Looking for any input as to replacing the 2415/2416 diaphragm with a Radian 1225-8. Apparently Radian does not make the required back cap adapter any more. Does anyone have any suggestions for a substitute cap?
Looking for any input as to replacing the 2415/2416 diaphragm with a Radian 1225-8. Apparently Radian does not make the required back cap adapter any more. Does anyone have any suggestions for a substitute cap?
Well, I think I have answered my own question: After obtaining the Radian Audio Engineering drawings of the C1225 Adapter Kit, thanks to Richard Kontrimas of Radian, I found that reproducing the back caps would cost about $400. I decided for less money I could buy used 2426 J drivers and replace the diaphragms with the 8 Ohm Radians. I have not received the both drivers yet, but will report the results.
Hi,
Simply buying some used 2426 drivers ( to load with Radian diaphragms ) is a very reasonable way to go .
OTOH, "old-style" Altec loading caps ( used in many of their older alnico based,small format drivers ) will work over the Radian diaphragm, both bolted to a JBL magnetic structure .
They come up for sale on eBay from time to time ( prices really vary ) .
It's the item on the right-hand side of the following picture .
Hi Earl,
The main problem with the 2416 driver is the lack of mounting holes for a cap. The Radian cap mounts with the same holes and screws as the diaphragm. JBL did not machine the holes in the magnetic return plate on this driver to mount the back cap. I guess the holes could be drilled and threaded in the existing return plate. Man, I would hate to attempt a magnetic gap cleanup after the machine work. There is also a difference in the phase plug between the drivers. The 2416 has the nine concentric holes while the 2426 has the concentric rings. I think I read somewhere that the concentric ring configuration was an upgrade. I hope the new drivers are compatible! At this point I am waiting for the second driver.
Thank you for the reply. I really appreciate your input! Experimentation does not always result in an acceptable answer, Ha Ha.
John.
I made mine with $7 ABS pipe caps from the Home Despot. (Sorry for the sideways images.) Used "Amazing Goop" to seal the holes.
I put felt pads inside for reflection damping, and put steel shelf supports on the bottom edges of the plastic to "grab onto" the magnets: see:
(Not shown here; sorry). I pressed the pins into holes in the plastic to stabilize them, then let the 90-degree angled parts rest on the magnets; it sucked the cap down onto the driver and centered it.
Zonker,
What did you use to seal the cap to the driver. Was the fit tight enough that the seal was not required?
It was a snug fit, but I wrapped a thin band of clear adhesive tape around the seam anyway. (I suppose I could have glued it closed with Amazing Goop, instead.)
The replacement diaphragms were a successful match even though the phase plug is a completely different design. Last fall I was able to buy a new old stock Crown I-Tech 5000HD amp. I did need to equalize the 4425 response: 45Hz -4dB with a Q of 10, 110Hz -2dB with a Q of 4, LP Shelf @ 160Hz -3dB, 800Hz +1dB Q of 1.4, HP Shelf @ 5000Hz -3dB. These old JBLs really woke up! I have compared them to my 6332s which IMHO are very flat in my room. They are an excellent reference source. I have always considered the imaging excellent on the 6332s, but the 4425s are another step above. These things are incredible imagers. The mid range is very good for a two way system with a 12 inch woofer, and I understand why JBL has gone in this direction with there new designs: The M-2s and the 7 series.
A plug for the Crown I-Tech. If you have not heard this amp with a digital source connected to the AES input, seek out a demonstration. The transients and definition are much better then my Benchmark DAC-1 HDR and my Audio Research DAC-1.
John
Nice! I have my pair restored and mirror-imaged but I have yet to fire them up; they're waiting for me to finish my home office. Are you saying that the Radian diaphragms have a different response from the OEM diaphragms?
A buddy of mine has a metal fabrication shop and he's making stands for them; four square metal tubes running vertically between upper and lower horizontal metal plates.
Zonker,
The Radians seem to be a little hotter then the JBL titaniums. But again, I changed the drivers to the 2426's, so I am not sure what effected what. I am running the pads at -4 for the 10kHz and -4.5 for the 2kHz, but the eq. in the amp is set to -3dB shelved at 5kHz. That is probably a preference thing on my part. I have hooked the baby checks up to my old Threshold 500. The sound is sweeter and a little laid back. I did not like the sound with the old titaniums when using the Crown amp. The measurement system I currently have only goes to 500Hz, so the rest of the equalization is by comparison to the 6332s. Certainly subjective!
But, the bottom line is, - I really like these old monitors. I used Event Opals for about 5 years before getting the 6332 JBL's. My opinion is: The JBL's are in a completely different league. If I were mixing, I know what I would be using.
John
OK; thanks; I think I understand.
I really like these old monitors. I used Event Opals for about 5 years before getting the 6332 JBL's. My opinion is: The JBL's are in a completely different league. If I were mixing, I know what I would be using.
Are you saying you like the 6332s over the Opals, or the 4425s over the Opals, or both?
Zonker,
Yep,
I think both the JBLs are in another league. I really don't think they even compare. The Events have a pretty fuzzy mid. and the low end is not flat and can't be made flat. The upper end of the Events is wirey sounding and not flat at all. The Events image OK but not even close to the 4425s. I think the 4425s make a great video speaker also. They image so well you do not need a center channel.
Did you see the comment from Greg Timbers about the listening center of the 4425 being slightly above the speaker? He says that is where the crossover sum is the flattest. Below is the eq. that the Crown is feeding to the 4425's. I have one for the 6332's also.
Regards,
John
Very cool; thanks. I had not seen that comment about the 4425 listening center, but I'm glad to hear it, since I deliberately designed my stands a little low to keep the speakers less tippy.
I'm not finished experimenting with the 4425s. I think the design philosophy concerning the frequency response was a little different then with the newer JBLs. The high end of the frequency spectrum was a collection of measurements taken in the dispersion pattern and summed for the newer designs? Or something a little more complicated then that. Maybe a sum of the direct and first reflected wave were summed. Anyway, the 6332s are considerably more "polite" at the top end. I need to purchase a measurement setup and haul everything outside to come up with a real eq. for these.
Zonker. I am looking forward to hearing of your listening adventures with these classics. I recently acquired a tired pair of 4333Bs. So I am working to get those guys restored and operating. At this point I am calling them the money sinks!
John
Yeah, can't wait to fire them up! Pictures here: http://www.audiokarma.org/forums/sho...d.php?t=654308
4333Bs are way cool. I just finished some 4435s:
http://www.audiokarma.org/forums/sho...d.php?t=654301
And earlier, some 4430s and 250Tis.
Eric
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