Critical Podcast Episode 1 Script — The Rooms We Listen In

Welcome friends. This is new for us all — new systems to do it on and learn how to operate. We are new as co-hosts with very different backgrounds that we hope will add to the discussions and the dynamics here. My name is Sarel, and I’m joined by our co-host William, publisher of AV News.

E1: Rooms

Some housekeeping first.

There is a whole host of topics we are planning to cover, starting with our rooms used to listen in. Next episode we plan to cover both hearing and a bit of listening. Your input, suggestions and feedback is greatly appreciated, both positive or not. This is for the audiophile community and your suggestions and contributions will make this podcast yours. We will publish links to the podcasts and upload to Youtube and Vimeo as well.

Arguably the room is the most important single part of enjoying being an audiophile: critical listening happens indoors, almost without exception.

 

Side note: High fidelity is only related to reproduction of previously recorded materials as musical instruments, and voices are always high fidelity.

Fun fact on harmonics: https://www.puremix.net/blog/musical-instruments.html

 

It’s complicated and it depends on the musical instrument what type of frequency dominates — fundamental versus 2nd or 3rd (really even and odd) harmonics. The human voice is even more complex.

Let’s now look at where the energy in music is — the lower octaves in smaller rooms are the most problematic. A Fender electric bass playing a low A note, in the spectrum below (55 Hz). It is clear that the fundamental note is softer than its first two harmonics. There is more energy in the second and third harmonics than in the others. Bass instruments sound full due to their second harmonic.

This is the same note on a Yamaha Grand. As is clearly visible when comparing these two, the harmonic content is vastly different, as well as the rate of decay.

Back to your room: most listening rooms are not custom and bespoke designs, and even if they were, there are always real world compromises. It is a well-known and accepted fact that the room influences the sound; some are bright, some noisy or others dead. At the lower octaves in particular, the room will dominate the reproduced sounds (Specifically the most troublesome octaves in small rooms, normally below about 400 Hz). Smaller rooms are more problematic wrt the lower octaves that cause nulls or dips (and peaks) and these alter the sound we hear.

A random room at say 6 m in length (small from a sound wavelength perspective), would correspond to fitting a full single wavelength at about a 56 Hz frequency. Shorter lengths = higher in frequency. The first room mode then corresponds with the longest dimension of the room and here at 6 m is 56 Hz.

The smaller the room, the more it will need treatment and careful placement of speakers. Also the listening position is more critical for its placement.

This picture shows the non-linearity of what we listen to. It is important to visualise that far more energy is contained in the middle to lower octaves from a pressure wave perspective.

 

A piano only plays notes to just above 4000 Hz!  These are the fundamental notes. There are overtones much higher up in frequency. The following table shows the lower octave wavelengths, too:

 

We need a room that is at least 17 m long to reproduce a full wave at 20 Hz. This does not mean we cannot reproduce 20 Hz in smaller rooms, just that there are more compromises.

Above that 56 Hz frequency, multiples of this frequency will form standing waves with modes all over in length, width and height. These are the worst for lower octaves, and most of that energy will bounce from the back wall and caused nulls and peaks all over, frequency depending.

This picture shows a representation of a null and nodes, etc. Remember this works in all three dimensions.

The only way to deal with this in an existing room, is to use treatment. Absorption lowers peaks and that in turn reduces nulls in response. This ends up with a flatter response. It does not reduce overall base response, as most of the energy lost in the dead areas were cancellation of energy waves. Now peaks are lower, so with less energy, but at the same time nulls are less as well, equalising the energy. We will come back to more in depth acoustics and room treatments in a later episode.

Think about this, what is the most expensive component of your system? Take a moment to consider that and then realise it’s your room (well house), but you cannot separate them. The room structure, for most of us, is more expensive than the system in it. Of course there are exceptions to this, but in general.

Also the room is the biggest single component. Yes, think of it as a component of your system, that influences the sound produced there, its influence even larger than that of the speakers. Think for a moment, about changing the room itself, the size or its structure or the type of materials the walls are made of (Materials reflectivity is a touchy subject…Reality however is that sound reflectivity is frequency dependent and not that variable).

Materials reflectivity for the types rooms are made out of varies with less than 1 dB between materials normally, so it’s not easy to hear the difference when music is played there. A huge, absolutely huge change on how the same system and music will sound will take place if the room size or relative dimensions are changed — even if the volume of it stays the same. And that my friend is the importance of the room on what we hear when listening critically.

It’s kind of a chicken and egg situation, as we need something to listen to in the room to assess the room itself. There are two ways we can assess a room: by listening and by measuring. In the past, to measure our room was expensive. No longer so today.

The only objective way to do the assessment is to test. Listening is subjective and you cannot do calculations by guessing frequencies. Our memories are not all that good for comparing sounds in a room in any case. Some people, however, do exactly this and do not measure. We are not here to convince them otherwise, but merely to share information.

Think of this: we cannot manage nor improve what we cannot measure and quantify. The rest is really subjective. Nothing wrong with subjectivity, but quantifying that is sort of difficult as it will differ from person to person.

What may make a room a bad room, or a good one? A cube, or very close to a cube is bad. Any room where the ratios are multiples between length, width and height, are not good. The smaller the room, the more difficult to reproduce balanced sounds inside it.

 

Fun fact: room correction software does not fix acoustic problems of the room. It has its place, but is fit for purpose fixing timing and other issues … but not room acoustics.

A good room, some say, is built with the golden ratio. Rooms with alcoves or with an L shape are common, and normally perfectly acceptable. We have to work with what we have.

 

So now the room has doors and windows and some skylights, too. We mentioned noise inside a room — that is outside noise penetrating to the inside and the other way around also. This is called isolation, or the lack of noise control. We need some of that for obvious reasons.

Bass frequencies are the problem children of audio. It’s difficult to control because the room has the biggest impact on them. We need mass and thickness to achieve isolation. But, instead of keeping the bass in and attempting to tame it, we can use the windows strategically to allow the bass to escape and not be reflected. Windows, normally single pane, on the front and or back walls may help tremendously with this.

Ponder on these things for a moment and we will deal with them again in a later episode. The room influences sound reproduction tremendously. Treatment and intelligent use of absorbers and diffusers in such treatments are vital. On this there is what I refer to as the ABC of room treatment. A Bridge and Cloud. Let me explain.

Between the listening position and the speakers, there are walls to the sides and a ceiling above. It’s important that the speakers be equi-distant from the side walls to prevent relative delays; this timing difference between left and right delays will interfere with our hearing of the original sound by creating masking effects and what could be perceived as reduced clarity. The walls reflect the directly radiated sound and that sound arrives later at our ears than the direct path sounds. We want to eliminate those reflections to improve the sound quality and clarity. These side positions are part of the bridge.

At about the same place more or less above on the ceiling, there is another reflection point that does the same. We want to reduce that too, and it is called a Cloud when we affix absorbers there. Between the side absorbers and the Cloud absorbers we get the ABC, a Bridge of absorption passing from one side via the Cloud to the other side, improving sound quality and clarity.

Wait, what about the floor then? We and our brains use floor reflections as location beacons almost constantly. Everywhere we go we have reflections from below our feet. Removing those have a rather large influence on perceiving sound location, and in music listening , floor reflections form a large part of sound staging and placing voices and instruments where they belong. If you have a loose carpet there, try and remove that and test. Fully carpeted floors may be problematic for the best in critical listening. We depend on better reflections than that, and are used to such. A dead floor will sound not natural.

Let me leave you with this — we are not going to be able to talk about everything in one session but there will be more. The chain from source to amp is far more accurate at -2 dB 40 Hz to -3 dB at 20 kHz than your speaker. All the components, including your speakers, are way more flat in response than your room allows: the room dominates.

If you don’t believe this, then drag your system to the garden and have a listen there. Let us know the outcome please, send pictures too… It is frequent that we see dips of 20-40 dB in room response, see the forest for the trees, be as objective as we can be for the pleasure of critical listening. Do not fret about the 3 dB issue in the speaker or amp frequency plot, when we have a bad room… focus on the room. As the saying goes, It’s about the room, stupid!

Do not let biases or dogma or myths make you lose the forest. Critical thinking, and listening, is required for best enjoyment with least money spent.

Next time on the critical video podcast is E2 on ears and listening, or more specifically, sound perception.