Piezo VS voice coil tweeters

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I have built a Worldaudiodesign design KLS3 Mk II gold utilizing above mentioned Audax tweeter HD3P tweeter.
It produces a very sweet and distinct treble quality. Regreatibly it seemes not to be in production any more. Non horn design, kind of dome where the gold layer (on the polymer) is a motor.
Meadowlarks speaker company (among others) had the driver in their top of the line model once.

So: the piezo pricncple has a potential to develop!
Regards
Dimitri
 
near field listening?

I don't think anyone's considered whether horn tweeters are appropriate for near field listening? They would be efficient, which is good if you're driving them from the sound card, but if you're close to a horn tweeter they may not blend with the mid/bass driver that well?
Anyone's experiences with these would be appreciated, I've got a pair of Piezos & a pair of EV horn Tweeters which I haven't thought of a good use for yet.
Pete McK
 
Re: Piezo vs electromechanical tweeters

Konnichiwa,

polsol said:
At first glance, a piezo tweeter would appear to be ideal for the HF section of a speaker system because it does not require a XO.

The statement "Piezos don't need crossovers" is misleading. They do not need them to be protected from low frequencies, the way dome tweeters do, but in the acoustic sense they need the same sort of approach to integrating them with the other drivers as any other Tweeter, except of course electcally they appear as capacitor which has implications o the croosovers practical implementation.

Used correctly Piezo Tweeters, even the Motorola/CTC PA "Lemonsqueezer" can be quite good to very good.

Sayonara
 
Also in the interest of the thread starter, could you suggest how that could be approached, please? ;)

I've got two Motorolas laying around. But I have never heard them sounding good, and I had to stand them quite often.

Of course, piezo tweeters - while 'safe' - are sonically useless without crossover. The usual recommendation would be to connect a resistor in series, this 'lowers' the series impedance of the two and let's the resistor-piezo combo look alsmost resistive for low frequencies. People then usually put the usual crossovers in front of them, calculated for the (almost linear) impedance of the series resistor.

But I have never experienced this to sound goot, neither in so called PA systems, nor with my particular piezos.

Thanks,
Sebastian.
 
I use Motorola rectangular piezos on my forth:D system, on the basement.
They sound like a million dollars, but some years ago I've spent a lot of time testing components and tuning a crossover for them.
:att'n: Without a crossover or with "standard" values for a crossover they sound horrible.

They have a very fast (oh so fast...) and detailed sound, it really reminds a live performance, the real thing.
They have to be crossed over quite high to sing like this, and attenuated to match your mid/woofer.
Only this way they produce gorgeous midband and treble.
I would have to open the speaker to see the component values I used, but in my head, from what I can remember, it's something like this:
 

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Thanks, Carlos.

I didn't investigate this further back then when I was at it (I was only 16 when I bought them, my god, long ago!).

My assumption has alway been that it's wiser to approach piezo tweeters similar to normal ones: Attenuate the piezo's sensitivity with a divider that in turn poses a low impedance load to the amplifier. Then match a high pass with it and experiment from this starting point on, towards a cut-off point and an acoustical filter slope that fits the system. That said, your filter looks really genuine with 560nF and 1:1@33R. :D

I gave up when I realized that it seems impossible to get their distortion down at frequencies in the midrange, like until below 4kHz. I liked their sound at 'ultra high frequencies', but couldn't match them with a low-mid unit in a two-range system.

Sebastian.
 
Cal Weldon said:
But it's still a piezo :D
Cal

Yes, but with this crossover, after many hours of fiddling, I've got a sound from them that is, really, quite good.
It's a different sound from a good dome tweeter, yes.
But it's just different.
Some people may not like, other people like me and others who I've showed these tweeters playin' get quite amazed at the speed and detail they can produce.
I have them on standalone small rectangular wood boxes, I can take them everywhere and connect them to any speakers I want, preferably with double binding posts so that I can easily disconnect the speaker's tweeters.
On this system I use them with cheap fullranges.

sek said:
I gave up when I realized that it seems impossible to get their distortion down at frequencies in the midrange, like until below 4kHz. I liked their sound at 'ultra high frequencies', but couldn't match them with a low-mid unit in a two-range system.

Sebastian.

They work very well with fullranges.;)
 
That means they should look like the cheapest and cr@ppiest pseudo-PA speakers around?
An 8" and a rectangular piezo horn? :D :D :D

Uuuh, "a car boombox", most would probably say in the first place.
A perfect way to hide the really good speaker boxes from the people who don't recognize the difference between a bad woofer and a beautiful fullrange driver... ;)
 
I have played around a lot with these cheap CTS piezo drivers and I even own a pair of the very expensive Phy-Hp ones (wich are in fact a highly tweeked CTS piezo)
After listening to the Phy-Hp I had bought a dozen of those tweeters (the lemon squezers) at a dump store for only $2,50 each and started to play around with them. Right out of the box with no filter they sound quite horrible indeed, fully as expected.

After a lot of experiments I came with the following best sounding solution for frequency above 8kHz (did not use them any lower and used an active crossover).

I gave the paper cone and the piezo element a double coating with Damar varnisch also tried C37 on another pair (yes, dried for 4 months) but the Damar seemed to do a better job with these.
After that I have put some wool damping in a very thight string between the cone and the piezo element.

The paper cone is fitted into the horn buy pressing the outer ring of the cone between two pieces of plastic. The piezo element hangs free. I made this the opposite. I dismatled the complete horn, just leaving the bare naked piezo driver, took a piece of wood and drilled a hole in it the same diameter as the paper cone in the front and one with the same diameter as the piezo element at the back side, both hole are as deep as half the wood thickness. I fitted the driver in their by clamping the piezo electric element in a rubber ring (bought at a hardware store and had luckely exactly the right diameter) and glued thin ring into the whole. I used the half round plastic cap of the back of the horn as a twweter chamber at the back fitted with some wool.

Because I used an active crossover I only put a 22 ohms resitor in series with the tweeter and another 22 ohms in parallel of the whole thing (same as Carlos did with the 33 ohm resistors. )

the whole thing is now build according to the same principle the Phy-Hp is build. I don't know how they fitted the piezo element itself and they use a housing completely out of bronze etc, but all I can tell is that after my owm complete rebuilding (I don't want to use the word modification because not much of the original unit is left) almost all of the typical cheap piezo sound is gone. Yes there is still a little left and I think it can be modded further but I gave up on that, I must admit that the Phy sounds better but they share a lot of the same characteristics

Be carefull with doing such mods, I have killed three out of twelve tweeters with it, any deforming of the paper cone and the efficiency collapses. (and could throw away another four of them after making mods to them that made them sound even much worse)
 
Yo Carlos.....

.. where did you get that circuit from I wonder ;-)

notice you have raised the parallel resistor from 22ohms to 33ohms, but the cap value is very odd...??

do you mean 5.6uF ?? (=5600nF)

do you reckon it smooths things out even better than the 22ohm, 3.9 or 4.7uF combination.

Also you should note that the 33ohm in series with the tweeter will need to be adjusted depending on the sensitivity of the main driver.
 
Re: Yo Carlos.....

Andy Graddon said:
.. where did you get that circuit from I wonder ;-)
notice you have raised the parallel resistor from 22ohms to 33ohms, but the cap value is very odd...??

do you mean 5.6uF ?? (=5600nF)

do you reckon it smooths things out even better than the 22ohm, 3.9 or 4.7uF combination.

Also you should note that the 33ohm in series with the tweeter will need to be adjusted depending on the sensitivity of the main driver.

I found this circuit some time ago, don't remember where... I saved the page on my HDD.
That page had a table for the cap to be used depending of the cut frequency you whant to use.
The table was all in the uF range, and the resistors were 22 ohms.
I used it as a starting point, but everything sounded bad, and I ended up with these values.
No mistake, it's 560nf.
You can use values above to match it with your drivers.
Test this with 560, 680, 820nf.
Don't use much higher values than this, because with these drivers midband will jump on you in a way that's not pretty.:D
I think that these small values work better with this tweeter because it seams to be much more sensitive in the midband than in the treble.
 
Re: Hi Carlos..

Andy Graddon said:
That circuit diagram is from my old web site, as is the scan of the specs etc.. :D

That's why I was so interested in the changes.. I'll have to try then sometime, see what happens.

Best Wishes

Aaaaaahhhhhhhhhhh...:D

Nuuk said:
Yes, I gave up in the end and just stuck mine on top of the cabinet! ;)

Hey!:eek:
My wood-rectangle-shape-black-painted piezo tweeter boxes are just like yours!:cool:

Nuuk said:
(BTW - why do pictures come up so much bigger now?)[/IMG]

Big speakers deserve big pics.:D
 
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