Expertly written, you are a genius when it comes to technical listening.

Nice comparisons and great technical know how. Not sure my experiences of Solar are the same, but mine are Unis - and a lot depends on fit/tip...and source.

Thank you guys. I appreciate. 
 
@ozziecook Well, I got some infos/PMs about it and I think that universal has less prominent mid-bass presentation. The bass quantity difference probably depends on tips and insertion depth as you said. 

great review , very helpful

My pleasure mate. 

How different are UM Mentor and Solar? In particular, vocal sound.

I don't have Mentor anymore. But from what I remember, I can say that Mentor is a little thin sounding unit. Solar has more body. 

Great (detailed) review!
You must have some kinda ''bat ears'' to hear all these nuances. And besides that, I think it takes quite some writing skills to be able to put that in words like you do (I know I certainly can't) => respect!

Thank you Erik, I appreciate your comments and kind words  Everybody uses different definitions.. 

I can't wait to get my Customs and see how they compare to your impressions. Thanks for the review.

How would you compare the w500 to the solar? I found the w500 bass quantity too much, do you find the solar has a similar eq?

@PinkyPowers Hope you enjoy your Solar
 
@BenHolmes In fact both have a slight low frequency dominance, but W500's midbass sounds closer to your ears when compared to Solar. In this regard, W500 may seem to have a little bassier presentation. 

Cheers Mike. I may have to try before I buy in that case! Great review, once again. Cheers