woofers in parallel

soundnovice · 11th November 2011, 07:53 AM

hi
i have two woofers with rated SPL of 82dB. if i connect them in parallel how much SPL i can expect from them?

thanks
pranam

speaker dave · 11th November 2011, 09:31 AM

For the same voltage input, 88dB. They will add in phase and pressure will double.

So what happens in terms of power?

David S.

AndrewT · 11th November 2011, 09:39 AM

Two drivers in parallel will try to draw double the current. If the amplifier were perfect (or you used two identical amplifiers) then the doubled current equates to doubled power and that gives a +3dB in SPL. A real amplifier will probably achieve +1.5dB to +2.5dB

If the two drivers can reinforce each others' output, there is potential for another +3dB in SPL. That extra output is only available over a narrow frequency range.

speaker dave · 11th November 2011, 09:46 AM

Anybody else?

umut1001 · 11th November 2011, 09:51 AM

Andrew described very good so there is no need to tell something more.

speaker dave · 11th November 2011, 09:55 AM

Sot thats 2 votes for +3dB and 1 vote for +6.

The +3s have it.

soundnovice · 11th November 2011, 09:55 AM

i simulated the FR curves and i can see an increase in SPL when drivers are connected in parallel. can i safely use this SPL increased FR for passive xover design? one advantage i am seeing is both woofers(after connecting them in parallel) and tweeter have almost equal SPL, so no need for tweeter sensitivity attenuation.
however since the woofers have Rdc=5.8. after connecting in parallel effective Rdc=2.9 ohms which is very low for an amp rated at 4 ohms. how to tackle this problem?

umut1001 · 11th November 2011, 09:58 AM

yes.In perfect conditions +3dB, the woofer frequency response should be same for getting +3 db.You should use matched woofers.Otherwise there may be distortion.Acoustic is very complicated science.

speaker dave · 11th November 2011, 10:06 AM

Quote:

Originally Posted by umut1001

yes.In perfect conditions +3dB

Sorry, you already voted.

Quote:

Acoustic(s) is very complicated science.

Thats why I'm just adding vectors.

AndrewT · 11th November 2011, 10:17 AM

Speak,
read my post again.
+3dB, if the amplifier power is perfectly doubled.
+3dB, over a narrow frequency range, if the speaker outputs can reinforce each other.
That adds to a potential +6dB over a narrow frequency range.
Read again and you see why you can't get a blanket +6dB.

11th November 2011, 07:53 AM	#1
soundnovice diyAudio Member Join Date: Jan 2011	woofers in parallel hi i have two woofers with rated SPL of 82dB. if i connect them in parallel how much SPL i can expect from them? thanks pranam

11th November 2011, 09:39 AM	#3
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Two drivers in parallel will try to draw double the current. If the amplifier were perfect (or you used two identical amplifiers) then the doubled current equates to doubled power and that gives a +3dB in SPL. A real amplifier will probably achieve +1.5dB to +2.5dB If the two drivers can reinforce each others' output, there is potential for another +3dB in SPL. That extra output is only available over a narrow frequency range. __________________ regards Andrew T.

11th November 2011, 09:51 AM	#5
umut1001 diyAudio Member Join Date: Mar 2007 Location: Istanbul	Andrew described very good so there is no need to tell something more. __________________ My New and vintage capacitor store: http://stores.ebay.com/Paradise-of-H...dio-components

11th November 2011, 09:58 AM	#8
umut1001 diyAudio Member Join Date: Mar 2007 Location: Istanbul	yes.In perfect conditions +3dB, the woofer frequency response should be same for getting +3 db.You should use matched woofers.Otherwise there may be distortion.Acoustic is very complicated science. __________________ My New and vintage capacitor store: http://stores.ebay.com/Paradise-of-H...dio-components

11th November 2011, 10:17 AM	#10
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Speak, read my post again. +3dB, if the amplifier power is perfectly doubled. +3dB, over a narrow frequency range, if the speaker outputs can reinforce each other. That adds to a potential +6dB over a narrow frequency range. Read again and you see why you can't get a blanket +6dB. __________________ regards Andrew T.


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11th November 2011, 09:31 AM	#2
speaker dave diyAudio Member Join Date: Nov 2009 Location: Toronto	For the same voltage input, 88dB. They will add in phase and pressure will double. So what happens in terms of power? David S.

11th November 2011, 09:46 AM	#4
speaker dave diyAudio Member Join Date: Nov 2009 Location: Toronto	Anybody else?

11th November 2011, 09:55 AM	#6
speaker dave diyAudio Member Join Date: Nov 2009 Location: Toronto	Sot thats 2 votes for +3dB and 1 vote for +6. The +3s have it.

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