Why not use mains as centers

Is there a reason I should'nt use two good bookshelfs or smaller towers for my center if I have two center outputs and available amp channel?
Sure, If you have the room. I have a big projector screen it sounds more convincing than a single. To err on the side of caution, I wired mine in parallel.
Sorry, I meant to say that I wired them in series!
I think the only reason companies make special center dchannel speakers is so that they will not take up a lot of height, and fit on top of or underneath the monitor OK. If your speaker fits under or on top of the monitor, I would say it should be better than a center channel. It seems like all the specialized cabinet design that manufacturers tout as a reason to buy their speaker goes out the window with center channel design.
Using a main speaker as a center is ideal and usually superior to using most dedicated center speakers. However, you should use only one, not two, or the radiation/interference issues common to horizontal speaker will be encumbered.

Use one. Save the other for a spare.

I use two bookshelf speakers on their sides, on top of the sub, tweeters in, and making a V angle out of about 30 degrees. Sandbox on top. No interference issues apparent in movies. I play music elsewhere.
I would expect a good specialized centre channel speaker to be far superior than a third main. The centre channel in an HT setup is primarily for voices. Voices are in the midrange. So the design of the centre speaker can focus on midrange reproduction. There is less need to design for bass. The left and right mains, on the other hand, need better bass capability. So their design will be obviously different. Specialization of function is, I think, the primary reason why centre speaker design differ from that of other speakers. Also, HT speaker design will, or may, at the manufacturer's option, have to accommodate the design requirements needed for THX certification.

You can't assume that what's desired in a speaker for music reproduction in a 2 channel system is what's needed or desired in an HT set-up. That's why a lot of people have dedicated systems for both 2-channel and HT use. That's why you see so many posts on this forum from people about how to deal with the compromises when they want to use a single system for both purposes.
Sorry, Markphd. While there are a few well-designed center speakers, the vast majority are specialized to accommodate their positioning, not their performance. In specific, horizontal speaker arrays are fundamentally flawed and that is why you see so few of them used for stereo or main channel speakers.

As I said, there are exceptions but they are few and far between.

Also, Samujohn, it is fine that you are happy with your paired horizontal speakers but that does not mean they are not compromising imaging due to radiation interference.

I helped a buddy set up a great home theater, with a lot of room, and we actually used a pair of Magnepan MMG's because he had the space and an extra pair, man they sound great. We had no interference problems, and actually just split the signal with a good DH Labs Y-splitter from the processor. It has worked great. It's a bad-a__ theater. All Maggies: IIIa up front (rebuilt at Magnepan), MC-1's for the rears, the pair of MMG's for the center and a single Velodyne DD-15 in a fairly large room. Very nice for music, great for theater. Anthem D-1 with an Innersound ESL running the fronts and a Parasound 2205 running all the other speakers, it's a really bumpin' home theater, turned out great.
Maggies are a special case. Considering their construction, using a pair, edge-to-edge with the HF drivers together, actually works well and, imho, better than any of their dedicated centers. In fact, one of the very best MCH systems I have ever heard consisted of three pairs of 20.1s with one pair as the center, edge-to-edge and sharply angled with the HF ribbons pointed at the listener.

As for others saying that they hear no interference with a pair of standard speakers side-by-side, that's fine. That there is interference can be demonstrated with measurements but the degree to which listeners hear it or are bothered by it varies greatly.

Sorry Kal, I disagree with you.

My two cents worth , a good center channel with 2 mid drivers flanking the right and left side of a tweeter mated with matching drivers in the left and right fronts will not only give a more seamless integration with timbre matching but the designs of most good center channels will pan sound across from side to side better than a speaker made to be used as either the left or right side of a pair of speakers. Center channels in home theater do more than vocals. The center channel is where 90% of a movies sound will come from no matter what type of movie. In my opinion it is the most important speaker for home theater sound. With 90% of the sound coming from the center channel why wouldn,t it be . I have to agree that a specialized design for the center is better for home theater use. I cannot agree with a statement that center channels are designed to accomodate positioning and not performance. NHT AC2 , Martin Logans ,to say that center channels like these two of many were not built with performance of sound first is hard to beleive. Sorry , my two cents actually ran up to five cents worth. Damn inflation! Cheers
thanks for the input.I was just going to put them on both sides of a 73" screen,use them for movies and play music in two channel.I have the room I was just wondering why I don't see anybody doing it.
Well, gentlemen, you can disagree with me all you want but the physics does not change. Two drivers emitting the same signals but displaced from each other by more than 1/2 wavelength will produce additive and subtractive interactions resulting in an extremely ragged spatial radiation pattern in the plane of the drivers. This means, for the typical center channel, in the horizontal plane, unfortunately.

Thus, a typical MTM arrangement is fine when vertical since its horizontal dispersion is uniform and the vertical dispersion less important as long as the listeners remain seated or in the direct beam of the speaker. A "center channel with 2 mid drivers flanking the right and left side of a tweeter" is a design that is made to accommodate design and convenience and suffers from the described uneven dispersion. Note the lack of any quality main speakers with laterally arrayed drivers.

I do not wish to single out ML, nht or any other decent company since they are almost all at fault. They want to sell speakers that people will want and, unfortunately, most people think that a wide center speaker with an array of drivers "looks" like it would have a wide dispersion.

None of what I say depends on my hearing but on physics. Speak with any design engineer or read any book on speaker engineering and the issue is clear. Whether you care about it is your own business.

two centers as mains(l and r) will work too.
Jaybo wrote: "two centers as mains(l and r) will work too."

If you stand them up vertically. ;-)


You are quite correct. Speaker arrays (same drivers outputting same frequencies) are best avoided except in the bottom two octaves (assuming one cherishes precision). You get lobes in response as well as comb filtering of certain frequencies which makes the audible response much more variable than a point source.
As I stated earlier, the issue is the relationship of the driver spacing to the wavelength. In the bottom end, the wavelengths are large enough that the relative placement of the drivers is inconsequential. I was surprised at the resistance to this issue here as I thought it was a fairly well-known matter.

All I know, is that where I have set it up, it sounded fantastic. Not sure of the physics behind it, but the 2 MMG's emitting the center works very well in a home theater I set up for someone in my neighborhood, who didn't want to give up his MMG's.
Good. As I said, and for many reasons, Maggies are a special case.

Do people really think the extra effort put into time aligning the drivers, making non-parallel cabinet faces, controlling horizontal dispersion, etc. becomes unimportant in the most important sepaker in the system? You can either think it is unimportant in all of the speakers, or important in all of the speakers, but it doesn't make sense to think it is only important in the side channels, but not in the center. In both stereo and multi-channel, you are trying to get image continuity between an array of speakers - same problems whether you have 2, 3, or 5 speakers.
Post removed 
Right, Bob, except I did that a few years back. ;-)

I recall being annoyed at the repetition of basic articles in the hobbyist mags every 2-3 years back when I was an avid reader of the audio and photography mags. Now, I realize that there are new readers coming on board all the time and they never saw the previous publications.

Still, today, everything is archived on the Internet. Unfortunately, no one new knows to search for that stuff until something becomes an issue for him.

In specific, horizontal speaker arrays are fundamentally flawed and that is why you see so few of them used for stereo or main channel speakers.

Absolutely agree. I have no ATC center channel. There is a reason and it is not budget. There is also a reason that studios use the same speaker for center channel as they do for the other channels. Also studios align the speakers vertically (midrange and tweeter must be at the same height as L and R). The whole HT horizontal home center channel thing is a compromise for off axis listeners - they benefit but overall everybody loses a bit from this configuration. Obviously the TV screen makes this comprise necessary, however, for those who rarely watch movies with a crowd their is a compromise which is better IMHO: phantom center!
>Is there a reason I should'nt use two good bookshelfs or smaller towers for my center if I have two center outputs and available amp channel?

You don't want to use two because one will have more uniform power response and off-axis behavior than two.
I use a full-range main speaker as a center channel....and it rocks. I use an infinity Kappa 9 laid horizontally as my center channel.
Ouch! If you lay that on its side, you are encumbering all (and I mean all!) the comb filtering and irregularity of any horizontal center and, probably, compromising the otherwise ideal match to your other Kappa 9s.

You are a good example of the market for which speaker manufacturers make horizontal center speakers.

Kal, technically you may be correct, however,in my system it sounds outstanding. I've tried other speakers designed specifically for center channel duty, and they just didn't measure up. Hearing is believing.

I have two Infinity Kappa Video Center speakers in my storage unit that I need to sell....they just didn't fill my room with enough sound. The size of my room pretty much voids all of the conventional rules that apply to center channels. When the makers of home theater make center channel speakers, I don't think they were considering that the room would be 70 feet long and 22 feet wide with a 22 ft ceiling height. After much experimentation, I found a solution for me. In a conventional sized room, speakers designed specifically for center channels might be a better option...but not in my case.
I have no problem with your satisfaction but you have traded a dynamically inadequate solution (dedicated center) for a spatially compromised one. If that is optimum, fine.

There are center speakers that will do fine in a large room, such as the B&W HTM1D or the JBL Synthesis units. Nonetheless, I would be surprised if you can achieve a really good sound field throughout with any standard home audio equipment.
I can understand lots of points made here. For Kr4 (Kal's) perspective, yes, he I believe he is right in his horizontal ,sideways dispersion position, relative comb-filtering, etc. Varying degrees of off-axis comb filtering apply, also, depending on crossover, relative design of speaker, driver positioning, etc, yes. Lot's come into play here.
As someone who's designed a few HT's in my time, I also try to integrated these types of speakers (or any for that matter) in a vertical arrangement, for such reasons. With a typical Dappolito designed speaker, stacked vertically, you tend to keep your wider dispersion (depending still on actual design of speaker, crossover design, and overall waterfall plot of speaker - note: even vertically arrayed, some designs still exhibit restricted horizontal dispersion, compared to others). Still, a vertically arrayed typical mid/woof surrounding a tweeter designed speaker, and similar will most always have better side-to-side dispersion characteristics than a horizontally arrayed speaker. For the most part, Kal is right here.
Most always, if you can get that speaker upright, and relatively well integrated in relation to the L/R speakers, you're gunna get better overall performance throughout your theater setup, likely.
I find issue with many options to use an otherwise full range, typical passive stereo speaker (likely with tweeter on top design) in the overall design effectiveness for a couple of reasons - especially if the overall setup of the systems is a situation where you have lots of ceiling and floor interaction reflections messing up your sound propagation from the speaker! If that's not controlled well enough, you'll be not only not adequately re-enforcing the direct sound that emits from your speaker (multiple drivers covering the same frequencies will make a stronger more dynamic re-enforcement of the sound, help eliminate of cancel out distortion), but will greatly help control ceiling to floor reflections, which need to be controlled (radically affecting dialog, detail, dynamics, imaging, and overall solidity of sound). And with your typical stereo speaker design, there's a tweeter atop a midrange, atop a bass driver. Rather than multiple drivers for stronger presentation, you are left with potentially "iffy" sound propegation subject to distortion, limited re-enforcement of the sound, and limited dynamics, comparatively, I find.
I would rather see multiple mid/woofers (as a minimum), likely multiple bass drivers, and even tweeters, depending, for the strongest sound, with lowest distortion, and most solid image from any given speaker (especially across the front) of a speaker array! It's been my experience that such dynamic piston designed speakers (not considering crossover and efficiency of speaker design) do lots of things better and more efficiently in for reproducing a dynamic, impact-full, very solid sounding presentation.
In contrast, your polite, laid-back, rather diffuse sounding speaker designs and arrangements leave much to be desired in an effective, hard hitting, solid imaging, ultra dynamic, cohesive multi-channel audio system - especially with the difficult acoustical conditions often facing home systems!
Yes, you can get otherwise descent results with some systems setup's - even in small spaces - with traditional stereo speaker designs (i.e, one tweeter and a woofer, for instance). But you really must consider the dynamic efficiency of the speakers, how hard you intend to push your system, relative size of room, and how far you are seated, proportionately, from the speakers, in relation to the boundaries - as closer proximity to your direct radiated sound will make for better sound quality. This is why THX accepts such designs for small spaces, where your dynamic needs of the speakers, and relative lack of ceiling boundary interaction with the sound is reduced. Because in such a set up, needs are reduced, you're hearing more of the direct sound being radiated from the speakers, in relation to boundary reflections from the room, etc).
Too often, you'll find people trying to use these traditional passive (even active designs like these would be more effective in a lot of ways than what we typically end up with at home) speakers in situations where there's inevitably going to be too many sonic compromises that result from improperly integrating the speakers in the system, and not working in a given application, so effectively! But, some would still swear they feel such setup's sound great! And yet the experts will still staunchly recommend otherwise. Well too each his own, I guess.
In any system given system there's bound to be compromises. And that's a fact. I find that the more you can limit such compromises, the greater you're overall results are going to be in a given system. Fail to consider or realize such compromises, and the results will speak for themselves. The more aware you are of "what's doing what" in your system, the more you can maximize and improve on the performance and effectiveness of your system, basically.
And still, the nice thing about this hobby is that you can make your recipe whatever you like! And perceived results and personal preference, options, bias's, will always vary.
Still, with all the greatly diverse speaker designs and inevitable setup variations that exist, one things for certain, and that's that results will greatly vary, depending on all the variables in play!
Lots going on in a multi-channel audio system. LOTS!
alright,I am new to trying to be an audiophile.I cant afford high end equipment but I am concerned with getting the best possible sound reproduction.I am using rotel amps and processor and I switch two two channel for music.I kind of understand what some of you have said about frequency cancellation with two drivers emitting the same signal,but not fully.So,for home theater I sould try to find the best matched center as opposed to using two speakers emitting the same signal on the sides of the screen?I know I can be slow on the uptake,I just want the best sound I can get with whats available to me
So,for home theater I sould try to find the best matched center as opposed to using two speakers emitting the same signal on the sides of the screen?

If you have excellent Main Right and Left speakers that image well and are dynamic and you do not invite a crowd regularly to the house (you and one significant other mostly) then I'd recommend using Phantom and use the money saved to buy a better amp or better subwoofer or better TV or better L and R mains.

If you find yourself needing a center channel with just yourself in the sweetspot listening then you should replace your main speakers - they probably don't have teh dynamic range needed for movie soundtracks - typical manifestation of this problem is either:

1. It is too loud and boomy when you can hear dialogue prooperly

2. You can't hear dialogue properly at modest levels.

=> a center channel will indeed help fix the dialogue problem but it is not adressing the root cause. Contrary to popular opinion, movie soundtracks often have much greater dynamic range than music - they therefore require very good speakers to do a decent job of imitating what you actually experience in a good cinema theater.
Many people (myself included) find that there's no center channel like NO center channel. If your seating has no one sitting outside one of your main speakers, try running your system with and without a center (to test your system without a center channel, tell your processor you have a "phantom" center). You may find, as I have, that your L+R main speakers provide a more stable, coherent soundfield and well-anchored dialog WITHOUT a physical center channel speaker than with one.

Everyone's installation is different, so there's no telling how many will find this helpful, but I know that I'm not the only one who has found this to be true. Good luck to all!
thank you,I will try no center and see how it sounds.I appreciate all the feedback.
I use a set of Klipsch KG5.5 as my rear LR and a single KG5.5 as my center with Khorns as my LR. the full range speaker works great but i have the room to do this in as my front projector screen sits in front of the center speaker.

That is the ideal way to do it - you need the right kind of screen for this but this is the perfect way.
OK, tried the "phantom" center yesterday, and I hate to say this, but it didn't sound good at all. Very hollow sounding, I tried some other setting changes, but just turning the center on again was a huge improvment.

Since I don't listen to multi channel music, I kept my excellent Definitive Tech CLR 2500 center with the powered 8" sub in it, from a previous system, great speaker.

Actually, when I downsized my AV system to just video based a few years back, I got rid of my high end 2 channel stuff and just used a reciever and bought all Def Tech speakers (BP 7004's for mains) with no sub. Just used the subs built into the 7004's and that system sounded very, very good. I'm a huge Def Tech fan now, maybe the best value I have seen in speakers.
>OK, tried the "phantom" center yesterday, and I hate to say this, but it didn't sound good at all. Very hollow sounding, I tried some other setting changes, but just turning the center on again was a huge improvment.

You probably have main speaker / room interface problems, most likely stemming from speaker placement relative to the walls (four feet off the front wall and a few feet to side walls is a nice place to start) and large objects (like a one-piece television; upgrading to front projection is in the top 3 things I've ever done for better audio performance).

A receiver with Audyssey equalization may be a reasonable work around for the problem.

You might get a bass boost at low frequencies with a phantom center (power response sums 6dB over a single speaker's output versus 3db at higher frequencies) although otherwise there shouldn't be a difference for listeners seated dead center between a phantom image and center channel.
I have a receiver with Audessey (Denon 3808ci), and I have spent considerable time with main speaker placement of my Maggie 3.6's, so I'm going to say no, to the problems you bring up. It just sounds better with a center channel.

I have often stuggled with the concept of the Center Channel. I have never been able to even imagine a center that could match up to my MonitorAudio Studio 20's and they image absolutely perfect. Recently i put in a small theater room for the family in the basement. I went with an old pair of NHT 2.0 that i had, and a Outlaw 1050 processor/amp. I have a pair of BG in-ceiling ribbons for the rears. At this point its a 4.0 system--no center, no sub. I just didnt get that far yet. However, after 2 weeks of listing to this 4.0 system i'm astonished at how incredible the 360 degree sound field is. Its better than my own system upstairs (Monitor Audio studio 20, MA 800 center, MA Gold in-ceiling, Rotel proc, Adcom power all around).

I had a hunch that the center was a problem. I did a little research and found tha the center channel is sort of meant only for theaters. WAY back, a long time ago theaters only had a center (mono). When they added 'stereo' in the 70's or so, they kept the center because it was there, AND because they needed even volume distribution over the 100' wide theater, addressing issues of people sitting way left or way right. This mono center channel insured the producer that the 'voice track' was at least evenly heard by the whole house. The .1 (sub) was added to expand the low bandwidth production that may not have been specd well in the old center, and LR mains.

None of these issues are present in my home surround system--or anyones for that matter. So i'm thinking that an audiophile 4.0 system will ALWAYS outperform a 5.1, or 7.1... The NHT's are rated down to 25 hz which is quite good, but it wouldnt hurt to have a sub in the system. So, in this application a 4.1 isnt a bad idea. However thats ONLY because the mains are a little lacking. Their big daddy, the NHT 3.3's would likely NOT need a sub.

Ny thoughts, comments?
"OK, tried the "phantom" center yesterday, and I hate to say this, but it didn't sound good at all. Very hollow sounding, I tried some other setting changes, but just turning the center on again was a huge improvement."

OK, for the record, to all the newbies, novices, and otherwise lesser experienced among us, the reality here is likely that there are many variables that effect the performance and results of a system. Simply changing one variable does not tell the whole story. For instance, there's a very very good possibility, in this situation, that the mains are likely located in a position in the room - relative to the seating area(s) - where there's a hole in the frequency response of the main left/right speaker setup. Also, there may be crossover issues, phase, etc.
Acoustics and system set up play such a huge part in the equation, that it all must be taken in context, when evalutating, trouble-shooting, and tweaking a system.
I would venture that there likely was not any care in setting up most of the system in regards to system response, initially here. So, to assume from the above statement that no center here is "not workable", is presumptuous. For informational purposes, anyway.
It is very very workable to PROPERLY setup a 2.0 or 2.1 system (allthough this is usually more effective dynamically, overall), sans the center. Not to say you should go without a center. But it can be done well, if properly considered and executed.
Thought I'd put my two cents in here...
IMO having the same exact speaker model on all channels would be the best choice. Yet I understand that doing this is probably not practical for most setups. Mains should be good over the full range, not just for mids.

My center channel (B&W) sounds very different (much worse) than my mains, yet they are both in the DM6xx family and have similar drivers. I just removed the center channel completely and told my Yamaha that there was none, and to send the signal to the mains.

I am currently in the process of setting up the room acoustics (traps, speaker positioning, etc.) so I'm not ready for a final verdict. At this point, it sounds different, not better nor worse.

I've recently read "Get Better Sound" my Jim Smith, and it discusses this topic and other related issues very well.