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Thread: 4343 crossover modifications

  1. #361
    Senior Member B&KMan's Avatar
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    Quote Originally Posted by rek50
    "Silver Solder Connections"... It must be my "Granite (Hard) brain that doesn't allow me to understand how a SOUND mechanical joint can/would be influenced by the top gas/air barrier (solder). To me, the "Sound Mechanical Joint" IS the connection (the cake), the solder is the "Frosting" on the cake. A helical twisted connection (with wire nuts...ala Henry Kloss) beats a poor weld/solder job, because the solder is the connection, rather than the "Sound Mechanical Joint". I've read about cascading caps and it is interesting but all those caps, instead of one or two for the needed value, might just cause its own problems; a lack of cohesion and focus.... Is it Live, or is it Memorex? At any rate, Nice Work guys! Any Unchallenged man remains a King of nothing. Trying/Working reveals who we really are....
    Thanks rek50,

    But I tested conductivity of connection without soldering and the caps is completely fixed on board... Helicoidal twised connection or just put lead in hole of pcb and soldered, my feeling is the lead on pcb is more fixed by soldering no ??? my reserve is for the quantity of metal create a resistance but not bad electrical connection... but I'm not electronic man...

    the cascade maybe broken cohesion or focus but it is possible to keep 10 Db plus 4 db (full max L-Pad) difference !!! hey is not a details here : it is major problem...


    =================

    but a fundamental question here:

    16 smalls soldering it is better than 3 big soldering ???

    =============

    any specialise have a response ???
    Jean.

  2. #362
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    Jean, I'm not an electrical master either. I do see the logic of a single, big (uF) cap being slower than the same value divided by two caps. To that end, I haven't "Cascaded" so to speak, but rather chose values that compliment all the values in the network. Say if I only needed 22 uF for the LF, 8 uF for MF, 3.3 uF for HF, and 2.2 uF for UHF. For the 22 I used (2) 10 and (2) 1, for 8, (1) 5 and (1) 3, for 3.3 (1) 3 and (1) .33., for 2.2 (1) 2 and (1) .22. My attempt is to keep the response close to equal, considering the duty of each section. I'll measure each cap and write down the measurement. Then I assemble (Sound Mechanical) the caps and measure the total. If the measurement equals the sum of my writen measurements, I'm ready to solder. After I solder, I measure again. The twisted together wire idea was to point out the need for a sound mechanical joint, as I don't view solder as a "Glue".

  3. #363
    Administrator Robh3606's Avatar
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    If you are getting that magnitude of difference something is obviously wrong. Are you sure nothings misswired and the values are correct?? Are the pots on the right legs?? Double check the phase on the drivers?? I am assuming the white plot is the new?? Why the roll off from 2K?? You should be flat out to about 8K from the 2420/2307?? Are you picking up the HF from behind the 2121 low pass filter???

    Rob

  4. #364
    Senior Member B&KMan's Avatar
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    Quote Originally Posted by Robh3606
    If you are getting that magnitude of difference something is obviously wrong. Are you sure nothings misswired and the values are correct?? Are the pots on the right legs?? Double check the phase on the drivers?? I am assuming the white plot is the new?? Why the roll off from 2K?? You should be flat out to about 8K from the 2420/2307?? Are you picking up the HF from behind the 2121 low pass filter???

    Rob
    the thin (very white) is new result and grey is old result ...

    yiah the HF is drop fast and the uhf is poor power... but I verified at close mic close to 2 inch impulse set-up (see : http://www.audioheritage.org/vbullet...&postcount=343 ) the result of each driver appear ok but I dont have a classical response of 3145 of 4345 driver for verifiyng correct correspondance...

    Thanks I run soon test of phase, maybe this is surprise is here...)

    Jean.

  5. #365
    Senior Member B&KMan's Avatar
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    Quote Originally Posted by rek50
    Jean, I'm not an electrical master either. I do see the logic of a single, big (uF) cap being slower than the same value divided by two caps. To that end, I haven't "Cascaded" so to speak, but rather chose values that compliment all the values in the network. Say if I only needed 22 uF for the LF, 8 uF for MF, 3.3 uF for HF, and 2.2 uF for UHF. For the 22 I used (2) 10 and (2) 1, for 8, (1) 5 and (1) 3, for 3.3 (1) 3 and (1) .33., for 2.2 (1) 2 and (1) .22. My attempt is to keep the response close to equal, considering the duty of each section. I'll measure each cap and write down the measurement. Then I assemble (Sound Mechanical) the caps and measure the total. If the measurement equals the sum of my writen measurements, I'm ready to solder. After I solder, I measure again. The twisted together wire idea was to point out the need for a sound mechanical joint, as I don't view solder as a "Glue".

    Thanks for details...

    Do you have picts ???

  6. #366
    Administrator Mr. Widget's Avatar
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    Quote Originally Posted by B&KMan
    Thanks I run soon test of phase, maybe this is surprise is here...)
    Reversed polarity won't do that. Something else is very wrong. Reversing polarity (phase) will primarily give you a notch at the crossover region.

    Widget

  7. #367
    Senior Member Ian Mackenzie's Avatar
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    Quote Originally Posted by B&KMan
    the thin (very white) is new result and grey is old result ...

    yiah the HF is drop fast and the uhf is poor power... but I verified at close mic close to 2 inch impulse set-up (see : http://www.audioheritage.org/vbullet...&postcount=343 ) the result of each driver appear ok but I dont have a classical response of 3145 of 4345 driver for verifiyng correct correspondance...

    Thanks I run soon test of phase, maybe this is surprise is here...)

    Jean.
    Jean,

    Check your wiring layout against the schematic then refer to the 3145 attenuation tables and use the JBL standard test jig to confirm attentuation at the crossover points.

    On the topic of Solder, (Yanks pronounce it Sodda) I used silver Solder from Welbourne Labs and Teflon wiring also from WelbourneLabs.

    As a sub set of the technical excellence = subjective perfection one of my aims was to ensure an almost pure copper signal path to ensure maximum conductivity. Poor quality or corroded teminations are the worst demons of loudspeakers, not solder as such.

    In attempting to acheive this goal the wiring is either Teflon 14 or 12 gauge high purity copper, bindings post premium Cardas, heavy duty 8 pole Speakon Neutrik output socket, terminals are 1 mm pure copper sheet. Provision will also be made for Mills fixed resisters once correct Pad levels are determined.

    As a matter of polarity convention I used Black for negative and Red for postive.
    There is much talk about solder but nothing beats best practise, make sure everything is clean, heat the joint correctly and apply solder to the joint.

    The Doctor
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  8. #368
    Senior Member B&KMan's Avatar
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    OK I'm back again...

    But not with good news...

    I re-read entire thread (it is a real photo-soap )

    I try to found what is erratum to affect cut frecquency...

    first I realise I dont have a electrical response of classical 3145 for 4 driver...

    Anybody have this magical electrical slope cut frecquency ????


    2---


    I back again on a 2 schema presented before in thread...
    (see pict)

    I verified the value of airinductor coil and I realize the value look maybe inversed in one schema

    (if you look serial value of one, it is appear in other schema in parrallele)

    It is a mistake Or really equivalent ???

    Giskard, Robh3606, Ian, other great members ???



    Jean.
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  9. #369
    Senior Member Ian Mackenzie's Avatar
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    Jean,

    The voltage drives are posted earlier in the thread.

    You can use either of the schematics, they appear correct.

    The Doctor

  10. #370
    Senior Member B&KMan's Avatar
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    Quote Originally Posted by Ian Mackenzie
    Jean,

    The voltage drives are posted earlier in the thread.

    The Doctor
    Where # post ???

    I found 3143 and comparison of hf and uhf but not complety curve in regards of driver...



    thanks...

  11. #371
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    Quote Originally Posted by B&KMan
    first I realise I dont have a electrical response of classical 3145 for 4 driver...

    Anybody have this magical electrical slope cut frecquency ????
    Here.
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  12. #372
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    Quote Originally Posted by B&KMan
    It is a mistake Or really equivalent ???
    It looked equivalent to me back when I did it. There could be issues though.
    If I remember correctly this stuff was all posted somewhere else on the forum.
    I think the green curves (A & B) were the second version of the equivalent while the orange curves (C & D) were the original version of the equivalent.
    E, F, G, H were stock.
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  13. #373
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    Changing loads to 16 ohms for HF and UHF.

    If I remember correctly the LE85/2420/2421 was considered a "12 ohm" device and the 077/2405 was considered a "10 ohm" device so 16 ohms should be too radical. I think Mr. Widget recently measured a bunch of the ring radiators but I don't recall seeing any impedance curves. Someone should measure their LE85/2420/2421's and post those impedance curves too.

    Second graphic is with UHF set to 10 ohms and HF set to 12 ohms.

    Try tweeking the HF circuit by replacing the 0.27 mH choke with something like a 0.24 mH or 0.22 mH choke and then adjust the L-Pad. If you have a spice package and measurement gear you should be able to get it spot on with a couple of tries. If you want me to help you with the spice portion then provide me with LE85, 2420, or 2421 impedance curves with the HL91 or 2307/2308 (data files, NOT graphs). If you want help with the UHF too then impedance curves of the 077/2405 will also be required, although the slop in that L-pad is probably sufficient to make any tweeking there fairly pointless. I would have thought the slop in the 8-ohm L-pad in front of the HF would have been enough. Impedance curves of the CD, horn, 20 ohm shunt resistor across the terminals and the L-pad set at 100% on, 75% on and 50% on would be nice too. I don't have alot of this ancient gear around anymore or I'd do it myself.

    What diaphragms are you using again?
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  14. #374
    Senior Member Ian Mackenzie's Avatar
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    Giskard,

    Due to time constraints I have not yet verified the attenuation on the new equivalent network but I can confirm the original equivalent circuit functions correctly under test with the JBL test jig. A graph I posted earlier confirms this with an in room response run. (my driver is an 8 ohm version however but you suggest there is enough slop in the Pads to deal with this).

    Ian

  15. #375
    Senior Member Ian Mackenzie's Avatar
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    Giskard,

    I am incline to think Jean has a wiring or parts error looking at his analyser read out.

    But the 5.6 uf capacitor in (A) appears large relative to the original eqivalent schematic and stock design.(3uf)

    Jean,

    Have you tested for induced currents into the slab of material under your inductors?


    Ian

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