Axiom Home Page Forums General Discussion Technical Questions Underpowered receiver? How loud can I go?

By the way guys, below is the response I got from NAD about the problem. I don't know what an overmodulated CD is or what kind of sound it generates. Any thoughts about whether this is what is really happening? It's true that the sound was not EXTREMELY harsh. It sounds something like the resonance of a loose metal part, I'm pretty sure that it's not just the bass string slapping against the wood, because I hear that clearly and cleanly at lower volumes.

Roger

>The amount of sound out depends on the amount of
>signal in. The 2 o'clock actual volume can vary
>tremendously, but if you aren't playing at very loud
>perceived volume in a large room, I very much doubt
>that the C350 is clipping. (That would produce
>EXTREMELY harsh sound, and damage to tweeters
>within a short time.) I suspect that the CDs in question
>are overmodulated, and that while the C370 would
>produce greater ease (having twice the overall power),
>it might not address this issue.

I have found this web-page to be very helpful in addressing the "how much / how loud" question:

http://www.soundandvisionmag.com/Buying_Tips/articledisplay.asp?ArticleID=66

The article is very comprehensive, including tables that let you make your own assessments, but here is a particularly relevant excerpt:

"Stating power capabilities in dBW is useful in another way: you can simply add dBW power figures to a speaker’s sensitivity rating to get an approximate value for the maximum undistorted sound level that can be generated by a given receiver (or amplifier) with that speaker. With a speaker having typical sensitivity — say, 90 dB sound-pressure level (SPL) with a 1-watt input — a 17.25-dBW receiver will generate up to 107.25 dB SPL at 1 meter, which is very loud for a home theater or listening room (the SPL at the main listening positions may be somewhat lower since most people sit more than a meter away from their speakers). You can actually trade off receiver power for speaker sensitivity — as power in dBW goes down, speaker sensitivity should go up by at least an equal number of dB SPL. A very careful shopper can save money by buying a less powerful receiver and still end up with a system that can play very loud if the speaker sensitivities are high."

I wanted to update anyone interested in the problem I was having with my amp and the m22is. The buzzing came from a problem with one of my drivers, which Axiom replaced promptly. The amp was not clipping. Problem solved. Nevertheless, I upgraded from the NAD C350 (60w/ch) to the C370 (120w/ch). This has made a dramatic difference in my attempt to fill a pretty large room with loud music. The new amp is both louder and cleaner. And it is really unbelievable how much sound the M22is can produce. There are some CDs where the speakers actually became too loud for our enormous 50X50 ft room. At those volumes I do notice the need for more bass energy, but this is at volumes where it is painful to stand in front of the speakers. I think I can also hear more distortion in the speakers at these volumes (they just don't sound as precise), which again takes me back to the thought of have two pairs of m22is rather than adding even more amplifier power or a subwoofer. Seems I'd get better dispersion, more bass energy, and less speaker distortion, because I'd be running the speakers at lower volumes. True or False?

Roger,

Youe last comment/question is mostly true. Running two pair of (identical - equal sensitivity) speakers very close together (i.e. side by side) generally, would increase your SPL (volume) by about 3db (everything else being equal)- as that configuration produces an additive process to the loudness - and thus you could drive your amp at a lower power to achieve the same "loudness". However, a 3db change is considered only a "noticable change" in volume. (It takes a change of 10db to be considered twice as loud) Dispersion would depend on how you "aimed" the speakers and imaging would be diminished - but somehow, I don't think that is the issue. But if you stacked the M22s exactly alike on top of each other, you could minimize the imaging loss.

Good luck,

Randyman