Originally Posted by
toddalin
Further testing indicates that we can reduce that dropout above 4KHz by angling the plates outwards a bit more. Testing also shows that the JBL slant plate placed over the tweeter has similar effect, except that (interestingly) it doesn't provide as much boost between 2.5-4kHz, nor quite as much cut up around 10K. The JBL plates frequency response more closely resembles the tweeters without the plates. Also, the JBL plates are about 1 dBA louder than my plates, perhaps due to bleed through, and, the thinner plates block less of the opening. The dropout above 4KHz is still there, but not quite as much. Angling my plates out a bit brings the the volume to the JBL plates in that region, but retains the benefit of the increased bass and flattened highs.
I also think that perhaps with the JBL plates, the plates are half as thick so more sound actually goes through them, rather than around them, relative to my fatter plates and some of this "direct" path is getting through making the JBL plates a bit louder and more of the natural tweeter-like (hence turning my plates out a bit better simulates this "bleed through").
I've done another set of revised angles to hold the plates in CAD and need to cut them out and see the difference.