Study Hall

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It’s All About The Bass: Insights Into A Familiar But Sometimes Overlooked Band Of Frequencies

The evolution, facts, and theories about subwoofers and the low end of the frequency spectrum. Also check out the gallery for a tour of new subs introduced over the past couple of years.

Various Approaches

So how do we get the best out of modern sub bass systems? The first thing to consider is that more is not necessarily better – just because we now have prodigious power at our fingertips does not mean that we need to wield all of it. There’s a fine line between levels that induce stomach jiggling excitement and those that induce nausea.

Bass coverage is rarely completely even throughout a venue, so it’s always a good idea to be familiar with the region where it’s at it’s maximum and then to set levels accordingly, also keeping in mind that the levels at front of house don’t always represent the whole.

One of the biggest causes of messy, muddy mixes is bass energy getting into the subwoofer that shouldn’t be there. This can be avoided in a number of ways. First and foremost is microphone choice and positioning – putting the right mic in the right position is the best way to ensure getting just the desired sound from the source. Also be aware of how directional mics exhibit the proximity effect; knowing when to exploit this and when to obviate it can help a lot in delivering a crisp and clean bottom end from multiple miked sources.

I’m also a big fan of the artful use of high-pass filtering, which serves two very important purposes. It can help reduce the amount of low-frequency leakage, which is inevitable when multiple mics are in close proximity to each other, and it can also help reduce frequency masking, which always occurs in a downwards direction, frequency-wise (i.e., guitars are more likely to mask the bass than the other way round). And if that doesn’t help reduce the amount of unwanted bass in the subwoofers, then the aux fed subwoofer method provides further control to ensure only the desired signals are present in the subwoofers.

input channel
A 75 Hz high-pass filter from an input channel of a Mackie 1402 mixer as measured in transfer function mode on Smaart software. The filter has a slope of 18 dB per octave. (Credit: Binksternet)

Sometimes, particularly in small venues, the issue is not too much bass but rather not enough of it. This is where a little knowledge of psychoacoustics can help. There’s an interesting phenomenon called the Missing Fundamental where we hear the overtones of a sound but not the fundamental frequency (usually because the sound system doesn’t go that low). Under the right conditions, our brains process the information present in the overtones and fill the gap left by the fundamental frequency so that we actually perceive it even though it’s not present.

I’ve often exploited this principle when the PA has a less-than-stellar bottom end. The key is not just to boost the upper reaches of the bass sound but also to reduce the low frequency content, which has the added bonus of stopping the PA from wasting energy trying to produce frequencies it can’t.

Hopefully this discussion provides some new insight into a familiar but sometimes overlooked band of frequencies. After all, if you’re planning to build a sturdy mix, it always helps to start with a solid foundation.

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