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Mac Audio Column

A Philosophy of Tweaking
By Ben Clemson.

Tweak v. & n 2. make fine adjustments to (a mechanism).

Perhaps the most common question I get from my clients when visiting their studios is "How can I get more out of my system?". This question is asked with a look of fear and apprehension, as if the answer I'm going to give inevitably involves the handing over of lots of hard earned cash for a new computer system. Thankfully for their wallets and my karma, the answer is one that doesn't involve wasting money. It instead involves a discussion about how their existing system processes digital audio, and how they can target specific areas of their hardware to increase performance in specific areas. That is the subject of this article.

Back to the Basics

Hardware tweaking for audio requires a different mentality to that applicable to desktop publishers and gamers. The value of a fast Mac to a desktop publisher can be measured in terms of the speed of screen redraws or the time it takes to process a plugin effect. On the other hand, the value of a fast Mac for an audio engineer can be measured in terms of the number of simultaneous audio tracks that can be played, or the number of realtime plugins that can be applied to a given mix. This difference is fundamental when considering how to best tweak your Mac for audio.

Audio Performance: It's Black and White

Applying a Photoshop plugin involves waiting while a status bar runs across the screen. The faster the Mac, the shorter the time spent looking at that cursed blue bar. You're always going to have blue bars to look at, the question is how long you're looking at them. But because audio processing is largely done on the fly, any Mac either will, or won't, play the 32 tracks of audio, the 7 native reverbs or the 4 virtual synthesizers. Hardware tweaking for DTP is only ever shades of grey, but hardware tweaking for audio is black and white.

To put it another way, a brand spanking new Dual 800 G4 Quicksilver PowerMac is going to play 16 tracks of 48kHz/16Bit audio just as well as a 4 year old PowerMac 7300/200. The only difference is about $3300. Both machines will probably play 24 tracks, but get up to the 32 or 48 track range, or rerecord those 24 tracks in 24Bit, and the 7300/200 won't play anything: system overload. Do you need 48 tracks? Do you need to record in 24Bit? If the answer is "No", do you need the new Mac?

Dissecting Performance

Of course this comparison is loaded and simplistic. The 7300/200 although playing the 24 tracks of 48kHz/16 bit audio will struggle to process even a quarter of the native plugins that the G4 could deal with, let alone virtual synths and samplers. But when you're looking at tweaking your Mac, ask yourself "What do I want to improve?". Is it the number of programs you can open at once, the number of open programs actively processing audio, the number of audio tracks you can play at once, or the number of plugins youcan assign a mix? Below is a table of these aspects of digital audio processing together with its dominant hardware variable.

Number of programs open RAM
Number of open programs that can actively process audio CPU,
Cache (L2, Backside etc)
Number of audio tracks Hard Drive*
Number of active native plugins CPU,
Cache (L2, Backside etc)
* The speed of your SCSI or IDE bus is also critical.
Most sequencers allow you to use RAM as a buffer
to (marginally) increase the number of playable tracks.

If you're happy with the number of tracks you can play but want to run more plugins, look at upgrading your CPU. If you want to run more tracks but, like me, you run a Powerbook and a faster internal HD is just too expensive, look at getting more RAM and then increase the RAM buffer your sequencer assigns to each track. Read the manuals that came with your audio software and look at how the software uses your Mac to do what it does.

And Finally...

Aside from upgrading aspects of your Mac's hardware, there are many things you can do to your existing system to increase its efficiency. That is the subject of next fortnight's article. In the meantime, just remember that audio processing is black and white, and that a newer, faster Mac is going to do what you do now exactly the same way as you do it now, its just going to be able to do more of it. The question is, where do you need more?

© 2001 Ben Clemson


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