This month, we sort out monitoring problems and give some practical mastering tips.
By day, Jamie is an electrician, but as soon as he gets home, the chances are he'll go straight up to his bedroom studio and start composing. When we visited him, he was just finishing off a library-music project based on dance-music styles. He called us in because he was having severe monitoring problems, and because he needed a few tips on mastering his mixes in Cubase SX. His monitors are JBL Control 5s, which are not really designed as studio monitors, but the most serious problem actually turned out to be his room.
All rooms have resonant modes that cause a build-up of acoustic energy at certain frequencies, so professional studio designers calculate the room dimensions in order to space these resonant modes as evenly as possible. This, in turn, produces the flattest frequency response. Having two room dimensions the same causes the resonances from the two sets of parallel surfaces to occur at the same frequencies, which magnifies their effect and at the same time leaves larger spaces between adjacent modes. Worse is the case where all three room dimensions are equal, as this often leads to huge peaks or dips in the bass response, especially in smaller rooms. Unfortunately, Jamie's bedroom studio was almost exactly 2.5m x 2.5m x 2.5m, although some large, built-in cupboards gave the room more of an 'L' shape. Because of this awkward layout, he had set up his desk and monitors close to the right-hand wall. He also mentioned that his monitoring sounded bass-light, leading him to over-compensate with EQ when mixing.
Before moving anything, Hugh played his old BBC test disc. Right away, the room sounded both bass-light and very, very ringy, because of the bare plaster-on-brick walls. To reveal the extent of the problem, we asked Jamie to set up a chromatic scale of equal-level sine-wave tones on his sampler so we could listen for hot spots and, sure enough, two adjacent notes were much louder than the rest.
We first tried putting the speakers on Auralex Mo Pads, to prevent vibrations getting into the computer desk on which they sat. Though this cleaned up the sound slightly, it did little to even up the bass end, so we tried changing the speaker positions. By reshuffling the studio furniture, we eventually managed to get the monitors around six inches further away from the corner, which helped a little. We also found that the bass end sounded more even with the room door left open, so we suggested Jamie at least give his mixes a final listen that way before signing them off.
The doors of the cupboards were panelled with painted hardboard, and tapping these produced an audible note at around 100Hz, so we suggested Jamie damp the insides of the doors by glueing rubber matting or heavy carpet onto them, which he said would be no problem. We could feel the doors vibrate as our test bass-scale cycled around, and while vibrating panels can absorb bass energy, these were so resonant that they carried on vibrating momentarily after the sound from the monitors had stopped, which has the effect of 'time-smearing' the bass notes. Damping them should help them absorb rather than re-radiate bass energy.
To kill the very pronounced ringing we could hear when speaking or playing music in the room, we used four Auralex foam panels. To avoid damaging the walls, we threaded cord through the panels and then hung them onto screws fitted into the wall — we let Jamie do this, as he had the biggest cordless drill! We couldn't put a panel immediately to the right of the mixing position, as that space was occupied by a window, but setting the vertical blinds to 45 degrees helped damp reflections from the glass.
On the left-hand wall, just to the right of the entrance door, we hung a vertical foam panel, with another placed horizontally behind the monitors at head height. The remaining two were hung on the bare rear wall, to reduce the amount of sound bouncing back to the monitoring position. The difference this made to listening was very significant, with the ringing gone and the stereo imaging more pronounced. Hugh also rolled up a duvet and jammed it into a rear corner to act as an impromptu bass trap, which made a small but noticeable difference to the evenness of our bass scale, and we suggested that Jamie put any other old duvets he could find in the front corners of the room, behind the studio furniture.
With all the acoustic treatment in place and the bedroom door left open, the bass end was noticeably more even and solid, while the general sound was much more focused and less confused than it had been when all the walls were bare plaster. A further foam panel on the ceiling above the mixing chair would undoubtedly help further, so Jamie added this to his mental to-do list.
During the day, Jamie came to the conclusion that new monitors would also help improve the situation, as the JBL Control 5 speakers are more general-purpose than studio monitors and are the kind of thing you'd expect to see installed in a wine bar or club. They don't have a great depth of bass anyway, and the high end tends to be a bit 'shouty'. Not knowing Jamie's budget, we suggested he look at KRK V6s or Fostex PM05s, as these perform well within their price range, but Jamie had heard Mackie HR624s and hoped he might be able to stretch his budget to a pair of those in the not-too-distant future.
Hugh also detected some low-level clicking coming from the output of the soundcard that Jamie was using inside his computer, but we couldn't find any way to reduce it by changing settings, so it may well have been due to electrical pickup inside the machine. It was barely noticeable at normal monitoring levels, even with no music playing, and as Jamie mixed 'inside the box' it didn't find its way onto his final mixes, so he wasn't too bothered by it.
Having made the room more workable — it will never be perfect, because of its size and shape — Jamie asked us about processing for mastering. Currently, his library music is being mastered by the company releasing it, so our best advice for projects of this kind was not to do anything at all to his final mixes, as the mastering engineer would have better monitors and better equipment, not to mention plenty of experience in making things sound good.
Even for self-released work, it would make sense to master at studios with more accurate monitoring, but, if this is not possible, cross-checking the mixes between speakers and headphones would be better than relying entirely on the monitor speakers. As always, you should always play your initial mixes on as many other systems as possible, including in the car, to see how they stand up to commercial mixes.
We only recently warned of the damage you can do to your music by making loudness the main goal of mastering. Nonetheless, the reality is that you do need to get the subjective levels in the same ball-park as the rest of the world, otherwise your clients will think something is wrong. Large increases in subjective loudness can be achieved using a fast-acting compressor, set to RMS (rather than peak) sensing, with a low ratio setting of between 1.1 and 1.4:1, and a low enough threshold to show around 5dB of gain reduction on the meters. The exact amount of gain reduction applied depends on the type of music: you'd probably use less on acoustic material and a little more on dance and rock music. As you increase the gain reduction (by lowering the threshold or increasing the ratio), listen to see when the compression becomes obvious, then back off a bit if you don't want it to be audible. However, with some forms of high-energy music, the sound of a compressor just starting to assert itself can add to the impact and excitement of the music. We used the compressor that comes as part of Cubase 's Dynamics plug-in, on its Auto release setting, which is often the best option for complete mixes, especially those that change their dynamics throughout the song.
We followed the compressor with a parametric equaliser, adding a decibel or two of boost at 10 to 12kHz to lift out the percussive sounds, and a couple of dB of broad boast at 100Hz, to firm up the low end. This was combined with a very broad, very gentle mid-range scoop, centred at 250Hz. Subjectively, the change in sound was very small, but the mix had more definition and a hint more punch, which is what we'd been trying to achieve. The final touch was to insert another Dynamics section after the equaliser, this time using only the limiter, to trap the occasional high-level peak. On Jamie's mixes, this processing produced not only louder mixes but also mixes that sounded a bit fatter and a little more defined, without being too obviously processed. Jamie seemed keen to try out some of these ideas for himself and he had no trouble following what we were doing.
After playing a few more of Jamie's compositions, most of which still sounded fine on the improved monitoring, we put our tools away and set off back home, but not before stopping at the local fish and chip shop!
"Many thanks to Paul and Hugh for popping over and helping me out — they couldn't have timed it better! The Auralex speaker pads and tiles have made a very noticeable difference to the room's acoustics, and I feel much more confident mixing stuff down in here now. The room sounds noticeably more 'dead' as soon as you walk in, and I can now hear bass frequencies which didn't appear to be there before. With bass playing such an important role in my styles of music, this has helped solve a big problem. I have now lined the inside of the cupboard doors with some carpet, stuck on with the remains of the spray glue Paul left behind, which I think has improved things further. I haven't got round to mounting the acoustic tiles on hardboard yet — we are currently re-decorating the hallway and landing, so it will have to wait — but I'll definitely be doing that soon.
"I decided against the idea of rolled-up duvets in the corners, mainly for aesthetic reasons, but also because I think the other changes have made enough of a difference already. I haven't made any hard and fast decisions on new monitors yet either. I have been recommended the KRK's by a few people now, though a mate has just bought some Mackie HR824s that I heard the other night, which could change my mind... Either way, I will be changing them in the near future.
"I have been putting some of Paul's compression tips into practice on drum loops, with very good results. Using a low threshold with a low ratio certainly helps not to squash them too much (something I have been guilty of on a few occasions).
"The library album (Xtreme Drum & Bass) has now been mastered, and will be available through Online Production Music (OPM). It's a mixture of different Drum & Bass styles which are (hopefully) commercial enough for television, but it also includes collaborations with fellow DJs David Smith & Lee Hirons (Ratty & LJ High), which helps keep its roots firmly on the dancefloor. OPM have also recently released a solo acoustic guitar album by my Dad, titled Guitar Man, so even though our music is worlds apart we've ended up on the same record label!"