Aphex Systems Explore the Features of the Aphex Dominator II and Why It's the Best Multiband Limiter

Aphex Dominator II

Precision MultiBand Peak Limiter

Models 720, 722

Why is the Dominator So Special?

A very significant problem with wideband processing is “spectral gain intermodulation” which occurs when one part of the spectrum controls the level of another part. A typical situation is a vocalist being “sucked down” every time the kick drum hits.

Since most energy is contained in the lower frequencies, they tend to control the level of the entire spectrum. When the lower frequencies are above the limit threshold the higher frequencies are attenuated thus causing the output to sound dull.

Multiband processing solves these problems by splitting the audio into two or more frequency bands and processing each band separately. However, more bands often result in many more parameters to control including a method of summing the bands together again. While giving the user flexibility, it also requires different settings for almost every different source.

The Dominator ll uses program dependent, intelligent circuits to reduce the number of controls. The user, therefore, has flexibility to shape the sound while quickly and easily achieving the goal of consistent, effective limiting.

The Secret Ingredient: ALT

A multiband processor splits the audio into separate bands, limits each band individually and then sums the bands together again. Even though each band’s peak output is predictable, summing the bands together produces an unpredictable peak output.

One conventional approach to making the summed output predictable is to use a wideband limiter after the summing. This, however, introduces all the drawbacks of wideband limiting discussed above.

Another approach is to use a clipper on the summed output. This causes too much clipping distortion if the summed output is too high. In order to avoid this distortion the limiters’ thresholds are set very far below the clipper threshold. The drawback is a loss of loudness and, due to the lower thresholds, much greater amount of processing.

The Dominator ll uses a patented method to produce a predictable peak output while maintaining maximum loudness without audible distortion- the Automatic Limit Threshold (ALT). The outputs of the three bands are summed and sent to the ALT detector circuit. If the sum exceeds a reference value, the ALT reduces the thresholds of the individual limiters. When the summed output falls below the reference value the limit thresholds return to their original setting.

The ALT circuit has a self-adjusting finite attack time. The amount of time it takes to lower the thresholds of the limiters is the length of time the limiters’ overshoot may be in the clipper. The reference value of the ALT in relation to the clipper determines the depth of clipping.

Both parameters are set by the Density control. When the Density control is set higher, the ALT reference gets closer to clipping, and the attack time is slower, producing more clipping. The opposite occurs when Density is set lower. The “0 RCH” position for the Density control emulates the standard parameters of the original Studio Dominator Model 700, and is recommended for general use.

PROCESS OFF/ON -	LF EQ - adjust input
	level to the low
switches the audio	frequency band ±5dB.
through the unit or	Center detent is flat
through bypass relays.	response below limiting.

Model 720

	STERE
RELEASE - adjusts	forces
	band to
release time of the	limiting
limiters between	the oth
150mSec (fully	band in
clockwise) and 7Sec	has a g
(fully counter-clockwise).	limiting

INPUT GAIN - adjusts input level ±15dB. Center detent is unity

XOVER 1 - switches the crossover point between low and mid

HF EQ - adjusts input	XOVER
level to the high	crosso
frequency band ±5dB.	mid an