Waveguides and compression driver exit angles

[a_tewinkel]

I'm considering starting a project with waveguides, after listening to erjee's El Cuerno and keyser's 2-way: Waveguide + Cardioid-like .

I think it was Dr. Geddes who mentioned a couple of times that compression drivers have a certain exit angle. I think 6 degrees was mentioned for B&C drivers.

This angle would be relevant for the coupling with the waveguide, I suspect . So is there a standard angle, or does this vary among brands? Could I combine an 18sound waveguide with a Beyma compression driver, for example?

Thanks!

[Ed LaFontaine]

In no particular order, I have done some cutting and pasting...

BMS
4550 – 14°
4552 – 24°
4554 – 26.7°
4555 - 30°

B & C
DE250 14.6°
DE10 7.7°
DE12 24°
DE400TN 20.7°
DE400 31°
DE500 17°
DE200 9.9°
DE85TN 34.5°
DE750TN 22°
DE950TN 17°

JBL
2450 10+°

Radian
950 20.3°

Celestion
CDX1-1745 20.16° total
CDX1-1730 20.16°
CDX1-1731 20.16°
CDX1-1746 7.6°

Beyma
CP750Nd – 24º
CP850Nd – 7º
CP755Nd – 12º60’
SMC65Nd – 15º
CP385Nd – 16º30’
SMC225Nd – 13º1’

Choose the CD driver first, then build the throat to match

[a_tewinkel]

Thanks!

I had planned on using a standard off the shelf waveguide. Currently I'm considering the Dayton H10RW or 18sound XT1086. So I would have to find a compression driver to match the waveguide in this case.

[erjee]

For El Cuerno I only considered Eighteensound compression drivers for the XT1086 waveguide under the assumption that the exit angle would match that of the waveguide. Eventually I chose the most expensive one, the NSD1095n, based on their published curves (measured on the XT1086 waveguide).

Based on the curves, the ND1030 could be an attractive option (81 euro):
ND1030 - HF Neodymium Driver
HN-Sound Shop für Veranstaltungstechnik, Casebau | 18 Sound ND1030 | Preiswert und günstig einkaufen

[gedlee]

ED

Did you or someone else measure those numbers? I ask because I have seen the B&C drawings (not available to the public) and the DE250 was 6 degrees (times two for your numbers I expect). Not a huge error.

There is no standard and even within a single company they vary.

[paulspencer]

Earl, I thought it was 6.5 degrees?

I have measured DE250 with calipers, but it's very difficult to get it accurate inside the exit tube, hence not a very accurate result. Easy to be out by 1 degree or more, unless you slice the whole thing in half!

[Ed LaFontaine]

Did you or someone else measure those numbers?

14.6 is a number that has it's origins somewhere else. I don't know where. I have worked with it.

I have 2) DE250's here with me. I checked the internal angle with a plug gauge. I also made a wooden taper for sanding/removing the ridges (mold marks). The taper I made has no crown. Only the ridges were removed from inside the throat.

Earl, is the throat a simple cone?

The taper I made has been passed along to another for their use with DE250's. I say the internal angle is a lot closer to 14.6 degrees than it is to 12 degrees.

My eye may need recalibration, though I'm confident I can discern to 1/2 degree. I have done surveying lay-out with a 20 second transit and attained closure. I know how to read verniers and split hairs.

[gedlee]

Yes, they are simple cones. 6, 6.5 degrees, thats not so much that it would make any difference.

[doug20]

Originally Posted by a_tewinkel

Thanks!

I had planned on using a standard off the shelf waveguide. Currently I'm considering the Dayton H10RW or 18sound XT1086. So I would have to find a compression driver to match the waveguide in this case.

Why not consider the QSC waveguide?? PE is selling those now too and so many measurements have proven it to be one of the best waveguide choices out there.

[a_tewinkel]

I've looked at it and it seems to perform well, except for a ragged top octave. It's too large, however (14" wide!). I want to couple it with a 10" driver, so about 10" is also the maximum width for the waveguide. I know a larger waveguide would be better, but I want a small speaker

Some of the Autotech waveguides look nice too, but they're rather expensive.