Using Short Delays To Create Up-front Ambience

Tips & Tricks

Technique : Effects / Processing

 

CRAIG ANDERTON explains how you can use your multi-effects unit to create contemporary short delay treatments.

The reverb-drenched sound of the '60s and '70s is well behind us, as is the chorused gauziness of the '80s. The sound of the '90s is high-definition and in your face; you hear less and less reverb on records, whether you're listening to the Red Hot Chili Peppers or cutting-edge dance music.

You might think that recording dry, without reverb, is one way to get this effect, but we're so used to instruments having some 'air', both from resonances within the instrument itself, and from the room in which it is played, that dry recording often sounds unnatural and unappealing. Listen to a totally dry drum machine: yes, the sound is clean -- but there's also a certain deadness. The stereo is too wide; drums become individual points of sound instead of being part of a cohesive, unified kit. A synthesizer or sampled keyboard -- in fact, any electric or electronic sound source -- suffers from similar problems when recorded dry. But when you add reverb, the effect is to distance the sound from the listener, thus destroying the up-front effect that's being sought. So how can you reconcile this desire for a current, 'in-your-face' sound with the need to give your instrumental sounds some air and stop them from sounding strange and unnatural?

Some engineers pump electronic sounds through speakers and then mic them up (not at all a bad idea, by the way), but there's a more predictable and compact way to give your electronic sounds some air: use short delays from your multi-effects unit to model a room, and create your own 'virtual room mic.'

 

 

AMBIENCE FOR THE NINETIES

While 'modelling' is a buzzword these days, the concept has been around for a while. Any electronic reverb is essentially modelling what happens when sound waves run around loose in a room.

Recording in a very tight, sparse, hard 'box' of a room is one way to get that 'in-your-face' sound. Back in the early days of digital delay, one technique for simulating this kind of ambience was to put several delays (with delay times of 1-10ms or so) in parallel. Mixing these delays well in the background creates the 'comb filtering' effects associated with typical small rooms. Unfortunately, with today's digital multi-effects, the room, plate, spring, and hall reverb simulations tend to be optimised for traditional long decays with lots of reflections, not short delays -- but there is a workaround.

 

 

HOW TO DO IT

Many multi-effects processors now offer an easy way to experiment with short delay techniques, thanks to multi-voice chorus algorithms (also called multi-tap delay algorithms). The typical multi-voice chorus or tapped delay algorithm looks something like Figure 1.

Most inexpensive multi-effects units combine the stereo input signals into mono. This signal then feeds between three and eight delay lines (Figure 1 shows a four-voice tapped delay). Each delay has controls for initial delay, feedback, level, and pan. There will also be some kind of dry level control. Multi-voice chorus units will also be able to modulate the delay times. Sometimes this controls all the delays, but sometimes each delay has its own modulation.
When patching into a mixer, you would generally drive the multi-effects inputs from an aux (or effects) send buss, just as you would a standard reverb, and feed the outputs into the aux returns. Turn up the send controls for the channels you want to process, and regulate the overall level with the aux buss return level control (remember that a little bit of this effect goes a long way).

 

 

TYPICAL PARAMETER VALUES

Following are two programs for the Alesis Midiverb 4, designed specifically for processing drum machine sounds to make them sound more 'live' without being drowned in effect. (If you don't have a Midiverb 4, the principles also apply to other units.) Typical parameters for a program based on the Four-Voice Chorus algorithm are:

PAGE 1 (MODULATION):
Rate 0.2Hz
Depth 255
Feedback 7%

PAGE 2 (DELAY TIMES):
Pre-delay 1 1ms
Pre-delay 2 2ms
Pre-delay 3 3ms
Pre-delay 4 4ms

PAGE 3: DRY ONLY (--)


NOTES
 
• This creates a tiny, dry room effect.
• The very slow modulation adds a bit of animation that dynamically colors the sound.
• For a more static sound, set the depth to 000.
• To change the room characteristics, try various other pre-delay times between 1ms and 10ms (the combination of 005, 007, 008, and 010ms works well).

The next program uses the Midiverb 4's Tapped Delay algorithm (and again, it can be modified for your own multi-effects processor). Although with the Midiverb 4 this has only three taps, compared to four for the chorus, each tap has more flexibility. Use these values as a point of departure:


PAGE 1

Time 1 005
Level 1 99
Pan 1 -50
Feedback 1 00

PAGE 2

Time 2 007
Level 2 99
Pan 2 50
Feedback 2 00

PAGE 3
Time 3 003
Level 3 99
Pan 3 00
Feedback 3 00

PAGE 4
Master Feedback 50%
LowCut Filter 177 Hz
Hi Cut Filter 15.1 kHz
Mix (--)


NOTES
 
• Master feedback is set to 50%, so if you want to experiment with individual feedback taps, turning them up just a little bit gives an audible effect.
 
• The low-cut filter is handy for keeping the kick drum out of the ambience effect, thus giving a stronger 'thud'.
 
• This program seems to work best with the short delay panned centre, and longer delays panned left and right. Of course, more expensive units with more taps let you create correspondingly more complex ambiences.

 

 

THINGS TO WATCH OUT FOR

If you turn up the aux returns to obtain lots of processed signal, beware of phase cancellations. Although the whole point of this exercise is to add the phase cancellation/addition effects found in the average room, high levels of processed signal can cause excessive cancellation. Check the signal for mono compatibility.

Another consideration is that this technique will tend to 'mono-ise' the signal and make the stereo spread less obvious. Frankly, I consider this a benefit, as it provides an overall sonic ambience for the drums.

Finally, note that these delays can sound good on vocals, but there's still nothing like a nice, warm chamber for wrapping around a voice. I always have at least two reverb devices available -- one to create these short, ambient delays, and the other to provide a more traditional plate sound for vocals. This gives the best of both worlds.

 

 

MULTI-EFFECTS FOR MUSICIANS

Craig Anderton's book Multi-effects For Musicians provides advice on what to look for when buying a multi-effects processor, and features lots of practical tips on using and making the most of these essential studio tools. It's available from SOS Mail Order and costs £10.95 plus postage & packing (£2.50 UK, £5.50 Europe, £8.50 rest of the world).
Multi-effects for Musicians, order code B306; please see the Mail Order pages in this issue for ordering details.

Published in SOS January 1997