Woofer Impedance (Cont.')
Even though
significant factors (especially near the free air resonance frequency) of
inductive and capacitive reactance are left out for simplicity, rest assured
that this driver is not anywhere near the 8 Ohms stamped on its rear. If I
was to assign a meaningful impedance to this port loaded driver, it would
be in the 16 Ohm range. At frequencies beyond its active reproduction range,
informal tests leaned towards a more nominal 8 Ohm rating.
The Satellites
Like the subwoofer, the
satellite specs are not specified by the manufacturer. Labeled as 4 Ohm, I
was able to make a few measurements across the audio range.
Satellite
Impedance
|
Frequency
(Hz)
|
Voltage
(mV)
|
Current
(mA)
|
Impedance
(Z)
|
|
315
|
342
|
56.6
|
6.04
|
|
1000
|
335
|
64.3
|
5.21
|
|
3150
|
314
|
54.8
|
5.73
|
Affecting power measurements,
and thusly power ratings, the satellite impedance is near to 4 Ohms but I'd
have to assign a number closer to 5½ Ohms for the purposes of power
calculations.
Frequency Response
The intentional 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 excellent-for-size 40Hz, with only a small rolloff beginning at 45Hz.
The midrange response
was so spikey (peaky) that meaningful measurements were hard to establish.
Since the midrange must also reproduce the entire range from 170Hz upward,
DA chose to intentionally boost the highs. And boost they did as this 3"
driver had high frequency extension higher than most 1" dedicated tweeters.
Notice the broad hump in the 7-9KHz range and the last hearable octave.
Overall
Frequency Response
|
Bass
(rel. 100Hz)
|
Midrange
(rel. 1kHz)
|
Highs
|
|
61-83Hz
= +4 to +10dB
|
6.7-8.9kHz
= +3 to +6dB
|
11-16kHz
= +3dB
|
|
68-72Hz
= +9-+10dB
|
|
|
|
45Hz
= -3dB
|
|
|
|
40Hz
= -6dB
|
|
|
Rated
R.M.S. Power Output
Since DA
was so adamant about power ratings, I was very excited when I measured 5.21
watts RMS at 1KHz with each satellite at the point of clipping. A great start
so far! Then, I measured the amp's supposed 15 watt output--it did and it
didn't. Glance upwards at the woofer impedance at 100Hz. Since this measures
about 16 Ohms, the power calculation resulted in a meager 8.02 watts. BUT,
the amp can probably do the full 15 watts due to the horrendously sharp and
wide eq curve below 83Hz. It will simply depend on the frequency of bass in
your personal music selection range, so I'm not disputing DA's 15 watt claim
at this time.
