# How can I run a center channel?



## Termix84 (Apr 8, 2015)

Ok so I have been trying to figure out how to incorporate a center channel into my system. I am currently running a miniDSP 2x8. I am running full active crossover to my front 3way setup. I have just ordered another miniDSP 2x8 so I can add more channels. My question is how do I get the right signal from my headunit to create a center channel? Do people use the left and right channels together to make a center mono channel?


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## brumledb (Feb 2, 2015)

You need a DSP with center channel steering like the MS8 (Logic7) or Alpine H800 (Pro Logic II). A true center channel is different than simply playing a sum of both L+R.


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## axipher (Oct 7, 2015)

brumledb said:


> You need a DSP with center channel steering like the MS8 (Logic7) or Alpine H800 (Pro Logic II). A true center channel is different than simply playing a sum of both L+R.


If I'm not mistaken, a typical center channel will output a summed input of the L + R channels then subtract from it whatever only appears in the L or R channels so you are left with just the stuff that's in both.


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## brumledb (Feb 2, 2015)

axipher said:


> If I'm not mistaken, a typical center channel will output a summed input of the L + R channels then subtract from it whatever only appears in the L or R channels so you are left with just the stuff that's in both.


A center channel does only play the common info between L+R, but you need a way to extract that info from the summed signal. I don't think the minidsp does this. You need a dsp with surround sound type processing which is the MS8 and the H800.

I love quoting Andy.



Tendean17 said:


> *
> ______________________________________________________________
> 
> Andy Wehmeyer :
> ...


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## 1996blackmax (Aug 29, 2007)

miniDSP has a center/rear channel plug-in.

https://www.minidsp.com/images/documents/Product Brief-Rear-Center channel plug-in.pdf


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## brumledb (Feb 2, 2015)

1996blackmax said:


> miniDSP has a center/rear channel plug-in.
> 
> https://www.minidsp.com/images/documents/Product Brief-Rear-Center channel plug-in.pdf


Unless the plug-in has been updated since this post, then it is still not a true center channel. It is only summing the two channels. It is not extracting and playing ONLY the common info between R+L.

https://minidsp.com/forum/minidsp-for-newbies/10705-center-channel-signal-improving-upon-l-r

And Fyi... Trumpet from the above post used an MS8.


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## 1996blackmax (Aug 29, 2007)

Correct....The heading was a little misleading. It said either L+R or L-R. Under the applications it's pretty clear. L-R is for the rear fill speakers. Thanks for clarifying it.


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## Termix84 (Apr 8, 2015)

Thank you all for the responses. I don't really want to get another DSP to run a true center channel.


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## 1996blackmax (Aug 29, 2007)

You can try the plug-in since you've already purchased the 2x8. If nothing else, it gives you the rear fill option as well.

I was actually looking at it for rear fill duty. I already tapped into the center channel output of my OEM system & ran it through my DSP.


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## Maylar (Dec 6, 2012)

In practical terms, what is the downside to using L+R summed together (analog)? I'm considering doing that for my 99 Buick, and I'm pretty sure that the OEM amplifier didn't have any fancy DSP capabilities.


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## axipher (Oct 7, 2015)

Maylar said:


> In practical terms, what is the downside to using L+R summed together (analog)? I'm considering doing that for my 99 Buick, and I'm pretty sure that the OEM amplifier didn't have any fancy DSP capabilities.


If there is an instrument off to the far right, it will now also show up in the center channel so it won't seem as far right.

If anything I want to guess that adding a summed center channel will pull everything present on both channels closer to the center, but also everything else towards the center a little bit as well.


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## t3sn4f2 (Jan 3, 2007)

Maylar said:


> In practical terms, what is the downside to using L+R summed together (analog)? I'm considering doing that for my 99 Buick, and I'm pretty sure that the OEM amplifier didn't have any fancy DSP capabilities.


AC: "Too much mono". Lol IOW collapsed to the center.......stage.


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## Patrick Bateman (Sep 11, 2006)

Termix84 said:


> Thank you all for the responses. I don't really want to get another DSP to run a true center channel.


Creating a center channel is an art and a science. I have Dolby PL II at home, and Lexicon Logic 7 in my Genesis, and they both sound different.

Whatever you do, don't even think about trying to DIY this; deriving a center channel is best left to the experts. Jim Fosgate (of Rockford Fosgate) spent literally decades working on the right balance for Dolby ProLogic II.

I looked high and low for a solution that would work in the car and wouldn't break the bank. 'Cajunner' found one on eBay that does it for about $20:

http://www.diymobileaudio.com/forum...iscussion/210570-five-channel-soundstage.html

Editorializing for a minute, I haven't decided if five channel sounds better than two channel. It's still a bit of a toss up. And I've had a five channel system for four years now. I guess that's a good sign though? The fact that I've been running a processor that turns two channels to five, and I like it enough that I haven't gone back to stereo.

I can't think of any good reason NOT to run four channel though. The back channels make an unmistakable improvement. The center channel is a bit more of a toss up.

I also find that simply putting a tweeter in the center works pretty darn well. Maybe even preferable to Dolby PLII. The reason that putting a tweeter in the center works so well is because our perception of high frequency location is based on amplitude, not phase. So if you have a really well behaved tweeter in the center of the soundstage, the width doesn't collapse. The same is not true of adding a full-bandwidth speaker. When you put a full bandwidth speaker in the center of the stage, it has a tendency of reducing the width of the stage. This is due to phase; at midrange frequencies and lower, the phase cues introduced by a full range speaker in the center of the stage 'pull' the width inwards.



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## Patrick Bateman (Sep 11, 2006)

Termix84 said:


> Thank you all for the responses. I don't really want to get another DSP to run a true center channel.


If you want a dead-simple way to fill in the hole in the center, do this:

1) get a MiniDSP
2) get a four channel amp
3) get the plugin for a mono sub from miniDSP
4) Now wire up four channels like this:

a) one tweeter in the center of the dash, playing two octaves from 5000hz and up
b) a left speaker playing six octaves from 80hz to 5000hz
c) ditto for the right
d) a subwoofer playing two octaves from 40hz to 80hz

It's preposterously cheap and simple and it sounds good. Basically the way that this works is that high frequency cues don't need to be in stereo. There's a thesis paper from Dr Kenneth Pohlmann in Florida that explains how this works. So the tweeter in the center 'fills in' the hole in the center. It takes advantage of the fact that one of the MiniDSP plugins, designed for a mono sub, can also be used for anything mono... Such as a mono tweeter.

It sounds bizarre that a single tweeter would sound better than a stereo pair, but it works. Eliminates comb filtering and it still sounds stereo because there are plenty of stereo cues in the midrange, arguably it's the midrange that really gives you the cues.

I've posted a few threads on this. The oldest one is called 'anyone tried using one tweeter?'


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## brumledb (Feb 2, 2015)

Patrick,

In regards to rearfill:

Do you think it is necessary or preferable to use PL II or Logic 7 so that the ambient (out of phase) info can be extracted and funneled to the rears? Or do you believe it is sufficient to use a driver that is bandpassed from say 100hz to 5000hz with a 20mS delay?


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## Patrick Bateman (Sep 11, 2006)

brumledb said:


> Patrick,
> 
> In regards to rearfill:
> 
> Do you think it is necessary or preferable to use PL II or Logic 7 so that the ambient (out of phase) info can be extracted and funneled to the rears? Or do you believe it is sufficient to use a driver that is bandpassed from say 100hz to 5000hz with a 20mS delay?


I don't know enough to answer that, I've never tried it


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## garysummers (Oct 25, 2010)

brumledb said:


> Patrick,
> 
> In regards to rearfill:
> 
> Do you think it is necessary or preferable to use PL II or Logic 7 so that the ambient (out of phase) info can be extracted and funneled to the rears? Or do you believe it is sufficient to use a driver that is bandpassed from say 100hz to 5000hz with a 20mS delay?



If you can use PLII or L7, they will extract from the stereo signal the proper L-R component and send it to the rear outputs. I am not a huge fan of either of these processes, but it is all that's available now. MHO


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