Steinberg Freefilter; Spectralab

Steinberg's new FreeFilter 'learns' the frequency response of one piece of music then applies this to another. In the main graphic window is the input frequency plot, the red one is the resultant output, while the upper, yellow trace shows the current 'learned' filter response that is being applied. See main text for more details.

Unexpected crashes happen to all of us — even SOS PC gurus! Martin Walker tells a tale of troubleshooting, and falls for Steinberg's new Freefilter.

Something strange happened to my PC recently. One morning, out of the blue, it hung during the boot‑up procedure, after the Windows 95 screen had appeared. It had been working fine the previous evening, so it was hard to think what was causing the problem. I have no AUTOEXEC.BAT or CONFIG.SYS files (which is where any DOS‑based drivers will be loaded), which narrowed down the problem areas considerably. Fortunately I could still get into Safe Mode, which confirmed that the problem was driver‑related. (Because Safe Mode uses only a very basic set of drivers, if your PC will start up in this mode you know that the problem is one of the extra drivers that is loaded in a normal boot‑up. The trick is finding out which one...)

Bearing in mind my previous trouble‑shooting experience, I went into Control Panel, Device Manager, System, and clicked on Properties for my Adaptec SCSI card. At the bottom of the general page is a box labelled Device Usage. I un‑ticked the Original Configuration (current) box so that the card driver would not be used the next time I booted. Sure enough, my machine safely reached the desktop on its next try. The problem still re‑occurs on cold mornings, so I suspect that the dreaded borderline SCSI chain may once again be at fault — but after the machine has been switched on for a while I can just tick the same box again and the driver is activated immediately. I can live with that.

Un‑ticking the Original Configuration box is a useful way to leave drivers in your system without actually using them. This is ideal for me when reviewing soundcards, because I need to temporarily remove my own card but don't want the hassle of re‑installing its drivers when I've finished with the test hardware. It's also good for disabling things like unused joystick drivers in such a way that they don't load into memory, but are still known to the system so that you don't get a 'New Hardware Found' message next time you boot up.

Freefilter

Using SpectraLab, I can finally measure the A‑weighted background noise figure for my Event Gina soundcard — and here it is, at +/‑95dB (the yellow trace), along with the higher one for my AWE64 Gold (the red trace, which measures ‑83dB). Notice the mains breakthrough at 50Hz with both cards, and the few spurious lines at higher frequencies. Time to go in search of earth loops.

Now that there are DirectX plug‑ins available from so many manufacturers, it's good to find one that stands out from the crowd. One such is Steinberg's Freefilter, written by Spectral Design (whose excellent Magneto, Loudness Maximiser, Denoiser and Declicker are already well known to plug‑in users). There has been quite a lot of interest in Freefilter, since it claims to 'learn' the sound of one piece of music, and apply to another.

In essence it is a linear‑phase 30‑band third‑octave equaliser, with a built‑in spectrum analyser. All the controls of a standard 30‑band graphic equaliser are provided in the bottom portion of the display (see screenshot), along with three special tools for global control in the small box beneath. The Rubberband tool can be used to select any portion of the frequency graph above; the faders that control this portion of the graph will then be grouped together and operate as one. The Filter Level tool acts on all faders at once, setting them in a steady slope whose angle and central point you can determine; the Bone tool performs a similar function over any selected portion of the frequency response. Of course, the faders can also be clicked and dragged individually; you have +/‑15dB of control for each of the bands.

The really exciting stuff, however, is found above the graphic frequency response window. To analyse some music, just start playback and click on the Source button (the Learn button illuminates as well). Between this moment and the time that you stop the Learn process by unclicking the Learn button, the program builds up an averaged frequency fingerprint of the chosen material — you may want to play an entire track, or just a short section, depending on what you're trying to achieve. Once the source has been analysed, you select the piece of music that you want to match to this original, start playing it, and press the Dest (destination) button. The Learn button again illuminates, and analysis of the new material continues until you hit the Learn button again. Now comes the interesting bit: clicking the Match button generates the exact filter response needed to modify the frequency characteristics of the destination to match those of the source. The Morph slider, which determines how much filtering is applied, defaults to 100%, but you can change this to anything from 0% (no change) through to 200% (highly exaggerated). At this point, the graphic controls still remain flat, so that you can use the individual sliders, and the global tools, to further modify the sound. You can hear all of your changes in real time.

After trying Freefilter with a wide variety of source and destination material, I felt it was ideal not only for learning more about other people's mixes (by attempting to match your own material to platinum‑selling chart‑toppers), but also for mastering albums, since you can tweak one track to match another more closely in timbre. Whether you want to sound more like your favourite band, or correct anomalies where different studios were used to record different tracks, Freefilter can help. You could also use it on individual tracks, to match the sound of a new take to that of an older one. Filter presets are provided (from '1965' to 'Techno'), which you can use instead of a Source track; you can also save your own Source analyses for later use.

If I were to suggest improvements, a lower resolution filter response (ie. smaller FFT size) for the learn process would be among them, so that the many sharp peaks and troughs in the frequency plot of a real track could be replaced by more gentle curves — as it is, the graphic sliders do not offer sufficiently fine frequency resolution to match the more complex shape. It might also be useful to apply Freefilter to a shorter section of a track, with the option of fading its processing in and out.

I found that Freefilter works best inside Wavelab (using 70% of a Pentium 166 MMX processor), since this allows you to move between any number of WAV files while the plug‑in window remains open. Cubase loads the presets, but without names, while Sound Forge and Cool Edit Pro won't currently work at all.

Of course, there's more to good mixing than frequency response, and Freefilter doesn't take account of dynamics or frequency masking, but it should still prove invaluable for anyone working with lots of different material. It is a clever and useful plug‑in for both PC and Mac platforms. At £299 it won't sell by the bucketload, but could certainly become an indispensable tool in many studios. Contact Arbiter Pro Audio (0181 207 5050) for further details.