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View Full Version : An experiment that seems to have worked- converting 2213H to 128H w/ aftermarket kit



GordonW
10-28-2011, 09:10 AM
I had just gotten a pair of dead 2213H frames... cones were destroyed and thrown away.

Since there are no good 2213H/123A kits readily available in the aftermarket... I decided to see what would happen converting over to 128H/129H type spec, using the 128H-1 kit from MWA Speaker Parts.

I have to say- it seems to have worked fine.

All parameters, measured by Dayton Woofer Tester 3, are within 10% of original spec, once woofer is broken in. It measures between the parameters of the 128H and 129H, in terms of optimum box tuning (i.e, it would work in L65, L150, L112 and such, fine). HF performance seems to match the published curves for 128H within a dB or so, too.

I did make one cosmetic alteration- the MWA cone has a "purple" tint... so, I masked off the surround, and lightly painted the cone with flat black acrylic spray paint. That made it look a lot more like the matt Aquaplas texture of a 128H-1.

There will always be those who only want factory parts- and that's their perogative- but, this can be a good option, for those with dead frames, that simply just want a way to make something useful and functional with them, without spending a ton of money. After all, there's a LOT of things a good "128H clone" could be useful for...

Regards,
Gordon.

Earl K
10-28-2011, 09:58 AM
Thanks for the info Gordon .

Good to know .

<> :)

edgewound
10-28-2011, 11:58 AM
I had just gotten a pair of dead 2213H frames... cones were destroyed and thrown away.

Since there are no good 2213H/123A kits readily available in the aftermarket... I decided to see what would happen converting over to 128H/129H type spec, using the 128H-1 kit from MWA Speaker Parts.

I have to say- it seems to have worked fine.

All parameters, measured by Dayton Woofer Tester 3, are within 10% of original spec, once woofer is broken in. It measures between the parameters of the 128H and 129H, in terms of optimum box tuning (i.e, it would work in L65, L150, L112 and such, fine). HF performance seems to match the published curves for 128H within a dB or so, too.

I did make one cosmetic alteration- the MWA cone has a "purple" tint... so, I masked off the surround, and lightly painted the cone with flat black acrylic spray paint. That made it look a lot more like the matt Aquaplas texture of a 128H-1.

There will always be those who only want factory parts- and that's their perogative- but, this can be a good option, for those with dead frames, that simply just want a way to make something useful and functional with them, without spending a ton of money. After all, there's a LOT of things a good "128H clone" could be useful for...

Regards,
Gordon.

It'll take more than flat black spray paint to make it sound the same. WT parameters are fine for mechanical charateristics but it won't measure how the cone acts when sound is applied.

There is a difference. I'm all for aftermarket parts when OEM parts aren't available...BUT...

I'm totally against the aftermarket making claims that are sure to come up short with disregard and disrespect for JBL's extensive R&D efforts.

GordonW
10-28-2011, 12:53 PM
It'll take more than flat black spray paint to make it sound the same. WT parameters are fine for mechanical charateristics but it won't measure how the cone acts when sound is applied.

There is a difference. I'm all for aftermarket parts when OEM parts aren't available...BUT...

I'm totally against the aftermarket making claims that are sure to come up short with disregard and disrespect for JBL's extensive R&D efforts.

Please don't go down this road. This sort of dismissive attitude is why a number of us have pretty much stopped posting here, much, anymore.

Was the part "HF performance seems to match the published curves for 128H within a dB or so" not clear enough?

Yeah, I didn't do distortion analysis... but that's usually more of a function of the motor than the cone material, anyway. And yeah, I AM qualified to make that statement, having done quite a bit of design and building work, using LEAP/LMS, Clio, and other measurement and design systems, over the last two decades. I actually HAVE specified and had built, woofers for custom applications, for up to $30K bespoke speaker systems, personally myself...

If the preponderance of people here really don't care to get this kind of data from me, when I find something I find interesting like this, I can just go away and stop posting again. No skin off my back. I'm not mad... I just don't want to impose on the proceedings here, if it's not wanted. I just thought it might be something that would be found useful. No claims were made it was a duplicate of the original parts... just that it is a viable substitute, if you don't have the bucks for the original...

Regards,
Gordon.

Mr. Widget
10-28-2011, 01:28 PM
Please don't go down this road. Hi Gordon,

There was a recent post by another member where he posted his findings about aftermarket kits in some JBL frames. Some were displeased with his posting and the moderators moved it from "Lansing Technical" to DIY... and it started a discussion among a few of us on perhaps adding a "Clone" or "Aftermarket" area to our forum. I think we should do something to encourage this type of work, but it is a specialized field of endeavor.

My attitude a few years ago was "Why screw around with aftermarket parts in an attempt to save a few bucks and risk ending up with something that you don't like." My view today has changed. While in general my point of view is to always try to do the very best possible work regardless of cost and therefore using original JBL parts is the best approach, the writing is on the wall and in the future it is likely that fewer and fewer of our treasured vintage drivers will be serviceable by JBL parts. Fortunately there are a few very good replacement parts out there, Truextent is the only one I am personally familiar with, but I'll take yours and other's word for it that non-JBL replacements can be made to work properly. I realize that in the case of Truextent, the parts actually costs more than the Ti or AL diaphragms that they replace and is a special case, but the point is that going forward we may have no choice but to seek alternatives.

Beyond that I appreciate your popping in to share your experience and hope you continue to do so. That said I do tend to agree with Edgewound and would be surprised if the aftermarket woofer you put together actually performs identically to the JBL at all power levels and in actual critical listening tests. Yes, I believe in measurements and have a great deal of respect for LEAP, MLSSA, and CLIO, but I also know that even doing every test they are capable of will not really tell you how a speaker or driver sounds.

With that said, and getting back on the topic of this thread, did you have a chance to A/B your new woofers with actual JBL 128Hs in identical cabinets? To me that would be the best test, after verifying the measured data of course.


Widget

pos
10-28-2011, 01:50 PM
it started a discussion among a few of us on perhaps adding a "Clone" or "Aftermarket" area to our forum.
Is this going to happen?

IMHO their is nothing sacred about JBL OEM kits: most of them are already made by other compagnies and JBL only specifies procedures and tests...
I would love to see JBL "open source" the specs and QA procedures of NLA kits, and lansing heritage forum would be the best place for such things.

GordonW
10-28-2011, 02:05 PM
My attitude a few years ago was "Why screw around with aftermarket parts in an attempt to save a few bucks and risk ending up with something that you don't like." My view today has changed. While in general my point of view is to always try to do the very best possible work regardless of cost and therefore using original JBL parts is the best approach, the writing is on the wall and in the future it is likely that fewer and fewer of our treasured vintage drivers will be serviceable by JBL parts.

This is one of the primary reasons why a number of us are out there, trying to determine what works, and what doesn't. There is coming a day- and there's not much any of us can do about it, unless we had the money to buy JBL's entire corporate apparatus and bend them to our will- that we will probably not have access to any of the wonderful parts they created in the past...

I saw that other thread... and I would have called that 2202 replacement "unsuitable for the task". That obviously had to sound radically different from an original 2202. That's one example of what does NOT seem to work well. OTOH, this is a case where the differences were pretty benign... there weren't any big "whoop de doos" in the response curve, compared to the original, with the aftermarket 128H kit.

Also, given how many 2213H and 123A-3 frames I see out there dead... it seemed like an interesting concept, to make them useful as SOMETHING. Not even necessarily trying to duplicate an original model exactly- but as something that could be useful in building SOMETHING that sounded good. I think this falls into that category, soundly. And in the case of most of the 3-way JBL cabinets the 128H was originally specified for- most of those didn't run the woofer above about 800 Hz, so the breakup-region behavior isn't as much of a factor in those, as in the 2-way systems with crossover points at 1200 Hz or higher. That's where surround resonances, cone radial and ring modes, and such, start to make much more of a difference. But, for the specified use- the better of these aftermarket kits seem to work well enough, that it's very difficult, if possible at all, to discern them from factory kits, in-system...

IMHO, it's about being able to preserve the products as useful units, after JBL themselves has gone onto other things. Same as the guys who build parts for vintage musclecars and antique planes and such... SOMEBODY needs to keep these things "on the road"!

Regards,
Gordon.

Mr. Widget
10-28-2011, 02:41 PM
OTOH, this is a case where the differences were pretty benign... there weren't any big "whoop de doos" in the response curve, compared to the original, with the aftermarket 128H kit.Yes, but for some, myself certainly... we are drawn to JBL because we seek the exceptional not merely the acceptable. What makes JBL, JBL is in those subtle details.



IMHO, it's about being able to preserve the products as useful units, after JBL themselves has gone onto other things. Same as the guys who build parts for vintage musclecars and antique planes and such... SOMEBODY needs to keep these things "on the road"!Mission of last resort, I suppose. To use your auto analogy, I don't particularly care about "matching serial numbers" though I can understand those who do, but I don't want a Chevy or Ford engine in my Jaguar.

Widget

Lee in Montreal
10-28-2011, 02:56 PM
MWA is not Lansing, therefore out of place in the Lansing product technical section. That's for sure. But I would be pleased to see it in the DIY section as an experimentation around a Lansing product. That would be valuable information. :D

edgewound
10-28-2011, 03:49 PM
Is this going to happen?

IMHO their is nothing sacred about JBL OEM kits: most of them are already made by other compagnies and JBL only specifies procedures and tests...
I would love to see JBL "open source" the specs and QA procedures of NLA kits, and lansing heritage forum would be the best place for such things.

Who are these 'other' companies making JBL kits? 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.

pos
10-28-2011, 04:24 PM
Who are these 'other' companies making JBL kits?
Mogami or Hawley for the C8R2245 (and probaly others)
Brush wellman for the 435Be/2435/476Be diaphragms

edgewound
10-28-2011, 06:01 PM
Mogami or Hawley for the C8R2245 (and probaly others)
Brush wellman for the 435Be/2435/476Be diaphragms

Well...for the record from a few of years ago during an extended conversation with Greg Timbers at CES...Brush-Wellman supplied the Be alloy diaphragm only...at considerable unit cost to them. Harman Manufacturing then built the completed diaphragm assembly.

JBL has NEVER pressed their own cones... spiders and compliances maybe... but has them made to proprietary specs. Voice coils have historically been made by JBL on the high end and pro stuff. There are techniques and adhesives that are used to assemble and treat the compliances that are pretty outside the normal operation of a small reconing shop.

The kit components are then assembled in-house on precision assembly jigs by Harman Manufacturing. Many crossover networks are assembled by outside suppliers....but not recone kits and replacement diaphragms.

lgvenable
10-28-2011, 07:31 PM
If the preponderance of people here really don't care to get this kind of data from me, when I find something I find interesting like this, I can just go away and stop posting again. No skin off my back.
Regards,
Gordon.

Hey Gorden, good to here from you, and I HOPE you keep posting. You're right the day is coming when JBL wil say sorry, and the only choice we might have for our equipment is aftermarket or Great Plains. Their arrogance is astounding to me, I remember when they were the Bee's Knee's.

Personally I appreciate the work done to identify driver parts which are within 10% of oem....I'm not sure my 58 year old ears can hear that kind of difference...

edgewound
10-28-2011, 08:50 PM
Hey Gorden, good to here from you, and I HOPE you keep posting. You're right the day is coming when JBL wil say sorry, and the only choice we might have for our equipment is aftermarket or Great Plains. Their arrogance is astounding to me, I remember when they were the Bee's Knee's.

Personally I appreciate the work done to identify driver parts which are within 10% of oem....I'm not sure my 58 year old ears can hear that kind of difference...

In all fairness to GPA...GPA is OEM Altec-Lansing. It's not aftermarket. Bill Hanushak bought the OEM Altec-Lansing tooling and technology. EVI sold it off.

pos
10-29-2011, 03:03 AM
Since JBL closed its production facility in Northbridge I image there are plenty of JBL people "available" out there that could start something around this... (and maybe even the tooling?...)

edgewound
10-29-2011, 11:53 AM
Since JBL closed its production facility in Northbridge I image there are plenty of JBL people "available" out there that could start something around this... (and maybe even the tooling?...)

R$D is still done here. Large production is done with equipment that has been moved south.

doyall
10-31-2011, 10:38 AM
Please don't go down this road. ...

Seems as though even in light of objectivity many will continue to paint with a broad brush. It surely looks like as long as some/most aftermarket parts are unacceptable, all aftermarket parts will be damned by some without the benefit of testing. I thank you for sharing your findings and hope it will continue. I feel confident that in the not too distant future those very people who now protest will come to appreciate it as well.

4313B
10-31-2011, 11:15 AM
It surely looks like as long as some/most aftermarket parts are unacceptable, all aftermarket parts will be damned by some without the benefit of testing.I think it depends on where someone draws the line.

For example, JBL has a room full of reference standard loudspeaker systems with rotted foams. As far as JBL is concerned they are unrepairable (even with their own recone kits) whereas one of us would buy some Rick Cobb foams, refoam them and go on using them.

I personally like this quote:

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.

JBL knew what they were doing when they engineered their transducers (taken in context of the applicable eras) and they've never been real thrilled with wildly varying standards. They've always liked the "close tolerance" gig.

While I personally have little interest in aftermarket kits for JBL transducers I can see where such activities would fit into the DIY section of this forum. It can be quite enjoyable to mix and match this and that for the sheer fun of it.

speakerdave
10-31-2011, 08:23 PM
I'm with edge on this. Support the remaining kits. Devising and publicizing less costly substitutes will only hasten their demise.

Mr. Widget
10-31-2011, 09:34 PM
I'm with edge on this. Support the remaining kits. Devising and publicizing less costly substitutes will only hasten their demise.I hadn't thought about it in those terms, but that is a good point. If there is a market for factory kits and the bean counters can see them as a revenue stream, they are more likely to continue producing them. We may all be disappointed that Harman in their infinite wisdom have pulled production from Northridge, but I think most of us still feel that the JBL "factory" kits are still best available in most cases.


Widget

ivica
11-01-2011, 01:53 AM
I think it depends on where someone draws the line.

For example, JBL has a room full of reference standard loudspeaker systems with rotted foams. As far as JBL is concerned they are unrepairable (even with their own recone kits) whereas one of us would buy some Rick Cobb foams, refoam them and go on using them.

I personally like this quote:

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.

JBL knew what they were doing when they engineered their transducers (taken in context of the applicable eras) and they've never been real thrilled with wildly varying standards. They've always liked the "close tolerance" gig.
.

As I can understand
"..loudspeaker systems with rotted foams. As far as JBL is concerned they are unrepairable (even with their own recone kits)...."
mean that they can not be repaired under ANY CIRCUMSTANCES, so JBL recone kits are present here just to 'enhance money income".
I can not understand what kind of technology has been applied 30 or 40 years ago, that is not possible to be applied today in order to produce "appropriated" foam or cone, especially if the price of OEM parts is concerned.
That would be understandable if ALL type of drivers are available as spares ( for exchange) with "understandable price", but now it seems that for an example C8R2245 (not to mention driver 2245H), would not be available now or soon. On the other side, we are aware, that the "operation life" of studio monitor is not 10 or 20 years, especially if their drivers are 'power reinforcement ready divers".

So I wonder if now ."..JBL KNOW ..." .concerning : "...JBL knew what they were doing when they engineered their transducers..."
May be some amount "of light" would come from "www.jblselenium.com"

4313B
11-01-2011, 06:36 AM
As I can understandIt isn't real hard to understand. Even JBL with their industry leading tolerances can't return an engineering standard system to spec. It can't be done.

I'm with edge on this. Support the remaining kits. Devising and publicizing less costly substitutes will only hasten their demise.I'm not so sure about that. There are all different kinds of people out there and some of them will pony up the cost of going legit and some of them are going to go with the cheapest solution because they just don't care.

ivica
11-01-2011, 06:51 AM
It isn't real hard to understand. Even JBL with their industry leading tolerances can't return an engineering standard system to spec. It can't be done.

I can understand that the other parts were gone out, not the foam "only", but if the "basket assembly" is in the technical tolerance (mechanical, magnet ,etc), it is difficult to me to understand that "the cone assembly (with the coil+wires...)" is impossible to produce, even if appropriated "re-cone kit" is available. Does that mean that the mentioned re-cone kit is NOT exact replica of the original "cone assembly"?
If that is"the case", what are we buying now for not so small amount of money? Is it "the best EXPECT-ABLE solution" for such amount?

Robh3606
11-01-2011, 07:24 AM
I think we are in a semantics battle so to speak. We have engineering standards where I work. Usually a unit is tested and selected by engineering to be the standard/baseline unit.

Once a unit is picked to be a standard it never gets a finger laid on it again by manufacturing. It becomes a standard until the end of it's life. If we were making speakers and foam fell apart that would be the EOL for that standard. There is no going back.

That doesn't mean or imply there is anything wrong with the re-cone kits. It's just a point of view. From a strict engineering discipline point of view it makes sense. At least to me.

Rob:)

4313B
11-01-2011, 07:38 AM
Thanks Rob :)


If that is"the case", what are we buying now for not so small amount of money? Is it "the best EXPECT-ABLE solution" for such amount?Think of it as buying 5% tolerance instead of 25% tolerance.

Obviously someone in Japan is going to buy the 5% tolerance. And someone in the midwest that found a JBL at a second hand shop or in the dumpster might opt for the 25% tolerance.

timc
11-02-2011, 12:18 AM
I think we are in a semantics battle so to speak. We have engineering standards where I work. Usually a unit is tested and selected by engineering to be the standard/baseline unit.

Once a unit is picked to be a standard it never gets a finger laid on it again by manufacturing. It becomes a standard until the end of it's life. If we were making speakers and foam fell apart that would be the EOL for that standard. There is no going back.

That doesn't mean or imply there is anything wrong with the re-cone kits. It's just a point of view. From a strict engineering discipline point of view it makes sense. At least to me.

Rob:)

I fully agree on this.

The problem if you repair a reference product, is that it might be identical, or it might not. The chance of failure is way higher than the chance for sucsess. So better to get a new reference, with identical specs to the one that died.

ivica
11-02-2011, 01:26 AM
I fully agree on this.

The problem if you repair a reference product, is that it might be identical, or it might not. The chance of failure is way higher than the chance for sucsess. So better to get a new reference, with identical specs to the one that died.

Every think is, for me understandable, only if the production process of "reference unit (units)" is different then the production of the "normal (ordinary)" units.

But my point is not to deal with "reference units", I just wonder, what we, as a ordinary customers can get after "re-coning" JBL units with OEM re-cone kits. Can we expect "acceptable" driver (in accordance to the factory specification) or something that is +/- xx % of unit JBL specification, or only "a good luck can help".

timc
11-02-2011, 03:49 AM
But my point is not to deal with "reference units", I just wonder, what we, as a ordinary customers can get after "re-coning" JBL units with OEM re-cone kits. Can we expect "acceptable" driver (in accordance to the factory specification) or something that is +/- xx % of unit JBL specification, or only "a good luck can help".

But that is what me and others are trying to say. You simply don't know. You can hit it spot on, or you can get something that is way off.

The whole point of a reference is that all production should be withing x% of it. If we then do a repair to the reference and skew the spec with y%, then we would also move the production y% further away from the intended target.

JBL has the reference for their drivers. Others don't. Gordon has obviously hit very close to home with his aftermarket purchase, and that is a good thing for him. But can we trust that if we bought 4 recone kits, that they all would perfom exactly similar?

ivica
11-02-2011, 04:48 AM
The whole point of a reference is that all production should be withing x% of it. If we then do a repair to the reference and skew the spec with y%, then we would also move the production y% further away from the intended target.


Me, personally, do not expect that reference unit has such purpose, I have been expecting that the such unit is present:
1. in order to confirm that under proposed technology process the production line has possibilities to produce the products of expect-able characteristics with some % of their variation,
2.and if something goes wrong (say more then "technology-expect-able"just produced units do not satisfy the proposed specification) the reference unit is "present" to be "easily" compared to the just produced (not satisfied) pieces, in order to find out what is (are) the reason(s) of such (un-expect-able) behavior.

About reparation reference units: may be for JBL it is cheaper to produce a new reference unit then to repair (foam) on EOL (end-of-life) one.

doyall
11-02-2011, 05:03 AM
... But can we trust that if we bought 4 recone kits, that they all would perfom exactly similar?

In light of post #18, the same thing might also be asked of original JBL recone kits.

Thinking back, it seems as though I remember reading at least one post about member reconing a transducer with (presumably) a factory kit and not getting anywhere close to the specified T/S parameters then stating that the reconed transducer was off to eBay.

Which certainly raises the question: When a factory authorized service facility recones a JBL transducer with an original JBL recone kit, does tha factory authorized service facility test the finished product's T/S parameters against the reference standards and if it does and if the finished product does not produce T/S parameters within an acceptable range does JBL furnish another recone kit at no charge and does the factory authorized service center install the second (or third, etc.) recone kit at no charge?

timc
11-02-2011, 07:23 AM
Me, personally, do not expect that reference unit has such purpose, I have been expecting that the such unit is present:
1. in order to confirm that under proposed technology process the production line has possibilities to produce the products of expect-able characteristics with some % of their variation,
2.and if something goes wrong (say more then "technology-expect-able"just produced units do not satisfy the proposed specification) the reference unit is "present" to be "easily" compared to the just produced (not satisfied) pieces, in order to find out what is (are) the reason(s) of such (un-expect-able) behavior.



I believe we are saying the exact same things with different words.

ivica
11-03-2011, 08:30 AM
I saw that other thread... and I would have called that 2202 replacement "unsuitable for the task". That obviously had to sound radically different from an original 2202. That's one example of what does NOT seem to work well. OTOH, this is a case where the differences were pretty benign... there weren't any big "whoop de doos" in the response curve, compared to the original, with the aftermarket 128H kit.

..............And in the case of most of the 3-way JBL cabinets the 128H was originally specified for- most of those didn't run the woofer above about 800 Hz, so the breakup-region behavior isn't as much of a factor in those, as in the 2-way systems with crossover points at 1200 Hz or higher. That's where surround resonances, cone radial and ring modes, and such, start to make much more of a difference. But, for the specified use- the better of these aftermarket kits seem to work well enough, that it's very difficult, if possible at all, to discern them from factory kits, in-system...


s
Gordon.


I think that any good solution with AF kits or parts would be well-come, if nothing more then info. For the bad solution even more. My be you can look at:
http://www.audioheritage.org/vbulletin/showthread.php?31943-K120-re-coned-with-McKenzie-kits&p=322195&viewfull=1#post322195
as an example of bad one, but which is "measurable"

badman
11-03-2011, 04:00 PM
I think that any good solution with AF kits or parts would be well-come, if nothing more then info. For the bad solution even more. My be you can look at:
http://www.audioheritage.org/vbulletin/showthread.php?31943-K120-re-coned-with-McKenzie-kits&p=322195&viewfull=1#post322195
as an example of bad one, but which is "measurable"


One key point. If the assembly matches on thiele small parameters, then it's likely a very good performer in the pistonic range and a perfectly fine replacement. If the woofer is expected to run higher, though, the cone design and materials become more and more important. A 123A/2213 can run up to 5kHz pretty smoothly, due to the heavy lansaplas coating. A cone could mimic it's parameters (high Mms for a 12" would be a key component) with glued weights, but not have nearly the same HF performance.

For big multiway system woofers, if you can match the T/S and coil specs, you're going to be pretty close for 12s/15s under 300hz or so.

ivica
01-30-2012, 12:19 AM
One key point. If the assembly matches on thiele small parameters, then it's likely a very good performer in the pistonic range and a perfectly fine replacement. If the woofer is expected to run higher, though, the cone design and materials become more and more important. A 123A/2213 can run up to 5kHz pretty smoothly, due to the heavy lansaplas coating. A cone could mimic it's parameters (high Mms for a 12" would be a key component) with glued weights, but not have nearly the same HF performance.

For big multiway system woofers, if you can match the T/S and coil specs, you're going to be pretty close for 12s/15s under 300hz or so.

I agree with You, but only all mentioned data can be get from the forum members own experience, because none (on my personal knowledge) of AF-Market producers give such information, and that is why I "call the members of the forum" to inform us about theirs experience, of-course with their acoustic experience too, some technical data would be well come.