Phantom centre vs centre, AVR sound mixing

[Evo42]

Just after some advice to try and understand how AVRs mix centre channel content with left and right fronts vs fronts with a centre. I appreciate that a lot of movie content and dialogue in a LCR speaker setup across the front is directed to the centre speaker. In a two speaker setup I assume the AVR is essentially splitting that dialogue and other ordinarily centre channel content across both speakers.

So assuming all speakers are the same does that mean in a two speaker setup that because the centre channel content is presented through both speakers there is a wider soundstage and volume compared to if it was solely channelled through the centre speaker?

I fully appreciate that the centre is required to anchor dialogue to the screen and when you move off axis with only two speakers that effect diminishes.

I have unique setup(pic attached) and after looking at hundred options to replace my passive soundbar I've settled on the best option being two kef q150 on their side or two q250c. I am potentially considering two q150s and the centre however with such a narrow area of placement 1-1.5m I am wondering whether it's even worth it depending on the answer to query above( ie. could just L & R potentially work better)and that fact I am trying to minimise visual impact.

FYI have 5.1.2 setup with a Denon x1800h just looking to improve the LCR or L & R aspect of the setup.

 

[NTK]

Just after some advice to try and understand how AVRs mix centre channel content with left and right fronts vs fronts with a centre.

Upmixing from 2 channel to multi-channel is far from a trivial process, and we are quite a way away from perfecting the process. Extracting the sound source directional info from the left and right channels isn't easy nor simple. (For example, amplitude panning is simpler to detect and extract, time delay panning is much much more difficult.) There is no guarantee that the results are always acceptable. Simply summing the left and right channels to produce the center will have the effect of narrowing the soundstage. (For example, if you have a sound hard panned to the left, summing left and right to produce the center will "leak" the hard panned left sound to the center, and thus move the apparent sound source closer to the center than with the 2 channel version.)

Below is from the conclusion of this paper titled "Upmixing to Multichannel Audio" by a Masters program student at Aalto University in Finland.

https://mycourses.aalto.fi/pluginfile.php/2254357/mod_folder/content/0/9%20Upmixing.pdf

 

[DVDdoug]

I think we're talking about downmixing...

assuming all speakers are the same does that mean in a two speaker setup that because the centre channel content is presented through both speakers there is a wider soundstage and volume compared to if it was solely channelled through the centre speaker?

I'd say I perceive a "vague" center with regular 2-channel stereo. Some people seem to get a more precise center.

Theoretically, the volume will be the same with -3dB (half power) from the center mixed-into left & right.

But... I read in Floyd Toole's book that there is an effect with stereo related to the distance between your ears (or something) that makes a slight dip around 2kHz and that affects intelligibility. If the mixing engineer is mixing in stereo, he'll compensate for that and it will sound normal but of course if he's mixing with a center speaker the mix will be optimized for a real center. Mr. Toole also says, "the center is the most important speaker."

And of course, with a real center you can bump-up the dialog a bit. A lot of people like to do that because they aren't listening at "theater volumes" and with the loud effects adjusted to a comfortable volume, the dialog ends-up too low.

 

[Evo42]

Thanks for the replies. Good point being able to adjust the volume of the centre independently. I've been thinking having the three in a row is perhaps a more seamless look in any case. I notice the new q series doesn't have the smaller centre so will probably just get the q150 and q250.

 

[StigErik]

Theoretically, the volume will be the same with -3dB (half power) from the center mixed-into left & right.

You may experience as I did, that the center channel content played back by the L and R speakers becomes 3 dB too loud.