Psycho-Acoustic Spectral Compensation

PASC gives you crisp clear dialogue AND deep rich bass at ANY volume. Human ears (more specifically our brains) hear less bass frequencies (as a percentage of the total) at low Sound Pressure Levels (SPL) than at high SPLs. This is why symphony orchestras play at a loudness of around 95 dB. At this sound pressure level (too loud to talk over, but not too loud to shout over) our ears; or our brains rather, hear highs and lows more or less evenly. At levels less than 95 dB or so, our “ears” pick up much more of the middle frequencies than the lows or extreme highs.

Psycho-Acoustic Spectral Compensation (PASC), modifies the incoming audio signal 48000 times a second with “make it sound flat” data. For example; if the playback level is 95 dB or above, PASC does nothing. If the level dips down to say conversational level (around 80 dB) then PASC boosts the bass like crazy, but only for a short period of time. The result is sparkling lively music and more intelligible dialog.

The Problem

Anyone who works with sound knows that matching the mix to the volume it’s going to be played back at can make the difference between great and unlistenable results. Until now, adjusting the mix to meet the demands of differing devices, ranging from bass shy phones to huge DJ systems - at differing sound levels has been an imprecise activity, full of time-consuming trial and error.

Early technologies based on volume control position only confused the mixing and mastering process. Even more recent RMS based loudness compensation techniques don’t take the guesswork out of mixing to work properly with the device creating the sound. For 30 years, engineers have been wandering in the woods trying to come up with something better. We faced the problem head on and broke the code and fixed the loudness compensation problem once and for all.

The Solution

PASC allows you to simulate the sound balance you will hear at any volume level without actually having to play it at that volume level. It sounds simple, even though it takes massive technology development to make it happen. Despite its under-the-hood complexity, it’s a breeze to use.

Instead of adjusting low and very high frequencies based on the position of the volume control or using RMS detectors to set levels, Phasx’s PASC technology uses a powerful software algorithm that takes your input about how loud something will be played in performance - say at 105 dB in a dance club - and plays it back over the Phasx PX300 or PX600 with a 100 dB frequency balance at a more comfortable volume level of say 80 to 85 dB.

PASC adjusts the output 48,000 times a second so you hear what you would hear if it was playing very loud, and it reproduces the entire audible sound range, even to bone-crushing subterranean bass frequencies as low as 25 Hz.


The applications for PASC are many, here are a few:

  • Mix and master to 105 dB at a comfortable 85 dB
  • Optimize dialogue for television and movies
  • Maintain deep rich bass response during low volume playback