Hello all,
After some deliberation, I decided that it would make more sense to start a new thread rather than dig up an
old one that had a similar topic.
I hope this is OK.
So, basically, this post is to summarise the information that I painstakingly collected over the years on the internal geometries and flare rates of the "classic" JBL and (JBL-inspired) Pioneer TAD compression drivers.
The internal throats are all conical, but based on a hypothetical duct having the same length and entry / exit diameters, and assuming exponential or hyperbolic-exponential (hypex) expansion, one can calculate equivalent cut-off frequencies.
The reason that this is relevant is that for the best possible matching to a horn, one would want the horn (including throat adaptor) to have the same flare rate as the one that actually already starts within the compression driver itself.
So, here it goes:
Large-format drivers |
Throat diameter [mm] |
Throat angle [deg] |
Equiv. Fc (Exp) [Hz] |
Equiv. Fc (Hypex T=0.7) [Hz] |
Equiv. Fc (Hypex T=0.6) [Hz] |
JBL 375, 376, 2440, 2441, 2445, 2446 |
49.2 |
8 |
180 |
235 |
260 |
JBL 2450 |
49.2 |
10 |
217 |
290 |
320 |
TAD TD-4001, TD-4002 |
49.2 |
10 |
217 |
290 |
320 |
TAD TD-4003 |
39 |
8.5 |
225 |
300 |
340 |
Small-format drivers |
|
|
|
|
|
JBL 275, LE85, 2420, 2421, 2425, 2426 |
25.4 |
8 |
350 |
450 |
480 |
TAD TD-2001, TD-2002 |
25.4 |
8 |
350 |
450 |
480 |
I hope someone will find this useful! :-)
Marco