Help with calibrating 5.1 speakers with SPL meter

[ajinkya]

Hi,

I'm trying to tune my system with Chesky's 5.1 Audio Sampler disc, which has inbuilt Dolby test tones to help calibrate the sound pressure levels (SPL) from each speaker to be around 75 dB. I'm sure all those who've tuned their systems are familiar with this procedure. I'm using the recommended RadioShack SPL meter with all settings done.

The setup:
I have my DVD player outputting to my AVR Ext In via 5.1 analog cables. In other words, the DVD is doing all the decoding; the AVR simply outputs to the relevant speakers. So I set all distances/delays and speaker volume levels on the DVD itself.

My only question is the following:
When I need to get 75dB on the SPL from all speakers, at what default volume level should I keep the AVR at? If I increase the volume, while keeping the speaker volume settings on the DVD player the same, the SPL goes up, as it should. So what reference does one use here? What is 75 dB measured against? I am lost as to what reference level all these tests measure against. Most web articles explaining the setup do not mention this so I'm looking to the forum members for help.

Thanks,
Ajinkya.

 

[ajinkya]

I think I understand the process now. The idea is to make all speakers sound equal in volume, so the main volume (reference) of the AVR is immaterial. However, I'd still like to know where the number 75 dB comes from

 

[venkatcr]

Ajinkya:

Did you read my article on Wattage vs Decibel on http://www.hifivision.com/speakers/2250-small-query-regarding-my-setup.html ?

Does that answer your question?

Let me also do some research on the levels used for setting up AVRs using SPLs.

Cheers

 

[ajinkya]

Venkat,
Yes, I did read that informative thread. I had also responded with a further query:

"Venkat,
Thanks for the detailed answer. There is one question I still have: The -db levels on most receivers I've seen are quite loud in sound output. So I think the 0db level for these is calibrated at a different level than ambient surround levels. Denon, for e.g. has a volume range from -80db to +18 db, which is asymmetrical about 0 db.
Does anyone have an idea of what 0db corresponds to for such receivers? "

It stil does not give me a direct answer to why 75dB is used as a baseline...by your thread that SPL level should roughly correspond to a passenger car at 1m...I don't know why that's a reference benchmark

 

[audiodelic]

Easiest straight forward way is...

You set your avr volume of 0db and set individual channel gains accordingly till all channels read 75db on the spl meter.

Once this is done when your watching movies on your HT, 0db should be your reference level to run the system at. As you exceed this 0db volume just be a little cautious that you are going above 75db.