[ Home | Staff & Contacts | HiFi Playground | Listening tests | DIY & Tweakings | Music & Books ]

Ikea Acoustikea

Nodes, Antinodes & Hol Tables

[Ikea Hol Table]
[Italian version]

Product: Ikea Hol Table
Manufacturer: Ikea - Sweden
Price: 49€, £18.99 UK
Size: (double size model costs 79€, £34.99) Reviewer: Mark Wheeler - TNT UK
Reviewed: January, 2007

"What's he up to now, reviewing furniture?", demand plebs, stage left
"It has potential as a hifi accessory", replieth humble scribe
"Is it as a turntable support?" enquire plebs, slightly mollified
"No", comes the stern reply
"LP storage?", they ask, their curiosity piqued...
"No", the old one answers,
"Not another in the endless saga of vibration control...we can't stand that again....", plebs complain
"Yes indeed, but airborne this time"

I spotted this £19 (49€) product in my local branch of Ikea while looking for new LP storage since my recent house move. Aye aye, methinks, that will have audio gadget potential... It is made of solid walnut. It is not veneered chipboard or foil finished mdf, which regular readers know I would not give space in my house. It has holes in it on all four sides and top, hence Ikea's amusing name Hol. How do people get the job of thinking of the bizarre pseudo-Scandinavian, but ultimately meaningless Ikea product names? Is there a university course at Stockholm, where language students expertly apply their skills to learn how to coin a name that actually means nothing in any European language, but sounds like it should mean something?

I want that job. I could sit around with my friends, listening to music and drinking wine and coining meaningless neologisms...

[Hol support anyone?]

The Hol table comes in two sizes and would probably make a perfectly adequate audio support for components. Equally, it has room inside for vinyl lps or the usual audio junk we all acquire, like cables, or footers, or adapter plugs, we no longer use. But I have other ideas.

The space inside the Hol is defined by four perforated walnut sides. Each hole in the Hol is 20mm x 20mm, separated by strips of walnut land 20mm wide. Each area of perforation on sides, or top, measures 380mm x 380mm.
It looks to me extraordinarily like an acoustic absorber. On its own one Hol could attenuate from around 200Hz up, based on internal dimensions. Placed near a wall or corner, its 46cm x 46cm cube fills 50cm x 50cm and it could work down to about 100Hz depending on room or placement. The larger version may get an octave lower than that, depending on placement.

Better yet, through careful placement it could disrupt standing waves and hence contribute to the destruction of the usual regular patterns of constructive interference or destructive interference that plague the listening rooms of typical popular housing.

In the typical rectangular rooms of Western homes, patterns of nodes, antinodes and eigentones are formed. Plenty of information is available in books or out there on the web. Hard masonry walls and floors tend to reflect most of the audio band. Some lighter cavity walls, drywalls, timber-frame construction and plasterboard tend to absorb lower frequencies; indeed many modern houses have internal partitions that are virtually transparent to low frequencies. If your listening room is built these ways, then this article is not for you. Your room has quite different problems.

Rooms with solid masonry walls, but suspended timber floors and plasterboard or lath & plaster ceilings are less likely to suffer these low frequency problems either, but those parallel, facing, solid walls will set up patterns of interference, causing exaggerated bass, of certain wavelengths (hence frequencies) in some places and loss of bass of other wavelengths in the same places, but a completely different pattern elsewhere. Put on your Jaco Pastorias cds and wander around your room. Try the Chesky bass resonance test (CD track) or use some low frequency pink noise and wander about on your hands & knees; or half crouched; or fully upright. You'll probably notice a waxing & waning of various frequencies. These level variations are caused by the distance between the stereo speakers and the distances from the room boundaries of the speakers and your ears. Solid floors and the concrete ceilings of apartment blocks probably suffer the most from these problems, especially in view of their completely rectanguloid room shapes, without the relief of alcoves or bay-windows of more traditional architecture.

The classic Beranek text should be in most libraries and still holds true in this respect, after many years; I'm sure my hardcover Focal Press edition was only a couple of quid in a used bookshop.

Texts Worth Reading

  • Leo L. Beranek: Acoustics, seems to be worth over £200 on Amazon these days, so order it from the public library!
  • Beranek & Sabine: collected papers, I had to order from a university library
  • F. Alton Everest: Master handbook of Acoustics, not read it but contents looks excellent
  • Society of Acoustics, useful links
  • Building Acoustics Quarterly, link to use index and order backnumbers

My previous listening room had parallel 300mm stone walls and a 150mm cast concrete slab floor, on a bed of Styrofoam Floormate insulation. It had an uneven 200 year-old lath & lime cement ceiling with exposed beams that disrupted reflections and ceiling related standing waves. The pattern of nodes & antinodes set-up by the side-walls resulted in bass-nulls right down the centre of the room from the speakers to the central listening chair. The provision of a well-stuffed sofa along one side-wall near the listening position did ameliorate this problem to some extent, but the problem continued due to the remaining exposed parallel areas. A permanent cure was effected by panelling the lower 1m of the walls with birch plywood of different thicknesses 6mm, 9mm and 12mm and faced with 'bead&butt' tongue&groove softwood boards. This wainscot was mounted with varying batten spacings, to prevent a new resonant problem being introduced. The cavity behind the wainscot varies dramatically in depth due to the ancient uneven stone walls and is filled with fibreglass wadding. The room became much warmer (temperature not tone) and the in-room bass response much more even. Speaker placement became much less critical.

The temperature insulation gain is worthwhile in itself in a room where one sits for hours listening to music, but could a similar acoustic effect be achieved at less cost and disruption by one or more Ikea Hol tables?

Because my new listening room has big areas of glass, more than half the total wall area, it absorbs bass at the boundaries. The ceiling also slopes, so Low frequency resonance is really evenly distributed. If anything, this room is bass-shy. Freak conditions will have to be created for this test.

Technical Tests

The most dramatic and surprising result was on a 40Hz tone generated in a room end just 142cms wide. At best this should support a half-wavelength standing wave between 115Hz to 120Hz depending on humidity and atmospheric pressure. The rest of the room is asymmetric and without any significant parallel surfaces. This space was chosen because it has a hard floor, and low solid ceiling at 190cms. the portable cd player used to generate the tone from a test disc is not the last word in fidelity, accuracy or output capability, so the 40Hz tone inevitably has some overtones and the hand-held meter is not gated. There are limits to what one can achieve experimentally at home, but it is at home that the results will be applied. And you, dear reader, guessed correctly, this test is in a bathroom!

The tests use test disc tones of 40Hz, 80Hz, 100Hz, 160Hz; signal generator sine tones; test sweeps 20Hz-20kHz; tracks with clear melodic bass lines; bass guitar.

Test Signals & Recordings used to generate room nodes & antinodes

  • Chesky: Best of Chesky Jazz and more audiophile tests Volume 2, percussion imaging tests; bass resonance test
  • HiFi News & Record Review: Test Disc, HFN003; Spot Frequency response, Sweep Frequency Response (individual channels), wide frequency sweep
  • HiFi News & Record Review: Test Disc III, HFN020; LEDR test; spot frequency tests
  • Cheap kit Signal generator; everyone should have one
  • Radio Shack (formerly Tandy in UK) Realistic: sound level meter
  • Vellemann: handheld oscilloscope
  • Cheap contact microphones & cheap plate microphone
  • Fretless J-Type Bass Guitar (allows continuously variable tones)

Absolutely empty, the Hol table, when placed into this space, attenuates these tones by 2-3dB. This is regardless of position against the end wall; central, or in a corner, or not-quite parallel, or propped up sloping. One position, about a third of the way along and angled at about 15°, exceeds 3dB of attenuation. 3dB is the equivalent of a doubling of amplifier power. This attenuation is merely caused by disrupting the wavelengths' endless reflection and re-reflection between two facing parallel surfaces.

Lifting the lid on the Hol table, and dropping in a couple of ordinary cushions (about half filling the void) increases the attenuation to nearly 5dB. Now the placement is much less critical, and the attenuation remains between 4-5dB in all positions. I have not tried lifting it from the floor, because the point of this exercise is to have domestically acceptable solutions, not render one's living areas any more industrial than the usual audiophile den. If you're a bloke living on your own you can arrange the listening room exactly to suit audio, without aesthetic compromise, but if so, you guarantee to remain remain a bloke living on his own.

Emptying the contents of an old polyester pillow onto the cushions lifts the performance to nearly 6dB of attenuation. Replacing the contents of the Hol table with long-fibre wool, as specified by Dr A R Bailey for stuffing transmission lines (I happen to have a bag awaiting a loudspeaker) raises the game further.
An Ikea Hol Table, roughly filled with long-fibre wool will attenuate a 40Hz standing-wave by more than 6dB. A 6dB increase in sound pressure level is a doubling of subjective loudness.

That test seems a bit random and variable in quality and application for a proper conclusion to be drawn. Next up, I place a Hartke bass guitar practice amp into the corner of my listening room and play glissandos on a fretless bass, noting where the peaks & troughs in amplitude occur. There is a 9dB difference between slightly sharp of low G and C on the low E string. It repeats whether I pluck softly or loudly. Moving my body between the amp and the opposite wall dramatically reduces this difference. The Ikea Hol table has much less effect than the human body, but still reduces the peaks-&-dips range by about 4-5dB. OK, this is NOT SCIENCE.

What these experiments lack in scientific rigour, they more than compensate for with drama. There would be absolutely no point in TNT-audio setting up a scrupulously thorough test in an empty void with solid masonry walls, because those readers incarcerated in such conditions are unlikely to be permitted stereo-systems. Or internet access to read this, so I suppose they aren't TNT-audio readers anyway.

So, while I lack the facilities in my home, to conduct this sort of experiment rigorously and throughly, it has been possible to demonstrate that there is a measurable effect, and therefore a reasonably predictable effect. The only place I might have access to acoustic research facilities is so unlike a domestic living room that the experiment would be utterly meaningless. This is one reason why acoustic cures advertised with impressive graphs and exemplary laboratory performance may not work for you at home.

The only test I can really make that will be useful for you to read will be in my listening room, with my hifi playing some familiar records. So the room gets rearranged to introduce some deliberately lumpy bass by placing speakers equidistant from corners, and nearer them than usual. Ah yes, the bass now waxes and wanes as I move around the room...and there's a distinct lf suckout in front and to the right of my usual listening position. The chair gets moved to the worst place, and bass rich records played.

The Sound Effects

The system, set up like this, sounds much worse than usual. It takes several attempts, bobbing up & down between listening seat and Hol table, to find the best placements. Several positions seem to work equally successfully.

[The Holestory]

It is really simple. Bass becomes more even. The wrong speaker positioning sounds more like, but not nearly as good as, the right speaker positioning. Tight bass transients recover some of their tension, 90s dance like Dave Clark's Archive One, that sounds more like a full club than a soundcheck in an empty warehouse.

Drum'n'bass timing improves, the lower octaves lagging less behind the percussion samples, although this can often seem like a characteristic of the production style. Synthesised bass lines, which by their very nature tend toward even temperament, plunge less into resonant pauses. In-room the difference between cheap hollofil polyester pillow-stuffing and long-fibre wool is inaudible so the extra expense is unecessary, and the pillow-stuff should be CE approved furniture grade while the wool definitely is not, thus constituting a potential fire-hazard near all those hot valves.

I wonder if the effect is caused by the holes in the Hol table, causing it to behave like a panel absorber, or whether it is merely placing an object along the standing wave axis. I substitute the rival product: a footstool, padded but fairly solid with a dense leather surface. The footstool has no audible effect placed in similar positions to the stuffed Hol table. This surprises me as the footstool's padded leather surface should be a frequency selective device, tending to absorb or disperse lower frequencies, while scattering high frequencies. I might expect the effect on power response to be similar to the perforated surface of the Hol table. But the footstool fails to perform at all. This suggests the holes of the Hol table do the work.


If TNT-audio had posted this review in April, readers might have guessed it is a joke. It's appearance in Winter, traditionally the season audiophiles get serious about their toys, implies that this is no joke. A cheap furniture product, used with a little imagination, can perform as well as some quite expensive domestic acoustic accessories.

It is not going to cost as much as an audiophile marketed geegaw, and its effect in the listening room is just as unpredictable. Readers whose rooms suffer from zones of bass emphasis and zones of bass cancellation risk little by buying one or two of these tables and experimenting with stuffing and placement. If it makes no difference, just place it adjacent to the listening chair to support that glass of Pomerol like the '61 Pétrus we TNT-staffers quaff everyday.

Music Enjoyed During This Review

  • Noel Redding: The Experience Sessions, 2003, RTH-2017
  • Jaco Pastorius: Golden Roads
  • Miles Davis: Tutu
  • Dave Clark: Archive One 05 02 96, 12"vinyl
  • LTJ Bukem: Journery inwards, 12"vinyl

Copyright © 2007 Mark Wheeler - www.tnt-audio.com

[ Home | Staff & Contacts | HiFi Playground | Listening tests | DIY & Tweaks | Music & Books ]