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I have the 4622N's. Would upgrading the CD to the 2432 (from the 4722) be worthwhile? The networks are different too. I would even consider the 2452SL, but that might require alot more tweaking. Are the BE phragms available in 1.5" yet? Although those would likely be cost prohibitive. I don't have any real measurement capability.
 

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Quote:
Originally Posted by Wrager
I have the 4622N's. Would upgrading the CD to the 2432 (from the 4722) be worthwhile? The networks are different too. I would even consider the 2452SL, but that might require alot more tweaking. Are the BE phragms available in 1.5" yet? Although those would likely be cost prohibitive. I don't have any real measurement capability.
I've never heard the 2432, but by most accounts the aluminum phragm in the 2431 sounds better than the titanium phragm in the 2432. JBL moved to titanium mainly for better power handling and durability.


From a SQ perspective, it generally goes ti -> al -> be. Mylar is probably somewhere between al and be, but JBL doesn't use it in large format drivers for obvious reasons. These are just generalizations about the sonic signature of the phragms. There are many other elements at play.


(For instance, in talking to Zilch, he preferred the Mylar BMS 4555 over the 2432, but preferred the 2452H-SL over both)


You might ask, why not the 4555 then? It won't play low enough for the 800hz cross on the 4622 (those woofers and the CTC spacing need it that low). 1khz is the 4555's lower limit, otherwise it would be the likely choice.


To throw things off, JBL coats some of the phragms in aquaplas such as the 2452H-SL. This takes the edge off of the typical titanium harshness. They also coat their beryllium Everest drivers which are unobtanium and when they do show up go for $2k and up.


So what are your options? I see two. The 2435HPL and the 2452H-SL. The 2435HPL is basically a beryllium version of your 2431. It has the same phase plug, but with the superior phragm. The 2452H-SL is the current TOTL JBL pro CD. I own the 2452H-SLs. They are awesome to say the least, but not cheap.


The 2452H-SL has the latest phase plug which gives it very smooth response up to 20khz, something no other 4" phragm (or 3" for that matter) has been able to do. It is coated which is a big improvement and has a modestly priced replaceable phragm. The downside is cost. New it is something like $1300. Used varies, but is still high.


The 2435HPL is discontinued I believe, but you can find them on the bay. I think they sell for less than the 2452H-SL. I haven't heard them, but they are very well-liked. They have a non-coated 3" Be phragm. The phase plug doesn't give the smooth 20khz extension like the 2452H-SL but it is pretty much the same as your 2431 in that regard.


Which sounds better? I haven't heard the 2435, but in private talks with Zilch, he loved both, slightly preferring the 2452H-SL. But, the 2435HPL can probably be swapped in without any crossover changes and sound great. Of course, you could run some measurements and tweak the crossover, but you would be fine running as-is.


There are two downsides to the 2435HPL. First, it requires ferrofluid on the coil. From what I've been told, some of the ebay 2435's need a ferrofluid touch up. I don't know what the likelihood is that it will be dry. Second, a replacement phragm is around $700-900 (if they even stock them). You better hope the one you buy on ebay is solid.


The 2452H-SL uses a $185 phragm and is easy to find. You could also use a 2452H and swap in a SL phragm. The downside to the 2452 is that you will need to tweak the crossover. I'd certainly be willing to help if you are willing to measure FR and impedance. It would be very easy.


Here are links on audioheritage to the internal JBL spec sheets for these drivers:


2431H - http://www.audioheritage.org/vbullet...hp?21758-2431h

2435HPL - http://www.audioheritage.org/vbullet...hp?14369-2435h

2452H-SL - http://www.audioheritage.org/vbullet...21706-2452h-sl
 

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Discussion Starter · #3 ·
Thanks Max, as usual a very thorough and excellent response.


The 4622 actually uses the 2430H. Is it Ti? I do have a 2431 in my AM6215. I do like its sound very much. I didn't realize the 2435HPL was Be. I may look for one to try.


Thanks again Max!
 

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Ah, I thought it was the 2431H. I can't find much info on the 2430H. I found one thread on AudioHeritage: http://www.audioheritage.org/vbullet...ighlight=2430h


It seems to be an aluminum phragm. It also seems to have a very similar FR to the 2431 and 2435. The 31 and 35 seem to have better HF extension. They are all pretty close in FR and impedance it would appear. You could first try swapping in the 2431 from AM6215 into your 4622. If you can take some measurements, great, but subjective will do.


If that seems to work well, I think the 2435 is worth a shot. Just understand the risks I detailed above. If you get a good unit, you are fine. Just don't blow the diaphragm. The good thing is that in home use, unless you do something really stupid, it is hard to blow these guys up.
 
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