Since 2006, our TM400 “Test and Measurement” wireless system for sound system alignment has been a standard tool in the live sound reinforcement industry. Used by loudspeaker setup and alignment techs, touring rental companies, and consultants doing sound system installation and commissioning, the TM400 system saves time, is compact enough to travel easily, and is easy to use. One reason for this is that the Digital Hybrid Wireless® transmission platform offers relatively flat frequency response, and does not have the dynamic processing common to most analog wireless mic systems.
Another important consideration is audio frequency response. Accurate frequency response information from input to the output, via the RF link, and can make the difference between accurate and not-so accurate measurements.
How Do We Measure Frequency Response In Our Test Environment?
The original TM400 system with the R400A was designed to provide a reliable wireless link between calibrated test microphones and measurement equipment. You can use a variety of analysis equipment to create visual Bode plots; we use SmaartLive.
Improved Frequency Response and Phase
With the recent introduction of our D Squared digital wireless platform, and more recently the DPR digital plug-on transmitter, we now have a new platform for the RF link between the test microphone and your favorite measurement equipment.
Here is a comparison of the original TM400 system with our new DPR with the DSQD. For test purposes, we set the transmitter high-pass filters to the lowest frequency available. For the HMa, that is -3dB at 35Hz and for the DPR, that is -3dB at 25Hz. We ran frequency and phase plots using SmaartLive V8, and a Sound Devices USBPre2 as the A/D interface.
What We See
The DPR/DSQD clearly passes signals at much lower frequencies and shows a more gentle rolloff below 25 Hz, when compared to the older system. The newer system also displays a much better phase response, due to the simpler, single-pole high-pass filter. This may help with certain types of measurements. Both the older system and the new one display very flat frequency response above 60 Hz all the way up to nearly 20 kHz, while many wireless systems have a more restricted audio frequency band.
Is this to say that the original TM400 isn’t as good? Not at all – it is still a standard and has provided nearly 15 years of good service to technicians and sound system operators. However, for those users looking for the ultimate in RF performance when applied as an RF link between calibrated microphones and their analysis equipment, the DPR and DSQD offer this platform.