We do not have any specific recommendations for stands but the following guidelines should be followed when choosing suitable stands:

• Relatively heavy build, rigid and non-resonant.
• Top plate size suited to the ‘footprint’ of the speaker.
• Base plate size large enough to offer good stability, taking into consideration the size of the speaker and the stand height.
• Stand height should position ‘acoustic centre’ of speaker at, or close to ear level. The ‘acoustic centre’ of ATC’s 2-way loudspeakers is at the mid-point between bass driver and tweeter and the ‘acoustic centre’ of ATC 3-way loudspeakers is on axis with the mid-range dome.  Ideal stand height= ear height – distance of ‘acoustic centre’ from base of cabinet.

• Height – speaker ‘acoustic centre’ should be at, or close to ear level. See above for recommendations on suitable speaker stands.  For speakers supplied with ATC stands or floor standing models, the ‘acoustic centre’ height is defined by the stands the speaker is supplied with on the height of the cabinet.  In these cases, the vertical position of the ‘acoustic centre’ can be adjusted by tilting the speaker back, or forwards by screwing the stand/plinth spikes either in or out.
• Speaker-speaker-listener distance:The distance between a stereo pair of speakers should be approximately the same as the distance from one speaker to the listening position.  The speaker and the listener positions will form the ‘points’ of an equilateral triangle.  See diagram.

We highly recommend spikes are used when the speakers are positioned on carpet or a rug.  The spikes penetrate through the carpet (or rug) and into the ‘solid’ floor beneath and this will allow you to mount the speaker firmly and ‘wobble’ free.  It will also ensure the speaker or speaker stand does not mark the carpet.  On a ‘solid’ floor, spikes may not be necessary although they can be very useful to ‘level’ the speaker.  Spike shoes should be used to ensure the spikes do not damage the surface of the floor.

It is difficult to give a definitive answer as the size and proportions of the room and also the materials it is constructed from will have a large influence on the subjective sound quality.  As a basic rule, positioning the speakers closer to a wall will increase low frequency whilst moving them away will reduce low frequency output.  Smaller 2-way speakers with a more limited low frequency output will be much more forgiving of positioning close to walls whilst a larger speaker will be less so.

It is important to install appropriately sized loudspeakers in any given space if the best results are to be achieved. How well a loudspeaker works in any space is a function of the acoustic properties of the room, the performance of the loudspeaker, and the loudspeaker/listening positions. The acoustic behaviour of a room is often very complex, so there are no absolute rules about which loudspeaker will work best in a room of a given size. Consider that smaller loudspeakers tend to have less LF extension and less dynamic range, so these are better suited to smaller spaces, or closer listening distances. Larger loudspeakers tend to provide more bass extension, greater dynamic range and lower distortion for a given SPL and therefore are better suited to larger rooms.

• Tweeters and bass drivers in 3-way speakers can be dusted with a very soft brush.  Do not attempt to clean the mid-bass drivers in the 2-way speakers or the mid-range dome.
• ATC veneered cabinets are lacquered with a very hard-wearing catalysed lacquer. We do not advise applying any waxes or creams to the surface, instead simply “dust” with a slightly damp cloth to remove any light dirt. The surface can then be “polished” with a clean dry cloth. This keeps the surface free of wax and silicones which can collect dust.
• Satin black, satin white and all classic, tower and professional black cabinets and baffles should be cleaned gently with a microfibre cloth. Do not polish the surface.

When engineering a loudspeaker, especially a smaller speaker, the choice has to be made between higher efficiency or an extended low frequency response.  ATC’s smaller loudspeakers all offer excellent low frequency output for their size, with the downside of reduced efficiency.  This means that a little more power is required to produce a typical listening level and as a result we recommend amplifiers with a minimum power output of 75W per channel into 8 ohms.  It should be noted that all ATC loudspeakers have a nominal impedance of 8 ohms with a typical minimum of 5.5 ohms.  As a result, they do not demand as much current as lower impedance loudspeakers and present an easier ‘load’ to an amplifier.  This, coupled with the fact that as you drive a speaker with more power, the voice coil temperature will increase, in turn increasing the impedance, an amplifier with a higher power output into 8 ohms is likely to give better results than an amp with a lower 8 ohm power rating but that can double it’s power into 4 ohms.

Passive speakers use crossover filters that only employ passive components (capacitors, resistors, inductors) and the crossover filters are ‘located’ between the power amplifier and the loudspeaker drive units.

Active loudspeakers use active (powered) crossover filters and the crossovers are ‘located’ before the power amplifiers.  Each loudspeaker drive unit (two in a 2-way, three in a 3-way) has it own dedicated power amplifier, fed from the output of the active crossover.

While it is possible to design a high performance loudspeaker using passive components, an active design has a number of benefits, these are listed below;

1) More accurate crossovers

• Active filters allow independent control of level and phase(time).  This is not possible with passive crossovers.  With a passive crossover any changes you make to the circuit affect both level and phase.  The benefit this allows is that we can adjust for the crossover to have a perfect magnitude response and phase response.  The result is that the stereo imaging is much more stable and the tonal balance of instruments is improved.
• An active filters performance is not changed by the temperature of the drive unit voice coil as they are not directly connected to them.  A passive crossovers performance (filter shape and crossover frequency) will change with voice coil temperature which, increases with SPL (input power).  This leads to passive loudspeaker systems having a slightly different sound when driven at low SPL compared to high SPL.  The performance of active ATC systems changes very little with drive level.
• More efficient crossovers.  Active crossovers do not need to use series inductors to achieve their filter shapes.  Series inductors have resistance that reduces bass driver efficiency and also increases the Q of the low frequency tuning.
• More cost effective crossovers.  Passive crossover networks use large, bulky and expensive components in order to deal with the high voltages from a power amplifier.  Active crossovers offer better performance for lower cost.

2) Lower Intermodulation-Distortion

As the separate amplifiers in an active system are located after the crossover, they only operate over a limited bandwidth.  This reduces intermodulation-distortion and, in comparison to a passive system, even a bi or tri-amped passive system, an active system will show 15 – 20dB lower intermodulation distortion.

3) Improved Frequency Response and Stereo Matching

An active system can very simply feature individual gain trims for the two, three or four amplifiers involved.  This allows very simple fine tuning of the frequency response and the stereo matching.  Similar matching in a passive system would involve the replacement of large, soldered passive components which, in practice, is difficult and time consuming for the manufacturer.

4) Lower Cost for Higher Performance

Because an active system is designed, engineered and implemented by a single manufacturer into as compact a package as the design allows, cost is saved on electronics case work and packaging and the manufacturer can invest in real performance enhancing changes or pass the saving on to the customer.