The amount of ‘color’ imparted to a distorted guitar sound by the speaker cabinet is often understated. Guitar speakers are not high fidelity. Rather they’re designed to roll off high frequencies, typically those over 8khz or so, and usually have poor response to frequencies under 120hz. The high frequency attenuation is particularly important for high gain distorted styles. If absent, listeners will suffer fizz and sizzle.

However cabinets present problems. They’re expensive, heavy, and need to be driven loud to impart the impulse characteristics associated with modern metal and rock. This doesn’t gel with living in a 900 sqft house in a major metropolitan area. Many home recorders and musicians need an alternative.

One alternative is to simply record via the line out on a pre-amp…this sucks big time. You can compensate a bit with high and low cuts on an EQ but it will sound very thin and fizzy. Leaving the power amp in the chain and brining the signal back down to line level through a load box and speaker simulator is better. Many of these units feature adjustable high cut and voicing controls. Additionally, you retain the color of the power amp section. But the results are usually still disappointing. There’s something missing, speaker impulse response.

The sound heard on most rock and metal recordings of guitar is the result of miking a speaker cabinet. Without a cabinet in the chain, it’s virtually impossible to reproduce certain dynamics captured by the microphone. Enter speaker impulse samples. Thanks to Prof. Fourier, it is possible to tease apart the speaker impulse data for all possible tones given any guitar speaker. These impulse ‘deconvolutions’ may then be convolved with any digital audio track to replace the otherwise missing impulse dynamics. Several ‘convolution reverb’ plug-ins are available for the task.

With well captured data from a good cabinet and microphone, the results are amazing compared against the unprocessed track. Many free guitar speaker impulse deconvolutions can be found via Google. At least one free convolution engine exists for Linux platforms, jconv, and can be integrated with Ardour via the Jack protocol. I highly recommend anyone recording guitars direct-to-console check these tools out.