John Darko
Denial – as the saying goes – isn’t just a river in Egypt. It’s a state of being. For our kind, denial most often takes root among the things we cannot change: that more costly speaker cables (that we cannot afford) will sound better than the pair currently in play; or that a more luxurious amplifier (that we cannot afford) will convincingly outperform our current choice. Never mind that we’ve demoed neither, our perception has been steered by behavioural psychology long before any measurements have been taken or our rear end has hit the listening chair. Instead, some of us wrestle internally with arguments of diminishing marginal returns to reframe personally attainable hardware choices as being at least 90% as good as spendier solutions, irrespective of the reality.
Chief among the denial-infested immovables is the listening room. In most households, the room that plays music must also serve as a TV room and an entertainment area. We must consider (significant) others before we consider acoustic treatment. Right on cue, denial enters the chat.
We know that too much room reverb(eration) in the midrange and treble is a problem. Sound leaves our loudspeakers and it goes straight to our ears. But only some of it. The rest fires off-axis to hit walls, ceiling and floor before snookering around the room as it decays. Each reflection point removes energy to make any onward-travelling sound quieter. Reflected sound mixes with the direct sound at the listening position but as late, distorted arrivals. Ten of thousands of reflections decaying over time all contribute to the room’s ‘sound’. The longer the decay time, the worse the reverb problem. The better the reverb situation, the shorter the decay time.
This why recording studios and professional listening rooms are acoustically treated with wall, ceiling and freestanding panels that absorb and diffuse (scatter) sound that would otherwise reflect. This is why I had my office in Portugal treated at the end of December. If I want to use the office to review loudspeakers or upstream electronics, I can’t risk the room colouring the sound and – perhaps – my opinion.
An RT60 graph formalises the state of play at the listening position. It shows us how long it takes for each frequency to drop by 60dB. The lower and more consistent the RT60 score at each frequency, the better sounding the room. Here is my office’s reverberant behaviour in the midrange and the treble, as measured by a Umik-1 microphone and Room EQ Wizard, before any treatments were installed:
As you can see from the graph, my room’s reverb started at 700ms at 300Hz before rising to over one second at 800Hz. Not good. Not good at all. Acoustics professionals generally agree that a listening room’s reverb time should sit somewhere between 300ms and 600ms between 300Hz and 4kHz.
Why not aim for 0 – 100ms? We still want to retain a little reverb to avoid the room sounding overly damped. And here is my office, measured with the same microphone at the same listening position but post-op:
With the panels installed, the office’s reverb time hovers between 300ms and 400ms — right on target. And boy, can we hear the difference. See this video for examples.
Regular readers will recall that I had my lounge room treated in early 2023 with similarly jaw-dropping results:
The lounge remains a little more reverberant than the office but still well within bounds at 400ms – 500ms. Now we ask: why is that when both rooms’ floor dimensions are identical and the ceiling in the office slopes steeply to one side?
At each end of the lounge listening room sits a hallway and staircase which send late reflections back into the periphery of the listening zone, which I’ve visually bounded with a rug and couch. It’s at that periphery, and talking away from the listening zone, I often film the talking head portions of my videos. Listen to those videos with a nice pair of headphones and you will hear the presence of late reflections because I am talking towards one of those hallways. Thankfully, those later-arriving reflections are far, far less audible when sat in the listening position. The reverberant hallways will need to be sorted eventually but this year, the office’s acoustic treatment took precedence.
My Vicoustic contact tells me that some of the most challenging listening spaces are lounge rooms that open out into larger, adjacent reverberant zones like dining areas and kitchens. The additional room volume lowers the incidence of bass resonances but the walls still contribute to strong late/r reflections. Only by treating the entire space – including the ceiling – will its reverberant behaviour in the mids and highs be properly tackled.
Those living close to a river in Egypt will see my thoughts on this matter – or the plethora of acoustically treated rooms on forums and Facebook groups – and reason with themselves that the carpet on the floor in their room, along with the shelving system that sits behind their couch and the picture frames that adorn the front wall (behind the speakers) and numerous houseplants are ‘just as good’. “It’s not rocket science!” they internally exclaim.
In the majority of cases, they could not be more wrong. And I know this because I too used to think that way — but that was before I compared a full acoustic fit-out to my pre-existing furniture. My experiential shortfall caused me a severe case of the Dunning-Krügers in which I’d reached for the denial that pegged my regular furniture plus some judiciously placed wall panels as 90% as good as a full acoustic fit-out; and German food as 90% as tasty as Spanish. After all, if we’ve never been to Spain, our opinion of its food will be far less reliable than the opinion of someone who has lived there for three years.
I now know both not to be true. I’ve been to Spain at least three times and I’ve spent 2.5 years living with – and in – an acoustically treated listening room in Berlin. That room’s makeover was my first. Before Vicoustic came in to treat it properly, I had heavy rugs covering 80% of its 6m x 5m wood-on-concrete floor, a sofa (at one time TWO sofas), a trio of 1 x 4 IKEA Kallax towers stacked with vinyl in three corners but also four GIK diffuser/absorber acoustic panels on the front and side walls and GIK bass traps running along the opposite side wall.
Yes, the furniture, rugs and GIK panels sounded better than the empty room but their collective impact did not come close to the sound of the fully-treated room, which notably went where regular furniture rarely goes: the ceiling. The ceiling is just as reflective as the floor.
Denial also blinds us to how a rug’s absorption coefficient generally doesn’t come on song until at least 1kHz and that the absorptive behaviour of our couch, media console, shelving and houseplants are total unknowns. Between getting the keys to a new house and filling the lounge room with furniture we hear a small improvement in the room’s reverberant behaviour, usually in the uppermost treble above 3kHz. However, this kind of audible improvement rarely means that all reverb problems are solved.
Anecdotally speaking, any furniture-related betterment is dwarfed by a full acoustic fit out. I don’t have an RT60 graph of my Berlin apartment with the furniture and GIK panels still in place but I do have the next best thing. In 2022 we saw how my next-door neighbour’s lounge room, the mirror image of my own, was decked out with a huge couch (far larger than my own), an L of 2m high shelves filled with books occupying one corner, a TV bench and houseplants.
Not only did my neighbour’s room sound reverberant but the measurement revealed an RT60 average of 700 – 800ms, which isn’t much higher than the upper bound of our 300ms – 600ms target. The room sounded worse than that suggested by the RT60 average because the RT60 values moved wildly with frequency. A better-sounding room not only displays a lower RT60 but a more consistently lower RT60.
Since my Berlin-based Vicoustic fitout, the hi-fi rack that previously sat between the speakers has given way to a mid-century modern sideboard (from Tikamoon) – with the electronics moved to smaller hi-fi racks sitting at the back of the room – and the record collection relocated upstairs to make way for nine IKEA GNEDBY CD towers.
Here’s the RT60 graph for the Berlin apartment as it stands now:
Notice how the RT60 hovers between 200ms and 300ms, nudging it closer to a recording studio’s target of 100ms to 200ms. Unlike our furniture, a wall- or ceiling-mounted panel’s acoustic behaviour is known and, therefore, predictable. Acoustic panels purchased from reputable manufacturers are supplied with data on their absorptive characteristics.
DIYers can go it alone for less, paying with time instead of cash. But isn’t time also money?
I’ve treated three rooms in the past three years. I could never go back to listening in a non-treated room. And there’ll be a fourth if I move house again. For me, the result is worth the aesthetic intrusion. However, we should note that if the difficulty in solving a room’s reverb problems isn’t the best argument for headphone listening and/or staying single, I don’t know what is. After all, it’s not rocket science.
