After installing my system, I calibrated the six channels by ear. My receiver allows me to adjust from -12dB to +12dB in 1dB increments. I thought that I had it set, but after a couple weeks watching DVDs, I further tweaked a couple speakers up/down 1 dB. I redid my "ear" calibration test and would have returned the channels back to the original values if it wasn't for the fact that I thought the new tweaks sounded better.
I borrowed a friend's SPL meter this weekend. Get this - the SPL meter readings matched what my original ear calibration had determined. I did not adjust any channels to match the SPL meter as I still think my tweaks sound better.
My point? Does anyone think a $60 SPL meter is worth the cost for the one-time setup of a personal HT system?
Maybe for a professional installer, but I think that the average user is better off using their ears.