Motorola Piezo HF any good?

[rotaspec]

I just picked up a couple of Motorola KSN1038A piezo horn tweeters cheap and wondered if anyone had used them?
Or would they make good paperweights

I know being high impedance devices, they will take a little matching, but hey no xover

Gary

[norman bates]

yup, using them correctly is tricky.
do a search on audioasylum.com for 1038a under high efficiency (or author djk and subject piezo).

People usually misuse piezos and they will spit at you run that way.
There are only a few of the original motorola piezos that are good also.

I used mine with a 60ohm resistor in series, active crossover 24db at 5khz...........
It has a nasty resonance at 4.5khz, but a LR crossover is 6db down at crossover point.

To use it best (correctly) you have to use a 25v transformer backwards and zobel / crossover amp side, a 60 ohm resistor piezo side, but you can get a 24db slope and an extremely clean (undistorted) tweeter.

Norman

[Godzilla]

I like that tweeter.

Piezo Super Tweeter

Godzilla

[wintermute]

Originally Posted by rotaspec

I just picked up a couple of Motorola KSN1038A piezo horn tweeters cheap and wondered if anyone had used them?
Or would they make good paperweights

I know being high impedance devices, they will take a little matching, but hey no xover

Gary

I've used them. They were great for Party speakers, but I wouldn't call them HiFi I ended up reverting back to textile domes, but part of the problem I had was I WAS using them with a pre-made crossover and they were supposed to be filling in from 4K up, when they could really only do from 5K. Mine were like the one on the left in the link Godzilla posted.

Oh and they won't make good paperwieghts either as they weigh next to nothing

Tony.

[Conrad Hoffman]

IMO, they can be used successfully, but you do need a crossover and you should drive them from a resistive pad so they don't look so capacitive. Parallel them with a low value resistor like 6-10 ohms, then a series resistor, fed from a crossover. It may take a lot of tweaking to get the response you want but they can sound rather good. Given what a conventional driver can do however, I'm not sure it's worth the effort.

[PeteMcK]

planet10 has a page buried in his website somewhere about how to use piezos, but I can never find it when I need it... Just last week I used a pair of K1005s as super tweeters, I think they sound good. Aiming to xover at around 9 KHz, I used a 22 ohm resistor in parallel, then a .8uf in series (.47 + .33 so I can tweak), this flattens out the peak at ~ 4Khz, and another 22 ohm resitor in series to cut the level down to where I wanted it.
Planet 10s page has a formula for calculating the C value. You can use them without a crossover, but that's what's given them a bad rep...