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What is Wrong with Centre Channels

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#1
Hi science enthusiasts, I have a question. I have seen many people claim that centre channels designed as WWTWW have a poor FR relative to their WTW counterparts in horizontal position. I know it has something to do with off-axis response but I can't find any explanation on this. Can someone direct me to a link about the science behind this issue? Thank you.
 

PaulD

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#2
It is because of the comb filtering caused by the different paths from the drivers to your ears as you move horizontally. This causes some frequencies to add and be louder, and some other frequencies to cancel completely, because of their different wavelengths and the different path length to the listener from the drivers. So this causes lobing in the horizontal polar response. Here is a reasonable explanation: https://www.audioholics.com/loudspeaker-design/center-channel-designs-1

Here is a design that does quite well: https://www.audiosciencereview.com/...s/infinity-rc263-center-speaker-review.12442/
 
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Sancus

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#3
2-way center designs pretty much suck, whether they are WTW or WWTWW. The horizontal dispersion is a mess. Here is an example of the mess you get.

What you want is a 3-way or coaxial center. The above Infinity RC263 is a good example of a 3-way, others are the Monoprice 365C, Emotiva C1+, and Polk LSIM704C. For coaxial, an example would be the Kef R2C which would have dispersion nearly identical to the Kef R3. I am hoping Amir will measure some of the cheap 3-way centers at some point to help people out in this area, as most are >$500.
 
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Thread Starter #4
It is because of the comb filtering caused by the different paths from the drivers as you move horizontally. This causes some frequencies to add and be louder, and some to cancel completely, because of their different wavelengths and the different path length to the listener from the drivers. So this causes lobing in the horizontal polar response. Here is a reasonable explanation: https://www.audioholics.com/loudspeaker-design/center-channel-designs-1

Here is a design that does quite well: https://www.audiosciencereview.com/...s/infinity-rc263-center-speaker-review.12442/
Very informative.

2-way center designs pretty much suck, whether they are WTW or WWTWW. The horizontal dispersion is a mess. Here is an example of the mess you get.

What you want is a 3-way or coaxial center. The above Infinity RC263 is a good example of a 3-way, others are the Monoprice 365C, Emotiva C1+, and Polk LSIM704C. For coaxial, an example would be the Kef R2C which would have dispersion nearly identical to the Kef R3. I am hoping Amir will measure some of the cheap 3-way centers at some point to help people out in this area, as most are >$500.
Thanks a lot. I wish members would send Amir more center channels for review. Especially budget ones
 

mansr

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#5
2-way center designs pretty much suck, whether they are WTW or WWTWW. The horizontal dispersion is a mess. Here is an example of the mess you get.

What you want is a 3-way or coaxial center. The above Infinity RC263 is a good example of a 3-way, others are the Monoprice 365C, Emotiva C1+, and Polk LSIM704C. For coaxial, an example would be the Kef R2C which would have dispersion nearly identical to the Kef R3. I am hoping Amir will measure some of the cheap 3-way centers at some point to help people out in this area, as most are >$500.
Do you have any opinion on the SVS centre speakers? I'm looking to buy something, and the price of those is compelling. Almost everything I can get my hands on within size and budget constraints is 2-way.
 

Andysu

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#6
Do you have any opinion on the SVS centre speakers? I'm looking to buy something, and the price of those is compelling. Almost everything I can get my hands on within size and budget constraints is 2-way.
Within a budget you could get JBL cinema professional on ebay, often at fish and chips prices but takes some time and looking around, which is how I got my fish and chips JBL cinema. some of these marketed home theatre speakers is a laugh at the over the top overrated overpriced and whoever made the centre channel should be fired cos that is the worst idea for home cinema. Matched JBL cinema professional, you wouldn't even go near a cinema again once you have them in your room at fish and chips prices. ... but then again cinemas are slowly going bust so watch ebay soon as these odeon cinemas and vue, cineworld showcase go under the crews will be in stripping those cinemas out and into storage for a month or many months until they are listed on ebay, often at fish and chips prices.
 
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#7
Within a budget you could get JBL cinema professional on ebay, often at fish and chips prices but takes some time and looking around, which is how I got my fish and chips JBL cinema. some of these marketed home theatre speakers is a laugh at the over the top overrated overpriced and whoever made the centre channel should be fired cos that is the worst idea for home cinema. Matched JBL cinema professional, you wouldn't even go near a cinema again once you have them in your room at fish and chips prices. ... but then again cinemas are slowly going bust so watch ebay soon as these odeon cinemas and vue, cineworld showcase go under the crews will be in stripping those cinemas out and into storage for a month or many months until they are listed on ebay, often at fish and chips prices.
thanks, i’m hungry now
 

Andysu

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thanks, i’m hungry now
Yeah, fish and chips JBL Just Beautifully deLicious. But what JBL cinema are you looking for? The current models will be bit steep would take few more years for them to be fish and chips. The older models ain't nothing wrong with them and I use the older models that would put those overrated M&K MP300 at what £3k each, daylight robbery.
 
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#9
Does this not beg the question why have a centre channel at all? I've had a centre for 20 years, numerous types, but temporary furniture changes meant using a phantom set up for a while. And I don't miss a centre at all. I wonder if just 2 or three are watching and all are in pretty much in front of the screen, then do the pros outnumber the problems mentioned in this thread.
 

Sancus

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#10
Do you have any opinion on the SVS centre speakers? I'm looking to buy something, and the price of those is compelling. Almost everything I can get my hands on within size and budget constraints is 2-way.
SVS Prime and Ultra centers both seem to be 3-way so they'd probably be fine.

Does this not beg the question why have a centre channel at all? I've had a centre for 20 years, numerous types, but temporary furniture changes meant using a phantom set up for a while. And I don't miss a centre at all. I wonder if just 2 or three are watching and all are in pretty much in front of the screen, then do the pros outnumber the problems mentioned in this thread.
Toole talks about this in his book in section 7.1, but the stereo phantom center is significantly compromised. Comb filtering causes an audible null at ~2khz, among other things. It's too long to quote big sections, but, "A center channel avoids the timbre problem, stabilizes the soundstage for more listeners, and is less sensitive to room effects."(pg 165, Sound Reproduction)

There is no real question that a properly placed, identical to L/R center is superior to a stereo phantom center. It just is. The issue comes when you are comparing a compromised design, poorly placed center, to none. Then I agree, sometimes none may be better, at least for an individual listener.

Buy good centers and make sure you can get them <10 degrees elevation difference from the L/R and there is a clear, audible benefit.
 

hardisj

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#11
Hi science enthusiasts, I have a question. I have seen many people claim that centre channels designed as WWTWW have a poor FR relative to their WTW counterparts in horizontal position. I know it has something to do with off-axis response but I can't find any explanation on this. Can someone direct me to a link about the science behind this issue? Thank you.
I recently reviewed a center channel speaker and in the video below I talk about some of the issues with “toppled MTM” designs. You might find it helpful.

 

sfdoddsy

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#12
Optimising a centre speaker requires it to be the same as your LRs, and in the same acoustic space.

This is very hard to do.

I’ve never been able to get a centre truly matching my mains. So I use phantom.

Given I hog the sweet spot off axis issues don’t concern me.

BTW, I find the earlier argument about comb filtering at 2k unconvincing. If it were then stereo recordings would suffer from the same problem.
 

Sancus

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#13
BTW, I find the earlier argument about comb filtering at 2k unconvincing. If it were then stereo recordings would suffer from the same problem.
Of course they do. This leads to the obvious conclusion that stereo is significantly flawed inherently and you need multichannel for proper audio reproduction which is 100% true.

People who think stereo is as good as it gets have literally missed the entire plot of audio reproduction. It's a compromise, nothing more.
 
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#14
Within a budget you could get JBL cinema professional on ebay, often at fish and chips prices but takes some time and looking around, which is how I got my fish and chips JBL cinema. some of these marketed home theatre speakers is a laugh at the over the top overrated overpriced and whoever made the centre channel should be fired cos that is the worst idea for home cinema. Matched JBL cinema professional, you wouldn't even go near a cinema again once you have them in your room at fish and chips prices. ... but then again cinemas are slowly going bust so watch ebay soon as these odeon cinemas and vue, cineworld showcase go under the crews will be in stripping those cinemas out and into storage for a month or many months until they are listed on ebay, often at fish and chips prices.
Just curious what JBL models you're talking about?
 

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