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TheLaw117 9th March 2011 02:58 AM

Do you need a crossover/filter for a sub?

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: | Passive Line-Level Crossover

TheLaw117 9th March 2011 03:14 AM


Originally Posted by PeteMcK (
yes, you need one; the easiest way: | Passive Line-Level Crossover

I mean only a subwoofer. Just a subwoofer in a other speaker.


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.


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 9th March 2011 11:39 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...?

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