Unstable Imaging - Causes?

Jwglista: The MMf 5.1 as the bellari are un-familiar to me, anyway here are my thoughts about:

+++++ " The entire soundstage will sound evenly distributed until there is a part in the song with a lot of trebble (i.e. sibilance, cymbals, higher octaves of instruments, etc.) at which point the treble shifts slightly to the right. " +++++

Other than you make exactly what Newbee already posted ( on the VTF subject you could try to set-up at the upper VTF limit of your cartridge specs and obviously that the tonearm is flat leveled. ) ) is to check that the tonearm/headshell wires are connected in right way to the cartridge: red one with red cartridge pin, etc, etc, then check if the RCAs tonearm outputs coincide with those tonearm/headshell wires: red wire with right output signal, white one with left output signal, green one with right ground output, etc, etc.

Other than these could be on a cartridge out of target or something wrong on the Bellari.

Regards and enjoy the music.
Raul.

One more possibility: detach and clean all the connections in the analog portion of your system. Dirty connectors can lose conductivity in ways which vary with the frequency and amplitude of the musical signal.

That sounds like what your experiencing. We've experienced it too and cleaning our phono cable leads and phono stage inputs solved the problem.

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...

Does this high frequency shift mainly on loud levels? If so it is entirely possible that your cartridge or the combo of it and the arm is causing a mistracking which causes, for some ellusive reason I can't comprehend, some uneven and excessive highs in one channel OR a reduction in the highs in the other channel which might well cause the same effect. I think getting a test disc (at what ever cost - so long as it is of value) is a far better idea than just getting higher quality TT's, arms, and cartridges, even though I suspect that maybe where you end up.

Forgive me for being redundant, but have you ruled out speakers and speaker placement as being an issue by at least reversing cables at the phono so the distortions which now appear on the right channel will appear in the left channel if the problem is associated with your TT set up?

As suggested by Newbee, swap the tonearm cables into your preamp and see if the imaging imbalance shifts to the other channel. If it does shift, that could suggest its a hardware problem or a speaker alignment issue. If it does shift, fiddle with speaker position (toe-in or move one slightly forward or back.) If it does not shift, it could be a TT/cartridge issue, but I'd also look to possible acoustic issues in your room as suggest by Wwshull. If the latter, read on.

If one has stable/symmetrical imaging to start with, its not that hard to cause anomolies at various frequencies by introducing or changing reflective or absorbtive surfaces in the room. Walls jutting out, furniture, ceilings - all sorts of things - could be a cause of a certain range of reflected frequencies stacking up in phase with those coming directly from the speakers - sometimes called a comb filter (iirc). The result can be an over emphasis on sounds in a particular frequency range and that can cause the perception of an image shift.

You can find first reflection points by sitting in the listening position and have someone move a mirror along the side walls. Mark the spots where you see the tweeter of
a speaker in the mirror - typically there can be two spots on each side wall, one for each speaker. Lay 2-4 bath towels on top of one another and drape that over a big piece of cardboard (or something to hold the towels in place.) Towels should absorb the highs much more so than the lows. Position them to cover the reflection points marked on the walls and listen again. Ideally you'd do this on both sides of the room at the same time. Try moving the towels around the room, including behind your listening position if possible. If the area to the side of one speaker is open and the other speaker has a wall beside it, try putting the towels on the wall to match the open area on the opposite side. You should be able to modulate the imaging in this way - look for the spot where the imbalance you're hearing goes away.

Tim