& Miscellaneous Measurements
Using a 100Hz tone and
various music selections, the maximum output of the sub placed at the intersection
of two walls measured 107dB SPL at 0.5m. The four satellites pumped out 108dB
SPL at 1KHz under the similar conditions before clipping (3% THD). The total
usable output from the entire system is 110dB.
Input sensitivity, the
amount of output from your soundcard needed to drive the 7500's to full boom
levels wasn't rated at all and is another downside. Using an SBLive!, which
cranks out a whopping 475mV to four channels, I was not able to distort the
satellites. That's achieved with all the sliders at 100%! These speakers require
an estimated 750mV-1000mV to drive them to maximum levels which no sound card
I personally know of can muster.
Signal to noise, or the
amount of hiss heard was the lowest (meaning worst) ever measured at TargetPC.
Weighing in at 60.7dBC relative to full output. Hiss will probably not be
heard though, as the satellites don't reproduce highs much beyond 10KHz anyway.
Input impedance measurements
couldn't be directly taken due to the presence of the dreaded DC blocking
capacitor. Again, BA chose the economy route when designing the 7500's by
not using split voltage rails that don't require input blocking. Suffice it
to say, informal measurements revealed no appreciable loading of the SBLive!
While not entirely sound
related, I did notice the rather poor satellite shielding. If the satellites
are placed closer than 3-4 inches from a large monitor or if the volume is
loud, the psychedelic color shift makes quite an appearance.
The woofer port center
frequency measurement is a N/A because the entire woofer output emanates from
the port normally.
Lastly, the crossover
frequency, the frequency at which the sub stops producing sound and the satellites
start measured 160Hz in the 2-wall environment and 150Hz in the nearfield
environment. The satellite crossover frequency was a bit complicated. Technically
measuring -3dB at 280Hz, it's curve extended smoothly much lower and will
mesh fairly well with the sub's frequency when the entire system is place
away from any walls.