Question: Auto-calibrated speaker levels on the C2?

[jprafter]

When I let the C2 auto-calibrate my speaker levels, it calculates all negative values. This may be because the room is small but I'm not sure. (other’s experience?) It is my understanding that the level adjustment is to bring the 7 speakers and sub to the same RELATIVE levels that the original soundtrack was mixed at. Thus the levels just need to be in the same ratio.

So my question is, after the C2 auto-calibrates, can I change all the levels by the same amount (say 5db) and still achieve the intended result?

The reason I even ask, it seems like there is more headroom when the levels are all adjusted higher. Also it seems like my new Paradigm S8's like more power.

Any information on this would be helpful.

[Peter Nielsen]

When I let the C2 auto-calibrate my speaker levels, it calculates all negative values.

The following affect the values:

-The gain of the amplifier (Note: If the amp is set to THX level, this factor can be ruled out)
-The speaker efficiency
-Speaker distance

Anyway, you really don't have to worry about anything. Negative values are most likely a sign of efficient speakers, which is a good thing.

FWIW, my mains are +2dB, center +8dB, surrounds +0dB, rears +2dB, subwoofer -8dB.

Yeah, you guessed it. Maggies are highly inefficient (typ. 85dB/1W/1m). The Martin Logan sub, on the other hand, is very efficient...

can I change all the levels by the same amount (say 5db) and still achieve the intended result?

You can do that, but then the dB display of the attenuator on your C2 is no longer correct. The reference levels are calcuated at THX reference level. In theory, you should turn up your volume to 0dB to get the "reference volume".

Or to put it in other words; if you change the levels, the dB volume indicator of your C2 will be wrong. "-15dB" will no longer mean "15 decibels below THX reference listening level". You would need to calculate the correct value knowing how much you offset the gain...

Is there a specific reason why you want to change the gain ?!? (I don't understand what you mean when you talk about more power. Surely, you never turn up the C2 attenuator to +22dB ?!???)

Peter

[jprafter]

Thanks for the reply. You have clarified what the intent of the 0db level is on my C2. With that understanding it now makes sense why the levels were being set where they are. As I mentioned the room is small, I have the A21, and A51, so there is plenty of power, and the efficiency of the speakers, the auto-calibration will then level to achieve not only a balance between the speakers levels but also the 0db THX reference.

I went back and compared the sound again. For some reason, which defies the logic, it seems that the bass is tighter and the sound is different at relative volume levels when the speaker levels were adjusted higher. This could just be me however.

Thanks for the clarification.

[Chris D]

Peter hit the nail on the head there. Yes, the most important thing is that all speakers and subs are calibrated in balance to each others levels. However, adjusting them lower than properly calibrated will make the volume level immaterial. 0 db should produce THX reference volume levels in your room, per the Parasound C1/C2 THX Ultra 2 standard.

No problem on the "all negative" settings. My Klipsch speakers are very efficient, so they're all negative, too. The mains are set as low as -13 db.