Subwoofer Calibration Question

[whmacs]

Hi All,
A real quick sub calibration question. When calibrating a sub using the test tones (or a test disk) is it best to leave the sub's speaker adjustment level on the processor at 0db and use the sub's volume control to get a 75db reading on an SPL meter or; set the sub's volume to say 1/2 way and adjust using the sub's speaker adjustment levels on the processor assuming that you are already calibrated say the left front speaker (to 75db) and have the processor set to the correct master volume level?

Thanks,
Stephen




My Home Theatre

[brucek]

Quick answer to quick question....

I would recommend this method:

When calibrating a sub using the test tones (or a test disk) is it best to leave the sub's speaker adjustment level on the processor at 0db and use the sub's volume control to get a 75db reading on an SPL meter

brucek

[aud19]

ditto

Jason




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[Bam!]

Hi Brucek....

Just curious....Why?


Take care




Bam!

[whmacs]

Hi Guys,
Thanks for comfirming that.

cheers,
Stephen




My Home Theatre

[Aussie Geoff]

Bam!,

Just curious....Why?

The main reason is to avoid possible clipping on the sub output. Sub levels are high any how (reference is 115db compared to 105 db for speakers). So if you (say) set your sub outout at +10db this is 10 times the power (ie 1V becomes 10V or something like that!) and you can clip either the processor output or the subs input on loud bass by exceeding the tolerance of the line level amplifiers. In reality however , up to +3 dB (double the power) is usually fine.

Also Processor bass processing is very complex with redirection from lots of speakers at once as well as the LFE channel. There have been reports of some recievers and processors over the years getting the relative redirected bass level wrong when calibarated with the sub-setting other than 0db. For example there was a long running thread on HTF on this for the Denon 3802.

Generally accepted "good practice" is to calibrate with your front left and right and the sub set at 0db and offset the other speaker levels up and down from that.

Hope this helps

Geoff

[Chris D]

Yeah, that's how I've always done it, Geoff, setting mains and subwoofer to 0 on the receiver. Then adjust the sub with the manual knob on the sub itself, and the other speakers with the receiver's adjustment menus.

Not sure why I've done it like that, but it gave me the best results.

Just to be clear, even if the sub's reference output is different than speakers, all speakers and subs are still calibrated with a constant reference volume. Most of the time, they should all be calibrated at the THX theater reference volume of 75db.




CHRIS
Luke: "Hey, I'm not such a bad pilot myself, you know"