JBL LSR 28p self-noise fix?

[Jax]

I like my LSR28p's, but they buzz and it doesn't seem to be related to the AC at my studio. I've taken them to several other locations, even in different cities, and the "buzzzzzz..." doesn't go away no matter where they're plugged in. They've been like this since I got them 4 years ago, and the if anything the buzz is now getting worse.

I'm wondering if there is any known repair or mod that can get the things to quiet down?

And hi there Jim Williams. If you happen to read this - do you know of any de-noising mods for the LSR's? Maybe you've done a few yourself?

[dave-G]

HIJAX

You might want to give a call to Joel at Studio D in Sausalito .. I seem to recall he somehow fought off some noise issues with his (they had a 5.1 rig with those LSR28s)

-dave

[wwittman]

I had one pair that did that.. but none of my OTHERS did.

JBL replaced them.

You might ring them and complain.

[Moze]

I had this exact problem with my lsr28p's. I had 3 separate shops look at the problem, replacing various components. The buzz would come and go. Everyone told me it must be my dimmers... I need to filter my AC, blah blah...Finally found the problem: On the input board, the power and audio wires have the tendency to cross and come in contact with each other. *I took the power wire and wrapped it around the ground to keep it away from the audio and the problem completely went away.

It is a crappy design... but an easy fix. I hope this is the same problem/fix that you need.

-moze

[Jax]

Excellent!! (Rubs hands together with sinister Mr. Burns expression) Thanks for the idea, Moze.

Questions, though: Would you recommend cracking these coconuts open to somebody with very little tech experience? Was it easy to put them back together?

I might try this if I don't feel like I'll end up buying a new pair of monitors by the end of it...

[Jim Williams]

I haven't done any work on this speaker, but I suspect it has the same problem as all the other "self powered" monitors out there. Look at the box. Now, look at a great power amp. Now, tell me how to fit that great power amp into that box.

My recommendation, use the passive models with a great amp. Problem solved.

Jim Williams
Audio Upgrades

[Moze]

Originally Posted by Jax

Excellent!! (Rubs hands together with sinister Mr. Burns expression) Thanks for the idea, Moze.

Questions, though: Would you recommend cracking these coconuts open to somebody with very little tech experience? Was it easy to put them back together?

I might try this if I don't feel like I'll end up buying a new pair of monitors by the end of it...

It is pretty easy... just unplug the speaker and unscrew the lower portion of the back panel (with the inputs and DIP switches). Slide it out a bit and you should see the wires I'm talking about connecting to the board. I think you'll almost HAVE to do it yourself or be there with a tech because the couple of times I sent it to JBL service centers they either didn't do anything or replaced components and never listened to the result because it came back doing exactly the same thing.

Hope this helps some...

-moze

[Jax]

Hey Moze,

I tried your fix and it did help cut down the noise to a more acceptable level, though not all the way gone. Interestingly, I found that wrapping the ground around the power wires 2-3 times actually made the speaker noisier... but it was quieter with one wrap around... strange.

I might try wrapping foil around the audio wires next, to shield them. If that works to any degree, I'm taking off the heatsink to reach the audio wires inside the speaker and fully shielding them. Don't know if regular tinfoil will create a greater problem (read: antenna) or help it go away.

Anybody have a suggestion for the proper shielding material?

Thanks Moze,

Jax

[tINY]

last night I noticed one making a hum-noise...

When I removed the transmitter for the IEM system from the top of the speaker, it went away.

I think these JBL self-powered monitors have a shielding problem in general. I'd move all equipment as far away from them as possible.



-tINY

[Jax]

Originally Posted by tINY

last night I noticed one making a hum-noise...

When I removed the transmitter for the IEM system from the top of the speaker, it went away.

I think these JBL self-powered monitors have a shielding problem in general. I'd move all equipment as far away from them as possible.



-tINY

Good point, though I already had everything as far away from the JBL's as possible. They are unshielded monitors, so it follows that they'd have problems with RFI/EMI/AC field interference. When I get a pair of mondotraps, I'll be able to back the monitors away from gear another foot.

Btw tiny, you're one of the few somewhat-newcomers whose posts are actually worth the time to stop and read. I haven't seen a bad piece of info from you, yet! (lol)

thumbsup

[tINY]

Originally Posted by Jax

I haven't seen a bad piece of info from you, yet! (lol)

Give it time....

I try to catch my own mistakes and I can be persuaded that I am wrong. The whole point for me is to learn things by discussion.



-tINY

[kifaru]

I've had the same problem with mine fo about 3 1/2 years. I honestly believe JBL knew(knows) about the problem and just refuses to acknowledge it. When I bought mine I wasn't doing records with the likes of the people wwittman so this is probably the reason JBL just blew me off. I am now though (thank god for the return of rock). Anyhoo if you (Jax) or anybody else even the JBL guy who may be lurking comes up with a fix I'd appreciate it. I'll even pay for it.

I think I will never buy another speaker made by JBL again but if my loot comes through for what I'm working on the Klein and Hummel O300 D's are going on the bridge.

[soliceseven]

I know this is a real old thread but I just bought a pair of second hand 28P's and they were noisy until i Pulled out the patch bay and patched them directly to my FF800.which is strange since my LSR4326p's didn't make any noise patched the same way. By the way these sound fantastic!!!

[oxide54]

patch bay grounding?

[Ike Zimbel]

Originally Posted by soliceseven

I know this is a real old thread but I just bought a pair of second hand 28P's and they were noisy until i Pulled out the patch bay and patched them directly to my FF800.which is strange since my LSR4326p's didn't make any noise patched the same way. By the way these sound fantastic!!!

This whole thing, like several other "noisy self-powered monitor" threads here, sounds like a Pin-1 problem to me. One really quick thing to try is, if there are any mounting screws on any of the jacks (XLR, 1/4", RCA, whatever's there), tighten them up with the proper tool and see if the noise goes away. A lot of equipment that has actually had the Pin-1 problem designed out of them (IOW are properly grounded) will exhibit the Pin-1 problem if they have loose screws or other hardware. Why? Because the Pin-1 solution is to ground the shields to the chassis through a mechanical connection, and if that connection gets loose or dirty, you are back to having Pin-1 problems.
Best,
Ike