Adding 2nd Center Speaker?

dkg999

I've read a lot of discussion on this forum and others on the pros/cons of adding a second center channel speaker. I've had times when the soft-spoken dialogue in movies tends to get overpowered by my front mains or is hard to hear. I picked up an open-box CSi5 at CC for $179 this weekend and added it to my bedroom HT freeing up the CSi30 I had in that set-up. I then decided to experiment by adding the CSi30 to my main HT set-up, positioned about 1 foot above the TV (probably about 6 1/2 foot total above the floor) and slightly pointed downward towards the back of the room. I used the speaker output of my HTR-5790 to run it, while the CSi40 is running off of an Outlaw M200. What a difference! It really opened up the center channel presence in the room and added real clarity to low-level dialogue. I'm not seeing some of the concerns with sound-wave cancellation, etc. that others have mentioned. Maybe I'm missing something, but I'm not sure why others have said this is not a good idea?

ohskigod

the only issue i can see with your set up is the fact that it is 2 different centers, i.e. 2 different sounds. but if you like the sound, roll with it if you see an improvement. i use a pair of speakers (monitor 5) as the center channel, driven by 150 wpc each speaker. no probs with dialogue in my set up (had probems with dialogue in the past as you have mentioned.

dkg999

The CSi40 and CSi30 are from the same series, and as I understand it, and from looking at them, they have the same tweeter. The CSi40 does have bigger mid-range/woofers. From what I understand these two speakers should be timbre matched. Having the CSi40 on the bottom seems to work the best, as it has the slightly deeper sound and is also slightly higher in SPL. You really are not able to isolate the sound coming from each speaker.

ohskigod

ooops, your right, they should be timbre matched. i thought you had the CSi 30 and CSi5 together, they would not be timbre matched. might want to give the CSi5 a whirl on your main rig, see how it alone compares to the CSi30 and CSi40 doing joint duty. supposedly the new vifa tweeters are supposed to sound a bit better than the old RTi (CSi) line (i.e. your CSi30 and 40).

Larry Chanin

Originally posted by dkg999
I'm not seeing some of the concerns with sound-wave cancellation, etc. that others have mentioned. Maybe I'm missing something, but I'm not sure why others have said this is not a good idea?

Hi DKG,

I've also recently started experimenting with dual centers and have also been pleased with the results.

However, getting back to your question I believe the concerns center (pardon the pun) around comb filtering. Comb filtering results when there is a delay between two identical signals reaching the listerner. These delays don't just cause cancellations, they cause both reinforcement and cancellation of the signal depending on the amount of the delay. These changes to the original signal are called Comb Filtering Distortion.

With horizontally spaced center speakers people sitting off axis will always experience a delay because the distance to the two center speakers is different. With vertically stacked center channel speakers it is possible to locate the primary listening position equidistant from both speakers so there is no delay. In addition, listeners sitting off axis will still be equidistant from both center channel speakers therefore they shouldn't be effected by comb filtering distortion.

An other problem with horizontally spaced center channel speakers is that listeners sitting off axis will not hear the sounds coming from the correct location. For example, suppose you are watching a movie and the actor is centered on the screen. The correct location for the actor's dialog would be in the center on the soundstage. A listener sitting on axis would hear the the sound coming from the center of the soundstage because the two speakers would be producing a centered phantom sonic image. However, someone sitting off axis would hear the sounds coming from the closer center speaker. Since the speaker is not centered the listener will not hear the sound coming from the correct location. If the speakers are widely spaced this off-axis discrepency could be significant.

This problem doesn't occur for vertically stacked center channel speakers that are centered above and below a display. The phantom sonic image will always be centered regardless of where the listeners are seated in the room.

Well, I'm just responding to your question under which circumstances dual centers might not be a good idea. However, if you're enjoying yourself all this theory really doesn't matter anyhow does it?

Larry

dkg999

I did try the CSi5 by itself, and it is a little better than the CSi40 by itself, but then I get into a timbre match conflict with my RTi70 mains. I could hear a difference in the CSi5 high-end and the RTi70's. Also, the CSi40/CSi30 pairing was producing much more center channel presence in the room. I'm in an apt. right now, so presence at low volumes is important! That's why I run two subs at low volume. The downstairs neighbors were gone tonight, and I had the new Punisher DVD, so I did crank it up some. I really like the CSi40/CSi30 pairing, it seems to work! I wish I could find another single channel amp. to use for the CSi30, around 60 to 80 wpc, with a gain control so I could experiment a little more with SPL on the two. My Outlaw M200 doesn't have a gain control, and if I use the receiver it adjusts both the pre-out and the speaker level. If I didn't like my RTi70's so much for HT, I would consider replacing them with an Rti8 or Rti10 to match the CSi5! To my ears, the RTi70's are a little smoother and hit a little harder on the mid-range and low-end than the RTi8's, and the RTi10's seem like a little overkill. I don't use my HT for music, that's what my SDA's are for!

Larry Chanin

Originally posted by dkg999
I don't use my HT for music, that's what my SDA's are for!

Hi DKG,

I can appreciate the logic of having two setups, one for home theater and one for two-channel music. However, it's highly likely that using your SDA's for home theater would greatly improve your home theater's performance. I'm using my SDA-1C's as my mains and dual SDA CRS+ as centers in a dedicated home theater along with other Polk Audio speakers. The result is wonderful for both movies and multi-channel music.

Larry

dkg999

Hi Larry - that's the funny thing about the SDA's, I originally tried them as my mains for HT, and I wasn't real impressed! It must be my ears, because I know a lot of people on this forum really like the SDA's for HT. I picked up my RTi70's for $99 each at a CC open box deal, and based on all the praise for them on this forum I couldn't pass them up. To my ears, and I don't claim to be an audiophile or expert on this stuff, the RTi70's sound much better in the HT role. The SDA's to me are just a litte too sweet and smooth sounding for HT use.

I appreciated your detailed explanation of some of the issues with dual center channel speakers and the placement - vertical versus horizontal. I understood what you were explaining! I did move around my room last night, and could at certain spots just barely hear some difference in timing from the two centers, but it wasn't bad at all. The CSi30 is just enough brighter in sound than the CSi40 that it really seems to mimick what we normally hear from a stacked tower speaker with the tweeter on top. The brightness difference could also be caused by the CSi40 being driven by the Outlaw M200 amp, and the CSi30 being driven by the internal amp. on my Yamaha HTR-5790. Aside from all the theory, you're right, it comes down to how it sounds, and I like what I am hearing.