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If you’ve ever built a home studio, you’ll have read much advice on the ‘net about Bass Traps….

When I built my first studio, way back when reverbs had springs in and autotune involved someone else, your guitar and a tuning fork, I got my first advice about bass traps.

Control Freak.

The back of the room with the speakers in – we called it the Control  Room, although the last thing you could describe its acoustic as was controlled – suddenly turned the track you were listening to into a dub reggae version if you put your head against the back wall.  In fact, if dub reggae was what you were aiming for, you listened to the back wall version, then tried to replicate it in the middle of the room.

An old lag in the industry who ventured into my domain told me: “what you need is a bass trap mate”.

Thus inspired, I ventured to find this holy grail, this ‘bass trap’ that would make my room sound perfect, and remove the ghost of Bob Marley from my back wall…

Set me free.

Legions of engineers since have been confronted by the same paradox – something that traps bass yet simultaneously makes it true and free.  Much has been written about this magical treatment and much has been bollocks.  My favourite being the wonderful flash animation on an alleged ‘professional studio builders’ page a few years ago that illustrated a bass trap as the ‘thing you put over the windows to stop the bass getting out’.

The truth is, sadly, much more mundane.  It turns out that in a conventional room, the sort that we all live our lives in, most of the bass ends up heading out via the doors, windows and ceiling, leaving precious little to bounce back and cause us trouble when we are listening to music.

Not none, of course.  Any room with parallel walls will conspire to boost some frequencies, and wipe out others, with the unfortunate characteristic of doing this sneakily and almost indiscriminately depending on where you are in the room.

However, when isolation is required and you try to trap sound in a room (or keep it out), the effect is magnified by a at least an order of magnitude, and the peaks and troughs can become so excessive as to render your perception of what is coming out of the speakers more or less meaningless…

Show me the way?

So, what to do?  Well in recent years, since the advent of the ‘net, a host of advice has found its way onto google.  Sadly, much of it is touted as generic – ie proposed as something that will work for everyone – when the reality is that every room is different, and every room will require trapping tuned to that room’s particular anomalies.

Lets face it – where was anyone going believing that all these problems had a universal solution?   Did anyone really think that someone’s total lack of bass and another persons huge boom at 100hz were going to be resolved by application of the same bass treatments?

Heal me!

Funnily enough – it turns out that the problems, and the solutions, can be more than just varied.  The problems can stem from many sources.

Likely causes:

Parallel walls- these cause peaks, and troughs (depending on where you are in the room) that distort at specific finely defined frequencies.

Weak walls – these will leak bass, causing poor bass response, either at specific frequencies, or wideband across the spectrum.

Strong walls – these will reflect the bass as part of keeping the sound in or out, causing peaks and nodes that vary depending on the offset of the barriers.

Weak doors allowing the influence of:

External spaces such as corridors – where the tube-like construction sets them up like tuned ‘organ pipes’ hanging off the room, and creating complex harmonic sequences of boost and cut that initially completely confuse the situation.

Then there are the secondary causes:

Poor speaker mounts – resonating at some frequencies and not others – upsetting the sound before it even leaves the cabinet.  Especially where speakers are resting on the top of nice symmetrical wooden furniture – and don’t get me started on ‘monitor walls… 🙂

Speakers sat one on top of the other – physical contact causing the speaker not in use to act as a limp membrane absorber to the one in use, causing what may be huge response suck-outs in the order of tens of dB…

Rock n Roll Doctor:

I frequently attend studios where the poor bass integrity has encouraged the client to purchase more and more bass ‘solutions’ – to the point where there may be no bass left to solve.  I have been seen dragging expensive bass trap panels out into driveways to undo the damage caused.

Worse, is the tendency for companies peddling acoustic ‘solutions’ to market generic bass traps as suitable for any environment.  These tend to come in two flavours – either the fixed centre frequency bass trap – often centred at 100Hz – that is sold as a universal panacea, or a wide band bass trap – often claimed to operate over a huge band – usually 100-600Hz, which, when assessed in situ, affects hardly any of these frequencies to any significant degree.

Dr Robert?

Why are these fake solutions peddled by modern day snake-oil salesmen?

Well, a few years ago, all of us in the audio industry were fixated on buying small boxes of electronics – reverbs, midi sound modules, compressors etc., that we were convinced would transform the output of our studios.  When those wonderful magic boxes were replaced with cheap virtual plug-ins, an entire generation of distribution companies and salesmen were cast adrift from the good ship audio.  Bearing in mind that only a fraction of those could find employment designing, manufacturing and selling us Microphones and Speakers (the last physical interfaces that we couldn’t avoid) then the rest turned their efforts towards selling us things that modified our rooms acoustically.

Sadly, apart from soft panels that make the midrange sound better (or get rid of it and make it sound worse, but that’s another story), any effective bass trapping these chaps could sell was going to be either too bulky, too heavy or too room specific to be a mass market product.  That didn’t stop them.  They made the products anyway – even if they didn’t work.  They made them light – so they could ship.  They made them small – so they could ship.  They made them all the same – so they could be mass-produced.  What they didn’t do is make them heavy, bulky and individual – so that they would actually work for YOUR room.

Here are some results from a room boasting £500 of proprietary light-weight bass traps (the sort that look, and feel, like an expensive mattress) – note that when we removed them, the change in LF response was minor and restricted to a tiny change in the lower mid – nowhere near the claims made by the product.

With proprietary bass trap.

mf bt out edit

Without bass trap.

mf lh b down edit

I think the results are self explanatory.

Embrace the difference:

Just like we as humans are all different, then so are the rooms we listen to music in all different.  They require different treatments to achieve the same result – the universal monitoring environment we all crave.  No one says that environment is easy to achieve, but we can all agree that it is not achieved by application of some simplistic, universal treatments.

A comedy of errors:

So, why can we not simply adjust the response of a room by using a graphic equaliser or a digital room correction algorithm?  Well, our ears are fine tuned by millennia of training, to separate out direct sound from an object from the reflected ‘reverberant’ sound produced on the way to the ear.  Sadly microphones – and analysis software – do not have this ability.  In their crude attempts to ‘flatten’ the response, such systems lump both direct and reverb sounds together and attempt to equalise the amalgam of the two.  The result, to our much more sophisticated ears, is a signal now not only twisted by reverberation from reflections, but also by apparently random dips and peaks in the direct response, as the system attempts to correct in a manner as crude and inappropriate as a Victorian electrician trying to fix an iphone.

In conclusion:

You have three choices:

  1. Live with it.
  2. Get someone who knows what they are doing to diagnose it and prescribe a correction.
  3. Gain the experience to correct it yourself.

Now, given that your reading this because 1) is unacceptable,  I’m not about to advocate 3) when I can offer 2) for a sum far lower than the cost of one of those traps that don’t work – am I?!

The Author

Howard Turner has over 30 years experience in the studio business, and for the last 2 decades, his Studio Wizard Organisation have been at the forefront of the development of effective & affordable designs and solutions for studios.  Further information:  +447803666789 web: www.studiowizard.com