A question for you audiophile mathmaticans

aaharvel

Double the wattage is a +3db. difference, correct?

i'm just wondering since my 5300 amp is 80x2, powering my stereo pair,
and my 7300 amp is 60x5, powering my center and 4surrounds~ should I go ahead and increase the center and 4surrounds to +1 in the pre-amp?

spl is pretty close, but JUST in the sweetspot is not realistic. SHould I just use the numerical formula?

the difference between 80watts and 60watts is 20.
20watts is 1/3 the amount of the lesser 60.
1/3 of +3 = +1 (so +1 for the center and 4surrounds) ? ??

ok i've gone crosseyed... :rolleyes:

hoosier21

Your thinking too much, you should set it up with a spl meter and the test tones in the pre/pro.

aaharvel

i like to think damnit! :cool:

seriously the only reason i'm doing this is b/c basing the system JUST on test tones is pretty much useless if you're ever sitting outside the sweet spot AND if your amps aren't equal in power.

PolkThug

Take measurements from different seats, then tweak away til you find a good average for everybody.

mantis

There is no way to exaclty adjust for the difference in power. What I have experienced when having 2 different amps driving a theater system is difference in dynamic range. When things happen onscreen, the lesser dynamic amp doesn't keep up with the other. This can be a huge problem depending on the person listening.

I just left a customers house hwo also is having this very same thing. He is trying to use his receiver to power his center channel and rears and allowing his mains to be powered off a 2 channel amp. What a huge difference when things happen. The center channel gets drowned out . The mains jump out and bite you in the face while the center gets lost in the mix. Then when it's just time to talk and mellow out on the screen , the center channel is to low. You have to turn the volume up to a comfortable level so you can hear what the hell people are saying. When dynamic range kicks in , it's way to loud.

My suggestion was to get a 5 channel amp so this problem will go away. He likes his receiver as a preamp (Denon avr3806) so going pre and amp is out of the question untill he trys it.

I feel this is what you should do. Stop hurting your mind and put the pressure on your wallet. You'll be much happier without the money and with a system you can fully enjoy.

Dan

aaharvel

thanks Mantis. Although the lesser Adcom doesn't get drowned out, since this is different than comparing receiver vs. sep. amp~ i was just trying to maximize my setup with something that I might be unaware of. But that's a good post, and thanks for the advice.

BY THE WAY MY DESK CHAIR AIR PUMP JUST BROKE. KARMA FOR STARTING SUCH A STUPIDASS POST? hmm... :rolleyes:

John K.

Andrew, the maximum power rating of an amplifier, regardless of whether it's 60 watts or 600 watts, makes no difference in what you're trying to do. Yes, doubling amplifier power would allow a peak to be played 3dB louder(but you may have the misimpression that the more powerful amp is always louder). At comfortably loud average listening levels most speakers use about 1 watt. Depending on factors such as dynamics of the material, room size, listener distance etc., brief peaks might require 50, 100 or even more watts for a split second. The difference between the 60 watts and 80 watts which you mention is 1.25dB at peaks, but again this has no significance at the usual lower levels. Different amps can have different gain and have to be set differently to output the same power and different speakers with different sensitivities can require different power to play at the same loudness level, but difference in maximum power output is meaningless in regard to balancing the speakers. As was suggested, you should use a SPL meter to balance the outputs of your various speakers.

aaharvel

thanks John K. I'm just leaving everything as it was. 0db. for all speakers, and balanced with the SPL meter. I've changed nothing, this thread i've started is retarded, and my chair is STILL fubared!

McLoki

I was running the front stage through my Cinepro and my rear speakers through my Onkyo amp. to match the levels with an spl meter I had to set my front speakers -1db with the rears at +4.

Since I got my amp fixed (only 4 channels were working - now 6 are working) all levels are set to -1db to be at reference level.

I am not sure if it was the more powerful amp in the front channels or the additional sensitivity of the amplifier inputs. (probably a combination of the two) Anyway - as others have mentioned, just set all channels with an spl meter and don't worry about it.

Michael

heiney9

mantis wrote:

There is no way to exaclty adjust for the difference in power. What I have experienced when having 2 different amps driving a theater system is difference in dynamic range. When things happen onscreen, the lesser dynamic amp doesn't keep up with the other. This can be a huge problem depending on the person listening.Dan

This is certainly true for amplification that may be substantially different. In this case the Adcoms are very similiar units in build and parts. I would think in this particuliar case tweaking would be the best remedy. Certainly at the limit the lesser powered amp might begin to audibley (sp) falter before the higher powered amp but in normal listening tweaking to get the right mix is the best solution. Unless you're just looking for an excuse to spend money .

Now if you had multiple amps from diff manufacturers, or a gross diff in output or design then moving to a 5-ch amp is one way to go.

YMMV

H9

shiu

aaharvel wrote:

Double the wattage is a +3db. difference, correct?

the difference between 80watts and 60watts is 20.
20watts is 1/3 the amount of the lesser 60.
1/3 of +3 = +1 (so +1 for the center and 4surrounds) ? ??

ok i've gone crosseyed... :rolleyes:

If you want to calculate power gain/loss in dB, you can use the formula, gain in dB=10*log(P2/P1), 10*log(80/60)=1.25. Most calculators have the log (to the base of 10) function key. Of course this forumla is irrelevant to what you are trying to do but you know that already.

reeltrouble1

AAharvel,

Balancing with SPL is correct. Some amps come with controls to help your situation like say B&K for one. When using diff manufacture's the slew rates and impedences are likely different which can cause problems.