Studio SOS: An Untreated Room

Alex’s setup is based around a 27-inch iMac and a Roland Octa-Capture interface.

Down at the bottom of the garden, among the birds and the bees, we went to Alex Hutchings’ studio, to eliminate some unpleasant frequencies.

Alex Hutchings is a familiar face at music trade shows, usually pulling impossible licks out of a guitar to demonstrate some amp or pedal, and when he’s not doing that he runs guitar workshops, plays gigs, and also composes and records music.

Until recently he’s used a little Logic Pro X system running in a downstairs room in his house in Bristol, but he felt he needed more space and an environment that wouldn’t be open to interruption. Moving to a bigger house wasn’t a financially viable option, so after much deliberation Alex decided to have a customised ‘home office’ built at the bottom of his garden, complete with double-glazed patio doors and windows, plus extra soundproofing in the building’s structure.

The bare walls were reflecting a lot of sound back to the listening position, which contributed to a washy, unfocussed sound.All this was expensive, but the room is spacious, lets in plenty of light and it looks fabulous, with a high-quality laminate floor, and is decorated with alternate white and green walls. Although it wasn’t planned, Alex subsequently discovered, purely by accident, that the green back wall worked perfectly as a green screen for his occasional video work, too!

Internally the dimensions of the main room are four-metres wide and 5.5-metres long, with a separate two-metre by one-metre room taking up one corner (which may become a bathroom in the future). The ceiling slopes across the width of the room, so that the wall is just over 2.16 metres high above the patio doors, falling back to 1.7 metres in the far corner. The average height is around two metres.

When we arrived, Alex had his Yamaha MSP5 active two-way monitors set up directly on the surface of a desk, on either side of a 27-inch iMac running Logic Pro X, with a Roland Octa-Capture eight-channel audio interface. An M-Audio Keystation 49 MIDI keyboard sat in front of the monitor and, at the time, Alex had been recording some guitar parts using the new Roland GT-001 guitar effects unit. A large V-Drum kit with a TD-30 sound module sat off to one side of the room, constructed on a thick rug, which itself sat on a layer of heavy carpet tiles to damp floor resonances and reduce the thumping from the kick-drum pedal.

Time To Reflect

Clearly the main issues here were associated with acoustics as, other than a couple of rugs, the room was completely untreated, and playing back some tracks confirmed that the room sounded splashy with badly focused stereo imaging. There were also some bass resonance issues from obvious room modes, as well as coming from the floor construction.

A pair of IsoAcoustics monitor stands were used to decouple the monitors from the desk. Ceramic tiles were placed on top of the stands to add mass, as the stands were designed for larger monitors than the Yamahas that Alex was using.IsoAcoustics kindly provided us with a pair of speaker platforms, and though these were a little too large for the Yamaha monitors, we decided to stick with them as Alex was planning to upgrade to larger monitors in the near future anyway. However, to get the small Yamaha monitors to sit securely on the platforms, which we assembled using the short legs and front spacers to achieve a slight upward angle, we bought some 8x10-inch ceramic tiles from the nearby B&Q DIY store, along with some non-slip rubber matting. We used two tiles on top of each speaker platform, with a layer of the matting placed between them, and then cut further pieces of matting to go beneath each speaker. With the speakers angled in appropriately we now had the tweeters aimed at an imaginary point just behind Alex’s head when he was seated in his mixing chair, and playing the same test tracks showed the lower registers of the sound had tightened up noticeably and the surface of the desk was now virtually free of speaker-induced vibration.

Floor tiles proved effective in damping the resonance of the floorboards.To deal with the splashy room sound, we deployed 10 squares of Universal Acoustics foam, tackling the mirror points first. We glued panels to each of the side walls on either side of the desk, and put two more behind the speakers, where the height of the panels from the floor was calculated such that the centre line of each panel was in line with Alex’s ears. We had space for two panels on the left, but only one on the right because of the location of a window. This was fitted with slatted blinds, which work reasonably well for scattering reflections when left set at a mid-way angle. Two more panels were fixed behind the V-Drum kit, on either side of the corner formed by the right side wall and the end wall of the bathroom partition.

Foam On The Range

That left three panels to treat the rear wall, but Alex didn’t want to glue these in place as he wanted to be able to use the wall as a green-screen background when necessary for his videos. So, after a little head scratching, we came up with the idea of fixing loops to the rear top edges of each tile and then sliding these over a curtain pole extending the full width of the rear wall. The pole, with tiles attached, could then be lifted off its brackets when the green screen was needed, but otherwise be left in place.

Removable rear-wall absorption was fashioned with the help of some acoustic tiles and an extendable shower rail.Again, B&Q provided the necessary bits and pieces in the form of a curtain pole and Velcro straps of the type you might buy to keep your cables tidy. We simply looped the Velcro straps, then stuck them to the back of the panels using spray adhesive. The pole brackets were fitted as close to the side walls as possible to leave the majority of the green-screen area clear, and set at a height that allowed the mid-point of the tiles to be positioned at seated head height.

This strategy not only worked fine, but also looked in keeping with the rest of the decor. Moreover, this construction also had the advantage of suspending the foam panels slightly away from the wall, extending the effective bandwidth of absorption to slightly lower frequencies.

Alex had also ordered a sofa bed to put at the back of the room (to replace the small arm chairs that were there at the time of writing), which would further help in absorbing rear-wall reflections and, depending on the construction, might also be of some benefit at lower frequencies too.

After completing the acoustic treatment installation we repeated our listening tests, and noted a very significant improvement in focus and stereo imaging, but we still had some bass resonances to investigate, so I constructed an equal-velocity chromatic scale of bass notes using the EXS24 sampler in Logic Pro, set to its default sine-wave tone. Playing this through the monitors showed up a couple of quite significant resonances, one of which corresponded to the pitch heard when tapping a foot on the floor near the mixing position. To help improve this we suggested some form of damping floor covering in the region of the mixing chair, although this would need to be smooth and tough enough for the chair to roll on. Yes, it was another B&Q solution, this time a pack of interlocking rubbery floor squares of the type used in garages or workshops. When placed in front of the desk these added some useful damping, and although the floor resonance was still evident if you tapped your foot, the decay was noticeably shorter. The best solution would have been to put a layer of heavy barrier matting over the whole floor before fitting the laminate, but reworking the floor now would mean removing all the skirting to allow the laminate to be lifted, and that would bring with it a significant risk of damaging the wall finish, so it wasn’t something we wanted to consider during our visit!

Logic’s EQ was used to negate some of the room’s remaining frequency anomalies.Alex asked about the effectiveness of foam wedge corner bass traps to help reduce the room modes, but in our experience you need a lot of them to make a significant difference, and that can end up being very expensive. One rather less costly solution we have found to be effective is to use glass-fibre loft insulation, left packed in its rolls with the protective plastic bag still in place. These rolls can be stacked vertically in corners and then hidden behind fabric screens. Alex said he would consider doing that in at least two of the corners, but for today we resorted to using some monitor EQ to dip out the worst of the offending frequencies.

Dip It Good

For this purpose we used Logic’s EQ plug-in to create four notch filters, the idea being to counter the most noticeable resonant peaks, but to ignore any dips, as the ear is less sensitive to dips than to bumps (and asking such small monitors to fill in big response dips would compromise the system headroom dramatically!). The end result of this monitor EQ compared well with the sound from good headphones, and this approach works well enough as a compromise solution. However, you have to take care when recording in the same room that your sound source doesn’t set off any of the same resonances, which would then be recorded. As the worst hot spots were below the usual vocal and acoustic guitar ranges, it would still be safe to record these in the room, something we later confirmed in a practical test.

The frequencies we dipped out can be seen on the accompanying screenshot, and when Hugh compared our results (obtained by listening to the chromatic scale while making adjustments) with those from a room mode calculator, they were pretty close given that we couldn’t allow for the effect of the bathroom partition or sloping ceiling. This EQ setting was saved as a plug-in preset, which Alex would have to insert in the main mix bus in Logic Pro for monitoring purposes, but would then have to remember to bypass it when either bouncing a mix or listening on headphones. (Other DAWs have dedicated separate monitor outputs where such an EQ process could be left all the time without affecting any bounces or exports.)

A dry recording acoustic was achieved using an sE Electronics Reflexion Filter opposite an Aston Halo screen.When Alex changes his monitors and maybe adds some of our suggested DIY bass trapping, this EQ setting will need to be rechecked, and hopefully the depth of the notches can be reduced. Heavier floor coverings would also help as the floor seemed to be overly resonant, so maybe putting a section of heavy barrier matt beneath each rug rather than carpet tiles, and beneath the rubber matting, would be worth considering.

Screen Time

After all this work, Alex agreed that the sound from his monitors was now a lot cleaner and corresponded much better with what he heard using his headphones, so our next step was to set up the Aston Halo vocal screen, kindly provided by Sonic Distribution, to see how recorded vocals would sound. Alex already had one of the smaller sE Reflexion Filters, so we suggested he place that behind him to reduce the level of reflections passing over his shoulders into the mic. Using this rather unusual-looking setup, Alex ran through a test song and we achieved a perfectly usable vocal sound that required only a little compression and reverb to give a polished final result.

The room, post-treatment, exhibited a markedly improved monitoring acoustic.Alex had already discovered that using some of Logic Pro’s low-horsepower reverbs — such as Silver Reverb — actually works well on vocals, as their coarser character adds the required texture without making everything sound too smeary. However, one Logic Pro feature Alex hadn’t discovered was the Low Latency button, which is incredibly useful if you’ve set up a lot of latency-heavy plug-ins and then have to go back to re-record or overdub a part. Switching on Low Latency mode simply bypasses any plug-ins that cause significant delays, so that you can record your overdub or replacement part without distracting latency, then simply turn it off again.

We also proffered a few tips on recording the acoustic guitar, specifically recording over one of the uncovered areas of floor to add more life to the sound, and then to move the guitar relative to the mic while monitoring on headphones to find the sweet spot. The textbook mic positions are always a good place to start, but they can usually be improved upon by fine-tuning.

By this time the day was wearing on, we’d given Alex’s coffee and cookie stash a good thrashing, and we had the Bristol rush hour to contend with, so we set off into the traffic leaving Alex in his gorgeous garden studio.