Wow - 60,000 posts in 2000 pages! What an amazingly durable thread this has been since it was started back in January 2007 by Soundlvr!
The puck mic is definitely not interchangeable with the Eiffel Tower mic. One problem with the latter is that they have no markings on them - the only designation is on the box the mic comes with, which could have course been misplaced or swapped with another.
If buying used, I think it is essential to be sure that the mic accompanying the unit is the mic it was originally supplied with. Using an incompatible mic will give you unpredictable results. Personally, I would not buy a used unit that didn't come with its original mic for that reason. As you point out, you cannot even be sure, if you approach Onkyo to buy a new mic, that they themselves fully understand which mic you need. Audyssey may be more helpful to you in fact and an email to their CSR might help.
Bottom line is that the mic is a very important part of the Audyssey system. Good luck.
Static is a great enemy of electronics. The thick rug I have in my HT always creates masses of static when I walk on it in my socks. I have to be really careful to discharge myself before I touch anything sensitive or important.
Is the sub trim the only difference you noticed between the two Audyssey runs? You can expect small variations because the mic positions will often be slightly different between runs. If you moved the mic and also moved the sub, it could account for a difference of a couple of dB. Also, the mics themselves have a fairly wide tolerance of +/-2dB, so if the old mic was -2dB and the new one is +2dB, add that to the couple of dB caused by moving the sub and the mic and I guess it could add up to 4 or 5dB as you are seeing. Either way, a sub trim of -7dB is nothing to worry about.
On a general note, are your speakers designed to be used facing out like that? If not I'd suggest you toe them in so they face the MLP more. Also, is that centre speaker clear by an inch or so from the front of the AV cabinet? If it isn't you may find a good improvement in SQ by moving it so that it is, and thus eliminating the nasty reflection that the cabinet will cause if the sub is pushed back onto it by an inch or so. The R & L speakers are not centred either side of the screen. While Audyssey will compensate for that it would probably be better if they were symmetrical to start with. I realise this will mean moving the sub though and if you have done a sub crawl and found that that is the best spot for it, it may be best left there. If you haven't done a sub crawl, I’d suggest you did as it is free and doesn’t take long and can make a substantial difference to the bass quality.
Ideally the speakers will be just to the sides of the screen. If the screen is fairly small, then spaced out a little more will enhance the soundstage without divorcing the sound from the on-screen action too much. I was really commenting on the asymmetrical placing rather than the distance they are apart.
The tripod is OK but a boom mic stand is better and much easier to use. Standing the tripod on the couch isn't really the best way to take measurements. $20 will get you a satisfactory one.
If you sit too far from the screen, the additional resolution isn't so easy to see with the naked eye. Whether it's on the wall or not isn't the issue - it's the seating distance.
12 to 15 feet is a heck of a way from a 50 inch screen! The recommended seating distance from a screen is usually twice it's depth. I sit about 8 feet from my 65 inch screen and, if the room layout permitted it, I'd sit closer still.
The recommended viewing angle (SMPTE) is 30 degrees, which would equate to a maximum recommended viewing distance for a 50 inch widescreen of 6.8 feet. THX maximum viewing angle is 26 degrees, which translates to a viewing distance of 7.9 feet. The recommended THX viewing angle though is 36 degrees, which corresponds to a viewing distance of just 5.6 feet.
So to achieve the recommended viewing angles for that seating distance of 15 feet you'd need a screen 110.7 inches diagonal (SMPTE) or 134.2 inches diagonal (THX)! Your current viewing angle is just 13.8 degrees.
I suspect this is what bsoko2 was referring to in his comment above. Of course, from that viewing distance of 15 feet, you won’t need to look up much at the screen - but if you were closer to the recommended distance and the top half of the screen is even a little above eye level, you woud experience eye fatigue and probably neck and/or shoulder fatigue too.
Yes, I wasn't meaning to sound as if I was criticising your setup at all - just thought I'd run those figures for anyone who might be interested. Sitting at the recommended disstances really does enhance the movie experience, but I agree that it is not possible for everyone due to WAF, room layouts etc etc. Personally, I'd love to have a HT room big enough to sit 15 feet away from the screen! A 130 inch screen and PJ would be top of my list then!
No. Are you trying to gain match the subs or level match the subs? If the former, forget it if your subs are different specs to each other. Read these FAQ sections for advice on the proper way to set up multiple subs:
And this Pro FAQ answer for more detail on gain matching:
No - gain matching and level matching are two different things. It's explained in those links.