Ramblings.(Product/service evaluation)

Preview: ETF Acoustic RPlusD room measurement software (www.etfacoustic.com)

The ETF 5 measurement system has been instrumental in many of my TSS reviews on speakers and electronic equalizers. A reasonable starting point to use this inexpensive software package is as your computer's internal sound card and the microphone in a Radio Shack sound level meter. Better results, like the ones I present in TSS, are obtained with an external sound card and calibration microphone.

ETF Acoustics has recently introduced RPlusD, which is designed for analysis of combined room and speaker response characteristics.. The GUI is much improved over ETF 5. For example, the frequency band can be specified on the x-axis between any two arbitrary values and the log graph is spaced on decades of I regardless of the start and end frequencies. Thus, the subbars are incremented by a factor of one until the next decade is reached at which point the sub bars will increment by a factor of 10 higher. Setting amplitude limits on the graph is also easer as is the selection of gate times and smoothing filter for the frequency-domain graphs. Similarly, time-domain displacements are easier to manipulate with the new GUI.

ETF Acoustics has modified the test signal so that both the maximum length sequence noise-like signal and the frequency chirp work in tandem to maximize the signal-to-room-noise value. Display of the signal-to-noise ratio has been much improved so you can check where measurements are valid.

Up to 32 multiple measurements can be displayed together in the frequency or time domain with the RPlusD software, a distinct improvement from the single-profile plot function of ETF 5. With RPlusD you then just press the average button to see the average measurement. Displaying multiple measurements on the same graph and generating averages was a multi-step process in ETF 5.

Consider this application of the new software: the microphone is placed at various locations in the listening area. By examining the individual curves and the averages, you can identify room modes as well as the loudspeaker's response (above about 300Hz). The frequency-domain measurements can serve as a useful guide for to for positioning the speakers for optimal bass response smoothness. If you are using a subwoofer, you can view the response effects of moving the subwoofer and/or the satellite speaker in the crossover region. Likewise, you can examine the impact of changing the crossover frequency should your AV receiver give you the option to change it.

Studying the effect of a low-frequency absorption panel on room response is a recent exercise of mine for which the new software proved helpful. In the ...