Center Speaker

[petern]

Hi all,

New here, and though I have plenty of experience I have some fundamental questions.

Can someone explain, or perhaps better, point to information as to what the ramifications are regarding what I'll call "center channels" in live sound? In many shows (I do mostly folk shows), I like to add a hot spot style speaker at center stage, especially for the vocals, as I fine the mains to be too far removed to provide vocals both clarity and the right "location" especiallly for audience close to the stage.

My understanding is there can be some theoretical issues regarding sound waves and the combing effect, but certainly it simply sounds better (to me at least) when I add a "hot spot".

With home and theater sound systems having center channels, this has to be OK to a degree, though I don't know if there is additional technology that addresses any issues like combing. I assume there isn't a "crossover" type technique that simply pulls frequencies for the center channel.

[Hugh Robjohns]

Comb-filtering is only going to be a (potential) problem if you route the same sound into more than one speaker at similar levels. If you use the centre speaker only for vocals, and don't put vocals in the sides, there won't be a problem at all!

If you do put vocals in the sides as well, (and other stuff in the centre) then there could, potentially, be regions across the audience where the sounds from the side and near speaker interact in a deleterious way -- the time of arrival differences causing phase shifts that partially cancel some frequencies of different sound elements. However, if the sound contributions from the two speaker sources is substantially different, the cancellations will be minimal and it probably won't become a significant problem anyway.

H

[petern]

Thanks for the quick response Hugh,

Yes, that is my general understanding, though when I llisten around the room, it doesn't seem to be an issue, even if I don't make an effort to make any adjustments. Perhaps it also has to do with speaker locations.

Any further advice or direction is apprciated.

Peter

Comb-filtering is only going to be a (potential) problem if you route the same sound into more than one speaker at similar levels. If you use the centre speaker only for vocals, and don't put vocals in the sides, there won't be a problem at all!

If you do put vocals in the sides as well, (and other stuff in the centre) then there could, potentially, be regions across the audience where the sounds from the side and near speaker interact in a deleterious way -- the time of arrival differences causing phase shifts that partially cancel some frequencies of different sound elements. However, if the sound contributions from the two speaker sources is substantially different, the cancellations will be minimal and it probably won't become a significant problem anyway.

H

[resistorman]

In theater systems, the center channel is usually just for dialog. The channels are separated out for different functions at mix. https://en.wikipedia.org/wiki/5.1_surround_sound

[Sam Spoons]

I've used centre fills where the audience is close to a large stage, running them a good bit lower than the main FOH seems to work, they are only for the benefit of the centre seats of the front few rows (or those standing in equivalent positions) who won't be hearing the main, flown, FOH. If it sounds right it's probably fine.......

[Bob Bickerton]

The technique of putting vocals through a centre cluster of speakers is fairly common in music theatre and one which I’ve used successfully. It helps get around the problem of an actor’s voice coming from a side speaker when they are centre stage, which can be off-putting if youre sitting next to the side speaker!

However, this is still a compromise as you could have an actor far stage left or right, or moving from one side to the other, yet their voice is still coming from the centre position. I believe in certain high class professional production this is addressed using considerable technical trickery.

I’ve never felt the need to do this with music, or folk music for that matter. Music theatre is often trying to create the illusion that the actors are not miked, whereas if you have a musician standing in front of a microphone the impression given is that it is being amplified!

I haven’t used a venue yet where some seats are not compromised (though the perception of what constitutes compromise varies between individuals). Picking a seat that suits is the punter’s prerogative.

Centre fill, on the other hand is a different issue and necessary if coverage from the main speaker array is insufficient to cover the front centre seats (as Sam notes).

Bob

[MarkPAman]

It still surprises me how effective even a very small speaker at low volume can be for those sitting close to the stage.