Home theater center channel

Scott6840

New Member
Jan 30, 2019
2
0
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#1
I am using a Polk Audio CS10 center channel speaker in my home theater setup and, while it is rated as one of the top 10 center speakers on the market, my system sounds better without it than with it, which is not how it is supposed to work. All of the other speaker are matching Polk Audio speakers powered by a Denon AVR-S740H amp.

In order to check the speaker, I took it apart (With the blessings of Polk Audio) and hooked it up to a 20MHz dual trace oscilloscope and a frequency generator. A photo of the resulting sine wave trace (at about 8K hertz) is below. The traces were made by connecting the oscilloscope to the speaker terminals, after the crossover network. The smaller trace was taken at the 1" silk dome tweeter terminals; the larger at the 5" woofer terminals.

Trace.jpg

I am not an expert in either electronics or audio, but judging from the traces shown, it appears that the signal going to the tweeter is nearly 180° out of phase with the one feeding the woofer.

Is this the way it is supposed to be? Would this account for the poor sound from the speaker? How would I get the speakers in phase with one another?

I appreciate any help anyone is willing to provide. Thanks.
 

Kal Rubinson

Well-Known Member
May 5, 2010
1,590
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NYC/CT
www.stereophile.com
#2
I am using a Polk Audio CS10 center channel speaker in my home theater setup and, while it is rated as one of the top 10 center speakers on the market, .....
I cannot accept that statement. Perhaps it is one of the top 10 low priced centers. It is a horizontal 2-way with a 2500Hz crossover which is more than likely going to have irregular (venetian-blind) horizontal dispersion due to driver spacing. That said............................
Is this the way it is supposed to be?
Possibly. Depending on the driver spacing and the crossover slope, Polk may have decided that the phase inversion might be more successful in blending the drivers. This is not uncommon.

Would this account for the poor sound from the speaker?
Impossible to say.
How would I get the speakers in phase with one another?
You could reverse the two wires connected to the tweeter terminals and decide if you think it is better.
 
Feb 8, 2011
21,354
471
83
Vancouver Island, B.C. Canada
#5
It's not from a high-end audio mag like Stereophile.
The speaker retails for $99 ... It's the best that I could find. :)

* I would cross it @ approximately 80-90 Hz to the subwoofer.
It weights a very reasonable sixteen pounds...3/4" thick enclosure, and the two mid-bass drivers are protected/covered in the rear from electro-magnetic waves dispersing and discoloring the TV set above or nearby.
For a center channel speaker in that price range it's much better than many others.
It gets the dialog (most important) right; clear and articulate, from many comments I've read.

Just for fun ...
 
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Kal Rubinson

Well-Known Member
May 5, 2010
1,590
82
48
NYC/CT
www.stereophile.com
#6

Scott6840

New Member
Jan 30, 2019
2
0
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#8
Thanks for all of the input. I was hoping that someone would have an elegant solution ("Remount the tweeter so that the logo is upside down, or some such.") that would have solved the problem, but I guess it just isn't to be.

Everyone seems to agree that the CS10 is a good, inexpensive speaker, but it doesn't seem to get the job done, at least for me. What center speaker could I get that would be a reasonable upgrade to the CS10? Could I just replace the tweeter?

Thanks again.
 
Feb 8, 2011
21,354
471
83
Vancouver Island, B.C. Canada
#9
Yes Scott, if you don't use the grille (you should because it's an integral part of the speaker design; just look @ the protruding side edges from the front baffle), you sure can mount the tweeter so that you can read correctly the Polk Logo. That way it will look more elegant.

C'mon, leave the speaker grille in place; without it the sound will hit the edges and bounced back with distortion. So if you are interested in good sound first before an elegant look use the grille.

If you still don't like the sound just buy another speaker with a mid and tweeter in the center between the two woofs; those are better for horizontal positions center channel speakers.

You could also switch all your speakers from Polk to a higher level...within the brand or not.
Also, having a receiver with say Audyssey MultEQ XT32 auto room calibration system will help in having better coherence in your room's acoustics from all speaker's provenances.
And two subs are better than one.

* If you put another tweeter in your CS10 I doubt that you'll improve its sound, but experimenting is always fun, same with reversing the phase as Kal said yesterday. Those are your ears.

I don't know what other center channel speakers Polk have, look for a three-way one.
It's the most important speaker in a home theater system.
 
Feb 8, 2011
21,354
471
83
Vancouver Island, B.C. Canada
#11
Feb 8, 2011
21,354
471
83
Vancouver Island, B.C. Canada
#13
Check my edited above post Kal; the Emotiva 3- way center channel speaker (C1) for $249
_____

The Paradigm Center 3 v7 (Series 7) was retailing for $599; it is now 50% off @ $299
_____

* Just for fun ...

 
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