Bass Effects on Downmixing DD to Stereo and Spectrum Labs information

[Chrisbee]

Thanks Edd. I'll take a tour round the dealers to see what appeals.

[bossobass]

The HK chopped off the first 1 second of audio when changing tracks because it has a feature to mute output from a digital audio connection when the signal is dropped or has no output.

This is why it appeared to be 'dead silent'. Mute function.

Bosso

[Sonnie]

SteveCallas wrote:

I don't find this too bad though, as pressing the button twice on the remote takes me about 1 second.

I figured you for a Home Theater Master, Pronto or Harmony.... one of the learning ones anyway. A macro at turn on solves pressing that button twice. Something tells me you already know this.

[SteveCallas]

bosso wrote:

This is why it appeared to be 'dead silent'. Mute function

Are you referring to the analog outputs being dead silent?

Sonnie wrote:

I figured you for a Home Theater Master, Pronto or Harmony.... one of the learning ones anyway

Nah, I actually like having seperate remotes - no way am I going to spend the time to program all the minute little functions. Also, if I want to keep testing a track on a disc, I can easily adjust receiver settings and work the dvd player with two remotes whereas with a universal I would have to get out of ones functions and go into the other. The only functions I may want to combine are those of the tv and HD cable box, and the universal remote that came with the HD cable box should be able to do that with ease.

[bossobass]

SteveCallas wrote:

Are you referring to the analog outputs being dead silent?


Nah, I actually like having seperate remotes - no way am I going to spend the time to program all the minute little functions. Also, if I want to keep testing a track on a disc, I can easily adjust receiver settings and work the dvd player with two remotes whereas with a universal I would have to get out of ones functions and go into the other. The only functions I may want to combine are those of the tv and HD cable box, and the universal remote that came with the HD cable box should be able to do that with ease.

It doesn't matter, the mute when no signal function applies to the outputs, which are all analog.

Also, I agree with your seperate remotes logic, even a step further as I don't have cable or any sort of TV. Only wealthy bachelors can afford HD cable

Bosso

[SteveCallas]

No TV or cable? No football? How many movies do you typically watch in a month?

As for the HK muting with no signal, I never considered that that might be why it was dead quiet. I'll try muting my Yamaha later tonight to see if I can replicate the dead silence in the tweeters.

[J_Palmer_Cass]

Ilkka wrote:

It did the testing also with this configuration and the result was exactly the same as when you disable the center. 4.1, 3.1, 2.1, 4.0, 3.0, 2.0 - same SPL loss compared to 5.1 or 5.0.


Just like he says, only the DTS part is incorrect. I tested it too and DTS doesn't behave the same. There is no loss if you disable the center or surrounds. DTS doesn't carry any DRC information. Surprisingly DD 5.1 was only around 2 dB behind DTS at the same MV setting (Master and Commander).

So do remember that this happens only when playing DD tracks, DTS doesn't have this problem.

Just as a folow up, I ran some DTS tests on my system.

When I turned the center channel OFF, then DTS sounded the same as the full 5.1 sound.

When I turned the surrounds OFF, then DTS lost 6 dB of peak volume.

I have my mains set to large, and all other speakers are set to small, plus a subwoofer. There is no compression, but there is some type of change in either bass redirection or mix levels (or both) when the surrounds are set to off. I suspect it is simply bass redirection. Not sure if you get the same results if your mains are set to small.

Anyhow, DTS does sound good when you downmix. The downmix of DD sounds bad due that DRC downmix override function!

[J_Palmer_Cass]

SteveCallas wrote:

As for the HK muting with no signal, I never considered that that might be why it was dead quiet. I'll try muting my Yamaha later tonight to see if I can replicate the dead silence in the tweeters.

I have Sony receiver, and from what I can figure out only the analog inputs do not use a mute function. The digital inputs are hard to "listen to" if there is no digital input due to the typical mute function.

Anyhow, if you listen to a passage recorded at a very low volume on any active digital input, you can get a good idea of how quiet your system is. I can't hear any background "hiss" at -5dB from Dolby Reference Level MV settings when I am 1-foot from my speakers, so I am a very happy camper.

WARNING: You must know what you are listening to so you don't get blasted by high volume when you least expect it!

[Jman]

What about the output option? If you set it to 2/0 stereo or 3/2+sw 5.1 there is a big difference in Speclab

[Ilkka]

J_Palmer_Cass wrote:

Just as a folow up, I ran some DTS tests on my system.

When I turned the center channel OFF, then DTS sounded the same as the full 5.1 sound.

When I turned the surrounds OFF, then DTS lost 6 dB of peak volume.

I have my mains set to large, and all other speakers are set to small, plus a subwoofer. There is no compression, but there is some type of change in either bass redirection or mix levels (or both) when the surrounds are set to off. I suspect it is simply bass redirection. Not sure if you get the same results if your mains are set to small.

Anyhow, DTS does sound good when you downmix. The downmix of DD sounds bad due that DRC downmix override function!

That is really strange. I alse tested the same and max peaks were always identical. I could turn off the center, surrounds or both - no change (and my mains are set to large too). AFAIK DTS doesn't contain any DRC info. Which movie (scene?) did you try and which receiver you have?

[Ilkka]

Jman wrote:

What about the output option? If you set it to 2/0 stereo or 3/2+sw 5.1 there is a big difference in Speclab

You should use 2/0 stereo. Spectrum Lab monitors only mains channels, so all the material should be in them. You should also turn off "auto gain control" and "bass redir".

[J_Palmer_Cass]

Ilkka wrote:

That is really strange. I alse tested the same and max peaks were always identical. I could turn off the center, surrounds or both - no change (and my mains are set to large too). AFAIK DTS doesn't contain any DRC info. Which movie (scene?) did you try and which receiver you have?

It is just the bass management of my reciever (Sony STR-DA4ES).

In some modes LFE and redirected bass are sent to both the R & L mains as well as the subwoofer. When I set the surrounds to OFF, then redirected bass goes to the R & L mains only, and only LFE goes to the subwoofer.

It is just a subwoofer calibration issue. I have to set my subwoofer down by 5 dB when LFE and redirected bass are sent to both the mains as well as the subwoofer. Same calibration method you use for running dual subwoofers.

Same issue when I set all the speakers to small. When they are all set to small, I have to add the 5 dB of gain back into the subwoofer input to get my bass back into calibration. I never use the downmix mode, so I never documented the bass redirection of my receiver in those downmix modes.

[eddthompson]

Just to dig this up, i was exploring through the menus in my denon reciver, and lo and be hold there was :

Dolby Digital Downmix Dynamic Range Compression : on/off

well who would have thought if you use less than 5.1, have a look into denons

edd

[Ayreonaut]

That's cool, what model do you have?

I don't see that menu option anywhere on my AVR-1905, but it's one of their lesser models.

[eddthompson]

i have the K-AVC1-SE , i dont know the american model number, but its one of their $3000 amps. I got it used for $1200, the uk is so expensive sometimes, even for used gear.

edd

[J_Palmer_Cass]

Here is a posting from the AVS forum by Rober Dressler (Dolby). This should help out with this issue. It seems like the vast majority of receivers use the DRC ON method when performing "speaker management". It seems like some here have the DRC OFF when downmixing option. My receiver does not have that!


Anyhow, you learn something new everyday!!!


--------------------

Roger Dressler
Advanced Member


Join Date: Jul 2000
Location: CA
Posts: 916 Quote:
Originally Posted by SpectralD
Unfortunately, it is actually in the Dolby spec that DRC is engaged whenever downmixing occurs. Shockingly, this includes downmixing LCR -> LR. They refer to it as 'overload protection DRC' in the docs.

Go figure.

Allow me to clarify. Downmixing can take many forms. In a DVD player, a 2-ch downmix is always (I have not seen an exception, but who knows) done with DRC activated. This ensures the average level is maintained while preventing clipping.

In an AVR, 2-ch downmixes will probably be done the same way. However, if it is desired to downmix without DRC, every Dolby Digital decoder IC knows how to do it. The output level is scaled down 11 dB, then there's no way to cause clipping.

In the case of "speaker management" as descibed here, the AVR may allow the decoder to run in full 5.1 mode, no DRC, then downmix the C into L/R with the usual -3 dB mix level. With a little bit of scaling in the DSP, clipping can be prevented, and the gain is made up in the analog stage.

The AVR maker can use this method, or they can use the "downmix in the DD chip with DRC on" method. It's their choice.

The tests described by others will show which mode the AVR is using.

__________________
Roger

[Ilkka]

eddthompson wrote:

Just to dig this up, i was exploring through the menus in my denon reciver, and lo and be hold there was :

Dolby Digital Downmix Dynamic Range Compression : on/off

well who would have thought if you use less than 5.1, have a look into denons

edd

Many receivers do have DRC control (mine too), but it doesn't seem to affect while downmixing (ie. it's overruled). Could you check whether your Denos does this too? Just run a short dynamic scene with center on and off. Check the peak SPL with your SPL meter. Are they identical?

[J_Palmer_Cass]

Ilkka wrote:

Many receivers do have DRC control (mine too), but it doesn't seem to affect while downmixing (ie. it's overruled). Could you check whether your Denos does this too? Just run a short dynamic scene with center on and off. Check the peak SPL with your SPL meter. Are they identical?

Ilkka,

That DRC control is not the same as our DRC control.

The optional control that Ed has is special (and optional). It refers to downmixing in particular. Not sure how many receivers in any price range have that option.

"Dolby Digital Downmix Dynamic Range Compression : on/off"

Anyhow I use a full 5.1 system, so this it does not even apply to me right now. I was considering not using a center speaker in a second system that I am putting together, but I gave that idea up a while back after I figured out this DD downmix mess. The funny thing is that many people still insist that you can live without a center channel. If you question them, they respond like it's like a personal insult.

Put down the Sony STR-DA4ES in the DRC is applied during DD downmixing pile!

[SteveCallas]

The funny thing is that many people still insist that you can live without a center channel. If you question them, they respond like it's like a personal insult.

Lol In regards to audio, some people can't handle the truth.

[Ilkka]

Sorry, I thought Ed meant the "normal " DRC. Though I would still like to see him testing it.

Many people insist that you can live without a center channel speaker. I was one of them until I discovered the DRC thing. I don't need center channel speaker for sound stage etc. because I always sit at the sweet spot. But due this DRC thing I now have to consider buying it...

[SteveCallas]

I was one of them until I discovered the DRC thing. I don't need center channel speaker for sound stage etc. because I always sit at the sweet spot. But due this DRC thing I now have to consider buying it...

Well not only are you going to get better highs and lows, you are going to spread the workload out over more speakers. Assuming you buy a third identical speaker, aside from having to spend money, this is a good thing.