The idea behind Uhbik-A was not to create the most vivid, natural reverb at any expense on CPU, but rather to create the most pleasant sounding one. Its character should not be as in-your-face as recent convolution or ray-tracing reverbs tend to be. On the contrary, reverb really should blend with the dry signal to create a coherent audio “scenery”. To achieve this goal, two concepts that are rarely seen together were combined: early reflections and plate reverb.
Early reflections are very short echos of the dry signal. They appear only milliseconds later and determine our immediate perception of room size and structure. The reverb “tail” has a more chaotic character in which the original sound is less recognizable. It affects our spatial perception.
Uhbik-A has three basic operation modes: small, direct and open. Although these are very different algorithms, they all share a common set of controls.
Of course the choice of reverb depends on the source material and its function within the music. The open setting is probably your best choice for subtle ambience, while direct may be more suitable when used up-front. The small model is predestined for smaller rooms with prominent early reflections and relatively short reverb tails.
Mix and Reverb
The reverb knob crossfades between early reflections and the reverb tail. The mix knob controls the overall amount of reverb. Note that all knobs to the left of the mix knob have to do with input and early reflections, while everything to the right has to do with the reverb tail and its diffusion.
Pre-Delay and HF-Range
The pre-delay knob sets the length of time before the onset of early reflections. Pre-delay can bring the dry signal forward while causing the reverberating space to appear further away, or even result in slapback echo effects.
The hf-range knob controls the high frequency content of the early reflections (and therefore the overall sound). A lowpass filter simulates the absorptive properties of nearby materials (wooden walls, soft carpeting etc.), which tend to absorb higher frequencies more than low ones.
Early Size and Spread
Early reflections are an irregular series of echos. The number, arrangement and levels of these echos depend on the selected algorithm (see Operation above).
The early size knob affects the time-span of these echos, and therefore the perceived size of the immediate surroundings – from about a millisecond (shoebox) to over 60 ms (about 40 meters between enclosing walls). Of course pre-delay adds to these times.
The spread knob adjusts a channel-independent shift (up to 20 ms) between individual echos. This is irregular, for different reflection patterns in different channels. Using a lot of spread can result in rather extreme (but still transparent) spaces. Experiment with these two parameters: Certain settings can neutralize or even create directionality (the Haas effect – google it!)
Decay and Density
The reverb tail is generated by means of a complex network of short delays, some of which pass their signal forward while others pass it back to an “earlier” position in the network. The decay knob controls the level of the feedback channels (and therefore the length of the reverb tail), while the density knob controls the level of the forward channels (and therefore the diffusion).
For long decays, you would usually set quite a high density, and for short decays a relatively low density, otherwise the sound can become overly metallic. This is only a rule of thumb, in the end it really depends on your audio material and the effect you want to achieve.
The relative lengths of delays within the network (as well as the network’s structure) were chosen to produce quite natural-sounding reverb. However, percussive sounds - the true test of quality reverb - can often sound too metallic. Uhbik-A’s modulation parameter brings subtle movement to the delay times, warming up the reverb. Note that too much modulation can lead to unwanted flanging effects.
Bass, Treble and Treble Freq
Absorption also has a significant effect on reverb character. In natural environments, high frequencies are absorbed more strongly than low frequencies. However, you might like to shorten the low frequencies to avoid clashing with other tracks, or set up an especially crisp reverb for vocals. Uhbik-A’s feedback channels include a frequency separation filter with 3 controls:
The treble and bass knobs control their respective decay times, from very short to about twice normal length. The treble freq knob sets the cutoff position of the high shelf...
Unlike many other reverb units, the filters in Uhbik-A are not highpass and lowpass, but wide- range shelves. We believe that this results in more interesting absorption characteristics that are more suitable for plate-type reverbs.