Same center channel speaker as L/R or different?

[Tahoe Gator]

Which would be better as a center channel, the same exact speaker or specified center channel? I have Polk RT55 left and right speakers. I could pick up an identical one on eBay so I'd have 3 of the same across or get a new Polk center channel. Any thoughts?

[superpanavision70mm]

This is such a debatable topic....and good question. I think that like most H/T you are going to find different opionions on the matter and it will essentially boil down to preference. The argument for going with a center channel that is different is that those that use floorstanding speakers are not going to find a perfect center channel match. Also, most center channels are carrying different material than what the L/R would. Center certainly carries the most amount of dialogue and is a very underrated speaker in any system. My preference is to go with a very clean and clear center speaker, which is why I went with Athena, despite listening to many other more expensive alternatives, which did sound great...the Athena delivered the type of clear sound that I wanted. The Athena is also a perfect match for my PSB towers, which are covering lots of low and mid sound, so the Athena breaks through the mix quite nicely.

I suppose going with 3 front speakers of equal identity is going to give you an equal front soundfield, but once again each are carrying slight differences and you could possibly EQ and modify each channel through your receiver. I am not a fan of this method though.

[musicman1999]

Tahoe

No,bad advice.The absolute best arrangment is to have three identical speakers across the front,but for most thats not practical.If you are happy with your Polks,select the center from that line and go with it.It will give you the best results,you do not want a speaker that breaks through the mix,you want a seamless soundfield across the front,so that left to right pans will sound the same across the front.The only way to do this is with timbre matched speakers and to do this,you cannot use a different manufacturer.Check out the dts and dolby digital websites they explain it well.

bill

[kexodusc]

Truth is...the immediate environment in the first few feet around a speaker, distance from the listener, and relative room position will do as much or more to change the apparent "timbre" of the speaker than driver material and drivers themselves. Timbre matching is a great ideal to strive for...but to say you have to buy the manufacturers "matching" center channel is misleading.

Most Center channels I've seen use the MTM (midwoofer, tweeter, midwoofer) alignment. Reason for this is straightforward. Increased dynamics, sensitivity, and decreased distortion in the midrange- where dialogue is. This is good. The downside, however, is that the MTM design by nature is not a good performer when placed horizontally. The crossover slope, frequency, off-axis response, dispersion, and power response are all dramatically different than the L/R speakers this center channel is suppose to match. All of these contribute to the "timbre" of a speaker. How can anyone say an MTM placed horizontally "timbre matches" a 2-way floorstanding speaker with a single tweeter and woofer? They don't. Instead, you get a few similarities at a few region in the spectrum where the speakers behave similarly - in anechoic conditions. Put them in a room, on top of a TV, etc, and all bets are off.

So the manufacturers use voicing techniques to attack the center channel's slope such that it "sounds" like the L/R speakers.
Fact is, these broad similarities are usually convincing enough. That's why you'll often see manufacturers sell center channel speakers that have different drivers than the L/R speakers they're matched to.

Since different drivers can also be "timbre matched", we have to accept that different speaker brands can be timbre matched. You'll find that center channels with similar driver material and similar crossover regions/slopes will work quite well with your L/R mains. It might even sound better than the "recommended" center channel. The reason why we don't always recommend mixing brands is because it's just much easier to buy a speaker from the same company when you know it's at least close in "timbre". If your mains are polypropylene/titanium, you should start looking at other poly/titanium combos, but expect some trial and error...this could get quite costly and time consuming as you'd imagine. Obviously a company builds a center channel with matching it's own products in mind...

This is about the best we can get for people who want a speaker to go above or below their TV. But to call it "timbre matched" is more marketing than substance. The only "timbre matched" speaker to any speaker is itself.

The choice of using a dedicated center channel model, or a 3rd L/R speaker for a center channel should consider the following:
Will it be used for movies more than music (multi-channel audio).
For movies, the lower distortion and slightly better dynamics lean towards a center channel - for music, the best imaging/soundtage will come from a 3rd speaker.

Will people sit off axis of the center channel's tweeter more than a few degrees? (1 or 2 feet to left or right - 2/3 width of a typical sofa). Those MTM speakers suffer terrible changes in frequency response, and therefore timbre, as you move off axis even a few inches...much more so than single woofer speakers or even TMM's. Let's be honest though, most of us probably sit in the "sweet spot" or darn close to it - so it's good enough.

But if you've got a larger room, and your family sits, 2 feet or more from the horizontal center (assuming 10 ft proximity or less to TV) very few MTM center channels will be anything close to timbre matched. A 3rd L/R or even similar speaker from the company's product family would be preferable. Maybe even a competing brand.

What height relative the L/R will your center speaker be placed at? MTM's actually have fairly decent dispersion making them less sensitive to variations in vertical placement...especially when matched to L/R speakers. Though angling can mitigate some of the difficulties a 3rd L/R might be faced with.

I think most people would be better off with a bookshelf version of their L/R speakers (especially if they already are bookshelfs) in a system used for music and movies. So why don't companies offer this? I really don't know...Money is the only thing I can see. When the center channel is the best speaker in a 5.1 system, the others have been compromised or the consumers choices have been intentionally limited to boost revenue. Check out the prices of most center channels...I see them anywhere from 2/3 to 3/4 the price of a pair of speakers...yikes.

[L.J.]

Dang Kex, that's one helluva comment! Great info!!


I did a demo for a friend a couple of months ago and let him sit in the SS. This was my first time out of it and I could not believe the diff in sound. It was just awful. And I was only in the next seat over on the couch.

[kexodusc]

Dang Kex, that's one helluva comment! Great info!!


I did a demo for a friend a couple of months ago and let him sit in the SS. This was my first time out of it and I could not believe the diff in sound. It was just awful. And I was only in the next seat over on the couch.

Maybe 5-7 years ago you saw alot more LCR speakers that were usually MTM's made for left/right/center/surround purposes. All one model. Problem with that is most people stick the LCR speaker on a TV (or near it), so the baffle step compensation circuitry which was the same in all 3 speakers was working against itself to "mismatch" the center from the other 2 speakers. You either had too much or not enough attenuation in the 200-1000Hz range. It's no wonder these aren't more common today. Give speaker companies credit, it's hard designing a "one-size-fits-all" speaker. They can only make assumptions about the "typical buyer" in any price-range and go from there.

I think part of the traditional center channel speaker's success can be attributed to looks. Let's face it, the symmetrical looks of most center channel speakers looks better than a tall skinny bookshelf standing on top of a tv or laying horizontally with a tweeter and woofer ruining the symmetry.

[AVMASTER]

Kex;
your opinion on matching the width of the center channel to the screen( as close as possilbe)?????
thanks in advance

[musicman1999]

My main point was that for the average person,the easy way to get good sound is to buy the speaker that matches it as close as possible,for the average guy.I do recognize that other solutions work as well,but need a little more though and work.

bill

[kexodusc]

Kex;
your opinion on matching the width of the center channel to the screen( as close as possilbe)?????
thanks in advance

That's a new one to me...The width of the speaker affects the center point frequency of the baffle step loss (rise) phenomenon normally, but in the case of a horizontal lying center channel, width isn't terribly important. The only possible dowside to the speaker being less wide than the screen would be a bit of diffraction effects. You won't notice much, if at all.

We're more concerned with the speaker's placement relative to the TV set. When top mounted, the screen is effectively extending the size of the front baffle, making the speaker "appear" to be much taller than it is. This will reinforce lower frequencies (well, prevent the the loss of inensity of lower frequencies) as they "bounce" of the front screen. I think most center channels these days make the assumption that the speaker will be mounted on a TV set, just below and in front the TV set, or close to a front wall where it will benefit from this reinforcement.

It's always a good idea to demo the center channel in a position similar to where you'd put it.

Don't downplay the significance of this. Baffle step compensation is critical to getting the speaker to sound balanced, and is often a trial and error process in a lot of designs. For L/R speakers, we assume there will be no walls immediately beside or behind the speaker, so we build in this compensation to correct for the loss of some response below 1000 Hz or so. For a center channel, once this assumption is made, and correction is built into the crossover, the speakers response is locked. Optimal performance should depend on what assumption the designer made. If the designer assumes a large 57" TV will be right below the speaker, less compensation is used...if it's assumed to be stand mounted a foot or so in front of the set, more compensation is used. If you put your speaker somewhere other than the assumed place, the response will change of course. Whether or not you notice the difference as good or bad is another question.

I'm guessing most designers assume on top of a TV, close to the front wall.

I made a home theater system consisting of 5 identical speakers. For the center channel, I had to substitute in a smaller resistor than the front mains in the crossover twice before it sounded right, and matched to the L/R speakers. The speaker sounded to bloated for lack of a better word...not enough treble - too much lower midrange.
For the wall mounted surrounds, a smaller resistor still (and a different inductor). 5 Identical speakers, 3 different crossovers, all dependant on their placement.

I was stupid, too, didn't label the speakers, so when time came to move, I had to take them apart to find out which one belonged where :shocked:

[kexodusc]

My main point was that for the average person,the easy way to get good sound is to buy the speaker that matches it as close as possible,for the average guy.I do recognize that other solutions work as well,but need a little more though and work.

bill

I think this is generally good advice...for most people, the matching center channel is probably enough and is definitely the easiest solution (short of no center channel at all).

I think a large portion of the people that post here are a bit more than the average speaker buyer, and perhaps more fussy about their systems.
If someone is even considering what options they have besides the recommended center channel they should still add that center channel to the list of options, but don't rule out anything else just because the manufacturer says something is a perfect match.

2 years ago I would never have considered a 3rd L/R speaker for a center channel, it just wasn't possible. In my next setup, it'll be the best option for me. Things change...

One last comment...we should also consider the importance of placing your front 3 speakers at the same height. A friend of mine just put his speakers on 12" taller stands, but upside down so the tweeter was still about ear level...he claims far better results with a more seamless transition from Left to center to right etc..

I haven't tried yet, but it makes sense.

[Woochifer]

As others have said, three identical speakers across the front, all aligned at the same level, is the way to go, IF you setup allows for that. The typical horizontal center speaker was developed solely because the ideal place for a middle speaker is exactly where most people have their TVs. Otherwise, there is no technical advantage to the horizontal center speaker alignment and basically it's a compromise by necessity.

Most center speakers are designed to sit on top of a TV, and aside from some flat panel and coaxial designs, the basic design has not changed much since these speakers were first introduced when Dolby Pro Logic came along. This design made sense when nearly all TVs were housed in large deep cabinets with CRTs.

With CRT-based TVs, there's really no place for three identical speakers up front, unless you lay the middle speaker on its side or stand it up high, neither of which are ideal alignments. There's also the issue of magnetic interference to consider, since most main speakers are not magnetically shielded.

However, more recently, numerous changes to the TV market have made three identical speakers up front more feasible. First and foremost, more and more TVs sold nowadays can mount on the wall, which opens up the space underneath the TV for the middle speaker. Also, more TVs nowadays use DLP, D-ILA, plasma, or LCD, which are not susceptible to magnetic interference like CRTs. Another factor to consider is that TV cabinets are no longer built as deep as before, so a good portion of the rear projection or flat panel TVs nowadays are not deep enough to support a center speaker sitting on top. In addition, bookshelf speakers have increasingly been sold individually rather than as pairs.

I think that with more and more rear projection and wall-mounted TVs getting sold, the previous assumptions about center speakers need to at least be rethought. If you can't feasibly go with three identical speakers at the same level up front, then you need to go with the center speaker that provides the best voice match with the mains. It does not matter how subjectively good a center speaker sounds if it does not sufficiently match with the mains. A horizontal center speaker, side mounted bookshelf speaker, or high mounted bookshelf speaker will each create their own issues with the front soundfield continuity. It's up to you to decide which approach works best in terms of performance and compatibility with your room and existing setup.

[Woochifer]

I think most people would be better off with a bookshelf version of their L/R speakers (especially if they already are bookshelfs) in a system used for music and movies. So why don't companies offer this? I really don't know...Money is the only thing I can see. When the center channel is the best speaker in a 5.1 system, the others have been compromised or the consumers choices have been intentionally limited to boost revenue. Check out the prices of most center channels...I see them anywhere from 2/3 to 3/4 the price of a pair of speakers...yikes.
...
I think part of the traditional center channel speaker's success can be attributed to looks. Let's face it, the symmetrical looks of most center channel speakers looks better than a tall skinny bookshelf standing on top of a tv or laying horizontally with a tweeter and woofer ruining the symmetry.

I think a big part of the horizontal center speaker's appeal has simply been its practicality for typical room setups. For CRT-based TVs and RPTVs, the horizontal center speaker just sits on top of the TV and doesn't get easily knocked over. For people with entertainment units or TV stands, the center speaker can easily fit inside. As I said earlier, I think the large-cabinet TV designs that led to the need for a horizontal speaker in the first place are on their way out, and this will hopefully lead to some rethinking on how to address the center channel. I like the approach of using a third bookshelf speaker, but I'm not not so sure about laying it on its side.

Interesting point about the pricing. It seems that premiums are often charged on surround speakers as well, particularly dipolar or bipolar designs. Might just come down to more drivers = more $$$.

[kexodusc]

. As I said earlier, I think the large-cabinet TV designs that led to the need for a horizontal speaker in the first place are on their way out, and this will hopefully lead to some rethinking on how to address the center channel. I like the approach of using a third bookshelf speaker, but I'm not not so sure about laying it on its side.

There's still some problems with this approach, baffle step rise in particular. The dispersion characteristics are actually a bit better than an MTM for a horizontal bookshelf, I just ran a few simple simulations though, and I typically see a +1 to +2 rise in the overall response from 1000Hz and below....I suppose one could use their receivers EQ features, but that's getting even more complicated.

Pick your poison I guess. Easy to see why a recommended center channel is the easiest solution.



Interesting point about the pricing. It seems that premiums are often charged on surround speakers as well, particularly dipolar or bipolar designs. Might just come down to more drivers = more $$$.

Well, yes, intuitively this makes some sense. There's probably some extra costs in producing only a single speaker for ever pair as well, smaller production runs, design/R&D costs, etc. Most people probably don't bother considering the cost of a single driver and a few bucks for crossover components, speakers seem to base price more on looks and relative performance. That's true in any market though.

I could cry foul at the pricing of a CC-370 compared to a Monitor 5 speaker, but that's not nearly as foul as the gap between the Monitor 5 and Monitor 7, IMO.

Subs are the worst value wise from what I've seen.

I can only assume the solid profitability of speaker companies is at least partially responsible for the incredible number of start-up companies the past few years. I keep waiting for competition to force some big company prices down...doesn't seem to be happening though, yet.

[Kevio]

Most Center channels I've seen use the MTM (midwoofer, tweeter, midwoofer) alignment. Reason for this is straightforward. Increased dynamics, sensitivity, and decreased distortion in the midrange- where dialogue is. This is good. The downside, however, is that the MTM design by nature is not a good performer when placed horizontally. The crossover slope, frequency, off-axis response, dispersion, and power response are all dramatically different than the L/R speakers this center channel is suppose to match. All of these contribute to the "timbre" of a speaker. How can anyone say an MTM placed horizontally "timbre matches" a 2-way floorstanding speaker with a single tweeter and woofer? They don't. Instead, you get a few similarities at a few region in the spectrum where the speakers behave similarly - in anechoic conditions. Put them in a room, on top of a TV, etc, and all bets are off.

I'll take this excellent and historical post a step further: the horizontally mounted MTM is a flawed speaker configuration. The side-by-side identical drivers are produce phase cancellation and a spacial comb filter. Timbre is going to vary greatly, critically sensitive to the angle from center. Off axis it is as messed up in your living room and it is messed up in an anechoic chamber.

Why would anyone build a speaker like this? I suspect it is because a single driver won't do the job in the limited space where it needs to live (above or below the TV) and because the symmetry "looks right". An asymmetrical driver configuration is not going to "look right" for a center channel speaker.

If anyone knows of a legitimate justification for this configuration, let's hear it. Meanwhile I've replaced my MTM with a standard bookshelf speaker and I and those sitting to the left and right of me on the couch are much happier.

[RoadRunner6]

If anyone knows of a legitimate justification for this configuration, let's hear it. Meanwhile I've replaced my MTM with a standard bookshelf speaker and I and those sitting to the left and right of me on the couch are much happier.

This is a very old thread but IMO there is misinformation in some of the above posts.

The justification is one of practicality and marketing. The Absolute Best arangement is to have the exact same speaker in the exact same orientation (vertical) for all three speakers across the front. This, especially with larger speakers, is almost never practical and hence the development of the horizontal center channel in a D'Appolito array. Most peolpe don't realize this is only done for practical reasons and is not the best for sound. It is in fact practical for smaller systems if you can buy single speakers, rather than in pairs only, so you can buy three identical speakers (Axiom sells their bookshelf speakers individually). My current system (as well as my previous two systems) have three identical bookshelf speakers, at the same height and slightly tilted down to ear level, all in a vertical orientation across the front. Yes, each speaker has a slightly different voice due to near room effects but it is definitely as close as you can get to having the perfect timbre matching across the front.

IMO, this is one of the several very important reasons I have excellent sound in my room even with very modest costing speakers.

Here is a very interesting and relevant quote from a review in Home Theater Magazine on the new Energy Take Classic 5.1 system:

"..........The Take Classic satellite is a two-way design with two drivers. So, surprisingly enough, is the Take Classic center. It eschews the woofer-tweeter-woofer array so common in center speakers in favor of a single woofer and tweeter. The only differences between the satellite and center are that the latter’s enclosure is a little longer, presumably for horizontal placement, and it has two front ports instead of a single back port.

People, the absence of a second woofer is front-page news. It means that this center is more graceful in handling a problem that plagues the vast majority of other dedicated center speakers to some degree. The problem is lobing. While this phenomenon affects all speakers with physically separate drive units, it occurs profoundly in the dispersion patterns of speakers utilizing dual midwoofers operating over the same frequency range. When listened to off axis, they sum and cancel each other differently at various angles. In the case of most horizontal center speakers, the listener in the center seat may enjoy flat frequency response, but the listeners off to the sides won’t. The Take Classic designers deserve credit for doing the right thing where so many others bow to bad habits and marketing inertia.........."

RR6