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Old 22nd December 2003, 11:56 AM   #1
HH is offline HH  Denmark
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Default JBL 4343 modifications

Hi,

I am using a pair of JBL 4343's. Recently I have replaced some of the caps in crossover used for the 2420 driver and the 2405 slot tweeter with Jensen oil in paper caps. The results were very encouraging, and now I would like to make further improvements.

In the crossover there is a 52 uF capacitor that all the signal for the MF, HF and UHF drivers apparently has to pass. Is there any way of getting rid of this capacitor or any other ways of simplifying/improving this crossover?

Any help will be greatly appreciated.

Crossover schematic
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Old 22nd December 2003, 12:47 PM   #2
sreten is offline sreten  United Kingdom
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The 52uf capacacitor and the related 2.8 ? mH inductor seem
to be permanently in circuit for the top three drivers in normal
mode.

In bi-amp mode, that does require an external active crossover,
only the 52uf capacitor is used in series with the three drivers.

My guess is that it has been done like this to reduce the
voltage rating required of the first HF and UHF capacitors.
(Or to simply reduce the stress on the first capacitors)

Some rewiring of the switching would allow you to bi-wire the
speakers, and run them is passive bi-amping mode as well.

I believe there is a dedicated JBL studio monitor forum somewhere.

sreten.
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Old 22nd December 2003, 01:38 PM   #3
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Quote:
Originally posted by sreten
I believe there is a dedicated JBL studio monitor forum somewhere.

sreten.
HH,

The Lansing Heritage forum is here:
http://audioheritage.org/vbulletin/s...?threadid=1203
This link will take you a discussion on the 4343 among other things.

The 4343/4345's are fantastic speakers. I just setup a pair for a friend of mine. They can sound really good with a little elbow grease.
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Old 22nd December 2003, 02:26 PM   #4
HH is offline HH  Denmark
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Thanks,

I have now posted my question at the Lansing Heritage Forum too..

But any help from this forum will still be greatly appreciated.

HH
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Old 22nd December 2003, 02:57 PM   #5
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HH,

One simple improvement is to biamp the system or alternatively bypass the 52 uf with a smaller value film foil capacitor.

Ian
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Old 22nd December 2003, 03:44 PM   #6
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Tweaking the mid-horn is necessary in this system. I explain the tweaks I've used here:
http://audioheritage.org/vbulletin/s...5&pagenumber=6
I've had good success with these mods and they go a long way toward taming some of the peaks.
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Old 25th June 2011, 09:01 PM   #7
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"Am a newbie to this forum. My 4343s have been with me since new - 1978 or so. Just had the 10 inchers rebuilt and the shop suggested I re-do the crossovers, too. Since I want to, at long last, bi-amp the system, I need some product info for electronic x-overs and 75 watt power amps.

carl
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Old 25th June 2011, 09:03 PM   #8
kevinkr is offline kevinkr  United States
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Quote:
Originally Posted by carlsderr View Post
"Am a newbie to this forum. My 4343s have been with me since new - 1978 or so. Just had the 10 inchers rebuilt and the shop suggested I re-do the crossovers, too. Since I want to, at long last, bi-amp the system, I need some product info for electronic x-overs and 75 watt power amps.

carl
Your best place for this sort of information is going to be the Lansing Heritage site. They have a forum and a lot of knowledgeable folk on all things Altec, and JBL..
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