Axiom Home Page Forums General Discussion Technical Questions M80 Max 400w?

There seems to be a lot of debate in the psychoacoustic world about "how many dB to sound twice as loud" but there's no question that the most common answer is that a 10dB change in SPL sounds twice as loud (and takes 10x the power to achieve).

Reading between the lines, it sounds as if it might take a bit less than 10dB to sound twice as loud at low SPLs, and a bit more than 10dB to sound twice as loud at high SPLs, ie even the ear's logarithmic response is only an approximation.

I do think Jakeman's original statement was correct.

I just read the article by Alan he says "The lesson in all this is that you can never have too much power , and that big amplifiers rarely damage speakers. Little amplifiers driven into clipping burn out speakers. In the scheme of high fidelity, that last barrier to realism is having enough power and being able to approximate real-life loudness levels"

I don't plan on getting an amp that puts out 400 watts, but close! Adcom GFA 7707 is what I've been looking at.

thanks for all your replies!

Mike

I think a more useful number (well, for me) is you need to double the power in order to get a 3dB increase in volume into the same load/speaker.

If you have a 87dB efficient speaker, it can play 87dB @ 1 watt (usually at 1 meter, which means less volume at your listening chair). 90dB at 2 watts, 93dB at 4 watts, 96dB at 8 watts, 99dB at 16 watts, and so on. You reach a ceiling pretty quickly, which is why, if you like it loud, speaker efficiency is every bit as important (maybe more so) as amplifier power.

The difference between a 100 and 200 watt amplifier, in total volume - all else being equal - is +3dB total volume. Of course, the more powerful the amp, the better able it is to handle transients at louder volumes. I've seen different numbers for transient peaks, with regards to required amplifier power - anywhere from 3x to 10x (i.e., if you're using 10 watts of continuous power at a given volume, you'll need anywhere from 30 - 100 watts in order to properly handle the peak transients in music/movies).

I'm going on memory, so hopefully this is correct. The gist of it is that you can never go wrong buying the most powerful amplifier you can afford. You'll never use 400 Watts continuous in real world listening, but you may need a huge reserve to handle the peaks.

wid: interesting. I have never seen the term "subjective loudness" used before. Of course, when you are drinking music tends to be played louder, MUCH LOUDER!!!!

All that said, I stand by what I post about electrical math. In electrical terms, what I said was 100% correct.

Budget: true. And, with the GIANT amp, you can always say to someone else, "mine is bigger than yours."

LOL!!!!

I want a bigger amp!!!

Budg, that's pretty much it: a doubling of power results in only a 3dB increase in the maximum sound level possible on brief peaks. The increase in level is logarithmic, not linear, so exactly the same 3dB increase occurs between 1 and 2 watts, 10 and 20 watts, 100 and 200 watts, etc. Also note that the sound level using 1 watt is actually quite loud, and is what might be used for a typical average listening level. The peak power required might vary from practically nothing more in the case of some almost uniformly loud pop music recordings to 100 times or more for very dynamic material, such as some classical items that I have.

Yeah, Bernard, the term "subjectively twice as loud" is seen fairly often, but nobody knows what it really means.

>>Yeah, Bernard, the term "subjectively twice as loud" is seen fairly often, but nobody knows what it really means.

Amen to that. Even as I was typing my last post in the back of my mind I was thinking "so what *does* <twice as loud> sound like ?"

I believe it's the incremental difference between one hand clapping and two hands clapping.

No wonder it takes 10 times as much power.

It gets even more confusing when you factor in electronic crossovers. If you have a normal HT setup, the bottom two octaves are filtered prior to amplification for the 5 or 7 speakers. The sub fills in the 20-80Hz range, using it's own amplifier. Thus, your 100 watt amp - unencumbered with reproducing the power-hungry frequencies of 20-80Hz - can now play louder and cleaner. This is one of several reasons to buy a quality powered sub - especially if you use a reciever to power all 5 or 7 channels.