# Center bookshelf speaker - why different size?



## oddeomixer (May 12, 2010)

In the home theater, often the center speaker is a different size. Why? 

I understand that space (tower, etc.) often the issue. 

It seems counter intuitive when the center speaker has different size drivers, more drivers, and different size enclosure than the main left & right speakers. 

Often, I read that the center channel speaker has been designed to match the “timbre” of the left and right speakers. How is that possible? Seems to defy the laws of physics.

Someone please explain this center speaker philosophy. 

The Left, Center, Right speakers in the movie theater are the same. The dub stages where movies are mixed have speakers the same size for the Left, Center, Right.

For example;
I’m looking at the Polk RTiA3 speakers for the LCR.
Polk only sells the RTiA3 in pairs.
On Polk’s web site, they often recommend a “center” speaker like the CSiA4. Saying that the “timbre” matches the RTiA3.

Any insight on the physics/science or calibration voodoo - would be appreciated.

-Scott


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## lcaillo (May 2, 2006)

The center channel is mono and contains all of the energy that would be in L & R channels in a stereo system. In most soundtracks there is much more energy in the center channel than in the L & R, particularly if no sub is used.


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## Kal Rubinson (Aug 3, 2006)

Most center speakers are designed to fit under the screen and are accompanied by a lot of jabber about matching/voicing/timbre. In fact, they are severely compromised speakers that suffer in comparison to the main speaker to which they are supposedly matched. How many modern quality loudspeakers have you seen that have horizontally-arrayed drivers? I cannot think of any and that should tell you that the OP's initial concerns are valid.


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## tcarcio (Jun 27, 2007)

In a perfect world you would want your front 3 to be the same but in most cases it isn't possible because of the inability to have the room in the setup to put a large speaker such as a tower speaker in front of your screen. I have all matching fronts but I have the room to do it with the speakers I have chosen. People with transparent screens that allow sound through usually will have 3 matching speakers because they can obviously put them behind the screen so they are not seen. Here is a pic of my center which have the same waveguide as my L+R.


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## zuter (Dec 14, 2012)

There is plenty of voodoo and science on this topic. And yes you are right there are differences in sound with orientation/layout of speakers and drivers. Depending on your budget there may be no limit to what can be achieved, but for most setups some compromise is required.

I use the Axiom M80 towers and VP180 center. The center is the towers, drivers and cabinet, on their side with a little modification for its horizontal layout. This is the closest I can come to matching my 3 fronts in a typical setup. Ideally I would use 3 towers but that isn't possible or affordable.


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## Kal Rubinson (Aug 3, 2006)

zuter said:


> There is plenty of voodoo and science on this topic. And yes you are right there are differences in sound with orientation/layout of speakers and drivers. Depending on your budget there may be no limit to what can be achieved, but for most setups some compromise is required.
> 
> I use the Axiom M80 towers and VP180 center. The center is the towers, drivers and cabinet, on their side with a little modification for its horizontal layout. This is the closest I can come to matching my 3 fronts in a typical setup. Ideally I would use 3 towers but that isn't possible or affordable.


Of course, compromise is necessary in the vast majority of cases. However, I respond as I do because there is a common misconception among newbies that a "dedicated" center speaker means that it was designed to perform better than its tower or stand-mounted siblings. I would hope that no one would choose such a center, based on such a misconception, when he could accommodate a "normal" speaker .


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## Wayne A. Pflughaupt (Apr 13, 2006)

oddeomixer said:


> It seems counter intuitive when the center speaker has different size drivers, more drivers, and different size enclosure than the main left & right speakers.


It’s not as counter-intuitive as it might seem. Often the various speakers in a manufacturer’s particular model line will have the same tweeter and different sizes of the same woofer (in the example of a two-way speaker like the Polks you mentioned). Believe it or not, the voicing on such speakers will be similar, if not virtually identical. 

In fact this is something I tell people all the time who have (for example) vintage floor-standing stereo speakers that they want to utilize in a surround sound system: “The model “XX” was a bookshelf version of the same speaker, with an identical tweeter and a smaller version of the 8-inch woofer your speakers had. Find a couple pairs of those and you’ll have timbre-matched surround and center-channel speakers.” Naturally there will be differences in bass extension between the main and smaller speakers, but the overall voicing will be the same. I once had such a system and the blend between the mains and surrounds was audibly seamless.

That said, the real compromise in timbre-matching will be with speakers designed and designated for the center channel, as Kal rightly noted, as they typically re-orient the drivers. So the best center channel speaker is actually one that matches the mains, including its orientation (i.e. standing upright), if at all possible. But even then, center channel timbre-matching qualities can be compromised if it’s put into a cabinet.

Regards,
Wayne


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## vjsanaiz (Oct 23, 2012)

One the most clear explanations around the timbre subject, in other words, a soft dome tweeter by A will more than likely have a different voice than a metal dome by B.
On the matter, I also think that timbre match is more critical in mutli-channel music reproduction than in movie reproduction.


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