Does anybody know the M32-8, 15"? Recone to 2235H question...

[Ralf]

I have an old JBL M32-8. Is it possible to recone it to a 2235H?

It looks like a E-130...


Maybe Giskard knows it?


Ralf

[Ralf]

here I found some infos:

M32-8 (http://www.jblproservice.com/pdf/Goes%20Into%20List/03%20Goes%20Into%20List.pdf)

the reconekit C8RE130 is the reconekit for both speakers (E-130 AND M32-8)

The E-130 is reconeable to 2235H, so my opinion is, that the M32-8 is also reconeable to a 2235H. Can somebody confirm this?

Ralf

[Mr. Widget]

I don't know a thing about the M32-8, but the E-130 is not exactly the same as the 2205H, 2225H, 2231H, 2235H cores as the E130/ E140 have a slightly larger magnet and greater flux density. This will reduce deep bass output and increase upper bass/low mid slightly. The audible differences will probably be very subtle.

Widget

[Ralf]

I have both here, a 2225H and a E-130, but visually the magnet looks like the same. The Weight of the magnet is in both Versions 8,5kg (18 5/8 lb).

But you are right, the flux densitiy is 1,35 T for the E-130 and 1,2 T for the 2225H/2235H.

I`m a little bit confused about the connection of the flux density and fs. We have messured out an old Alnico K-130 reconed to 2235H.

We stated that fs shifted itself approx. 5 cycles per second upward in the comparison to the original 2235H Alnico. The reason for it is the leaving magnetism with Alnico magnets. Accordingly a higher Tesla value would have to mean a frequency shift downward???

Can you explain, why a higher Tesla reduce the deep bass? I I am something confused...


Originally posted by Mr. Widget
I don't know a thing about the M32-8, but the E-130 is not exactly the same as the 2205H, 2225H, 2231H, 2235H cores as the E130/ E140 have a slightly larger magnet and greater flux density. This will reduce deep bass output and increase upper bass/low mid slightly. The audible differences will probably be very subtle.

Widget

[Guido]

Why don't you grab your phone and ask your old friend?

E Series magnet is 22,23mm thick
22xx series magnet is 19,05mm thick

Measure it.

We will meet this week for a reconing session anyway (I hope)

:cheers:

[Hofmannhp]

Originally posted by Ralf
I have both here, a 2225H and a E-130, ....

Hi Ralf and Guido,

I have also two de-coned E130 (Alnicos) slowly gettin dusty and think about to recone them to 2235.
The JBL fit list tells me that this works.
where do you buy your 2235 cones?

HP

[Mr. Widget]

I`m a little bit confused about the connection of the flux density and fs. We have messured out an old Alnico K-130 reconed to 2235H.

We stated that fs shifted itself approx. 5 cycles per second upward in the comparison to the original 2235H Alnico. The reason for it is the leaving magnetism with Alnico magnets. Accordingly a higher Tesla value would have to mean a frequency shift downward???


Can you explain, why a higher Tesla reduce the deep bass? I I am something confused...

Essentially as you increase the magnet strength it is a similar effect to lowering the mass of the cone. The associated TS parameters will shift accordingly. I would assume the K-130 with an alnico magnet would measure and sound closer to the E-130 than it would to the 2235 if we were comparing all three with the same cone kit in them.

Guido is correct in that the E-130 and E-140 are slightly deeper than the 22XX 2205H, 2225H, 2231H and 2235H frames. The 2220H frame however has an even larger magnet and is even deeper than the E-130 and E-140.

[Guido]

HP I'll PM you with details;)

[Ralf]

Ok. that`s clear. But why we got a higher fs with older Alnicos??? Where is the failure? We should get a deeper fs, or?



Originally posted by Mr. Widget
I`m a little bit confused about the connection of the flux density and fs. We have messured out an old Alnico K-130 reconed to 2235H.

We stated that fs shifted itself approx. 5 cycles per second upward in the comparison to the original 2235H Alnico. The reason for it is the leaving magnetism with Alnico magnets. Accordingly a higher Tesla value would have to mean a frequency shift downward???


Can you explain, why a higher Tesla reduce the deep bass? I I am something confused...

Essentially as you increase the magnet strength it is a similar effect to lowering the mass of the cone. The associated TS parameters will shift accordingly. I would assume the K-130 with an alnico magnet would measure and sound closer to the E-130 than it would to the 2235 if we were comparing all three with the same cone kit in them.

Guido is correct in that the E-130 and E-140 are slightly deeper than the 22XX 2205H, 2225H, 2231H and 2235H frames. The 2220H frame however has an even larger magnet and is even deeper than the E-130 and E-140.

[Mr. Widget]

No that is right, the K130 as well as the E130 should have a slightly higher Fs.

[Ralf]

Hi Mr. Widget,

the Tesla value of the K-130 is the same as the 2235H Alnico version (in older 43xx Series) and the same as in 2235H Ferrit version: 1,2 T

Why I got a higher fs with the same value? The reason we believe is the decrease of the magnetism of alnico materials. I don`t understand the connection...

Summary:

1) the same origin Tesla value should result in same fs for all possibilities of combinations

2) we got a higher fs with older alnico magnets

3) if we recharge these alnicos, we should get the origin results of fs for 2235H

4) if we have larger magnets, we get a higher Tesla value

5) so we should get a deeper fs with higher Tesla values

6) I know that I know nothing

7) Why?

8) with larger magnetic flow density of the permanently magnet one needs fewer ampere to move the same mass

9) the same ampere with higher magnetic flow densitiy can move more mass

10) the acceleration of the cone is larger with same mass, same ampere, higher magnetic flow density

11) the fs should be deeper with higher
magnetic flow density...

12) Where is the mistake in reasoning?

Ralf


Originally posted by Mr. Widget
No that is right, the K130 as well as the E130 should have a slightly higher Fs.

[Mr. Widget]

You got me I was lazy and didn't check up on the old K series and assumed they were the same as the E series. As far as differences that you have measured between the K-130 recone and the 2235... I would put my money on lot to lot variation over demagnetization.

But now that we are on the subject, did anyone ever notice that while the K-130 does indeed used the same structure as the 136A the pro variant, the 2231A, used a slightly larger magnet return casting. JBL claimed the 136A to be identical to the 2231, but in fact they are slightly different. You can even see it in the L-300 brochure in the cut away photo.

Any ideas about that one.

Widget

[4313B]

Here's what I get with flux and mass changes:

[4313B]

"But now that we are on the subject, did anyone ever notice that while the K-130 does indeed used the same structure as the 136A the pro variant, the 2231A, used a slightly larger magnet return casting. JBL claimed the 136A to be identical to the 2231, but in fact they are slightly different."

Yes, I've owned all three. I have no idea where that "goofy" magnetic structure on the 2231A came from. We could probably find out if it's that important. The 2231A and 136A are functionally identical, as would be a K130 or K140 with the old C8R2231 cone kit installed.

[Ralf]

Originally posted by Giskard
Here's what I get with flux and mass changes:

Thanks for the infos, Giskard.

Can you hear a difference between the 1,2 and the 1,35 T Versions? More Mids? Or is it not visible?

[Mr. Widget]

Originally posted by Ralf
Thanks for the infos, Giskard.

Can you hear a difference between the 1,2 and the 1,35 T Versions? More Mids? Or is it not visible?

Ralf,

I have a pair of 2235 cones in 130E baskets. I have not done a direct comparison with my actual 2235s but they seem very similar.

I did plug in the numbers that Giskard posted into BBPro 6 and it appears to agree with what I would expect from my "seat of the pants approach". Essentially the response with the stronger magnet gives slightly less output below 90Hz and slightly more output above 100Hz. It wouldn't surprise me if these differences were within normal production variation.

Widget

PS. Giskard, if you could ask around about the 136A vs 2231A castings I would love to hear about it. I can't imagine that they measure exactly the same... they probably sound the same though.

[Ralf]

Originally posted by Giskard
Here's what I get with flux and mass changes:

definitly Summary:

1) a greater Tesla value results in smaller Qes

2) a greater Tesla value results in smaller Qts

3) with a greater Tesla value you get more power compression

4) you will get lower deep bass (not vissible, but maybe -1dB)

5) you will get higher mids (not vissible, but maybe +1db)

6) the fs is the same

open questions:

1) Why the fs is different in the alnico version (basket K-130, result +3Hz)?

2) can you hear a difference between the baskets (different Teslas, different magnetic materials)?

3) we should make a table of content of Thiele-Small-Parameters with all possible baskets reconed to 2234H/2235H for a real comparison. What you think about?

4) different Thiele-Small-Parameters needs different enclosures. Is it really comparable?

Ralf

[Guido]

Originally posted by Ralf
definitly Summary:


open questions:

1) Why the fs is different in the alnico version (basket K-130, result +3Hz)?
Ralf

I think at least this is not significant as I measured ceramic 2235 from 18Hz to 22 Hz fs. Think its production tolerance.

[Mr. Widget]

I will second that.

Did you measure the alnico after it was well broken in? The Fs does change with break in.

Widget

[Ralf]

Originally posted by Mr. Widget
I will second that.

Did you measure the alnico after it was well broken in? The Fs does change with break in.

Widget


I bought the speakers from Guido. Don`t know, if they have ever seen real music...that`s a possibility.

Ralf