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Formulating a new theory on Center Speakers...


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#1 of 29 OFFLINE   Kevin_R_H

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Posted May 09 2003 - 04:55 AM

Something has been bugging me for the last 6 months or so. It has to do with my opinion on the necessity of Center Speakers. I have tried 3 different Center Speakers in my HT, and ALL of them have worsened the sound (as opposed to having no Center Speaker at all).

Based on this experience, I have voiced this opinion (Center Speaker is unnecessary) a few times on this board. But since an overwhelmingly majority of you disagree, I keep trying to come up with theories to help me to understand why. I know what I'm hearing, but can the countless thousands on this board be wrong?

Some of my theories have been:

1) The Center Speakers I've tried were not a tonal match for my mains, and this degraded the overall presentation. This goes along with what many on this board profess (how your center speaker should be a match for your mains).
2) The signal to my Center Speaker comes directly from my cheapie HT integrated, while the signal to my mains passes through a more-expensive tube preamp and tube monoblocks. This makes the tonal mis-match even more apparent.
3) My RM40 Main Speakers do a singularly wonderful job of keeping the Center dialog locked into place, regardless of sitting position. Most Main Speakers cannot duplicate this ability.

However, something keeps gnawing at me - telling me no combination of these is the real reason why. Why can't I see what should be so readily obvious?

And then, last night, something came to me. Perhaps the reason I don't feel the need of a Center Speaker is because I utilize a Front Projector in my system. Therefore, there is nothing on the front wall between my speakers. No entertainment center, no audio/video rack, no giant RPTV.

Now, I did this because I didn't want anything detracting from my 2-channel enjoyment. Soundstaging and imaging for 2-channel are greatly affected by "stuff" between your stereo speakers.

Well, if that's true, shouldn't an RPTV have the same detrimental effect on any HT system that has no Center Speaker? I'm now thinking that this may be the single most important reason my system can excel at HT dialog, where most feel you MUST have a Center Speaker to solidify the dialog across a wide listening area.

Maybe only those with a TV between the Main Speakers truly need a Center Channel, because otherwise their dialog is being broken down just as it would for 2-channel music.

Does this make sense?

Kevin

#2 of 29 OFFLINE   Bob McElfresh

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Posted May 09 2003 - 06:28 AM

Good theories.

Yes, the giant 'box' of an RPTV can cause early reflections. Thats why pulling the L/R speakers forward and giveing them some toe-in is typically done.

You also have to realize that "Immaging" in the tradtional 2-channel world was to create a phantom image in the middle. If you put a center speaker in a system that aligns the L/R speakers following 2-channel placement theory, you now have things conflicting.

With a center speaker in a HT system, you want to position your L/R speakers a bit wider, and with less toe-in to create a 'hole' in the middle of the soundfield. The center should then fill this in. Now as dialog/effects move across the front speakers, the sound-source changes and draws your attention to the location.

Some people prefer the "no-center" approach, and it's your system - suit yourself. Dont let anybody tell you it's wrong.

#3 of 29 OFFLINE   Scott Oliver

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Posted May 09 2003 - 07:35 AM

What are you trying to do Kevin, widen the gap between us primarily 2 channel proponents vs. the 5 channel timbre-matched proponents.Posted Image

Aren't we pariahs enough on the forum without you stirring up trouble?

BTW, I currently have a 35" TV between my speakers and still greatly prefer no center, although I am scheming of ways to rid myself of the set to make further improvements.Posted Image

IMO, I think a big reason why this phantom center set-up is great for us, is the quality of our main speakers and the gear driving them, plus the fact that our system usage time is heavily slanted to 2-channel music listening.
-----------------------------------------------------------
Oh and off topic, I got my new Granite Audio tube preamp into the system, and it already blows the Theta CasaNova out of the water for CD listening. This surprised me because my only source in house right now is a Sony S7000 DVD player, that is noted as having a fine transport, and good video, but I don't think any one has ever said anything positive about it's DACS and analog output stage. And I will more than likely be adding a Nottingham Analogue Spacedeck w/Spacearm in June. Drooling in anticipation!

#4 of 29 OFFLINE   Kevin C Brown

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Posted May 09 2003 - 07:53 AM

You might find that, for proper imaging of the phantom center channel info *without* a center channel, the true 'sweet' spot will only be exactly 1/2 way in between the main speakers. For seating positions not exactly at that 1/2 point, the center ch image will be pulled off to the main speaker that you're closer too, and obviously, away from the center point of the screen. That's really the only benefit to a center speaker: it keeps the center ch info pinned to the display.

One way to help deal with the early reflections of a center speaker on a TV, is to increase the crossover freq to the center ch, as the effect of those reflections is more apparent with lower freqs. But then if you go to high (much higher than 80 Hz), your bass becomes too localizeable to the sub and not to the center ch where it's supposed to be coming from.
If it's not worth waiting until the last minute to do, then it's not worth doing.

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#5 of 29 OFFLINE   Kevin_R_H

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Posted May 09 2003 - 08:35 AM

Kevin,

I'm sorry I wasn't more clear. In my system, I have an 8 foot sofa as my main listening space. When more seating space is needed, I also set up a chair on the OUTSIDE of this sofa (to the left). This puts this listener almost head-on with the Left-Channel Main Speaker.

However, in my system, in my listening room, there is little to no degradation of dialog/sounds when sitting in this "outside chair". And I know this, as I usually take this off-center chair. I currently do not utilize a Center Speaker.

So again, that is why I posed this question. Why does my system excel at presenting a wonderful HT experience across a wide listening area when everyone claims it can't be done without a Center Speaker?

+++++++++++++++++++++++++++++++++

Hello Scott.

Thanks for responding. How did you come about the Granite Audio? That was not even on your list of contenders. That being said, it certainly comes highly praised. But I didn't expect it to better the CasaNova in processing CD input.

As for the Nottingham, they are cool looking, and my time spent with one also impressed me with their sound. Are you buying it as a kit? Also, what cartridge will you mate with it? Either way, I'm sure your vinyl will sound wonderful. You certainly have one of the nicest audio systems I'm familiar with, and the Nottingham will just make it better.

Also Scott, you mention the TV between your speakers, but where is you other equipment (sources/electronics)? I assume they along a side or rear wall. I think I mentioned to you my other gear is along the rear end of my RH side wall. Of course, each of my monoblocks sit on the floor behind the speaker they drive.

+++++++++++++++++++++++++++++++++++

Bob,

Thanks for the info on locating the Center Speaker. I think it's true I never adjusted the RM40s from their locations where they give the best stereo sound. Perhaps, had I readjusted their locations for HT, I could have coaxed some better sound from the Center Channel.

Of course, at 260 lbs each, I'm not crazy about playing with the RM40s' placement. They can stay where they're at!!!

Kevin

#6 of 29 OFFLINE   Scott Oliver

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Posted May 09 2003 - 09:18 AM

Actually all of my gear currently except the subwoofer is between my speakers on Atlantis Reference racks. However I will be moving to a new house in June and will have either sold the TV or be relagating the TV to the bedroom there. Then I will plan on placing the equipment rack outside of the speakers on the front wall with only a new amp stand and acoustic treatments between the speakers. This should certainly improve my phantom center even more so.

Like you, I also often sit outside of the speakers currently and yes the sound isnt coming from dead center on the TV but it is coming from just left if I am sitting to the left. And for me if it isn't dead center I can live with it, but if it didn't sound realistic enough then I couldn't. And this arrangement with my speakers have been better than any center channel speaker I have ever heard in terms of sounding real.

#7 of 29 OFFLINE   Chris Tsutsui

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Posted May 09 2003 - 10:12 AM

Quote:
Why does my system excel at presenting a wonderful HT experience across a wide listening area when everyone claims it can't be done without a Center Speaker?


Because you love the way it sounds as do many with a nice pair of mains. Posted Image

But, lets see how sitting off axis with a center can be better than sitting off axis with a phantom:

One problem with sitting off axis with a phantom is the inter-channel phase and timing information that becomes an issue which can destroy instrumental overtones (timbres). First figure that an 1100hz harmonic has 12 inches in length. Then 4khz is like 3 inches, etc. Now imagine a female vocalist singing in the phantom center. If you sit two feet off center, that means that any fundamental notes and harmonics from at least 500hz and above have been altered. This is both audible, and measurable.

The different timing of sound from each speaker can mess up harmonic relationships. Because the positive cycle of a 100hz overtone arrives at your ear from the closer speaker before it does from the other one, it will cause a change at that frequency (harmonic overtone). Should the distance be equivalent to a half-wave length further (6 inches), then that particular overtone (harmonic) will arrive exactly out of phase.

One easy test for this is to play pink noise, and move from the center, to an off axis position. Then listen for a change in tonal ballance which is exactly what happens when you sit off axis with a phantom center.

Now with a center channel, you don't have to worry about this because it's only "one" speaker playing the vocal overtones and "genetic code" of a voice. Since you are hearing the correct harmonic (overtone) structure, you'll be hearing closer to what the director intended in the center "vocal" channel. Posted Image

A center channel can also help the dynamics of the HT. (Three speakers with 100w each can get louder than 2 speakers with 100w each)

The speakers also have less to play at the same time which can result in improved detail. The center only plays the discrete dialogue, while the mains play the discrete music rather than 2 speakers having to play "everything" at once. You're basically dividing the information that the speakers have to play between 2 discrete channels to reduce the work the speakers have to perform.

I highly doubt that "everyone" needs a center channel for HT as I'm certainly not one of them. However, if I had the choice of adding an identical speaker as a center, I'd probably take it.

I remember when I had floorstanding GR-Research AV3s as mains and to use an "identical" center, I had to prop one AV3 on its side so the tweeter was in the middle. Using 3 AV3s in the front stage, I got a suprisingly well integrated front, that easily rivaled the 2 channel performance. Of course I don't run a floorstander on its side because it's not practical and I'd rather run phantom and just not sit off axis.

Quote:
3) My RM40 Main Speakers do a singularly wonderful job of keeping the Center dialog locked into place, regardless of sitting position. Most Main Speakers cannot duplicate this ability.
I know your RM40s probably have nice imaging, but perhaps your room could be blurring the image. A panned mono center image generally appears to shift left or right in the direction that the listener moves. A speaker with good off-axis response means it directs highs in all directions to interact with the room. A speaker with a small sweet spot means the highs get pointed towards the listener, and not get wasted elsewhere which can cause problems.

I do agree with Kevin B. on how the primary benefit of a center is the wider sweet spot, but had to include part of the esoteric side I learned from Jim Smith of Avantgarde.

IMO, you don't need a center if you're happy with the performance. I acknowledge that off axis phantom might sound different, but can live with it because it doesn't distract me from the movie... for now at least... Posted Image


#8 of 29 OFFLINE   EarleD

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Posted May 09 2003 - 02:05 PM

Im building a modified center from a Klipsch KG 4.2. I use 5.2's as my mains and surround.

Im hoping using an identical horn and driver will really solve my center speaker mismatch(curently a Klipsch KG 2.2v). It will also give a center channel that has real output down to around 40-50hz. I hope.Posted Image

Center channel speakers seem to be the weakest link in many HT's. People will get floor standing speakers for mains and then expect a small center channel to keep up.

Im rebuilding the motor board and putting the k-85 horn in the center. Wish me luck.

Earle

#9 of 29 OFFLINE   Kevin C Brown

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Posted May 09 2003 - 07:35 PM

Chris- Excellent info! (I have to remember that.)

In fact, if you're sitting right in front of one of the main speakers, theoretically it's impossible to have a stable center image inline with the display. Why? Because you're closer to that speaker, it *will* sound louder, hence it will *pull* the image to it.
If it's not worth waiting until the last minute to do, then it's not worth doing.

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#10 of 29 OFFLINE   Yee-Ming

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Posted May 10 2003 - 05:16 PM

Quote:
Because you're closer to that speaker, it *will* sound louder, hence it will *pull* the image to it

hmmm, so if I have non-symmetrical placement of my front pair, I should boost the volume of the speaker further from centre?

because of the entertainment centre, my right-front is further out than the left-front from the "centre spot" as defined by the centre of the TV (I place the centre speaker directly under the TV, so not an issue in 5.1 HT). so to compensate, for when I listen to 2-ch stereo only, I've toed the right speaker in a bit more than the left, the theory being to "shift" the sweet spot more to the left, to match the seating position directly in front of the TV. is this correct?

any help/comments greatly appreciated.

#11 of 29 OFFLINE   Kevin C Brown

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Posted May 10 2003 - 05:59 PM

Yee- Yes. But you have balanced levels with an SPL meter, right? Posted Image That takes care of it for you. The sweet spot is governed more by volume than toe in. Toe in just helps with imaging quality but not where the image is located.
If it's not worth waiting until the last minute to do, then it's not worth doing.

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#12 of 29 OFFLINE   Clyde Metz

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Posted May 11 2003 - 09:56 AM

Keven
With the VPMS mains I wonder why you didn't try the LCR from VMPS?
Clyde

#13 of 29 OFFLINE   Chris Tsutsui

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Posted May 11 2003 - 11:03 AM

Yee, if you can't sit between the stereo speakers, I would adjust the left right balance. (Until equal volume is achieved)

I would also make sure both speakers toe-in towards the listener equally. I generally like aiming speakers 2-3 feet behind the listener's head, but if that's still too bright/edgy then you could have them intersect further behind.


#14 of 29 OFFLINE   Philip Hamm

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Posted May 11 2003 - 12:06 PM

The ideal solution is three identical speakers in the front running through identical amplification.

Would you run a L/R pair as two different speakers? Even if they were "matched" they would sound wack and stereo imaging would be out the window. It's the same thing with the center.

Here's my front soundfield, with identical amplification and speakers all the way across. It sounds very nice.

Posted Image

Anything else is a compromise.
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#15 of 29 OFFLINE   Brian Bunge

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Posted May 11 2003 - 02:19 PM

Kevin,

Since you're in Tampa, maybe you should go over to Home Theater Talk and contact Mike Knapp. He has an all Adire Audio setup for his HT. It's my understanding that it's an excellent setup. Maybe you can hear his system and see if you still feel that no center channel is best. Oh, and I hear his separate 2-channel setup is rather impressive also! Posted Image
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#16 of 29 OFFLINE   Kevin C Brown

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Posted May 11 2003 - 04:16 PM

Philip- Hopefully you tilt that center speaker a little towards where your head would be. Posted Image Otherwise, you're probably getting the high freqs rolled off due to the off-axis angle... But you are correct, 3 identical speakers are the way to go... (I can see the 950 right in the middle of your rack!)
If it's not worth waiting until the last minute to do, then it's not worth doing.

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#17 of 29 OFFLINE   Philip Hamm

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Posted May 12 2003 - 12:59 AM

I don't tilt it. My seating position is about 15 feet from the TV so it makes very little difference. The tweeters are only about 10-12" different in height across the front, which is nice. I have the center sticking out about 1/2" in front of the TV, and cross over the center at 100Hz and the mains at 80Hz. between 80 and 100Hz is some nasty "box effect" from the RPTV.
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#18 of 29 OFFLINE   Kevin_R_H

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Posted May 12 2003 - 04:45 AM

Clyde,

I didn't buy the VMPS LRC because I was out of money. I had a budget for my new system, and the VMPS center is ~ $900. Perhaps I could have added a VMPS Larger Sub, as well. But that would have cost another $600 (plus the price of an amp).

So, I had to consider which I would prefer. RM40s with TRT capacitors, or RM2 with LRC and Larger Sub. Perhaps for HT, it would have been close. But for 2-channel (which is 80% of my usage), the RM40s were the way to go.

Do I believe the VMPS center would improve my setup? I'm doubtful at this point. I understand the theory that it would be a "tonal match" for my Mains, as the other "pretenders" weren't. However, I wonder about that "tonal match", as the signal to any Center Speaker in my system would come directly from a relatively inexpensive SS HT integrated amp. While the signal to my Mains come from that HT amp into my tubed preamp, and then through my tubed monoblocks. I tend to think that even if I had another RM40 on its side, that the resultant "sound" would be different from my Mains.

++++++++++++++++++++++++++++++++++

Brian,

Thanks for the tip. I'm sure Mike's sytem sounds wonderful. However, my second system is a full 5.1 setup, anchored by Thiel CS-3.5 speakers, which are driven by a separate power block. It is a pretty nice setup, but my VMPS 4.0 system is noticeably better. Being an audio junkie, I have also spent considerable time with other folks with very nice HT setups (3 of whom have more cash invested than I do).

In addition, I have now had about 15 HT junkies at my house - and all agree the sonic superiority of this 4.0 system. In fact, to a person, they are always shocked there is no subwoofer nor Center. However, the big kick comes when I put on an album. That's when some get this glazed look on their face, begin elbowing each other, and start whispering things I can't hear.

Do I believe I have some kind of "ultimate Home Theater rig"? Of course not. My HT integrated amp cost less than $450, and my surrounds are PSB Alpha S Bipolars. I have no doubt that a critical HT ear can notice the limitations of this setup. I fully accepted those limitations as a HT compromise, so as not to compromise my 2-channel enjoyment.

Look, I fully understand the theoretical and pratical advantages of having a Center Speaker. This thread was started simply because of a hunch I had that possibly Center Speakers give more benefit to systems that have a TV and/or and Entertainment Center between the Mains. I was hoping that someone else with a Front Projector based system would chime in their opinions of the pros/cons a Center Speaker makes in their system.

Kevin

#19 of 29 OFFLINE   Kevin C Brown

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Posted May 12 2003 - 07:51 AM

Philip- Yeah, usually less than 15 deg doesn't pose a problem.
If it's not worth waiting until the last minute to do, then it's not worth doing.

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#20 of 29 OFFLINE   Stephen_Dar

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Posted May 12 2003 - 12:56 PM

I just have to chime in here and offer a general observation. I operate now with just 2 main speakers (Nautilus 803s) and a subwoofer (Bag End infrasub). System is powered by Krell. I'm very happy with my sound, and beyond the issue of clutter, one growing reason I haven't upgraded to multi-channel surround is all my listening tests keep pointing to the potential for such systems to create distraction and indeed decrease the overall quality of the sound field. I'm basically chiming in in support of the original poster. I know most disagree.

Yes, I haven't tried to live with such a multichannel system, but I have spent time with friends' set ups and done a bunch of listening tests. I don't care for the center channel handling all dialog. One single speaker just doesn't seem to render anything close to the rich sound field I have now. How can one speaker convey the positional differences of 2 or more speakers on screen? I had figured all 3 front speakers would be used to handle such nuances, but from the testing I've done, it seems that isn't the case, it all gets restricted to the single center channel. Maybe I'm missing something, but so far the idea of the single center being so important seems unwise to me.





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