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Cheap and (Pretty) Easy JBL 4430 Upgrade

Thank Zonker,
I have recently put them on small plastic stools (0.18m), and I've heard no difference... My ears wrong, isn't it?
But the speakers look more mighty on stands, so I should buy stands :)

Zonker92 said:
DF, I would think that the higher you raise the speakers, the less bass you will get, since their proximity to the floor gives them some "boundary effect" bass reinforcement from the floor. Or so I hear. I might suggest putting them on milk crates or sturdy boxes to find out what happens.
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Heck, half the mods I do, I can't hear. It would probably show up on test gear, though.

I like stands mainly because they raise up the sound-stage and look cool. :D
 
Jbl 4435 Zonker Mod

First time posting. This thread on modifying the 4430 crossovers has been great. Thank you Zonker!!! I have recently aquired a nice pair of jbl 4435's and in the process of performing Zonker's crossover mod. I have removed the switch and it looks like the jumpers need to be installed in the same places for both the 4430 and 4435. I was confused at first when I looked at Zonkers photo of his jumpers. He apparently selected jumper location based on the circuit board layout and I was selecting jumper location based on reproducing what the switch was doing and came up with different jumper locations. Although we came up with different jumper locations, they are electrically identical. To further clarify for anyone that wants to do this mod. Once you remove the switch, you will see s1, s2, s3, etc on the circuit board. Each is associated with a black line next to it on the board. Each line has three connection points. Example for s1, The center point in the line is the s1 point. The other two points on the line are what s1 can be connected to by the switch. This is the same for s1,s2, s3, etc. It is not possible for the switch to connect s1 to s2 or s6 to s2. That's what made me think Zonker had made a change to the circuit path with his jumpers to make this mod work. I verified the circuit path is the same on the board for both of our jumper locations. I have not installed the jumpers yet. Need to buy some wire and start ordering resistors, caps and inductors. Any recommendations that will work well with these speakers?
 
Welcome to the forum, Scott! I just did the mod to some 4435s and yes; the jumpers are the same. I'm gathering that your approach was to replicate the switch positions, while I was basically ignoring the switch and just trying to link up the requisite PCB traces. Either way, I'm delighted finally to have someone else confirm that my approach works.

I wound up replacing all the resistors with Mills 12-watters from Parts Connexion. Using four 62-ohm resistors in the R6 - R9 positions preserved and enhanced the power-handling capacity of the LF circuit. I replaced the L2 1.0 mH inductor with a Jantzen air core from Parts Express; 16 gauge I think was the right DCR. I left the smallest (L1) inductor in place as it's already a nice air core. I also left intact the bigger coils on the woofers (L101 and L102) on the assumption that they do a decent job by all accounts, although I'd probably use Erse Super Qs if I replaced them, and try to match the DCR.

I also charge-coupled the crossovers; see:

http://www.audiokarma.org/forums/showthread.php?t=636991
 
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Cool; I just edited that thread and revised my reply on this one. I may paste my last reply over there.
 
You have given me a lot to think about. I think I will start by replacing the resistors with mills 12 watt and the jantzen air core foil coil for L2. Sounds like I need to match the resistance or DCR of the original L2 inductor. Can you tell me what the DCR is on the original L2?
 
Zonker,

I forgot to ask you what you think of the Audiocap Thetas in your 4430's? Were they noticeably different sounding, better or worse? If you had to do it again would you try another cap?

Scott
 
Honestly, I haven't a clue. I have never been able to do a recap and say with any degree of confidence how a given cap "sounds." For example, my 4430 project involved bypassing the biamp switch, replacing the caps and replacing one coil. The resulting found was excellent, but to attribute that result to a particular type of cap seems a bit ... speculative, I think.
 
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Heh; thanks. Sometimes I wonder if something's wrong with me, that I can't be certain how a given bit or piece "sounds." :dunno: But I can say that I picked the Thetas for my 4430s because: (1) the values were balls-on identical; (2) the prices were in that Gildilocks zone of being "not too cheap" and not too expensive; and (3) Zilch liked them for bypass caps. (I tend to favor things that he recommended.)

I used them only as bypass caps on the 4435s; using them as the primary caps in the charge-coupled recipe would have cost a mint.
 
What kind of changes would be necessary to actively biamp (with external JBL crossover) after this mod has been done?

Thanks
 
Thanks, Ed; er, Warren! :D Very long day yesterday, just got home late last night.

So the mod I've described normally locks in the internal crossover and locks out the JBL dedicated external crossover as a result. You would have to re-configure it to lock in the biamp / "external crossover" configuration that JBL originally used as the other switch position.

As to how the jumpers would physically be moved around, I'd have to open one up and follow the traces with my eyeballs; that's how I did mine before. Schematic-wise, my goal would be to perform the following steps, after removing the rotary switch:
  • Move the top right jumper (red circle) so it selects the upper switch position (or just take the lead that comes off L102 and plug it directly into the LF(+) input);
  • Move the lower right jumper (red circle) so it selects the upper switch position; and
  • Omit jumpers on all three left switch positions.
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I think that would do it; the LF and HF circuits would continue to be separate and on the LF the L102 coil and C3/C4 caps would be left out of the circuit. C7/C8 would take the place of L2 and C11/C12 on the HF circuit.

But as to where to actually move the jumpers on the PCB, again, I'd have to eyeball the sucker.
 
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Thanks so much!

I am debating purchasing the JBL crossover for a reasonable price right now to give biamping a try.

Cheers,

Warren
 
Happy to help, Warren; let me know how it goes!

I do recall Zilch saying somewhere that he, or someone he knew, and tried the external XOs and preferred the internals, but I dunno.
 
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