I am not sure how much one can improve over the "ear test" when considered against measured responses to changes in azimuth.
Some time ago, I joined a "consortium" of three other Gonners who group-purchased a Wally Azimuth Tool. I used it on a Graham 2.2 which I had already set by ear and it was damn near spot on, well within the range of what Wally suggests. I fined-tuned it until both sides were perfect, within the error of measurement, and did not tell a difference. Then, I fiddle-farted with three other arms, first setting them by eye and ear, then using the Wally Azimuth Tool. In each case, the eye/ear setting was within the "prescribed range" and tweaking things "better" were not audibly different, at least not to me. So, I concluded that the tool was not NECESSARY, but it might be convenient - if you consider unhooking all of your speaker connections, hooking up the Wally, running the tests, and putting everything back together convenient.
All that said, if one adjusts the azimuth where you KNOW it is wrong, and then re-adjust by eye and ear, there is a WORLD of difference in sound. I also know that if you can easily adjust the azimuth of your arm, it is a luxury. Unfortunately, some of the arms where azimuth is easily adjustable have other issues. It is a pain in the ass having to use shims, and they have their own drawbacks, but sometimes it cannot be avoided.
Some time ago, I joined a "consortium" of three other Gonners who group-purchased a Wally Azimuth Tool. I used it on a Graham 2.2 which I had already set by ear and it was damn near spot on, well within the range of what Wally suggests. I fined-tuned it until both sides were perfect, within the error of measurement, and did not tell a difference. Then, I fiddle-farted with three other arms, first setting them by eye and ear, then using the Wally Azimuth Tool. In each case, the eye/ear setting was within the "prescribed range" and tweaking things "better" were not audibly different, at least not to me. So, I concluded that the tool was not NECESSARY, but it might be convenient - if you consider unhooking all of your speaker connections, hooking up the Wally, running the tests, and putting everything back together convenient.
All that said, if one adjusts the azimuth where you KNOW it is wrong, and then re-adjust by eye and ear, there is a WORLD of difference in sound. I also know that if you can easily adjust the azimuth of your arm, it is a luxury. Unfortunately, some of the arms where azimuth is easily adjustable have other issues. It is a pain in the ass having to use shims, and they have their own drawbacks, but sometimes it cannot be avoided.