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.
