Trying to get the best out of cheapo piezos

[Freedom666]

in former times I disassembled the piezo tweeters to cover the backside of the cone, too. But this is too much work for me today not being in relation to how easy these drivers could be used from scratch.

 

[Freedom666]

finished party box with aluminized piezo tweeter

piezo tweeter with simple 6 db filtering (18ohms in line, 0,26uF in line, 80 ohms across plus and minus of the driver)

the 5 and 10khz resonance peaks remain. But it sounds good enough so I keep the simple filter.

The aluminized bass offers great sound (sandwich alu paper alu with silicone glue forming constrained layer damping)

 

[Freedom666]

wiring of the tweeter is with inverted phase.

Yes you can hear the high peak at 5khz but it has the effect of "fresh" highs or gives the impression "yes there are present highs".

Its sounding fresh but not annoying.

For sure proper filtering like described omitting the 5khz peak is more hifi-ish.

 

[weltersys]

the aluminium on the piezo paper cone does not change anything concerning its frequency response nor the burst decay. But changes the sound completely for better transients and attack. Never did distortion measurements on this but maybe something can be seen there

The added mass of the aluminum should change both frequency and impulse response.
A "before" and "after" measurement would show what it has changed, for better or worse.

 

[Freedom666]

@weltersys

I have put measurements online.

I did not consider the change in resonances or f response as crucial but there is a change. See posts and following

Post in thread 'Trying to get the best out of cheapo piezos'

2024-04-15 6:53 pm

I am preparing a pair for indirect sound so frequency response is not critical.

Thin metal foil does not change the frequency response but I do that to all drivers I use (see thread "How to make a diy sandwich loudspeaker cone" here in the forum)

Added 100 ohms from plus to minus and tried 0.26uF and 0.039uF in line.

Raw driver no crossover

• Freedom666

 

[Freedom666]

Don Highend made a loudspeaker with a piezo tweeter, ready developed loudspeaker

https://www.donhighend.de/?page_id=7749

 

[PeteMcK]

The foil works best if you make a nice hat out of it:
https://en.wikipedia.org/wiki/Tin_foil_hat

 

[Freedom666]

Making an experiment with a salvaged piezo which was badly glued.

Repaired it, fixed it, let it being in its original position to be "suspended".

Now trying with some thicker alu foil a kind of sphere to see what frequency response would be.

Now waiting for the glue to settle.

 

[Freedom666]

that's the F response from post 88 piezo experiment. Bigger cone brings some (little) extra output at low frequencies.

f response looks more linear than with the horns

the broader f response is 45 degrees off axis, the other is on axis.

 

[Freedom666]

MPT 025 type piezo looks like this, if you compare there is more output below 4khz on this horn than using a big cone.

 

[Freedom666]

here I tried a no name screw on driver in the big horn mentioned. The big horn does not make much more output at 2khz than the MPT025 type. So no justification to use it for only little gain.

 

[Freedom666]

the big horn does more below 1khz. Theoretically it could be EQed but distortion should be observed. Even with dynamic drivers there is rarely anything used below 1 to 2 khz depending on power demand.

Some cut the throat of a big horn like the HL1018 and put a little fullrange behind it with relevant cone travel for making a FAST system