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Studio SOS: Reflective Surfaces

Kate Ockenden By Paul White
Published March 2013

Kate Ockenden's home studio before the visit.Kate Ockenden's home studio before the visit.

We visit the home studio of TV composer Kate Ockenden and discover that optimising monitoring needn't require acres of acoustic foam.

If the name Kate Ockenden seems familiar to you, it's because we helped her out with one of her mixes back in October 2010 (/sos/oct10/articles/mixrescue-1010.htm). In the meantime, she's been operating her Logic-based studio in the upstairs loft space of an outbuilding at her home in Shropshire. A very capable musician and singer, Kate has enjoyed success with songwriting, performing and producing music for TV, much of it for children's TV programmes, with additional musical input from her husband Geoff.

The subject of studio acoustics came up when Kate discovered that her mixes weren't translating to other sound systems quite as well as she'd hoped, so she asked us if we'd be prepared to take a look to see if anything could be done. The offer of a copious supply of Chocolate Hob Nobs followed by lunch in nearby Ludlow clinched the deal!

Lofty Ambitions

We estimated Kate's studio to be around four by seven metres. Like many loft studios, this one has walls that are only partly vertical before the slope of the roof cuts in. The very apex of the roof has been boarded over to create some attic storage space, however, so there is a slightly bowed section a metre or so wide in the centre of the ceiling. Many people working in such spaces are worried that the odd shape will compromise the acoustics of the room, but the angled upper walls actually have some advantages, in that they direct reflections away from the listening position, and so less in the way of absorbers may be necessary. There were a few of Geoff's amps, guitars and a drum kit at the rear of the room, but other than having to evict the snare drum to avoid rattles while we were doing tests, none of this caused us any problems.

Kate had her studio gear set up on a commercially available desk with two high outrigger shelves holding her Mackie HRM824 MkI monitors. The Mackies had their rear-panel controls set for 'half space' and the lowest 38Hz cut-off frequency, which was theoretically correct given their placement close to an end wall. The speakers were facing down the length of the room, which, again, is usually the best option.

Less than ideal, however, was the speaker platform height, which placed the tweeters somewhat above ear level. Also, having the speakers set up very close to a back wall can compromise the action of rear passive radiators, as employed in these Mackie speakers.

The Low Down

The speaker shelves on Kate's desk were rather high, which meant that the Mackie's tweeters were above ear height. Turning the monitors upside down rectified this, while placing some Auralex MoPads underneath the speakers decoupled them from the desk.The speaker shelves on Kate's desk were rather high, which meant that the Mackie's tweeters were above ear height. Turning the monitors upside down rectified this, while placing some Auralex MoPads underneath the speakers decoupled them from the desk.

Before doing anything else, we played some test tones and music from Hugh's trusty Studio SOS CD, and discovered that the low end in the room was less even than we might like, with a sharply pronounced shelf-like reduction in level below 75Hz and a noticeable dip higher up, followed by a slight peak at around 200Hz. Our first measure to improve the situation was moving the desk a little further from the wall and fitting a pair of Auralex MoPads, with their wedges, to angle the speakers down towards the listening position. The revised speaker positioning improved the accuracy of the mid-range and high end, but didn't make much difference to the bass issues. Moving the speakers slightly to one side, thus disturbing the symmetry of the setup, sometimes helps smooth out low-end wrinkles, so we gave it a shot. It helped a little, but didn't cure the problem completely.

Another potential 'hump and bump' problem can occur when the bass drivers are midway between the floor and ceiling — which these were — so we decided to reset the MoPads to provide a flat surface and invert the Mackie speakers to place the woofer on top. This moved the woofers away from the mid-point of the room's vertical dimension, while simultaneously placing the tweeters at ear height. Again, we heard some improvement but it was still not a complete cure.

That left the monitors' rear-panel switches to experiment with. First, we tried setting the low cutoff switch to 47Hz, which reduced the bass variations considerably but left the mixes sounding a little bass light. Changing the Space switch from half-space to full-space pushed the bass level up slightly, which, in combination with the 47Hz filter setting, gave us a more even low end without sacrificing too much in the way of deep bass. A few more positional tweaks, such as pulling the desk even further away from the wall and adjusting the positions and angles of the speakers on the shelves, left us with the desk around half a metre from the end wall and 200-300 mm right of centre. Playing through our bass-scale test signals indicated a much smoother and better balanced bass response, and listening to our familiar music tracks confirmed a useful improvement in the accuracy of the monitoring system overall.

On Reflection

Here you can see how the whole setup was moved slightly off-centre, which helped to even out the bass response at the listening position. Here you can see how the whole setup was moved slightly off-centre, which helped to even out the bass response at the listening position.

Despite the complete lack of acoustic treatment and the reflective wooden floor only partly covered with a thick rug, the room sounded pretty well-behaved. However, we decided that there would be a small benefit in applying some Auralex foam panels to the walls behind the speakers, each side of a small window. There was also space to jam one between the roof beams above and just forward of the mixing position, to intercept ceiling reflections, with a further panel being affixed to the rear wall adjacent to the door. As we didn't want to mess up the walls by using a permanent glue fixing, we stuck old CDs to the back of the foam panels at the top centre, and then hung them on map pins pushed into the walls.

There were no curtains or blinds on the window, which presented another reflective surface directly in front of the mixing position. Sunlight coming through the window also made it difficult to see the computer screens, so we suggested fitting wooden slatted blinds, to break up sound reflections and cut out glare. Kate thought this was a good idea and added some blinds to her shopping list.

Hugh also spotted that Kate was using a Denon PMA355UK hi-fi amp as a physical volume control between her RME HDSPE AIO interface and Mackie monitors, via unbalanced connections. Although, surprisingly, there were no obvious ground-loop hums, the location of the hi-fi amp behind the desk meant that it couldn't be easily reached. Hugh suggested that she buy a simple passive monitor controller that would allow her to carry a balanced output from the interface all the way to the speakers, and which could be positioned conveniently on the desk. The SM Pro Nanopatch is a very cost-effective option, but as Kate also wanted to be able to switch the monitoring signal to a pair of small domestic speakers that she also had (and which were powered by the amp), the more flexible M-Patch 2 would be a better solution. She would also need to get hold of the optional balanced breakout cable for the AIO interface, in order to benefit from a balanced signal path to the Mackies.

Vocal Point

After we completed our adjustments, Kate played back some commercial material, as well as several of her own mixes, and agreed that the sound was now much more consistent, making it easier to judge how her mixes really sounded. With the monitoring improved, Kate went on to ask advice on where would be the best place in the room for recording her vocals. She had been using a folding fabric-covered screen to help control the acoustics, placing it to one side of the desk with the mic in front and her back to the screen, where she could see the computer monitor and reach the keyboard.

Of course, it is very important to have a large absorber behind the performer, to prevent reflections from the room bouncing into the front of the mic, which, in the case of a cardioid model, is the most sensitive axis. Further screens of some sort — behind, to the sides and sometimes above the mic — also help, which is why Reflexion Filters and the like are rightly popular, but for the best results they need to be used in combination with absorbers behind the singer and positioned at head height.

The folding fabric screen, although used in the right way, was rather too thinly padded to be very effective as a broadband absorber, and it was also a little too low, so we recommended using a cheap polyester-filled duvet instead, which could simply be hung by its corners from a couple of the roof beams. The lightweight fabric-covered screen could then be redeployed behind the microphone. We also pointed out that the edges of the room, as well as the dead centre of the room, are best avoided when recording using microphones, as these locations can produce an uneven sound. A duvet was duly added to the shopping list.

Level Playing Field

While Kate was playing some of her mixes, we both noticed that a lot of her tracks were recorded very hot, leaving little or no headroom. In general, it is a lot easier to mix, and the results usually sound better, if tracks are recorded with sensible headroom margins — just like in the good old analogue days. Tracking with average levels around -20dBFS and transient peaks to about -10dBFS is in keeping with traditional analogue practices. When you're mixing tracks together, the overall level rises, naturally, but won't normally get much higher than about -6dBFS at the main output, so there shouldn't be any need to pull the main fader down to avoid overloads.

This approach makes the mixing process much easier and often seems to make the plug-ins and overall mix sound better, too. More importantly, working with lower average levels doesn't stress the analogue circuitry of interfaces, monitor controllers and speakers quite so hard. After all, these are typically designed for nominal levels of +4dBu, with a headroom margin of 20dB to the clipping level of +24dBu. If you are always running close to the digital clipping level, the analogue electronics will be close to clipping too, and that never sounds good!

The lesson learned from this brief Studio SOS is that worthwhile improvements in sound quality and accuracy can be made simply by adjusting the placement of the speakers in the room and experimenting with speaker settings. It's rare to come across a home studio that delivers a perfectly flat bass response, but as long as you can minimise the inevitable humps and bumps and ensure that the tweeters point directly at the listening position, you can almost always end up with something workable.  

Reader Reaction

Kate Ockenden at her newly re-jigged studio.Kate Ockenden at her newly re-jigged studio.

Kate: "It was quite a relief to know that the room wasn't disastrous. I wasn't sure how much of a problem the shape would present, although I guessed it might stand a better chance of good behaviour than a square or rectangular room with mathematically related dimensions. I had visions of shaking heads, a large quantity of acoustic tiles being glued to the sloping walls and Paul and Hugh attacking my desk with a circular saw! Instead, they calmly moved the desk, turned the monitors upside down and experimented with their settings, carefully placed four helpful acoustic tiles and offered great advice about recording and mixing.

"The whole experience has been extremely helpful. It has proved to me that positive results are not that far away, and are pretty simple to achieve as long as you have a good pair of ears, awareness of your studio equipment's capabilities, and knowledge of room acoustics. I was particularly intrigued by Paul and Hugh's observations regarding hot recording/mixing levels. That will certainly be carried forward as I travel through future projects.”