Articles and whitepapers

The Science Behind Domestic Wooden AV Furniture (3/6/2005)

By Craig Clarkstone, FX Furniture

Gramophone, radio, and for the wealthy, a simple black and white TV were the sole extent of the definition of the term 'AV' or 'Audio Visual' in the 1950's. Although these newfangled contraptions were enjoyed, it was felt that they did not fit easily into the home. In response, furniture manufacturers started to produce the very first cabinets dedicated to disguising these 'modern' inventions, leading to the concept of the very first AV furniture.

Radiogram with wood veneer

The 1980's sparked the growth of black ash, along with glass and chrome AV racks, while the 1990's rejected everything eighties. Lighter woods became more popular, and an interest in European interiors was sparked by contemporary designers and the IKEA invasion of our shores.

Current trends

Since the millennium, interest in interior design has soared, and sales of contemporary wooden AV furniture have increased. Indeed every furniture manufacturer is producing something for hi-fi and plasma screens, and there are of thousands of AV furniture manufacturers around the world.

Custom compact 42Ó plasma lift fitted at the end of the bed.

Whether custom-built or off-the-shelf, furniture for the home can be broken down into two categories, namely hi-fi cabinetry comprising wooden cabinetry designed specifically to blend into the home; and AV racks comprising simple shelving or a rackmount system, originally developed for AV professionals such as recording studios.

Generally, men have preferred simple open-shelved racks, being content to have their kit on display gathering dust, including the hordes of cables projecting out of the rear. Women on the other hand, have tended not to appreciate black boxes and hundreds of cables, preferring instead wooden cabinetry to hide it all away. It looks as though the British male however, is beginning to appreciate the finer points of interior decor.

Off-the-shelf versus custom-made wooden furniture

When considering AV furniture for a project, remember that each type of furniture has strengths and weaknesses.

The advantages of bespoke furniture are:
* It gives you exactly what you want.
* It is unique.
* It matches the decor of the home exactly.

The disadvantages of bespoke furniture are:
* It typically can take up to 3 months to make.
* It is normally more that twice the price of a similar off-the-shelf product.
* The time spent on developing bespoke furniture is normally much less that the time dedicated to off-the-shelf furniture. So although it looks better, it may in fact be poorer in design.
* Complex design such as mechanized plasma lift furniture will need detailed involvement of the cabinetmaker and custom-installer in its development, causing potential problems and misunderstandings.

The advantages of off-the-shelf furniture are:
* It provides the customer with a fashionable furniture product.
* It presents good value for money.
* It is available in a short space of time.
* The Design is well considered and the product has been tested.
* Accurate construction due to computer-controlled manufacturing processes.
* Consistent well-matched veneers and woods due to large stocks to choose from.

The disadvantages of off-the-shelf furniture are:
* Your friends or colleagues may have the same furniture as it is not unique.
* It may not match your room layout exactly.
* It may not be exactly what is required.

If you ask a manufacturer of high-end hi-fi what the perfect environment is for their products, they will suggest a cool room, away from other pieces of equipment, on a level surface, with the speakers in another room. There are several good reasons why.

Shielding from microphonics

Various electronic components, particularly valves which consist of a number of metal parts assembled together inside a glass envelope, can produce a variation in voltage if shocked mechanically though impact or airborne vibration. Metal parts can move, and in doing so will alter their capacitance. The pickup on a turntable for example, can easily be excited by the sound from the speakers and cause feedback. In varying degrees, all electronic components suffer from microphonics, so the only way to protect hi-fi equipment from this is by shielding it from the airborne sound vibrations caused by the speakers.

Furniture manufacturers have devised all sorts of ways to prevent vibration from affecting equipment, including lightweight shelves, stone and granite shelves, rubber mounted isolators, oak-coned feet, carpet spikes etc. To be honest, most would not work. Quite simply, the best way to stop microphonics is to either have your equipment in a different room to your speakers, or to shield your equipment inside a cabinet. If the equipment is to be put in a cabinet, then the shelves should be mounted on simple rubber blocks in order to absorb any vibrations in the cabinet carcass.

Shielding from electromagnetic interference

In order to sell AV equipment in Europe, manufacturers must comply with strict CE regulations and have their product tested in laboratory conditions to ensure that the equipment does not interfere with radio and television signals. All hi-fi equipment however, creates a certain amount of electromagnetic interference.

Transformers can often cause EMC interference

When equipment is stacked directly on top of each other, there is a degree of electromagnetic interference between them, often causing a light humming or oscillation of electronic components on the PCB. Transformers are often culprits as they create a strong magnetic field around them. The way to reduce this interference is to space hi-fi separates at least 50mm apart from each other, dependant on the type of equipment and thickness of material around it, or have a dense metal shield, such as steel, to absorb the interference.

Cooling and ventilation

In layman's terms, the friction of electricity moving through a conductor causes heat. The hotter a conductor gets, the less efficient it is. Therefore it is important to keep AV equipment operating at its optimum temperature. Inside an enclosed space or cabinet however, there will quickly be a build-up of heat, and equipment will start to perform less effectively unless a way to remove the heat is used.

Heat moves according to three basic principles:

Radiation - when heat moves by radiation, it is moving in the form of waves.
Convection - this is based on the principle that warm air rises and cool air falls, transferring heat via the flow of air.
Conduction - this is the method used to move heat through a solid material. For heat to transfer from one surface to another by conduction, the surfaces must be in direct contact with each other.

A good cabinet design will take into consideration all of these factors. It will ensure that the air in the cabinet is replaced regularly to remove convected air building up, and it will ensure that shelves are made from suitable materials to prevent conduction and radiation of heat from one item to another directly above. If fans are to be used, they must be the rubber-isolated, virtually silent type, controlled by a thermostat so that any noise is kept to the barest minimum.

FX Furniture shelves especially designed for convection.

Technology in wooden AV furniture

The application of good design techniques and understanding of scientific principles can make the difference between general mass-market furniture and specialist AV furniture.

Fluid dynamics

For the purpose of reducing heat build up, the application of fluid dynamics principles to the internal shape and structure of a cabinet is effective in improving air flow around the hi-fi separates and reducing heat build up.

Material selection

Equipment cabinets require special treatment, as solid wood cabinets tend to distort, causing the individual planks to crack when you place warm objects inside, so either careful heat shielding must be used, or grainless MDF to ensure that the cabinet lasts, and looks good in years to come.

Arca-Nuevo cabinets use veneered MDF to ensure no warping due to heat build up.

It is important to use quality lacquers. Often cheaper lacquers such as 'Acid-Cat' and 'Pre-Cat' are used as they are hardwearing, but unfortunately cause quite severe discoloration after a couple of years. It is better to look at other types of lacquer such as polyurethane or polyester, as these tend to discolour much less.

There are also two types of finishes, namely closed pore and open pore. Open pore is the norm, where you see the grain pores and shape in the lacquer. Closed pore requires much more work and is seen as a more luxury finish. This is where all the dimples and 'pores' in the wood grain are filled, presenting a smooth finish.

Infra red technology

Mounting any AV device in a cabinet or cupboard results in the problem of how to control it via an infra-red remote. There are two solutions. Glass doors, be they smoked, frosted or plain, are effective at letting the IR signal though. Alternatively, infra-red repeaters, such as the Xantech Dinky-link, are useful when solid cabinet doors are used, but some repeaters can be prone to interference problems, as plasma TVs emit signals that can affect the repeater.

Smoked glass doors in this AV centre allow Infra-Red signals to pass right through.

Environmental factors

Furniture production in the past has had a huge impact on the environment, but is now increasingly made from sustainable sources, particularly in Europe and North America. Certain species of hardwood should be avoided, such as Brazilian Mahogany, as demand for this tree has been the cause of large areas of deforestation. Other types of mahogany, such as African Iroko, are available which have similar grain properties.

MDF is a good use of waste wood products, but tends to have a large proportion of chemicals such as formaldehyde. EU laws however, mean that the MDF available in Europe tends to be of high quality.

Considerations for the specifier/designer

When designing a piece of AV furniture, either for manufacture or on a one-off basis, the designer must take into consideration:
* Wood/MDF choice- if using solid, will this warp?
* Lacquer choice - will this discolour?
* Pore type - closed pores or open?
* Heat removal - natural convection or fan-assisted?
* Cable management for power cables.
* Cable management for signal cables.
* Space for cables behind equipment.
* Operation of equipment via IR - glass door or repeater?
* Can the cabinet be removed for service access / maintenance?
* Can the cabinet take the largest components, if an upgrade is sought after?
* Choices of plasma lift mechanism (if required?). Does it offer:
- Quiet operation.
- Reliability.
- a manufacturers guarantee.
- What will happen if the cabinet breaks down in the down position?
- Cable management - will my cables get trapped?
- does the IR control for the plasma get interference from the plasma?
- is the mechanism CE certified? If not, it is illegal to sell it in Europe.

Final advice

When considering what type of cabinet to purchase, remember that well-designed AV furniture should protect and look after the equipment it houses, whilst making it easy to install and access equipment and cables.

The cabinet should not hinder the operation of the equipment and should prevent it from overheating. It should blend into the room it is intended to go into, and in two years time, should look as good as the day it was purchased.

Craig Clarkstone is a Director of specialist AV furniture manufacturer FX Furniture Ltd, based in Retford, Nottinghamshire.

www.fx-furniture.com