The difference in 2220 & 2225 Voice coils

[mark214]

I picked up a trashed 2220 last weekend and decided to strip it down today. I was surprised to see the differences in the voice coils.
The 2220 is not as rigid, not as deep and mainly paper. The 2225 is very rigid, deeper and with a metal band inside.
From the literature JBL put out when I thought of a 4" JBL edgewound voice coil I always envisioned the one on the right not the one on the left.

The 2220 is on the left 2225 on the right.


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[Eaulive]

the 2220 has an underhung voice coil, meaning the gap is longer than the voice coil. It has a light cone and former and is very sensitive, it's basically a mid-bass driver.
The 2225 has a long coil and short gap (overhung), the assembly is heavier and has less sensitivity but more low end.

BTW, the coil on the right doesn't look like an original JBL, it has an aluminum former, the spider is different and the coil is longer.
This one is an original 2225, although defective.
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[speakerdave]

the 2220 has an underhung voice coil, meaning the gap is longer than the voice coil . . . .

Hmmm . . . . first I've head that, and I actually don't think so. Can you point to the specs somewhere? My recollection in reading, a while back, and I can't say where, is that in this driver the voice coil winding length and the magnetic gap depth are about the same. It is designed as a low excursion driver and primarily meant to be horn loaded, with a design goal of maximum noise rather than lowest distortion.

Athough technically underhung, the difference in voice coil winding length and the gap depth is only 1.8 mm. This is a Lowther type excursion which I'm sure the 130a/2220 exceeds in normal use, especially when baffle mounted. The spec excursion before damage is 16 mm with a T/S spec of 3mm. Looking at the sheet for the 2220H the use of SFG technology would suggest the engineers expect the voice coil to partially leave the gap on excursion. A truly underhung voice coil does not, even at its maximum specified excursion. JbL LE15A/2215, 1400nd, LE8T, and 1500Al (I think) and Altec 515B, for example. All of these drivers, which are described in the literature as underhung (the 2220 is not), have significantly greater excursions than the 2220, yet the magnetic gap is deep enough to accommodate them fully.

Setting all that aside, I have a pair of 2220B's which I treasure for the fact that when I am ready to have a huge pair of speakers with no VLF to drive with a tiny tube amp with no VLFs, at low volume, I'll have the woofers I need.

[subwoof]

actually the 2220 is "barely hung"......it's voice coil length is close to the actual gap length.

The 2225 and related are over hung

The LE15/2215 and underhung ( with a gap depth even greater that both of the above ).

There is a very good paper ( pro note ) released by JBL on this but it's impossible to get this site to add to the library anymore. we have tried for years..:(

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[1audiohack]

There is a very good paper ( pro note ) released by JBL on this but it's impossible to get this site to add to the library anymore. we have tried for years..:( sub

Will you post it or provide a link to it please?

Thank you,
Barry.

[subwoof]

JBL's website has changed 200,000 times and without a half days effort, impossible to find material that I had linked before. The pro notes currently posted omit all the older, more relevant ones alas.

http://www.jblpro.com/catalog/general/technicallibrary.aspx

Even then many of these things were (A) never scanned/posted in the first place, (B) are such poor quality that they cannot be read or (C) nested so deep they are not searchable.

sorry for the sarcam but JBL's documentation is stuff of legend around here...:(

If I had a way to make pdf's I would scan the entire lot ( I have them all somewhere ) and post. Maybe this winter.

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[louped garouv]

If I had a way to make pdf's I would scan the entire lot ( I have them all somewhere ) and post. Maybe this winter.

sub

sub,
i just got a new scanner with an auto feed feature...
(it's not a super nice one, but produces acceptable quality -- an HP 6500A)

if you have the inclination to ship them, I would be willing to scan them -- host them up somewhere online -- and ship them back to you...

it's just a few 4" binders worth of paperwork at the most, right?

just a thought...


I hope all is well....


David

[Eaulive]

Hmmm . . . . first I've head that, and I actually don't think so. Can you point to the specs somewhere? My recollection in reading, a while back, and I can't say where, is that in this driver the voice coil winding length and the magnetic gap depth are about the same. It is designed as a low excursion driver and primarily meant to be horn loaded, with a design goal of maximum noise rather than lowest distortion.

Athough technically underhung, the difference in voice coil winding length and the gap depth is only 1.8 mm. This is a Lowther type excursion which I'm sure the 130a/2220 exceeds in normal use, especially when baffle mounted. The spec excursion before damage is 16 mm with a T/S spec of 3mm. Looking at the sheet for the 2220H the use of SFG technology would suggest the engineers expect the voice coil to partially leave the gap on excursion. A truly underhung voice coil does not, even at its maximum specified excursion. JbL LE15A/2215, 1400nd, LE8T, and 1500Al (I think) and Altec 515B, for example. All of these drivers, which are described in the literature as underhung (the 2220 is not), have significantly greater excursions than the 2220, yet the magnetic gap is deep enough to accommodate them fully.

Setting all that aside, I have a pair of 2220B's which I treasure for the fact that when I am ready to have a huge pair of speakers with no VLF to drive with a tiny tube amp with no VLFs, at low volume, I'll have the woofers I need.

The datasheet of the 2220 I have here says "magnetic gap depth 9mm" and "voice coil winding depth 7.2mm"
JBL talks about the 2220 as an underhung woofer, although slightly it's true.
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I hope the way I attached it will work.

[speakerdave]

That's very interesting, and I appreciate having that information. Mounted in a horn or used as a midbass the 2220/130a is effectively underhung, or nearly so. I'm looking at them with new eyes. Thanks.

[GordonW]

BTW, the coil on the right doesn't look like an original JBL, it has an aluminum former, the spider is different and the coil is longer.


I agree with this assessment. All 2225s I've seen, at least for the last two decades or more, have had Kapton formers. I suspect that is either a Waldom or Chinese recone for 2225.

Even the more common aftermarket recone kits (MWA Speaker Parts, primarily) have the right Kapton former...

Regards,
Gordon.

[edgewound]

I agree with this assessment. All 2225s I've seen, at least for the last two decades or more, have had Kapton formers. I suspect that is either a Waldom or Chinese recone for 2225.

Even the more common aftermarket recone kits (MWA Speaker Parts, primarily) have the right Kapton former...

Regards,
Gordon.

Both coils in the fist photo are OEM JBL. Guaranteed. There was phase when voice coils were aluminum formers. Some 2235 have aluminum formers, too.

The quality of the coil stack windings and the markings are a signature giveaway.

[Eaulive]

Both coils in the fist photo are OEM JBL. Guaranteed. There was phase when voice coils were aluminum formers. Some 2235 have aluminum formers, too.

The quality of the coil stack windings and the markings are a signature giveaway.

What about the black spider and the obviously longer coil (compared to my posting of a recent _and defective_ 2225 kit from Mexico) of the assumed 2225 on the right?

Again I'm not trying to challenge your experience, I just want to know ;)

If you look at the two 2225 pictures, the one on top has obviously more winding and less space between the coil and the spider. Apart from the black spider and the Al former.
It's true that the winding is perfect though.

[edgewound]

What about the black spider and the obviously longer coil (compared to my posting of a recent _and defective_ 2225 kit from Mexico) of the assumed 2225 on the right?

Again I'm not trying to challenge your experience, I just want to know ;)

If you look at the two 2225 pictures, the one on top has obviously more winding and less space between the coil and the spider. Apart from the black spider and the Al former.
It's true that the winding is perfect though.

I guess I should have clarified the coils in the post #1 photo. Sorry 'bout that.

The coil on the left is a 2220. The coil on the right is a 2235. I've experienced the same problems with out of the box defects from Mexico as I explained in this post from another thread about "the experiment which seemed to work" from GordonW:


Production of JBL OEM kits have been moved south of the border to a Harman facility that's been there for decades. Granted...the quality and precision and delivery of the recone kits has been painfully slow and a real work in progress.

That said...the parts that I have received in JBL acceptable quality have been very good. A recent D8R2431 with "Made in Mexico" on the box was perfect. Same with 2241, 2226, 2235, 128H-1, E120, E130, E140. I just shipped a pair of 2235H to Michigan that were beautiful and the customer was quite pleased on receipt. I had a C8R2220 out of the box several months back that was a reject. Many of us Authorized Service agencies have raised a lot of noise about it and they responded with replacing entire production runs of parts.

I'll say it again regarding aftermarket parts. It better be damn close/identical to OEM in every regard for it to be JBL acceptable. Outside of that it's just another cast frame speaker with potential to be great.

Please keep in this in mind...There was a an episode of bad production parts 22 years ago when I couldn't use any parts that came off the production line. Harman was going through a bad transition of people that were inexperienced on the production line....much like has just happened in Mexico. This can and will happen with a labor force that is inexperienced with precision assemblies. Here' the funny parts with reconing speakers. There are a few companies that sell preassembled precision recone kits for their low frequency drivers. JBL, Celestion, B&C, RCF, Tannoy and probably a few other that I can't think of right now. They are pre-assembled to ensure that the voice coil is positioned in the gap for proper performance. Electro-Voice supplies recones kits as loose parts...but there are factory centering/depth jigs that are required by EV to do the job correctly. This still puts the assembly precision at the mercy of the reconer.

I've seen so many ebay recones passed off as original OEM parts for any of the above drivers that someone has to be on the look out for either out and out fraud or "just as good as the original" when buyers are looking to get something on the cheap. If you don't have the trained eye of experience building this stuff with the actual genuine parts from the manufacturer and know the differences from aftermarket parts, you will get burned by scam artists. I don't have a problem with full disclosure of aftermarket parts as long as it's fully disclosed that it's different from OEM. Most of the time the seller says it's 'the same parts that the factory uses'. Many times it's a buyer that has bought an ebay item and regretted the purchase trying unload it on another unsuspecting buyer.

It's a mean world out there. Someone's trying to look out for your best Lansing Heritage Legacy quality.

I'm one of them, and I'll fly the JBL flag as long as they do the parts and performance well. At some point I might do aftermarketparts as well....but I'll try to match the JBL specs and construction techniques before I claim they are "Factory OEM Equivalent".

Stepping off soapbox now.:)

[Eaulive]

I guess I should have clarified the coils in the post #1 photo. Sorry 'bout that.

The coil on the left is a 2220. The coil on the right is a 2235.

Right, now I feel better :D

Still, until today I would have rejected any C8R2225 or C8R2235 with an aluminum former and a black spider... I guess one never stops learning :)