Review: Supermegaultragroovy Fuzzmeasure & Audiofile Engineering Spectre
So you want to calibrate your room somehow but you currently have no idea where to start? Perhaps it’s time to get a bit DIY about things and analyse ‘the office’ yourself!
14 May 2011
Review: Brent Heber
In conversations with engineers of various ages and experience, one crucial aspect of recording seems to hold a common mystique, a kind of voodoo or black magic if you will: how the space in which we record or mix affects our speaker’s ability to translate our craft.
Acoustics. The word can bring to mind pictures of DIY boxes with lots of strategic holes in them, lots of foam, egg cartons, liberal application of second-hand mattresses and professors in lab coats. It can seem a complex and bewildering ‘known unknown’ that casts a shadow of self-doubt across the hearts of even the most experienced engineers. But is it really that hard and complex? In a word, no. It doesn’t have to be.
I’m no expert – let’s get that straight. My heart lies in mixing and production but I’ve crossed paths with acoustics several times over the years and some AT readers may know that last year I built my own mixing suite within the confines of Trackdown Scoring Stage in Sydney. I had the support of several key engineers and mentors during the project, along with two tools they shared with me that not only made a big difference to my confidence in the room, it also gave me the ability to tweak and finesse it. These were SuperMegaUltraGroovy’s ‘Fuzzmeasure’ (much kudos for company name) and Audiofile Engineering’s ‘Spectre’. The result of all this advice and the two software programs has been that I now have a clear understanding of what’s really happening in this room I call my office.
As a precursor to using these tools yourself, a solid reading of things like Bob Katz’s K Metering standard, understanding the use of sound pressure level meters to calibrate speakers and what pink noise is and how it differs to white noise (and brown noise?) will provide useful background information. If you’re interested in the process of analysing a room, do yourself a favour and dive in the deep end. Read up on some of the basic principles – you’ll be surprised how much you can pick up in a relatively short time.
Understanding more about the room you call your office is vitally important and there are great programs – like the two on the table here – that will aid you in your pursuit of acoustic improvements. You’ll also need to get yourself a measurement microphone that will allow you to interface with the programs. I used the cost effective Behringer ECM8000 but if you’re expecting to do this sort of thing often, Earthworks also makes a microphone for under a grand that comes highly recommended.
FUZZY LOGIC
The first piece of affordable software I became familiar with was Fuzzmeasure, from SuperMegaUltraGroovy. Fuzzmeasure is a comprehensive audio analysis suite that has enjoyed rapid adoption throughout the industry thanks to its clean, simple user interface and OSX compatibility in an otherwise PC dominated field.
Fuzzmeasure works by passing a sine sweep through your system and recording the outcome for analysis. The software then compares the frequency response over time, giving you a bunch of information about room modes, reverb time and the like.
Perusing the interface pictured opposite in Fig.1 , you can see it broken into four easy-to-navigate areas: the left side for selecting which recording you’re analysing; the top half for frequency analysis; lower half for impulse analysis; and the right side that refreshes settings and information depending on what you’re looking at or clicking on. One last idea before we look over the various reports and how to interpret them: be sure to import any calibration data you have for your microphone and run a loop test through your audio interface to calibrate it before making any recordings.
HOW FUZZY: FUZZMEASURE’S PRO GUI
The Frequency Response Window of Fuzzmeasure should be familiar in principle to most engineers, looking much like the plot provided with a microphone or set of speakers. The top image in Fig.1 shows the frequency response of your system, taking into account the speakers, the microphone used, and most importantly, the room you’re in. If calibration data has been provided to Fuzzmeasure for the mic and A/D, D/A stages of your system, what you’re left with is a solid analysis of your speakers and room at your listening position. This provides a great starting point, providing concrete evidence about what’s happening in your room and, more importantly, showing the changes you subsequently make to flatten out/normalise dips and peaks across the spectrum. You can develop a solution (stick up a mattress – whatever you decide) and analyse the results with a simple sweep. Then, if your ‘solution’ only makes things worse you’ll be the first to know!
The Impulse Response Window (also in Fig.1, below the Frequency Response Window) is less about frequency and more about energy over time. This window’s diagram reveals things like time delays between speakers in the short term, or time to the first reflections in the medium term. This window is also interactive with the frequency plot – as you adjust the window of time in the IR window, the frequency plot updates to show you the corrected response: i.e., you may wish to disregard the initial burst of the impulse response and only analyse the frequency response of the reverberation time in the room. PA operators can also use this diagram’s information to set up PA delays to minimise phasing in a venue – Linkin Park, for example, used Fuzzmeasure on their last Australian tour to tune the PA.
NEED TO KNOW
WATERFALLS & REVERBERATION
In Fuzzmeasure’s plug-in menu we find two other very useful tools. Firstly, a ‘waterfall’ plot extrapolates frequency response information over time, presenting it in a 3D diagram – otherwise known as a Cumulative Spectral Decay (see Fig.2 above left). This is one of the most useful tools to help identify problematic room modes – frequencies that get overly excited by energy and ‘colour’ your room. By watching the decay of sound in the frequency domain a waterfall plot shows room modes as peaks and troughs that extend much further than balanced frequency spectra. This is the nature of a room mode – a little bit of energy into a resonant frequency ‘excites’ it and consequently boosts that frequency over time.
All conventional rooms will have modes. The key is to minimise them at the listening position with the use of acoustical treatment, or ideally, spread them out evenly during a new room’s design phase, largely by building to specific dimensional ratios (google Bolt, Griggs or Bonello for more studies on ideal room dimensions to spread modes for best results).
Another way of looking at the same information would be reverb time. The Reverb Time plug-in in Fuzzmeasure shows largely similar information, but arguably in a more easily digested format (see Fig.3 above). As mentioned, room modes will decay longer in the room, and show up as taller peaks in the frequency bands where they’re excited.
WHAT NEXT?
So, you’ve done some measurement of frequency over time, you’ve found your room modes, you’ve spent what money you can on bass traps and diffusion of various styles and done what you can to optimise the space you’re working in. This is often where a studio owner will stop. However, if you were tuning a large space like an auditorium or cinema, or tuning a PA, the next step is obvious – inserting and calibrating a room EQ.
WARNING, WARNING!
The ideal behind a room EQ dates back many years and holds a certain amount of infamy. Basically, you first run up some pink noise through your speakers (equal power at all frequencies) and check the frequency response using a real time analyser (RTA). You then place a permanent EQ over your outputs to flatten the frequency response at the listening position. This is where the disagreements start – a room EQ is only treating the sound coming from your speakers at their point of origin. More modern acoustic theory points out that EQ doesn’t take into account the complex changes in sound over time within the room, such as phase anomalies. In fact, ironically the very act of adding an EQ will introduce a shift in the phase of your signal at that frequency – it’s the nature of the math involved. So the thing is, less is more – a little bit of gentle top end roll off in a bright room, with bright speakers, could help you mix with less fatigue and help your mixes translate elsewhere. The most important thing is to be aware of it, know that you’re monitoring through a coloured system and triple check your early work for translation to other spaces to make sure you’ve got it right.
The Spectre meters are extremely configurable. This setup shows an RTA with Peak/RMS meters below.
IN SPECTRE
Fuzzmeasure is great to this point but it doesn’t provide a real time analysis tool/plug-in. For this I’ve turned to a set of meters than can run standalone as needed, called Spectre, by Audiofile Engineering. These guys make all sorts of interesting little tools, one of my favourites being Sample Manager, a batch processor that augments ProTools quite nicely.
Spectre is attractive for a number of reasons, one of them being that the company does a ‘Spectre Starter’ version that can give you what you need for only $50! And it’s not just good for room analysis work either. I use it for a variety of pro work on an almost daily basis. The program includes VUs, PPMs, configurable ballistics – the works (much like SpectraFoo used to provide).
My approach with room EQ has been very minimalist for the reasons touched on above, but each to their own. Given this was my first solo studio build – and with the advice of those around me – my gut told me to avoid placing too many filters across my speakers. [Very wise. As you mention, there are several issues pertaining to room acoustics that involve phase, so the more you might boost EQ frequencies the more these phase anomalies may simply suck them out – Ed.]
My speakers themselves have a simple set of filters that allow cut or boost in a few frequency bands and adjustable hi and low shelving and bass roll-off. I set these filters using Spectre’s results at the listening position. I also run dual subs in my room, and here the RTA over the LFE channel showed twin peaks and a null between 60 and 80Hz, so I set a parametric on my bass splitter to fill that void and even it up a little, which worked wonders. The hole was quite audible prior to the parametric boost, which meant I was adding much more gain on my LFE channel to ‘feel’ the right amount of sub than was required. Once I filled the hole in the spectra, I could pull the gain back significantly and the bottom end sat much more evenly in the room: a definite, audible improvement.
Obviously room EQ is a debatable topic (as Andy Stewart’s interjection already shows above). In an ideal world the best listening position should be achieved with the best speakers, in the best spot, with the best acoustics. However, not all of us have these resources, and in the interests of pursuing the best we can do within our given limitations, sometimes a little bit of EQ can inform us better about what’s going on in our mix. Just be aware than any EQ over your master section inside a DAW will result in phase shifting in those bands. (‘ARC’ from IK Multimedia is one product that claims to be able to compensate for these shifts within the plug-in and give you a choice of how much corrective EQ to apply. Several co-workers of mine have and regularly use ARC and swear by it.)
MORE DATA IS GOOD DATA
There are many resources on the web to help you refine the acoustics of your mixing/listening room. Rule of thumb: design principles are all well and good, but to my mind, if you can use professional tools, easily and cost effectively to gather solid data on what’s actually happening in your space, why not pursue that information first before hanging up the mattresses and egg cartons? Some of those room acoustics kits have hefty price tags and for all that foam and plastic, they can often be too ‘one size fits all’ to be considered a truly tailored solution.
A bit of data can go a long way in not only defining your needs but also in getting more familiar with your studio and ‘owning’ your creative space – if you’ve never done this sort of analysis in your room, maybe it’s overdue. By all means, employ an acoustician if you can afford one, but even if you do, wouldn’t having some concrete information on hand when they arrive help kick the project off on the right footing? At least then the acoustician won’t think you’ll be easily convinced by smoke and mirrors…
