k y m a • t w e a k y — the kyma collective || view the current website || February 2015 Archive

/ WebHome / Sounds / Share.DiscussCompressiveBBEDiscussion


Share Section



All Sections


Login / Register 
Change password
Forgot password?

Symbolic Sound

Kyma Forum
Eighth Nerve

TWiki Links

This Sound file contains the BBE process but with a twist. Standard BBE processing enhances the bass and the highs by the same amount no matter how loud or soft the sound is. But if you look at the shape of the BBE equalization for various depts of low and high contouring (0 - 12 dB), it really resembles the standard "Loudness" adjustment found on hi-fi's.

It is well known that as the music grows softer, our ability to hear the bass and the treble diminishes. That Loudness curve is a bathtub curve that raises the bass and the treble by however hard you push it. Loudness controls also perform their same magic no matter how loud or soft the sound gets.

But when the music gets really loud, we don't need any help hearing the whole spectrum. By rights, then, the Loudness curve should flatten out. That's exactly what happens when you drop the Low and High Contouring controls of the BBE Process to 0 dB.

So by arranging to have the contouring provided by Kyma Compressors, whose ratio depend on the strength of BBE Processs contouring and compressor action threshold, we can have the best of all worlds. Adjustable depth BBE Processing (Loudness contouring), separate for bass and treble, phase shifts to delay the bass region into your speakers (the claim to glory of the BBE process), and depth that naturally diminishes as the music grows louder.

Surely you have heard of BBE? Well the new stuff from them -- the Sonic Maximizer -- is really nothing more than a sum of three signal paths taken from the input signal. The first is a negated (inverted) direct signal cut by 18 dB. The second is the output of a lowpass filter - a simple 2-pole filter with a very low Q of 0.2 and a cutoff frequency (?) of 725 Hz. And the third is a simple 2-pole highpass filter with the same Q and cutoff frequency. Attenuation on these filters with the contour controls ranges from 0 dB (full on processing) to -12 dB (no enhancement).

But the interesting thing is that even without enhancement of the bass or treble region, you still get the supposedly desirable phase shift going into the speaker system to "realign" the bass and the treble.

How do I know all this? Nobody told me, and if you read the old patent disclosures those were written for the old days of analog only components. No, I had to reverse engineer this and use some flashes of inspiration to duplicate the Sonic Maximizer.

What it really is, is something akin to photographic unsharp-masking, a process that enhances the detail in an image by subtracting a low-pass filtered version of itself from some multiple of the original image. BBE Processing does this with both low-pass and high-pass information in the sound. Doing the low-contouring enhances the bass region, and the high contouring enhances the treble.

Some folks swear by BBE Processing. For myself, I found it too much most of the time, because most modern music seems to be loud already. So with this Sound you can have the best of all worlds -- adaptive Loudness contouring.


-- DavidMcClain - 16 Nov 2004

Along the lines discussed in my Compressor Discussion elsewhere, this is a reworked version that uses psychoacoustic compression. The result sounds much smoother and more live.

The compressors are ski-jump shaped, comprised of a blend of the original signal with a hard limiter set to a fixed threshold such that it never produces more than -20 dBFS steady state output signal. Hence it is not likely that this will ever produce clipping output unless you boost the output gain too far.

The nominal output gain setting is 0 dB. This also allows varying compression attack and release, with good settings around 5 ms Attack and 200 ms Release. As before, the Low and Hi Contouring controls run from 0 dB to 12 dB. The higher the setting, the stronger the effect. Zero is actually a disallowed value in the math inside this sound, so I set a lower limit of 0.01 dB, which is close enough.

-- DavidMcClain - 16 Nov 2004

AHEM.... yes, that phasey, flammy, sound you hear with long Attacks is my own fault. All of the signals combined with the output of a compressor with predelay need to be similarly delayed to stay in lockstep... sorry about that!

-- DavidMcClain - 17 Nov 2004

© 2003-2014 by the contributing authors. / You are TWikiGuest