I have used these in several cabinets and with several horns. But the easiest to use, by far, are the CTS-Motorolas.

The 1188's I have sound very good. Yes, I wish I had a response graph to look at, but my ears tell me they are just fine.

According to what I found on the CTS site, and talking to Mr. Moleski today, wire a 20 ohm 10 wt resistor in series with the 1188's. The 1188's also have the same Powerline protection circuit as the KSN1165, 1142, etc. The various 1800 hz Powerline drivers need no outboard resistors, or other parts of any sort.

Dave

The 1800 hz drivers (KSN1025a, KSN1165a, KSN,1141, KSN1142a)already have a 22 ohm resistor already built in, in series...I think that is the value, it has been a while since I tore into one. They need no outboard parts for protection. CTS advises adding a 20 ohm, 10 wt resistor in series with the larger KSN1188a (800 hz horn driver). The piezos have such a high impedance in their response range, 20 ohms is nothing. There is no noticable drop in output in audible range.

But what happens is that way up high, 30khz and higher, the impedance drops very low... a piezo acts like a capacitor, not a resistor. A 20 ohm resistor in series gives the amp some load. If you have some stray signal, or occillation, with an amp that can respond up to 100 khz, as modern amps can, then you will have a problem.

So, the resistor protects the piezo (and the amp, too) at those very high, inaudible frequencies.

The only reason I ever wire a resistor across the terminals... I have used an 8 ohm 20 wt resistor across the terminals to make it act, to a crossover, as if it were an 8 ohm dynamic driver. Then you can put an appropriate cap in series with it, and cross it over at a higher frequency if desired. Or you can put an L-pad between the cap and the now "8 ohm driver".

Try this experiment... hook some wires to your amp's output and connect them to the terminals of a piezo driver. No other parts. Put on some interstation FM hiss, white noise, whatever. Now, get your 8 ohm resistor, and touch it across the terminals (parallel)... hear a difference?

OK, now wire a 20 ohm resistor in SERIES with the piezo driver, turn on some noise and listen. Use a piece of wire to short around the resistor. Hear a difference? You won't.

I don't usually attenuate the piezos... I just chose a woofer that is in the 95-98db SPL range. Plenty of those available.

You have given quite a lot of useful information on these drivers. The DIY press usually ignores the subject of piezos. I have gotten a great deal of information on what I considered a "hidden art" before these posts. Your posts have taken me a lot further in understanding these interesting drivers.

Piezos are a natural for the DIYer. They are simple, cheap, and rugged, have a wide frequency response and don't require a crossover. What’s not to like?

Please post the values of the inductor for the woofer on the 800Hz driver (when you get you system fine tuned). Let us know when you get any more interesting data.

Dave

I blanked off the midrange hole, took out wire cutters and hacked out the crossover... what a pile of parts! I put in a zobel for the woofer, 10 ohms + 17 uf in series across the terminals, and a .7 mH inductor in series... a simple 6db at 1800 hz or so. I installed KSN1165a's in place of the tweeters, with an 8 ohm resistor across the terminals, to make them look like an 8 ohm driver to my meager crossover. I wired the 1165 and resistor to the L-pad, and from the L-pad back to the hot lead a 12 uf cap. I dialed the L-pad down about -5 to sound right with the woofer.

These speakers never sounded so good.

I will be using the KSN1196a 5x15 horn lens and KSN1188a 800 hz driver with only a 20 ohm resistor in series with the piezo, and 1.5 mH inductor in series with my older Pyle MH1560 woofers (15", 60 oz mag, 97 db SPL...) and exact box design not determined yet. I formerly had the Pyles in a 6.3 cft ported box with a Pyle H3910E horn crossed at 2500 hz 12 db/oct.

I am sure the 800 hz horn assembly will give better dispersion and sound better as it will carry more of the midrange.

PYM1555 292-236 300W 95.8db $59.90
PYM1578 292-238 400W 97.5db $79.90
PYM15128 292-240 600W 96.6db $139.75

Assuming that the 800Hz Piezo can keep up with 97.5 db (1w/1m) efficiency, the PMY1578 looks like the deal (although the aluminum basket, 4" VC w/ Kapton former, 125oz magnet, and 600W power handling capacity of the PMY15128 looks good). Otherwise, the specs on the woofers look identical.

Any idea of how Pyles would work in a base-reflex home installation? I know there are people who swear by them. I think they would perform well using Wayne's alignment (early, shallow roll-off).

What kind of impedance load do you think a system like this would present? Could it be smoothed out enough for vacuum tubes or is this a transistor only system?

Dave

I just ran the 1578 specs thru BoxPlot for my brother, and with a 5 cft ported cabinet, F3=52 hz, two 3" dia x 3.2" long ports. With 8 cft you can get down to about 45 hz.

The 15128, in a 5.14 cft box, F3=44hz, 2 ports 3" dia x 1.61" L. The 96.6 db SPL should match the 1188 well.