Bass Traps - pt1

When I first started working from my own small studio everything I mixed was too bass heavy even though it sounded totally fine in the studio. The mysterious equipment dealer guy who looked like he escaped from Miami Vice called Jeremy came by one day and I explained the problem and without missing a beat he said: "You need some more bass trapping, son!'s gonna cost ya!" and in my mind of course, I was thinking "What... what...MORE trapping? I don't have ENOUGH bass! And what the hell is that terrible shirt all about?" And that - was the beginning of the never ending adventure that was practical studio acoustics. The bad news for that control room despite it being treated was that it was already quite small, and more bass trapping takes room, so the options were limited, but sure enough...after a load of research, I swapped the whole configuration of the studio, moving to the live room, and turning the old control room into the live space. I hired a guy to do a plan, and then built some huge BBC D2 design bass traps tuned to the lowest room modes for the corners, and installed yet more panel trapping around the entire lower half of the room like the genius said. And instantly, even though the live room was now pretty small...the recordings drastically improved.

Now, the ideal way to do it is to build your control room with room mode friendly dimensions in the beginning, then add additional treatment which is exactly what I did the next time - but most of us don't have that luxury, especially at home or in an existing smaller space. Bass is powerful. Like Thanos powerful. It literally almost cannot be stopped, so the term "bass trap" is a little're not trapping ANYTHING - it's more like a "bass speed bump" but that's not as catchy of course. Bass trapping serves to attenuate the power of the wave reducing the effect that it has in the space. Most home-sized spaces are pretty small when it comes to the world of bass; A 100hz tone has a wavelength of a little over 11 feet to complete one cycle - and that's not even really low! 50hz is 22 feet long. This is an epic topic to go into, but for now I’ll just say physics creates some complexities involving the interaction of the waves with your room dimensions and each other the end result of which which means that depending on where you are in the room you may experience a pretty inaccurate sense of what is really happening with your low end. Generally these room modes can be predicted from your room dimensions, though the construction also has a big effect on reality which is why a room mode calculator alone is not enough. That said, here is a great online tool you may wish to try if you are curious and want to see:

So, from the dimensions we can see what is *probably* happening, but brick walls act very differently to studwork and plasterboard walls. Perhaps you have a big false ceiling above you? A bouncy wooden floor? A huge storage space at the back? Maybe a thin back wall leading to a hallway? Posse of homies on the sofa? All of these act as bass trapping to some degree...and in fact are all useful when it comes to practical studio construction.

We have all been in a room when something rattles when the bass is loud, right? Let's say that thing resonates most centered at 100hz. When the bass note is played, it physically moves, and that movement is converted to heat. What made it resonate? The sound wave - which then loses the amount of energy required to make the movement happen. This is bass trapping in action!

In the case I mentioned above I had some severe nulls - that is - around the listening position, the waves interacted in such a way that they cancelled out some key areas in the low frequency so naturally - I'd overcompensate. Maybe counter-intuitively, adding bass traps would reduce these issues, but was impossible in that space. In general with studio acoustic design you're trying to get your reverb decay time more even, or flatter across the frequency range your monitors spew out. Add some foam tiles, that'll damp down the high end and high mid...but the rest of the frequency spectrum stays pretty much unchanged. The lower you go, the harder it is to control, and why if you only use tiles or the like you are more likely to end up with the kind of issue I had as you aren't even touching the low end with your treatment.

You wanna see what is happening in YOUR listening position? Sure you do. Grab a reasonably flat mic (it’s close enough at this stage!) use this, and find out:

How were those results? Oh dear. I guess we better either buy or make some bass traps next week huh? Stay Tuned!

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Adam Whittaker