Reference level???

**Burke Strickland** · 29 July 2003, 15:11 Tuesday

Originally posted by AudioVideo101.com

Dolby Reference Level

Volume level of an audio system with the volume [control knob] at the 0 decibel setting resulting in 85 decibel volume with a test tone and 105 decibel peaks. Dolby reference level is the volume level used in movie theaters for movie presentations (although this level is sometimes turned down).

The reference level is set using a test tone generated by a surround sound preamplifier and a sound pressure level meter (SPL meter) to measure the sound output or volume. While providing a realistic and enlivening auditory experience, the reference level is very loud and is often turned down somewhat by listeners. However, surround sound audio systems should be set to the Dolby reference level and all channels properly equalized (each channel putting out the same sound pressure levels with a reference signal) even if the system will not be listened to at the true reference level.

These are also the levels prescribed as the THX "reference levels" for THX-certified theaters and home systems.

Originally posted by AudioVideo.com

THX Reference Level

Volume level designated to be used as the standard in THX certified theaters and home THX installations setting volume at 85 decibels when fed a continuous test tone and achieving 105 decibel peaks when the volume control is at the reference 0 decibel setting. The 0 decibel setting is the reference on the volume control with negative numbers being the number of decibels below reference and positive number being the number of decibels above reference. The reference level is set using a test tone generated by a surround sound preamplifier and a sound pressure level meter (SPL meter) to measure the sound output or volume.

While providing a realistic and enlivening auditory experience, the reference level is very loud and is often turned down somewhat by listeners. However, surround sound audio systems should be set to the THX reference level and all channels properly equalized (each channel putting out the same sound pressure levels with a reference signal) even if the system will not be listened to at the true reference level. It is an interesting exercise to demonstrate a home theater system for friends when it is set at the true THX reference level though.

[Emphasis added. The "O db" level refered to above would be marked differently on receivers or pre/pros which start their markings at O and show only positive numbers.]

In practice, if you set all the channels to the same level as measured by the SPL meter when playing a standard test tone, you are setting a "reference level" for your system. It doesn't have to be as loud as the Dolby standard as long as it is consistent across all the channels.

Burke
Spelling and grammar checked in MS Word. If you detect an error, please notify Bill Gates.

**Andrew Pratt** · 29 July 2003, 15:35 Tuesday

Reference levels simply mean that you are playing back the movie at the same volume at which it was mixed at and usually what the director intended you to listen to it at. Of course this is all just a guideline and you're free to listen to it at what ever volume you find comfortable...which for most people is quite a bit below "reference". Your volume reading though means nothing when comparing it to someone elses unless you've calibrated your system against a known volume level. This is usually best done with either Avia or Video Essentials which are both Calibration DVD's that calibrate both the audio and video side of your systems to a started level. If you don't already own one of these fine discs I highly recomend you pick one up as well as an analog SPL meter from Radio Shack. These tools will help bring your gear upto the level its capable of and allow you to get every last ounce out of the equipment. With respect to the reference volumes what you would do is play back the test tones on the DVD that are at a known volume. You then turn up your volume on the the Rotel until your SPL meter reads either 75 or 85 dB (depends on which disk you use). You then simply adjust all the other channels until their volume matches the fronts. You should now be able to turn up your receiver to this volume number (mines at 70 db on the display) and know that you're at the same level as the recording studio and other users. Its also handy when you say you prefer the sound at -10dB from reference since we'll all know exactly what you are hearing at that level even though you have different equipment and a different room then we have.

**Tha Freak** · 29 July 2003, 16:36 Tuesday

I see...a little bit complicated...but I could manage!

I have the S&V tune up disk...is it OK?

If I have this right, I (try to find) buy a analog SPL meter, I pop the disk in my player, play the tone for left channel and ajust the volume until the SPL reads 85db, then I switch the test tone to the next speaker, and with the ±db I ajust it so it also reads 85db, and so on for the rest of the speaker.

So, the reference level is more for the initial set up.

do I get this right?

- - - - - - - - - -

"Are you gonna bark all day little doggy?...or are you gonna bite?
-Mr. Blond in Reservoir Dogs

**Andrew Pratt** · 29 July 2003, 16:59 Tuesday

I have the S&V tune up disk...is it OK?

Yes that's fine. The S&V disc is just a subset of the Avia DVD but for 95 plus percent of the population the S&V disc has all you'll ever need. And actually its got the 6.1 test tones that are missing on the Avia disc so you're ahead of the game in that regard.

Being in Canada you might have a hard time finding an analog SPL meter since Radio Shack only sells the Digital ones up here now :roll: but its not that big a deal. The reason we always suggest the analog one is that its easier to use in that its easier to watch the needle swing around 85 dB where as its harder to watch the digital display jump around from 83 to 87 and so forth...it can be done though.

**Chris D** · 30 July 2003, 00:29 Wednesday

Tha Freak: You got it right. It's really not very hard at all, and not very expensive. I think the SPL meter is like $20 at Radio Shack. I also prefer the analog version for the same reason Andrew said. I personally crouch behind my seat at the main listening position, holding the SPL meter right where my head would be to eliminate my body directly interfering with sound waves, but even that's not really required.

Most people find the reference db level somewhat louder than normal, and turn it down. It's all personal preference, but you'll lose just a bit of detail every time you turn it down. Me, I'm big on hearing the true, original sound of media that the designers intended.

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

**David Meek** · 30 July 2003, 08:13 Wednesday

Huh? What? I can't hear you. . . I've been listening to movies at reference volume for too long! :B

One other comment on reference levels: if I'm not mistaken, aren't you supposed to set your subwoofer output +10 dB (to 85 or 95 dB depending on which disk you use) to compensate for the differences in home vs. commercial theater acoustics? I've heard some HT's that are set like that and the bass is too pronounced (room gain?), but in my room that's what produces the most normal and balanced tones across the spectrum. As always, YMMV.

One caveat here: I'm running a Velodyne FSR-15 sub which is one of the servo-controlled designs. Some people think the bass on these is too constrained, so that might have something to do with my +10 dB preference. I don't think these subs are "too anything", but I do have mine set +10. . . .

David - HTGuide flunky
Our "Theater"
Our DVDs on DVD Tracker

**Burke Strickland** · 30 July 2003, 10:02 Wednesday

I'm big on hearing the true, original sound of media that the designers intended.

I'm big on still having my hearing intact at the end of my listening session. ;>) Reference level is for reference only. A really good home playback system can resolve sufficient detail at lower volume levels to be satisfying as a listening experience and be true to the artists' intent (unless their intent was to make the members of their audience deaf).

IMO, "reference" level is too loud to be comfortable or safe for sustained listening, While some would argue that Dolby and THX would never prescribe a level that isn't "safe" or they wouldn't get away with it legally, by analogy, there is also a lot of processed food on the shelves of the grocery stores that have excessively high salt content and they "get away with it".

Although it isn't healthy to eat a lot of salt, (it can lead to high blood pressure and damage internal organs), it is still legal for the manufacturers to sell their products that are loaded with it for "taste". We as consumers have to read the labels and protect ourselves by avoiding "too much" salt. Likewise, we need to take "reference" levels with a grain of salt, :>) and set our actual listening levels at a sane volume that won't blow out our eardrums.

Burke
Spelling and grammar checked in MS Word. If you detect an error, please notify Bill Gates.

**George Bellefontaine** · 30 July 2003, 11:53 Wednesday

Earlier I used to try listening as close to reference as possible, but it became annoying after awhile to myself, my wife and guests who often felt reference levels in theaters were much too loud. I have my Denon volume control knob set at -15 for most dvds. The DTS track of LOTR though is very loud and I had to cut that back to -20. As for the sub, like Tex, mine is +10.

My Homepage!

**ht_addict** · 30 July 2003, 21:24 Wednesday

I personally pick 0db on my Marantz pre/pro as the 75db level. Calibrated each channel individually to this level. Now when I watch DVD's I usually turn it up to -15db to -10db. This is plenty loud especially during intense scenes.

ht_addict

**Chris D** · 31 July 2003, 00:47 Thursday

True, true.

Me personally, after calibration at reference level volume, I back off the master volume 5-10 db for viewing. But as others pointed out, each disc/TV show varies from a little to a lot in volume, and it requires further adjustment. Some discs are made "hotter" in overall volume, or even just certain frequencies (usually bass) to appeal to the ear.

Funny that LOTR was mentioned--this is always the first movie that pops in my mind. It is VERY, VERY bass heavy. Usually I have my sub turned up a few db over reference due to both personal preference and to compensate for bass-deficient material. But LOTR is one media piece that needs no additional boosting whatsoever.

I just don't like to adjust calibration for individual movies or music.

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

Reference level???

Reference level???

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment