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10 ways to remove the room with EQ

  • During last week’s video interview with Berlin-based studio acoustician Jesco Lohan, he listed three big wins in his battle against the negative influence of the room over a loudspeaker system: 1) speaker/couch placement; 2) the installation of numerous absorbers, diffusers and bass traps; and 3) Equalisation (aka EQ).

    For the majority of readers, domestic harmony will immediately strike number 2 from the list and number 1 was probably set in stone a long time ago — although a revisit couldn’t hurt.

    That leaves number 3 as the remaining weapon of choice in our war against modes and reflections. EQ in the 21st century is often executed in the digital domain. For audiophiles listening at home, that often translates to a software application running on a PC or Mac; or dedicated code – digital signal processing (DSP) – running on a chip inside a piece of audio hardware.

    I’ve not experienced all that is out there to be tried and neither have I gone too deep. Consider this a surface skim (and not an exhaustive list) of EQ applications and devices that might bring you one step close to audio nirvana, with the caveat that EQ isn’t a magic bullet and won’t ever strip away all of the room’s ills. However, it can make a significant improvement to the listening experience.

    ONE

    In addition to calculating troublesome room modes, another relatively easy starting point in getting to know how your room – and how it is affecting the sound of your loudspeakers’ output – is to measure the loudspeakers’ in-room frequency response at (and around) the listening position. REW (Room EQ Wizard) is a free download for Windows, MacOS or Linux. Setup and signal routing is as easy as 1-2-3:

    1. Install REW
    2. Connect a room measurement microphone (like the UMIK-1) to the host PC or Mac’s audio input.
    3. Route the Mac or PC’s audio output to the loudspeaker system

    We are now ready for REW to run frequency sweeps that it will immediately capture via the microphone before graphing the in-room frequency response of our loudspeakers; in an untreated room, the results will be a long way from the loudspeakers’ anechoic chamber measurements.

    We can then make adjustments using our playback software’s DSP-powered parametric EQ capabilities.

    Roon’s parametric EQ allows us to tweak the frequency response at the server level so that it calculates and sends any user-specified frequency adjustments to the streaming endpoint. If REW shows us a bump, we might try to counteract it in Roon’s PEQ with a corresponding dip. REW room measurements can also be exported as a correction filter file and then imported directly into Roon. All of Roon’s playback zones (endpoints) are independently configurable.

    Parametric EQ adjustments can also be applied to the output of Audirvana, JRiver and many other leading music playback apps. Hans Beekhuyzen takes a closer look in his video:

     

    TWO

    What if a measure-and-correct process could be automated within a single app? Standalone room correction software like Dirac Live, measures the loudspeaker’s in-room response and then automatically calculates a target curve and correction filters than can be dis/engaged with a single click for instant A/B testing.

    The Finnish company explains: “Using a microphone to analyze the audio system and room, the audio calibration software uses this data to build an acoustic model of the listening environment and detects the deficiencies.”

    “By using mixed-phase correction we can enable impulse response correction. A loudspeaker’s impulse response affects staging, clarity, detail and all spatial aspects of the sound. Dirac Live® is unique in that it improves the impulse response throughout the listening area, not just in a particular zone. The Dirac Live® algorithm suggests a target response appropriate for your listening environment and speakers, which you can, of course, adjust to your taste using our simple graphical interface.”

    However, Dirac Live as a standalone Windows or MacOS app is no longer available.

    THREE

    In recent years, Dirac has begun licensing their room correction software smarts to high-end audio manufacturers. Dirac Live functionality shows up in the NAD M10 integrated amplifier, the NAD C658 streaming DAC and Arcam’s SR250 stereo receiver.

    This opens the door to a more simplified configuration process via Dirac’s smartphone app:

    FOUR

    For a standalone Windows/MacOS app we look to Latvia where Sonarworks’ Reference 4 “removes unwanted colouration from studio speakers”. The app guides the end-user through the room measurement process in order to calculate a ‘calibration profile’ that corrects for (some of) the room’s negative influence.

    Interestingly, Reference 4 creates a virtual sound device on the host PC or Mac and additionally integrates with DAWs and music playback software apps that support AU, VST and AAX plug-ins.

    FIVE

    Dirac-in-a-box isn’t the hardware to house room correction smarts.

    DEQX (“decks”) makes digital pre-amplifiers that offer an Australian take on room-correcting maths. But not only. The DEQX units additionally feature loudspeaker correction smarts. https://www.deqx.com/products/

    And like the Dirac-injected Arcam SR250, every DEQX box sports analogue inputs to open the door to turntablists, reminding us that room correction isn’t only for those who stream.

     

    SIX

    Industry legend Peter Lyngdorf reportedly looked at the standard procedure for room correction – 1) measure in and around the listening position, 2) calculate the target curve 3) apply required filters using DSP – to discover that there might be a better way to remove the room’s negative influence.

    Lyngdorf’s RoomPerfect calibration process involves taking a single measurement at the listening position to ascertain the loudspeaker’s properties and then a number of more random measurements throughout the room to help better identify why the loudspeakers sound as they do at the listening position.

    And that RoomPerfect tech can be found in the Lyngdorf TDAI-3400 and TDAI-2170 integrated amplifiers.

    SEVEN

    Active loudspeaker manufacturer Genelec takes this in-built thinking one step further by installing in-house coded corrections inside their SAM-enabled active loudspeakers. SAM? ‘Smart Active Monitor’.

    “Controlled by the proprietary Genelec Loudspeaker Manager (GLM™) software, SAM Compact systems use ground-breaking AutoCal™ to create an optimised and controlled monitoring environment. After automatic calibration, monitoring set-ups ranging from simple stereo to immersive audio will perform with the consistency upon which you rely, compensating for deficiencies in the listening environment.”

    The AutoCal app (Windows, MacOS) talks to the GLM adapter, which in turn handles microphone room readings and loads the final calibrated response into the loudspeaker over an RJ45 interface. Storing the correction profile in the loudspeaker ensures source agnosticism: analogue or digital; vinyl or streaming.

    Before we even get to GLM and SAM, we can adjust the Genelec speaker’s output according to boundary proximity. The rule of thumb goes like this: putting a loudspeaker close to the front wall will add 3dB of gain; putting it in a corner will add another 3dB. Rear panel dip switches for bass tilt and roll-off, executed in DSP, help us counteract this boundary gain. Treble trim allows us to tailor to the top-end according to the room’s reverb levels.

    The calibrated (parametric) EQ is tweakable, with options to store multiple profiles. It can also be switched in and out with one click.

    EIGHT

    Boundary gain compensation switching isn’t exclusive to Genelec monitors. We also find boundary compensation switches on the back of active loudspeakers made by the likes of Dynaudio and ELAC.

    KEF have put boundary gain compensation in their LS50 Wireless and LSX actives but instead of hardware controls, the partnering KEF Control smartphone app (Android, iOS) talks over the host network to the loudspeakers’ internal DSP, adjusting their output according to user-specified placement (stand or desk), front wall proximity, desk edge proximity, room size and acoustic make-up. The app’s ‘Expert’ mode rewrites this beginner-friendly terminology as treble trim, bass extension, ‘wall mode’ and offers optional phase correction.

    NINE

    To design their room agnostic ‘Three’ standmount loudspeaker, Kii Audio tapped the talents of Bruno Putzeys who coded the DSP engine so that the 2 x side-firing drivers and 2 x rear-firing shaped the otherwise omni-directional dispersion of lower frequencies into a cardioid pattern — far less troubling to front and rear walls whose first reflections bounce back into the room to create all sorts of invisible havoc. No user interaction required. Almost. Below 50Hz, boundary compensation is available via the back panel or the Kii Remote. The result? A loudspeaker that sounds as good at home as it does at the store or at a show.

    TEN

    Like the Kii, the Dutch & Dutch 8c loudspeaker (see feature image) delivers a degree of room agnosticism out of the box. Unlike Kii, the 8c’s low-frequency cardioid dispersion pattern isn’t digitally but acoustically: the 8c’s side vents re-route the internal back wave of the front-firing midrange driver to cancel out sound wrapping around the cabinet; sound that would otherwise head to the side or front walls.

    The 8c’s room cognisance doesn’t end there. Each loudspeaker contains a small network-accessible computer which accommodates parametric EQ via a web interface. After measuring each loudspeaker’s in-room frequency response with REW, we input the frequency of each troublesome hump, its downward dB adjustment and a (Q) width via a web interface…and then re-measure, repeating the process if necessary.

    And REW is where we came in: measuring and then manually applying corrective EQ, only this time, adjustments are stored inside the loudspeaker for proper source agnosticism. The improvement is nothing short of revelatory.

    What happens next falls to you.

    John H. Darko

    Written by John H. Darko

    John is the editor of Darko.Audio, from whose ad revenues he derives an income. He is an occasional contributor to 6moons but has previously written pieces for TONEAudio, AudioStream and Stereophile. John used to live in Sydney. Now he lives in Berlin.

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