Using choke coils in SERIES with piezo tweeters?

[Cal Weldon]

Many moons ago I used to take somewhere around a 1-5mH choke and run it in series with piezo tweeters. 5mH seems to ring a bell as the one that made a really noticeable difference, if I remember correctly.
Not sure if this old hat, or if anyone bothers with piezos anymore. But if you had or do, I found this a great way to cure that damn piezo sound harshness and give the tweeter a nice boost, yes BOOST at the upper end it needed. Now I'm not sure why I tried it in the first place as a choke doesn't seem like regular business when comes to running it in series with a tweeter .

Are there others who have done this? Am I too old and out of touch? I'm only forty something for gods sake, but I never hear about this. Was there something I was doing wrong there? Screwing with someones amp or worse their ears?

Disclaimer: Unfortunately budget constraints allowed me to become all too familiar with piezos.
Big ones, small ones, fat ones, skinny ones.

Cal

[kelticwizard]

Here is an Application Note on crossing over piezoes:
http://www.ctscorp.com/components/Da...ation_Note.pdf

No mention is made of chokes.

I have never tried what you said. However, if you have nothing else hooked up to that circuit, I would not recommend it. A piezo is basically a lossy capacitor, and running an inductor and a capacitor in series results in a resonance point where no impedance is present-hence burnt out amp.

Running an 8 ohm or even 20 ohm resistor across the piezo might make such an arrangement possible, I don't know. But hooking up a choke and piezo together in series soundls like not a good idea.

[phase_accurate]

A piezo is basically a lossy capacitor, and running an inductor and a capacitor in series results in a resonance point where no impedance is present-hence burnt out amp.

It's possible that this resonance-point was responsible for the EQing Cal liked.
As far as the resonance goes: A piezo tweeter seems to be a very lossy capacitor and might therefore not present a too dangerous load in series with an inductor. To be really sure one has to perform measurements though.
I remember that some speakers a workmate once bought (at the end of the seventies) used a piezo tweeter with some circuitry that was also including an inductor.

Most users don't get the maximum performance out of their piezo tweeters anyway by simply paralleling them directly to the woofers. So I think there is quite some room for improvement.

Regards

Charles

[Cal Weldon]

Hi Charles,

Thanks to you and kw for the responses. If it is not going to pose a problem to the amp then I think someone out there might want to do some tests and let us know. I always found those tweeters were really shrilly, even the one that had a deep throat [approx 5-6 inches overall depth] and about a 3X8 front face. This to me was the only piezo I got to use that sounded half decent.

So try the experiments with different coils and see what effects you can get out of it. I am simply not set up to do it but would be really interested in anyone who can. I'd like to compare the graphs of different coils vs. without. I always enjoyed the "improvement" this made.

Thanks to anyone ahead of time,

Cal

[Andy G]

yes, a piezo CAN be used without a cross-over, but they will sound rather harsh and this is the reason for their bad press !!

there are articles etc on the page below that may help you.

http://users.tpg.com.au/users/gradds/piezos.htm

[Cal Weldon]

Hi Andy,

Back to the original post. Have you ever run a choke in series with a piezo?

Thanks

Cal

[Andy G]

nt...

[kelticwizard]

Maybe a good idea would be to hook a choke in series with a piezo and a resistor of some 10 ohms, and do an impedance test.

Then run a choke in series with a piezo in series and a resistor of 5 ohms. Run an impedance test.

If that turns out okay, then go down to lower resistances and finally no resisitance at all. That way you don't risk a burnt out amp.

Just a suggestion.

By the way, Cal, did you find any success in looking for that online tone generator for the Mac?

[Cal Weldon]

Hi KW,

I think I was running a dual 12" [cheapie] system with no choke on the woofs and a 5mH air core on those long throat tweets.

That would have been the strangest crossover I ever did.

Great party speakers for a buddy though...

[Cal Weldon]

Forgot,

The Sound generator downloading was beyond my abilities.

I'll get my buddy, the mac friendly tech dude to do it.

Thanks for the link KW.

Cal