Have you considered the possibility that the "bright" might be from the room surfaces and/or speaker positioning?
Egglestone Andra 1 tweeter "crossover"
A friend of mine told me that my Andras 1 will sound better if I use a good quality, non-inductive resistance, of 1 ohms in serie of each tweeter. If I do that, he says that the sound will be similar of the Stax Omegas 007 earphone. I will be pleased if someblody can help me in that. Regards, Francisco.