For starters, both have an interesting spectrum analyzer, providing a visual cue to both input and output frequencies. It is also possible to turn on quantization noise, which models the lo-fi converters that gave these boxes some of their charm (even if it makes the reverb sound less realistic). I found keeping the noise on brings the reverb more to the front of the mix. Both plug-ins have a wet/dry knob, with a switch for 100% wet. They also have an A/B switch, which is great for comparing different settings. Both come with a fair number of well-crafted presets, and the units share similar controls across the six faders that do most of the sound shaping. Both units start with a pre-delay fader, with the RC 24 maxing out at 152 milliseconds and the RC 48 at 510.
Because it's modeled after equipment from the very early days of digital reverb, the RC 24 is more limited in range and capability. Following the pre-delay fader, the RC 24 has a depth control for changing the distance from the listening point to the source; placing it further gives you a richer (though less clear) sound. Fader 2 on the RC 48 is labeled "shape," with a corresponding spread knob that affect the envelope of reverb's development over time. The RC 24 has three reverb algorithms—room, small hall and large hall. This is considerably less than the hardware version's eight, but there is still plenty of control and variety available. There are four modulation modes with a fader for intensity that effects the phase and pitch variation of the reverb tails. Their effects are very subtle, though, even when pushed to the max. RC 48 has just two spaces, hall and random hall, to choose from. The latter adds randomness simulating changes in a real environment—moving musicians, for example—to make for a more realistic sound. The random hall setting also has a pre-echoes tab that gives access to a sort of multi-tap delay independent from the reverb. There is no feedback, so as the name indicates, it's more of an echo, and it can give another dimension to the virtual space. Where the RC 24 has simple dark/bright controls for two of its halls, the RC 48 has controls for spin, "wander" and shelf for its random halls. They can add some interesting texture to the echoes' decay. Strangely, though, all three of these sliders are linked.
The right-side controls of both plug-ins are very similar. There are faders for bass and mid-frequency decay times and a crossover to determine where those ranges start and end. These decay times can be extremely long, up to 70 seconds or even infinite on the RC 48. This makes both units very useful for creating ambient tones or special effects. When adjusting these decay times, you can see the shape of the reverb change in the spectrum analyzer. The final fader is a high-cut, with the RC 24 limited to 10900 Hz (another charming nod to its limitations as an emulation of older digital technology). The RC 48 adds a dampening knob which attenuates high frequencies in only the reverb tail and not the pre-echoes.
Reverb is a subtle art, and picking the right one goes a long way in a mix. The RC 24 and RC 48 both deliver quality sound from small spaces to lush halls, and they can even produce some weird effects. Some reverb plug-ins have dozens of parameters where adjustments barely yield a discernable difference. Fortunately, this pair has a decent set of presets to get you started, with rather straightforward controls to shape your space.
Ease of use: 3.5/5