Unstable Imaging - Causes?

Well I haven't noticed the issue when listening to CDs, which is why I'm suspecting the TT setup. I will try these suggestions to see if anything helps. Maybe it could be an issue with azimuth?

Thanks

From what I've read in the manual for the MMF-5.1, adjusting the azimuth can be a pain. What is a "headshell?" Is that a particular tool for measuring azimuth? Cause I'm wondering how anyone could get it perfect without some kind of tool to tell you if it's out of adjustment...

Well thanks for the all the suggestions, but I still don't seem to have things exactly right. I tried playing with the azimuth, which seemed to help, but it is very difficult to accurately adjust on the MMF-5.1. I also tried increasing the VTF per Raul's suggestion, which didn't seem to help with the imaging. As for the mirror thing suggested by Stringring, I did try that but used the little mirror on the back of my stylus brush; I have it to a point now where to the naked eye, it looks very straight. But who knows if it's exactly correct. I also tried switching from the Bellari VP129 back to my NAD T162 preamp with built-in phono stage. The sound was much more sterile and congested, but the imaging problem seemed to be lessened. I later realized that this is probably just because it was masking the issue, because I could still faintly hear the shifts.

I've noticed that a lot of the imaging shifts also occur when trying to reproduce the room reflections of the recording venue. The unstable imaging becomes most audible when listening to room reverb and those room reflections.

Could all of this simply be the result of owning a budget turntable/tonearm/cart? I've been considering buying a test record, preferably from e-bay because new copies seem to cost a lot...

Newbee:

Yes, the frequency shift does seem to happen during higher frequencies. I think I have narrowed the problem down to TT setup, because I played with the azimuth some more yesterday and was able to improve the imaging. To the naked eye, the azimuth appeared to be good, but since the channel balance still seemed to be favoring the left, I rotated the tonearm ever so slightly in the counter-clockwise direction, which moved things a little more towards the center. While it sounds better, it still isn’t perfect. When the channel used to be REALLY bad, I did swap the RCA cables to reverse the channels, and the problem was then reversed; this is what led me to believe that it was a TT setup issue, and not a speaker placement or room reflection issue.

Tim:

Those are all good suggestions. I may try all of that just for the heck of it, because I do need to work on my room acoustics. It may make a difference, and is pretty easy to try.

I’ve noticed that the hardest instrument to reproduce evenly between the channels is the piano. It seems that if the azimuth is even slightly off, the reverberation that is heard off the side/back wall of the recording venue may sound louder than the sound coming from the actual instrument in the middle, perhaps giving the illusion that there is a channel imbalance. That’s just one of my theories.

John

Ok well I think I may have narrowed it down here after doing a lot of experimentation. I started listening to some classical piano CDs just to make a comparison on how they imaged compared to LPs. My initial suspicions were correct: the "shift" is caused by an unequal reverberation in both channels, which is favoring the left. The reverberation is heard more in the left than the right, giving the illusion of a shift. I think this may be related to my room. To the left of my setup is a wide open dining room, but the right side of my system is about 3-4 feet from a wall and sliding glass doors that lead to the back patio. It seems as though the wide open space on the left is giving the soundstage room to "breath", whereas it is more confined on the right. This is causing the soundstage to sound stronger in the left. Has anyone else experienced this problem and know how to remedy it?

Thanks

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

“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