"Worst refoam job EVER" -rescue project

[Flodstroem]

hello

Does anyboby remember a thread from our friend Wsilva
"Worst refoam job EVER"

This image was attached to his post (a picture of a severe refoamed 136A
)

[Steve Gonzales]

It's a tie if anything

[Flodstroem]

Now, I got te opportunity to re-cone this pair 136A. This meant I had to cut away the old cone assambly and so on.

I started to cut avay the "foam super heavy delux micro bass" When finnished with that job (guess what a job, 4 different type of glue) I could see the cones was pretty fine and there was absolutely no rubbing scraping or other bad sounds from the voice coils.

I started to thinking re-foaming instead of re-coning.
To make this storie not to long, this was the results after that "thinking"
A rescued pair of 136A

a close-up of new foam:

[Steve Gonzales]

You are good!

[Flodstroem]

And this is a close-up of one of the two speakers
regards

[Earl K]

Very Nice Flodstroem

I truly think that you have "Mastered" this refoaming technique .

I'm glad to see all this restoration effort going on .

Now I'd like to see you "create" a new HiFi speaker out of available R&R stock.

Take (2) 2225s / cut out the linen surround / install Rick Cobbs' foam surrounds and you have created a 137H ( my designtion for a 136H without the "mass-ring" ). This would be the shorter coil predecessor to a 2234H .
( Fs ?, maybe in the 26 to 31 hz range )


EarlK , ( "Living vicariously" through all your efforts )

[Alex Lancaster]

And I thought Earl was an Ultra-Purist

[Earl K]

And I thought Earl was an Ultra-Purist

Ha, Ha, Ha,

I guess I forgot to take my "politically correct pills" this morning .

[Steve Gonzales]

What did you use to remove the GUNK? MEK?

[Flodstroem]

Hello all, thanks for comments
Yes Earl K I will fix that, send parts to me and we will see what I will come upp with. Kidding, I live in Norway and it will be an expensiv shipping.

When looking in the JBL T/S parameter list I can see the cone assamblys mass is 105grams. It is slightly heavier than the LE15/2215 cone assambly.
Taking that to account a new 2225/foam surounder would have a new Fs in the order of 23-27 Hz not as high as you thougt. This is only a guessing based only to the 2225´s moving mass. If 2225 magnet have a higher Tesla (stronger magnet motor) than the LE15/2215H, and a stiffer spider then Fs could be as high as you propose.

Regards

[yggdrasil]

Very nice job.

Rålekkert.

[transducergeek]

Very nice job.

Rålekkert.

Is is "Rol-eh-Curt?" or? I am born/raised California, and know nothing of the Norge lingo.... I assume it means, "excellent" or "great"... ? Thanks.. Rolf E.

[Flodstroem]

But back to the interesting 2225 Earl K Sub ("2225EKSub")

Earl K, the specs 1.2 Tesla and 0.9 Tesla you mention is from (I guess) the JBL´s T/S parameter list. This spec is given to the "flux density"(eg. Tesla or Gauss), not the "total magnetic flux" (eg. Maxwells or Weber) which was what I meant but couldn´t explain so clear.

Its means it is not for sure that the total magnetic flux in a 2225 is higher than in a LE15/2215 (H). The magnetic assembly differs (only?) in the top plate thickness. (if compare 2225H with a 2215H) what I can see. Thats also why the higher "flux density" in the 2225´s magnetic gap.

I think the total magnetic flux is the main factor which controls the Fs in a speaker. Maybe Giskard is the person who knows anything about the magnets in these speakers ?

This mean the only differance between the 2225 and the LE15/2215 (H) is mass of cone and stiffness of spider, if we dont count legth of voice coil, or turns or cone materials and handling power (if I´m not totaly wrong).

Heavier cone mass will (maybe) out-balance the stiffer spider in the 2225. I think we will end up with a loudspeaker that has an Fs narrower to the 26 Hz value rather than the 31 Hz value (which is a big differance compared to the original Fs at 40 Hz).

(D..n, I would like to test this. I have foam surrounds but I dont have any 2225 in stock . )

This "Rålekkert" was from my Norwegian friend and was a litle bit of off topics, but any way, Thank´s.

Regards

[Earl K]

Hi Flodstroem

Earl K, the specs 1.2 Tesla and 0.9 Tesla you mention is from (I guess) the JBL´s T/S parameter list. This spec is given to the "flux density"(eg. Tesla or Gauss), not the "total magnetic flux" (eg. Maxwells or Weber) which was what I meant but couldn´t explain so clear.

- Yes, you're right. I'm aware that "flux density" is only part of the electromotive equation. I haven't seen comparitive figures ( for a 2225 vs a le15 ) of "total magnetic Flux" . ( Maybe I haven't looked hard enough ). I usually consider the overall "BL" figure as a good generalized term that has accounted for the "total Magnetic flux". But I realize that it (BL ) is also not the full story. Two speakers with identical BL figures but vastly different gap topologies will usually have different "sonic characters" .

Its means it is not for sure that the total magnetic flux in a 2225 is higher than in a LE15/2215 (H). The magnetic assembly differs (only?) in the top plate thickness. (if compare 2225H with a 2215H) what I can see. Thats also why the higher "flux density" in the 2225´s magnetic gap.

I do find the top plate thickness a significant contributing factor to "resolution" / everything else being equal . The ME150h woofer is a good example of that.

I think the total magnetic flux is the main factor which controls the Fs in a speaker. Maybe Giskard is the person who knows anything about the magnets in these speakers ?

I agree, in the last 15 years, JBL has increased the thickness of their top-plates for their newer generation speakers ( while maintaining similar BL figures ) . There has also been a small rise in Fs and an increase in midband output . I happen to really like these developments - others may view them as a waste of extra magnet weight & polished steel . These speakers do come with extra resolution - whether the market responds positively to JBLs' gamble / still remains to be seen.

[Flodstroem]

Yeah Earl K The "new" generation of JBL bassdriver with a thicker top plate is exiting, but new ehhh? (only the mechanical assambly is different not the idea is it?)

My 2215H pair is not any newer but merely a vintage speaker. But what a speaker. It think it is a better model then the older LE15/2215. Its sound is a litle bit more distinct than their predecessors, you could say "faster" to responding to transients in the bass music drums etc.

Hope I soon could start to build my TL speakers with these speakers as subs
eg. the speakermodel will be a ML TQWT, Mass Loaded Transmission line Quarter Waveleght Tube based on an idea of Mr Martin King (I think). But now we are at a new thread isn´t we (ok, I mean -me).

BTW, It is to bad that the new generation subs not is on the market and available to home speaker builder (like you and me?)

Wander how big the differance would be between the 1500AL and the 2215H