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Question about sound below an amps frequency specs

if an amps frequency response are spec'd out to be between 20hz to 20khz, will it pass information above and below those numbers?For instance will it pass a 15hz tone or will any information below 20 hz be cut off by some internal filters. If an A/v receiver has the same frequency specs in their manual, will it also cut off info above or below its stated specs? Could info going through its LFE be cut off below 20hz as well. The reason I ask is when I was playing a Realtraps bass test CD I downloaded, my speakers had no info below 20hz, though the disc starts with 10hz tones. Just for fun I played the same disc using my tube amp and had significant bass through my mains well below 20hz. Which made me wonder.
shiva

Showing 2 responses by eldartford

eldartford
4,262 posts
 
In order to eliminate LF "noise" such as air conditioning rumble on the recording, or TT rumble when playing a LP, many electronic units do have a sharp filter below 20 Hz. The idea is that this signal wastes amplifier power, and drives loudspeaker cones in and out, which you can't hear but which causes distortion of higher frequencies that you can hear.

In general I think this is a good idea. However, I have one CD of a Wurlitzer theatre organ that has a continuous non-musical LF rumble at and below 20 Hz (per my spectrum analyser). I have heard the actual organ, which is in a pizza restaurant in Mesa, Arizona, and this sound comes from the wind generation machinery. If you filtered it out you might like the sound better but it wouldn't be like the real thing.
eldartford
4,262 posts
 
Jeffreybehr...The typical "rumble filter" (every one I ever had) was third order, 18 db/octive with 18 HZ as the -3 dB point. Such a filter would have only a couple of dB effect at 20 Hz, and most loudspeakers require more than a few dB boost to get to 20 Hz.
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