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i3 DSP Quattro

Real-time Audio Editor [Mac OS]
By Paul Sellars

i3 DSP Quattro audio editor.

This popular shareware sample editor has grown into a serious audio manipulation tool...

Back in 1997, while idly flicking through the June issue of SOS, I came across a brief but very favourable review of a shareware audio editor called D‑Sound Pro in what was then Martin Russ's Apple Notes column. D‑Sound Pro offered comprehensive sample editing functions, a variety of built-in effects, SCSI and MIDI dump support for numerous external samplers — and even a synth oscillator for generating new sounds. All this, as Martin observed, for "a mere 30 US dollars — less than 20 quid!"

So it was that I discovered D‑Sound Pro; a fast, reliable and very functional sample editor which could talk to my Akai S2000, chop and change samples in dozens of useful ways, and which seemingly never crashed. It ran without a glitch on my old Powerbook 5300, and up until a few days ago was still installed on my current Mac, and still getting regular use. The reason I mention this is that DSP Quattro, from Italian newcomers i3, turns out to be a direct descendant of D‑Sound Pro, and is developed by a team of programmers led by original D‑Sound Pro author Stefano Daino.

Although DSP Quattro has inherited a number of features from D‑Sound Pro (including the same comprehensive MIDI and SCSI support for external samplers), so much else has changed that it really deserves to be considered a new program in its own right. While its shareware forbear was a purely RAM-based sample editor, DSP Quattro features a powerful new 'polyphonic' hard disk-based audio engine. This means not only that files of practically unlimited size can be recorded and edited, but also that multiple files can be played back simultaneously, even while another is being recorded. D‑Sound Pro offered a handful of built-in off-line effects, but DSP Quattro's effects are all implemented in real time. Standard VST effect and Instrument plug-ins are also supported, as well as Steinberg's ubiquitous ASIO driver system for low-latency audio cards.

 Test Spec 
  • DSP Quattro versions 1.0 and 1.01.
  • Apple Power Mac G3 400MHz with 448MB RAM, running Mac OS 9.2.2, with Emagic Audiowerk 2 soundcard.

Getting To Know The Interface

DSP Quattro boasts a well-designed user interface, and is very easy to get started with. The Master window contains a stereo pair of faders to control the main output level, and buttons to access a few more commonly used features. Each open audio file appears in its own 'document' window, which features a zoomable waveform display (with overview), a pair of level faders (the left and right channels of stereo files can be tweaked independently), level meters with clipping indicators, and an LCD-style Marker display showing the current playback position and/or the positions of selected markers.

i3 DSP Quattro
  • Easy to use.
  • Powerful sound-processing functions and excellent loop-editing tools.
  • MIDI and SCSI support for many hardware samplers.
  • ASIO and VST support (effects and Instruments).
  • Support for most file formats, including 32-bit 'floating point' files.
  • Bargain price.
  • Some third-party plug-ins cause problems.
  • No support for regions, playlists or CD burning (yet).
A powerful, well-designed and very usable audio editor at an excellent price, DSP Quattro is already impressive, and promises a great deal for the future. Definitely one to watch.


Each document window also has its own set of transport controls, which allow you to play the file at normal speed, backwards or forwards, and to stop, fast-forward, rewind, or jump to the beginning or end of the file. There's also a button to toggle cycled playback on or off, and a virtual ribbon controller which can be used to audibly scrub through the file at variable speeds. Supported file formats include SDII, WAV and AIFF (8, 16, 24 or 32-bit), with the option to create and edit 32-bit floating-point files in AIFF or WAV formats. Files can be imported or exported as RAW data, and it's also possible to import via QuickTime, which is great for 'ripping' CD tracks or decoding MP3s.

Each file you open in DSP Quattro appears in its own document window.Each file you open in DSP Quattro appears in its own document window.Basic editing of files is easy and straightforward. Sections of a waveform are selected by clicking and dragging, and with stereo files you can select either channel separately. Markers can be inserted anywhere in a file by hitting Command-M. All the usual Cut, Copy and Paste (and crossfade Paste) commands are available, as you would expect, along with options to Silence or Repeat a selection, or Mix the contents of the clipboard in. DSP Quattro offers unlimited Undo and Redo, accessible via a floating Edit History palette. Consequently it's always possible to jump back to an earlier point in History and revert things to the way they were before it all started to go wrong. (If only everything in life was as simple...)

A couple of other nice labour-saving features are worth mentioning. First, a selected area of the waveform can be exported as a separate file by simply clicking and holding, then dragging it to the desktop. Secondly, you can choose to transmit part of a file to an external sampler (via SCSI or MIDI) by simply making a selection, then choosing the appropriate destination from the Network Transmit menu — no need to destructively edit at all.

Looping The Loop

DSP Quattro's loop editor is ideal for working with samplers.DSP Quattro's loop editor is ideal for working with samplers.DSP Quattro inherits an updated version of the loop-editing window found in D‑Sound Pro, which I always considered one of that program's most useful features. It offers a clear and easy-to-understand representation of the loop points in a sample, with the left-hand side of the window showing the waveform immediately before the loop end, and the right-hand side showing the waveform immediately after the loop start. Finding a good, click-free sustain loop is often just a matter of looping a likely-looking selection, then nudging the Move buttons a couple of times until a continuous, ideally zero-crossing waveform is displayed in the loop window. For those tricky samples that won't loop cleanly however hard you try, DSP Quattro offers a very effective crossfade function, to 'blur' the samples around the loop points and help disguise any problems.

Like most of DSP Quattro's off-line processing functions, loop crossfading employs a clever real-time previewing system, so that you can hear what effect a particular function will have before destructively applying it. A function called from the Processing menu opens in its own dialogue box, with its own duplicate set of transport controls, along with any other relevant parameters. To hear how the process will affect your file, use the Play button to start previewing, adjust the parameters until you like what you hear, then click Apply to update the file.

You can preview the results of DSP functions such as pitch-shifting and time-stretching in real time.You can preview the results of DSP functions such as pitch-shifting and time-stretching in real time.Previewing in this way is especially helpful when using the Time Stretching and Frequency Shifting functions. Tweaking the parameters in real time makes it quick and easy to find the settings that sound as natural (or as unnatural, if that's the effect you're after) as possible. This is a big improvement on the trial-and-error guesswork involved in using many off-line time-stretching algorithms, and also provides a fun way to come up with unusual effects sounds.

Further processing options are available with DSP Quattro's real-time effects. Clicking the Effx button on either a document window or the Master window opens an Effx window. Each open document has its own independent effects window, while the Master Effx window allows you to make settings that will affect all open documents. An Effx window features four insert slots in series, each with its own level fader and wet/dry mix control. Each insert can load one of DSP Quattro's own built-in modules, or a VST-compatible plug-in.

The built-in modules include a very nice Chorus, a 'Stereoizer', mono and stereo delays, a multi-tap delay with four independent delay lines, two different (and very respectable) reverbs, a four-band parametric EQ, a seven-band graphic EQ with independent controls for each stereo channel, and resonant low-pass, band-pass, high-pass and band-reject filters. These built-in effects, like VST plug-ins, can be used either as true real-time effects, or as off-line processes applied to a selection or the whole file. In the latter case, the effect or plug-in opens in a dialogue box with the same real-time previewing controls mentioned above.


DSP Quattro handles the business of recording new files in quite an ingenious way. The simplest way to make a new recording is to choose New / Input Recording from the File menu. This opens an Input Recorder window, where you can choose a format and location for the new file, select an input device to record from, and start, stop and pause recording via another set of transport controls. More than one Input Recorder can be opened at once, so with ASIO hardware that supports recording from multiple inputs, it's possible to record from several different sources simultaneously and capture each source in a separate file.

An Effx window is available for each document and for DSP Quattro's Master output. This is where real-time effects such as VST plug-ins are applied.An Effx window is available for each document and for DSP Quattro's Master output. This is where real-time effects such as VST plug-ins are applied.

It's also possible to record to a file via DSP Quattro's real-time effects. To do this, simply open a new Audio Input window (which is similar to an Input Recorder, only without the option to record), select the built-in effects and/or plug-ins you want to use in the Master Effx window, then open the Master Output Recorder window. This is similar to an Input Recorder, except that it captures sound from the Master outputs. Once again, if your ASIO hardware offers multiple inputs, it's possible to record from more than one of them simultaneously.

In addition to ASIO or Sound Manager inputs, it's also possible to record the output of one or more open document windows. This presents a number of possibilities. For instance, it would be possible to play a cycled excerpt from a track in one document window, while simultaneously recording multiple takes of (for example) a new guitar part into a separate file. It would equally be possible to record the live input and the document window's output in the same file, via the Master Effx, and gradually overdub layers to create a 'sound on sound' collage. What it isn't possible to do (yet) is synchronise playback of more than one file, so that multiple tracks at the same tempo can be bounced down to create a finished stereo mix. The developers tell me that they have plans to add Master transport controls and playback synchronisation in the next significant DSP Quattro update.

VST Instrument plug-ins are handled in almost the same way as normal Audio Inputs, and their output can be recorded in exactly the same way. Plug-ins can be selected from the File / New menu, and will open in a generic window. The plug-in's custom editor window can be opened if required, although it's possible to choose from an instrument's preset patches from the generic window. MIDI input is via OMS, and multiple instruments can be open, receiving MIDI from multiple sources — for example, your MIDI keyboard and an OMS-compatible MIDI sequencer (via the Inter-Application Communication buss). Even without its recording features, DSP Quattro could serve as a very useful multi-channel VST Instrument host (with real-time effects) for live performance.

 Mac OS X Support 
 At the time of writing DSP Quattro is available for Mac OS versions 8.6 to 9.2.2. However, i3 already have a working beta version for OS X (10.2 or later), and expect to have a finished version ready for release (as a free upgrade for registered users) by the time this article goes to print. They're also working to implement support for Apple's new Audio Unit plug-in format, as well as Carbon VST plug-ins. 

Trial And Error

Although it has inherited some 'mature' features from D‑Sound Pro, DSP Quattro is still a young application, and inevitably faces certain teething troubles. While DSP Quattro itself is fast and impressively stable, any software that supports third-party drivers and plug-ins is, to some extent, at the mercy of other people's code. In the course of testing DSP Quattro, I tried out a whole range of VST effects — freeware and commercial alike — without any problems at all. I also tried a handful of VST Instrument plug-ins, with slightly more mixed results. All but one of the commercial plug-ins I tried worked fine, and most (but not all) of the shareware and freeware instruments I tried were also OK. I only tried two different audio drivers (the default Sound Manager driver, and the driver for my Audiowerk 2 card), but these both worked perfectly.

When I spoke to i3 about the few glitches I did encounter, they candidly admitted that they haven't yet been able to test DSP Quattro with every third-party plug-in and driver available, and a few more incompatibilities might well be uncovered as more people begin using the program. However, in the 10 days or so since I began this review, DSP Quattro has already been updated from version 1.0 to version 1.01, with version 1.02 expected in a couple of days: i3 are clearly working hard to iron out any remaining quirks, and I've been very impressed with how quickly they've solved the problems I did come across.

Weighing Up

When writing a software review, I'm obliged to concentrate on those features that are already implemented, rather than those that are planned. As it stands, I wouldn't hesitate to recommend DSP Quattro as a very powerful and flexible sample editor, ideal for anybody who uses a hardware or software sampler in their work. Its editing and processing functions cover all the required bases, while its well-designed user interface makes everyday editing tasks quick and easy. What's more, its intuitive real-time previewing of DSP functions makes it an excellent tool for more experimental sound-design jobs. Equally, with its hard-disk-based audio engine and VST plug-in support, DSP Quattro could be a useful and cost-effective stereo mastering solution. The only drawback is that it isn't yet possible to create regions or CD track playlists, although i3 apparently plan to add these features in a forthcoming update.

DSP Quattro's ability to record sound from multiple audio documents and input sources simultaneously is impressive, and could have a number of creative uses. The addition of Master sync will significantly enhance the existing functionality, and could effectively turn DSP Quattro into a usable multitrack recording and mixing tool.

DSP Quattro can be ordered on-line from the i3 web site for just 99 Euros (about £65), while registered D‑Sound Pro owners can upgrade for just 59 Euros (about £38). To my mind, this is an absolutely unmissable bargain — and perhaps a real cause for concern among i3's competitors. DSP Quattro is already an impressive and powerful application, which could develop into a real giant-killer. If you're in the market for a Mac audio editor, you owe it to yourself to try it.

99 Euros (approximately £65).

Published April 2003