The only piezo tweeters worthy of high fidelity or pro audio use are the Motorola/CTS units, and of those, only the Powerline Series are suited for pro audio. The ones made by other companies are junk. I have seen them selling for as low as 75c each to dealers. If you pay more than $2 for one made by anyone but CTS, you are being ripped off. Sometimes it is said that piezo tweeters are "harsh" or "bright". First, if they aren't a real Motorola/CTS unit, they are junk. But with the Motorola/CTS units I have come to see (and others agree) that they have higher sensitivity than the published 92-93 db/wt SPL ratings. They seem to be 3-5 db higher. I have used the KSN1165a, rated at SPL = 92 db @ 1w @ 1m, with woofers in the 96-97 db range and they seem to have excellent balance. Using the KSN1165a with a 92 db SPL woofer, the tweeter does sound very bright. By reducing the tweeters output by 4 db it matches the woofer very well and makes for an excellent speaker. (more on this later) Ignore everything you have read about resistors and piezos. Most all are quoting each other and MISQUOTING the manufacturer. Some will tell you to place a resistor in series with the piezo tweeter, some say parallel. And both are wrong. Years ago with some of the Motorola line, not all, just some, and I have the paper from them about this, Motorola recommended a 20-50 ohm resistor in series with SOME of the tweeters. This gave protection to the amp from high freq (100khz or so) oscillations as well as some protection to some of their tweeters. They did not recommend using resistors for any of the Powerline series, which include the KSN1142a, KSN1165a, KSN1188a, and a few other in the series. (The Motorola piezo speaker division was purchased by CTS some years ago) The CTS/Motorola Powerlines were the very high quality ones for pro use, and contained built in protection circuits, quite sophisticated. This protection circuit uses a resistor and thermal breaker paralleled with a tiny light bulb. At about 100 watts the thermal breaker heats up, opens and now the power goes through the light bulb. As the bulb heats up it increases resistance. What this does is give "soft clipping", that is, a sort of compression of the highs. This is very mild and almost inaudible, and certainly not noticable. They burn out about 400 watts. These are once again available through Martin Sound. http://www.martinsoundpro.com/item.asp?id=340 Anyway, don't use a resistor with the Powerline Series piezos for power protection purposes; it is simply not needed. If you do put a resistor in series (and even Martin Sound says for Lpad use a 20-30 ohm resistor) I say, go ahead, but it will NOT make a difference in sound. Do you know why? Because a piezo tweeter has an impedance of 1000 ohms or greater. If you put a 20 or 50 ohm resistor in series with a 1000 ohm speaker, well, it is a miniscule change in power to the speaker. Duh! So, how DO you pad down a piezo? The CTS/Motorola paper says you can put a small CAPACITOR in series with the piezo to reduce the level, and that can work. But if you put an 8 ohm resistor across the terminals (follow this whole discussion now...) now it looks like an 8 ohm load. The piezo will not know the difference, it works off voltage only, drawing almost no power. Now, put an L-pad to this 8-ohm load. Make sure you use an 8 ohm L-pad. (or if you use a 16 ohm L-pad, use a 16 ohm resistor) An L-pad is actually two rheostats, one in series with load, one in parallel, and the taper of each is such that the load presented back to the crossover is constant. Now this piezo, plus 8 ohm resistor, plus 8 ohm L-pad looks like 8 ohms to the crossover. What crossover? Well, now that it is 8 ohms, it needs a crossover to keep from putting unnecessary load on the amp below the frequency produced by the piezo tweeter, power that would be wasted in the L-pad and resistor. A simple cap calculated for an 8 ohm load (or 16 ohm load if 16 ohm L-pad and resistor are used) is all that is needed. For example, for the KSN1165a or KSN1142a, which roll in at 1800 hz, if these were to be crossed in at 2000 hz it works out to 9.9 uf, which is a non standard value. But 10 uf is standard and plenty close enough. If you wanted to use all of the 1800 hz-20 khz available from that piezo tweeter use 11 uf (10 uf + 1 uf in parallel). If you wanted to cross this at 3000 hz use 6.6 uf (5.6 uf + 1 uf in parallel). Etc. Just remember, you can't go lower than the piezo tweeter is capable of going, but you can go higher. Calculate the capacitor using an 8 ohm impedance. So now with this setup you can not only control the level, but control the crossover point, too. You may also use a "fixed L-Pad" like this: -3 db R1 = 2 ohms, R2 = 6 ohms -4 db R1 = 3 ohms, R2 = 5 ohms -6 db R1 = 4 ohms, R2 = 4 ohms These are approximate, as in, "close enough for jazz". One caution--Do not try to use a steeper crossover, 12 db/oct, or higher. This is not needed for tweeter protection, and the piezo can react with the inductor in these and produce chirps on occasion.