Doubling up on a channel?

[FNG212]

I'm not sure how to ask this question so I'm not sure how to search for it.

Is it possible to wire in two center channel speakers on one channel out of the receiver? I figure it might work if you had two 4-ohm speakers wired in series on an 8-ohm receiver/amp. Possible application is just to help fill the center sound stage during movies. Two vertically aligned speakers on a horizontal separation or two horizontally aligned speakers on a vertical separation might help reduce the disadvantages of each of the alignments. Thoughts?

This is one of those questions that gets pulled out of the "crazy question box" late at night, so regard as such.

 

[bandphan]

I'm not sure how to ask this question so I'm not sure how to search for it.

Is it possible to wire in two center channel speakers on one channel out of the receiver? I figure it might work if you had two 4-ohm speakers wired in series on an 8-ohm receiver/amp. Possible application is just to help fill the center sound stage during movies. Two vertically aligned speakers on a horizontal separation or two horizontally aligned speakers on a vertical separation might help reduce the disadvantages of each of the alignments. Thoughts?



This is one of those questions that gets pulled out of the "crazy question box" late at night, so regard as such.

Its been discussed several times and unless you have a VERY large projection screen to mount top and bottom, you will more than likely come up with combing issues, creating bad sound isues.

 

[Quickley17]

This is something I was also wondering about specifically with the center channel. Can you explain what you mean by combing issues?

 

[bandphan]

This is something I was also wondering about specifically with the center channel. Can you explain what you mean by combing issues?

When the two are placed in close range it creates nulls and peaks in the frequency, creating problems in time. This also can occur in smaller rooms and nearby surfaces.

 

[Pyrrho]

In addition to combing issues, there is also the idea of the whole point of a center channel speaker. If you have one speaker, the sound is coming from that one place. If you have two side by side, the sound, wired as you are suggesting, if sitting in a line directly in between them, would normally appear to come from halfway between them, which, presumably, would be at the center of the screen. But for anyone sitting off that line slightly to the side, they would hear the closer speaker more, so the sound will be off center. So you are partially defeating the purpose of the center speaker that way. If you put one above the other, then the sound will be getting further away from the screen, as it will appear to come from between the speakers, which will be further from the screen than the closer speaker is (the exception for that would be one above and one below, but you still would have combing issues). Use one speaker for the center.

If you need more sound in the center, you either have things set improperly, have terrible speakers, or you have your right and left speakers too far apart. In a theater, typically, the right and left are, like the center, behind the screen. So for the sound, you do not want the right and left speakers far apart from the screen, or it will sound like someone talking on one side of the screen is further to that side than he looks like he is.

 

[Quickley17]

You're very helpful Pyrrho. Thank you. Is there a noticable difference in localization between center channels that only have one or two drivers and very wide center channels that have 4 (maybe even more?) drivers side by side? I guess what I'm asking is, would a wider center channel with more drivers side-by-side help you differentiate between characters on the left and right side of the screen more easily? I'm guessing no because I think the same signal would be going to all of the drivers? I guess some drivers could have a different crossover than others even if they are the same size, but that wouldn't change the ability to pinpoint sound in different places... OK I'm rambling, I'll stop.

 

[Pyrrho]

You're very helpful Pyrrho. Thank you. Is there a noticable difference in localization between center channels that only have one or two drivers and very wide center channels that have 4 (maybe even more?) drivers side by side?

It will depend somewhat on how carefully the speaker was designed, but rather interestingly, center channel speakers are more often designed for appearance and fitting in certain kinds of spaces, than for actual sound quality. In most cases, a vertically placed bookshelf speaker of the same line of speakers for the center would sound better than the regular center channel speaker.

I guess what I'm asking is, would a wider center channel with more drivers side-by-side help you differentiate between characters on the left and right side of the screen more easily? I'm guessing no because I think the same signal would be going to all of the drivers?

Your guess is correct, with normal center channel speakers. Some, however, are three speakers in one, so that the front left, center, and right speakers are all housed within one cabinet. These are usually made for space, rather than optimum sound.

I guess some drivers could have a different crossover than others even if they are the same size, but that wouldn't change the ability to pinpoint sound in different places... OK I'm rambling, I'll stop.

With a multidriver setup, it is more complicated than with a single speaker, but you still have the localization based upon the particular speaker making the particular sounds. In other words, if you have a woofer and a tweeter, the treble is coming from the tweeter, and the bass is coming from the woofer. If you have two woofers, the bass will appear to be coming from in between the two woofers, and so a horizontal placement, like most center channel speakers, will cause the center of the bass to be off center for everyone who is not sitting in a line bisecting the speaker (see above). However, treble is more directional than bass, so it matters more, but this is a reason why it is generally better, if you have room for it, to have a bookshelf speaker positioned vertically for the center speaker. I use identical bookshelf speakers for all channels (except subwoofer, of course), and they are all oriented vertically.

 

[Bugbitten]

I have used dual centers for over 4 years now with no issues.

I use bookshelves above and below the screen wired to the same amp output.

The dialog is tied to center screen very well.

Try it to see for yourself.

 

[fredk]

I have dual centers (vertical bookshelves) above and below the screen and this works very well (65" rptv). Horizontal centers above and below will work very well also.

It is with two centers in a horizontal arrangement, you will run into comb filtering issues, though I havn't tried that

 

[AcuDefTechGuy]

I've tried 2 identical center speakers (2 vertical) and it sounded TERRIBLE!

 

[FNG212]

I have dual centers (vertical bookshelves) above and below the screen and this works very well (65" rptv). Horizontal centers above and below will work very well also.

It is with two centers in a horizontal arrangement, you will run into comb filtering issues, though I havn't tried that

How do you have them wired coming out of the amp/receiver? What kind of speakers are they? Still the M2's from your sig? What kind of amp/receiver?

 

[Lordoftherings]

I have some receivers with two center channels outputs.
I did try it years ago, but I dismiss it very quick.

In my honest opinion (and others too), it is a bad idea to use two center speakers. Someone have already mentioned the combing effects, that's very true. It is a Mono signal, it is not Stereo.

* Check several articles on this subject, and you will see the negative impact of doing so. Even for a large screen (more than 120"), it is still a bad idea.

This is only my personal opinion, and also the one from various reputable audio pro people.

Bob

 

[ZeosPantera]

I have used dual centers for over 4 years now with no issues.
I use bookshelves above and below the screen wired to the same amp output.
The dialog is tied to center screen very well.
Try it to see for yourself.

I Just today mounted one of my two KLH 2100i Monitors above my 106" Screen. For the last 2 years I grew very annoyed by every sound coming from 4 feet below the center of the screen. However I seemed to be the only one bothered by it. I took precise measurements to to make sure the top speaker is the same distance from my head as the lower.

My suggestion is, If it isn't to hard to set up. try it. I recommend closing your eyes while testing because seeing a speaker above my screen screwed with my head a bit. I kept looking at it thinking it was louder then the bottom. It wasn't.

 

[Swerd]

There have been several comments about how using two speakers sharing one channel can suffer from comb filtering. This will be less of a problem with speakers mounted above and below a screen, but can be a problem with more than one speaker mounted at the same height. Sound in the center may be OK, but as you move left or right, there may be cancellations causing holes in the sound.

In your original post, you asked

Is it possible to wire in two center channel speakers on one channel out of the receiver? I figure it might work if you had two 4-ohm speakers wired in series on an 8-ohm receiver/amp…

When you wire two speaker in series this way, the second speaker in the series does not get a full range audio signal like the first one. The voice coils in the woofer and tweeter will act as low-pass filters. I don't know how audible this will be for a center channel with largely spoken dialog as the content, but it would be better to avoid this problem and wire both speakers in parallel with each other.

 

[walter duque]

I used 2 center channels a while back. Mounted horizontal below and above display driven by 350 watt amps each. Did sound great. Now I use the same speakers for rear surrounds. Try it you might like it.
http://www.sourcespeaker.com/LS26.html

 

[lsiberian]

This is really a matter of personal preference IMO.

Blind fold people and you might be surprised at how poor they are at telling differences. As with all audio decisions. I suggest you get a friend to double blind test you from where you sit. If you can pass the test numerous times at discerning improvement with 2 channels do it. If not ignore it and move on. Much time is wasted on things that don't really improve sound. I can't stress enough the importance of double blind testing. If people practiced this more often you'd see a lot of myths dispelled and a lot of money saved.

I suggest you do it and share your results with us.

I personally see no need for this. I think the cost and complication out weigh the benefits significantly. I have the same view of AT screens too. I'd rather have a higher picture and use whatever material I want.

That may change someday when the AT screens get cheaper. But I don't do critical listening in movies. I enjoy watching them too much to get to fancy. The main issue for me is getting the soft volumes up enough to hear.

 

[Lordoftherings]

The main issue for me is getting the soft volumes up enough to hear.

With a receiver or a pre/pro that has Audyssey Dynamic EQ, your issue would be at rest.

Also, In found that adding a couple more dbs to my center channel, does help in many cases.

 

[Pyrrho]

This is really a matter of personal preference IMO.

Blind fold people and you might be surprised at how poor they are at telling differences. As with all audio decisions. I suggest you get a friend to double blind test you from where you sit. If you can pass the test numerous times at discerning improvement with 2 channels do it. If not ignore it and move on. Much time is wasted on things that don't really improve sound. I can't stress enough the importance of double blind testing. If people practiced this more often you'd see a lot of myths dispelled and a lot of money saved.

I suggest you do it and share your results with us.

I personally see no need for this. I think the cost and complication out weigh the benefits significantly. I have the same view of AT screens too. I'd rather have a higher picture and use whatever material I want.

That may change someday when the AT screens get cheaper. But I don't do critical listening in movies. I enjoy watching them too much to get to fancy. The main issue for me is getting the soft volumes up enough to hear.

In a way, everything about it is personal preference. If, for example, one wanted to place the front center channel speaker in the left rear position, there is nothing to stop someone from doing that. There is, of course, the issue of the original intentions, but one need not slavishly follow that. It is, however, good to distinguish between the way something was intended and the ways that it was not, as some people do wish to try to set their system up in a manner that achieves the intended results, as closely as reasonably possible.

And this distinction is useful to remember when reading (or giving) advice about how to set things up. I generally advise people in the direction of "proper" setup (i.e., setting things up to achieve the originally intended results, as close as reasonably possible), but naturally people should experiment somewhat and modify things to suit their own tastes. But when they do that, they should not confuse what they are doing with what was intended by those who made the recording.

 

[Pyrrho]

With a receiver or a pre/pro that has Audyssey Dynamic EQ, your issue would be at rest.

Also, In found that adding a couple more dbs to my center channel, does help in many cases.

It does not need to by Audyssey; some other brands work fine for adjusting levels of various frequencies to achieve a relatively flat response. And in fact, if you are using Audyssey, and you still need to boost the center channel to understand the dialog, obviously, Audyssey is not solving your problem.

Assuming we are talking about a well recorded soundtrack, there should be no need to boost the center channel speaker. If that is necessary to understand the dialog, it is likely that the center channel does not satisfactorily reproduce the relevant frequencies accurately. I would suggest looking for better speakers, if one can afford them. If one's speakers are good, and if the recording was competently made, there is no need for any extra boosting of the center channel; all should be balanced equally.

Naturally, anyone may adjust their system to their tastes, however that may be.

 

[fredk]

How do you have them wired coming out of the amp/receiver? What kind of speakers are they? Still the M2's from your sig? What kind of amp/receiver?

They are wired in series from the receiver to speaker A and from Speaker A to speaker B. Still the M2s connected to a low end Sherwood receiver.