Currently I have the only Tzar 90 in the world.... so BKK Kid is of little help.
That said, the Tzar 90 is a beuty.
No teeth jarring bass, very smooth no shocking highs that make you think.... "How did that happen..."
Over all a very mellow clean response. My personal pair of Tzar 350 went to Japan for some "classified" activity. So I built myself a pair of Tzar 90s, and I must say I do like them... I like them a lot.
I'm working on getting a package ready for the World Tour so more news about the Tzars will be out and about.
BTW, our bench test results of the Tzar 90 does not show a bass boost, but the Knowles results does, and this I would imagine, is due to the testing conditions being different. I wanted to "throw" that out there in case some one armchair expert tests the Tzar 90 and decides I am being decietful.
So it's a significant difference from the 3.Ai sound?