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Studio SOS: Imran Khan

Optimising Your Studio Space
By Matt Houghton

Imran's studio in its original configuration. The iMac, being some way in front of the speakers, was essentially acting as an acoustic screen, and the reflections from the table were contributing to an unclear stereo image. The complete lack of acoustic treatment also wasn't helping!

We visit a reader's studio in a converted garage to improve the acoustics, and to advise on mic selection and recording techniques for electric and acoustic guitar.

Cambridge‑based SOS reader Imran Khan is a keen musician who plays a number of instruments, his main one being electric guitar. In the ongoing search to capture his sound, he's set off down that path so many of us now know all too well: he's gradually acquired various instruments and bits of studio gear (including a nice collection of acoustic guitars, as well as a Fender Strat, a Korg Triton and other keyboards, a pair of DJ decks and more), and then moved on to create a home studio in which to house and record them.

The studio in question is a generously proportioned converted garage, which Imran had configured for listening/mixing at one end and for recording at the other, and had sensibly included a small 'airlock' between two exterior doors. This, along with the raised, decoupled floor and plasterboard‑lined walls, helped keep the noise within reasonable bounds as far as the neighbours were concerned.

Yet, although there was plenty of space, and he'd had the interior professionally converted to a domestic standard, it was proving problematic when it came to recording and listening back to what he'd captured. Imran had experimented with a little foam acoustic treatment, including placing it at the mirror points of the listening position at the 'control‑room' end, as we always recommend, but as it hadn't given him any confidence that it had solved any of his problems, he'd taken it down again — leaving a rather unsightly stain in places, particularly on the ceiling.

When it came to recording, the monitoring system was obviously an issue, so Imran had sensibly tried using his Sennheiser HD650 headphones to take the room out of the equation so he could monitor the recorded sound more objectively. But he was stillstruggling to capture the sounds he wanted, particularly from his main instruments — a nice‑sounding steel‑strung acoustic guitar and a Fender Stratocaster electric guitar, which he had hooked up to a Fender Hot Rod Deluxe tube amp and a number of effects pedals. He was also experiencing some issues with unwanted noise when hooking up some of the effects pedals.

Realising he needed some help and advice to make progress, he contacted SOS — and as he lived just a short distance away from me I headed over to diagnose the problems, returning a few weeks later to help Imran sort them out.

Not Hip To Be Square!

Imran had obviously been reading SOS because there was plenty of coffee and a fair few Hob Nobs to fuel us! The first thing that struck me about the studio space was that it was roughly square in cross section, and twice as long as it was wide. In other words, the space was effectively a pair of cubes. That's far from ideal for a studio space, as we've discussed before. It pretty much guarantees that there will be huge nulls at certain frequencies in specific parts of the room.

As I mentioned earlier, although Imran had done a great job in terms of sound proofing, there were only signs of aborted acoustic treatment. Playing material over his speakers confirmed that the room sounded as boxy as it looked, and walking around the room showed that the frequency response was uneven. It was easy to see that mic positioning for recording would be a truly unpredictable affair in a room like this.

There was some merit in the layout, though. Shelves of vinyl records on the rear wall seemed to be acting as a de facto diffuser, and the 'airlock' porch broke up the cube enough to address the worst of the room‑mode problems.

The sound at the listening position was better than I'd expected in terms of frequency response — largely due to the fortuitous position of the chair rather than anything else, I suspect — but there were still significant issues to contend with. The monitor speakers were set back on stands behind and slightly above the desk, with both a Soundcraft M12 mixer and the desk surface between each of them and the listening position. An iMac — ie. a large screen — also obscured the line of sight from the speakers to the mix position. So while the frequency side of things wasn't the problem that it could so easily have been, the stereo imaging was particularly poor.

Instant Improvements

There's always a balance to be struck on time‑limited Studio SOS projects, and in this case I decided that we'd tackle the basics of the monitoring setup first — because you have to have that sorted in order to make objective judgements about the rest of the studio — and then to tackle the noise and mic techniques for recording guitar. I'd then return on another day to address the acoustic treatment side of things more fully.

We started by moving the Soundcraft mixer toA Shure SM57 proved a more suitable mic for recording electric guitar than Imran's Rode NT1. one side and bringing the nearfield monitors forward, such that the computer no longer obscured them. The mixer was only really used as an input patcher for Imran's stereo interface, and as a monitor controller, so having it there was not problematic.

Despite the desk surface causing reflections, the improvement was noticeable, with the phantom centre image becoming much more stable. Temporarily placing some of Imran's unused foam in between the speakers brought further improvement, and I suggested that raising the speakers away from that surface might help tighten things further. Something like the Auralex MoPads or the IsoAcoustics stands should help here, I explained, or if he preferred a DIY approach he could create some stands similar to those we'd made in a previous Studio SOS visit (https://sosm.ag/jul11-studiosos). But there was little sense doing more in this respect until the room acoustics had been tackled more generally — and for that job I had in mind to try out a Primacoustic London Room Kit, which had recently made its way to SOS Towers for evaluation. So the plan was to return with that another day and revisit the monitoring issue then.

Electric Guitar Miking

Meanwhile, we turned our attention to the guitar recording side of things. Imran had only a single mic, one of the first‑generation Rode NT1s. He had been using this to record both types of guitar, but the results had been a bit disappointing and, as well as advising on recording technique, he'd asked if I could recommend any other mics that might be appropriate.

Imran was also experiencing some problems with noise when using certain stompboxes in his amp's effects loop, so we looked at that first. The connections all seemed fine, but several pedals were using power supplies, and I suspected that the problem lay in a ground loop. We first tried re‑arranging the PSUs in the familiar star configuration, with the amp and all pedal PSUs coming from the same socket — but that didn't improve things. I had some spare batteries with me, so we tried running the pedals off those, and that solved the problem immediately. It wasn't the ideal long‑term fix, but we had much more to do, so we decided that this would suffice for the time being — the noise was workable for practice, and Imran could switch to battery power when recording.

As an ex‑owner of an NT1, I was very familiar with its sound. This large‑diaphragm condenser was something of a bargain in its day, but in my opinion there are much better equivalent mics now, even at the budget end of the market — not least from Rode themselves. I recalled it sounding a little glassy and brittle by comparison with Rode's later offerings, and that's exactly how the Fender Hot Rod Deluxe amp (one of my favourites) came across. A nice, bright‑sounding Yamaha acoustic guitar also came across as being a bit harsh and with far too much pick/pluck/scrape noise coming through.

It seemed clear that while Imran knew plenty about the guitar and achieving the sort of sound he wantedThe spiked mounting plates that came with the Primacoustic room kit made mounting the absorption panels very easy indeed. from his rig, he was less experienced in mic selection and placement. So, with Imran playing some of his typical material, I experimented with some other mics that I'd brought with me.

First up was a Shure SM57, which is a mic Imran had asked about specifically. It's not usually my favourite for miking amps, but it's an affordable workhorse, and there's something wrong if you can't get a usable tone on blues/rock material when close-miking with an SM57! I explained to Imran the basics of close‑mic positioning when working with a directional (cardioid, in this case) mic, and felt through the combo's grille cloth to find out where exactly the speaker was (it's rarely placed in the centre, and the cloth obscured its position). I don't usually like to record with the mic right up on the cloth, though, and placed it at a distance of around an inch away, before running through three different positions (centre of the speaker, edge of the speaker, and in between) with the mic on axis (with its capsule facing the speaker directly), and then off axis (with the mic angled in towards the centre).

We recorded the results and played them back so we could analyse the differences without the sound of the amp in the room skewing our perception. Imran seemed astonished by the differences in sound that could be captured simply by nudging the mic across as little as an inch! The same position is unlikely to work for every track, though, and these fundamentals of speaker/mic positioning are one of the first things you should get your head around when recording electric guitar. Do also remember that directional mics typically exhibit a proximity‑effect bass boost, emphasising the low end as you get nearer to the source.

We repeated the experiment with an old Sennheiser MD421 I'd brought along, which we both agreed gave a slightly nicer sound — not sufficiently better to justify the extra expenditure for Imran, but I think he found it interesting to see what happens when you try out different mics — and I think he'll be more prepared to experiment in future. Other options in this application would include the Electro-Voice RE20 (which I love on guitar cabs, and which has been designed to eliminate the proximity effect) and the Beyerdynamic M201, another favourite of mine, which has a slightly tighter polar pattern than the others, and which can be obtained very inexpensively.

I usually use a multi‑mic setup on a guitar cab, but we didn't really have time to try anything like this out. Still, I explained how to configure multi‑mic setups to avoid phase‑cancellation problems, and about how to use mics to get more ambient sounds to mix in instead of reverb (when you have a decent space to work with!).

THD Hotplate

I really like the Fender Hot Rod Deluxe, but as it comes it's not the ideal home studio amp because to get it in its sweet spot you have to have the thing turned up bloody loud. Even if your neighbours don't complain, that makes it very difficult to objectively assess the sound coming through the mic without constantly recording and playing things back. Knowing in advance that he was using this amp, I had brought along a secret weapon — my THD Hotplate. This is a powersoak which is placed between a valve amp and its speaker. You connect the amp output to the Hotplate's input and the Hotplate's output to the speaker (despite the identical connectors, don't use a standard instrument cable or you'll fry something you don't want to!). The Hotplate converts some of the amp's energy into heat and passes on a lower‑level signal to the speaker. This enables you to crank the amp settings up to get the power stage crunching as you wish, without the levels becoming too loud to work with. This enabled Imran to get a much raunchier sort of sound out of his amp — and really put a smile on his face! It's worth mentioning here that different models of powersoak seem to work better for different applications. In this application, the idea was to attenuate the signal just enough to get into sensible recording territory — and for that I find the Hotplate works very well. But it's far from the most transparent-sounding thing if you're trying to get maximum attenuation, where something like the Sequis Motherload Elemental does a rather better job.

Acoustic Guitar

We then moved on to the acoustic guitar. You have to remember that acoustic treatment requirements when recording can be very different from those when mixing because very often you'll want a livelier sound for recording. What this means in most home studios, where the space is going to be used for both applications, is that you'll want to configure the room for mixing and then have mobile treatment to create the right space for recording.

I ran through the usual tricks for controlling the acoustic, which included placing a polyester duvet behind the player. That's pretty effective in attenuating unwanted reflections from behind the performer hitting the mic — certainly in the sort of frequency range that we're talking about with vocals or acoustic guitar, anyway. You can place a Reflexion Filter or similar device, or another duvet, behind the mic as well, to reduce the sound from the guitar and/or singer from bouncing around the room — but you may not need that, depending on the room in question. If you find that such treatment controls the sound nicely but leaves it sounding a little too dry, you can either add liveliness back in using reverb, or you can try adding controlled reflections back in using a wooden board or some such — in fact, that can be a good way to get a nice lively recorded sound in a relatively dead‑sounding control room.

As with the electric, we recorded Imran playing his acoustic guitar using his NT1 in a few different positions, before playing these back to see what Imran thought about the difference in sound. We started with the mic out towards the 12th fret and a few feet away, which gave quite a thin yet mellow tone. Then, I moved the mic closer to the soundhole (not pointing directly at it), which brought in more of the 'boom'. You can often get quite a bit of variety simply by moving the mic between these two positions, and it's a great place to start learning about mic position on acoustic guitar — but I rarely find it gives me the most pleasing results. We then tried placing the mic lower down, only a couple of feet off the floor and looking up towards the soundboard (with Imran sitting on a stool), and then up somewhere between the soundhole and 12th fret. The latter seemed reasonably flattering, but the NT1 still seemed to be imparting an undesirable harshness, so I dug out what I felt was a more appropriate mic for whatWith the Primacoustic wall panels in place, and the speakers moved onto the desk so that their sound was no longer being obscured by the iMac, the improvement in sound at the monitoring position was considerable. Imran had in mind: an AKG C451 B. This is a small‑diaphragm cardioid condenser mic which has a reputation for sounding quite bright, but it's bright without sounding brash, and I find it does a great job when you want an acoustic guitar sound that can cut through a rock/blues/pop sort of arrangement. We tried it in broadly the same positions and it sounded lovely by comparison to the NT1, with the details of the performance picked out nicely: bright‑sounding but noticeably smoother and nicely flattering, as I'd expected. These mics aren't cheap, but I've picked them up for very little secondhand and they're worth looking out for.

Logic

As the sun dipped below the horizon, we decided to have a quick look at the software side of Imran's studio before I left. Compression wasn't exactly a mystery to Imran, but he was still finding that setting it up was a slow process, so I showed him how to select a compressor preset and tweak it to taste, by first setting the threshold appropriately for the material, and then juggling the attack and release settings. The preset will never be precisely what you want — not least because a compressor's action always depends on the relationship of the threshold and the input level — but if you know what you're doing they can help you work much faster. What's more, auditioning presets in this way can be a great way to learn how the different controls interact, and you'll soon gain the confidence to set compressors up from scratch to do the job you want. (For more on this approach, read Mike Senior's excellent article from SOS September 2009: https://sosm.ag/sep09-compressionmadeeasy).

Next up, I demonstrated a technique for faking stereo width and ambience on a dry‑ish mono acoustic guitar recording using a reverb plug‑in set up on a send: rather than simply have the guitar in the middle and send to a stereo reverb, you can pan the dry signal to one side and the 100 percent wet reverb signal to the other. It doesn't always work, but it can be really useful in keeping the guitar out wide and leaving space for other elements in the centre of the mix — and it's always mono‑compatible. I also ran through a few very general tips and tricks for using EQ. Unless you really have a good reason, it's usually best to use broad Qs when boosting and narrower ones when cutting (it's easy to remember: broad boosts, narrow notches). I also demonstrated just how much you can tweak a signal such as acoustic guitar by using a subtle high‑shelf boost or cut, and experimenting with the turnover frequency of the shelf to bring out details without overcooking things.

Imran picked my brain on a range of other issues, such as how to avoid phase problems when using multi‑mic setups, but as we were running out of time, I quickly ran through some advice for sorting out the acoustics in the studio and covering up the unsightly foam‑adhesive stains, and pencilled in a date to return with treatment in hand...

Acoustic Treatment

By good fortune, Primacoustic got in touch to ask if we could evaluate their London 12 Room Kits, and Iran's studio seemed to me to be the perfect place to try it out. These kits come with pretty much everything you need to do the basic acoustic treatment in a studio space, and there are three different versions for different-sized studios. The smallest in the range provides enough pieces to sort out the control room end of a typical home studio, while the London 12, the largest of the three kits, caters for the full treatment of a decent-sized room. Primacoustic offer plenty of guidance on their web site (www.primacoustic.com/london.htm) about the different configurations in which these kits can be used, and even if you're not buying one, there's good advice on there about home‑studio acoustics.

When I next visited, Imran had heeded my advice: he'd moved his monitors forward a little, invested in a Shure SM57 and started experimenting to find the sound he wanted. He had also used some white spray‑on stain concealer to mask the adhesive stain (it really is brilliant for this!).

Of course, every room has its own idiosyncrasies, and in Imran's studio we had to tweak the layout of the kit a little bit, partly in order to accommodate some of Imran's gear (in particular his wall‑mounted keyboard stands and DJ decks to the left-hand side of the mix position), and partly because of the floor‑to‑ceiling vinyl on the rear wall leaving no space for tiles there.

Installation was easy, as the kits are supplied with all the necessary fittings, most of which come in the form of metal spiked plates that you screw to the wall, before spearing the panels on to them. The neat thing about this approach is that you can be really sloppy in your positioning of drill‑holes and still put the panels in the right place! You'll just need a ruler, a drill and a spirit level (you can use a free smartphone app for that) to line up the panels.

We fitted the corner bass traps and basic mirror-point panels to the walls as per the guidance. And then we went off‑piste, using some of the smaller panels intended for keeping the rear end of the studio a little more live in the area around the wall‑mounted gear. That left us with some spare panels, which we decided could be used on the ceiling mirror point. We didn't have suitable fixings for that (some are available from Primacoustic for this purpose), but tests confirmed that placing panels there did make a difference.

With further wall panels in place, we carried out some listening tests to ascertain just what sort of improvement installing this kit had made. We'd performed the bass 'stair' test (playing bass sine waves progressively up the keyboard to identify which notes leapt out of the speakers and which were too quiet) before installing the kit, and did that again now — and the difference was startling. We also played a number of tracks that we knew would show up problems in the lower part of the spectrum, and I was surprised by just how effective the Primacoustic kit was, considering that the panels are not that thick. Primacoustic have evidently done a good job in perfecting the material they've used in these panels, and I suspect that the air gap that the brackets put behind them contribute to their effectiveness too. It would be possible to make similar improvements in DIY fashion with less expense — as we've often done in the pages of SOS — but I think the Primacoustic kits do a great job for the money, considering that they're so easy to fit and, compared to the usual black foam, pretty elegant too.

The result was a studio in which Imran now felt confident to make judgments on both his recordings and his mixes. I left Imran promising to get back with details of the necessary parts to attach the ceiling panels more permanently (I wasn't going to stand there, arms aloft, while he mixed!) and made for home.  

Reader Reaction

Imran Khan: "I want to say a big thank you for all your advice and efforts at the Studio SOS visit. It was fun and a learning process at the same time. The sound of the room is really tight, and I'm very happy with the improvements. I managed to get rid of the horrible adhesive stain on the ceiling with the stain seal product you recommended — so thanks for that. I have also got some heavy breeze blocks under the speakers, and finally own an SM57 mic and a short stand — and have been experimenting more with mic placement and recording.”Imran at his newly treated studio.

Published April 2014