SPL for Subs re: Video Essentials (1 Viewer)

[Aaron Garman]

Hello all. I use the Video Essentials DVD to setup my A/V system. Is there a trick to setting up the SPL on my sub with the tones that VE offers? I know I set the rest of the system for 75dB, how about the sub? Thanks!

AJ Garman

 

[Vin]

Aaron, in theory, all channels including the subwoofer channel should be set to 75dB when using VE. However, a lot of people will set the sub channel slightly higher, say 3-5dB. Doing this will make up for the loss of low freqency impact (our ears are much less sensitive to lower frequencies) when listening below reference level.

Also, it's a good idea to leave some room for adjustment of the sub output channel from your receiver so that when you do listen at reference levels, it will be very easy to back off on this setting (if you choose to do so) from your receiver's remote.

Hope this helps,

Vin

 

[Harold_C]

However, a lot of people will set the sub channel slightly higher, say 3-5dB.

I would be very wary about recommending this practice.

Just getting the sub to play at the nominal setting is very demanding with a Dolby Digital or DTS source. In most rooms, you are already talking about needing probably 150 watts and a sub that can handle it just to come within a few DB of Dolby reference levels (115 db peaks delivered to the listening location from the LFE channel).

If you crank the bass up +3dB, you are now asking the amplifier to deliver double the power to the subwoofer. Things get out of hand very quickly. Let's say that you listen to movies at "healthy", but not excrutiating, levels (5 to 10 dB below Dolby reference). Properly calibrated, your sub is going to be delivering peaks between 105 and 110 dB. There's certainly no problem hearing (or feeling) bass at those SPL levels.

It's been my experience that setting the sub above where it is supposed to be set starts to very quickly make the sound muddy as the bass fundamentals mask the upper harmonics that give bass its "attack".

I would recommend setting the the sub levels exactly where they are supposed to be (the same 75 dB on the pink noise tones as the other speakers) and living with it for at least a month with various types of recordings to get acclimated to what bass is supposed to sound like when it's not artificially exaggerated. From there, maybe go up or down 1 dB just to see how you like it. 3 dB is a BIG change when you are taking about the amount of amplifier power reproducing the LFE channel requires.

 

[Rick Radford]

Harold,
Good point. I suppose the caveat should be that if you like to listen at reduced volume levels (how many folks really listen at ref level anyway?), you should be safe cranking the sub up 3-5 dB over calibrated settings.
Otherwise, set it at the calibrated level.
I know we listen (at night) around 15-25 dB under ref. (depending on what I can get away with)

 

[Harold_C]

I know we listen (at night) around 15-25 dB under ref. (depending on what I can get away with)

Actually, the best way to handle that would be to use the Dolby Digital dynamic range compression feature.

The reason that we turn down the volume levels is usually because the loud passages are too loud. But, turning down the master volume starts to make dialog unintelligible, particularly on soundtracks where the actors are whispering, speaking with accents, or are masked by background sounds. The whole idea behind Dolby reference levels is to keep normal dialog at realistic levels. I find that anything lower than 10 dB below Dolby reference levels starts to cause dialog intelligibility issues.

The Dolby Digital dynamic range feature is an ideal way to deal with this. Most receivers have two optional settings -- MAX dynamic range, Mid dyamnic range, and Min dynamic range.

In the MAX setting, you get the full monte with the loudest peaks from any single channel as high as 105 dB at Dolby Reference levels. The MID setting should scale the loudest peaks down 5 dB and the quietest sounds up 5 to 10dB. The MIN setting should scale the loudest peaks down 10 dB and the quietest sounds up by 15 dB or so.

This would let you keep the average diaglog levels up where they are intelligible while keeping the level of the loudest sounds that same as if you had turned down the volume another 10 dB.

Using this MIN dynamic range setting would be ideal for your nighttime movie viewing and would let you "get away" with higher overall levels for dialog intelligibility.

There is a separate mode used for devices like cable TV decoders that output a signal on an RF modulated connector. This compression mode applies massive dynamic range adjustment and raises the output level by 11 db. This produces a highly compressed signal similar to that of broadcast TV.

 

[Robert EW]

Harold, that is great information to know. I just happened to find that feature on my receiver this weekend while watching Toy Story 2 with my wife.

What happens if you have it on, forget about it and then calibrate with AVIA like I did. I assume I need to recalibrate, and will, as soon as I can find longer spikes for my speakers. Anybody have a solution for longer spikes?

 

[Harold_C]

That's a darn good question. If the calibration tones were recorded at -30 dBFs (30 dB below full digital signal) which would be used to calibrate to 75 dB output, the compression shouldn't make any difference because -30dDFS is the mid-point that should remain fixed while louder and softer sounds are compressed.

However, the Avia's tones are recorded at -20dBFs for playback at 85 dB. The compression might well change the calibration results.

Actually, Dolby Digital material is generally encoded with MAX compression. If you select no compression, the decoder actually scales the dynamic range UP.

To be safe, I would do the calibration with the no compression setting.

 

[Robert EW]

The calibration I made with the compression on was my second calibration in a week (somehow I defaulted my setting back to zero) and I did not write my first setting down on paper. Otherwise I could tell if it made a difference. This time I wrote my calibration setting down and I will compare them to the new setting and see if it makes a difference. However, I hope to have speaker spikes installed and may not be able to make and apple to apple comparison. Plus I am new to this and do not want to rule out human error.

 

[Rick Radford]

>the Dolby Digital dynamic range compression feature.<
I think that's called Midnite mode.. or something like that on my Onkyo 989.
I've always wondered whether it should be set to max or min (no mid setting).. and now I see it should be min. The OM has little to say about this feature.
I'll hafta remember this next time we watch a movie at night.

 

[Harold_C]

The Pioneer receivers have two different compression settings. One is the actual Dolby Digital dynamic range setting and it's buried in the menus with the speaker delay settings, etc.

Pioneer labels this one OFF (no compression, MID (mild compression), and MAX (max compression. But, you have to be careful to read the manual. Some companies label MAX (for max dynamic range, MIN (for minimum dynamic range.) This setting is a part of the Dolby decoder and ONLY applies to Dolby Digital source material -- not Pro Logic decoding, not DTS. It relies on instructions embedded in the Dolby Digital datastream.

The Pioneer also had a "MIDNIGHT" mode, which is clearly a compression scheme of some sorts (along with perhaps a bass boost?). This appears to be generic and applicable to all surround modes. Probably done in the digital post processing or DSP chips. Rather than a buried menu setting, this one is just a button that you turn on or off.

 

[Aaron Garman]

Hello all. Another question, how do I set the sub level precisely to 75dB? I forgot to mention earlier that the needle varies with the sub test tone from Video Essentials. Should I average levels, and if so what levels? I'm still trying to fine tune my JBL sub the best I can. Thanks again!

AJ Garman

 

[Rick Radford]

Harold,

Ok, I looked it up in my OM. Onkyo calls it Late Night mode (not midnite). And it does work strictly with DD material.

Here's Onkyo's description: "... When this parameter is set to "High" or "Low," the dynamic range of the sound is narrowed down to allow you to easily hear minute sounds at low volumes..."

Since high and low are relative terms, I have no clue as to which is best for reduced level listening. What does "high" and "low" refer to?

Whenever I think to try it.. we're always watching a movie and it's too distracting to switch back and forth and evaluate it while we're trying to watch.

... back on track ->

Aaron, just average the swings for your LFE setting. I'd guess the swings are due to room interaction with the LFE test tones. It's pretty common to see that.

Also, note that due to inaccuracies of the RS meter at lower freqs, a setting of 75 dB will be 2 to 3 dB hot.

 

[Harold_C]

Here's Onkyo's description: "... When this parameter is set to "High" or "Low," the dynamic range of the sound is narrowed down to allow you to easily hear minute sounds at low volumes..."

Well, that's an example of an owner's manual description that is essentially useless! In fairness, the guy writing the manual probably had no idea which setting was which so he had no choice but to fudge it with the language.

Here's my guess (but it is purely a guess).

As you push the button, it should cycle through three options. The first option is OFF -- maximum dynamic range. Whichever option appears with the next button press after OFF (either High or Low) is probably the milder of the two compression settings -- i.e the one that will reduce the highest peaks by 5dB or so. The next button press after that will probably take you to the heavier compression setting -- the one that will reduce the loudest peaks by 15 dB or so. Press the button again, and it will take you back to OFF.

Again, this is purely an educated guess. It would take listening to a portion of a soundtrack with particularly quiet background sounds and particularly loud sounds in the various positions to really nail it down.

By the way, Dolby refers to this heavier compression setting as "STANDARD" and requires this mode in all Dolby Digital decoders -- presumably because they are aware of how demanding the higher dynamic range settings can be on audio systems.

 

[Vin]

It's been my experience that setting the sub above where it is supposed to be set starts to very quickly make the sound muddy as the bass fundamentals mask the upper harmonics that give bass its "attack".

Based on your experience I can understand why you'd be reluctant to calibrate your sub higher than the main channels. My experience, however, has been positive.

I realize it's not 'technically correct' but it's a fairly common practice for those of us that normally play back at 10db or more below reference.

I guess the original poster will decide on his final settings depending on his playback levels and what sounds best to him.

Regards,

Vin

 

[Aaron Garman]

Hello all. Thanks for the help. I'm gonna give these ideas a shot. Just to give you all a reference, my room is a modest 9.5' by 11'. Small, but nice enough for a college student's home theater needs.

AJ Garman

 

[Aaron Garman]

Hello all. Well, I find nice levels for the room to be around -10dB of reference. As for bass, I merely adjust the sub accordingly for when I listen at lower levels. So far, everything is good. Cheers!

AJ Garman