Unstable Imaging - Causes?

Bob,

Thanks for the help. My question is, if you put one of those panels on the left, did you have to buy/build a stand for them? I'm not sure that would work in my apartment; a panel to the left of my system would make it very hard to get around inside the apartment. I suppose I could always just move the panel into place while listening, then move it when I'm done...

Thanks,

John

Couple of comments, a suggestion, but not necessarily any solutions though. 1) Your original post talked about a shift in the highs to the right. I think this is consistent with your description of your room and speaker placement. I'm a bit confused by your now referencing a drift to the left.

2) Use of a solo piano recorded and played back in stereo is not a good test for judging imaging. Usually they are multi miked and in many recordings the engineers have tried to re-create a life size piano (one that spreads over much of the stage between the speakers) and the dominant sound often is left of center, depending on where the recording mikes were placed and how they were mixed.

If you want to see what happens with high frequencies in your room get some recordings of solo instruments, typically reed instruments. They are much more capable of giving you a pin point center image to judge and hopefully balanced reproduction of room acoustics.

A CD/LP which has been of significant help to me in setting up and evaluating music (not test tones) in my rooms is "Depth of Image" by Opus 3. This was originally one of a series of LP's and is now incorporated into some CD's with additional cuts from other CD's such as Timbre. It is minimally miked, small, medium, and large sized groups and vocals of classical and jazz performed by some Sweds. It has been my touchstone for over 25 years regarding timbre and imaging. Each cut is accompanied by a description of what you should hear, and some of the instruments are very revealing of limitations/faults in your system in the high's such as a recorder and an organ but will also show what your system is doing right. A facinating exercise I think.

BTW, you haven't addressed your set up specifically, but don't forget that ceiling reflectons can be as much of a problem as side wall/floor 1st reflection points and are just as much influenced by toe in the effect of which is much overlooked. You haven't (at least I don't recall) ID'd your speakers, but assuming they are cone speakers here is a suggestion for you (one that initially appears counter intuitive) that is often used by professionals in difficult rooms.

Set your speakers up so that the axis of the speakers cross well in front of your listening chair. For example if you are listening in an equal lateral triangle with your speakers pointed straight ahead you have created a 22 1/2 degree angle. Try toeing in your speaker until you have passed your listening position 22 1/2 degrees and then gradually toe it back towards the listener position until it locks in. You will be changing (minimizing) the effect of lst reflection points on the wall, you will also be changing the effects of the reflections from the ceiling and floor. Give it a try before you spend any time or money making panels, drapes, etc. It's FREE. And you can get used to looking at cross-eyed speakers! :-)

I have just moved into a new house, and the very same system which sounded pretty good in my old house sounds pretty bad here. I called in an acoutic engineer who did frequency, phase shift, etc tests of my now current room, and advised many things. The right side of the room is almost totally glass leading to the back garden and pool. He told me that lows go through glass as though it wasn't there at all - "did you ever notice how loud a big truck going by the house can be?" Highs however, are reflected from glass. All together, all that glass can play havoc with good sound. You might try some draperies, natural(not artificial) plants, etc. to balance the sound.

“1) Your original post talked about a shift in the highs to the right. I think this is consistent with your description of your room and speaker placement. I'm a bit confused by your now referencing a drift to the left.”

I believe that originally, the azimuth was off, causing a shift to the right. I then made an adjustment which now causes things to be centered for the most part, but I’m still getting a feeling that the soundstage is more open on the left. It’s been driving me crazy because it’s hard to adjust azimuth when you haven’t isolated all the issues with room acoustics. But that’s what I’m trying to address now, using CDs which I know are balanced evenly between the channels.

“2) Use of a solo piano recorded and played back in stereo is not a good test for judging imaging. Usually they are multi miked and in many recordings the engineers have tried to re-create a life size piano (one that spreads over much of the stage between the speakers) and the dominant sound often is left of center, depending on where the recording mikes were placed and how they were mixed.”

That’s very true, and I have noticed that myself. A piano is one of the hardest things for a system to reproduce. The problem that I was noticing was simply that the reverberations of the recording venue seem to be causing the illusion of a shift. The reverberation of fthe left wall in the recording venue sounds stronger than the reverberation on the right; this makes it sound like there has been some kind of shift when notes are played louder, because there is more reverberation in the recording coming from the left.

I have done some experimentation with speak placement. I’ve tried moving them closer together, adjusting the toe in, etc. I’ve been able to get the sound to be a little bit better, but still not perfectly even. My speakers are Paradigm Studio 60 v3’s. They haven’t been as particular about placement as much as other speakers I’ve heard. I will try your suggestion and experiment with toe in even more. I’ll report back this evening with any progress. Thanks.

Stringreen: I may have to consider some drapes. I do, however, have sliding vertical blinds, which I usually leave half open so that the blinds are either perpendicular to the glass, or at an angle. I figured this may help to break up those sound waves, but it doesn’t seem like it does a whole lot.

OK, I've listened to the Stereophile Test CD 3 and have learned the my room has some major issues with acoustics. I am going to build some acoustic paneling using some 2-inch thick mineral wool, 2 layers, to create a 4-inch thick panel, measuring 2' x 4'. I will make 6 of these; one will be positioned behind the right speaker, a second one will be in a stand, just to the right of the right speaker to catch that first reflection point, two more panels along the back one, and one panel on each side back wall. Here are some pics of my listening room:

http://i166.photobucket.com/albums/u100/jsplice/listeningroom002.jpg
http://i166.photobucket.com/albums/u100/jsplice/listeningroom003.jpg
http://i166.photobucket.com/albums/u100/jsplice/listeningroom004.jpg
http://i166.photobucket.com/albums/u100/jsplice/listeningroom005.jpg
http://i166.photobucket.com/albums/u100/jsplice/listeningroom001.jpg