marco_gea
03-08-2019, 03:41 AM
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 (http://www.audioheritage.org/vbulletin/showthread.php?7861-2426-2445-tapered-throats) 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
After some deliberation, I decided that it would make more sense to start a new thread rather than dig up an old one (http://www.audioheritage.org/vbulletin/showthread.php?7861-2426-2445-tapered-throats) 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