Tuesday, March 16, 2010

Frequency Response Differences Between SASS & Head-Space Parallel Boundary Mic Arrays

Following the A/B comparison of Andrew Skeoch's and Paul Jacobson's comparison of their SASS/MKH-20 and Head-Spaced Parallel Boundary/Audio Technica AT-3032 mic arrays, I was curious to see if I could get a better sense of the tonal difference between the two rigs. It proved to be possible to approximate the difference fairly well using parametric equalization. This QuickTime movie contains that assessment:

(A) QuickTime movie comparing clips from the two rigs for viewing with a web browser (13mb).  Requires QuickTime Plug-in.

(B) QuickTime movie comparing clips from the two rigs for downloading and viewing with QuickTime, MPPEG Streamclip and other Media players.  (13mb .zip)  

I chose sound clips with distant sound sources because they pose a greater challenge for stereo arrays to render.  Be sure adjust the playback volume of the movie to a comfortable level.

Both arrays use omni mics with comparable self-noise and frquency response, especially in the lower midrange where the response difference is showing here. Here's a sonogram showing the Hz response and self-noise of an AT-3032 mic in comparison to MKH-40 and MKH_80 mics.

"Array C" is the Head-Spaced Paralle Boundary Array with AT-3032 mics and "Array D" is the SASS array modified with MKH-20 mics by Walter Knapp. 

I feel that the SASS array's impact on spatial clarity over the HSPB mic array is positive. Evaluated on my Mackie HR824MKII speakers, there seems to be more acoustic "airyness" without excessive resonance and more audible detail in distant sound sources.  I was able to adjust the EQ of the HSPB array to resemble that of the SASS array using using two parametric curves effective between 400 Hz and 1900 Hz. To match the tonal response of the HSPB array with EQ adjustments to the SASS's recording required two more curves.  It was revealing to hear details in the backgrounds become less audible as I made those adjustments to the SASS's recording.
The HSPB array has a 1" setback or distance from the front edge of the boundaries to the mic capsule.  Rob D.