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P.M.P.O. (Peak Music Power Output)

What kind of a spec is that? 1000 watts measured how? At 1000% distortion? MidiLand isn’t the only manufacturer guilty of this meaningless number, almost all brands boast that somehow the maximum music output is vastly higher (10 times or more) the R.M.S. (root-mean-square) wattage. Don’t ever be wowed over by the P.M.P.O. spec. It has no relevance to anything. Besides, as loud and efficient as speakers are these days, I wouldn’t want to have my eyeballs blown out by a bass peak of 1000 watts.

Rated R.M.S. Power Output

Without turning one screw to peer inside the sub box, the giant AC adapter gives a clue as to the maximum power output of the 490's. Rated at 14.5 VAC at 2.5 Amps this yields just over 36 watts of input power. MidiLand rates the 490's at 10 watts for each satellite and 30 watts for the subwoofer. Can a 36-watt transformer deliver almost double its rated power? The short answer is no.

Partial disassembly revealed a 6800uF 25 volt capacitor and a mysterious Philips OM8383S 9-pin output semiconductor. Even though Philips denies any knowledge of this unit, output power can still be calculated. At idle (no signal input), the measured voltage across the input power capacitor was 16.5 volts DC. Into a 4-ohm load, this translates to 34 watts rms for the sub and 8.5 watts rms for each satellite. Of course, no load conditions aren’t practical, so I turned the 490’s on and cranked the volume until a slight clipping was heard. At full volume the supply voltage dropped significantly to 13.0 volts DC. The power calculations now are 21 watts and 5.3 watts for the sub and satellites respectively.

What can be concluded regarding the factory rated power? Not really grossly out of spec, the 490’s can pump out about 42 watts rms and 68 watts for short peaks (100mS or less). Interestingly enough, the sub had 30W stamped on it and the satellites had 5W stamped on them.

Miscellaneous Measurements

The crossover frequency, the frequency in which the sub stops producing sound and the midranges start producing sound, was measured at 150Hz, typical for speakers of this genre. Signal to noise measurements were also typical at 62dB "C" weighted relative to 1 watt into a 4-ohm load (2 volts rms).

Maximum volume for the sub was 107dB at 18 inches and each pair of satellites could muster 100db of undistorted sound at my 18 inch standard. The total maximum volume from all 5 pieces was 107db. The maximum output was measured with the satellites at 18 inches from the listener, while the sub was 36 inches from the listener, placed at the intersection of two walls.

Frequency response

As I have mentioned in previous articles, I have routinely listened to some of the best examples available in the professional high-end arena. Some speakers cost in the ten’s of thousands of dollars, and fall short of the magical 20Hz-20KHz +3dB specifications. Actual measurements weren’t unreasonable; the 6-1/2 incher dipped moderately low into boom-land. The –3dB point relative to 100Hz was 63Hz and the –6dB point was 61Hz. This equates to a usable extension of nearly 60Hz, which, although higher than I expected, may be the best at this price point.

Since the satellites are single driver units, the midrange driver must strain to reproduce frequencies in the tweeter range. Most mid’s flop at trying and so do the 490’s drivers. Extreme highs simply won’t be available, but as I discovered in my review of the Altec ACS-45.2’s, this doesn’t equate to unlistenable highs—just muted ones.

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