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Making a subwoofer from strange box. Does shape matter? What size driver?

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Making a subwoofer from strange box. Does shape matter? What size driver?

Postby DC-Choppah » Tue Oct 08, 2019 4:02 am

I want to turn a structural box into a subwoofer to conceal the subwoofer visualy, but have it sound correct too.

https://drive.google.com/open?id=1QgQkg ... lfw3zMX8Gn
https://drive.google.com/open?id=1Gvlih ... tMic_Ws5Ed
https://drive.google.com/open?id=1ADAJE ... o37NErJRQ4
https://drive.google.com/open?id=1pUc2u ... axug9bN9Dn

The box is internally about 21" x 21" x 7" with one of the corners lopped off. It is made from 3/4" plywood. It fits in a corner and will have a large plant on it. The box was originally designed to hold a corner aquarium and is very strong and sturdy.

So I want to turn this into a down firing powered subwoofer and mate it too some nice Boston Acoustic speakers that are in that room.

I plan to increase the height of the feet all around, and add a bottom that will mount the down facing driver.

I estimate the volume to be : 21"x21"x7" - (7"x7"x7")/2 = 1.75'x1.75'x.58' - (.58'x.58'x.58')/2 = 1.8 - .2 (ft^3)= 1.6 ft^3

There is 15.5" between the internal baffles, so I could do up to a 15" driver.


So my questions are:

What size driver to use with this 1.6 ft^3 box?

Does the weird shape matter?
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Re: Making a subwoofer from strange box. Does shape matter? What size driver?

Postby ef37a » Tue Oct 08, 2019 9:33 am

The "weird shape" is actually an advantage, helps reduce standing waves but you are wasting some internal volume. Jig sawing 50% of the partions out will not reduce rigidity but will increase volume. Fill the voids with absorbent.

I would say 15" is way too big in just 1.6cuft but the first things you need to determine are the crossover frequency and the sort of SPLs you want from the main speakers.

If you want domestic levels, 80-90dB then I would think a good quality, low resonance 8" unit would suffice.

What will you be driving it with?

Dave.
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Re: Making a subwoofer from strange box. Does shape matter? What size driver?

Postby DC-Choppah » Tue Oct 08, 2019 10:49 pm

I have one of these: http://www.daytonaudio.com/index.php/su ... oofer.html

and would like to try to move the amp and speaker driver to my box.

This is a 12" driver? I can get smaller ones, but would like to try to use this 12" if that will work?

I have some fiberglass (rockwool) to stuff into the box.

The amp in that room only has a stereo speaker output so I am going to use the speaker connections from the amp to the subwoofer, and take the high pass signal to the Boston Acoustic speakers.
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Re: Making a subwoofer from strange box. Does shape matter? What size driver?

Postby DC-Choppah » Tue Oct 08, 2019 10:51 pm

ef37a wrote:The "weird shape" is actually an advantage, helps reduce standing waves but you are wasting some internal volume. Jig sawing 50% of the partions out will not reduce rigidity but will increase volume. Fill the voids with absorbent.
Dave.

OK. Going to take a saw to those internal partitions and fill those side voids with the rockwool. Thanks for that Dave.
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Re: Making a subwoofer from strange box. Does shape matter? What size driver?

Postby ef37a » Wed Oct 09, 2019 9:14 am

DC-Choppah wrote:
ef37a wrote:The "weird shape" is actually an advantage, helps reduce standing waves but you are wasting some internal volume. Jig sawing 50% of the partions out will not reduce rigidity but will increase volume. Fill the voids with absorbent.
Dave.

OK. Going to take a saw to those internal partitions and fill those side voids with the rockwool. Thanks for that Dave.

Not sure rockwool s the right stuf inside speakers? Way back in the day the usual stuffing was Bonded Acetate Fibre (still got some in the loft!).

Since you have the twelve, try it. You are never going to get a super flat, integrated system with ad hoc components but it could end up being quite pleasant to listen to. If you can change/sweep the LF crossover point that would help "tune" the results.

Dave.
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Re: Making a subwoofer from strange box. Does shape matter? What size driver?

Postby DC-Choppah » Sun Oct 13, 2019 8:22 pm

Subwoofer Corner Plant Stand

Sounds good!

Everybody’s happy now

https://drive.google.com/file/d/1-wSq54 ... p=drivesdk

https://drive.google.com/file/d/1AZcnC8 ... p=drivesdk

I used the black foam that was in the Dayton subwoofer.

I am going to use that Mike Senior File of swept bass tones and my SPL meter to try and set this.
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