originally Posted by kctess5

Sounds perfect. I've been using it as is for the last few days in my system and I can already tell this thing is insane. Even with the top unsealed and no stuffing it sound leaps and bounds better than my old sub. I can get some serious wall shaking bass with this thing.

I get a bunch of room gain when I'm sitting on top of the thing in the corner. It sounds almost 50% louder then in the rest of the room. Also I get noticeable room pressurization with all the doors and windows closed.

I'm powering it off of a 120w plate amp and theres no way I will need that much power. At levels where I'm worried about hearing damage after long term exposure I am still FAR from maxing out the amp, same goes for the woofer excursion.

My only real concern is the neighbors

Hi,

Your sofa sub should be easy to stuff if following this final scheme with minimized use of damping materials but cross-bracing and coverage of internal walls is still necessary if to peak the performance of this design :Part 1

b

PS: I will post Part 2 tomorrow = all plots.