FFW07: Lessons in coupling & isolation

Setting up studio monitors is never as simple as it sounds; not if you want to get the best performance from them. After finding the right positions within the room, you've got to make sure they're properly mounted and isolated. This First Word, written sometime in 1999, discusses simple things you can do to improve the sound of your monitors by paying attention to mounting, coupling and isolation.

Lessons in coupling and isolation
“Yikes, those Questeds are making my ATCs sound bad!” I cried. Brad was somewhere behind the console, fossicking for test CDs in a dirty blue milk crate. “Ha!” he laughed, “I dare you to print that!” “No, no,” I explained, “my ATCs don’t sound right when those Questeds are sitting next to them... the low mids have gone all lumpy!”

Brad and I had just unpacked the Quested VS2108s and, noting their size, decided to sit them flush beside my ATCs for a quick and easy A/B comparison. But at 34cm wide, the Questeds’ imposing baffles were playing havoc with the dispersion of the considerably slimmer ATCs, coupling the lower frequencies and making them sound dull and ordinary.

Interesting? Not really. It’s simple physics, and it’s something that PA operators deal with whenever they stack multiple boxes side by side. But it’s been about 15 years since I stacked a PA system, and acoustic coupling was the last thing on my mind as we lined up the Questeds beside the ATCs.

Switching between the ATCs and Questeds showed that neither pair were sounding worthy of their respective price tags. Taking the Questeds off the bench returned the familiar ATC sound. Likewise, removing the ATCs and listening to the Questeds in isolation revealed a much higher level of sound quality, certainly more in line with their reputation.

Lesson #1: Never compare monitors in any kind of side-by-side situation. It may seem like a good way to make a direct A/B comparison, but all you’ll actually be testing is how badly each monitor affects the other one. Retailers, take note…

Later that week, during an AudioTechnology ‘Spontaneous Human Consumption’ event at Brad’s place, Michael Stavrou spent a critical moment listening to the Questeds, rubbed his chin for another critical moment, then said, “You got any marbles?” “Dunno,” said Brad, “take a look around.” “How about washers?” Stav asked. “Ditto…”

You can dig up all kinds of interesting stuff while fossicking around Brad’s place but his marbles and washers were too well hidden, so Stav returned with half a dozen beers. He carefully removed the top from each bottle, and placed three tops under each Quested in a triangular shape (one under each front corner, one half way across the back). The performance increase was obvious to all, and became a hot topic for the next half hour or so. Just long enough for the beers to go flat…

Lesson #2: Lifting a monitor’s bottom off the surface it rests on minimises physical contact, thereby reducing the amount of sound energy being drained out of the monitor and into the surface. This ‘draining’ of energy out of the monitor causes a decrease in performance, but it gets worse: if the surface is not sufficiently well-damped, it will re-radiate that energy back into the room, causing an even further decrease in performance.

Brad’s monitor bench is about six feet long, reasonably rigid, and supported at each end. But the Questeds have a large and squarish footprint that provides a good contact area with the bench, and they generate a lot of low frequency energy for their size. Combine these factors with their 22kg weight per box, and you’ve got a powerful source of low frequency energy with a large footprint and considerable mass pressing down onto the bench, allowing an even better draining of energy.

Interestingly, my ATCs are designed with three feet fitted in place for this very reason – and never suffered this problem when mounted on Brad’s monitor bench. But why three feet? Why not four or more?

Lesson #3: Proper monitor performance requires stability. Powerful small monitors, such as the ATCs and Questeds, really need to be held stable. If the box wobbles or rocks in any way, it causes loss of output, blurring of the stereo image and smearing of high frequency detail. JBL’s Doug Button discussed this concept, which he calls ‘inertial grounding’, in my review of JBL’s LSR32s [Vol. 1, Iss. 4.]

So why three feet? Three points defines a single plane, and therefore offers maximum stability - that’s why microphone stands, camera tripods and my favourite ‘non-rocking’ café tables are all designed to stand on three feet. (Of course, ‘tripod’ literally translates to ‘three feet’. Duh!). Increasing the number of feet beyond three increases the possibility of instability and wobbling - not a good thing for microphones, cameras, steaming hot cappuccinos or studio monitors.

While Stav’s beer bottle tops demonstrated the benefits of isolation, they were only a temporary solution. Brad has since replaced them with height-adjustable brass cones designed specifically for decoupling speakers, which are available from your local hi-fi shop. Due to the squarish footprint and weight distribution of the Questeds, he’s using four cones - one under each corner. Being height adjustable, he’s able to fine-tune them for maximum stability. His Questeds are now sounding better than ever.

So if your monitors are sitting flush on their bottoms, get some cones under them ASAP! You won’t regret it. But make sure you put the cones the right way around – which is upside down. Their large flat end connects with the bottom of your monitor, while their small pointy end connects with the surface your monitor sits on. When done correctly, your monitors will look like they’re standing on tip toes. (In fact, the first commercially available cones were called ‘Tip Toes’.)

So how do the cones work? Physically, their pointed ends provide a solid connection between the monitor and the bench, which keeps the monitor from wobbling. But their small contact area with the bench creates a very high acoustic impedance, the sort of thing that sound energy prefers not to travel through. With the weight of the monitors pressing down on them, the cones are able to firmly anchor the monitors to the bench while simultaneously providing acoustic isolation. Amazing, huh?


I first met Brad Watts during the days of AudioTechnology's miserable predecessor, Sound Australasia. I was looking for a Mac-savvy guy to write a regular Macintosh audio column, and Brad came highly recommended from the people at AudioMedia magazine. We made an appointment to meet in my office at Pacific Publications. While waiting for this 'Brad Watts' to arrive, a feral-looking bicycle courier walks through the Pacific Publications cubicle farm, dreadlocks flowing and talking into the air with some kind of assertive certainty, just like a crazy guy. He stops at the door of my office. "Simmo? I'm Brad Watts, hang on a minute mate". He then proceeds to pace in and out of my office door while finishing the phone call taking place on his hands-free kit; obviously helping someone get their Mac working again. It was the first time I'd seen someone using a hands-free kit in such a brazen and open manner. It was also the first time I ever saw Brad Watts.

Two years later Philip Spencer and I saunter out of an important meeting that secured the future of our yet-to-be-published magazine. It’s a beautiful Sydney day and we’re feeling as good as the weather, so we stop at Mo’s, the outdoor café belonging to the Museum of Sydney, for a celebratory drink. The attentive waitress is buzzing around wiping tables and keeping us well stocked with refreshments.
“By the way, my name’s Jackie. What are you guys celebrating?”
“We’ve just launched our new magazine, called AudioTechnology. It’s about sound recording equipment.”
“Really? My boyfriend writes about that kind of stuff. Maybe he could write for you…”
“What’s his name?”
“Watts is his name! Brad Watts, actually.”
“He’s in our first issue…”

Fast forward a few more years and I find myself sharing a warehouse conversion at the top of Hibernian House, Surry Hills, with newly-weds Brad and Jackie Watts. Crazy and intense days, in retrospect, littered with marine aquariums, astroturf, huge televisions and way too many fried chicken wings from the Thai takeaway down stairs. But we had a lot of fun. We both had our own studio rooms; Brad with the Quested VS2108s mentioned above (which he promptly bought after the review) and me with my ATCs. Between us, there was probably not a single piece of audio gear on the planet that we could not review the heck out of.

Brad's Mac Notes column has been a regular fixture in AudioTechnology since the first issue, along with his prolific product reviews. He's probably the smartest Mac audio guy on the planet. A year or two ago he became a full-time employee of AudioTechnology, a position he well deserved. To be honest, I don't know where the magazine would be without him...

FFW05: Choosing monitors

As I learnt more about sound engineering and got over the pathetic obsession with knob-twiddling and plug-in piddling that afflicts most engineers, I realised that the most important parts to get right were those that involved the interface with air: microphones and studio monitors. Although the correct placement of either may seem mysterious, its foundation lies in physics and there's really no mystery at all. More about that later...

This First Word, written in early 1999, offers simple advice for choosing studio monitors. A companion piece was published as First Word in AudioTechnology #07, and includes practical advice for setting up studio monitors (see 'FFW07: Lessons in coupling & isolation'). This stuff will always be relevant, although my recommendations of reference recordings may require updating...

Choosing Monitors
For our previous issue I took on the task of reviewing a pair of JBL’s new LSR32 studio monitors. I say ‘task’ because the review that appeared in the magazine was one of numerous versions I’d written in my attempts to explain precisely how good those monitors sounded, and who they would appeal to.

Reviewing monitors can be difficult, but deciding which monitors to buy is even harder. Magazine reviews can be helpful but they’re ultimately someone else’s opinion. Choosing the right monitors is like choosing prescription lenses without the help of an optometrist – the monitors that bring my hearing into focus may not work for you. So where do you start? Try the following approach:

(1) References
To test the overall accuracy and fidelity of monitors, you need a recording that contains nothing but real acoustic instruments recorded in real acoustic spaces, with no EQ or processing. A good pair of monitors will reproduce those instruments with a lifelike reality, from the attack of a xylophone to the end of a natural reverb tail. For this, you can’t go past a minimalist direct-to-stereo recording from a high fidelity audiophile label. I recommend The Ultimate Demonstration Disc from Chesky Records because it contains some truly excellent acoustic recordings, each highlighting a particular aspect of high fidelity performance, and each accompanied by a narrator explaining what to listen for - a real education and a great tune-up for your ears. (Don’t confuse this disc with The Ultimate Test CD from Essex Entertainment Inc., which is not recommended.)

While it’s important for a monitor to provide good high fidelity performance, you’ll also need to establish how it performs in a close-miked multitrack recording situation. Can it handle the repetitive ‘thud thud thud’ of a kick drum in solo mode? Or the challenging uncompressed attack of a raw snare? For those day-to-day studio sounds, it’s hard to go past Alan Parsons’ and Steven Court’s excellent Soundcheck 2 CD, which contains everything from drums and guitars through to strings and woodwinds; all recorded by one of the world’s leading sound engineers without any EQ or processing. Close-miked sound doesn’t get much better than this! Soundcheck 2 also contains numerous test and alignment tones and, like The Ultimate Demonstration Disc, has great educational value. (With a score of four, Soundcheck tops my list of ‘most stolen CDs’. Don’t leave it lying around when other engineers and recording musicians are present.)

For a personal context, you’ll need a well-recorded disc of the style of music you prefer to work with. Something recorded and mixed in a major studio by a top engineer, with good production values, is the requirement here. Every musical genre has a handful of top acts who use the best engineers in the best studios, and sometimes they release an album that is both musically and technically satisfying. That’s the kind of recording you’re after. For example: Quincy Jones’ Q’s Jook Joint (R&B/vocals); Metallica’s Black Album (heavy metal/rock); Yello’s Flag (electronic/dance); Garth Brooks’ Sevens (country/western); James Horner’s Glory (orchestral/film score).

Finally, you might want to take along a disc of something you’ve recorded and mixed, but only if you can be objective about it. If you’re a well-established engineer with numerous albums under your belt, that shouldn’t be a problem. But if you’ve spent less than 10 hours of your life listening to a professional mastering engineer telling you what’s wrong with your mixes, then you may find it hard to be objective. So if your recording sounds like crap while the others sound great, don’t blame the monitors. In fact, monitors that highlight the differences between your recordings and others are definitely worth considering.

(2) Familiarisation
Before auditioning any monitors you need to totally familiarise yourself with your reference discs, and the best way to do that is to carefully listen to them through headphones. I don’t advocate using headphones for mixing because they over-exaggerate the small details in a recording, but that’s exactly why they’re good for this process. Once you learn where those all-important little details exist in your reference discs – and what they sound like – you’ll find them much easier to focus on when listening without headphones. That’s a powerful skill for judging a monitors’ low level resolution and accuracy.

(3) Room Effect
You need to understand that no matter how good a pair of studio monitors are, the acoustics of the room itself will have a major impact on the sound you hear from them. For example, a good pair of monitors should have a ‘flat’ frequency response (±2dB or less) throughout their usable range, yet the room’s acoustic behaviour can cause deviations exceeding ±18dB! These effects vary depending on the dimensions and materials of the room itself, the locations of the monitors within the room, and your listening position. By the way, the notion that near-field monitoring overcomes these room problems is comforting but not totally correct.

(4) Use Before You Choose
People often choose studio monitors as if they’re choosing speakers for their hi-fi system, by playing some favourite CDs and buying the pair that sounds best. That approach overlooks one of the fundamental requirements of studio monitors, which is to monitor and mix. Before choosing a pair of monitors, you need to spend time recording and mixing on them, and playing those mixes through various systems to see how they translate to the real world. Remember, the goal is to find the monitors that work best in your studio, not necessarily in your hi-fi system. You also need to find out whether you can listen to a pair of monitors for extended time periods without suffering hearing fatigue.

Shooting it out…
Make a list of the monitors in your price range, find out where you can audition them, and book a quiet time to do so. Using your reference discs, make a shortlist of the monitors you prefer. Now, considering points (3) and (4), you need to get the shortlisted monitors into your studio before you can make a final decision. You need to experiment to find the right placement in your room, and you need to do some complete sessions on them. This is a crucial and unavoidable fact of buying monitors, and something that every responsible salesperson understands. You may have to pay a security deposit, but, whatever you do, don’t buy a pair of monitors until you’ve tried them in your studio.

For more monitoring information, see Michael Stavrou’s Mid Tuning Your Loudspeakers and my Strategic Monitoring, both in AudioTechnology #01. Remember that the right pair of monitors is the single most important and long-lasting investment in your sound recording future. So be methodical, avoid impulses, and listen carefully.


The closing paragraph of this First Word mentions Michael Stavrou, otherwise known as 'Stav'. He's somewhat of an engineering legend - in Australia, at least - and is also the brains behind the Smart AV console. I had always admired Stav's engineering abilities and insights, and wanted to include an interview with him in our premiere issue. I visited him in studios and I visited him at home, all the time snapping pics and keeping my Sony ProWalkman in record mode in the hope of capturing some pearls of wisdom. But they just weren't forthcoming; although being highly obliging, he seemed reluctant to talk and the interview was going nowhere. Eventually he confessed that he didn't want to give too much away in an interview because he was planning on writing a book. I suggested that writing a regular column for the magazine would be a good way to get the book started: it would force him to write a regular installment every two months, it would prime readers for his forthcoming book, and the columns themselves could be considered as first drafts for the book. Fortunately he agreed, and thus was born the regular column Stav's Word - a wonderful part of AudioTechnology, full of great advice and unusual ways of thinking about sound engineering. Stav published his book, Mixing With Your Mind, a few years ago, and it has been a hot seller ever since. And it all started with a frustrated attempt at an interview...