Another driver in 4345.

[matsj]

I just a have questions about 4345.

I have 2 2245h, 2 2405 laying at home and i want to start looking for the other parts to build a pair 4345 in future.

Is there a "better" driver than 2421b ? 2426 ? 2435 ? 2450 ? I have 2 2450 drivers also.

Is someone making the stickers or can i buy them new ?

What color code is JBL blue ?

mats

[richluvsound]

Hi Mats,

I'm no expert, but I'd use either the 2426J , 2425J, dusted, (aquaplas) or the 2435 hpl -be . I'll be trying out the 2435 if it ever gets here from the US. The CD is the weekest part of the system based on my experience.Hey, if you really want to go for it and money is not an issue, the TAD 2002 is very highly rated.There is a fair bit in the search on this.

For foilcals and grill badges get intouch with Kenji at www.jbl43.net ,or PM riessen.

As for the JBL blue, the RAL can't be trusted. Rich Blue is pretty close having never seen the real thing , but that will change when I see HP's collection It can be mixed from eye. If not, I wasted 6 years in art school. I need to mix a batch for my 4333 and would gladly make some up for you. Just let me know !

good luck and keep us posted. Man they are worth the effort

Rich

[matsj]

Thanks Rich.

Money is a issue. The Tad are too expensive for me, i´m a regular worker . I think we are sitting in the same boat with the 2435 drivers . I´m also waiting for some drivers.

Your 4345 is VERY nice Rich.

mats

[speakerdave]

Yeah, do a search on this. There's a lot of reading to catch up on here.

David

[Robh3606]

Hello Mats

As a suggestion I would build them with the original drivers, have a listen, and then go from there.

Rob

[Ian Mackenzie]

As Rob mentioned I would start out with a 2425 so you have a baseline and consider purchasing a v.good measurement kit if you intend to explore using other compression drivers.

An acquaplas treated titanium diaphagm is a significant advance on the stock titanium diaphagm and requires no further modification of the network other than increasing the level by 1 db as there is a loss of about 1 db after acquaplas treatment.

One of the key differences in using an acquaplas coated diaphragm is a much broader range of useable adjustment (sweet spot)for the horn level over the untreated diaphragm. This is not so much to do with a smoother amplitude frequency response but a much improved (damped) time domain response above the mass rolloff frequency of the diaphragm. This is quite audible. The timbre tonal transition from the 2122H to the horn is very close with the acquaplas treatment.

The stock crossover was designed around the 2421/2425 driver and other drivers would require re-optimisation of the network. (the impediance and FR of the drivers/horn and lense assembly mounted on the 4345baffle will vary from one driver to another).

Adjustment of the L pads may compensate for some differences but will not necessarily give a true indication of how the system is performing with an alternative driver.

Some work is currently in progress on using other drivers with this system but I would recommend the acquaplas treatment of a stock driver as the known best alternative at the moment.

Ian

The images are the acquplas treated diaphragm appearance, the response curves are live in room tests on an actual 4345 baffle and are un smoothed, full raw response of the acquaplas diaghrapm, original equivalent HF filter response (acquaplas treated), full range response with HF Lpad adjusted +1 db (acquaplas treated) and the full range response with the stock titanium diaphragm). Note there is a 2 db rise in the microphone above 10 khertz. Small variations in response are due to room interference but I think there is a little less noise in the treated diaphragm. As can be seen in both cases the overall response is remarkable smooth but to the ear there is a tonal difference.

These tests were done some 12 months ago with a fairly basic measurement setup but you get the idea. In the end it ain't what you can see but how it sounds!

[Russellc]

As Rob mentioned I would start out with a 2425 so you have a baseline and consider purchasing a v.good measurement kit if you intend to explore using other compression drivers.

An acquaplas treated titanium diaphagm is a significant advance on the stock titanium diaphagm and requires no further modification of the network other than increasing the level by 1 db as there is a loss of about 1 db after acquaplas treatment.

One of the key differences in using an acquaplas coated diaphragm is a much broader range of useable adjustment (sweet spot)for the horn level over the untreated diaphragm. This is not so much to do with a smoother amplitude frequency response but a much improved (damped) time domain response above the mass rolloff frequency of the diaphragm. This is quite audible. The timbre tonal transition from the 2122H to the horn is very close with the acquaplas treatment.

The stock crossover was designed around the 2421/2425 driver and other drivers would require re-optimisation of the network. (the impediance and FR of the drivers/horn and lense assembly mounted on the 4345baffle will vary from one driver to another).

Adjustment of the L pads may compensate for some differences but will not necessarily give a true indication of how the system is performing with an alternative driver.

Some work is currently in progress on using other drivers with this system but I would recommend the acquaplas treatment of a stock driver as the known best alternative at the moment.

Ian

The images are the acquplas treated diaphragm appearance, the response curves are live in room tests on an actual 4345 baffle and are un smoothed, full raw response of the acquaplas diaghrapm, original equivalent HF filter response (acquaplas treated), full range response with HF Lpad adjusted +1 db (acquaplas treated) and the full range response with the stock titanium diaphragm). Note there is a 2 db rise in the microphone above 10 khertz. Small variations in response are due to room interference but I think there is a little less noise in the treated diaphragm. As can be seen in both cases the overall response is remarkable smooth but to the ear there is a tonal difference.

These tests were done some 12 months ago with a fairly basic measurement setup but you get the idea. In the end it ain't what you can see but how it sounds!

Ian, please educate me, do I have the diaphram of the 2425 "treated" or do I just buy a replacement? I have a JBL service center nearby in either event.

Thanks,

Russellc

[boputnam]

Ian, please educate me, do I have the diaphram of the 2425 "treated"...?

And, until you're able to sort that out, the 2421B actually sounds damn good with a new OEM diaphragm. Don't be afraid of the original components...

[matsj]

Thanks for the input. I´m looking around to se what drivers i can lay my hands on.
If i drive them fully active will a 2123 and 2426 be better. I don´t think i can get the 2122/2123, 2308 here in Sweden/Denmark. If i drive them active it´s no problem with the passive x over for the 2123 and 2426.

But i´m in no hurry, i will buy the drivers when they appeirs and i have the money.

mats

[Ian Mackenzie]

Russellc,


Some members have decided to meet the challenge and do a diy treatment with a small art brush/air brush. Suggest you follow their posts.

JBL used to have a replacement dusted diapgragm, it was both expensive and difficult to obtain.

In reference to the other comments I sometimes miss the warm luminous tone of the un treated diaphragms and wonder if the treatment almost overdamps it but the postives outweight the negatives with the improvement most obvious on classical recordings. A lighter treated diaphragm would be interesting candidate. As it is (treated) its more akin to a B&W802 on steriods or as some poor visitior said King Kong with his gloves on!

Some people find comfort in the 2397 and smaller interations, each to his own i guess.

Ian

Ian