JBL Professional 8350 and 8340A Technical Strip down...

LittleNipper

Well-known Member
I've got a few JBL Professional 8350's and 8340A's, so I thought I would do a strip down as I wanted to have a peak inside.

The 8350's are a tad heavier that than the 8340a's, but only by a kilo. But, as you look at them side by side they look identical. The only difference being the name on the sticker on the rear.

Four screws hold the front baffle on ( these are at the top and bottom outside edge ). One thing that was interesting is that the baffles are
interchangeable. All of the screws for both the front baffle and the actual frame of the speaker are all the same and interchangeable. I'm guessing this will
be the same for the 8320's as well. However, I don't have any of these, so can't tell.

As far as I am aware there are four different ways of mounting these onto a wall :-

1. Bent steel bars. The ones I have ( four of them ). However, the holes on them seem a little 'off' nothing a drill and HSS drill bit would not resolve.
2. Pivotting steel rod. Well, it was only after buying these did I think - how the hell do I fit them against the wall. They screw into the back of the speaker
without a problem. I am sure I will figure this out at some point.
3. K&M 24471 Brackets with appropriate plate on. I had these left over from some MK Sound speakers. These are nice as they pivot and twist. So in a 9.1 system you can easily angle the direction of the speaker - Speaker wall mount
4. JBL's own fixed angle bracket. I am waiting for some more 8340a's to turn up with these on - https://jblpro.com/en-US/site_elements/2516-quick-mount-fixed-angle-bracket-for-8330a-and-8340a.

The screws you use need a PH2 bit and they go into the rear of the case in brass female thread. Nice, good solid fit. I'm sorry, as I've not had to buy any more screws I don't know what the thread pitch / size is.

To dismantle the speaker, remove all of the screws on the rear. Don't worry, the frame will not fall out, as one screw that is positioned behind the base driver keeps the case on.

Flip the speaker over and give it a shake. You will find some of the screws don't come out, so they might need some more encouraging. Then lay the speaker on it's back, resist giving it a belly rub. If you now remove the 8 screws ( PH2 ) holding the base driver in. I then held the speaker up a little and gave it's back a tap and the base driver dislodged itself.

Now, remove the connectors on the rear of the base drive ( making a note of where each one went ) and then, this will reveal the final screw holding the case together. Remove this. Before removing the front of the case, disconnect the compression driver for the horn from the motherboard.

I did not attempt to remove the compression driver, but this is fixed to the moulded wave guide that makes up the front of the speaker.

There is a rubber seal all the way around. This might be a little stuff to remove. It does come away with the front of the speaker. Don't worry if it drops off.

You can now see the internals. This is from the 8350. I will do the 8340A another time and update the thread if anyone is interested.

The base drive is pretty substantial !! Next, I cleaned the rubber seal and as it was a bit dry put some petrolium jelly on it to feed the rubber. Everything went back together very well....

When you buy these, I think, over time the cones get replaced / fixed and depending upon manufacturing the damping foam inside might be different. The foam inside is mechanically fixed to the base of the speaker enclosure. I noticed one of these metal fixers has dislodged itself and stuck to the magnetic code. However, as my ear is attuned to the compression driver more than anything and they are on surround duties, I doubt I will tell after a beer or two !

On the last photo, you can see where the seal has and has not had the petrolium jelly on - top, just to the left of the port.
 

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LittleNipper

Well-known Member
Got a set of four 8320's. They are actually smaller. Thus I cannot change the front baffles. Also, the hole position for wall mounting isn't the same. I'm looking at using these for height Atmos speakers on either a .4 or .6 system. Just need to think about how to mount and tilt on the ceiling.
 

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