Azimuth and the Fozgometer
regarding the Fieckert software; Michael Fremer has done a seminar with Dr. Feickert at RMAF the last 2 years that i have attended. he showed graphs of how this software shows how the best crosstalk position compares with the best phase angle position with azimuth. it would be a coincidence if they happened to be the same. info on Feickert software |
The Fozgometer measures crosstalk and channel levels through a filter. It's a good start but by no means is the optimum way to set azimuth. Feickert uses the transfer function to measure phase response, to which the ear is much more sensitive. Minimum phase error between channels is often in the ballpark of minimum crosstalk in terms of azimuth angles but rarely coincides. For far less than $250 you can get someone to do the full Feickert alignment service. |
Lew, Joel Durand, of Talea Tonearms, set up my Talea in my room. he used an Ella Fitzgerald mono Lp to make the dynamic adjustments to the azimuth. i can tell you that it took our 'eyeball' azimuth set-up to another level. |
Dear Mike, Did you set your azimuth using the Feickert stuff? I ask, because I have seen that done, and phase-matching is used as a criterion for the optimal setting. However, at the risk of sounding like a curmudgeon, I would point out that music (or anything besides a pure sine wave test tone) is a complex mixture of many, many frequencies, each of which will have its own phase characteristic. It would be impossible to match them all truly between R and L channels (except possibly with state of the art digital intervention, which we don't want). So we have to settle for some average setting that makes the brain most happy. Then too, there are the unpredictable vicissitudes of one's room reflections, speaker crossover, speaker drivers, etc, to alter phase again, even the phase angles for each frequency were to emerge perfectly matched from the phono stage. But I do take the point that there may be some setting which is found to be most pleasing due to its average effect on all frequencies. |
...dead on azimuth is where the phase is aligned, not gain. the image snaps in based on phase being equal in each channel.Now that you mention it Mike, this makes more sense than merely minimizing crosstalk. Reducing stereo crosstalk certainly helps a binaural listener estimate the size and direction of a mock-single sound source coming from two speakers. But the image will only "snap into focus" when phases are precisely in synch AT THE LISTENING POSITION. Given the effects of room interactions, which Fozgometer, Wally and oscilloscopes cannot hear, one could argue that final adjustment by listening is THE most accurate method for musical listening purposes. For me as for you, setting azimuth is a simple, two-stage process: 1. make the stylus look vertical by eye (resting on a mirror helps) 2. fine tune until the image snaps in (this can be done listening to music if you don't enjoy test tones) Measuring devices just over-complicate this straightforward, though vital, adjustment. Agree the Talea's on-the-fly azimuth function makes it very easy. I've played with it for visual azimuth but didn't have time to fine tune aurally during my too-brief audition of that exceptional tonearm. |
I agree with Mike, that phase is everything in azimuth adjustment -- however, from my reading of the Fozgometer instruction manual: http://www.musicalsurroundings.com/Manuals/Fosgate/FozgometerManual.pdf it only measures L or R crosstalk levels (separately of course which is good) and L vs. R cartridge output levels (balance) AS MEASURED THRU YOUR PHONO PRE. I mention that little detail here because that fact makes it important to know if your phono pre is in perfect balance first! Now, that's easy enough to find out by running JUST the left OR right tonearm lead/signal thru one and then the other channel of the phono pre and making sure the output of each side (measured thru the tape output on your preamp) is the same. The Foz can balance the signal for you internally which is nice; otherwise, if any of the cartridge, the record, and/or the phono pre are not each in perfect balance, that CAN be adjusted with the preamp's balance control, EXCEPT you'll then have to take your readings from the preamp's main outputs, not the tape outputs. Just remember, results with the Foz or any measurement device depend on/assume the L and R signal are the same strength, whether your testing is crosstalk-based or phase cancellation-based. It's recommended the Foz also be used with a test record -- one with which I am unfamiliar, so I don't know if it contains an out-of-phase mono track. The Cardas record does, and it was cut by Stan Ricker, the best in the business, so I would rely on its accuracy: i.e. that both channels are precisely cut at the same amplitude, AND that there is a minimum of left/right phase cancelling crosstalk in the grooves themselves. Both measurement techniques -- crosstalk levels or degree of phase cancellation -- will provide dependable result if set up and carried out with good experimental technique ;--) however I prefer the phase cancellation method because I feel it's more precise (i.e. the cancellation is either complete, or it's not) while the crosstalk method involves some subjective judgement (as implied in the Foz manual.) Yes, you can use an oscilloscope as your measuring device; and if you're measuring crosstalk, it's essential if you don't have a Foz. But if you have a Cardas (or other) test record with a L/R out-of-phase track, and a mono switch on your preamp, then any device (including your ears!) will do just fine ;--)) . |
the only problem with the whole 'minimal crosstalk' approach (which i have used) is that it's only close to optimal. i have found that i can eyeball azimuth typically as close as when i measure minimal crosstalk. dead on azimuth is where the phase is aligned, not gain. the image snaps in based on phase being equal in each channel. i suppose that the Fozgometer must somehow measure phase. i have the new Talea tonearm with dynamically adjustable azimuth. i know of no other arm which allows one to adjust azimuth while listening. i watched the arm designer use this to dial in azimuth and it really works. |
I agree with Doug. Someone once told me in my Shure cartridge days (when we eyeballed everything!) that unless the cartridge was obviously "tilted" ;--) it would be "just fine". So for me, everything was "just fine" for many years. John, the track I use on the Cardas record is No. 3 on Side 2. It's actually 32 concentric (independent) grooves, so you can drop the stylus into any one of them and it will provide a continuous signal of out-of-phase white noise. If you can set your preamp to "mono", you can take a signal out of one (either L or R) of the main outs starting with the main volume at minimum until you find the best meter range setting (unfortunately the tape outs on most preamps will remain in stereo even when the preamp is set to mono ;--) Then you adjust the azimuth for the lowest meter reading. If yur preamp doesn't have a mono setting, then you can put a 'Y' connector on either the main outs or the tape outs and hook the meter to the 'combined' leg of the 'Y'. |
I've regularly been able to reproduce the minimal crosstalk position (as measured by a Wally Analog shop) when adjusting by ear (and yes, the final adjustments are VERY small). The Fozgometer is faster, easier to use and less expensive than Wally's device, but unless it's more accurate it wouldn't seem to offer much value for me. It would be fun to play with, but I personally wouldn't drop $250 just for that. YMMV of course... |
damn, I have always done this by ear. Guess I need to blow $250...John, I'm surprised you weren't their first customer!! ;--)) Unfortunately (fortunately?) my SME V doesn't allow for such tweaking, so I have to rely on the skill of my cartridge maker. However, the Cardas test record has a white noise track where the L and R channels are 180 deg. out of phase to each other. If your preamp has a "mono" switch, activating it will combine the channels resulting in cancellation -- and when the azimuth is "right on", almost no sound will come out of the speakers. If you use headphones, or a digital VU or voltmeter to do the test (instead of your speakers) you will have no trouble adjusting the azimuth for maximum channel-to-channel cancellation. And you can "high five" yourself for saving $250. . |
Yet another audiophile discovers that the mirror can lie. Is that a new wrinkle? But seriously, if you paid the dough for a Triplanar or the like, you are cheating yourself if you don't also set azimuth electronically, at least initially. THEN you can fine tune by ear. Good to know tha the Foz works. |
If you have a record with left channel only tones and right channel only tones you can record these with something like Audacity and adjust azimuth until you reduce crosstalk (relative level of the "silent" vs. non-silent channel for left and right) as much as possible. Obviously a more tedious procedure than having a gizmo like the Fosgometer, especially on my SME 309 where the azimuth adjustment is achieved by twisting the replaceable headshell. |
