So let’s consider another option…..say a 2” mid compression driver that can load down to 500hz and play up to 8.5k or so……not a hard task. But what to do about the top octaves? Has anyone considered a surrounding multiple tweeter approach?…….something like say the Dayton ND20fb?……4 units flush mounted in the throat very close to the mid exit? 4 of these little guys in series parallel should be a good efficiency match to a mid compression driver.
Two problems immediately come to mind.
First is the same problem discussed when using the ND20fb in a line array for VHF....the c2c spacing is 1.5 inches best. Too far apart for 1/4 WL summations.
Also, there is their distance apart inside the horn, across from each other to consider, that adds further separation.
MEH's are built around the idea of staying within 1/4 WL summations from all contributing ports.
Second, since the ND20fb's would need to be crammed together as tightly as possible towards the apex towards the compression driver to try to reduce the bad c2c ju-ju, i think the ports have the ability to create a level of increased horn disturbance with the CD output.
All in all, I'd say the idea is a backwards step....VHF needs to come from the pinnacle of the apex.
First is the same problem discussed when using the ND20fb in a line array for VHF....the c2c spacing is 1.5 inches best. Too far apart for 1/4 WL summations.
Also, there is their distance apart inside the horn, across from each other to consider, that adds further separation.
MEH's are built around the idea of staying within 1/4 WL summations from all contributing ports.
Second, since the ND20fb's would need to be crammed together as tightly as possible towards the apex towards the compression driver to try to reduce the bad c2c ju-ju, i think the ports have the ability to create a level of increased horn disturbance with the CD output.
All in all, I'd say the idea is a backwards step....VHF needs to come from the pinnacle of the apex.
Then you better use a coax compression driver like the B&C DCX464 and only do the woofers from the side i think.
Those concerns came to mind too.......IF we were considering a conventional tweeter application. But looking at this from a 'super tweeter' application say crossing in to the 2" CD at 10k, i wonder if really broad off axis HF might be achieved if all 4 tweeters were focused to an apex in front of the throat......or at least before the mouth. I'd submit that a symmetrical horn would have to be used though........square 90x90 or similar
What you're proposing would be tricky, if not questionable.
Have you seen the work put into the B&O tweeter reflector that PatrickBateman has analysed? or the effort Tom Danley went to to combine multiple tweeters into one apex?
Have you seen the work put into the B&O tweeter reflector that PatrickBateman has analysed? or the effort Tom Danley went to to combine multiple tweeters into one apex?
Not a hard task if the conical horn is under ~15degree dispersion.
If 90x90 degrees, more like 1kHz loading.
Four would be at best ~96dB sensitivity, ~15dB less than a decent 2" exit compression driver on a horn, before considering the horrible peaks and dips in response caused by sticking them in a horn throat..
The individual sources being more than a full wavelength apart at 8.5kHz creates lots of comb filtering, and a throat that won't work for a horn.
I'd second Mark's opinion that the idea is a backwards step, and further that the step is off a cliff 😉
Art
Art did a better job of describing what I was trying to say 😉
I'd suggest studying line array math, and the methods of combining multiple VHF drivers in prosound boxes.
I think the only time you will ever see much physical separation of VHF drivers, is for specific beam steering goals....for focus to a tightly defined spot