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SPL speaker calibration...not so simple??


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#1 of 9 OFFLINE   Mike_T_

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Posted January 12 2004 - 02:47 PM

I always thought this was cut and dry, and easy to do. However, after updating my Rotel it seems very loud when I listen to movies at 75dB. Here's how I calibrate...please tell me if I'm wrong.

I take the AVIA DVD, and run a test tone on my LF speaker. I turn up the volume on the Rotel until it reads 75dB on the meter, C weighting, slow... Then, I make note of the volume setting for future reference. I then make sure all other speakers/sub match that decibel reading as well until they're all equal.

I only go to 75dB because 85 seems way too loud. However, now even 75dB seems too loud using AVIA. I understand that AVIA intends users to calibrate to 85dB. Does this mean that I should calibrate to 85dB using Avia, and then simply turn the volume down until I reach 75dB and remember the volume setting for movies etc?

I've run several searches on this forum and can't seem to find a concensus...

Thanks!

#2 of 9 OFFLINE   James_Roberts

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Posted January 12 2004 - 03:00 PM

I have yet to calibrate my receiver yet, but the way that I understood it was that you set your volume to the 0 db mark. Then in the receivers menus set each speaker so that it is what the particular calibration source wants, 75db as you say. Then, 0db is refrence level, and everything less than that is that many db less than refrence or over refrence.

#3 of 9 OFFLINE   Tom Vodhanel

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Posted January 12 2004 - 05:16 PM

Hi Mike,

There is a good *how too* written by Guy Kuo in this link.

http://www.svsubwoof...m/faq.htm#meter

If you print out his text and keep it close when you are using AVIA, it really makes things go smoothly..Posted Image

Tom V.
SVS

#4 of 9 OFFLINE   Edward J M

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Posted January 12 2004 - 11:57 PM

If you want to calibrate your system to Reference Level, set your Rotel Master Volume to 00 and adjust all channels until they are reading 85 dB, if you are using Avia. For the subwoofer, try anywhere from 85-87 dB on the meter. Using the 90 scale will result in less needle fluctuation. 85-87 dB on the meter will result in a 2-4 dB "hot" calibration on the sub.

Remember, calibrating to Reference Level doesn't mean that you have to PLAY at Reference Level. You can play your system at whatever volume is comfortable and pleasing to you.

Dolby Reference Revel is defined as 105 dB bass peaks from any surround channel, and 115 dB bass peaks from the LFE channel - as measured at the listening position. The reason the LFE channel is higher, is because your DD/DTS pre/pro automatically boosts that channel 10 dB.

There is one variable on the whole RL concept, and that's the actual DVD mastering level. I wish I could say that setting the Master Volume to 00 after RL calibration with Avia or S&V always yielded sound pressure peaks of 105 dB in the surround channels and 115 dB in the LFE channel every time for every Dolby Digital DVD, but it just isn't true. Some DVDs are mastered very hot, and other ones are not.

So ultimately it's best to view RL calibration more as a standardized benchmark for enthusiasts to compare Master Volume settings on playback than to view it as an absolute playback level, because we can't control the mastering level in DVD movies.

The only way to really be sure you are playing back at true Dolby Reference Level is with an SPL meter at the seat (and correction factors if the meter is C-weighted). Most of the hot bass peaks on DVDs are in the 25-30 Hz region, so I would suggest using an average correction factor of 3-4 dB on C-weighted Fast. If you are hitting bass peaks in the 113-116 dB region on the meter, you are very close to true Reference Level.

Most subs can’t cleanly hit true RL at the seat, and many enthusiasts find it far too loud for comfortable playback anyway. Personally, I play back most of my DVDs at around 10 clicks under RL (but some as low as -15, and others as high as -5).

Regards,

Ed
Ed Mullen
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SVS

www.svsound.com

"What we do in life, echoes in eternity."


#5 of 9 OFFLINE   terence

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Posted January 13 2004 - 12:38 AM

Just to be sure I'm right here. Since Ovation Solfware made the Avia disc and S&V is also made by them.

Do you calibrate at 85db for all ch on the S&V disc or is it 75db for all ch on S&V disc?
Tee

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#6 of 9 OFFLINE   Mike_T_

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Posted January 13 2004 - 01:09 AM

Thanks guys...

How do you set your master volume at "00dB"?

#7 of 9 OFFLINE   Chriss M

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Posted January 13 2004 - 03:37 AM

Rotel doesn't use the 0db volume scale so you won't be able to do this.

Your volume scale probably goes from 0 - 85. You can arbitrarilly choose a number (try 65 or 75) and then adjust the individual channel levels so that the avia test tones read 85db on your meter, with the rotel's master volume set at the number you chose.

#8 of 9 OFFLINE   Roger Q

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Posted January 13 2004 - 03:44 AM

Not sure about S&V, but with AVIA you should calibrate to 85dB. Whatever level you master volume switch says at this calibration level is reference level.

One of the reasons for calibrating at such a high level is to improve the signal-to-noise ratio. And afterwards, as Edward said, you simply put your receivers volume at whatever level is comfortable for you.

If you look around at various posts on some of the forums you'll see that it is not uncommon for many people to listen to movies at -20 db or more below reference.

#9 of 9 OFFLINE   Mike_T_

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Posted January 13 2004 - 08:04 AM

Sounds like I'm making it more complicated then it is then.

I've just turned the master volume setting on the rotel up until it reached the proper decibel setting on the SPL meter..then while staying at this volume, calibrated the other speakers. I just didn't calibrate to 85db as per Avia's suggestion.