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Can room correction software improve the ‘sound’ of a listening room?

  • A man with a transit van. That’s how I moved a few key pieces of furniture, some basic filming equipment, several security cameras and selected hi-fi components from Berlin to Lisbon in very early January. (I was to greet its arrival two days after it left but my right eye delayed my outbound flight by three weeks). With van space at a premium, I had to be choosy. And quickly. The Zu Soul 6 were a non-negotiable as I was near-certain that their deep red gloss finish would look super smart once set down on the Lisbon apartment’s black and white tiled floor. I was not wrong. That big box choice then meant that the rest would have to be smaller pieces: KEF LSX II + stands, Sonus faber Lumina II, Technics SL-1210GR, Buchardt A500, Meze 109 Pro, Rosson RAD-0, Chord Hugo 2 + 2go, RME ADI-2 DAC FS, iFi Zen Streamer and Enleum AMP-23R. Unwittingly, I had put together a collection of Kallax-Fi for its new life in Portugal.

    With the world’s most popular vinyl storage system on my mind, I also had to choose which room correction-capable amplifier would make the 3000km road trip southwest: the Lyngdorf TDAI-1120 with Room Perfect or the NAD M10 V2 with Dirac Live? RoomPerfect makes lighter work of pulling a subwoofer into the room-corrected frame but the NAD has a large colour display and delivers a fatter, punchier sound to make it better suited to a broader range of loudspeakers. Furthermore, already knowing that two subwoofers from GoldedEar were about to come down the pike, the Canadian shoebox amplifier got the nod.

    In a recent post, we established that the midrange and high-frequency reverb time (RT60), as measured at the listening position in my 4m x 7m Lisbon listening room, clocks in at an average of one second. That amount of reverb, clearly audible in both hand clap and voice recording tests, is far higher than the amount recommended by acoustic professionals: between 0.3 seconds and 0.7 seconds from 300Hz to 4kHz.

    And whilst we didn’t completely disprove the acoustic utility of a rug in that previous post, we poured cold water on the audiophile community thinking that conflates the addition of a rug (and assorted heavy furniture) with proper room treatment. Your grandfather’s Winchester is not a bass trap and his footstool is not a Helmholtz resonator.

    A decent-sounding room is an essential tool for anyone professionally assessing high-performance audio equipment. For yours truly, it goes further still. Having lived with a complete Vicoustic fit-out for the past 18 months in Berlin, I knew before flying out to Lisbon that I couldn’t go without in the new place. Having since measured the room’s RT60 in the seat, I’m glad I took the time to tee up the room’s professional treatment before I left Germany.

    In any other country, I’d have looked to another acoustic panel manufacturer so as not to not play favourites. But Vicoustic is a Portuguese company, its headquarters a mere 20-minute drive from my new home. I sent them the architectural plans of my Lisbon apartment plus the specifics of the wall materials (plasterboard fronting masonry) and the floor (tiled). The non-parallel front and rear walls would work acoustically in my favour. Two weeks later I had a proposal document containing 3D renders of the room’s planned fit-out, as seen from several angles. Installation day was booked for two weeks after wheels down.

    Moving in, sorting an Internet connection, numerous shopping trips for the bare essentials and my failed rug test (and its two accompanying videos) ate an entire week. That left only a two-day window for me to investigate what room correction software from Buchardt and Dirac (via NAD) could do – if anything – for the room’s overly long reverb time.

    Per attitudes towards rugs and sofas, some corners of the audiophile community had room correction software pegged as a one-for-one substitute for professional acoustic treatment; a software stand-in for when the aesthetic make-up of a room cannot be messed with. Could the power of DSP really allow the hifi-loving minimalist or ‘WAF’-wielding boomer (😉) to have his cake and eat it?

    The Buchardt A500’s accompanying Platin Hub asks us to wave an iPhone around the room, covering corners and walls, as its microphone reads 90 seconds of test signal pushed to the Danish standmounts over a low-latency WISA connection. The smartphone app then analyses the iPhone’s reading to offer up a corrected output curve for the loudspeakers that would, in theory, optimise their in-room performance.

    I did this then I put a UMIK-1 measurement microphone at the listening position and connected it via USB to an M1 MacBook Pro running Room EQ Wizard (REW) which in turn was USB-connected to the Platin hub. The room correction (RC) curve could be turned on and off with a single click (inside the app) to make light work of taking an RT60 measurement with the room correction off and then on:

    To better understand one major reason why the Platin hub’s room correction software makes zero difference to the RT60 (between 300Hz and 4kHz), we must look at the frequency response (FR) graph where we note an uplift in the lower frequencies. The room correction software wants the A500 to push more low-end into the room but that’s not our focus here.

    What is then? Look at where the lines begin to diverge. The Buchardt/Platin room correction software targets only frequencies below 350Hz. An email to Mads Buchardt confirmed as much. That the following smartphone app screenshot shows something seriously amiss with the room correcting app’s frequency response analysis of my room – later determined to be a faulty Platin hub – makes not a jot of difference to today’s findings. The takeaway here is that the Buchardt/Platin room correction system targets only bass and changes nothing above 350Hz: not the frequency response and especially not the RT60.

    The LE version of Dirac Live that ships with the NAD M10 V2 suffers a similar fate. It is hard-curtained at 500Hz to make its correction a bass-only deal. A one-time payment of $99 drops the LE and its 500Hz curtain to give us full frequency response correction (20Hz to 20kHz) and an editable correction curve. I upgraded some years back so up next was a phone call to professional Dirac Live installer Terry Ellis to ensure that no mistakes would creep into the Dirac Live measurement process. The loudspeakers being driven by the NAD integrated were the Zu Soul 6.

    Like the Buchardt room correction system, Dirac takes data from multiple microphone positions. Our five UMIK 1 microphone measurements netted the following frequency response and a default correction curve – the straight line that runs through it – that we elected not to edit before pushing it over the air to the NAD M10 V2.

    With REW back in the driving seat, here we see the in-room frequency response of the Zu Soul 6 with Dirac Live off and on. Notice how Dirac Live has smoothed the Zu’s in-room response. Nice! What this measurement doesn’t capture however is how Dirac Live nudges the phantom centre image into (better) focus. Zu’s Sean Casey would probably prefer I call this ‘superior stereophony’.

    And yet the room’s long reverb tail remains unmistakably audible. That rubber meets the road when we look at the midrange and treble’s RT60 with Dirac Live off and on. The NAD’s room correction smarts fail to reduce the reverb times of frequencies above 600Hz and slightly worsen ’em below that point:

    Can room correction software improve the ‘sound’ of a listening room? Yes. But also no. Software like Dirac Live obviously controls the loudspeaker’s output – we can hear it and we see it in REW’s frequency response graphs. And from my limited understanding, it has the potential to heal some time domain issues – albeit to a lesser extent.

    However, room correction software appears to have next-to-no control over sounds that have already left the loudspeaker to snooker around the room. How could we reasonably expect anything else? Even if the DSP were to delay some frequencies, they too would reverberate around the room after leaving the loudspeaker (just a little later).

    Our conclusion then for today: nothing that I have measured here with REW – and nothing that I have heard during music playback – suggests that room correction software can meaningfully improve a long room reverb time in the all-important region between 300Hz and 4kHz.

    That means all the heavy lifting now falls to Vicoustic…

    Written by John

    John currently lives in Berlin where he creates videos and podcasts for Darko.Audio. He has previously contributed to 6moons, TONEAudio, AudioStream and Stereophile.

    Darko.Audio is a member of EISA.

    Follow John on YouTube or Instagram

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