Do you need a crossover/filter for a sub?

TheLaw117 · 03:00 AM

Hi,

You might know I'm working on an LM3886 Stereo amp. I'm a bit antsy you see...

While I'm in the amplifier/speaker building mode. Does anyone actually use a filter for a subwoofer? Is it worth it I mean?

EVENTUALLY, I'd like to get one of those nice 8" HiVi M8a's. Eventually...that is.

Also, is there a special type of amp required? Are 2x bridged LM3886s not good?

Thanks a bunch. Just out of curiosity.

PeteMcK · 9th March 2011, 03:12 AM

yes, you need one; the easiest way: TLS.org | Passive Line-Level Crossover

TheLaw117 · 9th March 2011, 03:14 AM

Quote:

Originally Posted by PeteMcK

yes, you need one; the easiest way: TLS.org | Passive Line-Level Crossover

I mean only a subwoofer. Just a subwoofer in a box...no other speaker.

Still?

N-Brock · 9th March 2011, 03:21 AM

Yes, still. if not the sub will sound poor.

You could use a PLLXO, a passive crossover (more expensive), or an active crossover 9even more $$)

If in doubt you can try it without a crossover, shouldn't hurt anything, but most subs are designed to only play on the lower end.

N-Brock

AllenB · 9th March 2011, 07:30 AM

Do you want your sub/s to be reproducing midrange? Apart from hearing it, if it/they are not close to your mains then you may end up with cancellations (comb filtering).

Unless you build bandpass subs which have inherent physical low pass filtering.

audiobomber · 11:42 AM

You may be able to use a sub without a filter if it's strictly used for a Home Theater ".1" channel, with all the other speakers set for full range operation. For any other setup, no way, a sub without a filter sounds horrid.

AllenB · 9th March 2011, 09:26 PM

If I assume by your reply that you are keen to get on with it, a simple inductor with the speaker lead will get you started, and maybe a well chosen electrolytic capacitor across the speaker terminals to go with it. No big deal until you want to start getting exact.

TheLaw117 · 10th March 2011, 12:18 AM

Thanks. I won't be building the sub for a while, but I was just curious...

And would I need to use a different type of amp? Or...?

9th March 2011, 02:58 AM	#1
TheLaw117 diyAudio Member Join Date: Sep 2010	Do you need a crossover/filter for a sub? Hi, You might know I'm working on an LM3886 Stereo amp. I'm a bit antsy you see... While I'm in the amplifier/speaker building mode. Does anyone actually use a filter for a subwoofer? Is it worth it I mean? EVENTUALLY, I'd like to get one of those nice 8" HiVi M8a's. Eventually...that is. Also, is there a special type of amp required? Are 2x bridged LM3886s not good? Thanks a bunch. Just out of curiosity. Last edited by TheLaw117; 9th March 2011 at 03:00 AM.

9th March 2011, 03:12 AM	#2
PeteMcK diyAudio Member Join Date: Feb 2002 Location: Western Sydney	yes, you need one; the easiest way: TLS.org \| Passive Line-Level Crossover __________________ Impedance varies with frequency, use impedance plots of your drivers and make crossover calculations using the actual impedance of the driver at the crossover frequency

9th March 2011, 11:39 AM	#6
audiobomber diyAudio Member Join Date: Jul 2004 Location: Sudbury, Ontario Canada	You may be able to use a sub without a filter if it's strictly used for a Home Theater ".1" channel, with all the other speakers set for full range operation. For any other setup, no way, a sub without a filter sounds horrid. __________________ Dan Last edited by audiobomber; 9th March 2011 at 11:42 AM.

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9th March 2011, 03:21 AM	#4
N-Brock diyAudio Member Join Date: Oct 2007 Location: Cambridge, MA Blog Entries: 4	Yes, still. if not the sub will sound poor. You could use a PLLXO, a passive crossover (more expensive), or an active crossover 9even more $$) If in doubt you can try it without a crossover, shouldn't hurt anything, but most subs are designed to only play on the lower end. N-Brock

9th March 2011, 07:30 AM	#5
AllenB diyAudio Member Join Date: Oct 2008	Do you want your sub/s to be reproducing midrange? Apart from hearing it, if it/they are not close to your mains then you may end up with cancellations (comb filtering). Unless you build bandpass subs which have inherent physical low pass filtering.

9th March 2011, 09:26 PM	#7
AllenB diyAudio Member Join Date: Oct 2008	If I assume by your reply that you are keen to get on with it, a simple inductor with the speaker lead will get you started, and maybe a well chosen electrolytic capacitor across the speaker terminals to go with it. No big deal until you want to start getting exact.

10th March 2011, 12:18 AM	#8
TheLaw117 diyAudio Member Join Date: Sep 2010	Thanks. I won't be building the sub for a while, but I was just curious... And would I need to use a different type of amp? Or...?

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