Got a question for all you smart people

I just received a 990/7700 combo and am in the process of setting it up. I normalized the speaker level with a SPL and the 990 internally generated test tones.

I assumed that this normalization would hold true for any pink-noise source. But when I checked my work with Avia disk's pink noise I got radically different results (in the order of +/- 6DB for some of the speakers).

Why is this? Which tone set would you recommend I utilize, the Avia DVD or the 990’s internal test tones.

Thanks for your help

-Peter

That is puzzling. I used the test tones in the 990 to configure mine with the use of a Radio Shack SPL meter. Then I used the test tones from a test DVD and the difference was less than 1 db. My test disk is not from Avia. It is one that Sound & Vision Magazine sells. I think it was made by Ovation. It has test tones encoded in both Dolby Digital and DTS and I tried both. Are the test tones on the Avia disk encoded in Dolby Digital or DTS?

If your SLM is a type 3 (survey) instrument, +/- 6 dB is within the error band of the device. If type 2, you should not see more than 4 dB difference.

Could be differences in microphone placement when you change tones, assuming you might move the SLM. You could see standing wave, destructive or constructive interferences.

If your SLM is reading in C scale and not true flat response, the difference could be due to a difference in low frequency energy between the test tones since the C weighting scale is not flat. Dumb response here. C and Flat shouldn't matter if the test tones are different only in low frequency energy. Each will detect a difference using the same instrument and weighting.

Just some guesses.

Del

The Avia disk is also made by Ovation. I am not familiar with the Sound & Vision Magazine disk, but if they both come from Ovations I would be not be surprised find that the only differences between the two was the number of test available on each disk. I would suspect (with out any confirming data) that the tests that where presents on both disks where identical.

pkafka,
I was just throwing my 2 cents worth in another thread (in the saloon) about this very topic.
Personaly, i start w/ the 990 test tones and then fianlize w/ video essential disk in the DVD player. To me, this includes the entire audio path.
I do see a difference - a couple of dbs in one or 2 channels only.
i would not be surprised one possible difference is in the quality of components in different DVD players.
i'm out of here....

There is a bug with both old and new firmware (I haven't tried the latest though which presumably fixes only 12dB sub offset.)
If the Tone Defeat is set to OFF, there is 6dB (or more?) difference between the fronts (fronts are louder) and center channel when calibrating with internal noise. If Tone Defeat is ON the unit calibrates fine.
Anyway, see if you are stepping on this bug.

Asx:

I used the auto calibration option (it's always worked fine for me) to set the levels. I did it with Tone Defeat "on". Does this then mean that if I turn Tone defeat "off" (add some extra db of base for example) my fronts will now be 6db louder than they should be in relation to the center level? And and if so, would they return to their proper levels again by turning Tone Defeat "off"?
I suppose I could experiment...

Asx,

Thank you for the hint I will try it with the Tone Defeat set of On and see if that resolves my issue.

I don't know if auto calibration has the same effect as I never even tried to auto calibrate. I alwasy use SPL meter. You can try it yourself and inform us about your findings.

As of louder or not, as far as I remember the fronts become louder during calibarion, so in effect they will become softer when played normally and it's rather the center channel that becomes louder. Also, you don't even need to add any offset to bass or treble. Even if they are left at zeroes, it's enough just to set the Tone Defeat to Off.