Difference Between Avia and DVE - Subwoofer Calibration (1 Viewer)

[Jeremy Anderson]

Here's my whole equipment list:
Onkyo TX-SR600 receiver
Polk Audio RTi28 mains, surrounds, rear
Polk Audio CSi40 center
SVS 20-39CS+ w/Samson 1000 amp and ART-351 EQ
Panasonic RP-56 DVD (w/latest firmware)
Hitachi 43UWX10b RPTV (ISF'd by Gregg Loewen)

I'm installing a Sanyo PLV-Z1 (or maybe Z2) projector and Da-Lite 92" screen in a few weeks to add to that list.

 

[Edward J M]

Sorry this took so long, guys. It's been raining like a son-of-a-gun here.

Finally got a nice day to ground plane and here's the test results:

20-39PC+ in 20 Hz tune at 1 meter ground plane with B&K SPL meter on C-weighted Slow and Master Volume at 0.0 and RB xo to 120 Hz:

Avia: 90 dB (arbitrarily adjusted gain at SVS to obtain 90 dB)
DVE: 88 dB

Since DVE has lots of deep signal content (to below 20 Hz), I broke out the TrueRTA rig to measure the actual unweighted SPL, since the SPL meter will read lower for DVE than for Avia (which only has bass to about 40 Hz).

20-39PC+ in 20 Hz tune at 2 meters ground plane with TrueRTA and Master Volume at 0.0 and RB xo to 120 Hz:

Avia: 90 dB (arbitrarily adjusted gain at SVS to obtain 90 dB)
DVE: 91 dB

20-39PC+ in 16 Hz tune at 2 meters ground plane with TrueRTA and Master Volume at 0.0 and RB xo to 120 Hz:

Avia: 88.2 dB (just plugged port, did not re-adjust gain)
DVE: 88.7 dB

There you have it, guys. Outdoors with ground plane and no room gain or boundary effects, my copy of DVE is slightly louder than Avia on the subwoofer tone. It is only 2 dB less with a C-weighted meter.

Since my copy of DVE is about 16 dB hot inside the house (as read on my SPL meter), I'm definitely getting lots of room gain, as Jeremy suggested. But that doesn't change the fact that my copy of DVE is almost exactly 10 dB hot outside.

Here's what I think: My copy of DVE does not take into account that the pre/pro boosts the LFE channel 10 dB. If I subtract 10 dB from my indoor sub reading (76 sat, 93 sub), I'm getting almost exactly what Jeremy predicted (76 sat, 83 sub) - about 6 dB of room gain resulting from the broader bandwidth of DVE. That would make perfect sense.

I took pics of the whole sordid affair if anyone wants to see them.

Regards,

Ed

 

[steve nn]

I took pics of the whole sordid affair if anyone wants to see them.

Sure Ed. Show us some pics if you have the time.

 

[Edward J M]

I edited my previous post above to clarify what I think is wrong with my copy of DVE and I'll post it here too, with Steve's request for the pics.

Since my copy of DVE is about 16 dB hot inside the house (as read on my SPL meter), I'm definitely getting lots of room gain, as Jeremy suggested. And I've confirmed room gain several times with TrueRTA. But that doesn't change the fact that my copy of DVE is almost exactly 10 dB hot outside.

Here's what I think: My copy of DVE does not take into account that the pre/pro boosts the LFE channel 10 dB. If I subtract 10 dB from my indoor sub reading (76 sat, 93 sub), I'm getting almost exactly what Jeremy predicted (76 sat, 83 sub) - about 6-7 dB of room gain resulting from the broader bandwidth of DVE. That would make perfect sense.

Naturally, this little experiment is reproducible anytime (provided I still have access to that 20-39PC+). I'll check the file dates on my copy of DVE and see if that sheds any light, because mine was an early pre-order.

Here's some pics, Steve. Deliberately low res; it saves bandwidth:

1 Meter With B&K SPL:



2 Meters With TrueRTA And 20/16 Hz Tunes:



Yours Truly With B&K, Avia, DVE, And 20-39PC+:

 

[Philip>L]

That's awesome. The length's that enthusiasts will go never ceases to amaze me!

So what's the bottom line here?

Is there any way that I can use DVE to accurately calibrate my sub without using an equilizer?

 

[JackRI]

What Phillip said. For those of us technically challenged, can you distill all that into layman's terms? Do all pre/pros (receivers?) boost the LFE 10dB?

Heck of a job, by the way. Thank you for taking all the time to do the testing. Glad to see the sun finally showed up.

 

[steve nn]

>>>Yours Truly With B&K, Avia, DVE, And 20-39PC+:

 

[Edward J M]

The disparity between my data and Jeremy's data indicates there are good and bad copies of DVE floating around. If he equalizes for about 5-6 dB of room gain, his copy of DVE is fine.

On my copy of DVE, you would have to account for a 10 dB encoding error right off the top, and then also equalize for any room gain - in my case about another 6 dB.

I would start calibration with your AVR test tones or Avia as a solid baseline. Then pop in DVE.

If your copy of DVE blows the meter off the scale and is about 13-16 dB too hot, then you have a defective version.

OTOH, if your copy of DVE is 3-6 dB hot (like Jeremy's), then it is probably OK, and you are just seeing room gain from the much broader bandwidth DVE is using.

In either case, I don't think you need a PEQ per se, you just need to be confident which version of DVE you have.

Edit: All pre/pros boost the LFE channel 10 dB unless the user specifically attenuates that channel with the LFE trim control. Not all pre/pros have an LFE trim control, though.

Edit #2: Steve, knee pads are for sissies. I'll take grass stains any day.

Ed

 

[Jeremy Anderson]

I'm beginning to think that my copy is the same as yours and that my logic is just flawed (as well as my equipment setup). Based on the dates of the files on my disc, my disc was made before the initial release date so it is probably not a repressing.

I think perhaps my logical error lies in how I derived what the total output should be. Here are the readings from the digital source files of each disc (with C-weighting already applied):
Avia -16.56dBC
DVE -29.01dBC

Avia's tone is in the left main channel, meaning its maximum output at reference should be 105dB. Since the tone is encoded at -16.56dB from max, Avia should read 88.44dBC at reference level based on the digital source. DVE, however, is in the LFE channel... which, as you've said, gets a 10dB boost so has a maximum output of 115dB. So 115 - 29.01 = 85.99dBC. In other words, pretty much the same as the Avia tone, when it should be 10dB lower.

Joe Kane, in the Q&A on DVE, says: "Our measurements were made at the output of the Dolby Digital decoder with C weighting applied. They do not account for anything that might be going on in the amplifier or in the room itself." Maybe the problem is that their equipment was showing the level of this tone BEFORE the LFE boost, since he was deriving this from the DD decoder.

I'm going to do some more testing on my system to make sure there are no equipment issues on my end (and hopefully correct them, since there's obviously SOMETHING wierd going on here), but at this point I think Edward's conclusion is pretty much rock solid and indisputable.

 

[TimRP]

It seems like there are two answers here, and neither of which seem like they can possible jive with each other. I would agree that Ed's testing and conclusions seem rock solid, but at the same time it seems like Jeremy's tests and conclusions are right as well. But the one thing I think we can take from all this testing is Avia is probably more correct in its subwoofer tests then DVE is with its subwoofer tests. Which is why I will only recommend Avia or Sound and Vision HT tune up. Thanks for all your hard work guys it has be enlighting to say the least.

 

[Sebastian]

Tim,

When you use S&V HTT clibration disc. Is the sub 5dB hot when compared to AVIA?

If I calibrate my sub using VE and adjust my sub to be 5dB hot over the mains.
Then slap in HTT the sub is about 10-12dB hot over the mains.

 

[Jeremy Anderson]

Yeah, Tim... The bottom line is that subwoofer calibration with DVE is too problematic for the end user. Also, the "40-80Hz" tones on the disc are NOT 40-80Hz tones as labeled (which is something both Edward and I have verified). I like having a wideband LFE tone, but I think Joe Kane should have included both that and a band-limited tone to accomodate everyone.

I still have some testing to do with my own system, as well as checking my EQ'ing (because I just changed from drapes to blackout shades, moved some furniture, etc.). I'm also going to burn a Dolby Digital disc to use in conjunction with my DTS disc to make sure bass management and LFE trim is functioning properly on my gear. I will continue to tinker with DVE, Avia, etc. and post anything interesting that I find.

Big thanks to Edward for dragging that sub outside and putting both discs through their paces!

 

[Jeremy Anderson]

Despite everything, I'm still confused by the results in my room. I've just spent the last hour tweaking my EQ to correct for the changes I've made in my room layout. After some minor changes, my subwoofer is back to +/-3dB flat corrected response from 20-100Hz (with crossover at 120Hz on receiver so the LFE channel isn't affected and subsonic filter at 10Hz on EQ). This was checked with 1/6 octave sine tones from 20-100Hz in both the left main and LFE channels, and each band comes out 9-10dB higher in the LFE channel, as it should if bass management is working correctly. When I run the wideband tones disc I made using DVE's sub test tone, it comes out 6dB higher on LFE compared to redirected bass, which seems to jive with Dolby's observations on how to set LFE with pink noise. I also double-checked my readings on redirected bass with the same sine tones burned to an audio CD, with my receiver in STEREO mode (which redirects bass to the subwoofer), and got the same response curve. At this point, I'm pretty certain bass management is being properly handled in my setup.

I then adjusted to reference level. Using the internal tones, I verified that all channels were at 75dB and subwoofer at 73dB (to account for C-weighting). I then popped in Avia, which correctly read 85dB for all channels and 83dB for sub. I then popped in DVE, which read 75dB for all channels and slightly over 75dB for sub (since it is pre-compensated for C-weighting). I also changed DVE to the DTS test tones just to double check, and got similar results.

This is all very confusing, because despite everything we've come up with in this thread, my DVE disc is still performing as advertised.

Edward, I think there's one last thing we might try to make sure there aren't different discs floating around: If you are willing to mail me your copy of DVE, I will mail you mine. That way, I can check the file dates on your disc and do frequency comparisons digitally, and you can see if my disc reads differently than yours on your gear. PM me your address if you're willing to do this, and I'll shoot you mine.

 

[Edward J M]

Hi Jeremy:

Before we consider swapping discs, you need to take your room out of the equation. Easy with a passive sub. Just run 30 feet of 12 gauge out the window and plop the sub on a sheet and let 'er rip. If your copy of DVE is 2 dB less than Avia (90/88 for me) with a c-weighted meter, we have the same pressing. If not, we don't. Either way confirms without swapping DVDs.

I have no trouble swapping any other DVD except this one. If mine is truly defective and it gets lost or damaged in transit, I'm SOL. And I definitely want to keep it for posterity and proof. Safest route is for you to check outdoors, first. I'd even go so far as to buy another version and check it out before I risked shipping this one.

Ed

 

[Jeremy Anderson]

Easier said than done in my room, Edward. Besides, my back yard is this wierd alcove that is basically an echo chamber, so the results would be useless. I could do it in my front yard, but I have unsavory neighbors who I'd rather not have see (or hear) my subwoofer, lest it get up and walk away when I'm not home.

I wish someone else who has the problem with DVE would verify the file dates so we could put that aside as a possibility.

Edward, I'll take one for the team: Shoot me your address and I'll mail you my copy of DVE, so long as you mail it back when you're done with it. If you get it and get wildly different results with it, we'll know they are different discs. If not, then we can rule that out. If it gets lost or destroyed in transit, SCREW IT... I still have Avia, and DVE was only $20.

 

[Edward J M]

Roger that. I'll just compare the two inside under the same conditions. Any disparity that large will be immediately obvious. I'll post the results and ship it right back. If it gets damaged in transit, I'll wire $20 via PayPal for your trouble. You've got PM.

Ed

 

[Philip>L]

How does one do this? Is it as simple as popping the disc into a DVD-ROM drive and opening up windows explorer?

 

[Stephen_F]

Yes, it is as simple as that.

Wow, guys this thread is great. It looks like one way or another Edward and Jeremy are going to get to the bottom of this strange problem, well done guys

 

[Edward J M]

Ditto for my DVE copy.

Strangely, the Audio folder is empty (but is dated 8-14-03). The Video folder (also dated 8-14-03) is chock full of files. Not sure why I'm not reading anything in the Audio folder.

 

[Jeremy Anderson]

That's because the audio streams are part of the VOB files, not authored separately. When I digitally extracted the LFE tones, I had to do it by extracting the AC3 stream from Title 9, Chapter 13 of the video files.

But if your copy of DVE has 08/14/03 for the files, that means your disc and mine are identical. Had there been any revision, the file for title 9 would have a different date. Knowing that, there's no reason for us to swap discs. Now I just have to figure out why DVE is calibrating correctly in my room.

But I think the bottom line here is still that DVE isn't user friendly for most people and produces inconsistent results from room to room.