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Difference Between Avia and DVE - Subwoofer Calibration


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#1 of 141 OFFLINE   Edward J M

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Posted February 15 2004 - 02:33 AM

This topic has generated some interest in the Speakers and Subwoofers Forum recently, particularly as it applies to subwoofer calibration. Even though it is a software related topic, it certainly has bearing in this forum.

I use Avia to calibrate my system to Reference Level, so the Avia subwoofer level listed is my preferred setting for my system.

Here are the results - again on my system with my copy of Digital Video Essentials:

Set-Up:

B&K Model 2205 sound meter placed on a tripod at the listening position at head level, facing forward at a 45 degree upward angle. Meter setting is C-Weighted, Slow.

AVR-3803 Master Volume set to 0.0

Remember, DVE is supposedly encoded 10 dB less than Avia.

Results:

Avia Surround Channels: 85 dB
Avia Subwoofer Tone: 82 dB (average of all channels)

DVE Surround Channels: 76 dB
DVE 5.1 Subwoofer Calibration Tone: 88 dB
DVE 6.1 Subwoofer Calibration Tone: 88 dB

Comments and Interpretation:

The DVE surround channels are right where they should be - almost exactly 10 dB lower than the Avia surround channels.

It is interesting to note the Avia subwoofer calibration tone uses the surround channel and redirected bass. Therefore the surround channel speaker contributes volume to the Avia subwoofer calibration tone.

In contrast, the DVE subwoofer tone does not use the surround speaker channels at all. It only uses the LFE channel.

A DD/DTS pre/pro automatically boosts the LFE channel 10 dB. If a disc encoder wants the LFE channel to provide the same volume as the redirected bass from a surround channel, the LFE signal must be encoded 10 dB less than the corresponding surround channels.

Conclusions:

The subwoofer calibration tone on my version of DVE is 12 dB higher than the corresponding DVE surround channels.

The subwoofer calibration tone on my version of DVE is also 6 dB higher than the Avia subwoofer calibration tone under identical room conditions at the exact same Master Volume level.

I can only speculate, but I suspect an improper encoding level for the LFE channel (0.1) is primarily responsible for this problem.

YMMV - it is possible later versions of DVE have been corrected - mine was an early pre-order version.

I hope this helps DVE users who are having problems with subwoofer calibration. Regardless, I strongly recommend comparing DVE to another disc like Avia or S&V or the older (OOP) VE as part of your subwoofer calibration process.

Regards,

Ed
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#2 of 141 OFFLINE   Kevin C Brown

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Posted February 16 2004 - 12:36 PM

I still think there's one more aspect to the equation. That is listening and adjusting from there.

I have always adjusted using Avia. But for low freq intensive movies, I always felt the sub was too loud. But it is also known that the Radio Shack meter is less sensitive to low freq info too. So in essence, depending on the low freq info in the test tone that's being used, the LFE ends up to be too loud because of unknowingly compensating for the lower sensitivity of the Radio Shack meter.

I found what best works for me, is to use Avia, but to adjust to 5 dB lower.

But like you say Ed, ymmv ... Posted Image
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#3 of 141 OFFLINE   Zack_R

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Posted February 16 2004 - 12:59 PM

Avia does use redirected bass for sub calibration. This is really good for stereo music set-up. However, once I have performed this test, I always like to do a gut check against my receivers discrete test tones to ensure my sub is calibrated pretty good for movies.

The only real issue I have with Avia is that the sub calibration only goes to 35 hz. I have found that while this does in fact calibrate my sub properly against the surrounds it doesn't calibrate the sub against itself. Meaning in order for me to achieve a calibration that yields a 20 hz tone equal to a 70 hz tone I need to bump the sub output up 3 dbs. Doing this makes the sub equal amongst itself but is now hot compared to the surrounds. I have a big room so I don't get the nice gradual bass rise many folks experience in their HTs as a result of room gain.

Ideally I need an eq so that I can leave my Avia calibration as is and bump the 30 hz and below up 3 dbs.

There is a dedicated LFE sweep that you can play to test your room response and to see how your receiver pre/pro's crossover affects the LFE channel.

#4 of 141 OFFLINE   Edward J M

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Posted February 16 2004 - 01:43 PM

DVE Surround Channels: 76 dB
DVE 5.1 Subwoofer Calibration Tone: 88 dB
DVE 6.1 Subwoofer Calibration Tone: 88 dB

Posted Image

I didn't want anyone to miss the main point here amidst all my rambling: My copy of DVE is insanely hot on the sub calibration tone.

If Avia is any indication (85/82 sat/sub), the DVE sub calibration tone should be reading about 73 dB.

Instead it is reading 88 dB.Posted Image

Something is seriously wrong with my copy of DVE, and I wanted others to know theirs might also be FUBAR'd in the event they were pulling their hair out trying to calibrate their sub.

Ed
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#5 of 141 OFFLINE   GraysonAng

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Posted March 16 2004 - 08:50 AM

Does that mean that if I use DVE, I should use 75db for all speakers and 85db for the sub?

Grayson

#6 of 141 OFFLINE   Edward J M

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Posted March 16 2004 - 12:02 PM

Quote:
Does that mean that if I use DVE, I should use 75db for all speakers and 85db for the sub?

If your copy is anything like mine, 85 dB would be a good starting point.

It might be worth your time to compare your copy of DVE to S&V or Avia. JKP might have fixed later production versions of DVE, for all I know.

Again, if I calibrate my system with Avia to 85 dB on the surrounds and 82 dB on the sub, and then pop in DVE without touching anything, I get 75 dB on the surrounds and 88 dB on the sub.
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#7 of 141 OFFLINE   GraysonAng

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Posted March 17 2004 - 01:19 AM

So by your test, you would have to calibrate the sub to 88dB on DVE.

Grayson

#8 of 141 OFFLINE   Edward J M

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Posted March 17 2004 - 05:16 AM

Quote:
So by your test, you would have to calibrate the sub to 88dB on DVE.


Correct.

And realize that 85/82 on Avia is running the sub FLAT at best (with the C-weighted correction factor included), or maybe even a little cool.
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#9 of 141 OFFLINE   Brian L

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Posted March 18 2004 - 02:41 AM

In case anyone has not seen it, the issue with the sub channel calibration on DVE was mentioned in this link:

http://www.hometheat....=&pagenumber=1

In fact, there are some e-mails from Joe Kane in here as well.

That said, I don't think anyone has tested quite to the extent that Edward has.

Furthermore, Joe did comment on the matter in a WSR a few issues back. However, I am not sure I understand or accept his explanation, which seems to lay the blame on differences in the way the tone is recorded, and largely, on room acoustics and poor measurement techniques on the part of the users.

Joe is a great engineer, and has done a tremendous amount to advance our hobby, but when I read his stuff, I get the impression that he would benefit from having a good tech writer edit his stuff.

Perhaps I am just too stupid to understand some of his writings, but he reminds me of some of the propeller heads that I work with that, when asked for the time, will provide detailed directions on how to build a watch, while explaining in detail why the concept of time is fundamentally flawed.

BGL

#10 of 141 OFFLINE   Edward J M

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Posted March 18 2004 - 04:55 AM

Quote:
However, I am not sure I understand or accept his explanation, which seems to lay the blame on differences in the way the tone is recorded, and largely, on room acoustics and poor measurement techniques on the part of the users.


Sounds like damage control to me.

Room acoustics don't come into play when nothing is adjusted or moved and all the user does is switch discs.

DVE uses the LFE channel for sub calibration. Avia uses the surround channel and redirected bass.

All pre/pro's boost the LFE channel 10 dB on Dolby Digital DVDs. Unless the LFE channel is encoded at -10 dB in relation to the surround channels, it will come out 10 dB hotter on playback.

Vince Maskeeper did many of us a great service a while back when he posted professionally mastered 40 Hz sine wave test tones for the redirected bass on the 5 surround channels and also for the LFE channel. One of the LFE tracks was encoded at the same level as the surround channels, and the other LFE track was encoded at -10dB. I downloaded those test tones and they were accurate - I mean right on the bean. The five RB channels and the -10 LFE channel all played at the same exact level. And the unattenuated LFE channel tone jumped exactly 10 dB above the other six readings. Vince's test tones proved the BM circuit in my pre/pro is functioning perfectly.

Again, it's just a hunch, but if you subtract 10 dB from my DVE subwoofer reading it would be 78 dB. At least I'm in the ballpark at that point 75/78.
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#11 of 141 OFFLINE   ScottCHI

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Posted March 18 2004 - 05:01 AM

Quote:
Vince Maskeeper did many of us a great service a while back when he posted professionally mastered 40 Hz sine wave test tones for the redirected bass on the 5 surround channels and also for the LFE channel.
could you please direct me to this "post"?

if they're not available anymore, any chance you could send them my way or make them available for download?

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#12 of 141 OFFLINE   Brian L

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Posted March 18 2004 - 05:12 AM

Quote:
DVE uses the LFE channel for sub calibration. Avia uses the surround channel and redirected bass.

Edward, can you expand on that a bit?

When I use Avia for my sub calibration, I use the tones that alternate between the sub and one of the main channels (I use sub vs. center).

So, I use the discrete channel balance tones to get the main channels matched, then I use the sub test tones mentioned above to balance the sub to one of the main channels.

I was under the impression that, using that method, I am in fact sending a signal out the .1 channel.

In your experience, is that incorrect?

BGL

#13 of 141 OFFLINE   Edward J M

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Posted March 18 2004 - 05:26 AM

Quote:
could you please direct me to this "post"?


Probably the quickest way to find it would be to PM Vince. I'm sure they are still available.

Quote:
When I use Avia for my sub calibration, I use the tones that alternate between the sub and one of the main channels (I use sub vs. center).

So, I use the discrete channel balance tones to get the main channels matched, then I use the sub test tones mentioned above to balance the sub to one of the main channels.

I was under the impression that, using that method, I am in fact sending a signal out the .1 channel.

In your experience, is that incorrect?

Avia uses the surround channel and your bass management circuit and redirected bass at the specified xo for the sub tones on each surround channel. If you power off your subwoofer and run the tone, you'll hear some bass still coming from the surround speaker in question. If your speakers are set to large, there will be no sound from the subwoofer on these tones.

Avia does have an LFE (.1) channel sweep in another section of the DVD, but it is not used for channel balancing.
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#14 of 141 OFFLINE   Brian L

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Posted March 18 2004 - 06:45 AM

Edward, I think we are singing from the same hymnal, but different songs.

On my Avia, under the section on sub set-up and calibration, there are tones that simply alternate between the sub and a chosen main speaker (you can select any main that you wish). These are not sweeps, just alternating tones that I use to match the sub to the chosen main speaker.

I do not know what frequency the tones are at, but the main channel tones sound like the normal channel balance tones. And I also do not know if the main channel tone includes any low frequency information that BM would send to the sub, nor if the tone that I hear from the sub is in fact encoded on the main channel and thus redirected to the sub via BM. I always thought it was discrete, but I could well be wrong. And either way, I suppose it matters not.

BGL

#15 of 141 OFFLINE   Edward J M

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Posted March 18 2004 - 08:06 AM

Quote:
I do not know what frequency the tones are at, but the main channel tones sound like the normal channel balance tones.

Yes, it is just some limited spectrum white noise.

Quote:
And I also do not know if the main channel tone includes any low frequency information that BM would send to the sub,

The white noise surround channel tone might contain a "little" information sent to the sub, but I doubt it's significant. The only way to find out for sure is to disconnect the speaker in question and leave the sub running and run the white noise test tone for that channel and see if the sub contributes a little sound pressure.

Quote:
nor if the tone that I hear from the sub is in fact encoded on the main channel and thus redirected to the sub via BM. I always thought it was discrete, but I could well be wrong.

With Avia, the subwoofer calibration tone is a surround channel signal. It is sent to the subwoofer via the bass management circuit and is redirected bass. It will only work if your speakers are set to small. It is not a discrete signal since it is not derived from the LFE (.1) channel.

It is easy to prove this: Just shut off the sub and run the subwoofer test tone for any surround channel. You will hear some bass coming from the surround speaker.

Quote:
And either way, I suppose it matters not.


Actually it matters a great deal. Have you ever noticed that the sub level on Avia typically changes (sometimes as much as 3-4 dB) depending on which surround channel you select? The reason for this variation is because each surround speaker interacts with the sub a little differently.

If the sub calibration tone was discrete, it wouldn't matter which surround channel you selected, you would get the same sound pressure from the sub every time.
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#16 of 141 OFFLINE   Kevin C Brown

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Posted March 18 2004 - 12:39 PM

Ed- I am also thinking the same that Brian is. I use the same Avia test he is referring to: when the signal toggles back and forth between the left front and sub. Center, then sub. Etc. Seems like a genuine sub output to me (not redirected).

I guess I will have to unpower the main speakers (and/or sub) and see what happens.

Quote:
Actually it matters a great deal. Have you ever noticed that the sub level on Avia typically changes (sometimes as much as 3-4 dB) depending on which surround channel you select?

See, I *have* noticed this. (Well, I only ever compared left front to center to right front.) The center always had weak bass. This is true for 3 different pre/pros and two different amp setups, and 2 different speaker setups. I always figured it was a problem with Avia. And I did try playing with the crossover freq, phase, etc, for the center channel. I could *never* get the center channel sub output level to match the left and right. And, for me, the left front and right front sub outputs were identical in level.
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#17 of 141 OFFLINE   Edward J M

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Posted March 18 2004 - 12:51 PM

Quote:
Seems like a genuine sub output to me (not redirected).


Not true - it's redirected bass using the pre/pro BM circuit.

Just power off the sub and run the sub test tone for each channel - you'll hear bass coming from each surround speaker, especially if you're using an 80 Hz xo or lower in the BM circuit.
Ed Mullen
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#18 of 141 OFFLINE   Lewis Besze

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Posted March 18 2004 - 02:33 PM

Ed is right,Avia doesn't use dedicated LFE tones for calibration purpose,and yes I use the main left for calibration not the surrounds,don't know what Ed is reffereing to on that one.
I'm also dissaponted with DVE,and Joe Kane's lame ass "explanation".He should recall the discs correct them and apologize. It would be all forgotten soon.

#19 of 141 OFFLINE   Kevin C Brown

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Posted March 18 2004 - 06:13 PM

OK, I'll try it and convince myself...
If it's not worth waiting until the last minute to do, then it's not worth doing.

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#20 of 141 OFFLINE   Edward J M

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Posted March 19 2004 - 01:58 AM

Quote:
and yes I use the main left for calibration not the surrounds,don't know what Ed is reffereing to on that one.


Hi Lewis. Give it a try with all five surround channels and see how your results vary. You might even see a few dB difference on the sub tone level between the left main and the right main.

Sometimes if the sub is located near one speaker, and in phase with that speaker, the sub tone will be louder (sometimes by 3-4 dB) for that channel than for any other.

I like to check the sub level for all five surround channels to get a feeling for the range between the lowest and the highest readings. I then usually calibrate off the surround channel that is most represenative and falls between the lowest and the highest channels.

Of course all my surround speakers have decent mid-bass capability (the least of which has an F3 of 55 Hz), so any of them will do a good job of contributing some mid-bass volume to the subwoofer test tone on Avia. If you are using a smaller center or side surround speaker, your results may vary. Only one way to find out....break out the sound meter and Avia. Posted Image

Ed
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"What we do in life, echoes in eternity."



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