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Author: Mark Wheeler - TNT-Audio UK
Published: December, 2024

Is This Where I Get Felt?

“The Old Scribe starts with a dreadful pun that only works in English,” accuse plebs chorus, stage left, “And then only for readers of a puerile nature”

This is an article I've been meaning to write for many years. Your Old Scribe has been making, researching, remaking and measuring acoustic art for 30 years in the quest to make pleasantly inhabitable living rooms that also double as audiophile listening rooms. Many of us have separate listening rooms filled with audiophile junk and treated with diffusers and absorbers on walls and ceilings into which we retreat from family life to the sanctity of deafening music. This does not suit everyone, not everyone can afford to devote that much of the household acreage to audio alone and your Old Scribe actually wants to share the experience of listening to music. For those of us who also need a darkroom, a classic vehicle workshop and an office, a room dedicated to hi-fi seems just plain greedy. Hence there is a place for domestically acceptable acoustic arrangements. Therefore it seems a bit tardy to be writing this introduction after owning 4 listening rooms over 30 years that have been the vehicles for experiments in unobtrusive, aesthetically pleasing even, acoustic interventions of the arty, stylish or just plain pretentious type.

Like everything else, especially all things audio, context is everything.

• The shape of the room
• The materials from which the room is constructed
• The furniture in the room
• The spatial and positional constraints of the room
• The dispersion patterns of the loudspeakers

The latter is in some ways the most important when it comes to fine tuning, especially with art works, but all 5 of these characteristics are equally important to begin with. The transitions between drivers in multi-way loudspeakers often create dramatic differences in dispersion from one octave to the next. The wider dispersion of the smaller driver means that its output bounces around the room far more than the upper frequencies handled by the driver below. Two-way and three-way loudspeakers with a transition to high frequency drivers at around 2kHz therefore create a specific problem with reflections causing comb filtering and other phase anomalies.

Writing this first article was prompted by a visit to “Entangled”, a special exhibition of work from the International Felt Maker's Association Region 10, at Leeds Industrial Museum. Just as your Old Scribe automatically observes almost any object for it's potential as a loudspeaker enclosure, art works are also automatically evaluated for their potential as decorative acoustic treatments. The works in this show of felt-making fine art would work beautifully contributing to the improved clarity and intelligibility of speech and audio in any enclosed space.

Audiophile Outsider Art

Another interesting art show at Leeds was the The Traumatic Surreal, at The Henry Moore Institute (until 16th March 2025), Leeds. Your Old Scribe might easily have responded to latter same show if it had been entitled “Outsider Art Comes Inside”, which is important to us here. “Outsider Art” is the art made outside of artistic traditions and institutions. Many famous artists were initially rejected by the galleries and salons of their day, some joining in “Salons des refuses” and others admitted to the establishment later in their careers as the establishment gradually or grudgingly accepted their innovation. Your efforts at acoustic art may therefore one day be accepted into the Royal Academy Summer Show leading to a change in career.

Apart from those TNT-Audio readers who have careers as exhibiting artists and are represented by agents and galleries, art that we make and display in our listening rooms is therefore outsider art and subject only to our own rules. Therefore rules which include acoustic aesthetics are just as valid as visual aesthetics.

Examples from the “Entangled” show

Any glazed framed art work acts as a specular reflector of light and sound. Therefore only the unglazed of the framed works are shown here, together with examples of felt makers' sculptures. The latter have particular advantages in audiophile spaces. The additional depth of bas relief felt images or 3d sculptures lowers the frequencies above which the felt art is effective. “Return of The Carpet Beetle” by Linda Hume is a wonderful example of a 3d art work in felt that would be ideal audio room fodder without the carpets becoming beetle fodder. Magnified from life by over 250 times, resulting in a wide-band absorbent object over 50cm across and 30cm deep, this would make a perfect bass absorber on an antinode at the ceiling, wall or floor.

Your Mental Health and Art in the Home

Numerous authors and researchers have argued for the mental health benefits of art in the home. There is even more evidence for making art ourselves. Making ceramics has special effects on our wellbeing, arising especially from the haptic qualities of clay. Home made ceramics tend to have rough surfaces that can diffuse the highest frequencies and therefore reduce the comb filtering that can affect instrumental timbre and spatial information in audio signals. Soft toy making is particularly satisfying, and Ethan Weiner, the explicitly objectivist “Audio Expert” has several large soft toys in his listening room and attributes the reported revelatory experiences of many audiophool reviewers as arising from subtle changes of position in poorly treated rooms and of comb filter effects. Comb filter effects are exactly the domain of amelioration by soft toys and felt art works. Felting is an increasingly popular craft activity available via taught workshops and felt art works can be bought ready made on the usual arty online sales sites. Your Old Scribe, wearing his Art Therapist hat, would obviously prefer that you and your family make your own art.

Hence you and the creative members of your family can make unique pieces of art, perfectly adapted to the specific requirements of a certain position on the listening room wall. Mixed media pieces have special adaptability to the acoustic requirements of critical positions in the listening room. For example an art work can combine areas of quadratic diffuser with areas of absorber. Both of these will be defined in their effects by size and depth of your masterpiece.

“Isn't it bad enough having the kid's art on the fridge door, let alone our own on the listening room walls?” Whine those plebs with 'House Beautiful' subscriptions

Your Room and Acoustic Art

Two things matter in your living room that doubles as your audio room. The first is the overall frequency response of the room-loudspeaker interface. This will be the subject of other articles about room shape, loudspeaker positioning and explicit acoustic treatment, usually in corners. The other aspect of the room is intelligibility. This is mostly influenced by the behaviour of sound waves at the air-solid interfaces in the room. This affects how well we can pick out individual musical contributions from the ensemble and how performers seem to be positioned with respect to our ears. The ambience of their performance environment is also affected by these effects. In pukka audiophile jargon (also known as review-speak or b*llsh*t) this is the stereo image, soundstage and air around the instruments. Most of the contribution towards achieving these Will'o'the wisps comes from the phase performance of the system and the reflective environment in which it tries to perform, if that is not too anthropomorphic a concept.

Acoustic art (i.e. all art objects and souvenirs on the walls of the listening room) plays a significant role in this, whether negative or positive. The worst kind of room for audio has flat parallel walls with hard plaster surfaces and no art works, souvenirs or other objects to break up the even dimensions between facing parallel surfaces. This is also a worryingly sterile environment that might have other psychological effects detrimental to a positive listening experience. Contrary to popular audiophile mythology, a widow recess actually helps a room by relieving the equidistant parallel surface horror with a slightly different dimension. Glass is not as perfectly reflective as plastered masonry (like brickwork, blockwork or stone) and curtains are jolly splendid absorber/diffusers operating down to the frequency ¼ wavelength from the glass and above the frequency defined by surface texture and pleats. The quarter wavelength distance affects room frequency response and the pleats affect intelligibility.

Immediately we can imagine that tapestries, wall hung rugs or large embroidery pieces will perform similarly to curtains. Many of the great cathedrals of Europe were once decorated by tapestries, the recently refurbished Notre-Dame cathedral was originally extensively hung with various drapery resulting in a substantially different acoustic from today. Some of the organ builders pitching for the job of installing the new replacement instrument were proposing various different new elevated positions for the pipes, to change the direct-reflected sound balance but the original positions transpired to be optimum. The early wall hangings predate the installation of organs and would therefore have had no effect on that choice. That the master craftsmen building these magnificent structures also sought to incorporate acoustic treatment is testament to their skill and today sound reinforcement systems are the means by which the congregation can hear the words of ceremonies.

The felted bowl, “Husbandry” by Jane Mercer is a good example of a piece that would sit decoratively on top of a shelf, sideboard or console table. Instead of the flat area of that surface and the wall behind it creating multiple reflections and comb filtering effects, this bowl would absorb a significant proportion of the reflections crossing the 90° included angle between wall and shelf. These reflections create delayed soundwaves at the listening position. The reflections also interfere with each other constructively and destructively, which can disrupt the illusion of soundstage. Mercer's piece, while beyond the capability of beginners like us, is an example of 3d felting. Individual pieces of old felt are cut into strips and twisted together using traditional cording techniques. This is a kitchen table whole family activity connecting everyone to the listening room with a sense of ownership. The red breasted robins shown would be ideal seasonal decorations at this time of year in those countries that celebrate such things.

Do Try This at Home

Use a mirror to identify primary reflection points in the room. Try placing big enough pieces of rumpled felt in these positions (using temporary fixings) and listen to the effect. Try this again over 50mm thick acoustic foam, because the wider dispersion from tweeters often results in more reflections from 2kHz to 20kHz. If there is any difference it will be worth locating something like acoustic foam there or for a more homely decorative solution create or buy felted art work.

Tests have shown that purposely created acoustic art works can typically provide about 75% of the diffraction, diffusion and absorption of similarly proportioned specialist professional products. At the 'Entangled' exhibition there was an old wool blanket that had been decorated with collage, tapestry and embroidery. This is a big bang-per-buck in terms of surface area treatment divided by effort. A quick test with a similar vintage pure wool blanket over 100mm of acoustic foam (2 densities layered) showed overall similar broadband effect to the same depth (total 125mm) of professional quality acoustic foam (not the cheap imitation sold by some vendors on auction sites) with some specific frequencies less effective due to the density of the blanket weave.

Conclusion(s)

This is not an April Fool or April Fish prank. Appropriate room treatment is increasingly recognised as more fundamental to good sound than the bits of wire, tweaks in sampling rate or magic stones loved by the esoteric audiophile. Obviously purpose designed and optimally positioned quadratic diffusers, bass traps and acoustic absorbers will be superior to these acoustic art works, but these can come close as 30 years of making and testing indicates. Now we can achieve musical harmony and domestic harmony simultaneously.