Speaker System Calibration

reeltrouble1

Polkie needs help.

When I first set up my system I just calibrated to 75db using the Rat shack meter and the receiver test tones. So then I add a second 450 sub and Mantis tells me how he sets these up. So I do this and sounds good. But then I buy the Avia disc. They talk about how 85 is the true level for the DD recordings etc. OK, this is very loud I understand, but what is the difference, if I calibrate to 75 or 85? I thought I was just trying to get the same pressure level from each speaker. I mean why not 65? And just turn up to where I like it? If you calibrate to 85 then how do you know where to turn up master volume? Just go to 0 relative on the reciever? Measure somehow with the SPL? I know its about how it sounds to me, but I am trying to understand the theory. Even at 75 the system gets very loud before 0 relative on the reciever. My room is 2970 3/ft, with some large openings.

Help!!!!!!!! I guess I still just do not understand what proper calibration means.

danger boy

did you set the calibration using the AVIA disc? use that instead of your receivers test tones.

Dr. Spec

There is a difference between balancing all the speaker levels (which can be done at any volume for the test tones), and calibrating to Reference Level (which must be done at either 75 dB or 85 dB depending on the specific disc).

The whole point of calibrating a system to Reference Level is that it (or any level below it) would be the same volume in any room for any given DVD scene. It is a universal benchmark by which we can all experience the same playback level.

Yes, I use Master Volume 00 for Reference Level calibration, simply for convenience.

I usually listen at anywhere from -15 to -10 (with Reference Level being 00), depending on the DVD.

Very few systems can be played at true Reference Level - the subwoofer can't handle the load, and it is often too loud anyway. Again, the whole point is establishing a benchmark that we can all "reference" to for playback volume.

Doc

reeltrouble1

Thanks Guys,

Doc,

When you calibrate with the Avia, how do you do your Surround backs? I am running 6.1, the disc outputs sound to the surround side and back. Just don't worry about it?

danger boy

i use 75db when i set up my speakers.. 85 db would be to much for me. unless I wore ear plugs or something.

Dr. Spec

Originally posted by reeltrouble1
Thanks Guys,

Doc,

When you calibrate with the Avia, how do you do your Surround backs? I am running 6.1, the disc outputs sound to the surround side and back. Just don't worry about it?

GREAT question! I have a method that works almost flawlessly.

With Avia, set your Master Volume to 00, and get the five surround channels all reading exactly 85 dB at the meter. BTW, the meter should be on C-weighted Slow, placed EXACTLY where your head/ears would normally be, facing forward, and angled up about 40 degrees.

After you balance and calibrate with Avia, leave the Master Volume at 00 and run the internal test tones. Note the volume for each speaker - they should all be almost exactly the same (but not necessarily 85 dB). Simply match the rear channels to the other channels at Master Volume 00 and you're all set for the rear surrounds.

FYI - Reference Level is defined by Dolby Labs as 105 dB bass peaks from any surround channel and 115 dB bass peaks from the LFE channel (since the LFE channel is automatically boosted 10 dB by your DD/DTS processor).

If there is a simultaneous bass peak in a surround channel and the LFE channel (such as might happen in U-571), then the resulting sound pressure would be 121 dB.

Since most surround channels are incapable of producing a 105 dB bass peak, we set them to small for HT and let the subwoofer handle the low passed bass, AND the LFE channel. So you can see, the subwoofer will be required to produce upwards of a 121 dB bass peak at Reference Level if the speaks are set to small. This brings into sharp focus the need for an extraordinarily high quality and powerful sub if you ever hope to even approach Reference Level for playback.

The reason you calibrate Avia to 85 dB is because the test tones are mastered on that disc at 20 dB BELOW the typical mastering level for bass peaks on a DVD. So at Master Volume 00 if Avia gives you 85 dB, then a "typical" DVD will give you 105 bass peaks from the surround channels and 115 dB bass peaks from the LFE channel.

Of course, not all DVD are mastered at exactly the same level - in fact there is significant variation in their mastering levels. Some DVD's are mastered on the "hot" side, and others are mastered "cool", and some are "just right" - like the three bears.

LOTR-FOTR DD theatrical version is a good example of a DVD that is mastered quite hot - it runs about 4 dB higher than most other DVDs. Couple that with a very aggressive bass track and you've got a subwoofer destroyer on your hands at anywhere near Reference Level.

Doc

donahue

Hi,

I've got the NAD T761 HT Receiver and the volume starts off negative and goes to some positive number (not sure of the actual numbers). Are you saying that the master volume should be set to 00 even with this kind of volume control? If not, what should the setting be?

Thanks,

Ray

Dr. Spec

Originally posted by donahue
Hi,

I've got the NAD T761 HT Receiver and the volume starts off negative and goes to some positive number (not sure of the actual numbers). Are you saying that the master volume should be set to 00 even with this kind of volume control? If not, what should the setting be?

Thanks,

Ray

Yes, that is the best type of Master Volume read-out to have, because it allows 00 to be selected as an easy to remember "reference" point.

If your Master Volume doesn't read out this way, you have to arbitrarily select some number on the display to calibrate against and remember that number as being Reference Level. My old Kenwood AVR was that way -10 was RL or something like that.

Doc

reeltrouble1

Hey Doc or any calibration experts,

I just hooked up a DVD audio player to the rack. The DVD player has a screen to set speaker size, Db level, and mps for the analog 5.1 channel. Should I calibrate for DVD Audio using this test tone for Multi Channel? What speaker size are you all using for DVD Audio? Will I screw up the prior calibration I did for HT with the AVIA disc? Is it practical to set the mps distance for each speaker or will the A/V double filter the distance since it is set also? It would seem so but I am not sure? The DVD Audio sounds pretty darn good.

Tour2ma

rt,
Unless you feel your DVD player's processor is better than your AVR's, I believe you want to just use it'a digital output and do all the processing in your AVR/ AVP.

fireshoes

Can't use the digital coax or optical for dvd-a though, Tour.

I would hope that you wouldn't need to calibrate it differently for the dvd-a player anyway.