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Woofer Impedance (Cont.')

Significant factors (especially near the free air resonance frequency) of inductive and capacitive reactance are left out for simplicity. These measurements didn't resolve well with the printing on the sub's magnet, which claimed "4//4 Ohm, 26W//26W." I would rate the woofer as a 7 Ohm unit for testing purposes. It should be any easy load to drive for the dual TDA8510J amp setup.

The Satellites

Like the subwoofer, the satellite specs are not specified by the manufacturer. The satellite cases were screwed and glued together, so I left them intact for fear of cracking a case or two.

Satellite Impedance
Frequency (Hz)
Voltage (mV)
Current (mA)
Impedance (Z)
315
120
25.0
4.80
1000
104
28.6
3.64
3150
109
24.7
4.41

Affecting power measurements, and thusly power ratings, I will assign a nominal 4 Ohm rating for this review. Similar to the easy going nature of the subwoofer, the sat drivers will be an easy load to drive for it's quad amp IC, a TDA8510J.

Frequency Response

The unintentional bass hump is moderately narrow in frequency range, but very pronounced. Remember, a 10dB boost essentially means a relative doubling of loudness for sounds produced in that affected frequency area. The low frequency cutoff in room measured an below average-for-size 54Hz, with a small rolloff beginning at 58Hz.

The midrange response was a disappointment. In two critical ranges, the curve shelved upward in one region and downward in another region. This had a dramatic effect on the perceived sound quality.

In-Room (2 Walls) Frequency Response
Bass (rel. 100Hz)
Midrange (rel. 1kHz)
Highs
64-78Hz = +3 to +8dB
4.7-6.3KHz = +3 to +8dB
14.5KHz = -3dB
58Hz = -3dB
7.5-11.5KHz = -3 to -8dB
17.5KHz = -6dB
54Hz = -6dB
   

The on-axis response clearly shows quite a nasty boost in the 4.7-6.3KHz range, which almost necessitated that the satellites must be listened to 15-30 degrees off-axis. But, if they are angled to that suggested range, the extreme upper midrange and high end roll off dramatically. All listening tests were performed with the satellites angled approximately 15 degrees off-axis to avoid the dreaded audio "headache."

The bass response was the most disappointing. The engineers just couldn't seem to take advantage of the dual port design of the enclosure and create a LF cutoff at least in the sub-50Hz range. This is nearly one full octave short of the 28Hz spec.

Rated R.M.S. Power Output

As I griped earlier, a high distortion power rating is nearly useless when contemplating higher end audio. Possibly a few teenagers, especially those with some hearing to spare might enjoy massively distorted sound, but this reviewer cringes at anything much over the 1% mark (which is plenty detectable). For the purposes of all my audio reviews, I chose the generous 3% rating, which was traditionally utilized for cassette deck/reel-to-reel testing until the early 1990's. At 3%, the waveform when viewed on an oscilloscope starts to visually "flat-top" or clip.

The main voltage rail to the minuscule DC filter cap, a 3300uF 25V unit, measured 16.3 VDC at no load. Direct measurements confirmed a satellite power of 4.64 Watts per channel, so the total across all four channels adds up to just over 18 Watts. The satellite with both amps at 3% distortion, reached 5.47 Watts per channel or a total of almost 11 Watts. I am rating the Xtrusio's as a 29 Watt speaker. This is far lower than the 100 Watt claim, but remember that the distortion figure is more than one-third lower than Logitech's 10%.

 





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