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Cheap, innocent searching piezo elements do accept as greetings cards sounders. They assume to could cause affliction if acclimated as acquaintance mics. They assume to affiance a lot but calmly complete asperous as frequently applied. Two solutions are proposed - the bargain and airy FET absorber which apparently meets all the requirements of 80% of users who are application the accessories on alfresco structures, and the top achievement adaptation for those who wish college achievement and lower noise. First of all though, why do these things complete rotten the way they are a lot of frequently used.

The complete to voltage about-face isn't acclaimed for its top superior - a lot of piezo acquaintance mics are acquainted apostle elements acclimated in reverse. The assumption disc on which the aspect is alert is advised to bell at the architecture abundance of 2-4kHz so that a ample audio ouptut is accomplished with a baby ability input. This will tend to advance to a peakiness at mid-frequencies, which is why I cement these to a allurement to try and advance this aiguille and accomplish the coupling to the antecedent better.

However, the capital acumen these accept gotten a bad rap is that abounding humans brace them into a accepted audio load, which loses low frequencies.

A piezo aspect can be anticipation of as a sound-dependent voltage antecedent in alternation with a ample capacitance of about 15nF. Here the agitation starts. You charge to put this into a amount which is college than the impedance of the alternation capacitor at the everyman abundance of interest. If that is 20Hz, back the impedance of the capacitor is 1/2*pi*freq*C again you wish that to be > 320k. I've concluded abundance in 3.9M because that's what I had to hand.

So what to humans do? They go and stick this into the band ascribe of their recorder, archetypal impedance 50k, or the mic ascribe of their minidisc, archetypal impedance about 7k, and they alpha to bear that this abuse affair sounds tinny. Which is does - from the abundance acknowledgment you can see that the mic ascribe starts accident low frequencies beneath 1kHz (red line) and the band starts to go beneath 200Hz (blue line).

We don't absolutely like that actual much. This tends to be circuitous with the botheration that these things aren't absolutely advised as mics and bell at 2-4kHz anyhow unless you stick them down so you get a acrid animal result. What you charge is a top impedance input, which gets you the dejected band in the artifice above

You could try and equalise in column production. The agitation with that access is you charge the specs of the mic and amplifier ascribe to apperceive breadth to alpha your 6dB/octave LF boost, so you will apparently accept to tune that by ear if you don't apperceive these. Plus you will addition all the babble and hum at low frequencies. With the mic ascribe you are searching at puuting in a 25dB addition by the time you get to 50Hz which is just allurement for hum problems, and even the 8dB addition on the band ascribe adaptation is added than acceleration any hum you may have.

These things are actual abundant like the clear mics humans acclimated to use with valve accessible reel recorders. Valves do top impedance absolutely well, and inputs were generally in the breadth of 1 megohm ascribe impedance. The move to transistor chip meant customer audio inputs tended to end up about 50k which is analytic simple to do. Clear mics aswell acclimated the piezoelectric principle, and were admired for their low amount and top achievement voltage which overcame the preamplifier babble better. Transistorising audio accessory dead off the clear mic as they articulate tinny and acrid with the lower ascribe impedances for the aforementioned reason.