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Thread: Is it sacrelege? Am I evil? (long) - 4343 xover mods

  1. #31
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    "human audio system is extremely sensitive"

    Actually the human audio system is for shit. It is barely adequate for basic survival and that's about it.

  2. #32
    4343mod
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    Originally posted by Giskard
    "human audio system is extremely sensitive"

    Actually the human audio system is for shit. It is barely adequate for basic survival and that's about it.
    That is right, and why we built shelter and moved indoors, leaving the wild to the beasts. Out there, we were merely food!

    Whoa, this thread has gone anthropo! :lol:

  3. #33
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    We really do strive to morph various threads into shadows of their former selves

    Now, about those lions, tigers, and bears...

  4. #34
    pangea
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    Originally posted by 4343mod

    ...{{hard to see here, but the I values on the HF rotary switch are .1, .15, .23 and .3 uF.}}
    - 4343mod

    Hi, I have two questions, if you'd like to answer them.

    1. You mean mH, not .1, .15, .23, .3 uF?
    2. The 2420 is a 16 Ohm driver, right, and do you know if I can use it with a 2445J?

    BR
    Roland

  5. #35
    4343mod
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    Originally posted by pangea
    - 4343mod

    Hi, I have two questions, if you'd like to answer them.

    1. You mean mH, not .1, .15, .23, .3 uF?
    2. The 2420 is a 16 Ohm driver, right, and do you know if I can use it with a 2445J?

    BR
    Roland
    Pangea- yes, I meant Mill-Henries. Duh-doowie!

    I thought the 2420 was a 16 Ohm driver, but the spare D16R2421 diaphrams I got from JBL measure resistance at around 6 Ohms. Maybe Giskard or someone can figure if 6 Ohms Resistance might = 16 Ohms Impedance? I'd guess the [16] in D16R2421 would mean 16 Ohms, but I dunno.

    As far as 2445J goes, I don't even know what that is. Is that a horn assy? A lens? Giskard?

  6. #36
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    The D16R2420 diaphragm (2420) is a "16 ohm" diaphragm and has a DCR of 5.9 to 7.0 ohms.

    The D8R2421 diaphragm (2421A) is an "8 ohm" diaphragm and has a DCR of 2.9 to 3.5 ohms.

    The D16R2421 diaphragm (2421B) is a "16 ohm" diaphragm and has a DCR of 5.9 to 7.0 ohms.

    The D8R2425 diaphragm (2425H) is an "8 ohm" diaphragm and has a DCR of 2.9 to 3.5 ohms.

    The D16R2425 diaphragm (2425J) is a "16 ohm" diaphragm and has a DCR of 5.9 to 7.0 ohms.

    The D16R2445 diaphragm (2445J) is a "16 ohm" diaphragm and has a DCR of 7.3 to 8.6 ohms.

    The horn loads the compression driver and affects the impedance. Different horns load differently.

  7. #37
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    Wow, so my 2420's aren't 2420 anymore, they are 2421B?
    How does the OEM horn that is fitted to the 2420 respond to a D16R2421 diaphram? Sometimes I really do learn something new everyday...Like today!

  8. #38
    Senior Señor boputnam's Avatar
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    Originally posted by 4343mod
    As far as 2445J goes, I don't even know what that is. Is that a horn assy? A lens? Giskard?
    I'm confused by your question (I should go back and review this Thread, but...) just to be sure you get an answer - the 2445J is a compression driver, with the large diaphram (factory titanium) that some feel is smoother than the smaller diameter siblings. JBL Pro - 2445J CD - Link

    Me? I'm quite fond of the 2421B's, with newly replaced diaphragms (D16R2421B), that I did only a few months back.

    Sweet.

    Oh, and they take the identical horn/lens assembly, the 2391 JBL PRo - Acoustic Lens Family - Link

    (NB: there is a typo in the spec sheet - that is the 2308 Lens...)
    bo

    "Indeed, not!!"

  9. #39
    4343mod
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    Talking

    Well folks, been a long time... and things still work!
    Not one driver burnout on the shallow slopes, and we do party hard sometimes.

    I have been away from the board so long, too busy to breathe for WAY too long but now I have some me time & I aim to make some improvements!

    Yes, it's time to start over again. The Solens & cheesey air cores are starting to sound kinda screetch, and the rotary switch will go, since I rarely go off .15 mH anyway. I'm pushing some shapes around in CAD again, with better chokes and caps, seperate bi-wired 12 dB/octave for the LF, some mild MF/HF value changes, and a simpler, more user friendly pad/shunt bridge for the Mills smear sticks. I'm going to try to reduce contact points and simplify cap/choke switching too.

    This time we'll use Baltic Birch instead of Fir and it's going to probably look like a sloped cigar box, with 2 levels, resistors on top and everything else underneath.

    2121 & 2231A: Can anyone recomend a source for recone besides JBL pro? They want way too much money to rebuild these, I think there are better (more sensitive) parts in the JBL family to replace these with anyway? Si or no?

  10. #40
    4343mod
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    Originally posted by 4343mod
    I will post the OEM schematic that I got from JBL (don't remember what the model number is for the 4343 crossover) and my 1st order schematic when I find them. They have been burried and have been through 2 moves since I made the changes. I know they are around here somewhere!

    Thanks, Andy
    I found that original 3143 XO (4343) schematic & can scan & post it if anyone is still interested.

  11. #41
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    Hi

    You might luck out and find what you need on eBay. For instance here's what turns up today on a search for a 2122H .

    A couple of good looking 2121h mids just sold this week for @ $ 155.00/pr .

    Reconing a 2231 with the 2235 kit is the way to go . You increase the Xmax by trading in the .6" deep coil winding of the 2231 for the .75" deep coil of the 2235. The 2235h kit is a good value - available to authorized recone centers only.

    <. Earl K

  12. #42
    4343mod
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    Earl,
    Thanks for the tip on the 2235 kit. I'd like to get away from foam surrounds if at all possible. Maybe that means different drivers all together. Foam just doesn't seem to hold up to my environment too well.
    Last edited by 4343mod; 10-10-2004 at 11:21 AM.

  13. #43
    Administrator Mr. Widget's Avatar
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    Originally posted by 4343mod
    I'd like to get away from foam surrounds if at all possible. Maybe that means different drivers all together. Foam just doesn't seem to hold up to my environment too well.
    Foam will last 10-15 years period.

    All of the drivers that I can think of including those by other manufacturers that use rubber or a cloth surrounds do not have the LF extension of the 2235 and it's sensitivity. There are plenty of drivers that go lower, there are plenty that are more efficient, but the 2235 represents an excellent blending of these two factors.

    If you are hell bent on getting away from foam surrounds, you can get a cloth surround 2225 kit for your woofers, but you will likely want to add a sub.

    Widget

  14. #44
    4343mod
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    Thanks Widget.
    Actually, I could sacrifice some extension for more sensitivity, then I would need less padding on the 2420, always a good thing in my book. I'm thinking subs are going to become essential anyway to get the levels I want <50 Hz. Is there a kit available that can offer ~100dB voltage sensitivity and the same power rating for these 2231 baskets? I was even thinking about going to 16 Ohm 15's and adding 2 more, and paralleling 2 for an 8 Ohm load and +3dB response, then working on a sub solution.

    Thanks again for all the info guys! The JBL parts list & history is so vast, I'm impressed with your knowledge! All of you!

  15. #45
    4343mod
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    Oh, yes, regarding the life span of foam: I'm sure that is true. But how does one know that the kits one pays to have installed aren't NOS and been sitting on a shelf in a hot warehouse for 10 years? Then your "brand new" kits are already half way dead just from drying out on a shelf. Possible?

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