silly subwoofer question...do not laugh!

hi all.

What I'd like to know is whether a powered subwoofer amplifier inputs have filtering circuitry and whether a line level signal is fed to them or is the filtering done in the AV receiver that one would normally use and hence a signal with low frequency components is sent to the sub woofer?

If they accept line level signals and do the filtering themselves, is there a standard production method for powered subwoofers? Or do some have the filters and do others rely on the AV Receivers subwoofer output?

Most powered subwoofers provide an internal crossover so that they can be implemented in a variety of systems, both stereo and HT. These are perfectly happy with a full-range line-level signal.

Many allow this internal crossover to be defeated for use with an AVR that does it's own "bass management", either via a switch ir a separate line-level input. Even if they don't allow a bypass, you can generally set the crossover to it's highest frequency and be back in the ball game.

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Originally Posted by dolt

hi all.

What I'd like to know is whether a powered subwoofer amplifier inputs have filtering circuitry and whether a line level signal is fed to them or is the filtering done in the AV receiver that one would normally use and hence a signal with low frequency components is sent to the sub woofer?

If they accept line level signals and do the filtering themselves, is there a standard production method for powered subwoofers? Or do some have the filters and do others rely on the AV Receivers subwoofer output?

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Most plate amps I'm aware of have a filter, it's usually 2nd order (12 dB/octave) which isn't all that great for subwoofer purposes. I'm seeing more 4th order (24 dB/octave) filters now though but that's mostly on more expensive subs.

AV receivers will usually be a better solution in the home theater world because you can apply the receiver's filter (usually 4th order now) to both the speakers and sub at the xo point, resulting in better integration.

thanks for both your replies.

kexodusc, what if the the subwoofer was going to be used primarily for music, and not for movies. I already have an old stereo amplifier which I've grown very attached to. The only trouble is that its a bit shy on bass notes.

How would my system fair if I connected a powered subwoofer to the "pre-amp out" of my stereo amplifier? I know the signal wouldnt be line level, but I doubt that the subwoofers amplifier input would be strained (or would it?...). This would also save me a lot of money than if I where to buy an AV Receiver with lots of features that I dont use.

I've tried various different speakers that where available to me and I've noticed that the the amplifiers frequency output range is not that expansive, hence the above question. Is this a viable solution or do I need to invest in a new amplifier? Would the subwoofer make a difference at all in my proposed scheme?

Quote:

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Originally Posted by dolt

thanks for both your replies.

kexodusc, what if the the subwoofer was going to be used primarily for music, and not for movies. I already have an old stereo amplifier which I've grown very attached to. The only trouble is that its a bit shy on bass notes.

How would my system fair if I connected a powered subwoofer to the "pre-amp out" of my stereo amplifier? I know the signal wouldnt be line level, but I doubt that the subwoofers amplifier input would be strained (or would it?...). This would also save me a lot of money than if I where to buy an AV Receiver with lots of features that I dont use.

I've tried various different speakers that where available to me and I've noticed that the the amplifiers frequency output range is not that expansive, hence the above question. Is this a viable solution or do I need to invest in a new amplifier? Would the subwoofer make a difference at all in my proposed scheme?

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Should be able to use the pre-outs of the amplifier to the sub, and set the filter on the plate amp. I would recommend setting it as low as possible for best integration but play with it and see what sounds best to you.

Many older receivers had a pre-out, pre-in loop with a pair of "U" shaped jumpers. Many subs have a pair of RCA inputs and RCA outputs.

By hooking a sub to the pre out and then using the sub output to connect to he receiver pre-in you will get the correct low pass/high pass crossover so that the main L/R speakers don't get the sub bass signals.

The more expensive subs will even have a variable crossover frequency switch or potentiometer as well as a level matching control. An extra option is a phase switch.

While all these adjustments are a major pain to set correctly, they can be quite important for music listening. IMHO they seems far less important for HT.