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Stupid ? what does reference level do. (1 Viewer)

PS Nystrom

Second Unit
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Jan 27, 1999
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What about calibrating LFE levels for DD vs dts soundtracks. I have heard whispers that sub settings for the two formats should be different. Most commonly that dts should be set 10db higher than DD. Occassionally that idea is reversed, and somewhere I ever heard dts should be 6db higher, not 10. Are the rumors true? Should the LFE levels for dts be calibrated differently than DD?

I am an AVIA user at the moment, but I have again heard through the grapevine that the S&V DVD contains calibration sections for both dts and DD. Is this true? Can anyone confirm? Thanks,

Pieter
 

Phil Iturralde

Screenwriter
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Oct 7, 1998
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... heard through the grapevine that the S&V DVD contains calibration sections for both dts and DD. Is this true?
It does! S&V HT Tune-up also includes Test Tones for 6.1 = use the same 85 dB SPL like AVIA.

FYI: Dolby's "Explore Our World" includes Dolby Pro Logic, Dolby Digital 5.1 / EX 6.1 & Dolby Pro Logic II Test Tones w/seperate Bass Management Test Tones for each format(s) @ 75 dB

Phil
 

Edward J M

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Sep 22, 2002
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The internal test tones on an AVR or pre/pro, and on the VE test disc, are mastered at 30 dB below reference level. The AVIA disc is mastered at 20 dB below reference level.

The SPL PEAKS on DVD's (which are invariably BASS peaks) are (or are supposed to be) mastered AT reference. Also keep in mind that many DVDs have full range, full power signals in ALL surround channels (i.e., mains, center, side surrounds). Das Boot and U-571 are good examples of this.

So when the AVIA calibration disc (for example) gives you 85 dB at a given Master Volume setting (which will vary with room size and speaker efficiency), you can expect - when playing a DVD - approximately 105 dB bass peaks from any given surround channel (if it is run on LARGE), and 115 dB bass peaks from the LFE channel, all at the SAME Master Volume setting.

We all know about DVDs that are mastered on the "hot" side and by this we mean they actually provide slightly higher than 105/115 peaks at reference level Master Volume setting.

These SPL peaks are all as measured at the "couch" on C-Weighted Fast with a decent SPL meter. If you use the RS meter, add a few dB on bass peaks for the true SPL since this meter reads a bit low in the bass frequencies.

The above assumes the surround channel speakers are true full range units capable of flat response to 20 Hz. If there is a simultaneous bass peak which occurs in a surround channel AND in the LFE channel, there will obviously be some source summing and you can expect upwards of a 120 dB bass peak at the couch in this infrequent (but certainly possible) instance.

If you run all your surround channels on SMALL (and most of us do because we don't have true full range speakers all around), you are asking the subwoofer to produce bass from all the surround channels below the selected filter point AND the bass from the LFE channel. Due to this bass management, the same simultaneous bass hit descibed above would require the sub ALONE to produce the same 120 dB bass peak at the couch.

Clearly, the need for a quality subwoofer (or two) is CRITICAL if one ever hopes to (for whatever reason) reach true reference level playback. Without question, the subwoofer is THE limiting factor in the ability of most systems to playback at reference level. If you are running your speakers on SMALL, and sitting 12 feet from the sub in a typical 2,500 ft3 room, I can count on one hand the number of subs designed for home use that can cleanly hit a 120 dB bass peak at the couch.

John Doran - you are one of the lucky few who can actually pull it off with room to spare.

Regards,

Ed
 

Alex Dydula

Stunt Coordinator
Joined
Nov 1, 2002
Messages
170
Ok,

My Turn!! (Smile).

If I read the last post right, when I set my speakers each via the receiver level control to for 75db at my seating position individually and the sub get a little boost, 78-80db, and then the volume control setting turns out to be -25db.

Then to get the 105 db i must turn the volume up to +5 db (cant do it on my receiver) to get the 105db. (75db + 25db) = 100db, want 105 db for ref level listening??

At the -26db volume level calibrated to 75db the sound is absolutley LOUD. Cant imagine listening at -10 or higher ever??

Seems like the receiver I have is almost spot on?? Out of the box in my room for my distances to the listening spot??

Alex
 

Zack_R

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Joined
Nov 4, 2002
Messages
220
Alex,
-25 is your reference per your receiver test tones. Your sub is probably running about 5 dbs over reference given a the calibration level you listed.
At -26 db you are listening to movies at 1db below reference. So yeah, it should sound loud to you.
Many people, myself included, listen to DVD movies at -10 to -15 db below reference. For you to listen at those levels your receiver would read -35 db for 10 db below reference and -40 db for 15 db below reference.
Likewise, if you were to playback DVDs at -15 db on your receiver you would now be 10db over reference and likely deaf:).
 

Lee Carbray

Second Unit
Joined
Oct 23, 2002
Messages
308
Then to get the 105 db i must turn the volume up to +5 db (cant do it on my receiver) to get the 105db. (75db + 25db) = 100db, want 105 db for ref level listening??
You are in the same boat that John was in. Reread some of Vince's posts. At your volume knob setting of -25Db playing back a movie would get you peaks of 105db. You do not need to turn it up anymore.
 

Phil Iturralde

Screenwriter
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Oct 7, 1998
Messages
1,892
My DD-5.1 REF Calibration SPL Mark is 12 o'clock high** (no digital readout for my Yamaha RX-V995) using Video Essentials / 75 dB (sub = 80 dB / lowest needle swing 79 dB - highest = 81 dB)

Since some DVD's vary in their recording SPL's, I just monitor my new Blockbuster DVD and turn up the Volume until I read approx. 105 dB+ FAST SPL Peaks @ my 'sweet spot' (RS Meter Dial = 100 / Speed = FAST / Weight = C).

** Silk-screen Volume Knob Number

Position .... Number

12 o'clock .. -16 dB

11 o'clock .. -20 dB

10 o'clock .. -28 dB

Just about 95% of my DD-5.1 DVD's that I have, the observed 105 dB+ SPL Volume Knob location is approx. -10 dB below my REF Level (approx. 10:30 o'clock Volume Knob position) when I visually check the Volume Knob location after I'm done AVG the LFE to 105 dB+ FAST SPL Peaks @ my 'sweet spot".

So, during my once or twice Friday NITE DVD Movies, I just dial it @ up to the approx. 10 o'clock - 10:30 Volume Knob position for any new DVD and adjust from up or down from there.

The approx. -10 dB below REF Level is loud enough to move your pant leg, couch, etc. if the DVD encoded LFE calls for it, and still loud enough to hear the whispering dialog during the quieter moments of the movie.

Phil
 

Lee Carbray

Second Unit
Joined
Oct 23, 2002
Messages
308
A question, since there is some good reference level discussion going on here.

Does it actually make sense to calibrate to reference?

Now I am not saying it does not make sense to know where reference is. You need to know where it is in order to compare. But if you do all you listening say -10Db from reference would it not be better to make sure your speakers are calibrated at that level, rather then reference. I would think that unless you had a system with 5 identical speakers, calibrating to your listening level would make more sense.

Any thoughts?
 

PS Nystrom

Second Unit
Joined
Jan 27, 1999
Messages
444
Lee,

I had the same thought earlier this week and decided it made sense. When calibrated at reference level I typically listen to DVDs at -15db. So I figured I'd try (using AVIA) calibrating my system to 70db at -15db on my receiver. Haven't watched an entire DVD since, but I'm looking forward to the weekend so I can test the theory out.

Pieter
 

Phil Iturralde

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Oct 7, 1998
Messages
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I would think that unless you had a system with 5 identical speakers, calibrating to your listening level would make more sense.
Actually, it's just Important to REF Calibrate your speakers whether you have 5 identical speakers and probably more so, if you don't have 5 identical speakers due to the laws of physics (cabinet size, number of drivers, room location, room boundaries, room furniture, etc.)
Since the supplied Test Tones in your AV Receiver and Video Essentials DVD is -30dBFS, for proper Calibration, you set your playback SPL @ 75 dB (RS Meter Dial = 70 dB / Speed = SLOW / Weight = C)
For AVIA & S&V HT Tune-up DVD with -20dBFS Test Tones, you use 85 dB.
It's simple as that.
It's been documented that some AV Receivers systems might drift as much as 2 dB in one or more of the 5.1 channels when you lower the volume from REF Level. If you're concern that your associated AV AMP/Rec SPL levels are not linear when you lower your SPL by -10 dB from the REF Calibrated Level Mark, ... then in those cases, I would recommend that you REF Calibrate @ -10 dB to re-adjust the channels that drifted by lowering the volume from the initial REFERENCE Level Mark! It's easy to check -
1) REF Calibrate @ 75 dB (VE / or 85 dB (AVIA and S&V)
2) Once you're done, run those same tones @ 65 dB (VE / 75 dB (AVIA and S&V)
If your trim levels drifted in one of your channels, then REF Calibrate @ the lower -10 dB.
I've check my Yamaha RX-V995 & Yamaha R-V905 (authorized mail-order version of the RX-V595) linear speaker levels @ -10 dB from REF Calibrated Mark, and my final adjustments for all channels were identical.
Phil
 

Lee Carbray

Second Unit
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Oct 23, 2002
Messages
308
then I feel that it's important for me to follow the REF Calibration instructions and REF Calibrate my DD-5.1 Playback System to equal 75 dB (VE) SPL ... so I can play back and hear my blockbuster DVD's as intended by the Mixing Engineer @ REF Level.
But you only listen at reference level on rare occasions. If your speaker calibration was off at a lower level would it not make sense to make them equal at that level. I think in my mind having the speakers at equal levels at a more used listening level would be better then having then equal at a higher volume that is never used. It is like tuning your race car for a drag race because you do that once a month but once a week you race on a road course.
 

Phil Iturralde

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1,892
But if it did change would you adjust or not?
If the difference was 2dB+ I would REF Calibrate it @ -10 dB and document my results between the two ...
1) REF Level
2) -10 db below REF Level
Then all I have to do is remember to adjust the speaker(s) trim levels as required based on my selected watching / listening levels!!
After doing the above for a few months, ... I would sell my AV Receiver and buy one that maintains the linear SPL speaker levels from REF Level on down to @ least -15 dB.
Fortunately, my Yamaha's don't have that problem, I already checked my 5.1 SPL's @ REF, -10 dB below REF and -15 dB below REF!!! :)
Phil
 

Alex Dydula

Stunt Coordinator
Joined
Nov 1, 2002
Messages
170
Zack, Lee...

Thanks for the replies!! I finally understand it!!! Whooooa!

I found the really only useful thing to me about calibrating was it made me check to see if all speakers were playing at the same level from my listening spot/chair.

ALl theother stuff while very interesting doenst mean a whole lot we seem to adjust the volume to what sounds good and or tolerable to whoever is listening to the movie at that particular time.

I did watch a movie at ref level once and "good gravy lady" was it LOUD and AWESOME at the same time, but really too loud for what my family would accept or tolerate!!

Back to the Movies!

A.
 

Lee Carbray

Second Unit
Joined
Oct 23, 2002
Messages
308
I would sell my AV Receiver and buy one that maintains the linear SPL speaker levels from REF Level on down to @ least -15 dB
Wouldn't it have more to do with ones speakers having different sensitivities? I would hope that most receivers have amp sections that adjust all five channels equally when raising or lowering the volume.
 

Vince Maskeeper

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Jan 18, 1999
Messages
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This is false.

The reason this rumor spreads is a complexity of how a certain feature is labelled inside most receivers. The basic truth is that the nature of 5.1 soundtracks require a 10db boost in LFE in playback-- for both DD and DTS- a boost handled by decoders (no, don't calibrate 10db too high, the processor handles this for you using existing tones from VE or AVIA).

The problem is many receivers have a "defeat" for this 10db boost- often called an "LFE PAD" (sometimes LFE trim). This pad is usually a toggle between 2 settings, which basically amount to "boosted / not boosted".

The problem comes in because in many receivers the DD pad is lablelled -10/0 and the DTS one is labelled 0/+10.

Each version does the same basic thing, setting the required LFE boost on/off- but the labelling means that "proper" settings puts you with DD at 0 and DTS at +10. This seems confusing- and I'll admit I'd still unsure why they have chosen to label things this way- but it doesn't mean an actual 10 db difference between the two.

Bottom line is the "right" position for this LFE trim adjustment (not the same as sub level!)- is all the way up, for both DD and DTS.

This is still a huge source of confusion- and many people are also stilll setting both LFE pads at 0, and then bumping the sub trim up for DTS tracks (when the proper lfe pad position would have fixed it to begin with).

I still need to just sit down and write a book on 6 channel sound calibrations!

-vince
 

Kirk Mango

Stunt Coordinator
Joined
Jul 8, 2002
Messages
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Vince,

I own the REF 30 from B&K. I have never heard of the LFE pad nor a setting that is similar to what you discribe in the above post. The only thing I have in my menu setings is a movie / music setting, and I set it to movies. I am not sure where this LFE pad might be located. I set my system to 75dB (actually 74dB) using the test tones on my preamp with the sub calibrated -2db lower then all the other speakers due to the RS meter problem with low frequencies. The settings are the same whether I play CD, DTS - DVD, or DD - DVD. I have checked this with VE and with my volume set at 0.0 I get 75dB out of all of my speakers and 72dB out of my sub. I am assuming I am calibrated correctly. Yes

KM
 

Vince Maskeeper

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Jan 18, 1999
Messages
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This might be it. Because DTS music discs do not requite an LFE boost, it might very well be a DTS LFE pad in disguise (music position is non-boosted, movies is boosted).

Also, some of these units hide the LFE Pad in some obscure menu- my Denon will not let you see it unless it has a lock to a digital source (so you actually have to have a dvd playing before you get an option for the menu!).

I would say you're probably just fine.

-vince
 

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