@AllenB I can tell there was a bunch of trial and error done to arrive at a suitable geometry to get the smoothest response and best distortion performance from the throat interface. The fact they're achieving anything significantly past 10k with a 4 inch diaphragm and at any significant amount of dispersion is pretty astonishing.
The PRV driver I'm testing (sadly, as great as it is on a shallow horn) has about 15 degrees exit angle, making it unsuitable for the A290 with current adapter. Its looking more and more like I can't find a pair of suitable drivers for my A290s. I dont have $4000 for a beat up pair of TD4001s. There are a few 3" diaphragm drivers which can do the full 400 hz to 15k + range, but not clean enough up top or loud enough downwards. I would have definitely not purchased A290 clones had I know they were so finicky on driver selection.
@kevinkr I sadly sold a pair of nice 2450s for quite little money a few months before I ordered my A290 clones. The difficulty of interfacing suitable drivers for the A290s largly wasn't yet as understood in the wider populous of large biradial horn crowd. I think you're the first guy on here who really went deep into investigating the compatability issues with other drivers on the A290s. The Radians you have should be great, but you found out the hard way they were completely unsuitable for the Yuichis.
The info shows the 416B wouldn't be considered "beamy" (less than 90degrees) below 1250Hz, where it's -6dB level would be 80 degrees.
Even as high as 1000Hz, it's beamwidth is around 110 degrees, similar to the Yuichi A-290 high frequency horn.
The woofer beamwidth really is of no concern in the 400-800Hz crossover range you may be considering.
Since you "can't assimilate" the concepts relating to beamwidth or polar response, as they relate to woofers and horns, you are probably misinterpreting something Pierre said.
The high frequency compression driver's diaphragm diameter has nothing to do with the woofer polar response.
The design of the compression driver's phase plug, it's exit diameter and the throat coupling do have an effect on it's frequency and polar response when coupled to a horn. That said, no aspect of the compression driver will have much impact on the horn's polar response in the range from 400-800 Hz.
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I really liked the 950PB on the JBL2380A horn, it was a good combination although the 1kHz problem was present there too. (I am not able to locate the measurements - believe they are on the computer I gave my wife.)
Note that the low end A-290 crossover point should not be lower than 600Hz. Not sure about the TH-4001. True also for the TD-4001 driver
Note that the low end A-290 crossover point should not be lower than 600Hz. Not sure about the TH-4001. True also for the TD-4001 driver
50,8 mm. Just a typo.
The calculation was correct , and a online taper calculator will give quick and easy results if desired.
The internal conical throat section ending at 39mm is the same angle as the adapter as shown in drawings.
AGREED!
DISAGREE WITH THIS.
I made the same kind of switch, from 1" to 2" and in my case the IMPROVEMENT was substantial.
HOWEVER, I used properly matched driver and horn from the start (JBL 2450 with Be diaphragm + Arai horn), and then replaced the horn with an even better (and larger) Yamamoto SS-300.
If you look around you might have some luck on the price. They pop up once in a while for a fair price, keep tabs on auction sites.
Paid 1300$ for the current pair of TD-4002z, a few minor scuff marks on outside. Factory sealed housings, with pristine diaphragms and excellent condition.
Yes! JBL 2450J (2" exit) with Be diaphragm is what I use, and it works flawlessly with horns designed for TAD TD-4001.
Those K&T measurements were done on an early batch of Be diaphragms which had some issues - this has been widely reported.
Sadly, there have been no other semi-official / reputable measurements since, though 🙁
Below are my own on-axis measurements of the JBL 2450J + Be diaphragm, when mounted to the Yuichi Arai A320FL horn (a "fin-less" version of the more widely known A290, with similar geometry but without the vanes):
Sadly, there have been no other semi-official / reputable measurements since, though 🙁
Below are my own on-axis measurements of the JBL 2450J + Be diaphragm, when mounted to the Yuichi Arai A320FL horn (a "fin-less" version of the more widely known A290, with similar geometry but without the vanes):
https://www.usspeaker.com/radian 950Bepb-1.htm
https://www.usspeaker.com/radian 951Bepb-1.htm
Again, I may be too ignorant to comment here, but might it be that the main performance issues you had were that the Radian 950 were due to using it with a horn with badly mismatched throat diameters and/or
other geometry, and where your adapter could not fully compensate? Perhaps using the Radian 951 would have worked with no such issues?
may be able to exchange my 3" 743Be for either the 950Be or 951Be
You seem to be fixated on using a Radian driver with an Arai or TAD horn. They are not a good match. I cannot be any more blunt than this.
Having said that, they will still "work", of course. But there are better alternatives, some of which have been mentioned in this thread (and elsewhere) before.
Okay, no 950. But what about the Radian 951 vs. the 745 for the 4001 horn?
https://www.usspeaker.com/radian 951Bepb-1.htm Same throat as 745 but will its larger diaphragm cross with Altec 416 woofer more seamlessly, yet can still be EQed for extended HF response like the 3" 745?
This is simply not true, and I already told you this. The 745Neo has an exit angle of 10 degrees, which is a quite good match.
Also not a great match. Same problem.
The internal throat of the Radian 950/951 compression drivers does not mate well ith the TH-4001's or Yuichi's as pointed out.
The 745 is a better candidate already with a 10 deg. exit angle.
The 745 1,4" will need a throat adapter.
I have seen you mentioned Joseph Crowe in some posts at some point i believe.
Take a look at the 3D model pictures in the link below of the ES-450 with the TD-4002.
See how the exit of the compression driver is smoothly blended to the horn, and the horn "throat" maintaining the same shape as the exit from the compression driver.
https://josephcrowe.com/products/3d-cad-files-es450-biradial-for-tad-td-4002
Having a horn that is a mismatch to the compression driver will have detrimental effects to different degrees.
As for the older JBL/TAD drivers discussed before here is some info:
| Large-format drivers | JBL 375, 376, 2440, 2441, 2445, 2446 | JBL 2450 H/J | TAD TD-4001, TD-4002 | TAD TD-4003 |
| Throat diameter [mm] | 49.2 | 49.2 | 49.2 | 39 |
| Throat angle [deg] | 8 | 10 | 10 | 8,5 |
| Equiv. Fc (Exp) [Hz] | 180 | 217 | 217 | 225 |
| Equiv. Fc (Hypex T=0.7) [Hz] | 235 | 290 | 290 | 300 |
| Equiv. Fc (Hypex T=0.6) [Hz] | 260 | 320 | 320 | 340 |
Spanish PA mfg. DAS also has the ND-8 and K-8 (ferrite version) 2" exit compression drivers that will be a good fit, they are basically JBL copies.
And then there is the slightly modified MeyerSound MS-2001 driver, based on the 2450J, using Alu. diaphragms.
The last pictures i added, you can see the cutaway of a JBL 476 (2450sl style), with the phase plug ending at the driver exit and 0 deg. angle.
Where the cutaway TD-4002 has a throat starting infront of the phase plug that expands from 39 mm to 2" through the throat adapter. And the horn should follow the same shape, set by the drivers internal throat geometry.
And even at 39mm exit, the driver has a short internal throat still.
And a cutaway of the 475ND which is based on the 2450H/J.
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Okay, living room: From the center of the flat south along the east wall to the center of a trigonal north wall is 22 ft 9” on which are three bay casement windows jambs, two ~ 31" x 42 and one slightly wider. The trigonal north wall then becomes flat and continues towards the west wall for another 5 ft; total width of the north wall 15 ft.
South wall is 11 ft wide beyond which is a 39” wide x hallway proceeding south for 15 ft. From that south wall/hallway Intersection but turning north the hallway opens to the living room and proceeds to north wall for 20 ft-while passing a 6 ft 8” x 8 ft kitchen and a 4 ft wide x 8 ft 3” staircase, which then turns and heads downstairs.
Over the living room, kitchen and 4 ft x 8 ft 3” staircase is a triangular ceiling peaking at 11 ft. The living room has 25 year old thin but intact carpeting, almost half of which is covered with new Karastan 0.75” thick remnants.
On the ceiling is a chandelier suspended by a ~ 18” chain and there are a pair of ~ 8” square HVAC vents on axis with each other, ~ 18” from the east and west walls and located in the middle of half the ceiling. On the other half is one other vent located ~ 3 ft from the chandelier. Perhaps all of the above might aide in hanging acoustical treatment ceiling materials?
Presently, there’s lots of empty boxes in the living room but save for my Drexel mid 20th century upholstered swivel rocker, another similar chair and a ~ 55” x 27” x 16.5” x 0.5” open glass table, two torch lamps, pc, NAS, Rythmik subs, preamp and power amps it’s otherwise empty. And the back of my chair is between the 45” x 81.5” door jamb of an open closet in the northwest corner.
Thanks! Great news, so I won't have to spring for the way more expensive 4" diameter models. for the 4001, though I wonder how Chalshus made this work, post 4284.
https://www.diyaudio.com/community/threads/ultimate-open-baffle-gallery.123512/page-215
However, Marco strongly suggests I consider another horn besides the 4001, though hopefully perfect for the 745Be.
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