JBL 375 vs 2441?

[Earl K]

Hi John

I used to think that JBL lowered the flux level in the gap so that it was more appropriate ( controlled ) for the generation of modal breakups within the newer 2441 diaphragm. Now I'm also inclined to think that JBL was reacting ( at least partially ) to more current information/theory ( for 1978 ) about magnetics and laminar flow theory.

An echo ( or overview ) of that information is nicely articulated in chapter 14 ( Loudspeakers, Enclosures, & Headphones - pages 417 & 418 ) from the "HandBook for Sound Engineers".
The author of that chapter ( Clifford A Henrickson ) states that " as 18,000 G is approached in the gap, the material (steel) starts to look similar to air, and the field becomes divergent. This is known as leakage and makes the gap area look much larger at high flux levels than that of the geometric gap. This increases the required magnet area to operate properly. This whole phenomenon on nonlinear magnetic force and leakage is known as saturation .

So, the partial "degaussing" might also have been a reation to this sort of information. JBL apparently didn't make the magnet any smaller even though that would have saved a bit of money. This implies to me that, that much magnetic bulk had always been required to generate even @ 18000 of Gauss . Perhaps measurement systems had just become more accurate.

One last thought - this was all around that time period when California ( or was it Congress ) passed its' "Truth in Advertising" laws .

regards <> Earl K

[Steve Schell]

Interesting thread, guys. Here are a couple of stray thoughts.

Scott, I think you might be mistaken as to the relationship between the voice coil/former assembly and the inner and outer pole pieces. There should be no physical contact whatsoever between them, and any contact indicates a fault condition. The voice coil and former is supposed to travel in the gap touching only air. When there is contact, which sometimes occurs especially at lower frequencies, a fairly obvious noise results. So, no diaphragm fit should feel tighter upon assembly than any other, except perhaps for the tightness of the positioning pins in their holes in the diaphragm mounting ring. These can sometimes be very tight, and are probably responsible for the tightness you have felt.

My preference is for the 375-2440 diaphragm, with its half roll outer compliance, over the 376-2441 diaphragm with its diamond pleated pattern compliance. My strong suspicion is that the latter achieves its superior measured high frequency response through a series of resonances in the outer suspension. This behavior is good in the measuring, but bad in the listening, as a body in oscillation is not capable of following the input signal very well. The highs from a 2441 do sound more extended to me, but also somewhat "tizzy" and artificial. What is needed for really good top octave reproduction is something like a good ribbon tweeter, which is still operating as a piston to beyond 20kHz. Just my two cents...

[Earl K]

Hi Steve

Always encouraging to hear from someone with a slightly contrary opinion.

My 2 cents of experience in this area is ; After inserting an "inline" suppresion resistor ( equal to the drivers nominal impedance ), And using cascaded HF bypass caps with the approach that their multiple, minute "timing-errors" can actually be utilyzed as a "quasi" D to A reconstruction filter, well - I haven't heard "tizzyness" for quite some time ( unless of course, I change CD players and have to start cap-matching all over ).

Somewhat a bit more seriously; I think I would need to listen to my phenolics for a much longer time to wean my ears away from the sound of metal. I tried that yesterday ( after your posting ) but the spacial "disconnect" I get when a tweeter is added ( I'm just not a tweeter guy ) - makes me switch back fairly fast. And my tweeters aren't junk. I have many ancient Fostex T945N(s) ( the Fostex [Pros'] answer to the 2402 ) plus a friends' 2404s.

Did you ever form an opinion on the sonics of the 475 driver ?

regards < . Earl K

[Hofmannhp]

Hi John,

I know some differences between the 2440 and the 2441.
1.) the 2441 has a "diamond pattern" diaphragma which has a better compliance
2.) the 2441 has 18000 gauss and a silver ring round the pole piece. This may be the reason for the less gauss against the 20000 gauss of the 2440, cause the silver ring is non active for the magnetic field 0.06" beside the gap.
3.) the result is a much better hight frequency range

that means: when using the 2440 you also need a UHF driver like 2402 or 2405, cause the 2441 can do 15kHz with -6dB.
The 2440 is finished with 10kHz with -3 dB.
This difference is remarkable and audible.

Anybody experiances?
Please tell me if I'm wrong.

HP

[Tom Burnett]

My experience essentially mirrors Earl K's. After spending a bundle on 077 tweeters and N-8000 crossovers, they lasted about 3 hours in my 2441-based system. I'm 53, so I couldn't hear any high frequency extension beyond what the bare 2441s provide. What I could hear was the degraded imaging caused by the upper midrange crossover.

To paraphrase Earl K, "I'm not a tweeter kind of guy". Well said. The 2441 is very difficult to beat in my experience used by itself. I think it's hilarious to see the big bucks paid by collectors on Ebay for any driver with "375" on it, when 2441s (or even 2440s for that matter) go for much less money. A 2440, of course, is identical to a 375 except for the paint job. Just my two cents.

Tom Burnett

[JohnH]

I've seen some advocate using a 2441 phragm in a 2440 driver. Can anyone comment on the resulting sound vs. a straight 2440 or 2441?

[Mr. Widget]

Wow!!!!!

I realize that our hearing does degrade with age, and many of us on this forum have played music at levels that OSHA would not be happy with, but loosing the ability to hear the spectrum above 10KHz is a bit scary.

In High School I topped out at 18-19KHz and today, 27 years later I top out just above 16KHz. I certainly am more cautious about high SPLs today than I was back then. I hope to continue enjoying this stuff for many more years.

As for the 077 and N8000. I used that combo about 25 years ago and was never fully satisfied. I blamed the 077. In recent years I have been using a steeper crossover slope at 10KHz and the 077/2405 sounds exceptionally good and I can understand why it has been in continuous production for longer than perhaps any other JBL component.

I would prefer to keep the system simple and in fact tried the 2441 without the UHF driver hoping to run it as a two way, but even with EQ, it didn't realize the top end of the spectrum as I would like.


... and yes the holy grail, the 375 with red wax seals intact... what ever! If the driver was used professionally or even exuberantly in the home it will have a very tired diaphragm and should be replaced. I'll take a remagnetized 2440/2441 with a fresh 2441 diaphragm in it any day over that 375!

As for the simple rolled 2440 diaphragm vs. the diamond edge 2441, I prefer the 2441, but I think application and personal preference plays a large roll in determining which is superior. Both are superior to the titanium 2445 diaphragm in that the aluminum has measurably lower distortion and to my ears at least just sounds better.

JohnH,
Scott Fitlin has advocated the 2441 diaphragm in the 2440. I don't think there is an actual difference between the 2440/375 and the 2441/376. I think the flux differences that are published are due to changes in measurement technique and not due to a physical change. In Scott's case, I would guess what he is hearing is due to differences from one production run to another. This last bit is speculation, but I have not seen any definitive information on the subject.

Widget

[JohnH]

Absent a gauss tester, is there a good way to judge if the expense of remagnification is needed? What do you gain from remag? Higher output? Flatter response? Something else?

[Mr. Widget]

Originally posted by JohnH
Absent a gauss tester, is there a good way to judge if the expense of remagnification is needed? What do you gain from remag? Higher output? Flatter response? Something else?

As you loose flux density your top end will roll off earlier. I suppose in an extreme case output would also lower.

Orange County Speakers will remagnetize drivers for $25 each, so it isn't very expensive, but shipping these massive drivers can be perilous. They should always be shipped separately and I always double box with excessive packing material. If they receive a very strong shock in transit the magnet may shift and the throat can get cracked.

[Tom Burnett]

Mr. Widget wrote:
>I realize that our hearing does degrade
>with age, and many of us on this forum
>have played music at levels that OSHA
>would not be happy with, but loosing the
>ability to hear the spectrum above 10KHz
>is a bit scary.

Losing the ability to hear the spectrum above 10KHz would, in fact, be quite scary. Fortunately, that hasn't happened to me. It just that I'm 53 and I don't hear as high as I did at 15. (As a side point, lots of things don't work like they did when I was 15). The point of my post was the response of the 2441 (usually considered to be approximately 15KHz at the top) is adequate for some people. I just happen to be one of them. At 15, it probably wasn't. If you can hear significantly higher than that, the 077/2405 might be a worthwhile addition. If not, and you aren't a genius at time alignment/crossover networks, etc. it might not.

The 2440/375 tops out at approximately 9KHz according to the published curves at jblpro.com. If you don't need a tweeter with those drivers, it's entirely possible you need a hearing aid. Apparently the point of my post was lost in my wording. I will try to be more careful in the future.

Tom

[LarryS]

After decades of experience with both, here are the basics ...
Most of your opinions are 'spot-on.' The only reason a 375 with seals intact are higher in cost is that they are valuable/original replacements for the famed Hartsfield and Paragon designs (some of JBL's most legendary art-deco models.)

What about sound ??? The 2441 kicks a 375 / 2440's butt ...

Here's how:
Considerably less measurable distortion in frequencies (roughly 500-3K) reducing the honkyness we hear with 375's and superior high frequency response above 8K over most 375 / 2440's.

That being said, here's another issue to ponder ...

Gap tolerances and diaphragm quality control has been all over the map since the 50's. They are almost never what they are supposed to be. JBL and Altec have been guilty of this for decades. It has been my experience (and I have tested over 200+ of these) that if your lucky, 2 out of 10 factory loaded JBL or Altec drivers will spec properly. It is very important to run signal through BOTH of the drivers you are looking to buy before you buy them. Otherwise, you run about an 80% risk of an oddball pair. If your hearing is good, a 2441 pair should remain audible at least to 15K (on both.) As with any model, If they don't match, youv'e got problems.
Personally, I own 2441's. Hope this helps.

[herki the cat]

Hi Steve

Always encouraging to hear from someone with a slightly contrary opinion.

My 2 cents of experience in this area is ; After inserting an "inline" suppresion resistor ( equal to the drivers nominal impedance ), And using cascaded HF bypass caps with the approach that their multiple, minute "timing-errors" can actually be utilyzed as a "quasi" D to A reconstruction filter, well - I haven't heard "tizzyness" for quite some time ( unless of course, I change CD players and have to start cap-matching all over ).

Somewhat a bit more seriously; I think I would need to listen to my phenolics for a much longer time to wean my ears away from the sound of metal. I tried that yesterday ( after your posting ) but the spacial "disconnect" I get when a tweeter is added ( I'm just not a tweeter guy ) - makes me switch back fairly fast. And my tweeters aren't junk. I have many ancient Fostex T945N(s) ( the Fostex [Pros'] answer to the 2402 ) plus a friends' 2404s.

Did you ever form an opinion on the sonics of the 475 driver ?

regards < . Earl K

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Excuse me for butting in five years later; you are probably well aware of what i wish to post, aka: Phenolic diaphragms present excellent driver FS damping not available from metal diaphragms to effectively reduce horn-honk in the crossover spectrum where typical horns present deminishing acoustic resistive loading so necessary to damp the metal diaphragm FS ringing combined with the horn acting like an organ pipe at the crossover. This horn thing is not a problem in a good Movie Theater Auditorium with the magnificient natural dense reverberation in the mid bass spectrum that literally overwhelms minor speaker sonic signatures. aka: annoying sonic artifacts that present problems in the tiny modest-home acoustic environment.

The trade off is that phenolic presents a nice "honk -free" very warm clean sound typicaly all the way up to around 8,000 Hz, where as, the aluminum diaphragm presents a very attractive high end up to 12,000 or 20,000 Hz __thanks to the "mass-break" osillations up there__at the expense of some level of horn honk depending on the driver design. You can, "outfit" the phenolic with the tinkel of a JBL 2405__positively!

Or, Note the example of the superb, very high flux density JBL LE-85 & the professional 2420 big brother, both are honk-free gems when driven by amplifiers with high damping factor.We all do encourage JBL marketing to make available again a few replacement LE-85 / 2420 Aluminum Diaphragms with tangential edge suspension. I dont think this will hurt the new JBL Berylium Driver Market, pas de tout..

As an addtional example for posterity, please note the obsolete WECo 713-B driver with phenolic diaphragm used in the post WW-2 Theater Horns systems & a WECo 753-C two way monitor fitted with a WECo 32-A horn and a companion Jensen ks 12004 bass speaker. I had opted in 1947 for the WECo 713-C driver with the Aluminum diaphragm because i just had to have the 20,000Hz thing & i did regret the horn honk.

What the heck __ who do you want to marry ? __a Blond or a Brunette? They are both pretty darned nice.
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Ce La Vie herki the cat

[herki the cat]

Hi John,

1.) the 2441 has a "diamond pattern" diaphragm which has a better compliance and a silver ring round the pole piece. This may be the reason for less gauss against the 20,000 gauss of the 2440, the result is a much better high frequency range.

2440 is finished @ 10kHz, -3 dB, there is a remarkable and audible difference in 2441.

Anybody experiances? Please tell me if I'm wrong. HP

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I would not say you are wrong__ There are additional considerations__ Aka:the Horn low-frequency cut off should extend at least (1) to (1.5) octaves below the crossover frequency; also, power amplifiers can present drastic artifacts. Every last fragment of driver flux density is required for driver high-frequency response, plus adequate BL for driver FAS damping. This quality was provided in the 1965, superb RCA LC9-A Horn System by the Awesome Honk-Free JBL LE-175 OEM RCA MI-11419 Driver.

Also, quite frequently, component performance reports, including speaker cable comparisons, are frequently presented with no clues as to of what equipments exist in the entire audio system chain, any one of which can contribute artifacts that can upset the system spectrum balance: for example, a heavy sound imbalance due to poor speaker damping in the mid bass spectrum, which will benefit from the extended high frequency tinkel of __say "the 2441" to the disadvantage of the more pure, lean sound of the 2440.

In comparing 2441 & 2440 diaphragms it has been stated that 2441 diaphragms sound better in the 2440 motor, than the 2441 motor__of course with the 20,000 gauss flux density of the 2440 motor. It has also been stated the 40 year old 2440 diaphragm was inferior to the 2441 diaphragm in both the 2441 and the 2440 motors.

Recently, John Eargle's comment has surfaced stating "that old beat up" aluminum membanes do have a memory of considerable microscopic cumulative bending, thousands of times per second, a history that "work-hardens" the delicate aluminum, increasing the metal stiffness, and severely degrading the sound performance ultimatelly rupturing the diaphragm.

After having my 2440's finally re-mag'ed to full 20,000 gauss, also equipped with new JBL 375 diaphragms, & mounted on"Honk-Free" RCA MI-9595 Radial Horns with cut-off of 250 Hz, driven by WECO 91-A single-ended 300-B amplifiers that have some 15 db negative feedback providing adequate damping factor, i experienced Steve Schell's preference for the 2440 clean stunning "you are there sound" Aka: the important "Germ & Body" of the Sound, for which, 10,000 Hz top__ is more than adequate; You can of course, add a good, superb ribbon tweeter if you wish to hear the shimmer of the brushed cymbal & the rosen on the violin bow.

SS[Quote, Steve Schell]=01-08-2004 03:30 PM Post/this thread. "My preference is for the 375-2440 diaphragm, with its half roll outer compliance, over the 376-2441 diaphragm with its diamond pleated pattern compliance. My strong suspicion is that the latter achieves its superior measured high frequency response through a series of resonances in the outer suspension. This behavior is good in the measuring, but bad in the listening, as a body in oscillation is not capable of following the input signal very well. The highs from a 2441 do sound more extended to me, but also somewhat "tizzy" and artificial." [Quote/]
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Cheers herki the cat

[kftool]

Hi all,

It's been 20 years or so since I had horn loaded speakers, E V Patricians. Since then I've built only line sources but always wanted to revisit a 375 based system. Last week I bought a 375 driver and last night a pair of 2441 units.

I've read as much as I could find on the various horns used with the above mentioned drivers. I thought of just buying a 537 509 horn lens assembly from Audio Classics but the wooden horns, Smith, Westlake and TAD mentioned are intriguing. I am a pattern maker and building any of the wooded horns would not be a problem as I have the machines to accomplish the task. The question is, which one to build.

I realize that listening to each design would be the best but it won't happen. I plan on using a pair of LE 15 A drivers along with an 075 tweeter with the center of the horn around 40 inches above floor level.

These speakers are an experiment so if they don't work out I won't be suffering sonically.

I realize that new posts to this thread are far and in between and I may be dead before I read one. If you have any opinions, a copy to my email address would be appreciated, if this site allows it. kftooldesign-at-comcast.net

I appreciate your thoughts. Ken Fritz, Richmond, Va.

[tomee]

Being a pattern maker, you could probably build any of these:
http://www.geocities.jp/arai401204/H..._Speakers.html

here's the download page with profile drawings:
http://www.geocities.jp/arai401204/D.../Download.html

(You might want to remove your email and full name from the post.)

Hi all,

It's been 20 years or so since I had horn loaded speakers, E V Patricians. Since then I've built only line sources but always wanted to revisit a 375 based system. Last week I bought a 375 driver and last night a pair of 2441 units.

I've read as much as I could find on the various horns used with the above mentioned drivers. I thought of just buying a 537 509 horn lens assembly from Audio Classics but the wooden horns, Smith, Westlake and TAD mentioned are intriguing. I am a pattern maker and building any of the wooded horns would not be a problem as I have the machines to accomplish the task. The question is, which one to build.

I realize that listening to each design would be the best but it won't happen. I plan on using a pair of LE 15 A drivers along with an 075 tweeter with the center of the horn around 40 inches above floor level.

These speakers are an experiment so if they don't work out I won't be suffering sonically....