416-8 onken

[Martyh]

Hi All, I am thinking about an onken or ultra flex type cabinet for my 416-8A. The only formula I can find for this alignment requires the driver total cone assembly mass. Can anyone provide this figure or a way to measure it? Has anyone had experience with this driver in an onken enclosure that they can share? Thanks in advance, Marty

[joyspring]

The simplest method to determine driver moving mass is the Delta Mass (added mass) method described in Dickason's Loudspeaker Design Cookbook.</p>

To do this, you require only a modest equipment list: a sine wave oscillator, frequency counter, an AC millivolt meter, a 1K resistor and some modeling clay (added mass).</p>

With the Delta Mass method procedure, you simply set up a voltage divider between the oscillator and load (your driver) using the 1K resistor as the series resistance and measure the voltage across the load noting the frequency on the counter. Resonance is where the measured voltage will be highest; as an aside, exact impedance calculation is unnecessary for the Delta Mass method as we're simply looking for the location (frequency-wise) of the resonant peak.</p>

You measure the free-air resonance fs and then mass-added (Ma, in grams) resonance fsa. Use clay, approx. 150-250g for your 15" driver.</p>

Calculate cone mass Mmd:</p>

Mmd = Ma / ((fs/fsa)^2)-1)</p>

The Loudspeaker Cookbook provides a table of driver air mass load for various driver sizes; for a 15" driver (i.e. - your 416), the air mass load Mmr is 15.3g.</p>

Total moving mass is the sum of the cone mass and air mass:</p>

Mms = Mmd + Mmr</p>

If you don't have the necessary equipment, ask local hams; they're usually more than willing to help.</p>

BobR</p>