ClassB power amp for a subwoofer

[ashok]

I was wondering if a classB power amp would show up any audible artifacts when driving a subwoofer which is typically rolled off by about 100Hz at 24dB or 48dB /octave. With NFB the distortion would be not too great numerically. Would such an amp sound different from one with a classAB o/p stage when used as a sub amp?
The logic being that typical bass signals are quite large anyway and away from the low signal range where the distortion percentage would be high !Plus the real sub drivers typically don't have a very wide bandwidth.

I think it may not but I guess I'll have to try it out and see what its like. Anyone tried this ?

 

[TBTL]

Most class B amplifiers actually are class AB. The crossover distortion of a pure class B amp will be audible, as most subwoofer drivers still respond up to say 1 kHz. Note that the low pass at 100 Hz is before the signal is sent to the amplifier, so it does not attenuate distortion products.


What do you mean with NFB?

 

[ashok]

Well what I meant was that with NFB the distortion content would numerically be lower in the amp, but you are right it will probably matter as the roll off is in the (active !) crossover and not in the driver.

 

[nigelwright7557]

Most class B amplifiers actually are class AB. The crossover distortion of a pure class B amp will be audible, as most subwoofer drivers still respond up to say 1 kHz.

In class B I find I can only hear crossover distortion at low listening levels.
I cant seem to hear it at moderate to high levels.

I turned down the bias on my mosfet amp to zero to test it.

 

[ashok]

I felt that with bass signals maybe we would not hear it at least most of the time. Typically bass signals are far higher in amplitude than everything above say 100Hz. But I am still going to try this out with a zero bias power amp. I have several here that I can experiment with plus a range of subwoofer drivers !
Maybe I should clarify that the subwoofer has an active crossover. If it did have a passive crossover the crossover would roll of some of the harmonics. Will have to see if it sounds 'bad' or just 'different' !