Tailoring tweeter output

I see you've spent alot of time optimizing your set-up positioning. Covering the tweeter with some material in addition to the grill might work, but there will probably always be a trade-off. You might try less toe-in and move the speakers closer together to compensate. Another option is to try some different cables.

The Ribbon tweeter has very wide dispersion so toe change will not work. The 3-5Khz region will drop before attenuation of the tweeter.

I am adverse to cable tuning to decreased 8-12khz output. Any cable that accomplish this would limits bandwidth.

After looking at pictures of your system I see the problem.
You are set up on the short wall. Your speakers are too close to the side walls.
Can you arrange your room so your system is on the long wall. The sound will be much more pleasing.
The room is a complex part of the system.

I hav tried the long wall setup. It is the same with much more bass issues.

I have also moved the speakers 3' from side wall and this does not change much. The direct sound of the tweeters are measuring a little too hot, this is done by setting gating time low to minimize the side wall reflection.

The problem with acoustic attenuation of your tweeter's output is that any material absorptive enough to make a significant differnce down at the bottom end of your tweeter's range is going to be overly absorptive in the top octave.

Assuming were talking about the Sarastros, I would consider experimenting with maybe one inch thick open-cell foam along either side of the tweeter, cut so that the sides are V-shaped, sort of like the faceplate's angle around the tweeter diaphragm. The idea is to allow the tweeter to output unimpeded across a reasonably wide arc (maybe 90 degrees or so), and then attenuate its output beyond that arc. We want the foam to be thick enough that it will effectively attenuate energy at the lower end of the tweeter's range. I really don't know if this will work or not, and several tries would probably be necessary to fine-tune if the initial try is promising, but I think this has a better chance of making a net improvement than placing absorptive material in front of the tweeter.

Duke
dealer/manufacturer