two sd315-88 in a sealed box

arjen · 14th September 2010, 10:15 AM

I want to build a smallish sub using two sd315-88 in a sealed box. It will be driven by a 2x100Watt amp (fed by the same -mono- signal of course). I plan to use Rod Elliots controller to boost the lower octave. I play at relative low volumes so the sd315's should be able to handle it.
Now I have a couple of questions.

The drivers are dual coils. So I could parallel the coils and have one amp channel drive one unit. Or I could parallel coil 1 of both speakers and coil 2 of both speakers and have the amp drive two times half of both speakers. In both cases the amp will see an impedance of 4 Ohm per channel, but are there other differences to consider?

When I put the TS parameters in winisd I get a optimum volume of approx. 74 liters. But if I lower the volume the difference in response is much smaller than I expected. Cutting the size in half only drops the 20 Hz level 3 dB. A small prize to pay for a much smaller (WAF!) box. Group delay and phase differ a bit for different sizes, but also not by large amounts. Are there other factor to consider?

Thanks,

Arjen

bjorno · 17th September 2010, 01:17 PM

Quote:

Originally Posted by arjen

I want to build a smallish sub using two sd315-88..
..When I put the TS parameters in winisd I get a optimum volume of approx. 74 liters. But if I lower the volume the difference in response is much smaller than I expected. Cutting the size in half only drops the 20 Hz level 3 dB. A small prize to pay for a much smaller (WAF!) box...Are there other factor to consider? ..

Hi Arjen,

Quote:

..A small prize to pay for a much smaller (WAF!) box..

IMO, A huge prize if apparent SQ is supposed to be targeted too.

b

arjen · 21st September 2010, 06:59 PM

Of course you're right, a horn will go much lower. But my living room is just too small to fit anything bigger than a 50 Liter box.
I've build a cabinet with a net volume of 46 Liters. And a bigger one (approx. 69 Liters). As soon as the amps and filter are finished I'll be able to hear the difference between the two volumes. But even if the bigger one sounds much better, I'm afraid there's just no room for it...

bjorno · 22nd September 2010, 02:11 AM

Quote:

Originally Posted by arjen

Of course you're right, a horn will go much lower. But my living room is just too small to fit anything bigger than a 50 Liter box.
I've build a cabinet with a net volume of 46 Liters. And a bigger one (approx. 69 Liters)...

But isn't the floor footprint

that counts in a smaller living room?

Have you tried to use LT?

b

arjen · 26th September 2010, 02:01 PM

Alas it's not only the floor footprint. It's the obtrusiveness that counts. Is it the first thing that you see when you enter the room.
I have build LT's, BR's, and even a horn in the past but that was then and this is now. This is actually the first sealed box I ever build, so it's also a learning experience.

Thanks,

Arjen

14th September 2010, 10:15 AM	#1
arjen diyAudio Member Join Date: Jul 2007	two sd315-88 in a sealed box I want to build a smallish sub using two sd315-88 in a sealed box. It will be driven by a 2x100Watt amp (fed by the same -mono- signal of course). I plan to use Rod Elliots controller to boost the lower octave. I play at relative low volumes so the sd315's should be able to handle it. Now I have a couple of questions. The drivers are dual coils. So I could parallel the coils and have one amp channel drive one unit. Or I could parallel coil 1 of both speakers and coil 2 of both speakers and have the amp drive two times half of both speakers. In both cases the amp will see an impedance of 4 Ohm per channel, but are there other differences to consider? When I put the TS parameters in winisd I get a optimum volume of approx. 74 liters. But if I lower the volume the difference in response is much smaller than I expected. Cutting the size in half only drops the 20 Hz level 3 dB. A small prize to pay for a much smaller (WAF!) box. Group delay and phase differ a bit for different sizes, but also not by large amounts. Are there other factor to consider? Thanks, Arjen

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21st September 2010, 06:59 PM	#3
arjen diyAudio Member Join Date: Jul 2007	Of course you're right, a horn will go much lower. But my living room is just too small to fit anything bigger than a 50 Liter box. I've build a cabinet with a net volume of 46 Liters. And a bigger one (approx. 69 Liters). As soon as the amps and filter are finished I'll be able to hear the difference between the two volumes. But even if the bigger one sounds much better, I'm afraid there's just no room for it...

26th September 2010, 02:01 PM	#5
arjen diyAudio Member Join Date: Jul 2007	Alas it's not only the floor footprint. It's the obtrusiveness that counts. Is it the first thing that you see when you enter the room. I have build LT's, BR's, and even a horn in the past but that was then and this is now. This is actually the first sealed box I ever build, so it's also a learning experience. Thanks, Arjen