You need to stack then up in a 'V' of two rows of five each. This will minimize comb-filtering. If they were Motorola/CTS they would require a 68 ohm 5W resistor on the hot lead for each tweeter, and then parallel them up. Real piezos can sound good with a proper crossover. They will do nothing but spit and buzz if not done right.

 

Is that some kind of pun? Just seems all to fitting at the end of a basic question in the advanced forum..

 

They are really easy to make, the cabinet doesn't even need to be sealed as tweeters are sealed units.

 

The only complication which you might want is an angled baffle piezo box so that the sound dispersed is at a wider angle giving more wider dispersion when you use multiple piezos. The angle would have to be exact for it to work well, thats the ONLY complication.

 

Wire the piezos in series so you can pump more power through them at way.Piezos handle the power better when wired in series. Put a 20w 8 ohm resistor on the + side nearest the terminal on the box. The resistor is there because some amps osscilate above 30khz and would damage the piezos.So the resistor stops that.

 

 And use an active crossover from 8-10khz for the piezos.

It sounds really crap if piezos ain't crossed over above 8-10khz. They are only good for the sparkle tssss tsssss sounds but you don't want lower treble/mid frequencies coming out of them as they sound ear piercing and squarky and crappy.

Plus piezos that are crossed over between 8-10khz handle more power than piezos without a crossover, which sound sh*te and handle less power.

 

 

 

 

 

 

 

The 'V' should improve the sound quality as it reduces comb filtering. But it also limits the throw of the tweeters which can be bad if you need them to throw the sound far.

 

I have to say this but the resistor is only there to stop damage from an amp that might osscilate. So you only need one nearest the + terminal on the box. Plus I think using an 8 ohm resistor is a better idea as it makes the piezos like a normal driver of 8 ohms.Instead of some unsteady extremelly high impedance which might make the amp osscilate.

 

Also they should be definatly wired in series to achieve more power being pumped through them. In parallel they will only take what each tweeter handles until it burns out.

 

 

 

I have piezo boxes from Mr Dubz in southend from over 15 years ago, & he's always recommended me to wire them in series - parrallel (Can't remeber what resistor he said to use) but they have never blown, & they sound sweet. (A bank of 8 in a semi circle)

 

They sound so good that a few months ago I went back to him & got him to make me a box with 2 rows of 8, again on a semi circle) Ain't tried them yet though so can't say what they sound like.

 

Tell you what though. it may only be a piezo box, but he used a cnc machine to do them & they look so criss. 

 

   

 

The angle is chosen for what you want it to do, you can design it for what ever you want. The point is to NOT do "2 rows of 8, again on a semi circle", as that gives the comb filtering that (in part) is responsible for the bad rap that the piezo gets.

 

"I have to say this but the resistor is only there to stop damage from an amp that might osscilate"

 

Backwards, the resistor is there to stop the amp from oscillation. Amplifiers don't like capacitive loads.  The resistor also stops the tweeter from drawing excessive power at the higher frequencies the amp produces when driven into clipping. It also flattens out the rising response in the top octave, and damps the mechanical resonance in the bender elements (between 5Khz~11Khz depending on what model it is).

 

The two most common piezo tweeters that would be used for DJ use are the Motorola/CTS KSN 1005 (the one that looks like an orange squeezer) and the KSN 1016 (the 2X5 model). The 1005 is best arrayed as per the cabinet shown above. Done right this will give a solid angle of about 80° in the top octave. You can go narrower than this, but should add a third collum if you want much wider than that. The 1016 is best stacked straight up, its small vertical mouth making this easy and compact to do. Ideally, the vertical array should have a concave curve (dish backwards). A convex curve (like line arrays are hung), causes comb filtering in the vertical plane.

 

These two models act like a 0.13µF load on the amplifier, about 62 ohms at 20Khz. Adding a 62R 5W in series with each one is recommended. You could combine all them for one lower value to save a few pennies, but what happens if one or more driver goes open? You lose the damping and response shaping, as well as the power handleing issue.

 

How much power can a piezo handle?

 

The 0.13µF bender element can handle 35V RMS at lower frequencies, dropping to 14V RMS at high frequencies. At lower frequencies the limit is how much the bender element can bend without cracking, at high frequencies the limit is de-polarizing from heat combined with the high voltage (they are polarized with about 50V when they are made). The individual resistor allows for proper use with a 28V RMS amplifier (200W 4R), although I have used with 40V (400W 4R) amplifiers as long as they don't clip excessively. Ten of the tweeter/resistor combos will be about a 12R5 load at 20Khz, and about 19R at 10Khz.

 

An array of five of the $5 each KSN 1016s will have about 14dB more output at 20Khz than a JBL 2402 bullet.

 

A user list would include:

 

Meyer Sound

Klipsch

Altec

Community

 

Yeah I wasn't thinking when I said wire them in series. I meant to say series/parallel arrangement. So that they handle more power pumped through them that way, whilst still being efficient.And if a few piezos die, the rest can carry on working instead of the whole lot not working.

 

Although I'm not keen on the harsh,thin sound of piezos. If your going to use them, I suggest going for the Powerline series of piezos with the built in PTC resistor and lightbulb as they can handle peaks up to 400w each.

 

As for the way you array piezos that V of two rows does minimise comb flitering but then the tweeters don't throw as far.

 

Personally I wouldn't bother with piezos are they are a nightmare to get to sound acceptable for a large sound system. A few of them Eminence APT80 super bullet tweeters are cheap and sound much nicer than piezos and don't suffer the high frequency problem like with piezos. They must be used with a min 3.5khz crossover to handle 45w rms each, or 5khz crossover to handle 85w rms each.