Subwoofer Specs?

Ok, I have a KLH Subwoofer. I like it, it sounds good, but is not as loud as my other speakers. I was interested to know more about it, so I picked up the specs book.

It says under FTC Rating: <10% THD @ 125 Watts @ 100Hz @ 4 ohms.

1: Whats the <10% THD mean?

2: What does 4 ohms mean?

3: What does FTC Rating mean?

4: Is there a way to find the sensativity level with this data?

THD means Total Harmonic Distortion. <10% is not bad for a subwoofer, but that is only at 100Hz, not a particularly difficult frequency to reproduce. 125W is a pretty hefty input at 100Hz, and that should sound pretty loud. The more important spec would be the THD at 40Hz. 4 ohms is the speaker impedance; it doesn't mean anything to you unless the amplifier you want to hook it up to won't drive a 4-ohm speaker. That is very unlikely, since 4 ohms is not uncommon. I"m not sure what FTC means. There is no way to determine sensitivity from these specs. You should be able to get sufficient bass volume from that speaker, so turn up the bass level (subwoofer level) on your receiver. You should really adjust the level with test tones and a sound level meter (you can get one from Radio Shack--get the analog model, not the digital, it is not very expensive and easy to use). I wouldn't worry too much about its specifications. Instead, adjust its level (and maybe the crossover)to where it blends in best with the rest of the system. I've seen systems where the receiver was rated for 100 watts per channel, but the subwoofer was rated for only 50 watts. It still worked out beautifully, because the subwoofer's level was adjusted properly. You can do all of by ear. You don't need expensive level meters like some insecure audiophiles go to the trouble of using.

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