Horizontal Center Channel Speakers and Why They Should Be Avoided

[drummerboy_2002]

After thinking about for a bit I think I understand the problem a bit more. While same frequencies played in an array can cancel or reinforce (even double the magnitude) each other at certain angles, multiples of those frequencies can cancel or reinforce individual waves of its multiple. IE, a 100Hz signal could reduce or reinforce every other wave in a 200Hz signal. Thinking a bit more, this situation can happen not just on the array plane, but every plane not perpendicular to the array. That's it, I'm done. My head hurts.

[Riff Magnum]

I thought that most of the newer horizontal center channel speakers have a crossover that allows one of the woofers to operate during lower frequencies, and the other to provide the midrange. This keeps the two main woofers from ever pushing the same frequencies at the same time, thus reducing lobing and cancellation.
With my DLP's tricky vertical viewing angles i don't think i'd ever be able to mount my tv high enough to allow a vertical floorstanding center channel to sit underneath.

[Corpboy]

I think I only understood maybe 10% of what all that said.

Let me ask this: if a horizontal center speaker is so bad, why oh why do I see so many of them specifically built to be oriented horizontally? It seem so self-defeating in nature.

[tlmaclennan]

From what I can tell, most center speakers overcome the problems with option #3:

3. Placing the tweeter above the horizontal line of the midrange drivers such that an approximate 45 degree angle is formed will lessen horizontal lobing.

Though that's not to say all center speakers are designed this way. I'm just curious if it is actually recommended to go out and buy three of the same floorstanding speakers to be used as Front Left, Right, and Center speakers. I'm sure that this woouldn't be neccesary for the more high-end speaker lines, as their centers are probably designed well and matched to the fronts. But if I were to go with a low-end Polk line, say the Monitor 50s, would it be beneficial just to buy 7 of the towers to complete a 7.1 setup?

[Drew664]

Originally Posted by Corpboy

I think I only understood maybe 10% of what all that said.

Let me ask this: if a horizontal center speaker is so bad, why oh why do I see so many of them specifically built to be oriented horizontally? It seem so self-defeating in nature.

I know what you mean!

I would have to think the horizontal nature of these speakers are simply due to the placement - directly under your viewing source. A "vertically challenged" speaker works best for most viewing set ups.

Also, Big Daddy - great info. I had no idea. How audible is the difference though?

[drummerboy_2002]

Ok, thought some more (ouch). While a verticle speaker with well defined crossovers (all different ranges) would produce the fewest issues, it might drop the imaging too far below the screen. I think for most of use, an MTM center with a 2.5 way crossover will do it for most of us.

Edit: Forget the crap earlier about frequency multiples. The speakers only play one frequency at any given time, so only the tweet, or mids would be playing, not both. Yep, I still think the 2.5 way is the sensible way to go.

[statikcat]

Nice post but.. I don't think most people have room below the TV for a verticle center.. due to the TV stand, etc. What are we supposed to do?

[aramis109]

Originally Posted by statikcat

Nice post but.. I don't think most people have room below the TV for a verticle center.. due to the TV stand, etc. What are we supposed to do?

1. Put your horizontal center at approximately ear level while seated.
2. Point towards center.
3. Sit in sweet spot.
4. Enjoy movie.

While I have noticed some loss in off-axis previous to this post, its just not enough of an issue (I rarely sit there) for me to make a change. My family has never complained about it. I'm the only freak about audio in the house.

[prerich]

Originally Posted by Drew664

I know what you mean!

I would have to think the horizontal nature of these speakers are simply due to the placement - directly under your viewing source. A "vertically challenged" speaker works best for most viewing set ups.

Also, Big Daddy - great info. I had no idea. How audible is the difference though?

Very!!!! When I left horizontal center channels - I never looked back. Now my front array must be three of the same speakers. I wan't nothing less (unless it's that 200 pound B&W with some 802D's, then I would consider a horizontal - but it's not really horizontal - look at the design)

[drummerboy_2002]

Ok, I'm back to my original confusion. How would raising the tweeter out of the mid array plane help with lobing? The issue is with two drivers playing the same frequency at the same time (the mids). The only place this would happen with the tweeter is in the small range where the crossover slopes overlap. Otherwise only the tweeter or mids are playing, not both.

[Clark Kent]

Another great reference post, Big Daddy.

[Big Daddy]

Originally Posted by drummerboy_2002

Ok, I'm back to my original confusion. How would raising the tweeter out of the mid array plane help with lobing? The issue is with two drivers playing the same frequency at the same time (the mids). The only place this would happen with the tweeter is in the small range where the crossover slopes overlap. Otherwise only the tweeter or mids are playing, not both.

Low frequency and high frequency sound waves have different radiation pattern. As a result low frequency drivers (midrange woofers) and high frequency drivers (tweeters) have intrinsically different radiation patterns. At the crossover point, the directivity of the drivers changes. Interference between the drivers at this point causes a dip in the level around the crossover frequency, with a peak above it. This will result in muddiness of the sound and movement of sound stage.

In reality, we have interference between three or more drivers, particularly at the crossover frequencies. Moreover, there is a significant interation between horizontal center speakers with the floor and the ceiling.

Remember that lower frequency sound waves have very long wavelengths and are omnidirectional and are not affected as much. The higher frequency sound waves have smaller wavelengths and tend to be more uni-directional with a much smaller soundfield. Interference in the upper mid-range frequencies up to and above the crossover frequency normally create most of the problems and damage sound clarity and imaging.

A vertical arrangement of the tweeter and midrange drivers will help imaging, clarity of the sound, and will increase vertical and horizontal dispersion. In addition, a lower crossover frequency point and a higher order crossovers network will help.

[Jhayman]

How about Paradigm's CC-690 its a very large center..

Originally Posted by prerich

Very!!!! When I left horizontal center channels - I never looked back. Now my front array must be three of the same speakers. I wan't nothing less (unless it's that 200 pound B&W with some 802D's, then I would consider a horizontal - but it's not really horizontal - look at the design)

[Big Daddy]

Originally Posted by Jhayman

How about Paradigm's CC-690 its a very large center..

The Paradigm CC-690 is a great center speaker. However, you are emphasizing the wrong thing. The performance of an horizontal center speaker does not depend on the size of the speaker. It is all about the arrangement of the drivers and the crossover to make the horizontal center speaker perform as well as a vertical center speaker.

[jomari]

Originally Posted by drummerboy_2002

After thinking about for a bit I think I understand the problem a bit more. While same frequencies played in an array can cancel or reinforce (even double the magnitude) each other at certain angles, multiples of those frequencies can cancel or reinforce individual waves of its multiple. IE, a 100Hz signal could reduce or reinforce every other wave in a 200Hz signal. Thinking a bit more, this situation can happen not just on the array plane, but every plane not perpendicular to the array. That's it, I'm done. My head hurts.

as mentioned in the post, its more evident in the horizontal plane and less on a vertical one. cancellation normally occurred when you have both midranges operating at the same frequency, giving you a higher chance of cancellation instead of reinforcement of the said frequency.

Originally Posted by Riff Magnum

I thought that most of the newer horizontal center channel speakers have a crossover that allows one of the woofers to operate during lower frequencies, and the other to provide the midrange. This keeps the two main woofers from ever pushing the same frequencies at the same time, thus reducing lobing and cancellation.
With my DLP's tricky vertical viewing angles i don't think i'd ever be able to mount my tv high enough to allow a vertical floorstanding center channel to sit underneath.

with the newer horizontal center channels, most companies have 'addressed' this concern, and have developed means to avoid lobing issues found in center channels. are they accurate to a certain aspect? sure. but physics is physics - we have to learn to distinguish which is truly done to dissipate the said lobing issue. some companies have addressed it in a way where we have one of the midranges to work certain frequencies, while the other would do the opposite, avoiding them to use both and cancel each other out.

Originally Posted by Corpboy

I think I only understood maybe 10% of what all that said.

Let me ask this: if a horizontal center speaker is so bad, why oh why do I see so many of them specifically built to be oriented horizontally? It seem so self-defeating in nature.

most of the center channel speakers were built back in the 90s in a more 'commercial aspect' instead of the technical course we are used to. they marketed these speakers to address a slowly growing trend back then, and have it in a convenient layout that can be placed both above or below the television/display unit. i wouldnt quickly call it self defeating in nature. there are only a few out there that would admit to purchase a vertical center vs a horizontally speaker. in essence ita aesthetics vs function.

[prerich]

Originally Posted by Corpboy

I think I only understood maybe 10% of what all that said.

Let me ask this: if a horizontal center speaker is so bad, why oh why do I see so many of them specifically built to be oriented horizontally? It seem so self-defeating in nature.

One reason - looks - its pleasing to the eye. How many people would put another tower in the center of their room? (I did ) but that's not the norm.

[cme4brain]

Originally Posted by Corpboy

I think I only understood maybe 10% of what all that said.

Let me ask this: if a horizontal center speaker is so bad, why oh why do I see so many of them specifically built to be oriented horizontally? It seem so self-defeating in nature.

I'll tell you why. Because all that tech above is meaningless for everyday, non-anechoic chambered listening areas. Center channel speakers are meant to go under a screen and therefore have to be horizontal. The concerns of lobbing are theoretical but do not really apply to the real home listening environment with a room filled with furniture, exterior sound, wall coverings and windows! While technically true that your car's tires should be at the maximal inflation pressure for the best mileage, can you drive the car 2 psi lower and not really note the difference? Of course you can. Buy the center you want (including the Axiom VP180 center which is 39 inches wide with widely separated drivers.

[chriscmore]

Originally Posted by cme4brain

I'll tell you why. Because all that tech above is meaningless for everyday, non-anechoic [SIC] chambered listening areas. Center channel speakers are meant to go under a screen and therefore have to be horizontal. The concerns of lobbing [SIC] are theoretical but do not really apply to the real home listening environment with a room filled with furniture, exterior sound, wall coverings and windows! While technically true that your car's tires should be at the maximal inflation pressure for the best mileage, can you drive the car 2 psi lower and not really note the difference? Of course you can. Buy the center you want (including the Axiom VP180 center which is 39 inches wide with widely separated drivers.

If you'd bother to have read the article you'd realize that physics are not theoretical, and center channels do not need to be horizontal. If you're willing to make compromises - good for you - but you don't have any argumentative basis to state that lobing, poor off-axis response and unintelligibility are theoretical. Again, if they are to you - great because you can save a lot of money in this hobby by having low standards.

Only one driver is necessary for any speaker, and if it's capable enough, say 60Hz to 20kHz with 115dB capability, none of the loudspeakers would need to be any more horizontal than your L/R are vertical. But the fact is that most companies aren't interested in such expensive drivers and would instead prefer to use many, lower-end drivers. Especially when it visually excites those that are primarily interested in bauble.

Several great point-source speakers are available from Thiel, KEF, and Zu Audio. For those that need to spread the duties across more than one driver, many good speakers keep their tweeters above the mid driver, although if the mid is capable enough, you could simply stop there and use a bookshelf speaker. Having horizontal woofers is a compromise (only one is usually needed, but people don't like asymmetry), but the lobing is low enough frequency to be less audible, and the maximum distance between the woofers is easier to achieve with lower frequencies. It still, however, contributes to mud-bass problems in the industry.

The Axiom vp180 is a terrible design and is used as an example of how not to design a center channel. It's appeal is that it flashes lots of trinky drivers in an array for those that have more budget than understanding of acoustics. Three vertical vp180s as L/C/R, or three M80 behind an AT screen can sound quite nice.

But your declaring that to you it's all the same and doesn't matter doesn't serve any useful purpose to those who seek to learn best practice and which elements they can incorporate into their own hobby.

Cheers,
Chris Seymour

[antennahead]

^ Great post!

[rpatt]

I'm very happy with my horizontal center. It's a compromise that works very well for me.