Ohms ? [Archive] - Audio & Video Forums


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05-11-2006, 01:37 AM
I went to buy a replacement subwoofer for my home & most of the speakers in the home audio book are 8 ohms.My subwoofer amp is only 100 watts(peak) The blown subwoofer is 4 ohms. My Q. is If I buy a 8 ohm subwoofer will it become only a 50 watt peak? The FTC rating in the owners manual reads as such...less than 1 % THD @ 56w@ 100HZ@ 4 ohms. My 12db/Oct adjustable crossover only goes from 40HZ TO 180HZ

05-11-2006, 03:46 AM
Basically, yes...50 watts would be what you could expect in theory. However, most amps aren't quite so perfect. It's possible your amp could deliver 55, 60, or even 70 watts into an 8 ohm load. Amps don't produce double the power into 4 ohm loads because of inefficient losses along the way (well some companies will artificially lower the 8 ohm specs to suggest they do).

You had better be using a very efficient woofer, 91 dB or more if you want to use an 8 ohm subwoofer. The higher the better. I'm guessing it will be cheaper to buy a new sub amp than find a high efficiency, 8 ohm subwoofer though.

05-11-2006, 07:06 AM
Thanks alot! Do you do audio work for a living due to the fact that you are VERY good at helping me w/ my audio trouble.?

05-11-2006, 07:18 AM
Nah, I've just read a some books and a bunch of internet resources to help me answer many of those same questions for my speaker building hobby...

Some things I know, some things I don't...and trust me, I'm still very much an amateur in many areas of this stuff....