Different sensitivity speakers in HT

Hi. I have Thiel CS1.5s up front and Thiel SCSs all around. The 1.5s are 86db and the SCSs are 87db. The SCSs are clearly louder than the 1.5s when I play the same thing through all the speakers. My preamp has adjustments for the center and surrounds which I've mostly gotten to my liking. I'm wondering if there is a specific formula I should be using to set the level for the different sensitivities. The preamp adjusts in 1db increments but just lowering 1db on the SCSs still keeps them too loud. Recommendations? Thanks. leo.
There is more to sensitivity ratings than one might think. While the SPL is somewhat averaged, a speaker that remains consistent across the band but has a slight (1.5 db) rise between 1 KHz and 3 KHz will sound noticeably louder than a speaker with a slight dip there and an equivalent plateau(s) somewhere else. As such, you might be hearing more of a difference in tonal balance than you are of ultimate sensitivity.

I would assume that you are using both an SPL meter and have experimented with various speaker placements ??? Speaker sensitivity and tonal balance are both GREATLY affected by placement and room acoustics. Sean
The best way is to get a Radio Shack sound pressure level meter (about $40-$60 depending on model)and a test CD with test tracks for the channels. Your preamp might also generate test tones for the different tracks which you can use instead of the test CD, I'm not really familiar with it. Then it's just a simple question of measuring the volume of the signals with the SPL meter and adjusting till they're equal with you positioned where you will be listening.

Sean, Greg, indeed I am using a Radio Shack SPL meter (the analog one). After I do the setup and get the correct readings the SCSs still sound louder. I have to lower the surround volume another notch or two before it sounds right. Sean, you mentioned placement and for some reason I didn't think of that. I have a set of Sounds Anchors stands on order for the 1.5s and that might so the trick (raising the fronts closer to the surround heights). Thanks! leo.