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Woofer Impedance (Cont.')

Even though significant factors (especially near the free air resonance frequency) of inductive and capacitive reactance are left out for simplicity, the 4" subwoofer has quite a high impedance. The best estimate I could muster would be approximately 9 Ohms. Based on that figure, the power output of the amp to the sub will be rather low, but I get ahead of myself.

The Satellites

Like the subwoofer, the satellite specs are not specified by the manufacturer. My best guess would be approximately 6 Ohms which will, of course, affect power calculations.

Satellite Impedance
Frequency (Hz)
Voltage (mV)
Current (mA)
Impedance (Z)
315
220
18.9
11.6
1000
198
34.2
5.79
3150
191
31.6
6.04

Frequency Response

With such a tiny subwoofer, in fact since it's so small, the low end was more or less nonexistent. Considering the nearly $200 USD price tag, this is unacceptable. Otherwise, the woofer itself had a very flat curve. The effective low end cutoff was the highest (meaning worst) ever measured at TargetPC for a subwoofer based system. A very popular low frequency octave these days, from 40-80Hz, is completely missing. And those measurements were taken at the junction of two walls, which gives a theoretical bass boost that centers its maximum output at 100Hz.

Overall Frequency Response
Bass (rel. 100Hz)
Midrange (rel. 1kHz)
Highs
95-150Hz = -3 to +4dB
150Hz-11.7KHz = -3 to +4dB
11KHz = -3dB
95Hz = -3dB
 
16KHz = -6dB
85Hz = -6dB
   

Don't be fooled by the moderately flat midrange. Peaks and valleys were so numerous that voices took on an edgy, distorted quality at all times-a "fuzzy", unclear sound that took some getting used to.

The high end extension was the best ever measured from a full range driver (no tweeter). Having good extension well beyond 10KHz is difficult to muster. The Diamond Audio 3025's had far too much HF boost, while the 5.1's curve gently rolled off in the last hearable octave.

Rated R.M.S. Power Output

Frankly, JazzSpeakers' ridiculous claim of 2500 Watts makes me very angry. Possibly that's why they have no U.S. dealers due to totally false power specs that would never pass under the noses of the F.T.C. This number was pulled out of thin air for many reasons, the first being that the transformer can't supply that much juice.

Rated at 65VA (volt-amps), I would love to hear how this sizable unit could be forced to crank out over 30 times it rated wattage. And as mentioned earlier, since most people's 120V sockets are fused at 15 Amps (some have more of course), is JazzSpeakers implying that the ROCCO's must be plugged into a dedicated 20 Amp 120V line?

As measured, the 3" satellites sucked down 5.30 Watts each at 1KHz. Adding that to an sub estimate of 13 Watts (11 Volts @ 9 Ohms) and not forgetting the 2.5" center channel drivers at approximately 5 Watts each, we can arrive at a reasonable estimate. Adding up to just over 44 Watts RMS before the onset of clipping (3% THD), the ROCCO 5.1's do play very loud. Just not at the 2500 Watt level.

 





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