Distortion and Xovers

[bombardon73]

Hello to all the xover freaks, I have a problem concerning a xover.

Let me first try to explain how the distortion sounds like and when it occurs.
The distortion sounds like loud ticks or crackling thats coming from the midrange speaker (three-way system). This occurs with midrangy sounds (twangy guitars and some vocals). You really have to play LOUD to make the speakers create this noise, the problem starts with approx. 150 watts.

The problem is NOT the amplifier (I tried several, also a 600watt BELL PA amp), it's also not the speaker.

The xover point is 400hz 12db/oct (wich is pretty common with three-way system).

I know now that the distortion indeed occurs with the highpass to the mid speaker ( I made a test setup with only the midrange speaker and the inductor and capacitor).
Low and behold , the distortion disappears when I take away the inductor. So if I only use the capacitor the problem is gone but I have only 6db/oct then, wich is not the thing I want.

So the question is, why do I get distortion with a 12db/pct xover (or higher order).

Also, I tried several kinds of inductors. The ones I didn't try are the really expensive ones with the windings glued together or the tritec inductors. Maybe it is indeed some resonance of the inductor (they indeed can create vibrations when they are fed with lots of power).

Ok, I really hope someone can shed some light on this problem.

[pinkmouse]

Sounds more like you're bottoming out the voice coil in the drivers rather than a crossover problem.

Post a schema of your crossover, that will help. you may be trying to cross the midrange driver over too low.

Or you could turn it down!

[bombardon73]

Pinkmouse, if you read my post correctly you could conclude that it's NOT the loudspeaker. It can't be because when I run the same speaker with a 6db xover it WON'T make that distortion.Eventhough the excursion of the midspeaker is much bigger because of the 6db xover it won't distort. (I also tried other speakers, same results)

It won't make a difference if I would post the schematic, changing the inductors or the capacitors value won't fix the problem.
Only if you would xover at e.g. 3000hz the problem won't occur!

[paulhfx]

Anyone else dare to guess at the problem?

Paul

[hermanv]

If you have used a iron/steel or ferrite core in an inductor they are famous for making exactly this sound when the current is high enough to cause the inductor to saturate.

If this could be the problem, use a bigger inductor, lower the current (it is ampere turns that saturate a coil so either less amps or less turns will help, maybe you can move the crossover freq) or better yet use only air core.

[bombardon73]

I allready used regular air conductors, but maybe I need some really big ones like these http://www.speakerland.com/TRAFOKERN-SPOELEN.htm .
It's a Dutch site, but these are some of the most expensive inductors, maybe these are what I need, or not.

[hermanv]

Air core inductors can not saturate so this does not appear to be your problem.

Perhaps an inductor in the woofer is indirectly causing the problem?

Any chance the capacitors are arcing internally? A series coil capacitor combination will have a resonance. At this frequency the voltage at the coil capacitor junction can become very high. You tried other inductors, did you try other capacitors?

After that, I too think maybe you voice coil is bottoming. or in other words I have no further ideas.

[DSP_Geek]

It could also be the air core inductors arcing if there's circuit board foil underneath them. I had inductors arc between the outer winding and the inner lead-in wire, which was a bugger to find on a crossover I was fixing. The manufacturer ended up doing a design rev.

[ShinOBIWAN]

I've also had these clicks on a project I did sometime ago using a PCB to mount the XO components.

It turned out that I'd damaged one of the caps whilst soldering, either with heat(most likely) or mechanical stress, I replaced it and the problem went away.

Best way to describe the sound is occasional pops that would occur when playing loud'ish.

[bombardon73]

I also did try several other Caps and electrolyts, problem stays.
This is really weird.