none radio related question, dose anyone know if these reduce their output power with wear? i've been using 2 disco horn ones, 1 of them the output power seems to less, is this normal?

Yes - they are crap. Best avoided, however as you've got them already they only cost a fiver to replace.

Are they these rubbish things for three quid?
http://www.ebay.co.uk/itm/291765393846

If by "wear" you mean not driving them appropriately, then yes - but I've not heard of them reducing output due to usage. Like any loudspeaker driver you can blow them and any additional surrounding circuitry.

Hello Mr Northeast!
Ive used these many times and although they are cheap and capacitance based? I have never known them to degrade over time?
One thing to bear in mind is the quality of your audio? With MP3 widely used these days, HiFi definition is severly compromised!

their actually the retanglar horn ones from ebay but the same as above, drove one with a frequency from a 555 timer it started resonating at other lower frequencies, its pretty crap, looked inside, there was a large crack down the middle.

i’ve been using audacity to monitor the sound level, pretty sure when I drove it in the past tested it would go over into red, i’ve hooked up some speakers out of tv, it dose go over into the red , i think they both duff.. I had been putting 28v throught them for sometime, think they might of gone, now looking for replacements none piezo ones.

Their funny things to drive anyway because of the impedence, know some people say you should use resistors..

Lol yeah cracks in the driving element are not good!
Also im intrigued why youd choose to use a 555 to drive them? which in basic form is effectively a square wave oscillator?
I used to use them in banks of four per stereo channel and the high frequency response was excellent!

The only piezos worth using are of the Motorola variety. Anything else should be placed firmly in the bin.

I remember a reggae "Sound System" I saw in Harlesden some years ago. They had about a dozen wardrobe-sized speakers which each had a 24" bass driver and four piezo tweeters. When they'd finished wiring this lot up, they fired it up and put on a record. All we could hear was a bowel-shaking bassline and a bit of tizzy high-hat - the vocals and other instruments were entirely inaudible! Their "engineer" announced that it was the best "Sound System" he'd ever heard!

Albert H wrote:Their "engineer" announced that it was the best "Sound System" he'd ever heard!

Ho ho ho, I bet he did! It wasn't Mark Weiss was it?

Dai Pole wrote:The only piezos worth using are of the Motorola variety. Anything else should be placed firmly in the bin.

About 20 years ago I had a small cabinet of those with 5 in and they didn't sound too bad to be fair.