SACD/DVD-A Players - LFE Channel Level (1 Viewer)

[Lewis Besze]

But there is a big hole in that argument: If it were so, then the user would need to reduce the bass level for DVD-A and SACD sources (assuming the user applied to +10 dB somewhere in the signal chain).

The problem with this,that you can't boost the LFE independently by raising the sub out[player] or in on the receiver.Possible execption of the new Denons[3803/5803].If you raise the sub trim level only it will affect both the redirected and the LFE content.
For instance on my Denon 2900 when played DD/DTS movies,I notice that the LFE lacks on certain momments,that I know it has large LFE peaks[not redirected bass],but on most normal part it seems fine.This is when I compare it to the digital out[receiver decoding].So this led me beleive that the player doesn't do the boost.
On MC music however it's just right,no disc I put in so far,that would have suffered from low bass.There were some "charges" that this player won't have the right amount of LFE on MC formats,but I don't see how it can be proven beyond doubt,as the current test disc providers should "explain" how it was recorded[exact level for all channels].
I haven't tried the Chesky disc yet but the DVD-A tones on the Telarc Celebrating the Music Of Weather Report,is a recycled Dolby tone IMO.

 

[Steve_D]

*sigh*...this is exactly the issue that prevented me from buying the Denon 2900...and went with the Philips 963 instead.

My solution is to run DD/DTS decoding in my Denon 3801.

SACD runs off the L/R analog into the Denon, where it handles bass management. AHHH, say the purists. but then you have an extra A/D/A conversion. Yes, but only for the bass frequencies...It uses a combined Analog bypass / Digital bass management scenario so only the low Freqs go through this extra A/D/A conversion. No, not perfect, but nothing is at this stage of development.

When the uni-players get BM right, then I'll go with a passive 6.1 pre-amp....or hopefully the Uniplayer will have a master volume control...thus bypassing the need for a pre-amp!

 

[Brian L]

For instance on my Denon 2900 when played DD/DTS movies,I notice that the LFE lacks on certain moments,that I know it has large LFE peaks[not redirected bass],but on most normal part it seems fine.This is when I compare it to the digital out[receiver decoding].So this led me believe that the player doesn't do the boost.

Interesting observation, Lewis.

I have in my rig my old Sony SDP-800 DD decoder. I use it for HDTV and Satellite (since my receiver does not support DD).

FTR, this is connected through the same 6CH input as my 45A/ICBM. The 6CH trims are set via the Chesky disc feeding through the 45A/ICBM.

When I added the old Sony back into the rack, I used it's own trims to reduce the bass level by 10 dB to compensate for the boost already present in my signal chain.

This afternoon, I was watching MIB II on HBO, and I distinctly recall thinking that the bass is HUGE when played through the old Sony. I don't own the title on DVD, but did rent it, and really did not think it was all that great bass wise.

So, what you observed correlates to what I have observed here, even though I do have a +10 boost in the signal path.

Makes me wonder if applying the +10 after the LFE is summed with the redirected bass is the wrong thing to do.

Time to bone up on DD decoders!

BGL

 

[Brian L]

SACD runs off the L/R analog into the Denon, where it handles bass management. AHHH, say the purists. but then you have an extra A/D/A conversion.

I sure would not lose any sleep over that, Steve.

These are the same guys that swear those $500 interconnects "remove a veil of grunge from the music".

BGL

 

[Lewis Besze]

Steve,
You might have misinterpret my observation on the 2900 as a SACD/DVD-A player with the BM engaged.
While I'm not using it's internal DD/DTS decoding but I use it's internal BM for SACD and DVD-A and even for CDs.
It's doing an excellent job at it.Like I said the "alleged" LFE issue with MC music is a speculation at this point given the fact of the lack reliable testing and the fact that actual usage of this channel varies by a large degree on the current titles out there.

 

[Espen Braathen]

Quote:

"Makes me wonder if applying the +10 after the LFE is summed with the redirected bass is the wrong thing to do."

Yes, it's the wrong thing to do. If you try this the bass mixed in from the five full range channels will not get the right level.


Espen Braathen

 

[Espen Braathen]

Quote:
"But there is a big hole in that argument: If it were so, then the user would need to reduce the bass level for DVD-A and SACD sources (assuming the user applied to +10 dB somewhere in the signal chain).

But that is NOT what happens."

It depends on the player. I can only speak for the AOny SACD/DVD-Video players as I'm not using a DVD-A capable player.

The early hybrids scaled back the SACD LFE by -10 dB to keep it at the same relative level as DD LFE without the boost. There was also a further -5 dB gain adjustment before summation, thus a raw LFE signal lacked -15 dB in total.

The later Sony SACD/DVD-hybrids does only require +5 dB LFE correction, since they have abandoned the goal to keep DD LFE and SACD LFE at the same realtive level. Thus now I only use the +5dB gain factor in my Denon 5803/AVC-A11SR amplifier (the older 700 player needed the +15 dB factor).


Esp1

 

[Espen Braathen]

Quote:
"Correct,it's safe to say that most of these players don't do the boost,although I don't see how they got their Dolby licensing,even though they feature the logo."

No internal DD decoder does the +10 dB LFE boost. This is in line with Dolby Labs recommendations for "simple" built in decoders.

Some internal decoders apply a further -5 dB gain reduction to the bass from all channels before summation to avoid overloading the output stages. This varies between the manufacturers.


Esp1

 

[Steve_D]

Lewis,

No, there is a huge thread over at avsforum that points out the same issue with bass management on the 2900. A Denon factory rep that posts frequently over there inisists it is working as designed. "As designed" apparently works best with Denon receivers with the variable Sub-in adjustment.

 

[Brian L]

"As designed" apparently works best with Denon receivers with the variable Sub-in adjustment.

But as Espen commented, thats still wrong, in that these Denon users would be doing BM in their players, and thus the sub channel that gets sent to the receiver is the summed bass + the LFE. Of course, the Denon players also have some hocus pocus in their set-up, so it is possible that the player/receiver combo can in fact be set for correct levels across the board.

If it is in fact correct that the boost should only apply to the LFE, than a boost at the receiver and/or sub amp (which is what I have been doing) incorrectly boosts the summed bass AND the LFE.

I did a quick search at the Dolby site, but did not find a block diagram showing the DD decoder + bass management. I wanted to see just where the +10 takes place.

Back a while, WSR ran a series of articles by Richard Hardesty, that included block diagrams of a fully equipped decoder. I am positive it showed where the +10 was, but unfortunately I tossed it and its not available for download at the WSR web site.

For yucks, I just re-calibrated my rig (45A/ICBM).

I was previously set for fixed level across all channels (using trims in the receiver for balance), but changed to Variable in the player (-4 on all mains, +6 on the sub). With all speakers Large/Sub on, that should theoretically give my a LFE channel that is 10 dB above the mains.

I then needed to tweak the trims on the receiver to get equal levels, and I can no longer get 85 dB at 0 dB on the volume knob (the output of the Pioneer is too low), however I did get 80 dB across the board.

I will need to do some listening tests to see how my various DVD-A's, SACD's, and Movies sound, but a quick listed to Steely Dan, The Eagles, and David Bowie seem promising.

Steely Dan in particular seemed to have about the same level of low bass, but seemed to have better impact.

Disclaimer: The previous statement was totally subjective in nature, and not based on any sort of scientific tests whatsoever. It may in fact be total bull sh*t.

BGL

 

[Lewis Besze]

No, there is a huge thread over at avsforum that points out the same issue with bass management on the 2900. A Denon factory rep that posts frequently over there inisists it is working as designed. "As designed" apparently works best with Denon receivers with the variable Sub-in adjustment.

Yeah, I know of that thread,it's bunch of BS,if that's what steered you from getting this player you missed out on a great player.
The Denon guy is a marketing rep,and it shows too,but he's right for 1 thing,for MC music the player does what it suppose to[bm].

 

[Espen Braathen]

Quote:
"I did a quick search at the Dolby site, but did not find a block diagram showing the DD decoder + bass management. I wanted to see just where the +10 takes place."
It's here:
http://www.dolby.com/tech/L.mn.0002.DDPEG1.pdf
FIG 3-2 and 3-3 gives some clues on how its possible to manage this. Some scaling down in the digital domain and a further analog gain is the best solution.
FIG 3-2 is perhaps more corect for built in DD decoders in players, but these lacks the +15 dB analogue gain stage a shown in the diagram, thus need an external +15 dB bass boost. I'm not sure if these decoders keep the same realtive level, if they do all that's is required is the +15 dB gain. I was under the impression that this was not as simple, but maybe it is after all.
For SACD/DVD-Audio sources the gain adjustments needed seems to vary between players/manufacturers.
Espen Braathen

 

[Brian L]

Thanks Espen, that is the diagram I was looking for.

I did see this document but thought it was specifically for encoders, so I never even opened it.

I will give it a through read.

Thanks.

 

[Brian L]

FIG 3-2 is perhaps more correct for built in DD decoders in players, but these lacks the +15 dB analogue gain stage a shown in the diagram, thus need an external +15 dB bass boost. I'm not sure if these decoders keep the same relative level, if they do all that's is required is the +15 dB gain. I was under the impression that this was not as simple, but maybe it is after all.

Diagram 3-2 is interesting, in that it shows that the analog gain is applied to the summed signals + the LFE. So, maybe I had it right to start with be applying the boost to the signal as it leaves my ICBM?

If I interpret the diagram correctly, the bass that is summed from each main channel is first attenuated by 15 dB, the boosted by 15 dB after the LP filter, thus the summed bass signals when they appear at the sub output are at unity gain with respect to their original levels.

The LFE channel is first attenuated by 5 dB, before it encounters that +15 dB analog gain stage with a net result of +10 dB relative to its original level.

What does that mean WRT these internal decoders? I wish I knew! There are just too many variables, between the decoder, the test software, the functionality of the bass management....unless someone has a block diagram of the decoder in their respective player, then all we can do is guess.

The only thing I know is that the sub channel, when measured relative to any of the main channels with ANY current test software is low, and requires some amount of gain in the signal path for it to equate to main channels.

Why that is, or the correct way to fix it is just not clear to me.

Applying the gain after the ICBM resulted in pleasing results. I have also changed my set-up to adjust levels in the player so that the .1 channel is +10 relative to the mains, and that sounds OK as well, although it is impossible to do any sort of back to back test to zero in on any differences.

I just don't know that EITHER method produces ACCURATE results.

BGL