singing x-over

[ton def]

I was testing one of my x-overs on the bench. Hooked up the woofer leads, low pass working. Hooked up the tweeter leads and had extremely little sound output. Figuring that something was amiss, I disconnected the tweeter leads. Well I still heard music, with NO drivers hooked up. The only thing that I can attribute this to is one of the coils ? Anyone see this before ?

 

[system7]

Yup, coils interact.

Placement of coils in crossover networks

This setup produced a high-pitched whine from the tweeter. The multimeter produces an approx 1kHz test tone to measure inductance in the 1mH ferrite coil. There is an effect from the metal ground plane too. A silver ashtray in this case. Hence 0.827mH reading.

 

[AllenB]

I've had singing from inductors that had windings secured only by shrink wrap. Capacitors can behave badly too.

You could pot them..

 

[system7]

Ah, right. No drivers. Just coils singing. Sounds reasonable. BTW, crossovers with no drivers connected can be an awkward load for amplifiers.

Good to see you again, AllenB. You can't believe how bad it's been here since you went away.

 

[AllenB]

For a capable lad such as yourself? Thanks Steve. Are you still listening to paper coned tweeters? I always thought you had a good case there vs. domes.

 

[ton def]

I appreciate the replies gentleman.I took the x-over apart and started from scratch.I had 9 components crammed onto a 4x4 inch board. I placed the larger coil flat,and the smaller coil on its side.Made sure I had no cold solders or shorts. Tested on the bench,works and sounds good.

 

[wolf_teeth]

More often than not, the caps will sing without drivers connected, some to the point of being very clear and actually quite loud.

Later,
Wolf

 

[ton def]

More often than not, the caps will sing without drivers connected, some to the point of being very clear and actually quite loud.

Later,
Wolf

I am not an electrical engineer,but have some knowledge of electronics. But I am having trouble understanding how a cap (poly) could reproduce sound. With the inductor , I can kind of see what is happening.

 

[djk]

"I am not an electrical engineer,but have some knowledge of electronics. But I am having trouble understanding how a cap (poly) could reproduce sound."

Caps are a bit piezo-electric.

"the caps will sing without drivers connected"

Yes, in a 12dB crossover. The unloaded network is a dead short at its resonant frequency, so a lot of current is flowing.

 

[phase_accurate]

Yes, in a 12dB crossover. The unloaded network is a dead short at its resonant frequency, so a lot of current is flowing.

..... and quite a high voltage accross the cap at resonance.

Regard

Charles