JBL 4350 Question

[Audionutz]

Hello to all and thanks for the great forum !

I had a thought the other day on a basic mod to my 4350's and wondered if anyone could help?

Presently, I'm driving the mid/highs with a pair of 80wpc OTL's, which do a superb job on the highs.

However, in comparison to the 120 watt EL34 monoblocks I had before, they miss a bit in midrange punch and dynamics.

It occurred to me that if I could passively crossover the 2 x bass 15's, I could then run the upper bass/mid 12 inch driver with them off a single amp, thereby bring back the power into that part of the range.

I don't know if JBL ever made a passive crossover to roll off the top of the two bass 15's, or if they always used active crossovers and bi-amping ?:dont-know:

This would also mean that the system could be run from a single amp later, if desired.

Im not interested in mods that cant be reversed later, as I am adamant I'm going to keep these as original in appearance as possble ...

Cheers

'Nutz

[Woofer]

You would only have to run a passive 2-way x-over before the boxes two speaker inputs on the back of the 4350.
Have the new passive x-over feed it's Hi & Lo output directly into the Hi & Lo ins on the box.
Then you'll be able to run a single (stereo) amplificator.
I know someone in your neck of the woods that can do that for you, but with the quality of parts and the power handling needed, it ain't gonna be cheap. :o:

Sell 'em and get an iPod with earbuds. :p

LoL..... :D

[Audionutz]

You would only have to run a passive 2-way x-over before the boxes two speaker inputs on the back of the 4350.
Have the new passive x-over feed it's Hi & Lo output directly into the Hi & Lo ins on the box.
Then you'll be able to run a single (stereo) amplificator.
I know someone in your neck of the woods that can do that for you, but with the quality of parts and the power handling needed, it ain't gonna be cheap. :o:

Sell 'em and get an iPod with earbuds. :p

LoL..... :D


Nope, not quite what I meant.

I want to run the midrange 12" off the same amp as the bass 15's, so I'll need to roll off the top of the 15's. I'm hoping to be able to split the existing Mid/High crossover to give the 12" what it needs.

So ...I 'll need a crossover for the 15's, plus one for the 12, plus one for the horn/tweeter and hopefully all passive.

Hope thats clearer .... ? :confused:

[Woofer]

Well not being a Passive fan, I'd go with Active Tri-amp-ing. (but that's me.)
With what you're saying, the original internal passive x-over will have to be modified.
A snip here, and a replacement cap or two there, give it a good stir, and that should do it.
Nothing that can't be reversible.
Once again, you should give "you know who" a call..... ;)

[Robh3606]

It occurred to me that if I could passively crossover the 2 x bass 15's,

Both the 4350 and 4355 were set-up as Biamp only. What you need to do in replicate the voltage drivers for the cards used to biamp them in the 5234/5235 crossovers. Then use them as a guide curve in your simulation software. That will give you a target to get an exact passive equvalent. Be aware if you add pasive components on the bottom end of the 12's range the upper half of the crossover will most likely need to be tweeked as well. You will easilly be able to see this in your software when you compare it to the original passive voltage drive that rolls off the top end of the 12/2202 to the new curve with the added componenets to roll off the lower end of the 12' 2202.

Rob:)

[4313B]

Unfortunately I've already gotten rid of all the 4350/4355 gear so I can't whip up a pair of full passive networks. Not real sure that I would want to anyway as these things sound so much better bi-amped. I'm still perplexed that I have to build all these bi-ampable 4345 networks. :rotfl: I wanted to just stick with bi-amp only versions. :D

[MikeM]

Too Bad I unloaded the NOS 4350 xovers jbl had for 70$ each years ago, be good experiment material. If you look at the schematics on the xovers they are pretty straight forward.. I had a Pair of 4350 wh3n you could get a a pair for 3 grand... Nice speakers!

[Audionutz]

I still want to keep them bi-amped.

No intentions of changing that at this point.

Really, what I'm looking for is the extra "slam" in the upper bass/lower mids whilst retaining the benefits of the OTL sound.

I've been experimenting this morning with raising the bass crossover point to 290 from 250. Its slightly improved, but still not what I'm after.

Lastly, I was under the impression the standard crossover model was JBL 3150, but I see JBL 3107 mentioned as having been fitted to some 4350's ? Correct or not and where can I find the schematics ??

Thanks for the all the suggestions too - keep 'em coming :applaud:

[Woofer]

Wot happens when you reverse the phase/polarity of you bottom end?
Try that, then fiddle with your x-over points.....

[Audionutz]

Wot happens when you reverse the phase/polarity of you bottom end?
Try that, then fiddle with your x-over points.....

Did that at first. Its quieter in the bottom end, but a lot "leaner". Being quieter suggest I had it correct the other way, as I recall ?

Still experimenting with the x-over ......;)

[Woofer]

Have you got any software that will do a (Pink) Noise Generator and Spectrum Analysis?

[Audionutz]

Have you got any software that will do a (Pink) Noise Generator and Spectrum Analysis?


Nope, but I know someone who has .....:D

[MikeM]

I still want to keep them bi-amped.

No intentions of changing that at this point.

Really, what I'm looking for is the extra "slam" in the upper bass/lower mids whilst retaining the benefits of the OTL sound.

I've been experimenting this morning with raising the bass crossover point to 290 from 250. Its slightly improved, but still not what I'm after.

Lastly, I was under the impression the standard crossover model was JBL 3150, but I see JBL 3107 mentioned as having been fitted to some 4350's ? Correct or not and where can I find the schematics ??

Thanks for the all the suggestions too - keep 'em coming :applaud:

I have the 3107 schematics here. I cannot scan them. Let me know if you want a copy

[MikeM]

[QUOTE=Audionutz;289734]I still want to keep them bi-amped.

>I've been experimenting this morning with raising the bass crossover point to 290 from 250. Its slightly improved, but still not what I'm after.<

If anything Myself I went lower then 250hz. Critical range with dual 15's.
Good luck-enjoy the music.

[Woofer]

Yeh..... I don't like 250 Hz either, and usually prefer going a tad lower.

[Audionutz]

[QUOTE=Audionutz;289734]I still want to keep them bi-amped.

>I've been experimenting this morning with raising the bass crossover point to 290 from 250. Its slightly improved, but still not what I'm after.<

If anything Myself I went lower then 250hz. Critical range with dual 15's.
Good luck-enjoy the music.


Hadnt thought of that actually - duh:blink:

Will give it a try and report ........

[Robh3606]

Here is the crossover link

http://www.jblproservice.com/pdf/Network%20Schematics/3107%20Network.pdf


Rob:)

[Audionutz]

Here is the crossover link

http://www.jblproservice.com/pdf/Network%20Schematics/3107%20Network.pdf


Rob:)

Thanks muchly - :applaud:

Scott

[Audionutz]

So.... can anyone tell me whats needed in a passive x-over to roll off the 15's at 250, or thereabouts ??

I have the other side of it semi-sorted out now, but still researching the above !

Cheers

Scott