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Old 7th February 2012, 07:45 PM   #1
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Red face Thiele small parameters for tweeter

I've noticed that a few people are interested in measuring tweeters, but I've red an article about this matter and I've realized that is very important in order to obtain a proper crossover network.
In that article says that you have to Use the IMPEDANCE AT THE CROSSOVER FREQUENCY... and for that I need an impedance graph for that tweeter. I have the T/S parameters for woofer! It's done! But not for tweeter...

For woofer I've used a sine signal generator (software), my soundcard and an amplifier in mono output mode, then I've used a resistor 1 kOhm in series on positive output, a 10 Ohm resistor in parallel and a multimeter. Resistors have been used to calibrate the multimeter so on display you can read directly in Ohm (I've used 100 Hz signal, then I modified volume up/down until I've red on multimeter display 10 mV AC; that means 10 Ohm). Than, after the calibration, I've removed the 10 Ohm resistor and replaced with the woofer, and in that way I've determined the Fs (resonance frequency), than F1 and F2... Maybe the method is well known (I hope at least).

I hope you understand what I have written here.

And my question is: what frequency can I use for the tweeter (I can't use a 100 Hz for understandable reason) and how can I calibrate the multimeter to determine impedance graph the same way like above.

Thank you!
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Old 7th February 2012, 08:01 PM   #2
sreten is offline sreten  United Kingdom
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Hi,

whats the problem ? It works exactly the same way over the range of say
300Hz to 30KHz with a 1K series resistor to determine the profile of the
tweeters impedance curve.

Ferrofluid tweeters will show little evidence of the Fs peak, others will.

And FWIW you don't use the spot impedance at the x/o point, you
don't know the phase angle, the ratio of real resistance and imaginary
inductance, though assuming Re will get you very close. But 10 ohms
impedance at say 3KHz is different for a 4 ohm and 8 ohm tweeter.

If you want good phase matching at the x/o point you need to model
it using FRD files and ZMA files in a suitable modelling environment.

See FRD tools stuff below.

rgds, sreten.

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Old 7th February 2012, 08:08 PM   #3
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Quote:
Originally Posted by sreten View Post
Hi,

whats the problem ? It works exactly the same way over the range of say
300Hz to 30KHz with a 1K series resistor to determine the profile of the
tweeters impedance curve.

Ferrofluid tweeters will show little evidence of the Fs peak, others will.

And FWIW you don't use the spot impedance at the x/o point, you
don't know the phase angle, the ratio of real resistance and imaginary
inductance, though assuming Re will get you very close. But 10 ohms
impedance at say 3KHz is different for a 4 ohm and 8 ohm tweeter.

If you want good phase matching at the x/o point you need to model
it using FRD files and ZMA files in a suitable modelling environment.

See FRD tools stuff below.

rgds, sreten.
Thank you so much! I will try after studying the links
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Old 7th February 2012, 08:57 PM   #4
Flaesh is offline Flaesh  Russian Federation
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Location: Eburg
Default my new tweeter..

quick and simplest:
1. install ARTA (or REW5, or ...).
2. measure.
!tweeters are different. choose the lower limit of measurement in accordance with common sense.
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