by Peter W. Fri Oct 20, 2017 1:02 pm
Pillo69 wrote:Hi.
Does anyone use a zobel at the exit of the ST70?
What would be the correct CR values?
Here a calculator that needs values of the speakers, although there are amplifiers that include it from the factory.
http://diyaudioprojects.com/Technical/Speaker-Zobel/Thank you.
Where:
Re is the DC Resistance of the driver [ohms]
Can be taken with a standard VOM.Le is the Voice coil Inductance of the driver [H]
Needs an LCR meter, or specification from the driver OEM.Rz is the calculated Zobel resistor [ohms] and
Will calculate when the values above are input. Cz is the calculated Zobel capacitor [F].
Will calculate when the values above are input. Now, VC inductance is usually tiny - use one (1) mH and you should be within the ballpark. The typical driver at rest (resistance) is usually, 4, 6, or 8 oms. Try dropping those values into the calculation and see if they make sense. Then, drop an L-pad vs. resistor into the network and you have some additional control. Yes, I keep an LCR meter - I hadn't thought about this use, however. As a side-bar, I am working with another member here to clone the Dynaco A40 crossover to back-fill earlier resistor/cap crossovers in A25-on-up speakers. Using the OEM values I back-calculated to a crossover point of about 1,700 HZ - and that system uses a small air-core choke of about 0.75mH, and an 8.2uF NP cap with an 8-ohm L-pad. I will measure the VC inductance of the tweeter - that will give me the exact crossover point. But, you get the idea - small changes = significant effects. If this effort bears fruit - I will 'show my work' and source the parts for those here. My goal is to make it sufficiently simple that it is the work of a couple of hours if even that.
