Anyone using two center channels?

kingtut

A friend of mine is asking for an opinion regarding using two center channels because his Polk CSi400 is not producing enough clarity for vocals in movies. He already cabribrated the speakers w/the RadShack sound meter; a lot of times, the converstion is intelligible at regular volume. After calibration, the center channel is at 0, but he still cannot hear the actors' conversation during the movies. He practically has to manually adjust the volume channel to +10 to hear the conversation. Is any one using two center channels? If you're using two center channels, what's your opinion, pros vs. cons?

Dennis Gardner

His problem lies in the setup of his center. Have him get an Avia or Video Essentials setup disc. This will help him with phase problems, etc.

2 center channel speakers creates more problems than it solves unless alot of tweaking is involved. Filter combing of combining 2 tweeters with 1 signal create issues.

It can be done, but isn't the easy fix you are looking for.

kingtut

I already lent him my Sound and Vision calibration dvd, and he already checked the phase already. He was asking me whether getting an external amp for a 2nd center channel via pre-out from his receiver, and using his receiver to drive the CSI400 will solve his problem.

Dennis, can you elaborate on filter combing of combining 2 tweeter w/1 signal creating issues?

VR3

PLENTY of members have run multiple centers with great results. I have ran multiple centers with great results in multiple ocasions.

I recomend you use a seperate amp if you plan on doing it...

Multiple centers to me are a GREAT thing.. *ponders*

Dennis Gardner

Filter combing is a cancelation of the signals caused by identical drivers producing the same signals on the same plane. Placement of centers on exactly the same plane seem most affected by this condition.

kingtut

Trey, which amps and center channel models did you used?

unc2701

On the other hand, comb filtering is rarely noticiable in "real" rooms. Most rooms have so many reflections that the filtering effect is filled out by them. However, I'd agree that there's something wrong that needs to be addressed before he adds another center.

dkg999

I run two CSi40 center channels, one setting below my tv, slightly angled up, and one about a foot above the top of the tv, angled down towards the sitting area in the room. I split the center channel pre-out and each CSi40 is powered by an Outlaw M200 amplifier. I was having problems with center channel clarity and being able to hear the center channel in all seating positions, at low to moderate volumes. I am in an apartment, so I listen at relatively low levels. Using the two center channels has really helped with clarity and presence in the room. I use the set-up in my Yamaha receiver to balance my system, and then I do some manual adjustment. I run my center channel about +4 above all the other channels so that I have clear dialog and voices that stand out, and when the big booms come that I am not rattling the neighbors. The other option is to use the night mode on your receiver, if it has this option.

Mazeroth

Another vote to NOT go with dual centers. In my opinion, it's a shoddy fix for the problem. It creates a lot of cancellations, especially above 5000hz. If he needs to set it at +10, so be it.

VR3

I used RT5's...

my Dad used some big ol KEF bookshelfs...

I have never heard negatives effects from dual bookshelfs...

Also, when you are calibrating your setup..

You always set the left main back at -5 - get that volume... then set the center 1 db above that volume and the surrounds 2 db above that volume.

GATOR3000

I run Csi5 as my centre powered by my receiver. Have a spare Csi3. The Csi5 has 4 binding posts for Bi amping. The Csi3 has only 2 posts.

If I would like to try both centres how will I connect the Csi3 to Csi5? Can I connect the Csi3 to the bottom two binding posts of Csi5? The binding clip is on Csi5 between the 4 posts.

Thanks Gator

Dennis Gardner

Vr3MxStyler2k3 wrote:

You always set the left main back at -5 - get that volume... then set the center 1 db above that volume and the surrounds 2 db above that volume.

What the hell is that? If we didn't confuse him with different suggestions, this will surely drive him away...............

kingtut

dkg999, I already suggested the night mode/cinema EQ, and he already tried it.
Thanks to all who responded so far. Anyone else tried the two center channels?

VR3

Its calibration levels...

For instance... You want to set everything to 85db...

You set the left main to -5 and turn it up on the volume knob until you get 85db.

*The rest of the levels are done with the individual channel levels*

Then you calibrate the right main until you get 85db - same as the left main.

Then you calibrate the center... you calibrate it till you get 86db...

Then you calibrate the surrounds... you calibrate it till you get 87db...

I thought I explained it fairly well...

BIZILL

GATOR3000 wrote:

I run Csi5 as my centre powered by my receiver. Have a spare Csi3. The Csi5 has 4 binding posts for Bi amping. The Csi3 has only 2 posts.

If I would like to try both centres how will I connect the Csi3 to Csi5? Can I connect the Csi3 to the bottom two binding posts of Csi5? The binding clip is on Csi5 between the 4 posts.

Thanks Gator

don't do it. your ohm load will jump from 8 ohms to either 4 ohms run in parallel or 16 ohms run in series. your receiver probably won't handle it. someone correct me if i'm wrong.....

aaharvel

no that 16ohms statement is right on. Good way to fry your electronics and bring about clipping at anything more than moderate volume levels.

Dennis Gardner

Hey Trey, Why would you want them unbalanced?

I've never run a calibration disk that set them different. Where did this come from?

unc2701

Dennis Gardner wrote:

Hey Trey, Why would you want them unbalanced?

I've never run a calibration disk that set them different. Where did this come from?

+1 on that. They're supposed to be equal, if you want to hear it the way the engineers intended.

VR3

Just try it.

Louder surrounds are a GOOD thing.

Centers are usually harder to hear. Again - the bump... a good thing.

The 2+ db bump in the surrounds is a HIGHLY recomended thing among members here... particularly such as Dr. Spec and the works.

Again... try it.

GATOR3000

BIZILL wrote:

don't do it. your ohm load will jump from 8 ohms to either 4 ohms run in parallel or 16 ohms run in series. your receiver probably won't handle it. someone correct me if i'm wrong.....

Thanks guys. Good to know. Much appreciated.

BIZILL

most definately.

Larry Chanin

kingtut wrote:

A friend of mine is asking for an opinion regarding using two center channels because his Polk CSi400 is not producing enough clarity for vocals in movies. He already cabribrated the speakers w/the RadShack sound meter; a lot of times, the converstion is intelligible at regular volume. After calibration, the center channel is at 0, but he still cannot hear the actors' conversation during the movies. He practically has to manually adjust the volume channel to +10 to hear the conversation. Is any one using two center channels? If you're using two center channels, what's your opinion, pros vs. cons?

Hi king,

I use two vertically stacked centers with good results.

Here's a thread that discusses some of the aspects regarding comb filtering that Dennis mentions.
Adding 2nd Center Speaker?

I would like to add that having a center channel mounted high can help with intelligibility in the case of home theater arrangements with multiple rows of seating. The high mounting permits the sounds to travel unimpeded to the second row without being blocked by the first row of seats and people.

However, in echoing other's comments, I think it's likely your friend has a more fundamental problem in his setup that won't be corrected by dual centers regardless of the mounting.

With regard to Trey's comments about experimenting with the speaker level settings, sure there's nothing wrong with experimenting. However, using unconventional levels now is more likely to cause your friend additional difficulty in trying to diagnose the problem. He first needs to start out with the speaker levels set equal to pinpoint the problem. Then after he figures out what's wrong he can experiment with the levels to suit his preferences.

Larry

kingtut

Thanks for all the comments. I forgot to add that his center channel is on top of his TV. His TV is placed inside a recessed built-in nook that is to the left & front of the room, so his center channel is off-center and is closer to left front speaker. This is how the house was built (a track home). The nook is bi-furcated w/a built-in shelf, about 4-5' deep and 7' high (from the top of the shelf to the ceiling).

Dennis Gardner

kingtut wrote:

Thanks for all the comments. I forgot to add that his center channel is on top of his TV. His TV is placed inside a recessed built-in nook that is to the left & front of the room, so his center channel is off-center and is closer to left front speaker. This is how the house was built (a track home). The nook is bi-furcated w/a built-in shelf, about 4-5' deep and 7' high (from the top of the shelf to the ceiling).

Poor placement. 'Nuff said. A 10 db required boost indicates such a poor setup that multiple speakers, bigger amps,and electronic eq still may not overcome a inherently bad balance problem.

More HP from a bigger engine rarely helps if you've got flat tires.

Just my .02.

Larry Chanin

Yes, I agree with Dennis. The placement inside a structure is undoubtedly causing the problem. Sound is reverberating inside the enclosure and being defracted before it leaves the enclosure. The net result is that 1) the enclosure structure is probably resonating at it's own natural frequency and 2)multiple delayed reflections of the sound are coming of the edges of the enclosure. These reflections reach the listeners a few fractions of a second later than the direct sound, resulting in a smeared sound that is less intelligible.

The first thing your friend might try is simply placing the center speaker on top of the enclosure even though it's 7 feet high and the TV is much lower. Usually our hearing is fooled into believing the sounds are coming from the on screen action even if it is much lower. This will also permit him to diagnose the problem to make sure it's a placement issue and not an equipment/speaker problem.

If he has to keep the speaker inside the enclosure, if possible he might try stuffing any space between the speakers and the surrounding enclosure with batt fiberglass insulation to kill reverberation of sound in the enclosure.

Then he should try pulling the center channel out as far forward as possible with the grill protruding slightly from the enclosure and he might also consider fitting an MDF baffle around the speaker. These measures might reduce defraction of the sound.

Good luck.

Larry

TheReaper

Vr3MxStyler2k3 wrote:

You always set the left main back at -5 - get that volume... then set the center 1 db above that volume and the surrounds 2 db above that volume.

My suggestion, would be to start with all at the same level. Then try bumping the center, or surrounds and see how it sounds. In my settup, increasing one has the effect of some canceling of the other. Also In some surround sound mixes, the surrounds and center play off against each other. So I would shy away from bumping both the surrounds and center (bump one or the other).

Having said that, yeah my surrounds are bumped +1. And for late night low volume listening, I will frequently temporarily bump my center.

kingtut

Larry, it's a built-in recessed opening that was built by the home builder (obviously w/out any regard for a sound system) with one shelf (to put the TV on top) and no other shelf.

Skynut

I use a center chanel on the top of my set and one on each side of my set.
I have the cs1000p on the top and rt55's on the sides.
The cs1000p is powered with the receiver and the rt55's are powered with a seperate amp which gets it's signal from the pre-outs.

Originally I did this to bring a better flow to the center chanel. it provides a seamless sound that my mind hears comming from the center of the tv.

I like it. I also tend to run the left and right chanels at lower levels than the center and the surrounds at a little higher level than the center. This is just how I like it.

I would recomend your friend give it a try if he/she can do it with a seprate amp or independant power.

kingtut

Skynut, so you have three speakers for the center channels? Do you use the Y-splitter to connect the two RT55s?

Skynut

I did use a y splitter for the rt55's. It goes into the r/l inputs of the extra amp.
I think it works well but everyone has their own opnion.

Larry Chanin

kingtut wrote:

Larry, it's a built-in recessed opening that was built by the home builder (obviously w/out any regard for a sound system) with one shelf (to put the TV on top) and no other shelf.

Hi,

Perhaps I still don't have a good grasp of the configuration. Nevertheless, if the center channel speaker is tucked inside a deep recess, adding more center channel speakers in the recess, spread horizontally, and playing the same mono signal is not likely going to improve intelligliability, especially for people sitting off axis.

Your friend has already boosted the center channel level by 10 dB and that didn't solve the problem, so adding a second, level-balanced center channel speaker will only result in a 3 dB level increase. Regardless, while increasing the level of the center channel might help your friend hear dialog, it doesn't solve the basic problem of sounds reverberating and deffracting off the insides of a recess. Adding more speakers in that environment will just add more reverberation and reflections. In addition, if the level of the center channel(s) are boosted, other sounds meant to be heard from the left and right speakers will be obsured.

I take it that you or your friend are reluctant to try experimenting with stuffing the cavity between the speaker and recess with insulation?

Larry