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Sealed enclosures:
In the plot below, I've modeled the RS225-8 driver. The yellow curve is the modeled response of the
driver assuming only 0.1 ohm Rg for the source amp. The Qa was set at 15, indicating a reasonably
heavy stuffing, and the enclosure was adjusted to result in a modeled Qtc of 0.707, or 28.8 liters. Now I
increased Rg to add the cable resistance, the DCR of the inductor, and the voice coil heating effects.
For the purposes of this example, I assumed 0.4 ohm, which is about a 6% increase in Re, rather than
the 8% of the Stereophile article. Taking all the factors in account, this adds another 0.9 ohms to the
series resistance. The result is the cyan curve. Now the modeled Qtc has increased to 0.767, and
resulted in roughly a 0.5 dB loss above 75 Hz. To retain a .707 Qtc under these conditions the box
enclosure would need to be increased to 37.8 liters, or over 30% larger. -But with the extra volume
comes a 5 Hz extension in f3. This is shown in the red curve.
Continued...
Electrical Factors
affecting system
impedance
-And their consequences on system Q