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Thread: Quick & Dirty 4430-Inspired Two-Ways Part II

  1. #316
    Senior Member B&KMan's Avatar
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    Quote Originally Posted by Zilch
    Not yet, Jean. I'll do it last.

    Gotta unhook stuff and measure for that.

    Today, I'm just listening without it.

    I'm tweaked out for now....

    no rush...
    I discovered with to the invaluable assistance of other members and recent reading, that normally the zobel must be where placed it to you... on the other hand the fact of putting it at the beginning is not innocent either since it affects it inter reaction of all network. voilà where my question and my curiosity on the answer...

    I am in a hurry well to read you on this last adjustment...




  2. #317
    RIP 2011 Zilch's Avatar
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    Quote Originally Posted by Zilch
    Driver/diaphragm swaps are not so trivial as many (like myself) might suppose....
    Here's the logic:

    1) LE85 = 2420
    2) 2420 w/D8R2421 = 2421
    3) LE85 w/D8R2421 = 2421
    4) 2421 = 2425H in 4430 (They didn't change the crossover, allegedly.)
    5) 2426H = 2425H
    6) LE85 w/D8R2421 = 2426H?

    Not on H3100 with N3100.

    Unless my LE85's are FUBAR, maybe.

    [Gotta do the 1" motor/diaphragm study....]

  3. #318
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    Quote Originally Posted by Zilch
    4) 2421 = 2425H in 4430
    Nope. Different animals.
    Quote Originally Posted by Zilch
    6) LE85 w/D8R2421 = 2426H?
    Only if the 2426H is also running the D8R2421 diaphragm.

  4. #319
    RIP 2011 Zilch's Avatar
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    Thanks, Giskard.

    Having earlier "discovered" (duh!) that the various PT waveguides each required different filter compensation, I was not terribly surprised to find that 275nd diaphragms with their Aquaplas coating (much heavier than "dusting" would imply,) exhibited a different response characteristic.

    I did not, however, anticipate that a mylar surround aluminum diaphragm would be so different, let alone a diamond-surround aluminum diaphragm vs. a diamond-surround titanium.

    Part of this may be the different motors, as well. Quite apparently, I need to get some of these variables under control here. CLIO has arrived, which will afford the opportunity to do that with some precision....

  5. #320
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by Zilch
    Part of this may be the different motors, as well. Quite apparently, I need to get some of these variables under control here. CLIO has arrived, which will afford the opportunity to do exactly that....
    As resident Clio advocate, I'll say that it will give higher resolution pictures of the differences, but really your ears will tell you more. There are subtleties that a simple frequency response and harmonic distortion curve just won't show.

    Back when I bought my first pair of 4430's I was specifically told to get the 2421A's because "they sound better"
    When JBL made the switch from the aluminum diaphragmed 2421 to the titanium diaphragmed 2425, they didn't publish new response curves and make a big announcement... the difference was subtle but audible. The decision was to increase the reliability of the product accepting a slight change in sonic quality.


    Widget

  6. #321
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    Exactly,

    The audibly subtle nature of networks and drivers goes well beyond the measurement yard stick.

  7. #322
    Senior Member B&KMan's Avatar
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    Quote Originally Posted by Mr. Widget
    .

    When JBL made the switch from the aluminum diaphragmed 2421 to the titanium diaphragmed 2425, they didn't publish new response curves and make a big announcement... the difference was subtle but audible. The decision was to increase the reliability of the product accepting a slight change in sonic quality.


    Widget
    if I caricature, I understand that: the 2421 is refined more than the 2425 but at long time or with high voltage, the 2421 is less reliable??

  8. #323
    RIP 2011 Zilch's Avatar
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    http://audioheritage.org/vbulletin/s...ead.php?t=3233

    From what I understand, the aluminum diaphragms are smoother sounding because of the inherent damping of the softer material.

    They seem to last long enough (40+ years) in moderate home use.

    LE85/2420 is tangential aluminum
    2421 is diamond aluminum
    2425/6/7 is diamond titanium

    Here's a 1965 tangential aluminum that finally gave up. I do not know its history of use or abuse, but you can see the lines of flexural fatigue and ultimate failure around the edge of the dome:
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  9. #324
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by B&KMan
    if I caricature, I understand that: the 2421 is refined more than the 2425 but at long time or with high voltage, the 2421 is less reliable??
    Yes.

    The operative terms are long time and high power... I believe both the titanium and aluminum drivers will last virtually indefinitely when lightly used... under hard use the titanium or aluminum with a mylar surround are significantly more robust.

    As seen in Zilch's photo, the aluminum surround stresses and fails. I personally don't believe in a typical home environment, even playing occasionally at very high levels, the aluminum surrounds are a problem. If you run your home system at 120dB for extended periods... it may occasionally be a problem. I know I drove my LE85s that hard for several years with no problems years ago when I was young and stupid...


    Widget

  10. #325
    Senior Member frank23's Avatar
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    I am not an expert on this, but in the cycling world, fatique has been a major issue in bike frame design. Bikes used to be steel, but are mostly aluminium now, and more and more titanium bikeframes become available. Titanium is very hard to work at though.

    As I understand both steel and titanium have the characteristic that if you stay under a certain stress level, material fatigue never shows. So if you don't play too loud, titanium diaphragms should last several lifetimes.

    In aluminium, the material hardens a little under stress and that necessarily results in fatigue induced failure [like the picture above]. As I understood, you cannot escape it, in the end, they will all fail.

    Would anyone know if the diamond surround stresses the diaphragm more than the tangential surround and that would have been the reason to go to titanium? I wonder because JBL first introduced the diamond surround and then titanium only a few years later.

    edit: "Fatigue Strength: the level at which a material can withstand an infinite number of stress cycles."

    As I understand, the fatigue level for aluminium is zero, so it will break eventually at whatever level you choose. Steel and titanium have a level under which you can stress them an infinite number of times.

    edit again: the link in zilch's posting above answers some of my above observations...
    frank

  11. #326
    Senior Member B&KMan's Avatar
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    age vs distortion

    Quote Originally Posted by Mr. Widget
    Yes.

    If you run your home system at 120dB for extended periods... it may occasionally be a problem.

    Widget

    the time exposure for permanent earing loss at level of 120 dB is

    10 to 15 seconds


    =============
    ok, I refine my question...

    the stress and fatigue material it is probably here after 40 years but the diaghram is look good. so, more years passed, more level distortion increase ??? and logicly; less power handling possible...

    after read the link of Zilch for fatigue material on compression driver, I look my diaghram, it smell new... but it is realiable ???

    what is the harmonic chart of JBL for for tolerance of harmonics ???
    or what is global TDH ???
    the real level harmonics 2,3,4,5,6,7,8,9,10,11,12,13,14,15,???
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  12. #327
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    Dubbed "Annular Ring Diaphragm™ compression drivers," JBL 2406H (top) and 2407H on PT-H1010 waveguide with JBL 1" throat adapter, no filter. They appear to be ferrite and neodymium versions of the same polyester-diaphragm driver, though I haven't opened them up to verify:
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  13. #328
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    Different approach: Tweeters that play low:

    Initial evaluations were less than satisfactory. Though clear sounding, they were fatiguing to listen to. After Toddalin heard them and we agreed on the analysis, it became apparent that these VHF drivers do happen to play low, BUT, they need 24 dB/octave crossovers to prevent them from playing TOO low.

    I constructed crossovers after AM4212/00 (1.3 kHz) and here's the results with LE14H-3 LF. These all have the HF padded down ~9.5 dB:

    1) PT-H1010 w/throat adapter
    2) PT-H95 w/throat adapter
    3) PT-F95 (1", shown with crossover in bottom pic)
    4) 2342 Butt Cheeks biradial.

    Crossovers will require adjustment for waveguide type used. I've resorted to AutoEQ to try them all, and they sound quite good now.

    Biamping with an active 24 dB crossover (M552) and parametric EQ might be a better approach. 24 dB passives are, ummmm, a "challenge."
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  14. #329
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    Hi,

    Sorry I had to ask this question here, since it is a 4430 thread.

    I had the opportunity to see a pair of 4430, and I tried to push the 2235 to check the condition of the foam surround (again it was refoam wrongly, on the outside ).

    To my surprise, it feels very light, almost like there's no resistance, compared with my experience with the 2231 on my 4333A.

    Is this the correct behaviour of the 2235?

    Thanks.

  15. #330
    Senior Member B&KMan's Avatar
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    cone free displacement 2235

    Quote Originally Posted by ngccglp
    Hi,

    Sorry I had to ask this question here, since it is a 4430 thread.

    I had the opportunity to see a pair of 4430, and I tried to push the 2235 to check the condition of the foam surround (again it was refoam wrongly, on the outside ).

    To my surprise, it feels very light, almost like there's no resistance, compared with my experience with the 2231 on my 4333A.

    Is this the correct behaviour of the 2235?

    Thanks.

    my small experience...

    I haved a non original cone and I pull out for a original cone 2235 in my 2231 and I have surprise more stiff product... and mass ring include.... but it is really difficult to put good jugement via internet...

    now 4 years later my 2235, in vertical position have a few little resistance in 1/4 inch ( 5 mm) and is more stiffe for the rest of space displacement.

    I hope this is help you.



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