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Mike C
08-14-2003, 04:18 PM
Hi guys, last week I bought a pair of JBL 4691b boxes off Ebay. I was happy when they turned up as their condition was better than I expected. MMnn what to load them with? well I had a pair of 2231a drivers and 2420 compression drivers out of a pair of old 4331 monitors I also got off Ebay kicking around so they were the candidates. The boxes use a 2370 horn ( I don't hear much spoken about the 2370's but believe me they are brilliant with the 2420 ) the cd's took some getting into the boxes the cradles are designed for the later smaller drivers. I removed the original crossover networks (1500hz ) and fitted a pair of 3120a - 1200hz networks. The end resalt " WOW " the bass drivers seem to like the smaller enclosures ( 4cuft v's approx 5.5 cuft for the 4331's ).
The sound is so spacious and no real sweet spot which is nice. I coupled the 4691's with a pair of 2241's I have in 6 cuft bins tuned to 40hz, and crossed them at 100 hz. The bottom end is so full and warm I am so happy with the resalts. I am going to try a pair of 2220's in the bottom end to balance the system a little better as the efficientcy is down a little on the 2231's and a little more mid bass would be great. I'm also sourcing a pair of E-145's , I believe they work real nice at home.

GordonW
08-14-2003, 10:44 PM
I think you'll like the 2220/D130. Lighter cone mass = not only more efficient, but faster/better midrange as well. It won't go much below 50 Hz in that box, but with a 100 Hz crossover point, it should be gravy... :smthsail:

Though, if you can swing it to actually find a pair of E145s, well, far be it from me to tell you to NOT get (and happily use) those... :D

BTW: If you happen to want to do it, you can easily have your 2231s reconed as 2220s, IIRC. Any JBL reconer should be able to advise on this...

Regards,
Gordon.

Robh3606
08-15-2003, 03:09 PM
For what's it's worth I just got a pair of E-145's. One in excellent condition, the other a frame which I had reconed. Very nice drivers! I have been breaking them in without subs and they surprised me with the lowend I get from them. Nice, fast and tuneful.

Rob:)

Earl K
08-15-2003, 06:12 PM
Gordon / Mike

A modern 2220h cone in the shallower 2231 gap won't give the same performance as a bonafide 2220 ( H-style ) . It will likely result in a woofer that has performance more akin to the older 50/60s' 130a ( still an all-round favourite of some older audiophiles ) .

The 2220H magnet assembly has a gap depth of .35" ( 9mm ) while the 2231/2205/2225/2235 family of motors use the standard, shallower .28" ( 7.1 mm ) top plate depth . All things being equal, the extra depth offers better motional control of the cone. The modern ( motor ) successor in this evolution of cone control is found in the 2227h and the 2242. Their motional control is provided by an even deeper gap ( of .5" or 12.7mm ) and a magnet assembly weight of 23 lbs.

I know the later 70s' Alnico 2220 a/b series also had the .35" deep gap. - ( I just did a comparison between a 2205a and 2220a ).

I don't want to sound like I discourage mixing and matching cones with alternative magnet assemblies - it's just that - a person should be aware of the hit & miss aspect of these experiments. It's not a great hobby for the pocket-book challenged or those who don't/can't measure TS parameters.

While I'm at it; I'd discourage attempting to recycle or "improve" a 2241 by fitting it's small 15 lb magnetic assembly with a heavier cone kit. A close read of its' operational parameters and a look at the somewhat puny under-sized magnet ( 2226 style with only a .32" deep gap ) indicates a woofer already living close to the motional edge . This is evident in the Qts figure given for the 2241. A heavier cone kit ( like the 2245h that wants to see a .35" deep gap with 5 lbs more of magnet ) being fumbled about by that undersized magnet will give an 18" version of those old and pretty mediocore 125/127 series woofers. Do people really want JBL labelled woofers with a Qts of .5 or .6 ???

I'm off my soap-box now . :rockon1:

regards <> Earl K

boputnam
08-15-2003, 06:35 PM
"I'm off my soap-box now . Maybe, but THAT soap-box is a keeper! ;)

Mike C
08-15-2003, 08:59 PM
Hi Earl, the 2220's I'm chasing are h's I'm led to believe. At $250au each they are cheap. Recones are rediculously expensive in australia, so I keep buying what I can s/h.
I'm also chasing a pair of E-145's and E-140's.
I like the sound of the 2231's but unfortunatly they are too inefficient compared to all my other drivers. I have to pad all the other drivers down too much to get some sort of balance and this appears to weaken the dynamics of the whole sound.
Regards Mike

GordonW
08-15-2003, 11:32 PM
A modern 2220h cone in the shallower 2231 gap won't give the same performance as a bonafide 2220 ( H-style ) . It will likely result in a woofer that has performance more akin to the older 50/60s' 130a ( still an all-round favourite of some older audiophiles ) .

That wouldn't be so bad, actually... the original designs with the 130A used a 1200 Hz crossover (to the 175, which is really the spiritual predecessor to the 2420, et al), so he's right in the ballpark there. A modern 2220 kit should give slightly flatter midrange than the 130A (which wasn't bad, in the first place, really, come to think of it)... and truthfully, he doesn't really need the extension of the D130/2220 (which would be the primary benefit in this case of a larger motor); in fact, the mass-rolloff of the "130a-esque" woofer might be a benefit, in helping the crossover between the cone and horn have less overlap (and possibly avoid "honkiness" and "blattiness" in the upper mids)...

Regards,
Gordon.

Earl K
08-16-2003, 05:40 AM
Mike

Yes, the more obscure cone kits are continuing to rise in price and it'll only get worse. Finding old usable woofers versus reconing might be the only way to go - and now is the time to be buying.. I can understand your need for maximum dynamics in a system ,,, considering your line of work.
:cheers:
regards <. Earl K

Earl K
08-16-2003, 06:06 AM
Gordon
There's no argument from me, I do believe everyone should begin their personal woofer education by owning a pair of 130a (s). Having that sonic reference would make it easier to mentally catalog all the "Twists & Turns" that JBL executed while attending to the ever evolving needs of the M.I. & Pro Sound market. It's useful info to have a sonic reference of what results from adding weight to a minimum mass cone .

Given the chance, I intend to acquire a pair for the above stated reasons.
Plus, I want to compare them to my Altec 416-8c woofers, which roughly occupy a similar territory .:blah:

regards <> Earl K :)

Robh3606
08-16-2003, 08:58 AM
Hello Earl

Just wondering if the T/S for the 130 and 130A are different. I would assume they are. The new t/s on the JBL Pro site has the D130 only. To make an A asside from the dome change did they change the cone mass or suspension?? How are they?? I was looking at the mass of the 130 vs the E-145 60 vs. 55. I really like the 145's asside from the higher effciency how do the 2 compare?? I guess it should be a 130A vs. 150-4 the Hartsfield driver comparison.

Rob:)

John Y.
08-16-2003, 10:54 AM
To all,

Remember, the 130A (and the 150-4C) had copper coils. The D130 had aluminum. I think that was the major difference between 130A and D130 and accounted for the slightly higher free resonance of the 130A, whereas the extended highs of the D130 were partially aided by the lighter aluminum coil (and, of course, the aluminum dome).

John

Earl K
08-16-2003, 11:08 AM
Hi RobH

What TS figures are you looking through ? The latest that I have were downloaded this summer --- and they have the 130A - plain as day - on the first page of actual TS info . :flamed:

Among other things, you can see the cone weight differences or Mms values ( 70 Mms vs the 60Mms of the D130 vs the 55 Mms for the E145 ).

I intend to acquire some - sometime - but I don't have them yet - so I can't answer your other questons now. :spin:


- good point, JohnY. about the copper voice coil ! :)

regards <> Earl K :wave:

Robh3606
08-16-2003, 02:58 PM
Well guess what same as you I am just blind as a bat! :banghead:

Thanks

The E145 is a copper coil too.

Rob:)