[Rialas]

Just curious, as I would have thought a centre speaker would destroy the left/right sound-field.
Music engineers pan musical instruments in a studio placing them the in the stereo sound field.

Can't quite see the point or maybe I'm missing something?

Sorry, just killing time in the cafe.

[shadow191]

It's not just a BMW gimmick, many cars come with center speakers now. My Infiniti has a center speaker as well. Basically it just provides fill which is not needed if you have a proper set up.

[JK330i]

I think the centre speaker is probably an attempt to move the imaging / sound-stage to the front of the car, and away from the sides. Assuming there is a tweeter involved, it may have some benefit.

Not listened to a car with it factory fitted, so not sure how successful it is.

[Rialas]

Hi Jk, not sure that would be successful if that's their goal.

If the centre is taking the sum of both channels, then if a guitar is panned to the left (as an example), then that guitar will sound as if it's nearer the centre, as opposed to where the music producers intended it to be. All wrong imho.

Only benefit of the centre would be speech for film/movies, not something that most who a quality system would be interested in.

[jeffb335]

At a basic level the audio info that exists equally in both channels (which is centered in the mix) is sent to the center channel, the audio info that exists in the far right and left stays on the far right and left.

The idea is to create a left-center-right soundstage in a car environment where the listeners are sitting in an off center location.

This is now commonplace and in most cases standard on most moderate to high end cars.

[cdgatti]

Jeff do you know a way that a center channel can be simulated by adding or subtracting left and right channels like you can with a dsp?

[taibanl]

Originally Posted by cdgatti

Jeff do you know a way that a center channel can be simulated by adding or subtracting left and right channels like you can with a dsp?

Andy wehmeyer has posted on DIY mobile audio about how this works.

You definitely need a processing algorithm because it is information that is only common to right and left channels as jeffbe 335 says

Mathematically that looks something like left plus right, minus left minus right & right minus left

[techwhiz]

Not a gimmick.
My Chrysler Pacifica also has a center speaker with upgraded sound.

[cdgatti]

Originally Posted by taibanl

Andy wehmeyer has posted on DIY mobile audio about how this works.

You definitely need a processing algorithm because it is information that is only common to right and left channels as jeffbe 335 says

Mathematically that looks something like left plus right, minus left minus right & right minus left

tai you got my attentionL

are you saying?

(L+R) + (-L-R) + (R-L)

can you check this because this looks like it would collapse to:

R-L

[taibanl]

Originally Posted by cdgatti

tai you got my attentionL

are you saying?

(L+R) + (-L-R) + (R-L)

can you check this because this looks like it would collapse to:

R-L

Andy has posted it but its something like

(L+R) -((R-L)+(L-R))

[cdgatti]

Originally Posted by taibanl

Andy has posted it but its something like

(L+R) -((R-L)+(L-R))

thanks Tai - from an algebraic standpoint I can't see how that results with a center channel. BUT - logically it makes sense. the first term (L+R) gives you a full signal mono to start with, it would be L+R + all center information contained in the L + R. Then subtracting the quantity of the addition product of the R ambiance and L ambiance information, you should be left with the center information. Makes sense... now how can we do this with a Helix DSP? The Helix can take 4 inputs of L and R to make the output and each input can be in phase (+) or out of phase (-). Will have to stew on this one.

[jeffb335]

Yeah, you guys got it.

a lot of processors do this in one way or another...although with a processor and time alignment its not really necessary.....well....not for a single listening position at least.

Here is another Andy W quote that explains center channels (in this case related to the Logic 7 in the MS-8)

"Yes, the center image is something to get used to, especially if you're used to listening to simple stereo. The real benefit of a center channel and signal steering in cars is that the center image isn't created by the sum of the left and right speakers as it is in simple stereo. Information that's common to both left and right is sent to the center and atenuated by 6dB in the left and right. The difference between this arrangement and the common L+R (mono center) is that configuration narrows the stage by design. With Logic7, Left is still left and right is still right. If the center is too dominant, try turning the center channel level control down a bit."

[Rialas]

Originally Posted by cdgatti

Makes sense...

Well it doesn't to me Lol.

But thanks to everyone for the info.

I'm back in a coffee shop, and I need to get my had around it. Cheers.

[Rialas]

Well some of the physics and mathematics are a little over my head.

From a musicians point of view (me) .
There's no such thing as "hard" left and right, and there are very few instruments that sit bang in the middle of a stereo field.
Bass drum, snare drum, bass guitar, and vocals usually panned dead centre. Other instruments are panned left and right at varying percentages from the centre.

A processor will have no idea what I want centred on a third speaker. And why should it decided.

Besides, instruments that are panned centre, will sound as though they are coming from the centre from only 2 speakers, no need for a third.

Jeff, the unit I've bought will adjust the volumes independently to offset the driving position that you mention.

I have many friends who are in the studio business, and a common practice would be to mix a track, then listen to it in a car to get an idea of what they've produced. I don't think any of those musicians would want a third speaker or any processing messing with there work.
That would be like adding salt to a masterchef's recipe.

Although I may be completely wrong and technology does acoustic things that I just don't understand.

[jeffb335]

Originally Posted by Rialas

Although I may be completely wrong and technology does acoustic things that I just don't understand.

Yeah, processors do things you currently dont understand...but your knowledge of live and studio staging is correct...so let me try to tie it together for you.

This is car audio, not live performance or studio....you are sitting to the side of the car, not the center, the audio from the near side reaches you first, that causes your brain to perceive the center as skewed to the near side and collapses the soundstage. People often think that the near side speaker is closer and therefore louder and thats why the sound is skewed....nope, not the case. Its because the sound on that side reaches you first, our ears are REALLY good at this, its how we can localize the source of sounds in our environment....its why we have 2 ears....sure you can override this with changing the balance but thats fairly ineffective as our ability to hear the slight difference in timing is actually MUCH stronger than the effect of relative volume. Virtually no stock car stereo (without processing) has a decent soundstage because of this.

Time alignment processing can compensate for this by delaying the near side speaker sound to reach you at the same time as the far side sound, this effectively puts you in the center of the speakers and restores the soundstage. Virtually all processor do this, its extremely effective. BUT this only works for one side of the car....the other side will suffer as the delays are opposite AND in the wrong direction on that side.

Thats where center channel speakers come into play, they can place sounds that are mixed center in the recording into the center of the car so you get decent center sounds from either side of the car while not compromising the left or right sounds.

We are talking about left, right, and center, as discrete locations in the soundstage for simplicity sake, in reality there are of course an infinite amount of locations left to right, but a processor takes that into account depending on how far left right or center in the mix the sound is and balances the sound between the left right and center channel depending on how far right or how far left it should be.

In a perfect listening environment we only need a left and right speaker. But the car is not perfect.....in fact its a disaster as a listening environment. Center channels and the processing that goes with them are one approach to dealing with that.

[Rialas]

Thanks Jeff. I think I could get my head around this if for example the centre speaker was acting as my left speaker, and at the same time the same centre acted as the passenger's right speaker. Then both would have ideal positioning? Again possible with dsp I guess.

My major problem right now is my wife allowing me to turn the volume up.
As long it sounds good from my side I'm ok.

[jeffb335]

In car audio the typical goal in creating a sound stage puts the perceived center in the center of the hood, at eye level, with the stage stretching the width of the car (or wider in a best case scenario). The "center" in a car is typically NOT dead center in front of the listener.

This results in the perception that you are listening to a live performance somewhat left or right of center, mirroring your position in the car.

How that is accomplished is a combination of time alignment, ambient sounds from the rear speakers, the mix of front left, right, and center channel speakers, the driver locations, and the basic acoustics of any given vehicle....

When done well you dont hear the speaker locations, you only hear the instruments in their intended point in space. Frankly I think you are underestimating the power of digital sound processing and a good car audio system....

[Rialas]

Thanks Jeff, I still feel I need to understand what's going on when music is being processed by these clever devices. I really don't feel I'm missing anything with a regular system. The setup I have now is pushing 600w. That's way over what I set out to achieve and sounds unbelievable...to me...
Don't want to drag this out any longer.

[jeffb335]

find a few good car audio shops and ask for a demo of a nice SQ setup, owners car, whatever.

Or spend a little (or A LOT) of time here..... http://www.diymobileaudio.com/forum/...io-discussion/ .....and see how deep the rabbit hole goes....

[taibanl]

Originally Posted by Rialas

Well some of the physics and mathematics are a little over my head.

From a musicians point of view (me) .
There's no such thing as "hard" left and right, and there are very few instruments that sit bang in the middle of a stereo field.
Bass drum, snare drum, bass guitar, and vocals usually panned dead centre. Other instruments are panned left and right at varying percentages from the centre.

A processor will have no idea what I want centred on a third speaker. And why should it decided.

Besides, instruments that are panned centre, will sound as though they are coming from the centre from only 2 speakers, no need for a third.

Jeff, the unit I've bought will adjust the volumes independently to offset the driving position that you mention.

I have many friends who are in the studio business, and a common practice would be to mix a track, then listen to it in a car to get an idea of what they've produced. I don't think any of those musicians would want a third speaker or any processing messing with there work.
That would be like adding salt to a masterchef's recipe.

Although I may be completely wrong and technology does acoustic things that I just don't understand.

I am also a musician with a decent amount of recording experience. Actually having gotten used to the logic7. Processing, I now realize the follies of our ways some years ago when we recorded an album.

The better mixed albums that I now listen to have stereo separation on pretty much every instrument, usually the drums are near center but you can hear a drumroll somewhat from left to right with good sound staging

It now annoys me when makes engineers mix a mostly centered image

Logic seven and its use of the center speaker really are used to enhance stereo separation and sound staging not to detract from it or are you mix the work of the engineer, in fact it can't really remix the work of the engineer

The center speaker comes in handy to minimize the compromises in imaging when you have to optimize for more than one seating position

Even in a logic seven system, the center speaker can end up being completely useless if you're only trying to set up a soundstage for one sitting position i.e. the driver

Most people want to create a somewhat decent image for their passenger as well and that is where the center speaker makes its money

[Rialas]

Originally Posted by taibanl

I am also a musician with a decent amount of recording experience. Actually having gotten used to the logic7. Processing, I now realize the follies of our ways some years ago when we recorded an album.

The better mixed albums that I now listen to have stereo separation on pretty much every instrument, usually the drums are near center but you can hear a drumroll somewhat from left to right with good sound staging

It now annoys me when makes engineers mix a mostly centered image

Logic seven and its use of the center speaker really are used to enhance stereo separation and sound staging not to detract from it or are you mix the work of the engineer, in fact it can't really remix the work of the engineer

See.... This is what I'm talking about.
Two musicians and between us, we can't agree where the panning of instruments should be. You've admitted that logic 7 messes with the sound to give better stereo separation which is to your taste.
I don't want that, I want the instruments where I've placed them.

Yes most instruments are spread around the field.
But drums? In the 80's It was fashionable to hear the toms going left to right, but not anymore. In fact the opposite now. Hi-hats used to be panned slightly to the side, but again a lot of us like them bang in the middle.
At a gig, do you see a Hi tom-Tom at one side of the stage, and the left Tom-Tom on the other? The whole kit is in the middle with musicians either side.
Or maybe there's a progressive engineer who wants the drummer left to the bass player? There choice.

Logic 7, don't mess with my sound. Kinda like the stereo-wide effect button we had on our portables that we all thought was magic.

[taibanl]

Originally Posted by Rialas

See.... This is what I'm talking about.
Two musicians and between us, we can't agree where the panning of instruments should be. You've admitted that logic 7 messes with the sound to give better stereo separation which is to your taste.
I don't want that, I want the instruments where I've placed them.

Yes most instruments are spread around the field.
But drums? In the 80's It was fashionable to hear the toms going left to right, but not anymore. In fact the opposite now. Hi-hats used to be panned slightly to the side, but again a lot of us like them bang in the middle.
At a gig, do you see a Hi tom-Tom at one side of the stage, and the left Tom-Tom in the other? The whole kit is in the middle with musicians either side.
Or maybe there's a progressive engineer who wants the drummer left to the bass player? There choice.

Logic 7, don't mess with my sound. Kinda like the stereo wide effect button we had on our portables that we all thought was magic.

Actually, you're assuming things I did not say. The processing is intended to reproduce the soundstage as mixed to the ensure that mix is faithful to the listeners ear in a vehicle which is a challenging environment.

In that sense it is not like Dolby which attempts to create a new image

The best way I can describe it is that if you had a perfectly tuned and time aligned stereo system on two speakers, the logic seven will be perfectly tuned to you here in the seat position in the car either using two or three speakers (with the center).

The processing is compensating for the listener setting off center.

The presence of a center speaker if used, will compensate for more than one listener in a different position