# Anyone using multiple fronts and centers?



## Scuba Diver (Sep 28, 2007)

I would like to know if anyone is using 2 or more centers, fronts, and backs. Do you like the results? Does it require the need for seperate amp? Or is a quality Stereo enough to get the job done?


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## Kal Rubinson (Aug 3, 2006)

Scuba Diver said:


> I would like to know if anyone is using 2 or more centers, fronts, and backs. Do you like the results? Does it require the need for seperate amp? Or is a quality Stereo enough to get the job done?


I cannot think of any good reason to do this in a domestic situation. 

Kal


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## Prof. (Oct 20, 2006)

Several HT builders at AVS have more than one centre speaker..as I have also..but not duplicate L or R or backs.

They have one centre speaker mounted above the screen and one mounted under the screen..
Angling a single centre speaker up or down can sometimes have an adverse effect..particularly with centre speakers that have rear firing drivers and or ports
Instead of directing the sound towards the centre line of the screen, the sound becomes more localized, infact not angling the speaker can sometimes work better..

Having a top and bottom centre speaker helps to offset the problem..
I have three centre speakers, one above the screen and two below...The top speaker has two rear firing bass speakers and ports, and the bottom speakers have rear firing ports..

They are wired in series/parallel to maintain impedance matching with the other speakers..

The result of this setup is that I get good strong pinpoint voice location across the entire screen, with no emphasis above or below the horizontal centre line of the screen..


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## Kal Rubinson (Aug 3, 2006)

Prof. said:


> They have one centre speaker mounted above the screen and one mounted under the screen..


In compensation for other problems but not ideal.



> Angling a single centre speaker up or down can sometimes have an adverse effect..particularly with centre speakers that have rear firing drivers and or ports
> Instead of directing the sound towards the centre line of the screen, the sound becomes more localized, infact not angling the speaker can sometimes work better..


 Rear firing drivers are already suboptimal unless they are cutoff below 200Hz or so and angling also is compensating for sub-optimal placement. 

<<<snip>>>


> The result of this setup is that I get good strong pinpoint voice location across the entire screen, with no emphasis above or below the horizontal centre line of the screen..


Again, it is in compensation for being unable to place the speaker where it should be (and I acknowledge the difficulty without an AT screen). Are all three in the same vertical axis? :bigsmile:

Kal


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## Scuba Diver (Sep 28, 2007)

After reading both posts it looks to me that one set of perfectly placed speakers (as long as room acoustics and space permit such a set up), should be all any in home theater should require. However, if you have a difficult lay out or lack the knowledge or proper testing equipment installing several speakers can correct poorly placed speakers allowing you to obtain the same goal. Is this correct? If so it is a matter of money. You can place speakers right or spend more money on extra speakers and place them in ok positions. 

I only have the two of you to go by so I guess I will need to pull out some old speakers and try doubling up and see what kind of improvements I get. I may need more speaker wire for the test and was trying to prevent spending any money. 

Thanks for the advice. I will try both of your suggestions.


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## Prof. (Oct 20, 2006)

Kal Rubinson said:


> Again, it is in compensation for being unable to place the speaker where it should be (and I acknowledge the difficulty without an AT screen). Are all three in the same vertical axis? :bigsmile:



Vitually, yes...The bottom two are side by side (upright), in the vertical centreline with the top speaker..
I originally tried it with just one at the bottom, but the top big one ( which has 7 speakers in a 3 way crossover system) is an 6 ohm unit and is more efficient than the bottom 2 way 6 ohm speaker..So I parallel wired the two bottom speakers, and series connected the top speaker, giving an approx. total overall of 9 ohms..The Receiver is set to 8 ohms..
This just about perfectly matched the efficiency of all the speakers..

I only claim that this is only practical when using centre speakers that have rear firing speakers and or ports..
If one is using a standard sealed system or a bass reflex system with front ports, then one speaker above or below the screen is all that is needed..


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## Prof. (Oct 20, 2006)

Scuba Diver said:


> However, if you have a difficult lay out or lack the knowledge or proper testing equipment installing several speakers can correct poorly placed speakers allowing you to obtain the same goal. Is this correct?


It's not the placement so much, just about anyone can find a suitable centre position for their speaker, it's more the type of centre speaker as I've mentioned in the post above..

If you are using a sealed enclosure type speaker, or a BR with front ports, then one above or below the screen is all you need..
Other than that, the centre speaker should match tonally and efficiency wise with your left and right speakers..


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## salvasol (Oct 31, 2006)

> I would like to know if anyone is using 2 or more centers, fronts, and backs. Do you like the results? Does it require the need for seperate amp? Or is a quality Stereo enough to get the job done?


Why you want two or more set of speakers???? :scratch::scratch:

I have two pairs of front speakers (2L + 2R) :bigsmile: ... I got opinions that I might have problems, but I didn't listen :hide: and set up the two pairs ....

I did it, not because I was lacking sound, the speakers sounded good to me (but, I need to use REW to know for sure how my system is performing) ...:yes::yes:I did it, because I removed a pair of speakers that I was using as surround, and instead of putting them away I decided to add that pair in the front .. now I'm using them with the speaker selector A + B in my receiver.

I gained 5bds using the four speakers instead of two ... but after I use REW, I will decide to keep it or remove it ...:dontknow:


Here is a picture of what I have (you can see that my speakers are small, that help with position)


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## Prof. (Oct 20, 2006)

Do you get a "bigger" sound from the dual left and rights?...
This was something that I was going to try, but was advised that it's not the best idea to combine A+B speakers on the receiver..


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## Kal Rubinson (Aug 3, 2006)

Prof. said:


> Vitually, yes...The bottom two are side by side (upright), in the vertical centreline with the top speaker..


Both cannot be in the vertical centerline if they are side-by-side. They will interfere with each other.



> I originally tried it with just one at the bottom, but the top big one ( which has 7 speakers in a 3 way crossover system) is an 6 ohm unit and is more efficient than the bottom 2 way 6 ohm speaker..So I parallel wired the two bottom speakers, and series connected the top speaker, giving an approx. total overall of 9 ohms..The Receiver is set to 8 ohms..
> This just about perfectly matched the efficiency of all the speakers..
> 
> I only claim that this is only practical when using centre speakers that have rear firing speakers and or ports..


This is such an odd-ball setup that no lessons can be drawn from it. If it floats your boat, fine.

Kal


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## Kal Rubinson (Aug 3, 2006)

salvasol said:


> Why you want two or more set of speakers???? :scratch::scratch:
> 
> I have two pairs of front speakers (2L + 2R) :bigsmile: ... I got opinions that I might have problems, but I didn't listen :hide: and set up the two pairs ....
> 
> ...


I grew out of these machinations when I was a kid. If you use REW, try measuring a few microphone positions within several inches of each other. Bet they show widely varying results.

Kal


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## jackfish (Dec 27, 2006)

I would stack them vertically in a WTTW configuration and see if there is an improvement, especially in the midrange. I have Large Advents so stacked and the sound is incredible.


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## salvasol (Oct 31, 2006)

Prof. said:


> Do you get a "bigger" sound from the dual left and rights?...
> This was something that I was going to try, but was advised that it's not the best idea to combine A+B speakers on the receiver..


Do you remember Why is not a good idea to combine A + B speakers???

I gainned 5 bds using them together (I used the SPL to measure the sound with one and the two pairs and that was the difference) :yes::yes:

This is a temporary set up ... I have to use REW to measure the response to decide if I keep it or not.
Somethimes we like to experiment things, Right :bigsmile::bigsmile:


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## salvasol (Oct 31, 2006)

jackfish said:


> I would stack them vertically in a WTTW configuration and see if there is an improvement, especially in the midrange. I have Large Advents so stacked and the sound is incredible.


My problem is that the ceiling if very close (about 12") and if I stack them vertically I'm not sure if they will fit :dontknow::dontknow:


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## Otto (May 18, 2006)

salvasol said:


> Do you remember Why is not a good idea to combine A + B speakers???


Most likely because they will be run in parallel, thereby presenting a difficult load to your receiver/amp. Depending on the receiver/amp, this may or may not present a problem. If it's a problem, it will most likely be present at higher volumes, as that's when the most current will be demanded from the amplifier. All that said, I have done all types of parallel speaker installations and A+B installations (my own stuff, I'm not a pro "installer") over the years and have never had a problem. If you find that your receiver/amp is getting hot, distorting or shutting down, then you have a problem. If not, go for it.



> I gainned 5 bds using them together (I used the SPL to measure the sound with one and the two pairs and that was the difference) :yes::yes:


Yeah, I would have predicted a 6 dB gain, so you're right on target. However, keep in mind that absolute SPL gain isn't the only thing we're going for.



> This is a temporary set up ... I have to use REW to measure the response to decide if I keep it or not.
> Somethimes we like to experiment things, Right :bigsmile::bigsmile:


I agree that it's cool to experiment. But I think I'm with Kal on this one. Even if REW measures well or the same, I think overall sound will be better with only the one pair of speakers. There's just too much going on with the combining of the speakers. But if you like it, go for it!


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## Sonnie (Apr 11, 2006)

I wonder how it would be to stack them on top of each other with the top speaker turned upside down where both tweeters are closer together... :huh:


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## Scuba Diver (Sep 28, 2007)

I tried it. I have 4 surrounds and 2 centers. This is not the best test setup as the 2 centers are not the same brand and are obviously not matched. One center above and one below. One set of speakers are about level with the lower center and the second set is about level with the top center. I am not intrested in numbers just sound for now. 
I can honestly say it placed the center sound completely dead center of the screen. My wife thinks I am nuts. She sat down to listen I told her to close her eyes. First, I moved the single center to several positions until I found the spot she said is sounded best. Without telling her, I turned on the top center and she instantly began to smile. She said "It sounds better.... so are you trying to get my permission to spend more money" 

Of course there is a good chance that the center speaker I own may not be right for this room. All I know is it sounds better to me and my wife with more than one speaker. 

I will experiment more later. I would never have tried this if it wasn't for the fact that I have always been able to point out the center speaker with my eyes closed. At least until now. I honestly can not tell where the sound is coming from.


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## salvasol (Oct 31, 2006)

> ... At least until now. I honestly can not tell where the sound is coming from.


I know .... from the speaker :rofl2::rofl2::rofl2::surrender::whistling:


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## Prof. (Oct 20, 2006)

jackfish said:


> I would stack them vertically in a WTTW configuration and see if there is an improvement, especially in the midrange. I have Large Advents so stacked and the sound is incredible.


That sounds like a good idea...definitely worth trying :T


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## Prof. (Oct 20, 2006)

Otto said:


> Most likely because they will be run in parallel, thereby presenting a difficult load to your receiver/amp. Depending on the receiver/amp, this may or may not present a problem. If it's a problem, it will most likely be present at higher volumes, as that's when the most current will be demanded from the amplifier.


Yeah...That's pretty much it..
I think I was told that it reduces the dampening ability of the receiver..


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## Prof. (Oct 20, 2006)

Scuba Diver said:


> I tried it. I have 4 surrounds and 2 centers. This is not the best test setup as the 2 centers are not the same brand and are obviously not matched. One center above and one below. One set of speakers are about level with the lower center and the second set is about level with the top center. I am not intrested in numbers just sound for now.
> I can honestly say it placed the center sound completely dead center of the screen. My wife thinks I am nuts. She sat down to listen I told her to close her eyes. First, I moved the single center to several positions until I found the spot she said is sounded best. Without telling her, I turned on the top center and she instantly began to smile. She said "It sounds better...


An interesting configuration...Are you using A+B on the receiver, or are the 2 sets wired in parallel?


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## Prof. (Oct 20, 2006)

salvasol said:


> Somethimes we like to experiment things, Right :bigsmile::bigsmile:


Thinking outside the square can sometimes yeild surprising results..:T


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## Kal Rubinson (Aug 3, 2006)

Prof. said:


> Thinking outside the square can sometimes yeild surprising results..:T


When exhorted to "think outside the box" by a management consultant, our chairman of Psychiatry responded by saying that people who do are usually kept on medication.:rofl2:

Kal


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## Scuba Diver (Sep 28, 2007)

They are wired in parallel. I would have tried A&B but I did not have enough speaker wire for both speakers to reach the system. I will likely try that next. 

The top speaker was installed upside down so the tweeter is at the lowest point of the speaker, the lower speaker is right side up so the tweeter is at the top. this seams to mend the two speakers into one even though there is a gap of about 2 to 3 feet between them. However, moving the lower speakers to far to the left or to far to the right really screws with the sound quality. But when placed just right the two speakers become invisible and the sound seems to come from out of now where. I mean if you look the speaker the sound does not appear to be coming from it. 

Maybe a meter would tell a differnt story. But it sure has my ears, my wifes ears, and now my wifes girl friends ears fooled.


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## Prof. (Oct 20, 2006)

I tried this upside down configuration..WTTW..with my two lower centre speakers last night, stacking them on top of each other, and was surprised at the results..
I still had the good centre of screen voice imaging, with a good spread across the screen, but the voices were projected more forward than previously..
Also loud explosions had more impact with a sharper crack as the explosion began..
Definitely an improvement and I'll be keeping them setup this way..


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## htnut12 (Mar 5, 2007)

I use two front left and right speakers my placement options are nil with WAF so I have to improvise. The mains are placed a bit too far apart and fire into the room at an angle toward my listening postion. The augmenting speakers point towards the center of the back wall. Essentially the side of the augmenting speaker is placed along the back of the main speaker. Works great for me and my lovely wife. 

The center is augmented with a separate subwoofer placed behind it. No separate power amp in the sub, just a ported box with a sub. 

The downside, forget about doing this with a Denon receiver. The Denon is about useless for reference levels in home theater, even with the very efficient Klipsch speakers. It is a great preamp tho. 2307CI. My old HK AVR500 had no problem driving a pair of Klipsches per channel. That now serves as the guest bedroom 5.1 audio setup.

An ADCOM amp just gathering dust put back into service and all is now fine. 

When I get all my subwoofers installed I may use some of my pro amps to advantage with the fronts and center.


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## doubeleive (Oct 31, 2007)

I Use Dual Center Speakers From The Main Receiver, I Like To Have A Wide Center Channel As Many Movies Have The Audio Coming Out The Center Channel, I Have A 73" Tv So Plenty Of Room For Two Centers, I Also Like Them To Have Good High Output So I Use Two Athena Ws-60 Turned Sideways (they Are Designed To Go Either Way), I Used To Use Dual Front Speakers But Not Anymore, I Have The Centers Under The Tv On The Midle Shelf Of The Stand, Used To Have Them On Top Of My Old Tv But The Tv's Are Super Thin Now So No Room On The Top. Works Pretty Well.


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## Kal Rubinson (Aug 3, 2006)

doubeleive said:


> I Use Dual Center Speakers From The Main Receiver, I Like To Have A Wide Center Channel ...................


Of course, using two centers to achieve this is counter-productive. :scratch:


Kal


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## eugovector (Sep 4, 2006)

Kal,

Can you expand upon this? I doubt doubt that the interaction between two speaker can have some cancellation, but if you could fill us in on more of the science behind this, or perhaps link an article, that would be great.

Thanks,

Marshall


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## Kal Rubinson (Aug 3, 2006)

eugovector said:


> Kal,
> 
> Can you expand upon this? I doubt doubt that the interaction between two speaker can have some cancellation, but if you could fill us in on more of the science behind this, or perhaps link an article, that would be great.
> 
> ...


Off hand, no. I have explained the issue here and on several other forums (especially AVSforum) many, many times and even dealt with it in my column at one time. However, I would have to start Googling to find any of them, so I will have to leave it to you if you are so motivated.

Basically, it has to do with the wave interaction between any two sources (re)producing the same signals. The interaction corrupts in the plane of their displacement and is relatively benign at right angle to that plane.

Kal


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## htnut12 (Mar 5, 2007)

Move your head a few mm or inches depending on the frequencies involved and you can get reinforcement or cancellation with your two ears. I think sometimes way too much is made of minutia.


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## Kal Rubinson (Aug 3, 2006)

htnut12 said:


> Move your head a few mm or inches depending on the frequencies involved and you can get reinforcement or cancellation with your two ears. I think sometimes way too much is made of minutia.


Those changes can be due to many things, some of which are avoidable (such as speaker orientation and placement) and some are less tractable (such as boundary reflections at low frequencies). It also depends on how and to what you listen. 

Kal


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