Ampeg 410HE crackling noise - can I disable the tweeter?

Mark Joe · #1 07-23-2010, 09:21 PM

I have an Ampeg 410HE cabinet, and it makes a horrible cracking noise when pushed. I checked all of the 10 inch drivers and their fine; the crackling gets worse when I turn up the tweeter control, but with the tweeter control all the way down it still makes the noise.

I dont even like tweeter sounds, so is there a 'safe' way to disable the tweeter? I dont want to damage anything.. also if anyone has had this problem before and can suggest what might be wrong, that would be helpful.

I dont like the design with the built-in crossover; it is overly complex and apparently prone to failure.

Thanks for any idea anyone might have. -- Mark

craig.p · #2 07-23-2010, 09:40 PM

Step 1: Pull enough drivers so you can see what you're doing.
Step 2: Take copious notes on how the thing's wired now.
Step 3: Rewire the cab to give you the impedance you want -- run the jack directly to the four speakers, bypassing the crossover entirely. There should be a FAQ on wiring somewhere. Read it before you begin. Use the speaker baskets as tie points for the original disconnected wires you no longer use. Use tie wraps, not tape, and make sure the weight of the old wires won't cause them to come in contact with the cones when the cab's upright. It's a really simple job. Toughest part will be chasing down stranded wire and the push-on speaker connectors to crimp on them at Home Depot. Not sure if the wires are soldered to the input jack or not, but you'll know as soon as you pull the first driver, or maybe someone here knows.

JimmyM · #3 07-23-2010, 09:43 PM

btw, tweeters aren't very expensive. you could probably find a better tweeter for it at one of the many speaker sales sites on the web.

Mark Joe · #4 07-23-2010, 10:16 PM

The input jacks go directly to a stacked PC board which goes to the crossover, so to wire directly to the 10 inch drivers from the input jacks would require major surgery. I simply disconnected the two wires at the tweeter, and the crackling went away (well some of it was the amp it turns out so I tweaked that also).

The cabinet is rated at 8 ohms, and it has four 8 ohm drivers, so I wonder what the impedance is with the tweeter?

Also, am I going to damage anything by disconnecting the tweeter/am I asking for a future failure... that darn circuit board is in the way between my amp and the 4 drivers and I dont want anything to fail thereby ruining a gig...

I guess the other option would be to jury-rig a new 1/4 inch input and bypass the board and go straight to the drivers, but thats an ugly solution for a good-looking and otherwise wellbuilt USA made ampeg cab, and I dont want to change the original design in case someday I want to sell the cab...

JimmyM · #5 07-23-2010, 10:20 PM

piezo tweeters have minimal impedance so they don't really affect the overall impedance of the cab. and no, you won't damage anything, and to be honest i think it'll sound better without it. when i get supplied cabs with tweeters on gigs, i almost never run them.

Jerrold Tiers · #6 07-23-2010, 10:29 PM

Most of those don't have piezos...... don't recall every model though..... Foster horns are pretty commonly used on a number of cabs.

The tweeter tends to reproduce the clipping sounds of the amp, so it can make a bunch of obnoxious noises without actually being bad.

The best plan is not to just disconnect the tweeter, but to disconnect the whole crossover for it. The other speakers are wired direct.

As for the impedance, by the frequency the tweeter kicks in at, the impedance of teh LF speakers is probably at least 12 to 16 ohms........ it goes up with frequency.

Mark Joe · #7 07-23-2010, 10:31 PM

hmm interesting - I suspect now that the tweeter WAS amplifying problems with my amp (Gallien Krueger RB400)...

in spite of the amp crackle, it does sound overall tons better with the tweeter disconnected so that is definitely something I want to stick with.

... but how to bypass the crossover cleanly... I think all 4 inputs are hardwired right to the circuit board I will look more at it and see if I can move it out of the way enough to wire straight to the drivers...

JimmyM · #8 07-23-2010, 10:39 PM

Quote:

Originally Posted by Jerrold Tiers

Most of those don't have piezos...... don't recall every model though..... Foster horns are pretty commonly used on a number of cabs.

that's cool..i stand corrected.

David1234 · #9 07-23-2010, 10:43 PM

Once I used a venue-provided ampeg cab, with my own amp pushing it, and I got some distortion through it.

But the distortion was from my bass's battery going flat. The cab just did a fine job of letting me know.

Question for the OP: Are you *sure* it's the cab that's the problem?

[If you can't learn by others' mistakes, you have to make so many more of your own!]

Mark Joe · #10 07-23-2010, 10:55 PM

I think you may be right about the tweeter amplifying another problem..

The more I think about this, the more suspicious I am that there may be corrosion in my amp (it is after a 1982 amp), expecially when I could get the crackling to lessen when I tweaked the tone knobs and changed out the speaker cable... When I originally heard the noise, I didnt hear the cracking when running the same rig through my Acoustic 610 cabinet, so I assumed it was a problem with the Ampeg cabinet.

I think another application of electrical contact cleaner on the pots and input/output connecters of my amp is in order - the tweeter might be the key to me making sure I get my amp cleaned up properly.. but intermittent failures (such as noises that only happen when being pushed hard) are difficult to troubleshoot.

But in general, at the end I really just want a reliable, good sounding rig with little chance for unexpected problems on stage, and I like the sound and headroom of 10 10-inch drivers (the two cabs)..