4343 crossover modifications

[B&KMan]

Jean,
Your work on your 4343s has been of some interest to me as I too have a vintage pair of these. Your zest for rebuilding these and efforts in trying to improve these is all a bit over my head. Your interest in re-designing these crossovers in more ambitious then anything I would attempt.
When I rebuilt mine, I tried to restore them to original specs. I had to repair the cabinets, do major clean up on everything, replace the fiberglass, repair the grille frames, find replacement nameplates (thanks Guido), and re-foam or re-cone drivers. I also tried to upgrade the caps in the original crossovers. I installed some quality caps and did some bypassing, especially on the HF and UHF circuits.
Over the past year I've carefully adjusted my active crossover, set levels and adjusted the balance with my power amps and L pads to get what I think is nearing the perfect balance.
I did buy a pair of JBL 2421 diaphragms, but haven't installed them yet because the original ones still sound really great.
I feel that one needs to make small changes, and make them one at a time, in order to know what difference they're actually hearing. Too much too fast only leads to uncertainty.
This fall or winter I plan to open my 4343s up again. Then I'll install the new diaphragms and I might put in a few more high end caps. I consider this part of my slow, fine-tuning process.

I will read about your efforts and percieved results, but I'll take your experiences and advice very cautiously.
Thanks again for your enthusiasm!

Tom

thanks

I understand you process, but I burn step in regards of big expertise on the great members and because support by my first grade instrumental lab... otherwise be shure: one step at time is excellent process for keep the control. each room contribute to 50% result (sic) the rest of system is affect the final result => this is a chain !!! so control all parameters and assume one link is default and not other it is really tuff project....



and dont hesitate if you have futur question.

Jean.

[B&KMan]

I have a few minutes again for hint and tips...

The back panel is put on speaker and I listen the difference before fill sand....

No surprise but surprise I dont mesure the level of effect of diffuse sound is push very higher background realism!! all is more real, wide and deep. arround 200% better. the speaker before is really good integration in room and dissapear... but now is the room entirely arround the speaker is disappear !!!

I'm understand many high end speakers is build with pattern of back dissipation effect

( it is part of secret of k2 9800 ???) ...


:Cheers: again.

[rek50]

Jean, I like your "Experiment". Your exposure to vibration and instruments (B&K MAN) opens many doors, that others may have not entered, or cared to. After all, how many people have the testing equipment that you are fond of. To each his own, is an old saying, as well as, beauty is in the eye of the beholder (Beer-Holder, for some)... Enjoy the magic sounds, there are so many to choose from.

[Ian Mackenzie]

External crossover response curves, bi mode using hi end active crossover.

Here are some graphs taken with my very crude equipment by your standards.

The 1st graph is taken 1.5 metre on axis in the listening room . All controls at o position, no smoothing. The purpose og this curve is to proof overall system flatness. Compared to JBL data, the overall curve is almost identical.

The levels were set as previously descibed using a test tone and a Tandy spl meter. There appears no other way of accurately determining the 0 db position.

The other graphs show the individual response of the mid, horn and slot devices with the external crossover. The last graph is the right hand speaker.The slot devices appear to vary from unit to unit in response characteristics, therefore one should attempt to obtain matched pairs of devices if upgrading a system.

Ian

[Ian Mackenzie]

The original JBL test data of the 4345 system, controls set at zero.

While the above curves represent the performance of the 4345 18 inch system , those with 4344's or considering upgrading a 4343 to a 4344 should obtain similar if not identifcal performance. I do think however the offset drivers on the baffle in the 4344/45 accounts for an improvement in the system smoothness over the 4343, apart from the more advance mid and HF drivers. Perhap the imaging is also improved..no flys on the 4345 in that regard..well only one way to finds out.

Perhaps that is the ultimate upgrade for a 4343 owner, make a new replaceable baffle. The drawings are around somewhere deep in the forum.

I remember doing the measurements and the drawings...quite painful actually when you have a hangover like the one I have at the moment..time for quite one at the Pint on Punt.....LOL

Ian

[4343mod]

*snip*...Perhaps that is the ultimate upgrade for a 4343 owner, make a new replaceable baffle. The drawings are around somewhere deep in the forum...
Ian

Agreed, but make the new bolt-on baffle to bring the 8" up to a 12", maybe a D130? with Tatrix Horns! ..Leave the 15" alone, just add another cab and another 15" per side. Anybody here against (2) 15's per side for the extra 3dB?

How about this? Now add (4) 2-ch. amps, (1) DriveRack 480 in 2x4 stereo?

[Ian Mackenzie]

Its actually a 10 inch driver specifically designed for the system.

Other drivers may work but the network may require considerable re design.

Ian

[Ian Mackenzie]

Here are the voltage drives for the respective acoustic graphs above.

Ian

[Ian Mackenzie]

So with the above information and an inductance meter its almost a bomb proof exercise to update/modify the 4343 to a 4344 crossover spec.

You must however invest in updated diaphrams and recones in order that the network will work in a complementry manner to produce the required response.

Otherwise you've got you head in the sand thinking it will be a 4344.

For those content with their vintage 4343 components consider building a charge coupled version of the 3143 network and enjoy the improvements of an updated network.

Ian

[B&KMan]

http://www.audioheritage.org/vbullet...&postcount=308

I again, I read this thread for check, resume and verified if all is OK... before build the second DC charge 3145 sanded network

And I realize I not expose my result in regard of phase .... and maybe I have a question for you great members...

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

the original 3145 expose the 15" inch is non inverted polarity post-current and I put positif (+) electrical amp signal to neg (+) post driver post. and all other driver is invert so all positif signal amp is connected into red (-) post driver of 2121, 2420 & 2405...

Well this is a mistake of my interpretation of schema...

but after check for invert problem of signal of cable and connection into L-Pad
I perform phase match signal and acoustic response

It is appear the 3 upper driver is inverted signal connection. Yup the 2121, 2420 & 2405 is inverted phase response

after test and test and test and verified cable schema...

the final set-up is all black post driver (+) (old convention JBL)
is connected into positif signal amp.

final;

all (+) signal is connected on black post driver (+) of all




But For just shure it is not a weird mistake of me

please Earl and Giskard (specialised of 3145 schema) it is possible to just confirm for other reader this configuration connection is good ...

Otherwise other mistery is on cover ....

[Ian Mackenzie]

The output of the network schematic is drawn correctly.

The positive and negative of each leg of the network goes to red and black speaker connection respectively.

The phase is inverted within the schematics to the mid/hf andf uhf devices.

[B&KMan]

Agreed, but make the new bolt-on baffle to bring the 8" up to a 12", maybe a D130? with Tatrix Horns! ..Leave the 15" alone, just add another cab and another 15" per side. Anybody here against (2) 15's per side for the extra 3dB?

How about this? Now add (4) 2-ch. amps, (1) DriveRack 480 in 2x4 stereo?

it is look of 4355 project no ???

[B&KMan]

The output of the network schematic is drawn correctly.

The positive and negative of each leg of the network goes to red and black speaker connection respectively.

The phase is inverted within the schematics to the mid/hf andf uhf devices.

Well, just for shure if I'm realy understand:

the final result is :

if you send (+) impulse signal electric into a a speaker, normally if network is build correctly, all driver is go foward motion phase. the cone is go outward motion right ??

[Ian Mackenzie]

Well, just for shure if I'm realy understand:

the final result is :

if you send (+) impulse signal electric into a a speaker, normally if network is build correctly, all driver is go foward motion phase. the cone is go outward motion right ??

WRONG.

The woofer should move inward with a positive voltage applied to the RED input terminal of the crossover.

The midrange/horn and uhf should move outward with a positive voltage applied to the RED terminal of the crossover. (this is not easy to confirm without bypassing the filters).

[B&KMan]

WRONG.

The woofer should move inward with a positive voltage applied to the RED input terminal of the crossover.

The midrange/horn and uhf should move outward with a positive voltage applied to the RED terminal of the crossover. (this is not easy to confirm without bypassing the filters).

Thanks for reply but I just try without doubt your response.


1--- in theory, dont matter what code connections or nature of network... the final phase result is all driver have a outward motion right ??


2--- in regard of the theory, I understand your response is according to connection of network : and because the phase of 2121,2420 & 2405 is inverted by circuit network it is important to connect inverted the MF, HF & UHF.


3--- All this old drivers have a (+) post = black right??


4--- Manys folks is expose the JBL monitor is load the LF inverted phase for preload the inside speaker by inward motion. so independently the connection what is final motion of each driver ??? all outward ??? LF inward and all other outward ???


thanks again for light ...


Jean.

p.s. (this is not easy to confirm without bypassing the filters).

You have right... this question is delicate set-up and I study hard for control this parameter with my analyser... but it is easy now to perform this test with filters network load... after response , if you wish , I perform pict of this test.