slot-loaded tweeters (and 2 much time on my hands...)

tajanes

With claims of 140 x 40 dispersion (i.e. the Beyma ‘s), would appear to be a good way to minimize ceiling/floor reflections and at the same time broaden the listening sweet spot. (If interested in the theory behind diffraction- it’s a bit long; https://www.youtube.com/watch?v=DU3I-h8nyhE )

So it got me thinking, could this be incorporated into a coaxial?

Selected a DaytonAudio 4in (not my fav coax, but priced for destruction…).  First thought- good project for a 3D printer, but unfortunately last time I looked- not in my toolbox.  So what can I come up with that can be trimmed to fit, with a needed dome to mirror the tweeter?  And further needed to raise approx 1/32 off the center flange to provide clearance.  Came up with using a ping-pong ball, and of all things trimmed off a ring from a chair leg floor protector I had  (surprisingly an exact fit 7/8th inch ring).  As for the ping-pong ball, cuts easily, sanded to size (sanded against fine grain sheet flat on a table top), and glued to the trim ring, and then the tweeter flange.  Also put a little glue to underneath side as an attempt to dampen the ping-pong ball a bit.

I’ve attached a few pics of the process, and a couple of frequency charts.  The first frequency chart is of the tweeter ‘as was’ - actually kind of ugly off axis (approx 15-20 degrees off axis).  The second is with the ping-pong ball slot in place.   While it does seem to help on a relative basis on one axis, measuring from the other axis rolls off the response (hoped for, expected, and a good thing) but does so in a roller-coaster response (not so good).  But heck, it’s a ping-pong ball.  

tajanes

I failed to mention, the blue lines in both charts are the off-axis scans (and a bit surprisingly, with the slot the off-axis is the higher line)

tajanes

...and after reading comments / suggestions by dcibel in another discussion (very helpful- thx), thinking the second measurment showing higher off-axis can be attributed to slightly closer mic placement...

jr@mac

It irritated my wife, but I put small pieces of tape on the floor to help me get more consistency in my measurements. I also put alignment marks on the mic stand etc. Pretty straightforward to hit a little more consistency at this point. Add a tape measure and things really start lining up.

Cool experiment!

Kornbread

The AWA generally stays downstairs and lets me get away with a lot upstairs as long as I don't make enough noise to drown out her constant Harry Potter reruns.  There is tape on the floor designating speaker and mic placement at 0, 10, 20, 35, and 45 degrees @ 1 meter.    

tajanes

thx for suggestions (and btw jr, I've got a knack for that as well, and often not even needing tape...)

jr@mac

tajanes said:

thx for suggestions (and btw jr, I've got a knack for that as well, and often not even needing tape...)

I hear that, my friend.