About Piezo XO values

[e-side]

Hello,

I read the Wiki article about piezo xo's. I'm wondering if any value, like the one of the attenuation capacitor, changes when I use two piezo's wired in series instead of a single piezo tweeter.

thanks in advance.

Erwin

[e-side]

Nobody?

[sreten]

Hi,

the parallel resistor doubles in value and the series capacitor halves.

/sreten.

[e-side]

Thanks sreten!

Could somebody also tell me if the value of the in-line resistor will change?

"The Parts Express catalog suggests putting a 20-Ohm resistor inline with any Piezo tweeter to make it a more stable load for an amp.Will this not also attenuate the tweeter? If so, and if I need further attenuation, can I simply add more resistance? Is there a rule of thumb for
how much attenuation I will get with further resistance, or a way to compute this number?

The recommended resistor is to help protect the amplifier from oscillating due to the raw capacitance that is a piezo driver. Adding resistance in series with a piezo will actually roll off the highs a bit, adding more will roll off the highs noticably."

regards

Erwin

[sreten]

Hi,

the wiki has a more refined approach than parts express.

You need to read up on basic electronics,
so you can work these things out for yourself.

a 20R series resistor for a piezo hardly attenuates it,
except at high frequencies. (as the piezo is capacitive).

Increasing the 20R will only lose high frequencies.

As the purpose of the 20R is to protect the amp,
if you use 2 piezo's in series it does not need to change,
the high treble loss will be lower due to the series connection.

/sreten.

[Volenti]

I've had good results from using a non-inductive resistor in paralell with the peizo, and then simply designing any passive network/s to the resistor value.

[baggins]

I am somewhat confused by the statement that adding capacitance in series with piezo's cuts their high frequency response

capacitors in series gives i/ctot =i/c1=1/c2 therefore any additional capacitor will lower the c tot and smaller capacitors resist lower frequencies acting as high pass filters do they not?

[sreten]

Originally posted by baggins
I am somewhat confused by the statement that adding capacitance in series with piezo's cuts their high frequency response

Hi,

No. The series capacitor is used as an overall attenuator.

The capacitor and piezo capacitance act as a voltage divider, just
like two resistors would, except overall impedance is not constant.

Putting a resistor in series with a piezo does not attenuate, it cuts HF.

/sreten.

[baggins]

So a resistor in parallel with a piezo would cut the bottom end of its response?

[sreten]

Originally posted by baggins
So a resistor in parallel with a piezo would cut the bottom end of its response?

Hi,

No. It has no effect on response as its in parallel.
It will set the maximum impedance seen by the amp.

/sreten.