How To Avoid Mic Bleed

Mic bleed is the bane of many-a recording engineer’s existence and can easily throw a spanner in the works for mixing engineers and producers. After all, hearing the hi-hats on a snare take or having guitars inadvertently mixed in with the vocals are issues that require a lot of time to fix. Want to know how to avoid, remove or even use mic bleed to your advantage? Then read on!

The Downsides Of Mic Bleed
Screens & Absorbers
Choosing The Right Microphone
Fix It In The Mix
The Benefits of Mic Bleed
See Also

The Downsides Of Mic Bleed

Generally speaking, mic bleed can cause two kinds of problems. The first has to do with separation. If your snare drum recording includes the hi-hat, it’s going to be impossible to buff it up with an equaliser without brightening up the hi-hat too. The second problem happens when using two microphones that are aimed at different instruments but still capture part of the sound of the instrument they haven’t been set up to record. Take a singing guitarist: the sound of their guitar will reach the instrument microphone before it reaches the vocal microphone and vice versa, resulting in out-of-phase recordings and thin, hollow sound. This is also known as comb-filtering.

Screens & Absorbers

Since separate recording spaces per instrument are usually reserved for high-end recording studios, most of us usually have no choice but to record various instruments in the same room. Luckily, smart instrument placement alone can go a long way towards limiting mic bleed. Guitar amps, for example, are extremely focussed in terms of projection and can be easily set up to face away from any microphones. Meanwhile, drum screens, amp shields and absorber panels can also be used to isolate instruments even more.

Choosing The Right Microphone

A great deal of mic spill can be avoided by using the right microphone and setting it up properly. Every microphone has a specific pickup pattern and some even feature various selectable polar patterns. When deciding which pickup pattern would be optimal, it’s actually important to look at what any given microphone doesn’t register. Cardioid microphones barely capture any sound coming straight from behind, while super-cardioid and hyper-cardioid models register almost no sound coming diagonally from behind. Birectional (also known as figure-8) microphones, like most ribbon microphones, shut out most of the sound coming directly from the sides, making ribbon mikes ideal for well-isolated recordings. In short, accurate microphone positioning is just as important as taking the pickup pattern of your microphone into consideration and using it to your advantage. Learn more about pickup patterns from our article: Polar Patterns Explained.

Fix It In The Mix

Even with smart microphone placement, mic bleed is usually unavoidable. As such, it’s never a bad idea to clean things up before you start mixing. To do this, there are few bits of kit you could use, including filters. A low-pass filter is a great way to get rid of the unwanted treble frequencies of any cymbals in your kick drum sound, while a high-pass filter makes it easy to remove the low-end clutter of a bass guitar from your guitar recording. Then there’s the gate (or expander): a dynamic processor that only lets sound through when the signal is loud enough – a threshold value that can be set so that only the instrument you intend to record can be heard, keeping other sounds and instruments out of the mix. Gates and expanders are particularly effective when it comes to percussive instruments. Audio restoration software is another solid aid. Acclaimed titles like iZotope RX give you the tools you need to eliminate imperfections with surgical precision.

The Benefits of Mic Bleed

Mic bleed doesn’t have to be a bad thing. In fact, a little mic spill is indispensable for a coherent mix, especially in the case of more organic productions such as jazz records and indie rock songs. Even the Wall of Sound technique developed by Phil Spector in the 1960s is partly based on spill. Also, since there’s no more room for a heavy-handed approach once you enter the mixing phase, if you want to use mic bleed to your advantage, it’s crucial to get the sound right during the recording phase. Our tip would be to use microphones that have an equal off-axis response. Small-diaphragm condenser microphones and ribbon microphones are known for sounding extremely natural at any angle, while dynamic microphones will colour any sound that isn’t coming directly from the front. Any phase issues can be avoided by applying the 3:1 rule, so make sure that the distance between your microphones is at least three times the distance between each mike and its source. For more info, check out our article: How to Prevent or Fix Phase Issues in the Studio.