Hello cdc,
I doubt the Enacom will cure your problem. Brightness is a stacking of excess energy at a specific frequency. This energy comes from added noise to your system in that range. I doubt Jim Thiel would let a speaker out of his factory like this. I'm sure they are spectrally fine top to bottom. This brightness, I believe is being caused by something down stream. If your components are of a neutral nature, I would look at your cabling and power. Because this is brightness, I have to believe you are picking up some RFI in your cabling and it is being added to the signal and once in you can never get out without filtering and this noise is being reproduced at the speakers. I use the Enacom filters on my 4.5 Von Schweikert's which I think have a lot more zing than the Thiels. The Enacom is a very subtle but effective enhancement. They do tend to relieve some high frequency noise which leads to more sound stage and greater low level detail. They take about 50 hours to break in and if you remove them from the circuit they will have to be acclimated again about 50 hours. Installing them in the system you won't notice much immediately but after a couple of days of playing you will notice a cleaner presentation. What they do basically is filter back force energy created by your speaker returning to the rest position. Under signal the speaker will extend out, when speaker retracts it creates a back force engery which is fed back to your amplifier and here is where all hell breaks loose. This is only simplification but I really don't think they will help your situation. I have a pair I'm not using, if you would like to try them, they are not for sale, but I'll gladly loan them to you. Hell, If Albert could loan out his Domanus, I'll take a shot with these. That's what makes this site different from all other sites, the people. How this helps.
Thanks for listening,
Dave & Gloria
davehrab
P.s. If Sean, AlbertP. or Bob-B is hanging around this morning and reads this, I would appreciate their input also.