Placement of center channel

[The Dali]

Hi everyone... I have a smallist center channel that I am going to mount on the wall either above or below the plasma TV. Are there any recommendations on the actual placement of a center channel when it is mounted on the wall?

I expect to mount the TV at the optimum viewing height, and placing the center below the TV seems too low given possible obstructions (tables, feet on an ottoman, etc)... just thought I'd check if there was some common wisdom about this... thanks!

 

[Manin]

Hi everyone... I have a smallist center channel that I am going to mount on the wall either above or below the plasma TV. Are there any recommendations on the actual placement of a center channel when it is mounted on the wall?

I expect to mount the TV at the optimum viewing height, and placing the center below the TV seems too low given possible obstructions (tables, feet on an ottoman, etc)... just thought I'd check if there was some common wisdom about this... thanks!

If you have the room, go above the TV. Where will the tweeters in your mains be in respect to the height of your TV?

 

[The Dali]

I was planning on the front speakers to be placed even with the middle of the TV and angled down slightly toward the viewer.

 

[The Dali]

Do others agree that placing the center above the TV makes the most sense?

 

[mazersteven]

Do others agree that placing the center above the TV makes the most sense?

As you stated that you will have obstructions by mounting the speaker low. Then I can see no other choice but to mount it over the television.

 

[Alex2507]

Do others agree that placing the center above the TV makes the most sense?

Funny you should ask.

I wasn't gonna do this again because last time I made a mistake and had to eat my words but this time I won't mention any names. I was going through a really smart guy's thanked posts and found one where he advised against it. Now that I think of it I remember reading where another really smart guy said that going above the TV with the center would result in being able to localize the source as from above. Maybe it's an innate ability from the Pterodactyl days.

Take a stroll through the members system galleries. I think you'll find the vast majority of centers below the display. Hey, if you don't like it, plan B can be figuring out a way to hang that puppy off the wall.

Mine is below the display. Note: Spell check rules. Teradactile.

Edit: Got it.
http://forums.audioholics.com/forums/showpost.php?p=435357&postcount=6
Maze, I think the OP is talking about the normal stuff possibly being in the way. Instead of the 'try and see' reply I think I'll go with 'try it you'll like it' for the below position.

 

[TLS Guy]

Do others agree that placing the center above the TV makes the most sense?

Yes it does. Angle it down towards the listening position. This will help reduce ceiling reflections.

The sound should then seem to come right from the screen, and people seem a normal height when speaking. Note, only the lower coaxial diver has the tweeter connected. The upper driver is an active fill driver from an active crossover. So the center of the lower driver, is the acoustic center of the center channel.

 

[jostenmeat]

Where will the tweeters in your mains be in respect to the height of your TV?

To me this very first question asked is pretty darned relevant. It hasn't been answered yet, has it . . .

Yes it does. Angle it down towards the listening position. This will help reduce ceiling reflections.

The sound should then seem to come right from the screen, and people seem a normal height when speaking. Note, only the lower coaxial diver has the tweeter connected. The upper driver is an active fill driver from an active crossover. So the center of the lower driver, is the acoustic center of the center channel.

TLS Guy, nice to see you back. A little hiatus? Q: If it turned out it would be better from under the screen, he could simply flip the center upside down to have the "acoustic center" be, well, more centered to display, yes? Of course, angled up in this case.

 

[Alex2507]

Then it's settled.
If you don't place it below the screen,
then you should definitely place it above the screen.

In order to keep this post from being useless but no less of a mini hi-jack would somebody point me to an article that talks about lobing. I read that taking a regular speaker and laying it on it's side to be used as a center was a bad idea due to lobing. What is this lobing?

 

[Audioholics]

I made a pretty picture to demonstrate some of the issues with non-ideal center channel placement relative to the mains (and vice versa):

This is part of a Primer on installing surround sound.

 

[jostenmeat]

I sort of don't even want to reply, because Im sure there are many others who would do a better job in explaining. Well, ok here's a quote from Audioholic's Vertical vs Horizontal Center Speaker Designs, and I take the liberty in bold-facing.

If anyone likes you enough to watch a movie with you, the center channel must reproduce all that content smoothly and predictably across all your seats. If you’re sitting perfectly in front of the center channel, having multiple drivers of the same type in a horizontal configuration can do the job just fine. But if you move slightly off-axis, or as any of the other seats will realize, having horizontally-aligned redundant drivers will cause some frequencies to be canceled and some to be reinforced. This phenomenon is called wave interference and you can read more about a double-slit experiment with light (or any other physical media that behaves in waves) here. The subtracting and adding of various frequencies at various angles can result in audible shifting in the speaker’s sound across the room. Not only does the off-axis frequency response suffer, but timing and phase response follow. Off-axis, MTM speakers can often sound hollow but the comb filtering, or lobing effect, can also shift the imaging away from the middle as a “phasy” sound.

Now, as for a bookshelf on its side... that's not exactly the same as redunant woofers, but OTOH, the tweeter and mid do play the same freq's at or near the x-over.... right? Just my educated guess. Then, some vertical speakers might have wave guides and/or other designs that prohibit any other orientation outside of vertical.

Anyways, lobing's nutshell description is in that quote.

 

[TLS Guy]

To me this very first question asked is pretty darned relevant. It hasn't been answered yet, has it . . .



TLS Guy, nice to see you back. A little hiatus? Q: If it turned out it would be better from under the screen, he could simply flip the center upside down to have the "acoustic center" be, well, more centered to display, yes? Of course, angled up in this case.

I got back after three weeks in England a week ago. I'm now very busy with fall work. Getting the leaves blown, winterizing boats, tractors and vehicles. I have been getting a couple of the tractors ready to move snow. This time of year is very busy in lakes country. Summer, and we had a fine two months of it, has now well and truly given way to fall.

I have to get as much done as I can before heading to Orlando next week.

 

[TLS Guy]

Then it's settled.
If you don't place it below the screen,
then you should definitely place it above the screen.

In order to keep this post from being useless but no less of a mini hi-jack would somebody point me to an article that talks about lobing. I read that taking a regular speaker and laying it on it's side to be used as a center was a bad idea due to lobing. What is this lobing?

Lobing comes about from the tweeter and mid woofers being displaced, and the phase shifts of crossovers. The usual speaker layout of tweeter above woofer will do a pretty good job in the horizontal axis as a rule. However the vertical axis is not so pretty. To simplify things in general even order filters tend the have max output on axis with cancellations off axis. Odd order filters in the usual placement have a lobing error such that the max output lobe is tilted 15 degrees downwards, or 15 degrees upwards, if the tweeter is below the woofer.

In the MTM D'Appolito configuration, the lobing pattern of the odd third order filter, is used to control vertical dispersion. That is why the common center speaker with the D'Appolito layout turned 90 degrees on its side, makes no sense whatever, and should not be done or tolerated. To make matters worse there are a lot of big name manufacturers using the D'Appolito configuration with even order crossovers! Where their designers leaned their craft, Heaven only knows.

This article might help.

 

[Alex2507]

Thanks guys.
I was able to glean a vague understanding of the subject matter after a couple of brief skims of the material. A more concentrated effort is obviously required. Having info available is a start.