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To optimally adjust setting of the equalizer using the “HELIX DSP PC-Tool” it is absolutely neces-
sary to be able to measure the frequency responses of the loudspeakers in your vehicle. Even
absolute professionals are unable to make perfect adjustments using their hearing alone.
Thankfully, good measuring equipment is now affordable and is definitely worth the investment.
The following list of necessary components and software have been tested by us and judged to
meet the operational requirements.
•
Behringer ECM8000 measuring microphone
•
T-BONE Micplug USB microphone USB interface with phantom power
•
Praxis measurement software from Liberty Instruments - free to download from www.libinst.
com/praxis_downloads.htm
•
A music CD containing a pink noise test signal
Measuring microphone
The Behringer ECM8000 is a very robust and linear measuring microphone with omnidirectional
characteristics. In comparison to considerably more expensive microphones, it also provides per-
fectly sufficient results for this application. The supplied wind deflector should not be used when
taking measurements. It always requires a preamplifier which supplies the microphone with the
necessary voltage (“phantom power”). There is therefore no need for a direct connection to a PC
sound card.
Suitable preamplifiers
A microphone preamplifier with phantom power is required for the measuring microphone to
function with the PC. This function can be performed by the T-Bone MICPLUG USB, for examp-
le. It is simply attached to the measuring microphone and connected directly to the PC using the
(unfortunately very short) USB cable supplied. There is no need for a specific driver. If the USB
connecting cable is too short, we recommend using an additional XLR microphone cable to con-
nect the microphone and the preamplifier. When using the MICPLUG USB, ensure that the phan
-
tom power has been activated using the small button on the underside. This is easy to spot as the
transparent ring on the preamplifier changes color from blue to red (this requires that it is already
connected to the PC).
Suitable measurement signals
So-called “pink noise” is used as a measurement test signal and must be reproduced by the car
radio. This is the only means of ensuring that the equalization in many factory-installed radios (in
this instance, the sound control which is not accessible to the user) is taken into consideration
during the reading.
If you don’t have the CD with a “pink noise” test signal, you can download it from the Audiotec
Fischer website under “Downloads”, “Tools”.
If you want to burn the track onto a CD, please use the “Rosa Rauschen.cda” file („Rosa Rau
-
schen“ is the German term for pink noise). If your car radio can also play music directly from a
USB stick, select either the uncompressed WAV format “Rosa Rauschen.wav” or the MP3 format
Measuring frequency responses
Measuring equipment
