I just got my piezo horn tweeter drivers in the mail and I ordered twice as many as I needed, in case they blew out, but then I realized they're piezo, and I don't know if I can blow them out.
The site says they're "rated" at 100 watts RMS, but then, this site isn't known for having accurate specs.
Anyone ever blow up a piezo element? Or might it overheat and set the paper cone on fire? (Yes, there is a paper cone attached to the piezo element...)
Need I worry?
Thanks guys!
The site says they're "rated" at 100 watts RMS, but then, this site isn't known for having accurate specs.
Anyone ever blow up a piezo element? Or might it overheat and set the paper cone on fire? (Yes, there is a paper cone attached to the piezo element...)
Need I worry?
Thanks guys!
Heh, I just did some testing with one of the spares.
I was able to run 100 watts through it at 3 khz no problem--didn't even flinch.
However, when I went down to 1 khz, the poor thing "died" after a few seconds at 10 watts. (I had the thing under a mountain of pillows so I could only barely hear it, so I wasn't quite sure when I'd killed it.) I pulled it out, opened it up, and was amazed at how warm the element had gotten.
Then, just to be sure, I hooked it up again. As it turns out, after cooling off for a minute, it works again! (Anyone have any more "scientific" explanations? Please enlighten me!)
well, now I know what I need to know--my midrange is going to be the most easy-to-kill, and my little amplifier does have enough juice to do it, if I handle things wrong.
Thanks guys.
I was able to run 100 watts through it at 3 khz no problem--didn't even flinch.
However, when I went down to 1 khz, the poor thing "died" after a few seconds at 10 watts. (I had the thing under a mountain of pillows so I could only barely hear it, so I wasn't quite sure when I'd killed it.) I pulled it out, opened it up, and was amazed at how warm the element had gotten.
Then, just to be sure, I hooked it up again. As it turns out, after cooling off for a minute, it works again! (Anyone have any more "scientific" explanations? Please enlighten me!)
well, now I know what I need to know--my midrange is going to be the most easy-to-kill, and my little amplifier does have enough juice to do it, if I handle things wrong.
Thanks guys.
Some models of piezo tweeters have in-built overload protection through a light bulb(acting as a variable resistor) and a poly-switch(acting as a resettable fuse). That is why the tweeter worked after the `fuse' cooled down.
In models that do not have the protection feature, you will normally find a 30E 3watt resistor as a shunt load. This gets burnt first. If you replace this with a nominal 30 to 47E 5watt resistor, the unit will work again as good as normal.
Ofcourse, there are times, despite the above elements, the piezo element crumbles.
In models that do not have the protection feature, you will normally find a 30E 3watt resistor as a shunt load. This gets burnt first. If you replace this with a nominal 30 to 47E 5watt resistor, the unit will work again as good as normal.
Ofcourse, there are times, despite the above elements, the piezo element crumbles.
The rating in Watts for piezo tweeters is quite strange anyway. It is the voltage that sets the main limit on these. For the former Motorola piezos there was an average maximum of 20 Volts stated and a short term maximum of 30 Volts stated.
Although they can bear frequencies down to zero (=DC) they (and the user as well !!) benefit greatly if you keep low frequencies away from them.
Regards
Charles
Although they can bear frequencies down to zero (=DC) they (and the user as well !!) benefit greatly if you keep low frequencies away from them.
Regards
Charles
That's the thing that weirded me out.
I measured whilst testing and found that I had sent >35 VAC through it at 3 khz and it didn't even flinch! (I didn't know my amp could handle that much power!) I had the poor thing under a pile of coats so it didn't blow my ears out, but it didn't sound clipped at all.
Drop the frequency to 1khz, and suddenly the driver realizes its mortality! It only took about 10 VAC to make it stop responding, and then the strangest part, how pulling it apart made it start working again....
What a bizarre thing to be dealing with. I know now that there's no way I blow out these tweeters; unfortunately I don't have such a guarantee for the midrange. (I'm using the same drivers for the midrange as for the high-range.) Since it's crossed over at 1.2k, there's still a risk of suddenly losing midrange during a gig.
*sigh* Oh well. C'est la vi.
I measured whilst testing and found that I had sent >35 VAC through it at 3 khz and it didn't even flinch! (I didn't know my amp could handle that much power!) I had the poor thing under a pile of coats so it didn't blow my ears out, but it didn't sound clipped at all.
Drop the frequency to 1khz, and suddenly the driver realizes its mortality! It only took about 10 VAC to make it stop responding, and then the strangest part, how pulling it apart made it start working again....
What a bizarre thing to be dealing with. I know now that there's no way I blow out these tweeters; unfortunately I don't have such a guarantee for the midrange. (I'm using the same drivers for the midrange as for the high-range.) Since it's crossed over at 1.2k, there's still a risk of suddenly losing midrange during a gig.
*sigh* Oh well. C'est la vi.
Samuel Jayaraj said:
By the way I re-checked today; the 30 ohms resistor is not a shunt load but is in series with the minus terminal. In many units, when the internal resistor burned, I have shorted the link and connected a 33 ohm or 47 ohm 5 watt resistor in series with the minus terminal and the unit works perfectly again.
However, don't be under the impression that the piezo element can never be damaged. I have a couple of such lying around.
Reply
I've got piezo's [CTS],50w rms with a 22 ohm,2 w resistor wired on the plus terminal,wired in parrellel to the bass driver[Eminence Beta 15,150w rms,8 ohm].
Driven with a 150w rms into 8 ohm,200w rms into 4 0hm poweramp.
The piezo seems fairly indestructable combined with the 22 ohm,2 w,resistor.
It seems strange it doesn't blow,the amp is giving out 150w rms,and surely a 50w rms piezo would blow.But no it doesn't yet,even when I boost many of the high frequency bands on my 2x 15 band graphic eq,and play and mix the music at loud volumes for a long time.
The only thing i've noticed in this condition,is ear piercing highs and some midrange resonance chirps from the piezo.
Do you think in this condition,the piezo will eventally blow?
If so, i'll just buy a pair of CTS KSN1142 piezo powerline horn drivers,rated 200w rms,protected to 400w[with Tungsten bulb and PTC resistor].
I think the 150w rms bass driver is probably using the high power,instead of appling a full 150w rms to the piezo driver and 22 0hm,2w resistor.
I've got piezo's [CTS],50w rms with a 22 ohm,2 w resistor wired on the plus terminal,wired in parrellel to the bass driver[Eminence Beta 15,150w rms,8 ohm].
Driven with a 150w rms into 8 ohm,200w rms into 4 0hm poweramp.
The piezo seems fairly indestructable combined with the 22 ohm,2 w,resistor.
It seems strange it doesn't blow,the amp is giving out 150w rms,and surely a 50w rms piezo would blow.But no it doesn't yet,even when I boost many of the high frequency bands on my 2x 15 band graphic eq,and play and mix the music at loud volumes for a long time.
The only thing i've noticed in this condition,is ear piercing highs and some midrange resonance chirps from the piezo.
Do you think in this condition,the piezo will eventally blow?
If so, i'll just buy a pair of CTS KSN1142 piezo powerline horn drivers,rated 200w rms,protected to 400w[with Tungsten bulb and PTC resistor].
I think the 150w rms bass driver is probably using the high power,instead of appling a full 150w rms to the piezo driver and 22 0hm,2w resistor.
This piezo doesn't have protection. It cost me all of $2 USD for each driver. 
It's basically just a piezo element glued to a paper cone (Why? Dunno) and then stuck in a poorly-cast ABS plastic unit with threads to fit a horn.
It's just about the bare minimum you can do and still have a working horn tweeter.
It's basically just a piezo element glued to a paper cone (Why? Dunno) and then stuck in a poorly-cast ABS plastic unit with threads to fit a horn.It's just about the bare minimum you can do and still have a working horn tweeter.
To Bull
As already mentioned: If you connect the piezos without any crossover then there is always the full voltage at the piezo crystal. It therefore does not matter that much if it is consisting of bass frequencies or highs or whatever - voltage is voltage. If you don't drive your 200W/4Ohm Amp into constant clipping you end up with approx 30 Volts during signal peaks which is what the piezos may take.
Things would change of course if you have a crossover in front of the piezo.
If you look at the construction of the piezotweeter then you see the piezo disc glued to a paper cone (as mentioned by Nappylady). On the back of the piezo there is a rubber thingie for dampening purposes.
The deformation of the piezo element is almost independant of frequency. That is the reason why they can be used without a crossover. The inertia of the piezo element - together with the compliance of the cone - forms a mechanical highpass filter . The horn contour adds another highpass function.
If you keep the low frequencies away from the tweeter you will end up with less signal voltage across the piezo element and less IMD.
Regards
Charles
As already mentioned: If you connect the piezos without any crossover then there is always the full voltage at the piezo crystal. It therefore does not matter that much if it is consisting of bass frequencies or highs or whatever - voltage is voltage. If you don't drive your 200W/4Ohm Amp into constant clipping you end up with approx 30 Volts during signal peaks which is what the piezos may take.
Things would change of course if you have a crossover in front of the piezo.
If you look at the construction of the piezotweeter then you see the piezo disc glued to a paper cone (as mentioned by Nappylady). On the back of the piezo there is a rubber thingie for dampening purposes.
The deformation of the piezo element is almost independant of frequency. That is the reason why they can be used without a crossover. The inertia of the piezo element - together with the compliance of the cone - forms a mechanical highpass filter . The horn contour adds another highpass function.
If you keep the low frequencies away from the tweeter you will end up with less signal voltage across the piezo element and less IMD.
Regards
Charles
There's something I forgot to mention yesterday:
A piezo tweeter looks like a lossy capacitor to the source driving it.
Don't connect such a tweeter to an ordinary crossover, it may end up in a disaster!
If you want to use an odinary 2nd order crossover connect a sufficiently large resistor of the nominal value, the crossover was designed for, across it's output. Otherwise you don't have a highpass filter but a resonant circuit that some amps don't like that much (The same can happen if you connect a crossover to an amp without drivers).
The fact that one should connect a series resistor to the piezo is well known in the meantime, I assume.
If you want a 1st order crossover then you have to do the same with just a capacitor and a resistor. One could even "misuse" an impedance correction circuit (i.e. the one that compensates the woofer's Lvc) for this purpose.
Regards
Charles
A piezo tweeter looks like a lossy capacitor to the source driving it.
Don't connect such a tweeter to an ordinary crossover, it may end up in a disaster!
If you want to use an odinary 2nd order crossover connect a sufficiently large resistor of the nominal value, the crossover was designed for, across it's output. Otherwise you don't have a highpass filter but a resonant circuit that some amps don't like that much (The same can happen if you connect a crossover to an amp without drivers).
The fact that one should connect a series resistor to the piezo is well known in the meantime, I assume.
If you want a 1st order crossover then you have to do the same with just a capacitor and a resistor. One could even "misuse" an impedance correction circuit (i.e. the one that compensates the woofer's Lvc) for this purpose.
Regards
Charles
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