[treeman43]

ok...i've tried an experiment (i'm new at this). i've set up my spl meter at listening position, on a tripod, pointing at the ceiling. i've entered the distances from the speakers (7.1) to that sweat spot into my denon 3805 receiver. the main volume on the denon at 0.0. then i set the meter at 70. using the internal receiver tones, i adjusted the individual speaker db's, so that i got 75db readings on the meter(70 plus 5). the fronts are set to small (though they are large floor standing). the sub was 'off' when calculating all speakers. i then turned on the sub lastly and kept that spl reading at 70db. (isn't the sub supposed to read approx. +5 more than the others?).

here's what i got:

LF: +2.5

C: +2.0

RF: +2.5

RS: +6.5

RSB: +1.0

LSB: +1.5

LS:: +2.5

SW: +6.0


then....i tried the meter at 80. to get 75db's i would then simply subtract 5db's.

i fiqured that the outcome would be the same.

here's what i got:

LF: -1.0

C: -0.5

RF: -0.5

RS: +3.0

RSB: -2.5

LSB: -1.5

LS: 1.0

SW: +5.0


why so different? my room is set up for a projection theater, but because of a support pole, the seating area is off center. any advice is appreciated. i have ordered a reference mic and also an avia disc....but wanted to try this first. thanks.

 

[AV Doogie]

The first thing I would do is get a calibration disk like avia or DVE. Internal test tones are notoriously flaky.....depending upon the reciever or brand etc. Depending upon which type of SPL meter you are using, the meter may not respond well to very low or very high frequency signals. Are you also using the 'C' weighting on the SPL meter?


The white noise generator in your reciever may not produce a flat response??

 

[treeman43]

i'm using 'c' weighting and 'slow' response. i've also ordered an avia disc, so that will get to me this week, i hope.

but, all in all.........notorious or not, this difference is so extreme that i just had to ask. i didn't move anything, the phone didn't ring, and the j.w.'s didn't knock on my door offering eternal life.............i was stumped. thanks for replying though.

 

[treeman43]

oh, i forgot.....i have a denon 3805 receiver.

 

[AV Doogie]

The Denon is pretty respectable, I have a Lexicon MC12....and I don't use the internal test tone on this unit either!


Looking at your readings, the magnitudes are fairly respective except for the RS and Sub. Subtract 3.5 from all of the above readings and they are fairly close. I would not worry about checking levels at volumes other than the typical movie listening level or audio (music) listening level.