I couldn’t pinpoint what was bothering my ears listening to M945 then. I am sure I wasn’t the only one at the RMAF had the same impression about the sound. It had frequency extension but lacking a richer tone. I almost sold mine until I read about the after market AU90 high frequency transformer mod that addressed the mid low frequency suck-out. And yet SL received glowing reviews until this issue was permanently resolved with updated high frequency transformers.