Bass Effects on Downmixing DD to Stereo and Spectrum Labs information

[Ayreonaut]

Chrisbee wrote:

The tip to try setting the centre to small when none is present sounds good.

Wouldn't that just redirect the CC bass, but toss away all the rest of the CC info?

[brucek]

Wouldn't that just redirect the CC bass, but toss away all the rest of the CC info?

Yeah, makes no sense to me...........

[eddthompson]

i think it was merely to test the spl at a set volume, centre on, and centre off, to find out if the drc is affecting the spl.

ie, at -10 on the reciver, centre to on (even if theres no centre) measure the spl of your fave scene, then do the same with the centre set too off. The theory goes that with the centre off the drc will lower the total spl. which is bad, of course this doesnt apply to dts.

edd

edit: spl=sound pressure level drc=dynamic range compression, too manuy accronyms

[Chrisbee]

I'm afraid this idea crashed and burned via my DVDP (no receiver) based system.

No dialogue!

Pardon?

I said; "No dialogue".

[SteveCallas]

Yeah, you won't be able to use it as a permanent method, but as a test, you should be able to notice the difference in bass output with the center and surrounds "on".

[Chrisbee]

But isn't it rather academic if I can't hear the dialogue?

It's rather like saying you can save fuel by not starting your car.

[eddthompson]

no its like saying alter your system to have a centre, or only listen to dts track, or suufffeeerrr terrible dynamics.

edd

[Chrisbee]

DTS deosn't work on DD only films.

[eddthompson]

exactly, suffeerrrrrrrrrr

Back of amp im assuming this is the back of your e800, if so have you tried using it purely as a 5.0 preamp? ignoring any of it processing and just using the ext decoder in from your dvd player? can you not run a centre much like you run you rears? after all sound quality may not be hugely important on the centre compared to the extra quality gained from the increase in dynamic range.

edd

[Chrisbee]

My dynamics are still better than your dynamics!

[eddthompson]

if the dynamics are crushed on the out put, i could be realy screwing up the sound, thats all im worried about, especialy as you have such an awsome sub, i recall u saying lotr was an amazing experience, possibly because you used the DTS track? have you compared it to the DD track, if there is a huge difference in quality, sub output, dynamics etc, then it sounds like this sneaky drc stuff is causeing you grief. i just think it seems to be the issue we had a discussion about not long ago, i wasnt being nasty, just slightly cheeky

edd

[Chrisbee]

No worries, Edd! I was just winding you up too.

I haven't tried DTS because I get no sound when I try and play a DVD in DTS mode.

If I wasn't so lazy I'd have a dig round in the DVDP instructions to find out why. Probably some obscure choice in the menues.

I'm still trying to locate a matching Centre speaker but the old Mission 75C Freedoms don't come up very often on the used market.
Getting a used one sent over from England would easily double the secondhand sales price in postage.

I'm also looking at mid-price AV Receivers. Thought I might get a matching NAD to go with my DVDP. Only because I like the colour.

[eddthompson]

Thats ok then, thought id insulted you, im dyslexic and my posts often are misunderstood, due to my inability with writen language.

If you find one in england id be happy to foward it to you, although i bet shipping would still be prohibative.


edd

[Chrisbee]

Thanks for the kind offer Edd.

I'm still hoping I can find one over here before resorting to Parcelforce.

[eddthompson]

parcel force all other avenues must be looked into



edd

edit: at the cost of flights ill fly it over and visit lovely finland (£150) lol, well, i think your in finland, my memeory fails me, or was it denmark, i get confused, i have to many multi nations aquaintenses.

[Chrisbee]

eddthompson wrote:

parcel force all other avenues must be looked into

I know! I know!

When I think of the times the carriage has exceeded the cost of the goods it makes me want to cry. It might be cheaper to fly over except for the time it all takes going both ways.

[eddthompson]

lol, i think you missed my edit!!

edd

[SteveCallas]

Chrisbee, I have done blind testing of processing only going from a really entry level receiver to a dedicated pre/pro renowned for it's sound quality. When you feed them all to the same amp, so the receivers are only being used as pre/pros, they all sounded exactly the same. See here if you are interested. So if you have some beefy, discrete amplification, you really wouldn't be giving up any sound quality, and you'd be gaining a lot of capability.

As for the center channel, at the moment, it's like a hole in your sailboat while you're out on the sea.....plug it up now - you can do the more elegant repair later (add another Mission 755C). All joking aside, you are currently getting a pretty watered down experience Plug that hole!

[Chrisbee]

Steve

I read that blind review a while ago but never realised you were involved. No wonder they don't like you on AVS.

Since I don't need most of the amplification in an AV receiver, don't need HD and I'm not stretching to a processor the task merely becomes one of selection. What you are basically saying is that if I like the look of the fascia then that's about it? But that's what we've all beeen doing for years, isn't it!

[Ayreonaut]

Dolby Digital Guidelines
This document contains guidelines from several Dolby Laboratories publications

In addition to the DRC profile, metadata can limit signal peaks to prevent clipping during downmixing. This metadata, known as overload protection, is inserted by the encoder only if necessary. For example, consider a 5.1-channel program with signals at digital full scale on all channels being played through a stereo, downmixed linelevel output. Without some form of attenuation or limiting, the output signal would obviously clip. Correct setting of the dialogue level and DRC profiles normally prevents clipping and unnecessary application of automatic overload protection.

[Ayreonaut]

From "All About Audio Metadata"

Downmixing

Downmixing is a feature within Dolby Digital that allows a multichannel program to be reproduced by fewer speaker channels. Simply put, downmixing allows consumers to enjoy a digital television broadcast without requiring a complete 5.1-channel home theater setup.

As with stereo mixing, where the mix is monitored in mono on occasion to maintain compatibility, multichannel audio mixing requires the engineer to reference the mix with fewer speaker channels to assure compatibility for downmixing situations. In this way, metadata allows Dolby Digital to be an “equal opportunity technology” so that every consumer who receives a Dolby Digital data stream will be able to enjoy the best audio reproduction possible irrespective of the number of channels in their playback system.

Set-top boxes for terrestrial, cable, or satellite digital television will typically offer a mono signal on the RF/Antenna output, a line-level analog stereo signal, and a optical or coaxial digital output to convey the Dolby Digital stream to a decoder.

The analog stereo signals that are output from these units are most often internally downmixed from the original Dolby Digital multichannel audio program to ensure compatibility with nondigital home theater systems. This analog output can be one of two different types of stereo signals. One type is a stereo-compatible Lt/Rt (Left total/Right total) downmix suitable for Dolby Surround Pro Logic decoding. The other type is a simple stereo Lo/Ro (Left only/Right only) downmix suitable for playback on a stereo hi-fi or via headphones. That same signal is used for deriving the mono signal for use on the RF/Antenna output.

Certain metadata parameters allow the engineer to select which stereo analog signal is preferred as the default signal at these output connections and how that stereo downmix is constructed. In addition, within the metadata parameter library there are separate parameters for the adjustment of the Lo/Ro and Lt/Rt downmix conditions.

During downmixing, the adjustment of dynamic range control parameters is limited, and this is no different when using the signals present at the stereo or RF/Antenna outputs. The mono signal present at the RF/Antenna output of a set-top box will be applied with maximum DRC (RF Mode Profile) at all times to help prevent RF overmodulation. Certain metadata parameters assist in achieving an appropriate downmix, helping to ensure that the intention of the engineer/content producer will translate across these environments. Specifically, metadata provides control over how certain speaker channels are “folded” into the resulting downmix.

While the engineer must optimize the multichannel mix for reproduction in an ideal listening environment, it is important to preview the mix in downmixing conditions to ensure compatibility with different playback systems when selecting the downmixing metadata parameters. These previews can be achieved in real time using the DP570 Multichannel Audio Tool.