Axiom Home Page Forums General Discussion Home Theater What is "reference" volume?

Hi all, I'm turning to the Axiom Wikipedia again for understanding...

When reading through various articles on speaker reviews, etc., one often sees "reference volumes" mentioned. i.e. "We did all testing at reference volume -10db," etc.

My question is... what does this actually mean? Is there an actual reference volume in dB, or is the -10, +5, etc., just a measurement away from 0 dB on your receiver's gain control?

For example, I've calibrated the speakers in my HT to 75db using an SPL meter. When I watch movies, I usually watch them at -20 dB on my receiver. Does this mean I'm 20db off "reference volume?" If so, does anyone actually listen at reference volume? It would seem like you'd blow your ear drums out listening at that level (making the gross assumption that I've set things up correctly in my home theater at least).

Thanks in advance, looking forward to the discussion.

Jason

There isn't a universal reference volume. If you usually listen at 55dB, then you should calibrate your system at 55dB.

I calibrated my system to 75 db, but most DVD's, TV, and games require about -25 db on the receiver to have a 75 db output. HD DVD's require about -15 db.

so 'reference volume' has nothing to do with what the receiver says (-30 db, -15 db, ect.) but the average volume you would see with an spl meter?

so regardless of what my receiver says, if I am watching a show taht makes my spl meter say '75 db' then I am listening at reference levels?

Is that correct?

Well, Mojo keeps saying that the 60s and 80s sound very similar only at or near 'reference levels', with the implication of high volume. So, would reference then be the unfettered volume the CD was recorded at?

Each movie theater system provider have their own test to help calibrate a sound system so it plays "as intended". Dolby, DTS, Sony, etc... If you have an Avia disk, it usually comes (at least mine does!) with some test tones so you can calibrate it for Dolby's standard (mine is at -2db on my receiver for Dolby's reference level in my sweet spot).

Unless you have a lot of background noise (your ears automatically adjusts to compensate), Movie Theater "reference level" is quite loud (at -4db, somes scenes from LOTR-Return of the Kind reached 112db).

As for music and stuff, "reference level" comes from some typical test signals (on tapes or CDs) that were recorded at specific "levels" so you can calibrate. But I doubt they are very coherent among themselves (I could be wrong!).

To "reference level" one must replay "reference to what?"!

The dB references on your receiver are not related to SPL. Decibels are used to express relative levels of any unit (ie. SPL, voltage, current, and even apples if you want). The dB levels on your receiver are likely referenced to the receiver's maximum output voltage. The relation is 20log(Vout/Vref). On my Denon for example, I can get 19 Vrms out at 0dB. At -20, I get 2 Vrms out. 20log(2/19) is -20dB. How marvelous, eh ? BTW, my "normal" listening is at -20 (and sometimes even less than that). And now that you have my sub comparison, you know that my "night" mode is -30.

I'm not totally sure about this but as one approaches 0dB on a receiver, the output signal is more likely to distort. Once you click on the link below, scroll wayyyy down and you will see the start of distortion on my Denon at a level of -2.5dB with a 50Hz tone into a single M80. Not bad distortion mind you but distortion nonetheless.

Theatre reference levels are 85dB using "good" pink noise. Home reference levels are 10 dB below that. I don't know how these levels were established. -20dB on your Denon doesn't mean you are operating at a nominal of 20dB of SPL below your reference. In my environment, -20dB on my Denon results in a nominal SPL of 75dB for music. I can't listen to music at much more than this nominal value. It is simply not comfortable for me. I can handle transients far above that no problem but not continuous.

I don't know if that helps. Maybe someone can explain it better than I can.

http://www.axiomaudio.com/boards/ubbthre...true#Post170686

All this time and I never really thought about how taking the volume from -30db to -20 db didn't increase the spl by 10db.

Funny you should mention that. It may actually.

Going from -30 to -20 gives me about 9x more power on my Denon. And that does increase the SPL by ~10dB. But above -20, that relationship breaks down due to the way in which the gain is calibrated.

Ok, so -30 to -20 is not the same increase as -20 to -10.

Gotcha.

Jason, the term "reference" isn't used consistently in audio. The application that's most consistent is audio on video DVDs. The sound level on movies is supposed to reach a maximum of 105dB on brief peaks(10dB higher on the .1 LFE channel usually played by a sub)if the receiver volume level is set at the number(often 0)used when calibrating. Most calibration test tones are set 30dB below the 105dB peak max(i.e., 75dB; some discs have the test tone 20dB down at 85dB). No, very few listeners find that constantly using reference level is comfortable in a home invironment, and set a significantly lower usual level, assuming that they calibrated accurately, or used an auto-calibration feature which is generally quite accurate.

CDs and other audio discs have no similar standard reference level and the music often needs substantially different settings on different CDs to listen at a similar comfortable level. An average level which is loud, but not dangerous to hearing, shouldn't be more than about 80-85dB. For typical listening that level could well be reduced 10dB or so. An SPL meter, especially with the max and other settings available on the digital RS meter, is helpful in determining actual levels.

When I run the calibration tones from my Denon, they produce tones very close to 75 db. I think Avia's maybe give me 85. Can't remember which is which. I then adjust so all my speakers hit 75. (OK , I actually give the center an extra 1 db and the surrounds 1.5 as this seems to work best for me.) Some would then say 75db is my reference level.

Now when I actually play music or movies where I want to enjoy the dynamics and my wife is not asleep, the dial is most often set at -25. If I recall, this often gives me an average sound level of 75 to 80 db. However, this seems to vary from DVD to DVD I have. This works well for me for most movies and music.

If I'm showing off, I might try for an average of 80db. This normally gives me some very loud peaks but they rarely breach 105db. I don't enjoy stuff over 105 except in very short bursts. I have seen it reach 115 at this setting a few times though. Pretty cool as long is it doesn't last too long.

I might be admitting extra nerdiness but because some DVDs seem to be recorded at different levels, I actually used a sharpie to mark the optimal volume dial setting on certain DVDs that I use for showing off to friends. That way they are not effected by me going louder or softer as I try to find an impressive but comfortable level.

My point? Almost forgot. I think I just wanted to mention that because CDs and DVDs are often recorded at different levels to begin with, you will never be able to put away the volume remote because it will always need adjusting, even if you know your 'reference level'.

Hi guys:

I was confused about the reference level and am still not sure I fully understand it. I believe that when you play the calibration level (pink noise) through the receiver it is adjusting the 0dB level on the receiver to 75dB sound (in your room). When I play the calibration signals on my Denon, the receiver is automatically setting the "volume control" to 0 dB during the calibration. This is actually indicated on the front display. I never noticed until it was pointed out to me and I had to look closely at the display to see the 0dB setting.
The calibration allows the receiver to detect the recording levels of a DVD, automatically adjust (offset)the receiver for different recording levels and thus correct for these differences.

The 75 dB output of the calibration signal at a volume setting of 0dB is a way of calibrating the receiver. It does not mean that when playing a DVD the speakers will output 75 dB if the volume level of the receiver is set to 0 dB. Far from this, setting the volume to 0dB will generally produce ear-splitting sound.

From what I understand, none of this is applicable to music. This because music recording is not standardized and the level at which any particular CD, SACD or DVDA is recorded is highly variable.