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 Post subject: Channel separation
PostPosted: 14 Jan 2021, 21:20 
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Joined: 04 Jun 2008, 20:59
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Location: Arizona, USA
Hi Folks, I believe I have encountered something that I never expected. I did a bit of moving of stuff and shifted one speaker about a foot further to one side than before to improve balance. Before the change both were next to the fireplace. Now it is against the wall. The other one obviously can't move. The arrangement makes the center correct for my listening position. The balance was nearly 3 db off where they were and the listening position could not really be moved. Unfortunately it seems as if they are now just a little too far apart as the center sounds seem recessed. BTW my electrostatics are temporarily not in use. Ugh, fix one problem and create another. I figure I will have to add a "blend" control to the system to mix the channels slightly. Anyone else run into this problem?

Good listening
Bruce
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 Post subject: Re: Channel separation
PostPosted: 15 Jan 2021, 13:48 
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Joined: 01 Jun 2013, 09:05
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Hi,

My experience with this is you have changed your speakers.
The power supply in the amp is tuned to the other speakers, sounds nuts I know.
The frequency response or dynamics of the speakers is different.
You now have a hole in the sound stage assuming the speakers are not out of phase.
It won't show on a scope because the problem is the interaction with the system and the speakers.
If you now have an imbalance and you didn't before either the room acoustics are effecting one side more than the other.
Or the ability of the amp to drive the speakers in the dynamic range required to give you the centre focus is now not adequate.
If you change the ESR of the power supply you should be able to centre the image but at a cost that now your other speakers will seem to sound different. An example of synergy of components.
You might be able to correct it with changing the frequency response.
This is assuming you haven't run these speakers before with no problems, as long as you didn't "tune" the system to sound better with the other speakers and something is now different with the system.

In theory if the power transfer to each speaker is the same and frequency response is the same the image should be centred.
But if the HF has changed the centre will not focus.
This is the problem with what sounds good and what images well may not be the same.

This idea that everything has a flat frequency response is great in theory, but the components are not flat based upon power requirements to drive at different frequencies.

So in a nut shell its the same as an amp not being able to drive one speaker when it can drive another.

Just my thoughts.

Regards
M. Gregg

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 Post subject: Re: Channel separation
PostPosted: 15 Jan 2021, 14:11 
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one other thought,

Are the speakers multi way, you don't have damaged tweeter on one side?

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M. Gregg

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 Post subject: Re: Channel separation
PostPosted: 15 Jan 2021, 20:47 
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Hi, Thanks for the thoughts. The issue is simply that the speakers are slightly directional and the listening position a little too close. It is really not possible to change the position. So when I moved the one further to one side to get a physically centered arrangement, it made the separation too great to maintain a solid center image. I found the solution in a piece of gear I was already using. (one should always read and understand all the features of gear you already have) I have a Behringer DEQ2496 providing a bit of room correction already. It turns out that it has a stereo width control feature. Using that control you can change a stereo input to mono to well past the actual input width. You can also shift the center from left to right over a wide angle. All I had to do was drop the stereo image from 1.0 to 0.8 and everything just dropped into focus like it should.

The speakers are indeed two way and completely functional as are the amps and crossovers (I bi-amp). What this does demonstrate is how influential the geometry of the room is to the quality of the sound reproduction. I am quite aware of this as the alternate speakers (Martin Logan ESLs) are extremely sensitive to placement. You can make the sound go from glorious to crap with movements as little as 6 inches. Side to side, front to back and in between all matter extremely. The speakers in use now are an upgraded variation of Altec Lansing "Magnificents" using Great Plains Audio (the source of Altec stuff now) 30 cm alnico woofers and Radian drivers on Seos 30cm horns. They are quite excellent and really smooth in response. The problem is that I have very limited places I can put their 250 pound 7.5 cubic foot cabinets. The actual listening position is near the edge of the direct radiation pattern. I could angle one of them but not the other because of the brick fireplace. They really ought to be a huge room. That is pretty much what they were designed for. They are a downsized version of the Voice of the Theater line made for smaller (yeah right) venues. I figure a 100 seat auditorium would be proper.

As a thought I highly recommend both the DEQ2496 and the companion CX3400 electronic crossover. Both while digital, do not in any way I can tell alter the sound. I generally shy away from putting solid state gear in my system, but these guys work. The DEQ is extremely flexible and can do lots of things I don't need. The automatic room correction feature can be handy if you only let it make small changes. I actually found manual corrections more to my liking after it decided where the problems were. The CX is also quite good. It allows for 2 or 3 way (and subs) crossovers and is extremely flexible in the settings. I like it because it has 24db / octave crossovers that are phase matched. For what ever reason my ears (not the best in the world for sure) are very sensitive to anomalies in crossovers. Phase shift and slope changes bug the heck out of me. Neither device is particularly costly and I recommend them to anyone who has a problematic system.

Good listening
Bruce

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