Specifications

ABOUT AUDIO ON COMPUTERS
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General Information
Audio Quality
The general audio quality in a computer based synthesizer system depends on
two things:
D The quality of the software calculating the audio.
In our case, this is the Reason DSP (Digital Signal Processing) code.
• Reason uses 32-bit floating point arithmetic for all internal audio operations
which ensures the highest possible resolution throughout the signal chain.
• The program supports 16, 20, and 24 bit audio output.
• The program supports sampling frequencies from 22kHz to 96kHz.
•A number of digital audio techniques are implemented that reduce the risk of
“aliasing”, background noise, unwanted distortion and “zipper noise”.
There is no technical reason why this program should not sound as good as or
better than dedicated, professional hardware.
D The quality of the hardware playing back the sound.
In a PC this is the sound card. In the Mac it is the built in audio circuitry or any
audio card you have installed. Don’t be fooled by the “16 bit, 44.1kHz, CD qual-
ity” tags. How good some audio hardware actually sounds depends on a num-
ber of things, its frequency range and frequency response curve, the signal to
noise ratio, the distortion under various circumstances, etc. Furthermore, some
designs are more prone to disturbance from the other electronics in the com-
puter than others. Such disturbance might add hum or high pitched noise to the
signal.
As you probably understand by now, this is a big subject and there’s no way we
can help you find the right solution in this manual. There are a number of text
books and magazines covering this subject and any music dealer specializing in
computers will happily help you out. The only advice we can give is that if you are
serious about sound, choose your audio hardware carefully!
About Latency
On any personal computer system, there is a delay between the moment you
“ask” the hardware to play a sound and when it actually does it. This delay is re-
ferred to as the “latency” of the design. This imposes a problem for any system
where you want real time user input to affect the sound.
! See the Optimizing chapter for basic information on adjusting Out-
put Latency!
Why is there latency?
Any audio application creates its audio in chunks. These chunks are then
passed on to the audio card where they are temporarily stored before being con-
verted into regular audio signals.
The storage place for these chunks are called “buffers” (an analogy would be a
bucket brigade, where a number of people each have a bucket, and water is
poured from one bucket to another to reach its final destination).
The smaller the buffers and the fewer they are, the more responsive the system
will be (lower latency) However, this will also raise the demands on the com-
puter and its software. If the system can’t cope up with moving the data to and
from the buffers fast enough, there will be problems that manifest themselves as
glitches in audio playback.
To make things worse, audio playback always competes with other activities on
your computer. For example, under Windows, an Output Latency setting that
works perfect under normal circumstances might be far too low when you try to
open files during playback, switch over to another program while Reason is play-
ing or simply play back a very demanding song.
What is acceptable?
Normally, hardware synthesizers provide you with a latency of 3 to 7 ms (milli-
seconds – thousands of a second), at least if the instrument is targeted towards
a “professional” audience.
On a regular PC or Mac, the latency can vary from anything from 2ms to 750ms!
This wide range of values is an effect of the fact that computers and their oper-
ating systems were created for many purposes, not just playing back audio. For
multimedia and games, a latency of a 100ms or more is perfectly acceptable,
but for playing a musical instrument it is not!
• The internal audio under Mac OS 9.x provides an output latency of 11ms.
This is deemed acceptable by most users.
•A regular PC “SoundBlaster” type audio card with an MME driver (see later
in this chapter) might at best give you a latency of around 160ms.
• The same card with a DirectX driver provides at best around 40ms.
•A card specifically designed for low latency, with an ASIO driver, can give
you figures as low as 3 ms under both Mac OS and Windows. This is just as
good as any dedicated hardware synthesizer!
• The best possible situation is achieved using a fairly powerful MacIntosh
computer, running Mac OS X and using a CoreAudio driver. Such a setup
can give as low a latency figure as 1 ms! This is better than most dedicated
hardware synthesizers.