JBL 4343 Renovation

[georgebrooke]

Hi,
Years ago I promised a description of a 4343 renovation. It has taken me nearly 5 years to get anywhere with this... due to work pressure and the number of steps in my house. Neighbours who volunteered to help move the speakers from the garage to the house have aged but luckily some passing builders were talked into getting the speakers into the house.. but only after Rich (of Richluvsound) had performed some minor miracles.

The speakers were purchased (via eBay) from an ex-roadie of Pink Floyd. The initial problems were poor cabinet finish (in spite of the claim of a "piano finish") and rotted surrounds. Apart from putting them on wheels (since removed). They sat in the garage while I pondered active crossover, passive crossover, charge-coupled. Meanwhile I went ahead with building the electronics (Pass B5 buffer, F5 power amp, Crown K2 (purchase) bass amp).
Eventually I decided that I needed to get them into the house and that would not happen with them in their poor condition.

Having met Rich a few times I asked him if he would help on the woodwork. In this case, "help" turned into doing it all. He did an outstanding job as the attached before and after photos show. He has made his own thread on the work he did at http://www.audioheritage.org/vbulletin/showthread.php?33213-Latest-project-! One of my attached photos shows a close-up or the veneering and mitred corners. He has done a really superb job.

The situation now is that they are more than acceptable in a living room. Moreover, they sound ... even in their present un-tuned state so much better than my old L300s that I am sure that I am on the right track with these.

So, things to do.
Refoam the bass speakers. They had nestled in the house, not the garage, but that had not saved them from the ageing process. I have ordered kits from Rick Cobb. I have used his products in the past with good results.. and his method avoids the use of shims and dust cap removal.
Set up the balance of the speakers.. on 4-way systems not as easy as it should be
Listen to the speakers... on all kinds of music and take notes
Decide on upgrade priorities. From related threads I am awash with suggestions and ideas. My current thinking is to wait for a DIY version of the B4 crossover from our friend Nelson Pass and combine that with a rebuild of the remaining parts of the crossover. Given the similarity, it may even be possible to adapt the L300 crossover, recently redesigned by Nelson, for use in the 4343.
Preserve the original form and components of the 4343
If any one has comments or thoughts on what I am planning to do I am more than keen to hear them

I find it very satisfying to bring back top quality equipment to as near to its original state as possible. With this sort of equipment I am not so much the owner as the keeper, for now. Remember the Patek Philippe advert. "You never actually own a Patek Philippe. You merely look after it for the next generation". Well, if the next generation have big enough living rooms this might just be true!

[Lee in Montreal]

Nice restoration work.

[57BELAIRE]

Outstanding! :applaud:

I am currently involved in a similar project with a pair of 4350's and after some discussion and following numerous threads on this forum and other's, I've decided to keep them as original as possible with the exception of charged coupled networks.

They had been stashed in a warehouse for some years and before that were in a basement party room. I hope to bring them back to their former glory...well, almost. The walnut veneer is passable for now and the original drivers (except 2202H mid-bass) are surely roadworn but still pack quite a whallop.

After seeing yours, I'm fired up again to complete this project even more than ever

Your efforts are truly inspiring!

[georgebrooke]

Outstanding! :applaud:

I am currently involved in a similar project with a pair of 4350's and after some discussion and following numerous threads on this forum and other's, I've decided to keep them as original as possible with the exception of charged coupled networks.

They had been stashed in a warehouse for some years and before that were in a basement party room. I hope to bring them back to their former glory...well, almost. The walnut veneer is passable for now and the original drivers (except 2202H mid-bass) are surely roadworn but still pack quite a whallop.

After seeing yours, I'm fired up again to complete this project even more than ever

Your efforts are truly inspiring!

Hi,

it seems that your speakers had a troubled start just like mine... starting out in a garage. I really would encourage you to finish them.. but always be able to get them back to the original state regardless of changes that you might make.
In doing all this work my speakers are back to the original JBL "slam" but sadly they have lost the characteristic JBL smell. It used to be that I could recognise JBL speakers at 20 paces. No longer with mine. I think Rich cleaned them out properly!

[hjames]

They do look gorgeous now - Rich did outstanding work ...

and if you want the old "JBL smell" back, I imagine you could always spill a few pints on or around it and
get that back too, tho it'd be a real shame to muss that fine wood finish!


Hi,

it seems that your speakers had a troubled start just like mine... starting out in a garage. I really would encourage you to finish them.. but always be able to get them back to the original state regardless of changes that you might make.
In doing all this work my speakers are back to the original JBL "slam" but sadly they have lost the characteristic JBL smell. It used to be that I could recognise JBL speakers at 20 paces. No longer with mine. I think Rich cleaned them out properly!

[georgebrooke]

Hi,

can anyone point me to a clear procedure for setting up the L pads on the 4343s? I have a sound meter and access to a signal generator, but I am not sure of the frequencies to choose nor of the levels to aim at. In other words, not a clue! :(

Today the new foam surrounds for the bass units arrived. And just in time too... as a bass-heavy track left pieces of foam scattered over the carpet. I am expecting the bass to get even tighter with the repair fo the surrounds, but even now it is considerably tighter than my memory of the L300s. :)

[jbl_daddy]

I have toyed with the idea that you just completed, my wife says she still will not let them in the family room. Lucky she likes the 250ti's... In her defense she puts up with more than i could.

[BMWCCA]

Hi,
can anyone point me to a clear procedure for setting up the L pads on the 4343s? I have a sound meter and access to a signal generator, but I am not sure of the frequencies to choose nor of the levels to aim at. In other words, not a clue! :(

One method: Run a full frequency range, record SPL at each frequency and aim for a flat response (same level) on every frequency you run, with the meter in the spot your ears would be. (You'll probably need at least a third-octave EQ to do it accurately depending on your room).

Another: Adjust the L-pads in small increments and listen. Set it the way you like it. Treat them like tone controls to some extent. They're your ears and it's your system.

One more: Assume that god knew what he was doing; do away with all tone controls and keep the L-pads at zero. Any audiophile will agree. ;)



I used a Rat Shack dB meter and a compact pro tone generator with a full-spectrum sweep. I put the meter on a tripod and actually found my room reasonably flat without any adjustment. It was more reassuring than it was illuminating, but my room is well-damped, pretty small, with low ceilings and equal openings at either end/side, with enough "stuff" and furniture to kill just about any resonance. I do have a third-octave EQ in every system but generally use it for low-level listening compensation only.

[Earl K]

<snip>,can anyone point me to a clear procedure for setting up the L pads on the 4343s? I have a sound meter and access to a signal generator, but I am not sure of the frequencies to choose nor of the levels to aim at. In other words, not a clue!

Ian MacKenzie posted a "KISS" procedure ( quite a few years back ) that used an SLM/SPL meter ( along with certain test tones ) to balance the Lpads of these big 4-ways . It was apparently quite effective .


:)

[georgebrooke]

Ian MacKenzie posted a "KISS" procedure ( quite a few years back ) that used an SLM/SPL meter ( along with certain test tones ) to balance the Lpads of these big 4-ways . It was apparently quite effective .


:)




Hi,
I did see Ian's post.. but I could not understand why he chose the frequencies that he did and some of the instructions were a bit (IMHO) ambiguous.
Anyway, the plan is still to listen for a while.. fix the foam surround (which arrived from the US in just a few days after ordering) and let the system settle. Then start a procedure for balancing. Ultimately I suspect it will be a procedure followed by fine tuning according to ear-preferences. We shall see. This is just the start of a long job.

Strangely this morning I noticed the JBL smell reappearing. Perhaps the bass notes have shaken it out of the wood but it is definitely there. It could make a nice aftershave :-)
I am still impressed how non-hi Fi it all sounds.. big, relaxed and nimble!
Thansk for all the advice

[georgebrooke]

One method: Run a full frequency range, record SPL at each frequency and aim for a flat response (same level) on every frequency you run, with the meter in the spot your ears would be. (You'll probably need at least a third-octave EQ to do it accurately depending on your room).

Another: Adjust the L-pads in small increments and listen. Set it the way you like it. Treat them like tone controls to some extent. They're your ears and it's your system.

One more: Assume that god knew what he was doing; do away with all tone controls and keep the L-pads at zero. Any audiophile will agree. ;)



I used a Rat Shack dB meter and a compact pro tone generator with a full-spectrum sweep. I put the meter on a tripod and actually found my room reasonably flat without any adjustment. It was more reassuring than it was illuminating, but my room is well-damped, pretty small, with low ceilings and equal openings at either end/side, with enough "stuff" and furniture to kill just about any resonance. I do have a third-octave EQ in every system but generally use it for low-level listening compensation only.

Thanks for the above .. I think they are the start of a procedure that I could use. Re. the involvement of God in this.... you can give him a helping hand by starting from a clear starting point. This may sound stupid, but if you have one of those Water Pic devices then , using warm water, you can give yourself an ear syringe. I promise you that for around 30 seconds (until clever-old brain adapts) you will hear detail in your music like you have never heard before. Don't use cold water.. apparently this is used to test pilots for a tendency to vertigo and it could trigger an attack. Still, even if you are on your back it will still sound pretty amazing.

George

[spkrman57]

Nice work!

Regards, Ron

[georgebrooke]

Hi,
I seem to have answered my own question regarding the set-up. A colleague appears to have a pair of "golden ears" and infinite patience and went through an extended adjustment session with me on a variety of music. We arrived at a setting which we both appreciated. Whether this is "right" probably does not matter.. they sound glorious.

There is another small problem. Eagle-eyed readers might have noticed something odd about the grilles shown in my photographs above. The JBL model number plate is fixed to the top of the grille and extends in front of the tweeter and super-tweeter, doing nothing good to the sound at all. I have so far not been able to find the recommended position for the JBL model-number plate, except to guess that it should be at the bottom of the grille. Can anyone provide me with photographs and / or measurements of the correct position of this plate. I really would like to get it right when I do move it. Most photographs that I have come across avoid showing JBL grilles, in favour of showing off those impressive drivers. Thanks for the help

[1audiohack]

I can send you a picture and measurements in a couple of days of an original near pristine pair owned by a friend but I can tell you in the meantime that the plates are top left and do shadow the 2405 and 2308. Isn't that odd??

[boputnam]

...Can anyone provide me with photographs and / or measurements of the correct position of this plate. I really would like to get it right when I do move it.

Per my pm, my 4345's are top-left, as per Barry's post (1audiohack) for both cabinets, R or L, JBL logo always on L side (like the Union Jack on the US Flag...).
1 1/8" below top of grill
2 1/2" inside left edge of grill
But, these are 4345's, and not the cabinet in question.


I can send you a picture and measurements in a couple of days of an original near pristine pair owned by a friend but I can tell you in the meantime that the plates are top left and do shadow the 2405 and 2308. Isn't that odd??Not the 2308, surely (unless your vanes are angled upwards...? :eek:). On the 4345 there is no obstruction to the 2405; on the 4343, from the pictures here, it looks like only the very top'ish area of the 2405? But remember this is a horizontal-dispersion wave guide. I think we need some pics from un-retouched 4343's to see what the makers intended - maybe that logo plate is shifted upwards....

[georgebrooke]

It seems that photos of 4343s with grilles intact are pretty hard to come by. Worse, it seems that some grilles, like mine, have these plates in front of the tweeters. Unless JBL were doing some very sophisticated sound-engineering I doubt if this was intended. I am still searching for an authoritative photo of JBL originals. If anyone has such a thing I shoudl be very grateful to receive it. I would then try to get the exact positioning and publish the figures.
I would never have believed such a "simple" question would be so complicated

[DogBox]

Hi georgebrooke,
Have you seen the photo's from the library brochures on the 4343? The library has the 4343 and the jblpro.com/vintage has the 4343B-both have pictures on the second page showing the nameplate where Bo said they were placed. Not a real good shot for accurate placement positioning, but let's you know were they were put originally. Hope it helps... :)

Steve

[1audiohack]

Hi George and DogBox;

I am currently visiting a friend who has a one owner, near pristine pair of 4343's as his home mains. I left the camera at the shop last night but I will before I leave this weekend collect the dimensional information and pictures you are asking for, please stand by.

Barry.

[georgebrooke]

Hi,
well as information on the position of these nameplates continues to pour in, it seems there is no real resolution. I have come across photos showing the nameplates positioned at the top as well as at the bottom of the grilles.

Although the top position is persuasive, being shown in a JBL brochure, I cannot believe that it is intended. The plate passes across the centres of the two tweeters. This is unorthodox to say the least. So, unless someone can provide evidence that this is an intended sound modification .. a crude type of lens for example.... I think I have to dismiss top mounting, even if it does look nice.

So, positioning at the bottom is not so difficult. The brackets that JBL provide do have to be moved (they provide brackets for top mounting for vertical use, and side mounting for horizontal use) to the bottom of the grille. They only questions then is to left or right justify , or to provide mirror image. Since none of these choices can affect the sound it is a purely cosmetic decision. The brackets control the height of the nameplate. There is about 18 cms. of movement possible in left-to-right positioning. Feel free to choose, as we seem to be leaving JBL's mounting decision anyway.

I am still open to persuasion on this... if there is compelling evidence to support the top position. Melanie thansk for the many answers and PMs on this subject.

George

[georgebrooke]

Hi georgebrooke,
Have you seen the photo's from the library brochures on the 4343? The library has the 4343 and the jblpro.com/vintage has the 4343B-both have pictures on the second page showing the nameplate where Bo said they were placed. Not a real good shot for accurate placement positioning, but let's you know were they were put originally. Hope it helps... :)

Steve

Hi Steve,

thanks for reminding me about page 2 of the brochure. I still doubt if JBL really intended to stifle the tweeters with a nameplate, so I'm now brooding on the subject, again. The phrase "Get a life" springs to mind :-(

George

[hjames]

Hi Steve,

The phrase "Get a life" springs to mind :-(

George


Not at all - you HAVE a life!
you have a pair of GORGEOUS monitors,
be sure you enjoy the heck out of them -
play some good tunes, or discover something new -
that's the whole point of all this dancing!

:banana:

[4313B]

It takes a helluva lot more than some little strip of aluminum to stiffle a slot. They'll just burn a hole through that thin foilcal.

[1audiohack]

Hi Steve,
I still doubt if JBL really intended to stifle the tweeters with a nameplate, :-(
George

They didn't and they don't. Inside the grill frame behind the cloth are small metal tabs that the badges clip to/through. They can be attached left or right in mirror image as to not shade the tweeter with the box oriented either vertically or horizontally.

I have the dimensions and pictures but posting them will have to wait until I get home Monday.

[georgebrooke]

They didn't and they don't. Inside the grill frame behind the cloth are small metal tabs that the badges clip to/through. They can be attached left or right in mirror image as to not shade the tweeter with the box oriented either vertically or horizontally.

I have the dimensions and pictures but posting them will have to wait until I get home Monday.

Hi,
i am looking forward to seeing your definitive photograph of the proper positioning of the plates. However, by the time they arrive, Monday, I shall be on a boat just off Portugal and heading to Spain, France, Sicily, Italy and Croatia in that order. Hence JBLs will not be top of my list for the next three weeks. But when we get back......;)

[DogBox]

.... I shall be on a boat just off Portugal and heading to Spain, France, Sicily, Italy and Croatia in that order. Hence JBLs will not be top of my list for the next three weeks.......;)

Hi Georgebrook, BonVoyage! Enjoy! ...and just remember: where ever YOU deceide to put the front nameplates- you can always take the grills OFF when you listen so that NOTHING get's in your way of listening enjoyment whilst reminiscing over the tour you've just been on!!!
Lookforward to your safe return, and next post.

Steve

[Ian Mackenzie]

Hi,
I did see Ian's post.. but I could not understand why he chose the frequencies that he did and some of the instructions were a bit (IMHO) ambiguous.
Anyway, the plan is still to listen for a while.. fix the foam surround (which arrived from the US in just a few days after ordering) and let the system settle. Then start a procedure for balancing. Ultimately I suspect it will be a procedure followed by fine tuning according to ear-preferences. We shall see. This is just the start of a long job.

Strangely this morning I noticed the JBL smell reappearing. Perhaps the bass notes have shaken it out of the wood but it is definitely there. It could make a nice aftershave :-)
I am still impressed how non-hi Fi it all sounds.. big, relaxed and nimble!
Thansk for all the advice

http://www.audioheritage.org/vbulletin/showthread.php?6345-Tricky-mic-position-create-random-response-mesure&p=60625&viewfull=1#post60625
(http://www.audioheritage.org/vbulletin/showthread.php?6345-Tricky-mic-position-create-random-response-mesure&p=60625&viewfull=1#post60625)
Hi George,

The boxes look nice.

The tone frequencies are roughly centre to the pass bands of the mid, HF and UHF drivers so it was chosen on that basis.

The purpose of the process is not to adjust the overall tonal balance in your listening roon but to balance the sensitivites of all 4 drivers so you then have a base line to make other adjustments.

As there are 4 drivers (and not 2 as in a two way) its almost impossible to set up these systems by ear without getting the drivers sensitivity matched first.

By a process of deduction you can negatively engineer a flat response from knowledge of the voltage drivers and drivers response as measured by JBL and the "cut" of each L pad as marked in the L pad plates.

The fixed resister pads in the network were chosen to allow a +- range of adjustment for each driver with the L Pad of a known amount of dba.

The only inaccuracy is in the resistive wire element of the L pads and the give in the plastic adjustment knobs and that is why we use a "meter" to measure the tone level at full level on the L pad and then adjust to cut the level a specific db to match zero position at discrete frequency points for the mid, HF and UHF Pad postions, ie - 4 dba, -3dba as the case maybe.

If you have a lot of glass in your room or flat walls I would suggest Baxandall tone controls http://makearadio.com/tech/tone.htm

[1audiohack]

I left my note book so the detailed measurements will follow.

[1audiohack]

More detail.

[DogBox]

Hey 1audoihack, B-E-A-U-T-I-F-U-L pictures, and detail. Seems amazing that those foilcal's mount using those small holes in the 1/2" angle.. and like you said- provision to be able to place them L or R, even with the top baffle rotated... plenty of angle pieces to utilise.
Thanks Barry! ;)

DogBox

[georgebrooke]

Hi Ian,

I just saw your note explaining how you chose the frequencies etc. when setting up your speakers. Thanks for that information. Right now I am awash with possibilities but now that the speakers are domestically acceptable I am just listening to them for a while.
I am still looking at the B4 approach, using the passive crossover components that you sent to me a long time ago.... leaving the original crossover untouched . I do get a lot of contradictory information from various people about the best way forward here.. pure passive, bi-amp, pure active, a mix and so on. A colleague is currently evaluation speaker cables based on CAT 7e and he seems to be getting quite excited about the results. it might be something I pick up on too.. when I stop the listening. We hope to publish the results of these listening tests later this year.

Nice to hear from you again.

best regards


george







http://www.audioheritage.org/vbulletin/showthread.php?6345-Tricky-mic-position-create-random-response-mesure&p=60625&viewfull=1#post60625
(http://www.audioheritage.org/vbulletin/showthread.php?6345-Tricky-mic-position-create-random-response-mesure&p=60625&viewfull=1#post60625)
Hi George,

The boxes look nice.

The tone frequencies are roughly centre to the pass bands of the mid, HF and UHF drivers so it was chosen on that basis.

The purpose of the process is not to adjust the overall tonal balance in your listening roon but to balance the sensitivites of all 4 drivers so you then have a base line to make other adjustments.

As there are 4 drivers (and not 2 as in a two way) its almost impossible to set up these systems by ear without getting the drivers sensitivity matched first.

By a process of deduction you can negatively engineer a flat response from knowledge of the voltage drivers and drivers response as measured by JBL and the "cut" of each L pad as marked in the L pad plates.

The fixed resister pads in the network were chosen to allow a +- range of adjustment for each driver with the L Pad of a known amount of dba.

The only inaccuracy is in the resistive wire element of the L pads and the give in the plastic adjustment knobs and that is why we use a "meter" to measure the tone level at full level on the L pad and then adjust to cut the level a specific db to match zero position at discrete frequency points for the mid, HF and UHF Pad postions, ie - 4 dba, -3dba as the case maybe.

If you have a lot of glass in your room or flat walls I would suggest Baxandall tone controls http://makearadio.com/tech/tone.htm

[Ian Mackenzie]

Hi George,The cat9E is a good poor mans Kimber cable but well worth the effort (as advise by Zilch god bless him).Like all these things if you cant hear the difference your problem lay elsewhere.Not one to be contraversial but assuming a straight wire connection charge coupling Solen Fast caps to the signal path seems to add back a glazed electronic signature not there in the firdt place. Nice way to try and recover a lack of true detail and resolution.No flames please. Just as an observation in imhoIan