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Thread: alnico/ferrite drivers

  1. #1
    Figge
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    alnico/ferrite compressiondrivers

    ok! this has probably been nagged about before but here we go!

    i was just wondering about the diffrences between the 2421 (alnico) and say the 2425 (ferrite) sound?. the cores i mean.
    should i expect higher performance with the 2425 core?

    i heard the diffrence between the 116a alnico in l-19 and the 116h in 4301b. it was like day and night. ok not the exact same cabinets but...
    Last edited by Figge; 07-27-2004 at 01:21 PM.

  2. #2
    Administrator Mr. Widget's Avatar
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    I am also curious about this. Maybe someone out there could compare a LE85/2420 motor with a 2425 motor using the same diaphragms. It would also be interesting to compare the 375/2440 or 2441 motor with the 2445 motor sharing diaphragms. I don't know if anyone has done this, but it would be great if someone could do these comparisons both subjectively (listening) and objectively by measurement.

    Widget

  3. #3
    Webmaster Don McRitchie's Avatar
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    There shouldn't be a significant difference, if any, assuming that the throat and phase plug geometry is the same in both the ferrite and Alnico versions. I believe this is the case with the 2420/2425 and 2440/2445, but this is worth checking. Of course the big issue that will have to be checked is whether an Alnico, used for comparison, still meets the factory specs for flux density.

    In bass drivers, there is a difference is sonic character because of differences in flux modulation and temperature curves of the different magnetic materials. In a compression driver, the coils are generally underhung so that flux modulation is mitigated to low levels. The lower power handling of compression drivers results in lower operating temperatures so that the temperature curve difference has minimal effect. Nonetheless, I would be interested in the results of any experiments.
    Regards

    Don McRitchie

  4. #4
    Figge
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    ok since i now have both the 2421A:s and the 2425H:s i could step up to task of testing this. diaphragm that gonna be used is new 8ohm titanium.

    one question though: the 2421 are pretty old and alnico, can it have gotten demagnitized?


    widget: its only gonna be a listening test so far, as i have no messuring equipment.

    the 2425:s are mounted now and im gonna listen to them for a while, get to know them. and then swap, and listen for a while.

    a while = couple of days? weeks? idunno.
    Last edited by Figge; 09-22-2004 at 04:17 AM.

  5. #5
    Maron Horonzakz
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    I have a pair of LE 85 drivers with Ti diaphrams . The units were sent back to JBl for gap rework & remagnetizing. They sound fine. I dont know what the units would sound like if I would put the aluminum diaphrams back in . the gaps are now different.

  6. #6
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    the gaps are now different.


    Really ? Someone at JBL told you this ? Did they say what they now are ?

    <. Earl K

  7. #7
    RIP 2010 scott fitlin's Avatar
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    Alnico vs ferrite vs Neodymium!

    I say you can hear differences between different magnetic material! My latest exploration of this was the TAD 4001 ( alnico ) vs the TAD 4002 ( neodymium ) and both use the exact same diaphragm, but sound so very different from each other!

    The JBL 2441 vs the JBL 2445! Another buisiness down here that has big sound used the 2441J and switched to the 2445J. Ron didnt care for them, and put the 2441 diaphragms in the 45,s! Still they didnt sound like the 2441,s! I heard it, he heard it, and his sound engineer heard it!

    The JBL 2402,s! I have some alnico 2402,s and when I got them had them rediaphragmed, and sent em to JBL for a remag! I have A/B,d them against my 2402H and can hear difference between the two types! The alnico bullet seems to have a finer sounding top end, more jingly and airy, while the ferrite 2402 has that raspier sound, Tss Tss Tss! But i can always hear a difference between the two types! Im not saying you cant get ferrite drivers to sound good, they can sound great, but I can hear a difference between the magnet types!

  8. #8
    Administrator Mr. Widget's Avatar
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    Hi Scott,

    I really doubt that the magnetic material itself is the cause of the differences you are hearing.

    In the case of the TAD 4001 vs. the TAD 4002 you are correct that they both use the same diaphragm, but they have different phase plugs and different throats. TAD also makes the 4003 with neodymium and I think it is slightly better than the alnico 4001. It is a completely different driver though so it isn't a proper comparison.

    In the case of the 2441 vs. the 2445, I believe they have different throats and different phase plugs so once again a direct comparison isn't possible. I do find it interesting that with the same 2441 diaphragm, the 2441 driver is preferred. I have not made this comparison, but would like to at some point.

    I can't think of any reason that different magnetic materials by themselves should make a difference sonically in a HF device. I haven't noticed a sonic difference when comparing alnico 077s and ferrite 2405Hs. When dealing with these minute details the power of suggestion can be huge. Have you tried your comparisons in a blind or double blind scenario?

    Widget

  9. #9
    Maron Horonzakz
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    Earl K.......Well they shure the hell sent me a bill for for that service.

  10. #10
    Maron Horonzakz
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    Widget.... If you look at the cutaway drawings in the TAD catalog The 4001 & 4002 Have the same diaphram & the same phaze plug design. Its the magnets that are different plus the flux levels are different.

  11. #11
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    Hi Maron

    I'm just curious . I certainly believe JBL "regapped" the le85(s) , along with remagnetizing them . But to me, "regapping" is essentially "recentering" all the top-plate parts to achieve the best symmetry for the 2 circles. Somewhat "simplistically" like having a car engine "blueprinted" .

    This process shouldn't preclude the use of older diaphragms - unless I'm missing something here .

    regards <. Earl K

  12. #12
    Maron Horonzakz
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    Earl k......I guess I could replace the diaphram in one LE 85 to the old unit to see if it drops in output a skoshe. I just assumed it would. If its only a db I won,t hear it. I dont know if a rat shack meter could show this.

  13. #13
    Administrator Mr. Widget's Avatar
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    Originally posted by Maron Horonzakz
    Widget.... If you look at the cutaway drawings in the TAD catalog The 4001 & 4002 Have the same diaphram & the same phaze plug design. Its the magnets that are different plus the flux levels are different.
    I just took another look at the catalog, and I can't be sure the phase plug or throat are the same or not. Are you certain they are the same?

    The 4002 is a "low cost" alternative to the 4001. It seems strange that if the goal was to recreate the 4001 at a lower price point, using the same diaphragm, phase plug, and throat dimensions, that they would change the flux density. It certainly could be the same as the 4001 if they wanted it to be. I did notice from looking at the drawings that the rear chamber of the 4002 does seem smaller than the 4001. This would affect performance.

    Other than looking at the catalog I have no experience with the 4002 driver so I can't say anything about it's sound, but for their top of the line driver they chose to once again use neodymium and from my experience it does indeed surpass the alnico 4001.

    Slightly off topic, JBL has used alnico for their top of the line 1500AL woofer and yet gone with neodymium for it's companion mid and HF drivers. Further off topic even further still for JBL's slightly more cost effective alternative drivers to the beryllium diaphragmed 435Be and 045Be, they went with aluminum instead of Ti.

    If anyone has a theory or an actual explanation as to why they think alnico may be superior to Fe or neodymium, I am all ears.

    Widget
    Last edited by Mr. Widget; 09-22-2004 at 06:29 PM.

  14. #14
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    Hi Maron

    If you're not comfortable with recentering replacement diaphragms ( you need some test gear ) then I wouldn't recommend you mess about with what you got back from JBL . On the other hand, if swapping diaphragms in & out of magnet structures is second nature to you - then it would be interesting to hear about your impressions, of old versus new.

    regards <. Earl K

  15. #15
    RIP 2010 scott fitlin's Avatar
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    Well......

    Originally posted by Mr. Widget
    Hi Scott,

    I really doubt that the magnetic material itself is the cause of the differences you are hearing.

    In the case of the TAD 4001 vs. the TAD 4002 you are correct that they both use the same diaphragm, but they have different phase plugs and different throats. TAD also makes the 4003 with neodymium and I think it is slightly better than the alnico 4001. It is a completely different driver though so it isn't a proper comparison.

    In the case of the 2441 vs. the 2445, I believe they have different throats and different phase plugs so once again a direct comparison isn't possible. I do find it interesting that with the same 2441 diaphragm, the 2441 driver is preferred. I have not made this comparison, but would like to at some point.

    I can't think of any reason that different magnetic materials by themselves should make a difference sonically in a HF device. I haven't noticed a sonic difference when comparing alnico 077s and ferrite 2405Hs. When dealing with these minute details the power of suggestion can be huge. Have you tried your comparisons in a blind or double blind scenario?

    Widget
    In the case of TAD I was able to borrow two 4001,s and I could hear distinct difference between the 4002 and 4001. I preferred the 4001, better upper midrange! But still i prefer the sound of the JBL 2441!

    For the tweeters, I had one day, about three years ago while my dad was still running things with me, put up one cluster of four that I have with all four tweeters in that array being 2402 alnico bullets! The other three arrays were our 2402H. I played music for a bit, and about an hour into this my dad comes into the place, and said system sounds pretty good! he aksed me if I had his Yanni CD, which I did, and I played stuff from it for him. And he comes over to me, and asks me how come the tweeters over there sound better than the rest? I ask him, what do you mean? he tells me those sound better, cleaner, more top end, sounds like they go up higher than the others, and the others are kind of raspy! I say cant be! But I hadnt told him anything, or that those werent OUR bullets. I play more music, he keeps telling me Those sound better! Finally I tell him those are different ones, not ours! Same basic tweeter, same diaphragm, different magnet. He didnt know they were different, but he heard something different. This would be, to me, about as double blind as you get!


    The TAD 4002! heard em at a show, heard em in a pro rig, wasnt sure if i wanted the 4001,s or 4002,s! TAD wholeheartedly recommended the 4002 OVER the 4001, other pro sound guys also recommended the 4002! I bought six! Installed them, didnt like em, did everything, EQ, change amps, crossovers, crossover slope and points, just couldnt get what I wanted or expected from them! The 4001 is a superior sounding driver compared to the 4002, IMHO! Went back to my JBL 2441, and It sounds good. You know I really wanted to love the 4002, after spending THAT much money its hard to swallow that I made a mistake! But I did! I glad I held on to my JBL 2441,s though!

    Supposedly, the phase plug is the same in both the 4001 and 4002, yes the throat is different, and this could be what I hear, but to me the 4002 reminded me somewhat of the JBL 2450J, also not on my LIKE list! Beryllium diaphragms being the same, a major difference in tonality!

    These days I say specs, schmecks, I use my ears! if I like it, I like it, and I dont care WHAT makes it do what I like as long as I like it!

    I say we can hear difference between magnets! All of them can be made to sound good, but we can hear difference!
    Last edited by scott fitlin; 09-22-2004 at 07:45 PM.

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