Well my buddy gave me a pa speaker for my birthday on Friday, and I can't seem to get the squeal out of it with out turning the dyna mike almost down to nothing. I've mounted it to the driver side fire wall, ran the wire through the fire wall up the A post across header liner trim to my roof mount Cobra 29 LTD Classic. The <a href="http://www.motorhaven.com/"><a href="http://www.motorhaven.com/"><a href="http://www.motorhaven.com/">head liner</a></a></a> trim on that side also shares the <a href="http://www.motorhaven.com/"><a href="http://www.motorhaven.com/"><a href="http://www.motorhaven.com/">antenna</a></a></a> co-axe for a Wilson Little Will mag mount. The power line is run on the opposite side.

When I crank up the dyna mike past the 2nd bar it squeals when I talk. If I bring it down to about a bar and a half it's clear but not as loud as I'd like it to be. There's no markings on the speaker to tell what brand it is, but it's about 8 inches long and 5 inches around at the end of the horn. It's not light, it has a good weight to it so I don't think it's a cheepy.( My buddy only buy's quality gear) My radio has a conax board and has been tuned and peeked. Could it just be too much feed from the radio? Too light a wire gage? Wire routing? Fire wall mount too close to radio?

I'm running an Astatic power mike but I had it turned right down.

Any thoughts on this folks I need it to be much louder so I can poke fun at bass boom ricers and nuns at cross walks

 

Unless it's the impedance of the speaker,I would say the problem is the MIC.

Go ahead move it.
Make a copy for electrical forum too.

 

The squeal is feedback from the pa speaker into the mic. You need to locate the speaker farther away from the mic and not have it point anyway near it, like maybe up front somewhere. Don't know about Astatic mics but a unidirectional one will help cut the feedback too. BTW, does that mic "chime" when you key down? If so, that will start the feedback cycle. The gain isn't helping you either, you just have to play around with it until you get something reasonable.

Barry

 

The squeal you are hearing is basically an unwanted amplifier output oscillation that is triggered by the sound of your speaker feeding the mike; assuming you're not cranking the speaker too high, I would theorize that the amplifier was not correctly tweaked at the factory or it is a lower-quality amp. Some kinds of amplifiers outputs are tuned to provide a better power output, but with that power comes an instability that lurks just below the nominal operating range of the amp. It is a complicated science, I would have to explain Smith charts, and manufacturing processes that are at best,.. still an art. Each amp that comes from a production line has its own little personality and may also have latent defects that were missed in the testing process. If a standard mike doesn't help your problem , then you may have a poorly tuned amp, broken amp, or stressed-out amp output driver. The point is, a well tuned amp is less likely to start oscillating when using a sensitive mike. Good Luck

 

Try pointing your speaker down, like between your engine and fender. Someplace where the sound can get out, without a bunch of sound waves getting back in the cab. Up under the bed, near the rear <a href="http://www.motorhaven.com/">bumper</a> would be a good place. Have it point out the rear wheel well. That way you could pull up next to the thumpers at a stop light and blast them at 130Db
Really old carbon mics used to have funnel shaped input that would cover your mouth to help block out unwanted sound..lol..kind of unsightly, but it works. You could tell people it's a gas mask, at least as good as duct tape...

 

Well it's 8 am (mental note to self, don't work on pa speaker before the rest of the family is up on Saturday morning)

I've got it working great now! I moved it to the front passenger side just behind the grill pointing down.

It's real loud, I tried it out and woke up just about every bird for a mile ( it was like a Hitchcock movie). My wife even got out of bed and came out just to call me names. And what do I do? I reply over the pa with a simple "good morning to you too honey"

Some how I don't think this will be one of her favourite toy's.

Lucky my nearest neighbour is over a mile away with lots of trees between us!

Thx for the input guy's

 

Idea farm:

1) Mount it with rubber mounts - to reduce the vibrations that may carry audio from it along the frame and body back into the cab.

2) Put a 2:1 transformer on the line to the speaker to drop the volume, if you normally have to cut back your mike or gain settings from where the radio is usually set at.

3) It may be possible to get a delay module, which would cancel most regenerative feedback.

Just a few thots from the top o' my punkin' haid...

 

[QUOTE]Originally posted by Greywolf
[B][b]Idea farm:

1) Mount it with rubber mounts - to reduce the vibrations that may carry audio from it along the frame and body back into the cab.



Good idea Wolf!

I've got it working good now "real loud" but I will go with the rubber mount idea. I can actualy feel and hear the vibration. I've got some real thick neoprine that should do the trick.