LFE vs Diverted Bass - Is your processor WRONG? (Updated with custom test tones) (1 Viewer)

[Arnel]

Vince, nice of you to help in.

If someone could point out to me exactly what tone you're using, exactly where you found it on the disc- I'd be happy to check into the reason for the problem.

On the Title Menu, go to Advance AVIA - complete Audio and Video Calibrations (Chapter 7 - Calibrations)
On Audio Calibrations Menu, goto Verification/Evaluation
On the second page of Verification/Evaluation Menu, select the Low Frequency Pink Noise, 6 Channel Pan
The test will start with the following notations: "This circulating test tone contains only deep bass. Ideally, as it moves between the five main channels and the LFE channel, the tone should not change in level if the bass management of the system is operating correctly. Some slight variation in level is permissible, however, even in the correctly operating system. Recheck the bass management if the tone disappears altogether. If the system's LFE control has not been set to "normal" or 0-db setting, the level of bass may fall when the tone reaches the LFE channel."
Ok, the problem is, even if I set the LFE control to normal or 0 db, the level of the bass still falls by about 4 to 6 db. This would mean that if there where moments that all channels have a deep bass data, the LFE could be over powered by the other channels and make it almost non-existent. I have my LFE control set to maximum, where else can I modify to make the LFE leveled with other redirected bass?

 

[Arnel]

As Harold says, there were also deflections of about 4db between channels being tested but this doesn't concern me since they also reach a common level when the circulating test tone reaches the actual channel. What really concern me is the difference of LFE level against the other channels. Have anyone tried also this test? Did you get the same result? If this is but natural I think I have to stop asking.

 

[Vince Maskeeper]

As Harold says, there were also deflections of about 4db between channels being tested but this doesn't concern me since they also reach a common level when the circulating test tone reaches the actual channel. What really concern me is the difference of LFE level against the other channels. Have anyone tried also this test? Did you get the same result? If this is but natural I think I have to stop asking.

This is interesting- as my system is doing the same thing (3-4db drop when it hits LFE). I have double checked with the varsious discs I have containing dedicated LFE- and all are coming up rock solid and dead on. I haven't had a chance to seriously play with this track much (end of the semester), but hopefully in the next week or two I'll get the opportunity.

I have a copy of a dolby encoder for PC, and will probably go ahead and create a few test patterns of my own to see if I can figure out what's going on!

-Vince

 

[brucek]

Arnel,

Have anyone tried also this test? Did you get the same result? If this is but natural I think I have to stop asking.

After reading this thread, I tried this test on my system, having never used that particular test before on AVIA.

I have to concur with your results.

As the on screen icon indication moves to each of the 5 speakers, I get a common level that does fluxuate about 4db, but it's the same level in comparison between the 5 speakers as it cycles.

When the video indication is the LFE icon, my level does drop about 4dB in total. So I would agree that the AVIA disk is incorrect in this regard.

I have a fairly good system with my processor having the THX Ultra badge, so I don't think it is at fault.

brucek

 

[Boris]

Hi.

I'm 99% sure I once read a post somewhere by Guy Kuo stating that the LFE level was 10 down in the 6 channel pan.

I apologise if I'm mistaken.

Cheers

Boris

 

[Arnel]

I'm 99% sure I once read a post somewhere by Guy Kuo stating that the LFE level was 10 down in the 6 channel pan.

That's very correct Boris but if you'll continue reading his post, you'll find that while the encoded LFE is 10 db lower, on the decoding process it was compensated to yield the same result with other channels.

 

[Boris]

Hi
This is the thread.
Pete Mazz posts-
---
Great information!
Now the burning question.
Are the low bass test signals on Avia compensated in any way for use with the Radio Shack SPL meter, as it is known to read on the low side for lower frequency signals?
---
Guy Kuo replies-
---
No. The only compensation is for the discrete LFE in the 6 channel pan. That is 10 dB down electrically.
It would have been undesirable to alter the tones to specifically compensate for a single model of SPL meter. It would have made a mess for any other equipment because that poor should would have to undo the compensation built into a signal for the RS meter and then applying the correction for the meter being used. Far better to keep it standard and only expose the users to a single layer of compensations.
The signals are kept at electrical equal energy and you should compensate for your particular SPL meter. That means on the RS meter making the SPL reading equal 85 dB to match the 85 dB on the main tests yields a sub which is actually a few dB louder than neutral. Since so many of us HT fans like a lot of LF effects and don't listen at full reference volume, this yields an often more pleasing effect than a fully flat system.
---
Looks like I may have misunderstood???
However the reason I came to this conclusion is that on my system the LFE in the 6 channel pan is the best part of 10dB down. My system is calibrated accurately and the LFE pads are in the correct position (highest).
So it looks like I'm getting similar results to you guys.
Cheers
Boris

 

[Vince Maskeeper]

Alright kids- I know it's been a couple of months- but I finally got around to authoring a simple 6 channel pan test that should be correct.
I have created two test tones:
1) dd140hz1.wav: A 40hz tone at -20 which repeats in each of the 6 channels, one at a time (Left, Center, Right, Left Surround, Right Surround and LFE).
The exact same wav file was imported for each of the channels- so it absolutely identical. Because the LFE track in a dolby playback system (if configred correctly) boosts the LFE by 10db- a correct playback should keep the tone even until it reaches the LFE, where it will jump by several DB (approx 10).
2) dd140hz2.wav: A 40hz tone at -20 in the mains/ -30 in the LFE which repeats in each of the 6 channels, one at a time (Left, Center, Right, Left Surround, Right Surround and LFE).
The exact same wav file was imported for each of the channels- so it absolutely identical (aside from the LFE tone- but all tones were generated using professional tone generation software). Because the LFE track in a dolby playback system (if configred correctly) boosts the LFE by 10db- a correct playback should keep the tone even through all 6 speakers.
I used the tones in my system, using the Outlaw 950 preamp and found that the L/R speaker rerouted bass was slightly louder than the surround speakers:
L: +1db
C: +.5db
R: +1db
Rs: -1db
Ls: -1db
LFE: 0
I have always wondered if the Speaker volume setting has any effect on the rerouted bass info sent to the sub- I forgot to check- but will tinker with it later. If it does, it would be stupid-- but it might explain the 1-2 db difference between my channels.
-The tone is 40hz sine wave- so for this experiment you might want to start out with your x-over point around 80, and if you usually run lower- work your way down and see what effect it has.
- Tones are 5 megs a piece, so broadband is probably a must.
- These two files are DD wav files. It is possible to burn them to a CD, and play them in a cd player with a digital output- and get DD. This does not work with every player. However- if you have a PC with Spidf output, you should be able to use windows media player to play the files and get DD on your processor. Note, if you try to play these back in the analog domain you will get very displeasing noise! Be careful, turn the volume all the way down until the processor confirms a DD lock!
If anyone has any questions- feel free to post.
-Vince
PS: If anyone can think of other custom tones that would be helpful- let me know, I might be able to create them.

 

[Mark Fitzsimmons]

Hosted.

See links above.

 

[Vince Maskeeper]

Files have been fixed. The original posted versions had 48k encoding- so they would not work with standard CD burning software. The new ones are 44.1 and should work.

-Vince

 

[Nick V]

I don't know if it's just me, but the second link doesn't seem to be working

 

[Vince Maskeeper]

When did you last try? When I updated the files at 1:30pm, i fixed the link, and it works on my end.

-V

 

[Nick V]

It's good now, thanks!!

 

[Arnel]

Well Vince, I thought you have forgotten your promise. I have already downloaded the files and will try to burn it on CD. I will get back on this thread once I have the result on my system. Again thank you very much and God bless.

 

[Nick V]

I burned them to cd and playback worked fine in my dvd player. Only problem now, is that I can't find my damned SPL meter.

 

[Sebastian]

God bless.

NICE!!!

I down loaded them and burned them to a CD using Roxio CD creator.

Put it in my DVD player and ran the tests. No out put with the speakers set to small (onkyo rec) but worked when set to large, subwoofer set to "yes". With the meter at 75 Db the results were:

FL 0dB

C +8 dB

FR +4

RR and LR did not get a good reading even with the boost at +12 dB

My receiver indicated a Dolby digital lock, so what the deal?

Oh yeah the sub was off the chart(meter) even at -12 dB

 

[Vince Maskeeper]

Sebastian,

My first question would be: when you set to large, were the tones coming from the mains or the sub?

Secondly, do you have your sub hooked up "in line" with your speakers? In other words, is your sub hooked up from the main front speaker outputs, and then the speaker lines go onto the mains?

It sounds like that would be a reason why you got nothing when setting to small. It would also explain why you get nothing when you got to the rear tones. Sounds like your sub is not connected to the subwoofer output on the receiver- rather the speaker wires are going into the sub, and it's feeding bass off the front two speaker sends.

For these test siganls to work, you have to have you speakers connected properly for 5.1 playback (which means that the subwoofer runs off the sub output on the receiver, and the corssover controls are handled in the sub).

-Vince

 

[Sebastian]

With the speakers set to large I did have sound panning across all six speakers for about 5 sec each. Just the rear surrounds were extremely low. The sub was loud and it is connected to the LFE out on the back of the onkyo receiver.

The onkyo receiver bass mangement is different than most receivers. With the sub set to yes and the speakers set to small, they are crossed over at 120 Hz 6dB per octave and with sub set to yes and speakers set to large they get crossed over at 80 Hz at 12dB per octave.

The LFE attenuation level is set properly too, I believe 0dB for Dolby digital and +10 or for DTS. I am not sure if those are the actual values, but I know for sure it is set correct on the receiver.

 

[Vince Maskeeper]

Sebastian,

The 40hz tone should only come out of the sub if everything is configured properly- each channel tone lasts 5 seconds- but if you have bass rerouted to the sub, then the tone should only come from the sub. You said the tone panned across all 6 speakers? If so, the bass management is not rerouting the tone to the sub properly.

I'm confused-- if the bass management works as you suggested, why did you get no tone when set to small, yet got one when set to large? Something either must be connected incorrectly, of the bass management works differently than they explained it to you. I'd love to have an hour with your system to sort this out...

And I'm still baffled as to why you got such insane readings-- your l and r speakers shouldn't be 4 db different, even with basic configuation problems. Are you positive the only connection between your receiver and your sub is the single interconnect coming out of the subwoofer send on the receiver? There are no other lines running between the sub and the receiver?

-Vince

 

[Dan Hine]

Hello all,
I posted this in a thread in the receivers and separates forum as well but I'll post it here too since I know some people don't like to venture from their favorite section.
Thanks Vince for both the test tones and helping me sort through exactly what it all meant.
For those interested I have a Pioneer Elite VSX 35tx. My values for the first tone (LFE at same level on recording) came out as follows (using the Mains as reference point) also note that I run my sub about 1-2db hot:
L: 0
C: +3db
R: 0
LS: -3db
LS: -3db
LFE: + 10db
On the second recording (with the LFE -10db) everything was the same except for the LFE which was only 1-2db hot...which coincides with the way my system is set up with the sub calibrated about 2db hot. These show that the decoder is processing the LFE correctly since I do not have an LFE pad, only the general subwoofer level setting.
I find it interesting though that on the first recording it only measured as +10db even though I do run my sub hot as was reflected in the second recording. All in all a fun test and very informative about the receiver. In fact, the next time I audition a receiver or processor this will be an asset. I will be able to test and see if I'll be able to still get accurate calibration from the system in case it has no LFE pad. And even if it does you can test its accuracy.
Thanks again Vince!
Dan Hine
P.S.
Does anyone have an idea as to why it reroutes the bass from the center a little high and the rears a little low? You can see this reflected in Vince's numbers as well though not it was not as drastic as mine. Thanks.