The Resolution loudspeaker is 93dB efficient at 1 metre.

Unlike most manufacturers, I have measured it in a sensible way and I invite you to try it too. Incidentally the other loudspeaker's manufacturer claimed to have a sensitivity/efficiency of 85dB, but that turned out false as you will see

To measure efficiency, instead of relying on manufacturer data, here's what you will need.

Equipment

Oscilloscope

0.1ohm 3W resistor Sound Level Meter with calibration curve data for 20hz-20khz calculator

pad/pen for results/workings

tape measure

tripod for meter

sine wave generator / CD

Procedure

1 connect the resistor in series with the speaker

2 Play sines at 100Hz, 300Hz, 1KhZ, 15Khz

3 using the scope, measure the the millivolts accross the resistor, and the volts into the speaker.

4 convert your (peak-peak) readings into RMS by multiplying by .707

5 divide the the resistor's RMS millivolts by the resistor's value(0.1) to get the RMS current through the speaker.

6 multiply the RMS current by the RMS voltage at the speaker input to get the power.

7 vary the amplifier volume until the power is one watt (succesive attempts)

8 measure the SPL in db(c-weighted) by setting u the level meter on it's tripod one meter from the cones, in line.

9 recording all measurements, repeat for all frequencies.

Results for the Resolution @1m

100 hz, 45mVrms, 2.2Vrms, 72dBc

1Khz,49mVrms, 1.96Vrms, 85dBc

15Khz, 45mVrms,2.1Vrms,93dBc

Results for a JPW small bookshelf 2-way loudspeaker

100Hz, 25mVrms,4.2Vrms, 72dBc

1Khz, 35Vrms,2.94Vrms,80dBc

15Khz, 33Vrms, 3Vrms,81dBc

Conclusion

The resolution's specified sensitivity is apparent at 15khz.

compared to a cheaper speaker the resolution is 5dB better in the mid band, and 11dB in the treble band. Since every 3.3 dB is a doubling of loudness, this represents a massive increase of loudness/efficiency for the important mid/treble bands.

As for the bass, we see here there is little difference in efficiency, and that is because a high-efficiency driver by design has a higher roll off point, but lower bass resonance. this is why small loudspeakers have to be so inefficient - their design Q is lower, enabling a louder bass, but considerably worse efficiency, demanding a more powerful amplifier.

The small speaker is inefficient throughout, but the Resolution has outstanding efficiency improvement over it for most of the audio range.



 

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