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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. I would rate the woofer as a 6 Ohm unit for testing purposes. It should be any easy load to drive for the Philips OM8383S amp setup.

The Satellites

The satellite impedance is proudly displayed with a 4 Ohm sticker at the rear of the unit. With the 4060's, I whined about that being labeled as a 2 Ohm unit, which tests showed was not even close. Well, MidiLand must have listened to somebody, because those numbers have been doubled. Unfortunately, I'd rate these diminutive boxes more in the 6 Ohm range with the subwoofer.

Satellite Impedance
Frequency (Hz)
Voltage (mV)
Current (mA)
Impedance (Z)
315
109
7.36
14.8
1000
101
15.6
6.47
3150
97.5
13.4
7.28

Of particular note is the soaring curve near the satellites lower cutoff frequency of 265Hz. That may be a good indicator that a higher crossover frequency could be a better match as the 2.5" driver is strained in its last usable octave.

Frequency Response

This setup was obviously designed and tested in a two wall environment. Unlike the BA7500's, which displayed a huge low end boost, the 6.5" woofer was very flat in its 60Hz-175Hz -3dB range. Score another point for MidiLand engineers.

Overall In-Room (2 Walls) Frequency Response
Bass (rel. 100Hz)
Midrange (rel. 1kHz)
Highs
66-89Hz = +2 to +4dB
310-392Hz = +3 to +4dB
10.2kHz = -3dB
60Hz = -3dB
1.2-4.0kHz = +3 to +7dB
10.8kHz = -6dB
56Hz = -6dB
   

The midrange measurements appeared to be some cause for concern as they had two large peaks in critical vocal areas. It should be emphasized that not all objective measurements correlate well to subjective listening tests. The high frequencies were another welcome relief to the mostly missing top octave (10kHz-20kHz) range that plagues the vast majority of two-way systems.

Nearfield Response
Bass (rel. 100Hz)
100Hz = -3dB

For kicks, I also took a measurement of the sub not in its native environment. I placed it several feet into the room and took nearfield readings. Just to show you how much difference there is between a two-wall placement and an effective anechoic chamber, glance at the low end cutoff. By placing the sub at the junction of two walls, the low end grunt extends nearly one full octave, from 100Hz to 60Hz (-3dB).

Rated R.M.S. Power Output

Here's where I must needle MidiLand somewhat. I have no idea why the marketing department rated these speakers as 50 watts RMS. That's sustained power, not peak. Based on my 3% distortion readings, the 3050M's don't even come close and I think I may know why, but let's peek at the numbers first.

At 1kHz, the satellites have an impedance of 6.47 Ohms. Maximum output occurred at 4.50 Volts which leads to 3.13 Watts per satellite channel or a total (not including the sub) of 6.16 Watts RMS. It is possible that with a 4 Ohm dummy load, that the rated 10W/ch could be achieved but that's with an external, essentially "fake" load.

At 100Hz, the subwoofer had an impedance of 6.30 Ohms. Maximum output occurred at 4.18 Volts RMS which leads to a disappointing 2.77 Watts RMS. The subwoofer is capable of handling much more power than this and as hinted above, I believe that the OM8383S may not have been wired in a BTL (bridge tied load) configuration by mistake.

If the two channels of the four channel amp were wired in a BTL configuration, then the maximum sub voltage should raise to at least double (8.36 Volts), which would point to just over 11 Watts RMS at 100Hz.

As tested though, I must rate the 3050M's as being able to crank out slightly over 9 Watts RMS. At maximum output, the main filter capacitor struggled to maintain clean, ripple free voltage because it plummeted nearly 18% (about 3 volts) from its quiescent value.

 





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