2251 Variants

[4313B]

I'm having difficulty sorting out 2251J vs 251J variants. 251J-2 is apparently aquaplassed, but not yet available.The 2251J is the Pro driver as you already know.

The 2251J-1 is the Consumer equivalent with a frame color change (4348).

The 251J is the same driver with a mass ring and aquaplas added as previously mentioned in another thread (SK2-1000).

I believe I already posted the 251J specs but could be wrong.

*****

251J (http://audioheritage.org/vbulletin/showthread.php?t=11985)

SK2-1000 (http://audioheritage.org/vbulletin/showpost.php?p=21154&postcount=5)

More SK2-1000 (http://audioheritage.org/vbulletin/showpost.php?p=104911&postcount=5)

SK2-1000 sitting right outside one of the Everest II listening rooms.

[4313B]

SK2-1000BT (http://www.jblsynthesis.com/products/product_detail.aspx?prod=SK2-1000BT&Language=ENG&Country=US&Region=USA)

Dual 10-inch 2251J-2 AquaPlas™-coated, pul-cone woofers with 4" edge-wound voice coils and EPDM rubber surrounds, and utilizing Alnico magnets

Numerous people have noticed this. It is evidently a misprint. The coils are 3" and the magnet is Neo according to the EDS. It happens.

[Earl K]

Dual 10-inch 2251J-2 AquaPlas™-coated, pul-cone woofers with 4" edge-wound voice coils and EPDM rubber surrounds, and utilizing Alnico magnets

For the sake of clarification ; ( please correct the following assertions if wrong )

It is a 10" .
It does have an Aquaplased cone.
It does not have 4" voice coils .
It does use EPDM rubber surrounds .
It does use an Alnico magnet.

Thanks <> :)

[Zilch]

Here's the source of my difficulty/confusion:

2251J Fs = 61 Hz, mms = 32g, per spec.

251J Fs = 60 Hz, mms = 58g, per EDS.

251J EDS would appear to be for 251J-2, actually, though no Aquaplas or mass ring is mentioned. The HCG Part# is consistant with that, being the driver in SK2-1000BT/DG:

http://manuals.harman.com/JBL/HOM/Technical%20Sheet/SK2-1000%20Hercules%20ts.pdf

I don't believe EDS for Pro 2251J has been posted.

Now I'm confused about the magnets and surrounds:

2251J is neodymium. 251J-2 is alnico? Not according to the SK2-1000 TS.

2251J does not have butyl surrounds. 251J(-2?) EDS says "Cloth M Roll."

I'm not seeing alnico or butyl anywhere except in the apparently erroneous Synthesis SK2-1000BT web spec.

Are we looking at an otherwise undocumented product revision there?

There has been mention that GT was working on a potential upgrade.... :dont-know

[4313B]

What you have is a 2251J (Pro) and the 2251J-1 (Consumer) is the same driver with a different paint job.

The 251J is also the same driver but with the addition of the mass ring and aquaplas to extend LF response and decrease efficiency to work specifically in the SK2-1000 box.

Where are you getting this 251J-2?

I realize these conflicting sources of information are mildly irritating but JBL has had those issues forever. As far as parameters go - like we've always said, measure your own for your specific application.

I'll try and scan and post the 2251J when I get home.

Why don't you post some pictures of your 2251J that you just bought so everyone can see.

*****

I just looked at the 4348 Tech Sheet and it lists the 10-inch as Mid-Frequency Transducer 10" (254mm) 225J-1 (339093-001) while the EDS for the 251J says the part number is 339093-002 which is an invalid part number (which doesn't mean a thing).

[4313B]

Now I'm confused about the magnets and surrounds:I really wouldn't bother with being confused about it. You have the driver in your hands and it's the real deal. Second best source of information would probably be the EDS. What is printed on JBL Consumer's website and what is in their computer system has always been hit and miss. They do the best they can and that's about the extent of it. People make mistakes.
Are we looking at an otherwise undocumented product revision there?Not according to G.T.

There has been mention that GT was working on a potential upgrade.... :dont-knowOh, you might be thinking of the 10-inch in the Array1000... it is nowhere near the driver that the 2251J is. But it also has a better bandwidth for its intended application.

[Zilch]

I just looked at the 4348 Tech Sheet and it lists the 10-inch as Mid-Frequency Transducer 10" (254mm) 225J-1 (339093-001) while the EDS for the 251J says the part number is 339093-002 which is an invalid part number (which doesn't mean a thing).Yes, and look at the SK2-1000 TS, where 339093-002 is 251J-2. Synthesis web spec calls it 2251J-2.

Pro 2251J and Consumer 251J-1 are both available, apparently at the same $336 MSRP.

251J-2 is "unknown."

[4313B]

251J EDS would appear to be for 251J-2, actually, though no Aquaplas or mass ring is mentioned. The HCG Part# is consistant with that, being the driver in SK2-1000BT/DG:You keep adding information to your posts and it's tough to keep track of where you're at.

Ok, so Greg should have added a -2 on the EDS... :dont-know

[4313B]

Yes, and look at the SK2-1000 TS, where 339093-002 is 251J-2. Synthesis web spec calls it 2251J-2.Yeah, it's all goofy, especially since JBL adds dashes for any number of reasons.

What is it that you are trying to accomplish? Do you need the smaller bandwidth and higher efficiency of the 2251J? Or do you want the larger bandwidth and lower efficiency of the 251J?

Which driver/part number do you actually have in your possession?

Let's do this, let's say the 2251J is the Pro driver (that's indisputable), the 2251J-1 or 225J-1 or 251J-1 is the 4348 driver and the 251J or 251J-2 is the SK2-1000 driver. :) The part numbers are pretty much set in stone -
339093-001 is the consumer equivalent to the 2251J (124-31002-01)
339093-002 is the same driver with mass ring and aquaplas.
339093-002 is available it just isn't in the system for you to order it. That isn't unusual either.

[4313B]

Pro 2251J and Consumer 251J-1 are both available, apparently at the same $336 MSRP.Get the 1200FE instead then. It's $315 MSRP.

339093-001 MSRP is $365

[Zilch]

What is it that you are trying to accomplish? Do you need the smaller bandwidth and higher efficiency of the 2251J? Or do you want the larger bandwidth and lower efficiency of the 251J?
O.K., I believe we agree on the conclusion regarding part numbers. Please post the 2251J EDS.

I have pro 2251Js, which I am using with 4348 horns. That works great. With a step filter, I'm able to cross them as low as 120 Hz. I still need to do some groundplane measurements to verify what's really going on down there.

Clearly, 251J-2 would make that easier, but they are as yet unorderable. If I can't get there with stock 2251Js, I may consider adding mass rings and Aquaplas to them myself, or at least to the "helper" member of each pair.

[4313B]

Clearly, 251J-2 would make that easier, but they are as yet unavailable. If I can't get there with stock 2251Js, I may consider adding mass rings and Aquaplas to them myself, or at least to the "helper" member of each pair.They are available. You just can't order them right now.

Yes, just add the 10 gram mass ring and 10 grams of aquaplas to what you have.

[Zilch]

It's certainly a major stretch to view anything I might kludge together Q&D as affording competition for anything. ;)

Looks like I'll have more in the parts by the time I'm done than buying the real deal, anyway, with a lesser performance envelope. :dont-know

[4313B]

It's certainly a major stretch to view anything I might kludge together Q&D as affording competition for anything. ;)I would just be careful. People chatter, sometimes innocently.
Looks like I'll have more in the parts by the time I'm done than buying the real deal, anyway, with a lesser performance envelope. :dont-knowI have no idea what you are trying to accomplish. Someone mentioned that they thought that you were trying to build a "4345 killer"...

[Zilch]

JBL Pro 2251J:


The Model 4348's patented Neodymium Differential Drive NDD™ mid-bass transducer delivers increased power handling with reduced distortion, thanks to its unconventional dual voice coil design, which places the coils at opposite ends of the former, rather than coiled around each other. This design improves heat dissipation and minimizes power compression. A third coil between the drive coils acts as a dynamic brake to limit excess excursion and further reduce distortion. As a result, the 4348 performs with outstanding clarity and vocal intelligibility in the important 300 to 1000Hz range.

[Robh3606]

Oh Look here! Nice pictures Zilch. Are those straight sided cones like a 2122 or curvalinear like a 2123??

Rob:)

[Zilch]

Curvilinear. You can see a bit of it in the rear of the cone there at the spider. A "Vortex," when viewed straight on from the face....

[merlin]

2251J-1

Well half of one anyway.

http://i6.photobucket.com/albums/y225/airwise/DSCF218811.jpg

[Zilch]

Merlin's photobucket image is apparently gone. Would someone upload the cross-sectional view to the site in this thread, please? Or at least linke to it?

Did I save it? :banghead:

8" is 2250J. More differential drive info here, larger versions:

http://www.jblpro.com/pub/technote/JBL_TN%201-33%20rev3.pdf

[pos]

Zilch, did you had a chance to weight it, with its neo magnet?
the 2123H is 12lb and the 2012H is 19lb :blink:

[Zilch]

I did not weigh one. They are all mounted now.

At one point I had four boxes, two with drivers, two empty.

I had to open the boxes to find the drivers.... :p

[tomt]

Merlin's photobucket image is apparently gone.

Would someone upload the cross-sectional view to the site in this thread, please?






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