It never ceases to amaze me that studio monitors sound very different to each other, even though their specifications claim similar performance. Our monitors are the only means we have of judging mixes, so how are we supposed to do a good job when no two models sound the same and, to further compound the situation, no two identical models sound the same in different rooms?
The reason we manage as well as we do is that the human hearing system is very adaptable, so if you get used to the sound of your room/speaker combination playing back commercial recordings that are deemed to be of a high quality, you soon develop a feel for the sound, and that becomes your new 'normal'. However, it is still very important to minimise the effect of the room on the sound, as our ears are less good at compensating for an uneven bass response, which is what we tend to end up with when using speakers in small, acoustically untreated rooms. Even moving the monitors by a few inches can change the situation. These are factors we covered in detail with our studio acoustics feature last month, but it really pays dividends to attend to them before even thinking about mixing in the room, so I make no apology for returning to the subject here.
One way of checking the way bass behaves in a room (which is often referred to in our Studio SOS series and was also mentioned in the acoustics feature) involves playing a chromatic scale of bass sine-tones, spanning a range of about three octaves. This soon shows up whether some notes are extraordinarily loud or quiet compared to the average, so we made an MP3 of this scale and put it on the SOS web site for you to try for yourself (www.soundonsound.com/sos/jan08/audio/sinesweep.mp3).
Where you sit in relation to the monitors can affect low-end performance, so perhaps you should evaluate your studio layout before using the tones in earnest. Experience has shown that in domestic-sized rectangular rooms it is invariably better to have the speakers firing down the length of the room, rather than across it. Small, square or cube-like spaces are generally the worst, as the listener usually ends up sitting close to the centre of the room, where the bass response will fluctuate the most.
So what do you do if, after trying your best to acoustically treat your room and optimise your speaker position, the result is still less than acceptable?
One approach is to not apply any EQ at all below the frequency at which your room starts to sound uneven, which may be as high as 150 to 200Hz in smaller rooms. That way you can get the music mastered somewhere that has decent monitoring and let them EQ the low end for you. Another tactic is to check your mixes on as many different sound systems, in as many different locations, as possible and keep adjusting the mix until it sounds acceptable on all of them. Back in the days of tape, this often meant making a cassette copy and playing it in the car, but now you are more likely to make an MP3 to play back on your iPod, or a CD to play on a standard hi-fi system.
Personally, I use one of those cheap radio transmitters that have now been legalised for use in the UK, which are designed to allow you to play your MP3 player through the car radio (where no physical input jack is available). These have a range that covers a typical house, so if you plug one into the headphones output of your audio interface or mixing desk you can tune into your mix on any FM radio in the immediate vicinity. There's still no substitute for accurate monitoring, but by making your mixes sound good on a number of audio systems, you can at least minimise the problems.
Paul White Editor In Chief