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boputnam
09-14-2003, 08:10 PM
I've no clue what to title this, or really where to post it.

The message, though, is worth knowing.

This weekend I re-installed the 2421B's into the 4345's after they were "refreshed" with new Al diaphragms by a very qualified repairman ('cause we're not eligible for getting recone kits or the like... :( ). I didn't expect much change - afterall, they were working "fine". I had already resurround the 2245H's and 2122H's (THAT us pedestrians are still allowed to do... :bs: ), and figured I was mostly there.

WOW!!

Everyone loves to bash the small, 1-3/4 in diaphragm version of compression drivers, and hearing the 4-in series, I too thought :hmm:.

Ignorant.

The change is remarkable. Very smooth, and even - none of the edginess I had tried to EQ around. Changed the entire sound of the 4345's. Man-oh-man. It has opened-up the entire vocal range, added depth and imaging. I cannot overemphasize the improvement.

OK, I'll bottom line it: If you're listening to diaphragms that are over 10- or 15-yrs old, you should get them replaced. Stop thinking this metal does not fatigue, and that long-term use won't affect their response. :bs: (That's twice in one post...).

:thmbsup:

Mr. Widget
09-14-2003, 08:51 PM
Interesting!

Generally the studios do replace them as standard maintenance. It is kind of funny, all the money that people are willing to pay for "Original" 375s.

I'll have to come over with a couple of Heinekens so we can have a listen.:cheers:

Robh3606
09-14-2003, 10:10 PM
Does that hold true for the Titanium too?? I know the aluminum will work harden, I thought titanium was immune from this but anyone have a similar situation where a fresh titanium diaphram was a major improvement??

Rob :)

4313B
09-15-2003, 04:56 AM
Originally posted by Mr. Widget
Interesting!

Generally the studios do replace them as standard maintenance. It is kind of funny, all the money that people are willing to pay for "Original" 375s.
Yeah, nothing like paying top dollar for wore out drivers eh?


Originally posted by Robh3606
Does that hold true for the Titanium too?? I know the aluminum will work harden, I thought titanium was immune from this but anyone have a similar situation where a fresh titanium diaphram was a major improvement??
Titanium is supposed to last considerably longer, especially under stress. Last year I replaced a pair of 044Ti diaphragms simply because the original diaphragms were 15 years old. The new diaphragms are night and day better.

Performance of mechanical transducers degrades until eventual failure. They tend to follow the laws of nature pretty much like everything else.

Don C
09-15-2003, 11:15 AM
I replaced the diaphrams in my 044TI drivers recently as well, as Giskard said, it was a big improvement. I attribute a lot of the change to the replacement of the foam rubber pad behind the dome. That pad seems to be made of a material similar to the foam woofer surrounds, and it rots the same way.

boputnam
09-15-2003, 11:21 AM
Originally posted by Don C
I attribute a lot of the change to the replacement of the foam rubber pad behind the dome. That pad seems to be made of a material similar to the foam woofer surrounds, and it rots the same way. You got that right!

So what did you use as replacement, or where you able to find the exact part number...?

Earl K
09-15-2003, 11:59 AM
Bo


Everyone loves to bash the small, 1-3/4 in diaphragm version of compression drivers,,, Really ???? Where ???? Fighting Words !!!!!:die:

- And here I thought this forum/site was constructed to celebrate and deify Jim Lansings' efforts for designing & bringing to market the 1.75" & 2.88" aluminum diaphragmed compression drivers .

OOPs - wrong turn, :scoot:

<. Earl K

Don C
09-15-2003, 03:15 PM
So what did you use as replacement, or where you able to find the exact part number...?

I was able to obtain the correct parts.

Alex Lancaster
09-15-2003, 08:59 PM
I find the 1.75" drivers fine for home with the 2307/12 horns and 2308 lenses, now it will be the first time I use for HiFi 4"´s, I have 2445's, extra new 2450 diaphs. and some time, I will post my impressions.

Alex

Rolf
09-16-2003, 02:02 AM
Hi all.

Well, what did you all expect? A 15 year old car (with no service) to be in the same shape as a new????

NAAA

Regards

Rolf

Maron Horonzakz
09-16-2003, 06:49 AM
How long would the MYLAR surrounds on RADIAN diaphrams last? Would the 15 yr rule apply?

Maron Horonzakz
09-16-2003, 07:13 AM
Your wrong day old bread breath your not that old your self.

Oldmics
09-16-2003, 07:18 AM
Unless it rains!!!! In which case the Radians that I had (years ago) came apart where the coil is attached to the aluminum on the mylar surface.That was the end of Radians for me in pro applications.To be fair to Radian they say the adhesive problem has been fixed (also long ago),Oldmics

Maron Horonzakz
09-16-2003, 08:07 AM
I dont know either. I guess OLDMIC answere will have to suffice for now. I just thought Mylar would have a longer stress life. I didnt think a glue problem would happen.

Mr. Widget
09-16-2003, 11:06 AM
"I didnt think a glue problem would happen."


Neither did Radian!:D

Tom Loizeaux
09-16-2003, 04:29 PM
How do you think the JBL phenolic diaphragms (1.75") hold up compared to the aluminum ones?

Thanks,

Tom

Ian Mackenzie
09-17-2003, 03:03 AM
Today wile tracking down second hand 2440/41 I discover some interesting facts regards the Alinco drivers.

Thought this might be useful, no doubt most of you are aware of this......

According to a reputable Pro JBL SR installation firm here call Nova Sound, the older Alnico 2440/41 drivers can require re gaussing depending on their age and usage, particularly if the magnet has moved causing a break in the magnetic circuit.

The effect of regaussing is to top up the flux leading to more extended top end from from what I'm told.

The offer I got was a pair of 2441's re gaussed with new JBL Ti diaphragms for Aus $800 the pair (US $500). I have not decided when I will do it but figure better to get the best used article than buyer beware on Ebay.

(This guy has been in design of JBL horns for 25 years and also suggested the 2397 are an excellent device, but need the bigger driver or proper loading, the adapter does not correctly do this for 1 inch drivers.........poohy)

(the Widgets nice carvings are making me horny..muhahahah)



Ian;)

Alex Lancaster
09-17-2003, 06:34 AM
I agree on all counts, Al-Ni-Co (Aluminum-Nickel-Cobalt), degrades magnetically not only with shocks and heat, but also with time, more than ferrite.

The re-gaussing (fancy for re-magnetizing), needs a big electromagnet, and somebody who knows what He´s doing; I posted a thread about this, but nobody could help me.

Alex.

Don McRitchie
09-17-2003, 06:51 AM
Alnico does not degrade with time (it loses about 1% of its energy over a period of many hundred years). Of the common speaker magnet materials it is by far the most immune to heat. Nonetheless, when dealing with older speakers, it is pretty much expected that Alnico drivers will be substantially below their rated magnetic energy. This is strictly because of the instability of Alnico when exposed to large flux modulations.

As anedotal evidence, my web partner Steve Schell has measured the flux density of dozens of vintage drivers. From what he has told me, not one Alnico driver measured at its specified flux density (usually being around 30% down). In contrast, the ferrite drivers all met their specified flux density. This is soley due to the fact a brief exposure to a high power signal can demagnetize an Alnico driver while it will have no effect on a ferrite magnet.

boputnam
09-17-2003, 07:04 AM
Hey, Don...

Widget tells that in his opinion, JBL's first foray into ferrite motors resulted in transducers that to him were sonically inferior to the later iterations. He noted in-particular, the "B" series studio monitors. Later iterations of ferrite seem to equal, if not surpass alnico motors.

Do you, Giskard or others have any fact or mythos ;) to add to this?

Alex Lancaster
09-17-2003, 08:30 AM
Don:

Thanks for the correction, I equated "time", with "use", and guess that even if You do not burn the coil, it could be subjected to very short but high electromag. peaks.

I have learned a lot in the forums in the past few months.


About the "B" series monitors and "H,J" components:

I started with JBL in 1978, I think, which was the transitition time from Alnico to Ferrite, I liked the ferrite better, because usually they handled more power, recently I listened to 4311BWX´s I sold 20+ years ago, and they still sound great for what they are.

Alex.

Ian Mackenzie
09-17-2003, 08:59 AM
Alex,

I recall when leaving High school in 1978 for the big wide world I was a keen JBL addict.

Just as a short step off topic tell us your impressions when starting with JBL back then,

Ian:)

4313B
09-17-2003, 09:29 AM
Originally posted by boputnam
Hey, Don...

Widget tells that in his opinion, JBL's first foray into ferrite motors resulted in transducers that to him were sonically inferior to the later iterations. He noted in-particular, the "B" series studio monitors. Later iterations of ferrite seem to equal, if not surpass alnico motors.

Do you, Giskard or others have any fact or mythos ;) to add to this?
Well, I did have quite a bit to say but then I realized that it wouldn't serve any purpose. Some people are alnico fans and some people are SFG ferrite fans. I guess I'm willing to live in peace with all those alnico-V lovers... :rolleyes:

One thing is for certain. The new alnico structures, with all the SFG ferrite goodies incorporated, are too freakin' cool! :coolness:

Don McRitchie
09-17-2003, 09:49 AM
I'll open the can of worms. I don’t have any technical information to support Widget's assertion. However, I can’t argue preference. The following is what was relayed to me by Greg Timbers regarding the first generation ferrite drivers.

As has been stated numerous times before, the Alnico/ferrite conversion was the result of a crises situation that cut off the supply of Alnico magnets in 1978. JBL was forced to develop replacement magnetic motors in a matter of months. Given the time constraints, JBL specified that the first generation drivers should be identical to the previous Alnicos with the exception of the motors. They would use the exact same cones, baskets, suspensions and coils. In addition, the ferrite motors would be designed to have the exact same magnetic energy of the previous Alnicos so there would be no need to redesign the systems using these drivers.

Greg related that listening tests of the first prototypes to meet the new specifications were an ear opener. They set up A/B tests of existing loudspeaker systems where the only difference was the use of a prototype ferrite bass driver in one and an original Alnico in the other. The bass response of the ferrite driver systems was noticeably different than the Alnicos and everyone agreed it sounded horrible. This led to a major effort to determine what was causing the difference.

Terry Sorenson ultimately identified the issues at play and designed the SFG motor to address them. The primary problem was the ferrite motor’s greater susceptibility to temporary flux modulations caused by the current in the voice coil. The conductive nature of an Alnico magnet means that it acts as a shorted turn to stabilize the permanent field. Ferrite, being non conductive, does not have this property. Terry determined that he could stabilize the ferrite magnets with the addition of a copper ring around the pole piece and this became a core feature of the SFG motor.

The other issue related to the non symmetric nature of the fringe flux above and below the pole piece on a ferrite motor. Because ferrite is a weaker magnetic material than Alnico, it means that a much larger magnet is required that must be housed external to the magnetic circuit. Alnicos generally have the magnet internal to the circuit with the magnet acting as part of the pole piece. The external ferrites have to have an iron core as the pole piece to complete the magnetic circuit. This iron core is permeable to magnetic flux meaning that there is a strong fringe flux field adjacent to it. For overhung coil drivers (the vast majority of bass drivers) it means that the overhung portions of the coil are exposed to a much higher flux field below the gap than above the gap. This results in distortion due to the non-linear response. The solution to this problem was to undercut the pole piece so that the iron core was moved away from the gap.

All of JBL’s first generation ferrite drivers used the SFG motor developed by Terry. According to Greg, they measured better than the Alnicos they replaced and were considered sonically superior. Initially, the new ferrites were designed as one for one replacements of the old Alnico models. The model numbers remained the same, with the change of the letter suffix to H to designate a ferrite driver, Thus the 2205, 2215, 2220, 2231, became 2205H, 2215H, 2220H and 2231H.

With the exception of the 2215H, all of these first generation drivers would be replaced by second generation versions in two to three years. However, the second generation versions had nothing to do with magnet issues. The motors for these drivers were virtually unchanged. The big differences were in suspension design and power handling. The second generation drivers saw the introduction of progressive suspensions that dealt with the issue of dynamic offset (a problem common to ferrite and Alnico drivers). It also saw the introduction of heat resistant adhesives that increased power handling. Thus, the 2235H replaced the 2231H and the 2225H replaced the 2220H and 2205H.

In summary, the first generation ferrites were considered by JBL to at least be the equal (and in some attributes better) than the Alnico’s they replaced. The second generation ferrite bass drivers are considered to be significantly better than the original Alnicos.

P.S. For those reading carefully, it would appear that this post contradicts my previous post regarding Alnico and ferrite’s relative susceptibility to flux modulation. To clarify, high power signals sent through a voice coil in an Alnico motor can generate large flux modulations that can result in permanent, partial demagnetization. A ferrite motor exposed to the same signals would have no permanent effect. However, signals within the normal operating range of a loudspeaker will cause temporary changes in both a ferrite and Alnico magnet’s field strength and this results in distortion. This flux modulation is higher in a ferrite motor than a comparable Alnico motor, unless it is engineered out. The copper flux stabilizing ring of JBL’s SFG motor was designed to do just that to result in lower levels of distortion compared to an Alnico equivalent.

4313B
09-17-2003, 10:15 AM
Originally posted by Don McRitchie
I'll open the can of worms.
Thanks :wave:




I was able to A/B many, many of the alnico systems with their SFG ferrite counterparts and I can't recall preferring a single alnico version.

I was actually so upset about the whole alnico debacle that I was going to snag as many of the 2231A's as I possibly could before their impending demise. Fortunately for me I was taken aside and enlightened and I ended up walking out with only four 2231A's and four brand new 2231H's. After several weeks of goofing around with them all, the alnico's got dumped and I didn't even feel bad about it :) I've never looked back. :p

boputnam
09-17-2003, 12:22 PM
Yes, Don - thanks! :thmbsup:

OK, Giskard, now let's get back to where we were before - gimme the skinny on the favoritism you show (I think... :yes: ) for the LE14A's. They seem to hold a unique position in your AlNiCo experience. :hmm:

Alex Lancaster
09-17-2003, 12:33 PM
Ian:

It is off topic, hope I don't get kicked out of the Lansing C. C.,

It was great!!, at the time S. Harman had sold it to Beatrice Foods, and You would see the big execs., but I really had nothing to do with them; I was 25, and my first real speakers had been some used L19´s that were the greatest, anyway I got into the Disco business, was 2 Years out of Mechanical Engineering, although my specialty was Internal Combustion, and I had hated everything about the required Electricity classes, which I later had a lot of time to regret; Well, I wrote ,no 'net no Fax and the customs broker which I still use his services after 32 Years!, let me use their Telex, 96 Bauds mostly garbled, Ernest K. Wetzig then the main foreign sales guy answered, I went to Northridge to meet him, and there I was, the 2nd Pro dealer for Mexico.

Considering the small volume, I was treated like a king, soon the other dealer went OUB, and I was the only one.

I specially remember very fondly:

Mr. Wetzig for letting me get away with murder, and commercial tips; He even visited Guadalajara.

Garry Margolis for patiently answering my stupid questions.

John Eargle for " " " "

Murray Fancher " " " "

There were others, and You could feel the energy, care and commitment in everything.

In about a Year, Mr. Wetzig said somebody had to take the speaker repair course, which I did, and still have the diploma hanging in my office, that got us a lot of business, I taught 2 guys and were repairing 10 units a day, sometimes.

I got married in 1982, and wanted to use recorded music in a grand scale, so I went to G. Margolis with the floor plan of the church, 18th century and told Him I could get 3Kw of amps and speakers; He said: You need 30w/ch, 2 2205's and 2 2420's!, so I did and the SOTA then was a cassette tape in a TEAC 860, Burwen filter, Phase Linear pre and JBL 6233 amp., lots of people did the same later it sounded great! The cabinets were Altecs and 811 horns w/3110 xovers, a matter of availability on the Altecs.

So, lots of fun, unfortunately in 1982, Mexico went into one of its devaluations/recessions, so I closed the business a couple of years later, by then it was dead.

I hope it wasn't too long winded.

Alex.

For Don: This morning, thinking more about Alnico´s degradation, I guess just having a bar sitting there won´t affect it in 100 years, but with the magnetic poles almost shorted, except for the gap, Wouldn't it degrade sooner?

Alex.

4313B
09-17-2003, 01:48 PM
Originally posted by boputnam
Yes, Don - thanks! :thmbsup:

OK, Giskard, now let's get back to where we were before - gimme the skinny on the favoritism you show (I think... :yes: ) for the LE14A's. They seem to hold a unique position in your AlNiCo experience. :hmm:
Hmmm, I started out with a huge helping of dislike for the LE14A. The LE14/1400 transducer has always seemed to be a real favorite of a certain JBL engineer. Over the years I've come around to feeling the same way but it wasn't really until the LE14H-1 rolled off the assembly line that I started to get with the program. :p I had the concept down early on but I just wasn't willing to give up the excitement of the 15's :)

My all time favorite alnico transducer would have to be the 124A. What a brutal piece of hardware.

Oldmics
09-17-2003, 02:26 PM
Originally Posted By GISKARD "My all time favorite alnico transducer would have to be the 124A. What a brutal piece of hardware." With a hearty endorsement from GISKARD, eBay prices will probably climb to an astronomical level for this driver. Buckle up for the ride.Oldmics

4313B
09-17-2003, 03:11 PM
Originally posted by Oldmics
Originally Posted By GISKARD "My all time favorite alnico transducer would have to be the 124A. What a brutal piece of hardware." With a hearty endorsement from GISKARD, eBay prices will probably climb to an astronomical level for this driver. Buckle up for the ride.Oldmics
K :)
What should we push next week ;)

Don McRitchie
09-17-2003, 04:15 PM
Giskard

Do you know the background of the 124A? I assume it was developed for the 4315, but I don't recall any consumer system that ever used it. I have only ever seen it as an LCS driver. For this reason, I assume they are quite rare.

4313B
09-17-2003, 06:03 PM
Originally posted by Don McRitchie
Giskard

Do you know the background of the 124A? I assume it was developed for the 4315, but I don't recall any consumer system that ever used it. I have only ever seen it as an LCS driver. For this reason, I assume they are quite rare.
Hi Don,

It was the consumer version of the 2203 used in the 4315. It was part of the LCS line and a component in the S21 system. The EN3 enclosure was designed for the S21 system and could be purchased separately. The 121A used in the B212 was the same driver but had a heavier mass ring to create an even heavier moving assembly. The 2202 and 2204 used the same basket and magnetic assembly but had lighter moving assemblies. The 124A and 124H are quite rare.

boputnam
09-17-2003, 06:17 PM
Originally posted by Giskard
The 124A and 124H are quite rare. And will henceforth, be priced accordingly! Ha! :thmbsup:

GordonW
09-17-2003, 07:15 PM
Originally posted by Giskard
K :)
What should we push next week ;)

Ooh! Ooh! LE-10As and PR10s!! LE10s and PR10s!! :D :D :D :D :D :D

Regards,
Gordon.
blatant shill-fishing... :slink:

Don McRitchie
09-19-2003, 01:27 PM
For Don: This morning, thinking more about Alnico´s degradation, I guess just having a bar sitting there won´t affect it in 100 years, but with the magnetic poles almost shorted, except for the gap, Wouldn't it degrade sooner?

To my knowledge, it makes no difference. As the JBL rep indicated, there has to be a break in the magnetic circuit to cause it to demagnetize. One of the magnet company sites I came across stated that that care had to be taken in shipping energized Alnico magnets to ensure that they do not touch. It was not the actual touching that created a problem, but rather the act of pulling them apart. This action was certain to cause a partial demagnetization of both magnets.

Figge
09-21-2004, 05:52 AM
ok i changed my compression drivers in my 4430:s from 2421A with really old alu:s to newer 2425H:s with BRAND NEW ti:s wasnt relly expecting much of a change but.
:jawdrop: HOLY COW!!! uncompareble!



before i had some anoying hars screechy sound going...and it increased as i turnd up the volume!

after i installed the 2425:s i started up my amp and got some music going....it was like a breez of fresh air blew thruogh the room!

4313B
09-21-2004, 06:02 AM
Yeah, it's just a fact of life that they are going to wear out. One nice thing about the 4430 is the relatively low cost involved with maintaining the system.

If you're running Ti then the life of the diaphragms goes up dramatically. Some studios in the L.A. area routinely change out the diaphragms every couple of years, sooner if the engineers hear anything at all amiss.

4313B
09-21-2004, 06:07 AM
Originally posted by Don C
I replaced the diaphrams in my 044TI drivers recently as well, as Giskard said, it was a big improvement. I attribute a lot of the change to the replacement of the foam rubber pad behind the dome. That pad seems to be made of a material similar to the foam woofer surrounds, and it rots the same way. The newer replacement diaphragms also have CCA wire. The original diaphragms would degrade over time due to copper and aluminum not liking each other.

Figge
09-21-2004, 06:13 AM
Originally posted by Giskard
One nice thing about the 4430 is the relatively low cost involved with maintaining the system.

:yes: one other is that the system simply ROCK´N ROLL!

the new diphragms changed the whole sound of the system. when i first got em going i couldnt believe my ears i just sat there staring at the speakers. unbelieveble!


i still look like this! :jawdrop:

paragon
09-21-2004, 06:58 AM
Ok Bo,

I believe it. My 24 years 2441 are only driven at home listening
levels. First i had a pair of 2390, changed after four years into 2397.
Now i bought a pair of 2390 in Ebay and compared to the 2397.
The 2390 sounds very bad.
I never heared this 20 years ago. May be the old dias.
The 2397 make it all smooth compared to the 2390.
Okay, have to buy new dias. But what sort of ?
And what is about cone drivers ?
Is there also a change when you fix new ones in the basket ?
If yes, you have to pay a lot of money to restore your drivers.

Regards
Eckhard

Figge
09-21-2004, 11:28 AM
Originally posted by paragon
Okay, have to buy new dias. But what sort of ?


:yes: buy the original JBL.


And what is about cone drivers ?

i guess they were out eventually too! i have a 20 year old 2235H in one speaker and a brand new in the other.

now with the old dias i couldnt tell a diffrence but now. hell the old sound dead in comarence to the new!

paragon
09-21-2004, 02:32 PM
Thanks Figge,

So, what dias do you will take ?
Alu or the newer titan ?
I put new (australian) aftermarket titans in a pair of 2410`s
and they are going up to 17 kHz (-3 dB).
But they sound not so good as the big 2441.
May be the reason are the small H91 horns and not the dias.
If the aludias fatigue even at low power levels, there is ! a change
in cone drivers also, must be the spider,must be the cloth surround and of course the polyurethan (?) surrounds and
i think must be the cone himself !!
If you have a bass driver which goes up to 1000 or 1200 Hz
you must hear a change to a restored new one.
Nothing will match at all with old bass drivers (tuning),
Because surrounds are to hard or to soft, whatever, you have to tune your enclosure new to get best results.
So you have to change all, not only the high frequency drivers dias.
What do you guys think about ??

Regards
Eckhard

Figge
09-21-2004, 03:26 PM
well...

i had 2421A:s with aluminium diaphragms that probably were 20 years old. i bought new 2425H drivers with titaninium dias. and the change was more than obvious, frekin´marvelous!

but! i guess a new alu had sounded even sweeter!

so go and buy yourself new !JBL original alu for yer drivers. and i guess all will be fine. you wont believe the diffrence until u changed them!!

as for cones: im no expert but as giskard said:

Performance of mechanical transducers degrades until eventual failure. They tend to follow the laws of nature pretty much like everything else.
and my new 2235 is definently more "alive" then the old one. so i guess i have a recone coming my way.


I put new (australian) aftermarket titans in a pair of 2410`s

But they sound not so good as the big 2441.
May be the reason are the small H91 horns and not the dias
could be? or not...u never will know, until u get the "right" diaphragm for that driver.

after all its the diaphragms you´re listening too, not the driver or the horn.

4343
03-02-2006, 08:28 PM
when i first got em going i couldnt believe my ears i just sat there staring at the speakers. unbelieveble!

I was just listening to my 26 year old 2420 and felt the same way!:applaud:

I did change the dia about 20 years ago when it broke while taking it to a gig, (bought a used one from a SR bud for $20...) and yes these 2420's have seen a LOT of SR use, but never with the passive 3122's they came with, always active at 2.5k or above. I only use the 3122's for stereo playback duties, so these puppies still sound great! (I think the alu fatigue must be worse if the driver is run down to the rated XO point of the horn, especilly for SR use.)