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Why sound that travels faster than the speed of sound can ruin your mix

A post by David Mellor
Thursday November 30, 2006
Suppose that you're mixing your latest track. But as well as the direct sound from the monitors, you hear sounds that get to your ears even quicker. That can't be good.
Why sound that travels faster than the speed of sound can ruin your mix

Picture the scene in your studio. You are sat at your mixing console, DAW or control surface, equidistant between your monitor loudspeakers.

The acoustics of your room are relatively well-controlled. So although there are reflections from around the room coming at you, they are not too offensive and don't distract you from the direct sound of the monitors.

But something is bothering you. Somehow things don't sound quite right. What could the problem be?

Well, the problem could be that you are hearing 'echoes' that arrive before the direct sound from the monitors.

Yes this is possible.

All monitors radiate sound from their cabinets. Try putting your ear up against the rear of a loudspeaker cabinet and you will see exactly what I mean. Generally it sounds pretty ghastly.

When this sound gets into the air, it definitely does degrade the sound of the loudspeaker. But you would judge a loudspeaker on its overall qualities taking this into account.

But there is something else that can happen...

The sound from the cabinet can get into the speakers' supports. And from there it can distribute itself all around the walls, ceiling and floor of the room. And all of those surfaces can radiate that sound at you.

OK, it's just like another reflection then? Not too much of a problem?

No, there is a problem. And that is that sound travels faster through solids than it does through air.

So sound from the cabinet, pretty grungy sound at that, is arriving at your ears sooner than the direct sound from the drive units.

It's bound to be confusing.

The answer is to decouple the loudspeaker cabinets physically from the room.

You can buy all kinds of decoupling devices from hi-fi dealers. Anything small won't work so don't bother.

Ideally what you would need would be a heavy slab of material to stand each loudspeaker on. Underneath the slab would be a layer of resilient material.

The heavy slab would be difficult for the cabinet to vibrate, so not much energy would get through. And the slab is decoupled from the room by the resilient layer.

I'm not suggesting you spend a lot of time worrying about this, because usually there are far worse acoustic problems to deal with.

But it is a real thing, and if you wanted your studio to be perfect, you should definitely look into this phenomenon.

A post by David Mellor
Thursday November 30, 2006 ARCHIVE
David Mellor has been creating music and recording in professional and home studios for more than 30 years. This website is all about learning how to improve and have more fun with music and recording. If you enjoy creating music and recording it, then you're definitely in the right place :-)