Tailoring tweeter output

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

RAAL uses 2 foam blocks to adjust radiation pattern these reduce output slightly. Maybe sim will work. But better to just use a attenuator on ribbon if its to hot near-field. Or replace loudspeaker many ribbon loudspeakers do run tweeters hot since at distance they reduce in level. I use designs with user adjustment so can be used near or normal set ups. Fostex r100t is very good for attenuation.

I understand it's an old recording engineer's trick to drape a piece of toilet paper over the tweeter to tame the high frequencies. I've tried this on a few shrill recordings, and it works pretty well. It does, though, tend to reduce not just the highs in the brightness region but also in the region above that, which adds "air" to the sound. You might give it a try. It's almost free and it's easily reversible.

If your speakers are bi-wirable, you could also insert a resistor between the bass and treble inputs.
-Bob

How far apart are the speakers?

It doesn't make sense that you can move your system from the short wall to the long wall with the same results. The long wall should give you more options for speaker placement and the ability to increase off axis listening angles.
The fact that the bass was a problem on the long wall was most likely midbass which is easily cured with Tube Trap products along with Tube Trap products for the wall behind the listening position.
I know there are other room treatment products on the market, but it is my opinion ASC makes the best room treatment.
I see you have analized your room to death, but there is nothing like trial and error.
Sometimes we have to take two steps back because we went too far. Room treatment and cables alone are extremely powerful.
This is all a delicate balance and sometimes when we think we need less of one thing we actually need more of something else.