Piezo horn tweeter question.

[JoeBob]

When wiring up a piezo horn tweeter with a crossover I've read some people say that it's good to use an 8ohm resistor in parallel with it and treat it as an 8ohm driver in the crossover network, other's have said to use a 22ohm resistor in parallel, but would I then treat it as a 22ohm driver on the crossover network?

Basically what I want to know is, I've got two ksn1025 horn tweeters per loudspeaker, I wish to use these with a crossover obviously, what resistor/s or capacitors or whatnot should I put in either paraller or series and what impedence should the crossover be wired up for the tweeters? The woofers and midranges wired up for 4ohm impedence (but I should use the actual DC resistance when wiring up a crossover, right? which would be 3ohm) in case that's important.

I'm looking for the arguably best way to wire these up (I know different people have different ideas on what's best). Thanks alot if you reply.

 

[kelticwizard]

JoeBob:

Here are the application notes for piezoelectrics that Motorola wrote. The piezoelectric division was taken over by CTS, so all the notes now read "CTS" where they used to read "Motorola". I do not know if CTS was an existing company or something created by Motorola to deal with the piezoelectrics.

I have these same application notes in booklet form, which Motorola sent me years ago.

http://www.ctscorp.com/pzt/speakerappnote.htm

Good luck.

[Edited by kelticwizard on 11-25-2001 at 07:20 PM]

 

[kelticwizard]

Here is their lineup as well:

http://www.ctscorp.com/pzt/ffpzt-home.htm

 

[kelticwizard]

JoeBob:

The 1025 has an irregular frequency response. I believe that it is also sold as the Radio shack 40-1219. To view it's frequency response, go to the following link, then click on the first choice, "2 by 6" Wide Dispersion Horn Tweeter", then click on "owner's manual" for a frequency response chart. http://www.radioshack.com/searchdocs.asp?find=40-1219&SRC=2#

There are other piezo horns with better response. I am not certain, but I believe that the KSN 1016 was very smooth-almost as smooth as a magnetic. You might wish to contact CTS for frequency response charts on that 1016, as well as to double check the 1025.

[Edited by kelticwizard on 11-26-2001 at 12:46 AM]

 

[walker]

Just a quick warning to all. IMHO piezo horns are a cheap solution to handle the top end of PA speakers. Generally NOT the first choice, (or second for that matter) for HIFI speaker systems. Personally they may the hair stand up on the back of my neck, that's before the headache sets in.
I have used them on small PA setups, in this situation they work reasonably well.
Thet are not, an easy, cheap, HIGH QUALITY tweeter.
I'm sure that many on this forum already know this.
Regards WALKER

 

[JoeBob]

Hehe, I'm aware of this, they aren't the greatest quality by far. Although I'd still like to know the best way to hook them up, better not to hook up a not so great driver in an awful way is how I see it. kelticwizard, thanks for the links, it explains alot, I think I've got it now...

 

[Æ]

CONCERNING THE KSN 1025A FREQUENCY RESPONSE.

Hello keltic wizard and others,
The frequency response graph of the 1025A posted at Radio Shack is not very representative of it's true performance, in my opinion. If you want to see a more realistic frequency response graph of the 1025A look at the Piezo Horn article that appeared in the JAES (or reprints) by Jonathan Bost. April 1980 Volume 28, number 4. I personally measured an original Motorolla 1025A. They are/were amazingly flat from 1.9KHz to about 6KHz! From there up the frequency response rises, to ultrasonic (typical horn behaviour), with an (unusual) very narrow and deep notch around 12KHz. I personally think it is the best of the piezo tweeters in it's price range. I've tried all sorts of tweaks to remove the 12KHz notch without success. One way to totally flatten out it's frequency response, is to use a really large amount of series resistance, 300-500 ohms.