Studio SOS: Loft Acoustics

Recording in a converted attic, Tom Fox was having serious problems with his acoustics while recording drums, so the SOS team drove over to Yorkshire to sort things out.

Tom Fox is a music technology student at Leeds Metropolitan University and he called SOS because he was having trouble recording a decent drum sound in his studio. Given that the recording space is a converted loft, he suspected that some form of acoustic treatment might be needed, and he emailed over a couple of digital photos of the room to give me some idea of what he was up against. After studying the photographs, I guessed a little acoustic treatment would help and, as luck would have it, I'd just been talking to Paul Eastwood of Audio Agency (the UK distributor of Auralex acoustic foam products), who offered a selection of panels and other bits and pieces for Technical Editor Hugh Robjohns and I to take with us.

Home Studio Acoustics Problems

In order to get an idea of how a flutter echo could be sorted out, Paul rigged up a couple of mattresses over the studio's rear wall. Once some acoustic tiles had also been balanced on top, the problem was completely eliminated. A more permanent solution was then devised by fixing acoustic tiles with adhesive.We arrived at Tom's home in Yorkshire after a longer than anticipated drive, due to the sudden closure of the M1 following an accident. However, Tom brought out the coffee and a seriously large tin of chocolate biscuits which we started to 'download' immediately, and that soon got us back to normal — whatever that might be exactly! Tom's studio is based around Steinberg's Cubase VST running on a 'turbo nutter' 2GHz Pentium IV processor, which he had running smoothly. Monitoring was via a pair of Tannoy Reveal active monitors, while mic preamplification and mixing were courtesy of a Mackie 1604 VLZ mixer. Clearly, technology was not going to be the problem, but the room was certainly less than optimum.

Because of the sloping roof of the loft, side-to-side reflections were minimal, though there were a couple of boxed-in support beams running the length of the studio on either side at around head height (I should know — I walked into them enough times!) that were fairly close to the speakers and therefore a potential source of unwanted early reflections. More obvious was a strong flutter echo between the flat front and rear walls (the studio was set up along the length of the house) which were completely bare and reflective. The rear wall formed the back of an open stairwell which provided access to the studio, and we decided to start with that.

To deal with the oddly shaped room, Paul installed some Auralex acoustic treatment, fixed in place by spray adhesive.

Tom found a couple of thin single mattresses that we propped/taped in place, and then we balanced a couple of the Auralex foam tiles on top of them to cover more of the wall. This lash-up killed the flutter echo as close to stone-dead as makes no difference, so we decided that, as a permanent job, we'd fix four of the foam tiles to the wall and put the mattresses back where we found them.

Two more of the tiles were deployed on the front wall to cut down reflections from behind the monitors and a further two were used on each side of the listening position to cover the side of the supporting beam and an area of the sloping ceiling directly above. We also had a couple of small triangular bass traps, which we used to fill the corners where the supporting beams joined the front wall, but, as the ceiling was sloping, we had to cut the foam to the appropriate angle using a serrated bread knife. The Auralex kit included some rather good spray adhesive, which made fitting the tiles extremely easy, though we discovered it was best to spray both the tiles and the wall, wait around for a minute, then push the tiles into place.

Working On The Drum Sound

Once the foam was in place, the room sounded a lot more controlled and the monitoring environment was much improved. The next challenge was to sort out the drum sound. Tom's main instrument is the guitar — he's only been playing the drums for around eight months — but he was keen to get a good sound so that he could record his own rhythm parts. Tom was looking for a typical rock drum sound, with each drum close-miked and the overheads really just looking after the cymbals. He'd had the kit set up at one side of the room, where the ceiling is very low, and after playing back some recordings that he'd made, it became evident that the sound from the overhead mics was rather coloured, and was also suffering from the reflectivity of the room prior to treatment. The first step was to bring the kit to the middle of the room to give us the maximum possible headroom, though the space we had to play with was still somewhat restricted.

The kick drum had the front head removed and was damped with a pillow, then an AKG D112 was pointed towards the centre of the head.After moving the drum kit, it became clear that the skins on the toms were relatively slack and so the second step was to check the tuning of the kit, because Tom admitted he had little experience in this area. It turned out that, although the kick and snare sounded pretty good (although the snare was a little dull), the toms were all tuned too low in pitch and the sound was suffering quite badly.

While Hugh sorted out the mic cables, I set about tuning the kit and also asked Tom to take the front head off the kick drum, as the hole in the head was too small to allow us to position the kick mic correctly. I don't like leaving the front head off a kick drum for any length of time, as it places an uneven tension on the shell, so I suggested to Tom that he cut a larger hole in the front head and replace it in the near future. The inside of the drum was damped with a pillow in the usual way, so all that was left to do was set up Tom's AKG D112 about half way into the drum on a short banquet stand, pointing directly at the beater — a nice hard plastic one!

All three toms were miked using miniature AKG C418 electret drum mics, which clip directly onto the drum rims, placing the capsule about 2cm above the skin and 5cm in from the rim. They are small enough not to get in the way and the clips are strong enough to hold the mics in place. A flexible bellow in the arm supporting the capsule provides isolation from the mechanical vibrations of the drum.

The snare was miked with an SM57 above and an AKG C418 miniature clip-on mic below.The snare was miked using a Shure SM57 5cm or so away from the head and angled towards the centre of the drum. For overheads, Tom was using a pair of AKG C1000Ss, which don't have a particularly lively high end. However, they were all we had, so we set them up as best we could in the space available and positioned them to try to give the most even coverage possible of the cymbals, including the hi-hat. That left one AKG C418 spare, which Tom had tried using previously to cover the hi-hat. The revised overhead placement was providing a reasonable amount of hat so we clipped the last C418 to the bottom of the snare drum just in case we could get a better sound by miking both heads together — as it turned out, the SM57 by itself was rather lacking in attack. Normally the lower head mic would be set out of phase with the top mic, but as the Mackie mixer doesn't have a phase switch facility, we decided to record it normally and then use Cubase's waveform invert function to do the phase inversion for us on the recorded track. At this stage we fired up Cubase VST and made a test recording.

Listening & Adjusting

Listening to the two raw snare tracks together, the combined sound was rather thin and lacking in body, although the snare 'snap' was more evident. Inverting the lower mic track and recombining with the top mic track produced a much fuller sound with both body and attack, and this worked much better. During his previous recording experiments, Tom had been using a gate during recording, but we explained that he'd be safer recording everything straight, then using gate plug-ins if necessary. The reason for suggesting this approach is that a wrongly set gate will ruin an otherwise good take, whereas if you gate after recording you can have as many goes at getting the settings right as you like.

The kick drum sound was very usable as recorded (though we later fine-tuned it using EQ) and the tom sounds were much better for their retuning. Even though the snare sound was much better than when recorded using a single microphone, we felt it could be improved, so we spent a while experimenting. While the lower mic added more high end and snap to the sound, we still felt the overall sound could be brighter and more lively, so I suggested using an enhancer plug-in, as I've often found these to be good rescue tools for lifeless snare drums.

The multi-band enhancer within iZotope Ozone was used to get a brighter snare sound.Tom loaded up iZotope Ozone, which has an enhancement function which we applied from around 1.5kHz upwards and then set the mix balance by ear. I have never used this tool before, so I may not have been making the best use of it, but the end usually justifies the means in audio. Before long we had a usably crisp snare sound that would have been difficult to achieve without processing. No further EQ was required, as the enhancer had quite a profound tonal effect on its own.

With the whole kit playing, we soloed each track in turn to check for spill and noticed that the floor tom was resonating quite noticeably every time the kick drum was used, so we called up the gate in Cubase VST's dynamics section and carefully set it to exclude everything except direct hits on the floor tom. This cleaned up the overall sound quite dramatically, and though the two smaller toms didn't seem to be causing much of a problem, I suggested to Tom that he have a go at gating those too to see if he could clean things up further.

TBecause the drums were all close-miked, the overhead mics could be positioned to get the most balanced sound from the cymbals.he overhead mics were much cleaner now that the kit was in the centre of the room, but they needed a little EQ presence lift to compensate for the mics' lack of high-end sensitivity — a characteristic of the C1000S. We also rolled off some of the low end, since the overheads were mainly providing the cymbal sound, plus a little ambience, and didn't have to provide the main kit sound as they would in, say, a more jazz-oriented approach. Low end filtering can help maintain clarity and definition when the overheads are added to the close mics, as it helps avoid some of the phase problems that occur when the same drum is picked up by a close mic and by one further away — at the same time, the transients of the drum hits still come through OK. A broad boost centred at around 5kHz helped put some life back into the sound, which just left us with the kick drum to deal with.

This screenshot shows the EQ settings which were arrived at for processing the kick drum track.As I said earlier, the basic kick sound was very usable, but I wanted to get it sounding tighter, which was easily achieved using a little EQ. By boosting gently at 66Hz, and combining this with a notch at 224Hz, the low end of the sound became tighter and more focused, while boosting at 5.7kHz emphasised the impact click quite nicely. The final settings were arrived at by making adjustments with all the kit tracks switched on — if you work on the kick in isolation, the chances are that it will sound wrong when you have everything else playing.

Final Gloss

The final touch was to find a suitable reverb, so we loaded up Tom's Waves plug-ins and tried Rezoverb. By using short decay times of between 0.8 and 1.2 seconds and a bright plate setting, we got a nice sense of space around the snare drum without flooding the sound with reverb. A little of the same reverb could usefully be added to the toms and overheads, but the kick track sounded best left dry. At this point we decided that we had a good enough sound for Tom to customise by experimenting with his plug-ins. However, we did recommend that he get hold of a separate capacitor mic for the hi-hats, as they were slightly lower in level than the crash/ride cymbals, a problem which couldn't be completely cured by repositioning the overheads due to space restrictions. In the longer term, the C1000S could also be replaced by mics with a better top end for use as overheads, as there are now several low-cost capacitor microphone models to choose from that would do this job well.

To round off the day and to help compensate for the long drive up, we adjourned to a nearby Indian restaurant and talked shop until the rush-hour traffic had subsided. There, Tom told us that he'd found the visit instructive and he was also very pleased with the improvement that the acoustic treatment had made to his room.

Thanks to Audio Agency for supplying the acoustic treatment used for this article.