Help needed: JBL 2470 distorts

[dubai2000]

Hi all, some time ago I picked up four JBL 2470 drivers. After a while I noticed that one of them distorts at certain frequencies (for example when listening to solo piano). The diaphragms installed a the phenolic ones which look okay to me. So what can I do to get rid of that distortion.....any suggestion/help will be appreciated. Thanks in advance. Wolfram

[Rolf]

Hi all, some time ago I picked up four JBL 2470 drivers. After a while I noticed that one of them distorts at certain frequencies (for example when listening to solo piano). The diaphragms installed a the phenolic ones which look okay to me. So what can I do to get rid of that distortion.....any suggestion/help will be appreciated. Thanks in advance. Wolfram

If you switch channels, are the distortion on the same driver?

[dubai2000]

No, have not tried that, but moved the drivers to my second rig....and I doubt somehow that the same driver went to the same channel again.
Wolfram

[Mr. Widget]

After a while I noticed that one of them distorts at certain frequencies (for example when listening to solo piano).

Piano solos are excellent for finding damaged diaphragms. It is possible that one or more of your diaphragms have been replaced and the person replacing them didn't get one or more properly centered. Sometimes it is very difficult to do, and according to some of the professional reconers on our site some diaphragms simply won't fit right.

I'd suggest you remove the buzzing diaphragm and reinstall it following the guidelines posted here. You may have to some searches. It would be best if you could have someone experienced in this help you. Unfortunately those diaphragms have been discontinued so if the diaphragm is too warped or otherwise damaged, you may have a hard time replacing it.


Widget

[Fred Sanford]

Piano solos are excellent for finding damaged diaphragms. It is possible that one or more of your diaphragms have been replaced and the person replacing them didn't get one or more properly centered. Sometimes it is very difficult to do, and according to some of the professional reconers on our site some diaphragms simply won't fit right.

I'd suggest you remove the buzzing diaphragm and reinstall it following the guidelines posted here. You may have to some searches. It would be best if you could have someone experienced in this help you. Unfortunately those diaphragms have been discontinued so if the diaphragm is too warped or otherwise damaged, you may have a hard time replacing it.


Widget

I had a similar issue with one of my old 2470s, just needed to be aligned
and took me a few tries. Ended up selling them to a friend with two extra NIB diaphragms, so he should be pretty set.

je

[dubai2000]

Thanks so far for the input. I got those diaphragms from a forum member and to my inexperienced eyes the look no different to second pair of non-buzzing 2470s I picked up later.

Alignment of diaphragm? That might indeed be the issue...I did some search here but either I didn't hit on the right key-words or am simply a bit Internet blind today .

So can you perhaps guide me a bit through that procedure or simply point out a relevant thread?

Thanks in advance.
Wolfram

[edgewound]

So can you perhaps guide me a bit through that procedure or simply point out a relevant thread?

Thanks in advance.
Wolfram

http://audioheritage.org/vbulletin/s...9&postcount=14

Maybe this will help...I hope.

[dubai2000]

Great read.....thanks a lot. Unfortunately I do not own a test tone generator, but I know someone who does (though he lives quite a distance away from me).
But I certainly start looking for any kind of debris that migt have found its way into the gap or slits in the phase plug.

Wolfram

[rs237]

Hell Wolfram,

You can also use a CD with test tones. If you own a PC with a sound card, there is software to generate test tones.

regards
juergen

ps In Germany, where do you live?

[edgewound]

You can also download a signal generator for free as part of WinISD Pro.

Go here for the free download:

http://www.linearteam.dk

[dubai2000]

Hi Juergen,

I live in Essen......and you are located in....?

Wolfram

[rs237]

Hi Juergen,

I live in Essen......and you are located in....?

Wolfram

I live near Bitburg/Prüm ,unfortunately, too far to borrow a synthesizer.

regards
juergen

[dubai2000]

But if you know how to properly align diaphragms, Prüm is not that far from Essen....and I like driving....

Wolfram

[yggdrasil]

Without the tools described you still have the capability of reproducing the distortion, so here's what you can do:

1) remove the back-cap
2) loosen the diaphragm (not much)
3) push the diaphragm in one direction e.g. up
4) tighten the diaphragm
5) try to reproduce the distortion, and go back to 2) if necessary.

This should help you remove the distortion.

[rs237]

But if you know how to properly align diaphragms, Prüm is not that far from Essen....and I like driving....

Wolfram

PM send,
juergen