Help - questions on recone of 2203H

[jtalden]

I have a JBL 124H - same as the 2203H. It is now buzzing. On the bench with an osc it was quiet at very low freq and then it buzzed as soon as the freq rose a little. Buzzing started at maybe 20 to 40 Hz. I didn't go up much higher. The sound is like the cone is split, but with careful inspection I can find no external problem with the cone, spider, or surround and there is no rubbing of the voicecoil when deflected by hand even with with a little off-center pressure - all feels normal.
I don't know what is wrong, but it is a very good driver and I would like to repair it. I use it as a subwoofer in my theater (one of a matched pair).

Since the JBL recone kit is NLA I am considering options and need some advice. There is an aftermarket recone kit, but I am told it does not include the mass ring. This makes me think that the parameters may end up more like the 2202H instead of the 2203H. I really need to keep the the low Fs.
The nominal TS parameters for this 2203H were; Fs= 16, Qts= .14, Vas= 14.1 (the 2202H was Fs= 50).

A rebuilder offered to reuse the old mass ring when he did a rebuild with the aftermarket kit. I am tempted, but not sure if this is will work out. I assume this would lower the Fs and raise the Qts and Vas. I would not mind a resonable increase in Qts and Vas, but I don't know of all the potential problems. I can measure the parameters after the fact, but who knows where they may end up (or for that matter where they would be without adding the ring)? Has anyone any experience with the aftermarket kits?

I think the 2202H, 2203H, 2204H, 2206H all use the same frame and magnet assembly, but I am not even positive of this. There may even be other options I am not aware of.

It appears the JBL 2206H OE recone kit is still available. I could use it, but it also has a much higher Fs (52 Hz), Can the mass ring be placed on this coil former? At least I know where the parameters start and that it is a good kit. I am even considering using this kit "as is" even though I will need to EQ the FR very heavily for my situation.

Other options??

Has anyone any experience with these matters and can offer some thoughts or guidance?

Thanks for any comments!
John

[subwoof]

I have seen a number of issues with the mass ring 12's ( 2203/2124 and 121 ) and one issue is the joint where the spider meets the voice coil former / cone.

On 3 different units this had cracked and of course it only shows up when power swept on the bench.

Another issue is the mass ring coming loose when it gets driven backwards onto the magnet.

In any case I suggest you take it ( and the mate if same age ) to a real JBL service center and remove the dustcap to inspect.

The foam inside should be replaced anyways and the gap cleaned. This way the gap and some of the former can be inspected and most probably your problem found.

Simple 2 part epoxy carefully applied fixed all 3 of the 2203's that had this problem. The spider is thinner and more flexible so are prone to excursion damage.

sub

[jtalden]

Thanks Subwoof!
I will discuss this with the rebuilder I have used and see if they are confident with the task.
John