Some observations regarding JBL2440/2441 and diaphragms, including Radian - diyAudio
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Old 29th December 2009, 05:02 PM   #1
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Default Some observations regarding JBL2440/2441 and diaphragms, including Radian

I've been doing some research because I recently acquired a couple of JBL2440s that were supposed to have 2441 diaphragms (one does but with stress fractured surround, but the other has a 2445J diaphragm) so I am effectively looking to rediaphragm one or both, which got me considering my options.

The cheapest way to go would be to rediaphragm the one with a 2445J, and then they would match and have decent HF extension, in addition, although exactly how close to a 2441 I don't actually know since I have read that the phase plugs also differ between the 2440 and 2441 so comments on this matter are solicited. But, presumably, the HF would extend several Khz beyond 10Khz, say at least to 15Khz(?) which would be enough for my purposes here.

The other issue I am considering is aluminum vs titanium. I would really like to go aluminum for SQ reasons, but cost is a factor, considering that two new 2441J diaphragms price out at around $270 apiece. The other major alternative is to use the Radian 1245-16 diaphragm in both, but there apparently has been considerable dissension in other forums regarding the merits of lack thereof of this diaphragm as a JBL replacement, although to give the Radian its due, the worst criticism of it that I've seen still admits it as the best of the aftermarket replacements.

I felt that for this application that I could accept a tradeoff in ultimate ruggedness because I wasn't planning to beat this speaker to within an inch of its life, so the Radian was still in the running from that perspective. Also, the JBL 2441J aluminum diaphragm diamond surround is apparently a significant weak point in high stress applications, as witness the cracked surround on the one driver I received. But that leaves HF frequency response where there appears also to be a difference of opinion, and there I found some information that clarifies the matter significantly for me, at least.

Radian uses the 1245 diaphragm in one of its own drivers, the 950 and includes a response graph, albeit considerably smoothed. This is presumably an optimal application for this diaphragm, but it is reasonable to assume that a similar response is obtainable in the JBL 244x family for which this diaphragm is also intended. But, comparing this graph with the one that JBL provided that superimposes the 2440, 2441 and TAD4001 responses on a JBL 2350 horn, some things become clear.

Above 2khz to about 10khz, the Radian graph shows a smooth 10db rolloff, above which it flattens out (on the average), but with several db of ripple to 20khz. However, this includes an additional 6db dip at 14khz, so the worst case falloff is around 16db, relative to midband. This is still several db more output than the 2440 in the 10-20Khz octave, but limits system efficiency for flat response to the 97db/w/m range if a response out to 20khz without significant dips using a passive xover is required. Comparatively speaking, the JBL 2441J diaphragm has at least 8db more output in this octave, so will support a 2-way passively xovered system with efficiency up to about the 105db/w/m range out to 20khz. In all cases, a CD type horn is assumed. With a smooth flare horn, even the Radian might achieve perhaps 103-104db/w/m on axis while avoiding 'titanium sound' (My basement blasters use all original 2445J's so I know whereof I write here).

So, I am still undecided between the Radian aftermarket diaphragms and shelling out for original D16R-2441s. This particular system does have a smooth tractrix flare horn but will be over 100db/w/m efficient. Comments are appreciated. Btw, besides Radian, does anybody else make an aluminum aftermarket diaphragm for the 2441?

Last edited by thoriated; 29th December 2009 at 05:31 PM. Reason: typo
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Old 29th December 2009, 07:52 PM   #2
ScottG is offline ScottG  United States
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Originally Posted by thoriated View Post

..So, I am still undecided between the Radian aftermarket diaphragms and shelling out for original D16R-2441s. This particular system does have a smooth tractrix flare horn but will be over 100db/w/m efficient. Comments are appreciated..
A few things here..

ALL of Radian's replacement diaphragms for other manufacturers are based on their alloy diaphragms, not pure aluminum like the 950 uses. So in fact the 1245-16 is better compared to their 850 PB, though even that is a significant "stretch" considering the different motors. (..and whatever horns they happened to have used for their published graphs.) Here is a french reseller's measurements for the 850:
http://www.cice-industrie.com/Compre...850%20PB-8.pdf
There at least you can see that it isn't really the upper freq. response that is suffering for a 2 inch exit driver.

I believe that the reason most seem to like Radian's "sound" (if perhaps not their measurement spec.s), is due to their surround and lower freq. performance - i.e. there is more of it, though with an increase in non-linear distortion (..but not a hard distortion "wall" at fs like the metal surround diaphragms have).

IMO though you are "over thinking it" - just find-out Radian's return policy and purchase direct from them if it's suitable. If that works out then it's just a question of if you want to return them or not.
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Old 29th December 2009, 07:55 PM   #3
badman is offline badman  United States
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Quote:
Originally Posted by ScottG View Post
A few things here..

ALL of Radian's replacement diaphragms for other manufacturers are based on their alloy diaphragms, not pure aluminum like the 950 uses. So in fact the 1245-16 is better compared to their 850 PB, though even that is a significant "stretch" considering the different motors. (..and whatever horns they happened to have used for their published graphs.) Here is a french reseller's measurements for the 850:
http://www.cice-industrie.com/Compre...850%20PB-8.pdf
There at least you can see that it isn't really the upper freq. response that is suffering for a 2 inch exit driver.

I believe that the reason most seem to like Radian's "sound" (if perhaps not their measurement spec.s), is due to their surround and lower freq. performance - i.e. there is more of it, though with an increase in non-linear distortion (..but not a hard distortion "wall" at fs like the metal surround diaphragms have).

IMO though you are "over thinking it" - just find-out Radian's return policy and purchase direct from them if it's suitable. If that works out then it's just a question of if you want to return them or not.
It would amaze me if they would accept returns of tested diaphragms.
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Old 29th December 2009, 08:02 PM   #4
ScottG is offline ScottG  United States
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Originally Posted by badman View Post
It would amaze me if they would accept returns of tested diaphragms.
I don't see why not, Partsexpress has it and they are an authorized seller.

Parts-Express.com:*Radian 1245-16 Diaphragm Fits Most JBL 1.5" and 2" 16 Ohm | lansing vc replacement hf high frequency mids midrange

and their return policy:

Parts-Express.com - No Hassle Returns
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Old 29th December 2009, 08:20 PM   #5
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Hi, Scott G. -

Well, there is this from Radian's own description of the 1245 diaphragm:

Radian Audio manufactures a premium 4” compression driver diaphragm, model 1245, for its own model 950 PB compression driver. The Radian model 1245 also fits into several JBL™ 1.4” and 2” exit compression drivers, including model 2445, 2446, 375, 2440, 2441, 2447. 2450, 2451 and into Peavey™ models 44T and 44XT compression drivers. Available in 8 or 16 ohms.

Of course I would prefer to believe that the 1245 has a better HF response that shown for the 950. On reviewing the 950 spec, Radian doesn't indicate whether this measurement is shown for a plane wave tube or reference horn - I tended to assume the latter because the HF rolloff was not as steep as the plane wave tube measurment shown for the 1245 itself.

Last edited by thoriated; 29th December 2009 at 08:33 PM.
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Old 29th December 2009, 10:19 PM   #6
ScottG is offline ScottG  United States
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Originally Posted by thoriated View Post
Hi, Scott G. -

Well, there is this from Radian's own description of the 1245 diaphragm:

Radian Audio manufactures a premium 4” compression driver diaphragm, model 1245, for its own model 950 PB compression driver. The Radian model 1245 also fits into several JBL™ 1.4” and 2” exit compression drivers, including model 2445, 2446, 375, 2440, 2441, 2447. 2450, 2451 and into Peavey™ models 44T and 44XT compression drivers. Available in 8 or 16 ohms.
Yeah, that is kinda funny.

Their literature on the 950 says "pure aluminum"..

Here is cice's on the 950

http://www.cice-industrie.com/Compre...950%20PB-8.pdf

Obviously with the additional impedance "bump" higher in freq. the sample measured has some rear chamber problems with pressure.

The 1245 also has this in the spec.s:

"DIAPHRAGM MATERIAL 0.003 heat-treated aluminum alloy"

..can't be both!

(..I'm inclined to believe now that they are one in the same, and that there is no "pure aluminum" diaphram for the 950. If that is the case then note similarities and differences in the freq. responses of the 950 vs. the 850..)
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Last edited by ScottG; 29th December 2009 at 10:30 PM.
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Old 30th December 2009, 02:35 AM   #7
limono is offline limono  United States
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My friend called me a week ago and mentioned comparison between Radian and Jbl diaphragms on 2440 drivers and 340hz Edgar horns. From his brief remarks I understood that Radian sounded better ,fuller on the bottom but didn't have an extension of original JBL diapers. I don't know what the final verdict was and what other aspects of the sound they evaluated but probably can get you in touch
with people directly involved. Regards, L
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Old 30th December 2009, 02:49 PM   #8
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Have you had a listen to any of the aquaplas coated Ti diaphrams?? Any of the SL compression drivers uses them. They sound quite good. They are not inexpensive but cheaper than the 2441 diaphrams. It's another alternative I don't see mentioned.

Rob
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Old 1st January 2010, 02:20 AM   #9
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Hi, Limono, Robh -

Yes, I would like to correspond with somebody who has actually had the opportunity to directly compare the Radians with JBL diaphragms. And, if Aquaplas can sufficiently mitigate the hardness of the JBL titanium 'pragms', at less than the cost of an original 2441 replacement that is something I would definitely consider.
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Old 1st January 2010, 03:24 PM   #10
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I have experience with the Radian, the 2440, 2445, and 2441 diaphragms in 2441 drivers.

All need a tweeter, the 2440 (smooth as butter) sounds best to me if crossed at/below 3K and above 500 and the Radian sounds better "wide range" as in using it wide open on top with a super tweeter blended in. The 2445 is the least desirable in sound quality. The 2441 is kinda in between the 2440 and the Radian.
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