Axiom Home Page Forums General Discussion Home Theater Reference Level

This topic comes up often. This is my understanding of it.

You start with an input signal from a reference disc, -20 dbfs. That input should lead to an output of 85 dbs. At your listening position. If you do that then the loudest part of the movie should be 105 dbs.

Sometimes members talk about reference level as 0 or such on an AVR. But reference dial number will be different based on the room, the speakers(location and sensitivity) and the location of the listener.

Reference level is loud.

Add to this if you know more or if I am incorrect.

If the auto setup has been run using a mic at the listening position (or a proper manual calibration has been performed), -0 dB will result in reference level output. The setup takes into account the speakers, room, and listening distance.

I can't try this right now because my wife is home. But tomorrow I will give it a go.

Chris, I'll add that the built-in test tones on receivers(and some separate discs)are 30dB rather than 20dB down from the full-scale 105dB level, so the calibration for reference in that case is done at 75dB rather than 85dB.

Then, as Chris Neon points out, the "0" level on the main volume control doesn't mean the same voltage output is occurring in all cases. The automatic or manual calibration adjusts the voltage output at 0 to take into account all the factors you mention so that the desired 75dB or 85dB is achieved at the listening position.

You had almost six weeks to have thought of this and done it at any hour of the day or night. Now I have to wait for the result. Ha, I just typoed "result" as "reslut." I'll have to think of a good definition.

Dang. I can't do the experiment because My friend has my meter.

Here is a small blurb about it at THX.

http://www.thx.com/consumer/thx-technology/thx-reference-level/

Neon,
if you do a manual setup, how does the receiver know what reference is? Can you zero out the volume knob in a menu somewhere?

I can't even image listening to a movie at reference level, and I like things loud. I find that in my room, with my setup and calibration, -19 up to about -15 is where I like to listen, my family is more in the -23 to -25 range. I turned it up to 0 before and I would have a killer headache after probably 30 minutes of a good action flick.

if i were to listen to movies at levels of -20 to -25 dB rel. to Reference Level, i would often have a hard time understanding dialog.

to compound the problem, it's not every Blu-ray movie where they normalized the audio level to "0" (reference level) with a 0dB normalization offset;
good examples:
LOTR Extended on Blu-ray plays good at -7dB.
Inglourious Basterds plays well at -9dB.
Black Swan plays well at -10dB.
if you have any problem playing the above at Ref. Level, try these.

those 3 movies would be intolerably loud if played at Reference Level.
i can't see any good reason why they offset the playback level like this.

Some that play very well at Reference Level (all Blu-ray):
Super 8;
Godfather collection-the Coppola Restoration;
Hanna;
The 3 Bourne movies;
Saving private Ryan;

the only times i had headaches watching movies or listening to music was when i was upgrading my audio system and it was not calibrated.

I get headaches watching movies or listening to music when they suck.

Maybe I should recalibrate and re-listen to The XX again?

Lampshade said: "Reference level is loud."

i know some people think Ref. Level is loud because they say
105/115 dB sound are very loud, but the fact is those levels are only heard once in a while. Some even say that watching a movie at 115 dB is very bad for one's hearing, when in fact we are often subjected to noises above 100dB in our daily activities and we don't use or need ear plugs because those noises are very transitory. it's the same for movies, those peaks are very short lived, so there is no danger for the ears.

who would believe that there is a scene in Super 8 that measures 117 dB's and we're not even aware of it, because it does not sound very loud, being of short duration and way down low in frequencies;
it's when the "alien" pushes the bus on the road.
if the same sound was to last for many seconds, then it would seem much louder to our ears.

distortion in the reproduction or a very reflective room can make it seem like the sound is much too loud to bear.


those numbers (105/115 dB)are the maximum allowed, and the great majority of the time, the levels will be much lower, oftentimes even at the barely heard levels, like background noise like clock ticking, soft wind that makes tree leaves move on the ground...etc.

so, we should say that 115 dB CAN be loud, it depends...

I mostly agree, JB, but a transitory sound of sufficient DB can certainly impair one's hearing, temporarily, or forever. Take a sledgehammer to a cast iron bathtub in a 5 x 6' space w/o ear protection and see what I mean. A plam-nailer in a 2' crawl space can be pretty awesome, too!

i (mostly) agree with you too. ;-)

Well, crap! That's no fun, JB! Where do you suggest we go from here?

my suggestion would be
1: to have a good time watching/listening to movies at "realistic" levels, cause Reference Level is not always adhered to by the publishers.
2: petition those publishers in order to get the real Reference Level in every movie.

Sorry, JB, that's not what I meant. What I was implying is that there is no fun if we mostly agree, so what to do about that? How do you feel about NAFTA? (Kidding, please, kidding!)

sorry Bob, but i've tried and tried and still can't understand the humor in this. :-(

what i can say though is that i don't feel anything about NAFTA, but i do feel about the GF. good enough for you? ;-)

JB, the correct answer would have been "No Bob, you're wrong".

JB, do not fret. You are in the company of some excellent people. Oh, no no, not around here, of course, but nonethless.

Yes, it was correct for Joe to call me "wrong." Thank you, Joe.

I think that there are variables here that are still somewhat dependent on other factors. It is mentioned that that the studios don't follow the same exacting practice when mixing. Well shoot, aren't they the ones that we are trying to model? That sucks...

Also, I am starting to wonder if Audyssey (for me anyway) sets a realistic level for "reference" when used. By that I mean, in an uncalibrated system "0" means nothing. Take a pair of M80s, play them at "0" in a 10x10 room, and hang on... Put those same M80s played at the same "0" level in a gymnasium, and (besides horrible echo) it is much more tolerable because of the volume of air to fill with sound.

So I wonder if my Onkyo 709, when I calibrate it with Audyssey, it creating a "proper" '0' reference level, and adjusting the volume up or down to get '0' to be at the right level for my room? I don't have a SLP meter, so I can't check it myself.

With typical total harmonic distortion levels (claimed levels) for consumer AVR's being about the same, "0" gets uncomfortably close to clipping. At that level, mine so overloads the room that I can't even tell if there IS distortion.

what Audyssey does, when you calibrate, is adjust the gain in all channels so the signal levels at the MLP is 75 dB for each channel individually. I've checked this after calibration with a precision SPL Meter, and the individual channels all play back at 75dB when using the AVR's test tones.
if your room is very large, then Audyssey will want more gain in all the channels so that the sound level at the MLP is 75dB SPL. it demands more power from the amps in order to get this level at the MLP compared to...

if you room is small, then Audyssey will want less gain in all channels so the signal level at the MLP is 75 dB SPL. it demand less power from the amps in order to get this level at the MLP.

Smaller space = less power for the same SPL.

this gain adjustment inside the AVR is like a preamp preset (for every channel) that supplements the master preamp volume control.

this has nothing to do with good or bad sound, only with individual channel levels.

in an uncalibrated system, there is no Reference level, but only Preference level. for someone with a good ear, the two will often coincide. it's more difficult to get right because one has to keep making volume adjusments until the right volume level has been found.

is your sub well calibrated or is it running very "hot"?
do you have some sound treatment or is the room "live"?
a live room will be worse sounding as SPL goes up and at a certain level it will not be listenable (horrible).
are your amps clipping?
are your high frequencies adjusted to "flat" or Cinema?
Are you sure that it's not the sub "pressurizing" the room?

any one of these, or other things, could be the cause of your room "overloading".

i have about 3000 Watts, some of which are used to produce sound levels up to 115 to 117dB SPL in my small room (about 1300 cu.Ft.)and the sound is crystal clear. obviously, only part of those Watts are ever used; the rest is insurance in case i move to a large room someday.

Thanks J.B. I was wondering if that wasn't the case since the first thing that Audyssey does is ask you to manually dial down the sub to 75dB...

You also make the same point that I suspected, that it bumps up or down the channel volumes to compensate for room sizes.

Maybe I'll have to pop in Super 8 tonight. I've been dying to see it and my oldest daughter has been begging to watch it, so it would be a win-win if I can get them to watch it at a louder level.

Bob, I can play "above" 0 and still don't get distortion or clipping. Granted, this is only for short periods of time, but I've tried it.

All great points, JB and Nick. I guess what I'm saying is that I have no pressing desire to "go there," not for a movie, anyway. I'm using 1/2 the total power of JB. I sit about 7 feet from the center, about 9+ feet from the mains (M60/4 QS8/ep500).

For movies, 14-17 does just fine. I listen to most pop/rock music at about 14-16 (2-channel 95% of the time), depending on the recording. It's not that I hear detectable distortion at higher levels, I guess I don't need more to rock my plimsole--- in the house. It just gets assaultive past that point, because we're not talking "peaks," but rather whole tracks at full throttle levels all the way through. It'll never be a rock show, so I'm not really trying to recreate it. Though I DO wish that the sound quality and gain of some classical recordings sounded like the orchestral parts do on blu ray.

Surround is awesome for movies, and merely OK to me for a concert video. SACD is against my R & R philosphy (belief system?). R & R live is a plain ol' 180 degree, full-frontal attack. Timbre and room acoustics don't have much to do with most places I would see live R & R, large or small, certainly not in a club-sized venue. I would love surround for orchestral music or jazz, but I almost never listen to either, because they're too soothing and all the pianissimo parts take too long. I'd rather listen to a ballet than sit through an opera.

By the early 70's, decorum and contemporary music parted ways for good and I didn't let that train leave without me.

It's the same feeling I get when I've got ye olde Snells blasting away in my shop. If I drop something near them and bend down really close to the speaker to pick it up, I almost get nauseous. That's because I'm almost always at about 95 db @ about 6 feet.

I guess there's another factor at play. When I had a Hammond and a Fender Rhodes and an ARP, I could tolerate any volume, as long as those brilliant sounds (obnoxious atrocities) were being gifted to the world (committed) by me. It's amazing how loud you can bear things when the one making the noisefest is one's self. It's the only thing that Blue Cheer got right!

I guess its time to reslut.

Do you mean + or -? I'm listening in the range of -14 to -17 as well. When I checked, reference was at around -12. This is after using audessey for level and distance calibration.

My daughter keeps telling me to turn it down when I get close to -14. She would be much happier at -20.

There is also Absolute volume(82.0)numbers go up until reference level, and Relative (0.0), I prefer absolute because it's closer to decibal and my Onkyo says when ref. level is on(lights up) but I agree....too loud.

On my Pioneer it plays pink noise (your wife would like that) at what is supposed to be 75 dB, you can adjust the individual channels trims so they read that on the meter, then the system is calibrated.

On my old Sony the main, left and right, didn't have trims, the center and surrounds were relative to the mains. So you'd enable the test tone, and turn the volume up until the left channel was producing 75 (or 85) dB. Then you'd cycle to the other channels to adjust them the same. The volume control didn't have a dB scale at all, it was just a big knob. So you'd never know when you were at reference level.

Sorry, Fred, yes, minus 14-17. I have 2 Onks, both w/ audyssey. The 7.1 reads from -82 to +12. The 5.1 starts at 0 and goes up to 82. Cd's also seem to be getting "louder." With new releases by some bands two years ago, I would top out at -14. Now there's new stuff that I can't listen to much above -18.

Hi Neon,
I get the calibration part but I still don't understand how the dial reads 0 when done manually.

Thanks.

Hey guys, we're actually talking about audio! Almost even Bob.

If doing it manually then just make sure the dial reads 0 first, then you adjust the level of pink noise from each channel to 85db, 75db, 65db, or whatever db you want "0" to be.

The receiver should automatically set the dial to 0 whenever it outputs pink noise for channel level calibration purposes.


edited for spelling

Chris, when the calibration is done manually(definitely not my preference)the changes in level of the various speaker channels to get them equal is accomplished by changing the level trims which change the amount of voltage each channel gets at a given master volume control setting. That main setting, 0 or whatever, doesn't change at all during the calibration.

Ok. So simple. Just couldn't wrap my head around it. I think because my source of pink noise was from a Blu Ray disc not the receiver before I got my most recent amp.

nickbuol, how did it go watching Super 8 ?

i hope you weren't hurt in the train wreck.
please tell us your impressions of the movie and how your system took it and delivered it.

Alas, my daughter did other things and I couldn't talk my wife into watching it without her (my daughter). So I compromised and let my wife pick. We watched The Next Three Days. Not a bad movie at all, but not something with an amazing soundtrack. Maybe tomorrow night. I think that we all will be home.

To put noise levels into perspective....

Noise levels in excess of 90 DB, for an excess of 8 hours, will result in permanent hearing loss. It is for that reason that hearing protection is required (OSHA) in industrial facilities where a noise survey has concluded that personnel could be exposed to noise levels in excess of 84 db. A peak, one time exposure to a noise level of 140 DB will also result in permanent hearing loss. Exposure to noise in excess of 100 DB for a duration of 2 hours will also result in permanent hearing loss. Double hearing protection is required when employees may be exposed to 140 db peak and / or 100 db over 15 minutes duration (OSHA).

my SPL meter can measure average SPL for any length of time, as long as the batteries don't run down, something like 60 hours if i remember right.
some day i will measure one of those "noisy" movies to see...
maybe Saving Private Ryan. Or, what about "The Mouse that Roared", that would be great, right?

for now, my guess is the majority of movies would have average levels of some 80-85 dBC SPL.

i think the measurements should be done with the "C" weighting; if anyone knows otherwise, pls tell me.

I didn't like nor hate Super 8 but the train wreck scene is fun. I was using it to test my HT out. First really loud scene I have played since I got the basement done. Anyway my twin, two year old girls were upstairs running around looking out the windows trying to find the train. Priceless LOL!

if the whole neighborhood wasn't looking for the train wreck, then it means you need lots more subwoofers.

indeed... it's on my list