# What DSPs currently process a center channel correctly?



## James Cole (Dec 6, 2016)

Hello Guys,

Looking to add to my F150 build proper processing for the center channel which means that the center should play the info that is belng sent to L and R and ignore the info that is being sent "stereo"

What DSPs currently do a good job?

I was looking at the Alpine H800 but am not sure it works like that...

Thanks!


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## billj214 (Dec 12, 2016)

Im looking to do the same thing.

Helix DSP Pro has multiple options for center channels.


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## Bnlcmbcar (Aug 23, 2016)

I have Helix DSP Pro. It has labels in matrix menu but it itself does not process or steer a true center signal like the H800 does with Dolby Prologic 2. Helix will pass through an already steered center channel via its inputs or allow you to create a mono sum center from stereo R+L. 

But I am wondering if ErinH's rear fill discovery for the Helix can be adapted or modified to extract a center signal from stereo input using the Helix IO matrix options?

Something along the lines of subtracting the L-R signal from the mono sum R+L signal. If my logic is right this would leave a signal with only center information behind?


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## rton20s (Feb 14, 2011)

There are a few processors that allow you to do your own matrix upmixing similar to what bnlcmbcar mentioned. The new Mosconi (Aerospace) processors are capable of this. What you are lacking in these processors compared to units like the H800 and MS-8 are the active steering that are built into the licensed upmixers like Pro Logic II and Logic 7. How critical the difference is between the licensed upmixers and the DIY approach in a car is debatable.


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## James Cole (Dec 6, 2016)

So will the Mosconi aerospace make a true center channel?

I wonder how a Dolby PLII upmixing will sound...


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## Bnlcmbcar (Aug 23, 2016)

James Cole said:


> So will the Mosconi aerospace make a true center channel?
> 
> I wonder how a Dolby PLII upmixing will sound...


No not a true center unless you feed it an already processed/steered center into one of the DSP inputs. H800 with Dolby Prologic 2 and MS8 with Logic 7 will actively steer a proper center channel from R and L stereo input.

My car has oem dts processing that does this as well. I pass that already steered signal through my Helix for center channel.

To overcome the lack of options out there for center channel steering, I have been contemplating using a home A/V processor like the Outlaw Audio 975 (stashed in glove compartment) and connecting those outputs to the inputs of a DSP like my Helix or any multi channel DSP.


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## rton20s (Feb 14, 2011)

For anyone wanting to attempt this with a processor that has capable Matrix mixing (Mosconi Aerospace, Helix, etc.), I would suggest taking a look at some of PB's posts on the Dolby PLII and Penteo Surround matrices. 

http://www.diymobileaudio.com/forum/4307362-post73.html

http://www.diymobileaudio.com/forum/4307362-post73.html

Keep in mind, you are going to need one very capable center channel. Slapping half of a $50 4" coax set in your dash probably isn't going to get there.


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## Bnlcmbcar (Aug 23, 2016)

Thanks for that info!

ErinH debunked my logic of subtracting Rear fill signal from mono summed R+L signal.

ErinH about broke it down for me:

If you use L-R and R-L to extract center from combined L+R you wind up with L+R again.

(L+R) - [(L-R)+(R-L)] = L+R - L + R - R + L = L+R


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## rton20s (Feb 14, 2011)

Bnlcmbcar said:


> Thanks for that info!
> 
> ErinH debunked my logic of subtracting Rear fill signal from mono summed R+L signal.
> 
> ...


Is there a need to subtract the rear fill (hard left or hard right) from the center? Based on the information PB provided, both the Dolby PLII and Penteo Music Mode simply use 0.7071 R + 0.7071 L for center. Left and Right are left alone and the rear surround is the only place where it might get a little tricky.


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## Bnlcmbcar (Aug 23, 2016)

rton20s said:


> Is there a need to subtract the rear fill (hard left or hard right) from the center? Based on the information PB provided, both the Dolby PLII and Penteo Music Mode simply use 0.7071 R + 0.7071 L for center. Left and Right are left alone and the rear surround is the only place where it might get a little tricky.


Your correct.

I was just thinking that maybe subtracting the hard left and hard right from a summed R+L would leave you with a hard middle? :idea2: 

Much simpler (and smarter) to use Dolby and Penteo method.

So far I believe rear surround can be achieved using these methods:

http://www.diymobileaudio.com/forum/technical-advanced-car-audio-discussion/307730-how-rear-fill-helix-dsp.html


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## rton20s (Feb 14, 2011)

I've seen the thread. The same thing is possible with the Mosconi Aerospace software. Just put a "-" in front of the percentage and you invert it. Custom matrix mixing to your heart's content.


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## dawaro (Jul 22, 2015)

MiniDSP has a center/rear fill plug-in that does a L+R center and a L-R rear.


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## benny z (Mar 17, 2008)

"correctly processing a center channel" from a 2ch audio source is a misnomer.


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## rton20s (Feb 14, 2011)

Ben is correct. The "correct" terminology would be upmixing. What we are wanting to do is upmix stereo content in real time to 3.1, 5.1, etc. making use of a center channel and/or rear speakers.


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## benny z (Mar 17, 2008)

...and even up-mixed, it just sounds...artificial. There are always artifacts left over that just make things a bit unconvincing. At least, in my experience (home and car). Things in the spacial realm just aren't as correct as a proper 2ch system imho.

Sorry, I know that isn't the "in" thing to say these days.


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## benny z (Mar 17, 2008)

Actually, I have to admit there's one car that fooled me - Natan B's car at 2015 finals. But then that was his own custom processing wizardry.


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## rton20s (Feb 14, 2011)

Ben, I assume you are talking exclusively about center channel upmixing, an not necessarily rear fill upmixing?


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## benny z (Mar 17, 2008)

Correct.


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## ohiodish (Jul 6, 2010)

This is several months old but I am looking into the same thing for my Raptor. Was considering the new Focal DSP because it has center channel and also want to try the Toslink input. Using a PAC Pro with the optical option out. I downloaded the Focal software and I like the set up and design of the DSP software but I have never used one or even seen a review of it on Youtube. I plan on redoing the entire center and add a 6.5 and tweeter. I did a similar set up in my Tundra years ago and beside hating the MS8 I used, the center did come out nice. For some reason the MS-8 was terrible active and fine with passive. No idea why.


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## rton20s (Feb 14, 2011)

I would personally skip the Focal and go with one of the other processors previously mentioned.


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## -Kyle- (Feb 5, 2009)

Noob question incoming:

Is the goal of a center channel to raise the sound stage, add up front bass, both, neither? I bought one of those cheap MS8 refurbs on eBay, and have a spot for a 3.5in center channel in my current vehicle. To me, I would like to raise sound stage and improve vocal clarity. But whats the typical "goal"?


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## rton20s (Feb 14, 2011)

There are people far more qualified than myself who can probably provide a better response, but this is my 2 cents.



-Kyle- said:


> Noob question incoming:
> 
> Is the goal of a center channel to raise the sound stage, add up front bass, both, neither?


No. Assuming we are talking about single-seat tuning. You can get up front bass and raise the sound stage without the need for adding a center channel. Any capable DSP (including those integrated into head units) and a competent tuner can achieve what you are looking for without the use of a center channel.



-Kyle- said:


> I bought one of those cheap MS8 refurbs on eBay, and have a spot for a 3.5in center channel in my current vehicle.


The MS8 is a capable processor, and the most valuable attributes are the automated tuning process and Logic7 upmixer. A 3.5" center channel is going to struggle on the bottom end. Ideally, you want something that can play fairly low to match your left and right speakers. 



-Kyle- said:


> To me, I would like to raise sound stage and improve vocal clarity. But whats the typical "goal"?


In my opinion the typical goal of incorporating a center channel would be to provide a better listening experience for multiple listeners. Not just the person in the driver's seat. Can a talented tuner make use of a center channel for a better tune than stereo for a single seat? Possible, even likely. Is the center channel needed for a good single seat tune with good stage height and clarity? Absolutely not.


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## -Kyle- (Feb 5, 2009)

rton20s said:


> There are people far more qualified than myself who can probably provide a better response, but this is my 2 cents.
> 
> 
> 
> ...


Very informative, thanks.


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## josby (May 8, 2011)

-Kyle- said:


> Noob question incoming:
> 
> Is the goal of a center channel to raise the sound stage, add up front bass, both, neither? I bought one of those cheap MS8 refurbs on eBay, and have a spot for a 3.5in center channel in my current vehicle. To me, I would like to raise sound stage and improve vocal clarity. But whats the typical "goal"?


Though not specifically talking about the MS-8, the "father" of the MS-8 explains it well here, from the 0:59 mark to 2:33


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