Someone emailed me and asked about the various midrange taps I've used in Unity horns.
I've used slots, I've used holes, I've used intricately designed phase plugs, etc
I've generally found that the formula used by Danley in the SH50 Synergy horns works well. They're located 3.5" inches (89mm) from the throat and they're 3/4" in diameters (19mm.)
There are two midrange taps per midrange, and each midrange is 5" in diameter.
These dimensions will get you "in the ballpark" and it's hard to go wrong with them.
If you want to obsess about the geometry:
As the beamwidth increases from 50 degrees, you'll need the move the midranges closer to the compression driver. This is because the main variable in the midrange taps isn't the distance from the throat, it's the distance from the left midrange to the right midrange, and the bottom midrange to the top midrange. That's what determines how high they'll play.
This is basic midrange-tweeter-midrange theory, the further apart the mids are, the more you get off-axis nulls.
The exit of the midrange taps causes a discontinuity in the horn. It's up to you to decide whether you want ONE relatively large hole in the side of the waveguide, or whether you'd prefer a long and narrow slot.
Both options have their merits:
1) a hole only causes a discontinuity at certain angles, but the hole is relatively large.
2) a slot causes discontinuities at nearly all angles, but because the slot is narrow, the wavefront barely "sees" it.
I've used slots, I've used holes, I've used intricately designed phase plugs, etc
I've generally found that the formula used by Danley in the SH50 Synergy horns works well. They're located 3.5" inches (89mm) from the throat and they're 3/4" in diameters (19mm.)
There are two midrange taps per midrange, and each midrange is 5" in diameter.
These dimensions will get you "in the ballpark" and it's hard to go wrong with them.
If you want to obsess about the geometry:
As the beamwidth increases from 50 degrees, you'll need the move the midranges closer to the compression driver. This is because the main variable in the midrange taps isn't the distance from the throat, it's the distance from the left midrange to the right midrange, and the bottom midrange to the top midrange. That's what determines how high they'll play.
This is basic midrange-tweeter-midrange theory, the further apart the mids are, the more you get off-axis nulls.
The exit of the midrange taps causes a discontinuity in the horn. It's up to you to decide whether you want ONE relatively large hole in the side of the waveguide, or whether you'd prefer a long and narrow slot.
Both options have their merits:
1) a hole only causes a discontinuity at certain angles, but the hole is relatively large.
2) a slot causes discontinuities at nearly all angles, but because the slot is narrow, the wavefront barely "sees" it.
I have a thought about using a single mid range that would cover 650hz to 1300-1500hzish... It is a 1.5" throat CD that has a 4" diaphragm but is only 5.25" in diameter. The loaded output in that band should be in the 112-114db/1w range. I was thinking if attached to an 1.5"-2" conical adapter mounted behind the proper sized port it would not interfere with HF driver and would be able to be placed very close to the apex.. Is there a reason this can't work?