Hifi Journey, Speakers

Building the 4343

My JBL 4343 are clones of the original JBL 4343, built as close as I could for now. It all started several years ago when I first decided I wanted to build a big mid 70’s. Back in 2011 I started to collect drivers for a 4345, because if you can – why not go big?

I was successful in collecting the following:

224201″ horn drivers
22307Short midrange horns
2224518″ Bass drivers
2C8R2245H18″ recone kits
2C8R2122H10″ recone kits
12123H10″ midrange driver with broken cone

But then “life” happened – I got a girlfriend and she becoming homeless the same time as me moving into a bigger apartment, meant we moved in together. Lacking proper space, I stored all the equipment in a tall closet. Then one night I woke up with the sound of a shelf collapsing, causing everything to fall to the ground. the horns shattered, the 18″ were warped. It was pure horror!

I was devastated, so I gave most of it away for the price of the recone-kits to a fellow collector – I needed my bad conscience to not be reminded of my deeds.

Years went on and I collected several JBL monitors, among which were several pairs of L100’s – they all came and went and I realised the dream of those big boxes weren’t dead.

JBL L-212 and JBL L-100 Century
L100 and L56

So I started again to gather information and drivers. The choice of speaker changed as well (because of a space limitation, I needed roughly 10cm per side of my Hifi-wall, with the 4345 – so it became the 4343) which also has the benefit of having a symmetrical baffle, with all drivers on a straight line.

It is important to note here, that regarding drivers, some are extremely hard to find – this is for example the 2121A drivers – let alone recone-kits for them. secondly the bass-driver, 2231 Can be hard to obtain. 2405 and 2420 are not as hard, as they were widely used for a long period of time, both in PA systems and in hifi use. I was successful in obtaining a pair of LE85 with horns in pristine condition, and shortly thereafter I sourced 2405 and replaced the diapraghms with new ones from JBL. The bass-drivers were harder, but I managed to get a pair of 2231 with a 2235 cone in it – which was and is the JBL recommended replacement cone. (Actually I also bought a pair of 136 with 2231 cone kits – just for the hell of it!) All I was missing now was those damn 2121 speakers.

I started to ask around forums for the use of the 2122 or 2123 drivers instead. the verdict was clear, the 2122 could work fine, BUT it had a slightly different frequency response that the original network didn’t account for – but the 4345 network did(The 4345 uses the 2122H).

At that time the impossible happened, and on Ebay in Belgium a person listed a pair of 3145 networks in perfect condition (!). This is huge since, being an originalist I knew the network would be a challenge since the tapped autotransformers aren’t something you can buy – so the best one can do in the DIY route is something that works similar, not electrically identical.

That sealed my fate for now – I bought the networks and a pair of 2122 baskets along with 2122 redone kits. That was that, I had the content including an original JBL network. 

The JBL 3145 networks
The drivers

The next problem was the cabinets. Originally these are made of 1″ thick particle board. Living in Denmark that is a bit of an issue, since we don’t have imperial standards, so I bought 12mm in duplicate that I could then sandwich for 24mm thickness, a bit lighter than the 25mm original, but in a sandwich which should increase structural integrity and density a minor amount. Sandwiching panels was a smart way to also make lock-miter joints, all the way around.

I gathered all the information I could from fellow collectors through Audioheritage – was looking through forum threads and posts for all the info I could gather to make a CAD drawing of the enclosure.

Waiting for the warm summer-weather and the rain to stop, and off we went. They are big – also bigger than I could fathom from seeing pictures and measurements.

After making the cabinets I went on to the wooden trim, the solid walnut pieces were milled down and cut at a 45 degree angle and glued in place.

Veneering was done also in walnut, and applied using an iron, the blue colour was the hardest to obtain, and it took a total of 16 different samples, that I compared to the baffle of a 4333, in sunlight, to get the right sample. (80% NCS 6020 and 20% RAL 5014 on a shine 10 white base, which probably isn’t useful as different countries have different brands and different brands have different bases). The end result was spot on!

After applying the JBL mixture of Linseed oil and Gum turpentine, and waxing with bees-wax, eight months after I bought the horn and driver, I could finally give the system a first listen. And boy, was that worth the wait!

Link to the audioheritage thread: http://www.audioheritage.org/vbulletin/showthread.php?40653-Building-a-4343-Clone

Link to the Vintagehifi.dk thread (Danish): http://vintagehifi.dk/forum/viewtopic.php?f=565&t=11220