audioguru said:
I have an 18" woofer still in its factory box. I can barely lift it. I'm going to sell it at the next local car sound pressure competition. It is probably worth a fortune to some rich kid, but I paid very little.
Years ago I was given all the PA equipment from a local cinema that had been closed for years - it was been converted to an auction house, and the electrian doing the rewiring was a friend of mine.
The amplifier stood 6 feet tall, and was 19 inch rack - it had one big knob for volume (must have been five inches across!) - the output of it was only mono 10 watts!, it used really large old valves :lol:
Besides the amplifier I was given the speakers, these consisted of two 18 inch drivers made by BTH (no cabinets, they were just mounted on a board) - they didn't even have permanent magnets!, you had to provide a DC supply to energise the magnets!. There was also a single tweeter, this was a pressure unit mounted on a beautifully crafted wooden horn, it was latticed - I wouldn't like to have to try and make one!.
Anyway, I gave the amplifier to a collector, and we used the speakers. At that time I was involved in helping to run a rock club, we built two cabinets for the bass units, and hung the horn from the roof - we used a TV frameout transformer to generate the power for the magnets (crude, but it didn't cost anything, and it worked for years). Obviously with such old speakers we didn't have a clue what power rating they might be, but we fed them from a 125W Tuac module and they performed faultlessly for many years.
I was second DJ, the main DJ now actually lives in Medina, probably closer to Audioguru than me?.
I call awful-sounding piezo tweeters, whistles. A guy fed one with 20kHz and measured 10kHz out. Intermodulation distortion and peaky response like mad!
You can't beat the price of them though! - this is a budget job, and it's PA not HiFi. Have you seen the price of conventional PA tweeters?, they cost a fortune!.
As for 20KHz in and 10KHz out, are you sure it wasn't the amplifier?, at 20KHz a piezo tweeter is going to have a very low impedance, and could well upset the amplifier.