The SOS Team go hob-nobbing at a stately home this month, and get to grips with the acoustics of a large and lively room.
When we received a call from John Thomson, the Head of Centre at the Ingestre Hall Residential Arts Centre, we really didn't know what to expect. John told us they had a live room adjoining their studio control room (Studio 2) in part of an ancient hall, formerly the country seat of the Earl of Shrewsbury, that needed some serious acoustic treatment to make it usable. He said they would also welcome advice on improving the sound of their control room. When we arrived, our first view of the Hall, set within its own parkland and surrounded by rural countryside, was spectacular and more than a hint gothic. Suffice it to say that if Batman ever decided to move to Staffordshire, Ingestre Hall would be where he'd move to. The illusion was completed by site manager Mike Reay, who looks not unlike Alfred, Bruce Wayne's butler. Mike also takes care of most DIY and repair-related activities and, as it turned out, he was a good man to have on side, as we'd never have finished all the constructional work without him and his site team.
The centre's three music studios are used as part of the multi-arts residential courses for children and young people hosted at the hall, which is run as part of the Sandwell Residential Education Service. Music, art, photo-visual art, drama and dance are all taught in specialist studios throughout the week and over some weekends. It is also possible to book the studio for commercial projects, and the main reason that the centre wished to improve their studios acoustics was to enable them to provide opportunities for up-and-coming musicians to record and produce in the best-sounding environment possible.
The live room in question turned out to be around 14 feet high, 23 feet long and 18 feet wide, with bare plaster walls, adorned only by a few pieces of art that had no real acoustic benefit. This adjoined a fairly small control room, accessed via a vestibule that (if suitably treated) we thought could also work well as a vocal booth. Inside the control room, though, was the largest pair of Dynaudio monitors I'd ever seen, along with a pair of NS10s acting as a secondary reference. The three-way, 2 x 12 Dynaudio monsters were far too big for the room, and John had come to realise that they would be better off selling them and replacing them with something more suitable for the size of the space. Someone is going to get a bargain, as these monitors cost around £9000 new and, though hardly used, will be offered for little more than half that figure.
Some form of commercial acoustic treatment had been used to line the studio walls, but this seemed to comprise less than half an inch of foam-like material on top of metal plating, so although it mopped up the high-end fairly adequately, it did little to control the mid-range and nothing at all to control the bass end. We decided to come back to the control room after we'd decided what to do with the live room.
John, Studio Manager Anthony Evans and Producer/Engineer John Sambrook turned up to help with the work, and they'd also obtained a few office screens to try to achieve some separation between intruments and amplifiers recorded in the room. However, the room itself was so lively that getting a decent drum sound in there was almost impossible, as the overheads were swamped by the room reverb. Thin office screens are ineffective at lower frequencies, so Hugh and I planned a few affordable modifications to both the room and the screens that would help. As we only had one more day on site to complete the job, we decided that the best way forward would be to get Mike to make up most of the woodwork we needed in advance of our second visit, and to ensure we had the materials and tools to hand that we'd need to get the job done. John also managed to 'procure' some heavy curtains from elsewhere in the building, so that we could hang them over the windows to give us a bit more absorption, as up until now they had been completely bare. An ordinary wooden curtain pole was used to hang these.
Because this large room was so lively, we felt that a pragmatic approach would be to build a number of simple rockwool traps and to fix these to three of the side walls. The fourth wall adjoining the control room was already treated with the same thin industrial material as the control room, and there were also a couple of double-layer, double-glazed windows in this wall that provided visual contact with the control room. The traps we specified were simply wooden frames, around four inches deep, with two layers of 600mm x 1200mm x 30mm high-density, cavity-wall rockwool slab (packs of five from Wickes!), fixed inside and covered in unbleached cotton dust sheet. Mike devised a way to attach these to the walls using a wooden support batten at the bottom and a couple of mirror-fixing plates at the sides. He'd originally planned to use staples to fix the cotton material over the traps but his stapler was having none of it, so he finally resorted to using drawing pins which, once fitted, were hidden out of sight behind the traps.
We also specified a couple of shallower traps, containing just one piece of 30mm rockwool. These would be fixed to one side of the office partitions, to make them more effective in the mid-range as well as at high frequencies. As luck would have it, these traps were just the right width for their mirror-plate fixings to line up with the internal metal supports of the screen, so Mike drilled through into these uprights, then fixed the panels using self-tapping screws.
To keep drum vibrations out of the structure of the building, we suggested that an isolated drum riser might be appropriate. The drum riser could be built on-site on the day of our visit and would need to be nothing more complicated than a couple of layers of board sitting on a pad of high-density rockwool. It should be large enough to accommodate a couple of our movable screens as well as a fully-mic'd drum kit, so we decided on an 8-foot x 8-foot format, as this could be built from 8 x 4 sheets with no need for cutting.
When we returned for our second visit, to complete the work, Mike had not only built 20 of our rockwool panel traps but he'd also fixed them to the walls of the newly redecorated room, according to our original layout suggestions. The change in the room acoustic was dramatic: instead of the original, big, empty room reverb, the ambience sounded much more controlled and neutral. He'd also finished modifying one of the office screens to test the principle — and would have finished the others too, had he not used up the centre's entire stock of drawing pins!
Having decided on the best corner in which to record drums, we hauled four sheets of three-quarter-inch marine plywood up several flights of stairs and started to put together our drum riser. First we laid out eight of the 30mm rockwool slabs to form a square just under eight feet on each side, then placed the first two boards, side by side, on top of them. A thin strip was cut from some scrap felt carpet to go between the edge of the boards and the skirting board, so as to prevent direct contact. The second two boards were placed on top of the first but running in the opposite direction, so that when the two layers were screwed together they formed one rigid surface. Finally, Mike rustled up some oak trim to cover the sides of the plinth, made just deep enough to touch the carpet without putting any pressure on it. This made the finished plinth look tidy and also kept the rockwool fibres from escaping.
John's first thought was that they should fix carpet to the plinth, but we suggested using a loose rug instead, so that it could be removed when a reflective floor was needed, such as for recording acoustic guitar. Everyone agreed this was a good solution, and Mike could varnish the plywood to make it more durable and more acoustically reflective. After finishing the plinth, we paused for tea and chocolate orange Hob Nobs, before tidying up the room in preparation for running some practical recording tests with a drum kit. We also took the opportunity to have another look at the control room, to see what could be done there.
The way the control room was set up had the monitors firing across the width of the room. This is less than ideal in smaller spaces but, for logistical reasons, it would be impractical to change (not least because the custom-built studio desk would probably not fit the room the other way around). Furthermore, until the monster Dynaudio monitors had been found a new home, there would be no space for them if the room layout were changed. Our first observation was that the sides of the listening position were fairly reflective, with a window at one side and a heavy fire door on the other. This diluted the stereo imaging and needed to be addressed. A common solution is to build rockwool traps that can be hung in place, one on the back of (or just adjacent to) the door and the other suspended in the window space. If these are fixed up using hooks, they can be taken down and stored, or even used in the live room until needed for mixing. We decided to go with this solution. By the time we left, the traps had been built but had yet to be covered, because of the great drawing-pin shortage! Mike said it would be no problem to arrange the traps on hooks so that they could be fitted when needed.
Bass traps would also benefit this room, and we decided that these could be as simple as further rockwool traps, mounted across the front corners of the room, with pieces of barrier matt suspended directly behind them to act as limp-membrane absorbers. John actually built some to this design for his own home studio and found they worked really well but, again, until the big Dynaudios were moved, there really would not be much space to do this in the control room. As it was, we fitted some Auralex Mo Pads under the NS10s to isolate them from the desk, and to angle them correctly. This produced very acceptable results using just the NS10s. With the Dynaudio's active subwoofer, however, the low end of the room was predictably poorly behaved, which meant that we couldn't be confident about how the low end would really sound once mixes were played elsewhere.
We also looked at the vestibule between the studio and control room, which was big enough to use as a vocal booth. However, because it was fitted out with the same thin industrial surface treatment as in the control room, the mid-range had a slightly honky character. As the studio already had an SE Reflexion Filter, we felt that hanging a duvet across the back of the space, in conjunction with the Reflexion filter behind the mic, would improve the situation dramatically, especially if a few inches of air gap were left between the duvet and the wall. This would be easy and inexpensive to try, and a suitable burgundy-coloured duvet cover would match in with the rest of the decor.
At this point, John Sambrook asked if we knew the best way to set up the mounting hardware for an SE Reflexion Filter, as he'd found it made his mic stand unstable. We've encountered this problem a number of times and come up with various solutions, but in this case we were able to reconfigure the mounting bracket to place the combined weight of the Reflexion Filter and a typical capacitor mic more or less over the centre of the mic stand. This didn't require any special tools or modifications: we just swivelled the parts into a new configuration.
After lunch we co-opted drummer Danny Gee to try out the new recording environment. He set up his kit on the new riser, with a modified office screen to his left, and then used the four part-finished traps waiting to be fitted to the remaining two office partitions to deaden the reflective walls immediately adjacent to the drum kit. Mike Reay said he'd build up some new traps as soon as possible and fix these permanently in place at around head level, as it was clear that the remaining hard walls right next to the drum kit wouldn't help the sound.
Because the ceiling is so high, and because of health and safety issues, we couldn't treat the area directly above the kit, so decided instead to use some Auralex foam screens directly behind the overhead mics. We wanted to test out a couple of the new half-size SE Instrument Reflexion Filters but they weren't available at the time of this article, and in any event their extra weight would have meant bringing in two heavy-duty mic stands. For our test we used an AKG D112 on the kick drum, a couple of AKG clip-on drum mics on the toms, an SM57 on the snare and a pair of Rode NTs as overheads.
Retiring to the control room, we monitored the various mics while Danny played, and other than a few adjustments to the kick-mic position, we had a pretty good sound straight off. What was particularly impressive was the way the overheads now captured a very representative kit sound, with very little in the way of room coloration. By balancing the overhead mics with the close mics, we soon got a nice sound, marred only by the droning of the small tom every time the snare was hit. Gating the toms easily cured this. We then tried a little EQ on the kick and snare mics and also experimented with compression on the overhead stereo pair. Once we'd arrived at a workable sound, we patched in a reverb from Cubase 4 and set up a small, bright room ambience with a decay time of just under one second, which seemed to flatter the kit without making it sound too wet. While Danny was playing, we also checked the main floor for vibration and found it to be much less of a problem than before the isolated riser was fitted.
After tidying up our tools and taking a few photos, it was time to set off home and leave the team to do some 'for real' recording in the newly treated live room. We'd never have finished this project without all the hours put in by Mike Reay and his team, so we can't take all the credit on this one, but the challenge of being able to improve the acoustics of a large room, while sticking to a tight budget, seemed to have been met pretty well.
John Thomson: "We have always known that Studio 2 had the potential to be a great-sounding live room for recordings: we were generally satisfied with our control room but due to the nature of the building, the wide spaces with high ceilings meant that our live room sounded like a cathedral.
"The drum sound particularly suffered, and despite experimenting for a year we just couldn't get a manageable sound out of the live space. We had tried to correct this before, by surrounding the kit with office dividers and hanging duvets over the top, and although this dried up the sound a bit, we then had serious issues with phasing and the sound of the overheads was very poor. The drum floor, the Auralex mic shields and the rockwool wall absorbers have made a tremendous difference and we now have great-sounding overheads that we have an awful lot more control over. The floor was so simple to do, so every studio I set up from now on will have one.
"Mike did an excellent job of making up the boxes. The materials were easy to find — which made them quick to make — and they look really tidy covered with the cloth. The oak trim on the drum floor was the icing on the cake: proper pimpin'!
"We are so pleased that the work has provided a solution for these problems without taking away from the character of the room. We are now running a professional-quality studio that looks and sounds great, within a huge, awe-inspiring stately home, where bands and solo artists can get away from the distractions of the city and be inspired. The work on the live room has really deadened down the reflections, but without destroying what is quite a bright and exciting-sounding room. We're now able to record large bands and choirs there. Thanks to the SOS team, Studio 2 is now the studio we've always wanted it to be."