mark1101 Posted February 3, 2005 Share Posted February 3, 2005 I have read about the "boxes" a few of you made to create a line level derived center channel. My question is this: If the derived center channel is a composite of both L&R coming from one speaker, would it be the same to have left and right speakers pushed together in the center? I.E. Use two pair of speakers (A & . Put speakers A in the corners, and speakers B together in the center. What's the difference if it comes from two speakers or one as long as it is in the center? Or am I whacked on this idea? Quote Link to comment Share on other sites More sharing options...
mark1101 Posted February 4, 2005 Author Share Posted February 4, 2005 A shameless bump. Where are all the center channel guys? I'm really wondering if you can substitute a pair of speakers (with L/R signal output) pushed closely together in the center of the L/R speakers, and achieve the same results as using a composite signal of both channels coming from a single speaker placed in the center of the L/R speakers. My guess is that there is a difference because the center is no longer a point source. But I would also guess that the differences minimize as you spread the L/R speakers apart. Has anyone tried this? Also anyone know who is building the derived center channel boxes? I'm interested in the line level type. Edit: By the way thanks for any help here. Quote Link to comment Share on other sites More sharing options...
dodger Posted February 4, 2005 Share Posted February 4, 2005 There COULD be a noticable point, depending on the information fed. Though they are together, the speakers will still have separation even if the dispersion pattern overlaps. If you are set on doing this, if you have the room, invert one sopeaker and place it atop the other. dodger Quote Link to comment Share on other sites More sharing options...
oscarsear Posted February 4, 2005 Share Posted February 4, 2005 O.K. here I go. I pondered this very ? as I read the various posts one the subject. I even inquired about using an RC 7 and biamping it.....and literally got no answer. So I looked and asked harder. This is what I learned. In the 3 channel configuration the center mono speaker needs to be in balance with the stereo speakers if it's to work. Also, this center speaker needs to minimize it's bass frequencies because bass is so pervasive. If this is not done then the set-up doesn't enhance the soundstage it will mush it up. Essentially the center mono (L+R) is an attempt to unwind the mix of the stereo recording to better replicate the original center stage performance. You want just the center stage material, not the rest of the soundstage. Using the RC7 or 2 speakers in lieu merely drags the entire sound dispersion central. You won't have stereo and you won't have 3 channel...you will have a wall of sound. Reading what I've written and I'm not even sure I've explained it well/right. Anyway I'm now in the process of getting a minibox constructed. It will be specific to my integrated amp and my speakers. It will be balanced and it will cut off most of the mono bass response. I'll report back when I've brought the system up. Quote Link to comment Share on other sites More sharing options...
dodger Posted February 4, 2005 Share Posted February 4, 2005 I could not have said the above any better. I only know of one that would detail as correctly Excellent post Oscarsear. dodger Quote Link to comment Share on other sites More sharing options...
oscarsear Posted February 4, 2005 Share Posted February 4, 2005 ....thnx...I needed that. Quote Link to comment Share on other sites More sharing options...
KT66 Posted February 4, 2005 Share Posted February 4, 2005 I've got some dope on this from PWK's Dope from Hope email me for a scan if you want it. Quote Link to comment Share on other sites More sharing options...
artto Posted February 4, 2005 Share Posted February 4, 2005 To answer Marks original question, yes you can combine two speakers placed next to each to form some sort of pseudo center channel. Will it produce the correct results? NO. In fact the combined output of the two speakers when placed so close to each other will produce substantial comb filtering, which are large lobes (or combs) in the frequency response as various frequencies acoustically cancel and reinforce each other, making for a very lumpy frequency response. Oscar mentions above that this center speaker needs to minimize it's bass frequencies because bass is so pervasive. This is wrong. The center speaker should be (ideally) a full range speaker, of equal quality and low thru-center distortion as the flanking speakers. I believe what Oscar and some others who have posted on this subject are referring to is the tendency for a combined L+R stereo signal turned mono, to make the bass seem more prominent. This has nothing to do with a center channel speaker per se. If you dont believe me, simply run a pair of stereo speakers while playing something with a heavy bass track, even a rock radio program will do. Switch the source or preamp to mono and you will notice the bass get considerably louder, even with only L & R speakers. With analog sources the effect is even more prominent because of less channel separation. And this is why you need to have a some sort of level (gain) control for the center speaker, which is typically set about -3dB lower than that of the side speakers (0 to -6dB depending on the recording, your room, speakers & listening location). Wall of sound is a good thing, not bad. Quote Link to comment Share on other sites More sharing options...
DRBILL Posted February 4, 2005 Share Posted February 4, 2005 The box supplies a signal that only includes material that is common to both L&R. That would be quite a bit different from a L&R speaker stacked in the middle. Actually, I use two speakers in the middle: Two Heresys wired in parallel and fed from the 4 ohm tap of a 20W Williamson. There is a noticable improvement in the low bass. DR BILL Quote Link to comment Share on other sites More sharing options...
sfogg Posted February 4, 2005 Share Posted February 4, 2005 "The box supplies a signal that only includes material that is common to both L&R. That would be quite a bit different from a L&R speaker stacked in the middle." No, it doesn't. The Klipsch mini-box is a passive mixer that combines everything together for the center channel. It is not doing any sort of steering to only put common material in the center. Input something into the box on just the left channel and you will get output on the L and C. You might even get some on the R due to extra crosstalk in the box. As I recall I think Klipsch said there was about 20dB of channel seperation in the mini-box between L and R. Shawn Quote Link to comment Share on other sites More sharing options...
mark1101 Posted February 4, 2005 Author Share Posted February 4, 2005 Everyone, Thanks for the responses. A variety of opinions. But I think everyone agrees that you need the mono signal whether it comes from 1 or 2 speakers. That's what I figured, and that was the piece of info I was looking for. I have experimented briefly with heresys using a center channel out on my LK-72 into a 299. But I haven't put it to it's best use yet since my systems all have "stuff" between the L/R speakers, and the setups are far from optimal or readily adjustable. I never tried the approach I was asking about (2 pairs of L/R speakers). Now, does anyone know where one can get a stand alone device that derives a center channel with RCA jacks at the line level? Basically, I just ordered a JuicyMusic Peach and a set of NosValves VRDs, and I'm preparing for a main system overhaul that includes a center channel. Quote Link to comment Share on other sites More sharing options...
DRBILL Posted February 4, 2005 Share Posted February 4, 2005 Shawn, I could have stated my case in better terms. The box emphasises material that is common in L&R signals. There will, of course be artifacts of dissimilar L&R material, but they obviously would not be as prominant as common material. This would sound quite a bit different from two center speakers reproducing L & R respectively. There is no voo-doo about the box. You can get everything you need at Radio Store for about $5 including the aluminum box. I turned out five in an afternoon for local friends. Let me know if there is interest out there and I could probably do a quick assembly line. DR BILL Quote Link to comment Share on other sites More sharing options...
Ritz Posted February 21, 2005 Share Posted February 21, 2005 Bill. I, like Mark, am interested in building one of these boxes - a passive one without amplification - but need help on the instructions of how to do so. Can you describe how and what you assemble in making the box? Sorry to be so clueless. Gerry Quote Link to comment Share on other sites More sharing options...
Mallette Posted February 21, 2005 Share Posted February 21, 2005 I derive my center channel from a Hafler device and it goes to a Cornwall. I've been jonsing for a Belle to replace it, as I find the output to be about -3db or so too little. Sometimes it is adequate, sometimes I still find something of a hole there. Part of this is that my room is about 3 feet too narrow, but I figure a little more from the center might compensate. Headscratcher... Need to make a bit of $$$ so I can build a proper room. $$$. Seems to always come down to that. Dave Quote Link to comment Share on other sites More sharing options...
Hardhead Posted February 21, 2005 Share Posted February 21, 2005 The directions (and illustrations) for constructing a derived center channel are in the Dope From Hope papers. Gil McDermott posted a link to all the Dope From Hope in the "Technical Questions" section of this forum on February 10th this year. Also, Al Klappenberger has posted instructions and pictures of his mixing box a couple of years ago. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.