Piezo-only bad for amplifier?

[Johnny Dior]

I've been unfortunate in that 3 different amplifiers have met an early demise in the course of a year. One was due to a faulty ground wire (my fault for not catching it sooner) and other 2, seemingly dropped a channel. One was a Class T PA 2100, other was a Sony ES 5046. Both were running dedicated tweeters on two channels, at VERY low gain, full-range as the tweeters are capped with 10uf 50v caps at the tweeter, and I left Pioneer HU at -6 @ 10khz and +1 at the 3khz range, as that produced the cleanest tweeter output and it helped picked up where the doors left off.


Since it just dawned on me both failures occurred on the same tweeter channel, I'm wondering if the amplifiers might of had an issue with not running traditional speakers? I know piezo won't register an ohm reading, and don't seem to affect other speaker ohm readings i.e. 2-way 8 ohm woofer + piezo tweeter will register as 8 ohm. Only thing possibly odd with them is I series wired them as I wasn't sure if the amplifier would treat them like a 2ohm load or not, which I try and avoid.


I have a handful of silver Crossfire VR402, and a VR302, and both of those have powered the same tweeters w/o issues (although one of the VR402 was being worked to death in tri-mode and was sharing doors @ 2ohm + tweeters until another power cable could be run), as did a cheap, old, 4 channel Crunch amp I modified with better film caps and some audio path electrolytics to try and subdue the disgusting brightness (it was a $15 back-up amp before the Crossfire) it had and horrid separation of highs it exhibited- to some success, and neither of them faltered.


Sorry for long essay post, but rather give enough, than a few words. Have any of you run into amplifiers dropping channels running dedicated piezo-style tweeters? Does it just sound like bad luck on my end?

 

[jcx]

don't know the amps but some linear amplifiers can have problems loaded with too much capacitance - ceramic piezo would be that

most home loudspeakers using them do present a resistive load to the amp because the piezo tweeters usually have to have their level dropped by a R pad network to match the mids

without any R in series ceramic piezo tweeters could be unsafe loads for some types of audio amplifiers

 

[Johnny Dior]

don't know the amps but some linear amplifiers can have problems loaded with too much capacitance - ceramic piezo would be that

most home loudspeakers using them do present a resistive load to the amp because the piezo tweeters usually have to have their level dropped by a R pad network to match the mids

without any R in series ceramic piezo tweeters could be unsafe loads for some types of audio amplifiers

Well, that explains a lot, thank you. Learn something new everyday.

By "R" you are saying resistor? They were advertised as car speakers. Only thing I did was replace their 1uf Chinese caps with some 10uf Elna ones.

I wired in some 4x6 (1" tweeter + 3" mid in 4x6 framing) to help share the load on the VR302 in there now, so the tweeters aren't by themselves. Is that still safe?

Also, given what has been stated, what would you think might have been affected in the amplifiers? Generally speaking?

 

[JMFahey]

the tweeters are capped with 10uf 50v caps at the tweeter

Plain tweeters or Piezo Tweeters?
If Piezo, why a series cap?

Have any of you run into amplifiers dropping channels running dedicated piezo-style tweeters?

If an amp sees a Piezo Tweeter and nothing else, it won't like it.
If said amp is a switching type (Class D/T/whatever) it will often rely on voice coil series inductance to limit current at high frequencies (switching frequencies, audio program is not that important).
If you place a cap there instead, you run counter what was expected and of course make it suffer or worse.

Only thing I did was replace their 1uf Chinese caps with some 10uf Elna ones.

What logic reasoning did you follow to do that?

 

[Johnny Dior]

^ I'm fairly certain they are piezo. They have a standard voice coil that had 4 leads, that went into a PCB with a disc in the middle IIRC. Then, there was a 1uf cap on that PCB. That's how they came.


1uf caps only allow a very high frequency to played. A 10uf lowers the range a bit. In my case, both the 10khz and 3khz adjustments in the head unit can influence them now.


With the Class T amps, they sound absolutely perfect and can rival my multi $$$$ home amp in clarity and vibrancy. Just had no clue they could negatively affect an actual amplifier if run by themselves. Never really used them before as all previous speakers were old style tweeters, though I believe many of my 3-way 6.5" and 6x9 upgrades actually use them as well.

 

[Johnny Dior]

Also, to be clear, I didn't realize they showed no ohm readings when initially messing with them. The packaging they came with stated they were 4 ohm, so went off that premise. They are rated 100wrms and have proven to tolerate that, but I'm not trying to go deaf, so figured "8 ohm" series would be better. I have some home cabs with 3 piezo horn/tweeters and they series those too apparently.

If having 2 10uf caps per set of tweets alters the freq. range to be a little off from a straight 10uf, it's nothing to stress over. As long as it's not only covering the 12khz+ ranges.