Loudspeakers really don't need any introduction.   They can be found all around us in a variety of shapes and sizes and in use in a whole host of everyday products.

Does size matter?

It used to be that tall floorstanding loudspeakers were only an option at higher price points, but the low-cost breed has become something of a modern phenomenon.  It's not hard to see the attraction over smaller stand-mounting speakers or 'bookshelf' designs - a tall cabinet is generally much more aesthetically pleasing than a small box perched on a piece of ironmongery.  On sonic grounds however, stand-mounting speakers often beat their larger counterparts, particularly in the average sized living room in the UK.  While the greater cabinet volume of a floor-stander makes it easier to achieve deep bass, it bring with it another set of problems as designers attempt to control the effect of the box.  Small speakers are a better shape acoustically and mechanically, and often have the advantage in terms of rhythm, pace, timing and the like.  As a general rule, stick to the smaller speakers for smaller rooms while larger, more efficient models are better able to fill big spaces.

More on that all important impedance, sensitivity and power requirements..

Here's how to make sure your speakers match your amplifier

It's simple - you get the speakers with the highest sensitivity you can find, hit them with the biggest power amp you can afford, and there's no problem, right? Not quite, since there is another factor in action here - impedance.

Sensitivity is important: speakers with a rating of 87dB/W/m will need twice as much amplifier power to generate a given sound level as those with 90dB/W/m, which is why valve amplifiers with tiny outputs are generally used with speakers having sensitivity of 100dB/W/m or more. It's worth making the point that a 100W amp only gives 3dB more level than a 50W design, but then again that 87dB/W/m speaker design only needs one Watt to deliver 88dB of sound pressure. No big revelation there, but more to the point is that if you want to crank the level up another 12dB to 99dB, you'll need 16W of power...    However, before you get particularly power-crazed, bear in mind that even at high levels, your 100W per channel amp may only be delivering a constant 10-15W into the speakers - the rest of the power range is there to provide for the peaks and troughs of the music's dynamics.   It's virtually impossible to damage a pair of speakers by using them responsibly with an amp that seems too powerful.

But impedance is more often a limiting factor than amp power. Most amplifier specifications are quoted into a 8ohm load, but the fact of the matter is that the speaker doesn't exist that is a perfect 8ohm load right across the frequency range. Most start out at around 8ohms, but can dip as low as 2ohms or less at some frequencies. Others have nominal impedance figures of 6 or even 4ohms, and may or not have similar dips.

Now all this is no problem if the amp works as a perfect voltage source, since basic physics tells us it will double its output as impedance halves. In other words that 50W amp would deliver 100W into 4ohms, 200W into 2 ohms and 400W into 1ohm. A lower impedance figure doesn't make life easier for an amplifier - on the contrary it means the speaker sucks more amplifier power for a given output. Not a problem provided your amp measures up to the ideal, doubling its power as impedance halves, but many a 50W amp delivers not 100W, but 70 or 80W, into a 4ohm load. And there aren't too many 100W amps (even taking into account the fanciful way many manufacturers arrive at such a figure) capable of clouting 200W into 4ohms, let alone 400W into 2ohms. Indeed, some amps have a power rating that's quoted into a 4ohm load, to make them seem more impressive. If this is the case, remember your 50W/4ohm amp may only be 25W in terms of standard amplifier measurement.

So low-impedance speakers will make many an amplifier struggle, and it doesn't help if you start off with lowish 8ohm power output on the amp. The problem is that the power supplies can't top up the power as fast as the speakers are draining it, and we know of at least one acclaimed European bookshelf design that's an absolute pig when it comes to amp matching. Not one to try with that 20W per channel valve amp… 

Most speaker manufacturers play it cautious when it comes to indicating a maximum power handling capability for their designs, and using a speaker rated at 75W maximum with an amp rated at 100W maximum, for example, shouldn't be a problem. Only if you drive the amp so hard that it starts distorting - 'clipping' is the accurate description, and it sounds hard and fatiguing - can you damage the speakers. Too little power? Ah, that's a different matter.

If the speakers are said to need at least 30W per channel, that's what they need - driving them too hard with too feeble an amp sets up that distortion and whoops, there goes a drive unit. The tweeters tend to go first, simply because their tightly-wound coils of very fine wire are more vulnerable. It's an expensive problem, take it from those of us who've done it! Sensitivity figures give an indication - but only an indication - of how loud the speakers will go with a given amp. They're expressed as a figure in decibels (dB) for an input if one watt (or sometimes 2.83Volts), the measurement being taken at a distance of one metre. So you get a figure of, say 89dB/W/m - the higher the figure, the easier a time it will give the amp. Most modern speakers fall in the range of 87-92dB/W/m; speakers with figures below about 85dB/W/m may give some lower-powered amps trouble, while models with figures upwards of 100dB/W/m are available either for use with valve amps of tiny output, or for silly volume levels with modest amps (take a bow, Cerwin-Vega!).

All that said, speakers with low impedance aren't necessarily a bad thing - some highly-rated designs start off with 4 or 6ohm nominal impedance. It's just a matter of knowing whether or not your amplifier is up to the job, especially if you're expecting high listening levels. True, that 86dB/W/m design might only need one watt to get to a highish domestic listening level, but if it has a low impedance rating and you're using a low-powered amp that doesn't handle impedance changes too well, you could well find you're rapidly running out of power for the dynamics of ordinary music, not to mention those occasions when you want to crank up the level. That's when your amplifier will clip, compressing the sound and potentially frying speaker components, and when you're trying to impress someone with how loud it goes, nothing is more embarrassing than a failure to perform!

Speaker Positioning

What is the best way to set up loudspeakers?  Well there is no best way but I can give you a few tips that should give you good performance.

A loudspeakers will always interact with the room in which it's used, so buying the right box is only half of the story - to get the best from them you need to position them correctly.

While manufacturers make their own recommendations as to whether speakers should be used close to a wall or out in free space, these aren't rules written in stone. Experimentation is all: one design may sound great within a foot of a solid rear wall in one room, but unbearably boomy in the same position in another. Suck it and see.

It's also worth experimenting with toeing or angling your speakers in towards your normal listening position - that can help to improve imaging with some speakers, and can also help to tame bright-sounding systems but may have an adverse effect on image depth.  Rather than have them firing straight down the room, try swinging them in a little - you could just find everything suddenly snaps into focus. Some manufacturers advise against it - take a bow, Mission - but we usually find it helps. If it makes the sound better for you, then it's the way you should do it - however wrong it may seem.

Of course, the room itself can have an effect on the way a loudspeaker sounds.  Lot's of soft furnishings tend to soak up the midrange and treble leading to a softer sound, whereas a very bare room will emphasize the same frequencies and lead to harder sound (ever notice how hollow a bathroom or even an auditorium sounds?).   

Hint: don't try using the Castles in an attic room with a sloping wall/ceiling, or things get very weird-sounding! But whatever the speaker, it's best to avoid putting them close to side walls, and certainly away from corners, since these definitely cause boom and undermine imaging.

Loudspeaker Phasing

When your stereo speakers are connected in phase, the drivers of the left and right speaker move in and out at the same time. When they're out of phase, the drivers of the left speaker move in, while those of the right move out. If your speakers have removable grilles, you can pop them off and actually see this.

Stereo speakers should always be connected in phase. Out-of-phase speakers sound "not quite right" — imaging is vague and there isn't much bass.

To hook up your speakers in phase, just make sure that your positive receiver (or amplifier) terminals are connected to the positive speaker terminals, and your negative receiver terminals are connected to your negative speaker terminals.

It helps to pay attention to the markings on the wire — look for print, a stripe, or a rib that may be molded into the wire's jacket. If you find that your speakers are out of phase, don't worry, it's easy to fix. Just switch the positive and negative leads at one of your speakers (not both).

Loudspeaker Cables

At the end of the day, a cable is only the means of conveying a signal from the amplifier to the speaker, and a good quality low loss cable ensure that the signal remains intact.

The best tip that I can give you is use the best cable that you can afford and keep the runs of loudspeaker cables as short as possible. The best system has an amplifier (either a monoblock or a stereo amplifier configured for bi-amping) right next to each loudspeaker. Even the fattest cable has some resistance and this will dissipate some of the current flowing to the loudspeaker. This has the same effect as restricting the power and will tend to colour the sound. The cable also has capacitance and inductance. Although these have a small effect at audio frequencies, they do have a detectable influence on the sound. A short cable has less capacitance and inductance and therefore less effect on the sound quality.

There is no maximum length for a speaker cable: the sound quality just continues to deteriorate as the cable is made longer. If you don't have an amp for each loudspeaker then try to place your power amplifier in between the speakers at an equal distance from each one.

In most systems, the trade off is in longer signal cables. A signal cable tends to work like an antenna, picking up any stray radio signals. The longer the cable the worse the effect. However, in a well-screened, high-quality cable the interference is negligible. It is best to put up with long signal cables if it allows you to have short loudspeaker cables.

A great number of modern  loudspeakers consisting of more than one driver inside the same box allow for bi-wiring/amping.  The driver is the unit that actually makes the sound and it's usual to have different designs for different frequency ranges ¾ one for low frequencies, one for high frequencies and, sometimes, another for the mid frequencies. The loudspeaker manufacturer often provides terminals to let you connect to each driver separately. Bi-wiring is the process whereby one cable is run from the amplifier to feed the low-frequency driver and another cable is used to feed the mid- and high-frequency driver(s). This gives each frequency band a separate path and reduces the interaction between them. Bi-wiring also offers a lower resistance path to the loudspeaker.

The difference between connecting your loudspeakers using a pair of cables each costing 'X' or via a single higher-quality cable costing '2X' is small. However, adding a second speaker cable to an existing system is a cost-effective upgrade.

If the option for bi-wiring/amping is there then use it as it will give you the best performance.  Be aware that the effect varies from speaker to speaker and the most gains are to be had from adding an extra power amplifier.

Stands and Spikes

Why do speakers sound better on stands? If it's a matter of getting them to the right height, surely a shelf at the correct level will do just as well? And if it's all about putting them on something solid, a big heavy sideboard or wall unit should do the trick, right?

Well, no - not really. Yes, stands work through a combination of position and support, but they also isolate the speakers and keep them absolutely still - and asking your shelves to do that is just too much. If you've small speakers, unless they're among a small group specifically tuned for wall-mounting they'll sound best on stands. As a general rule, the right stand for your speakers will raise them to a height where the tweeter (the little treble driver) is at ear-height when you sit in your usual listening position. Some manufacturers tune their speakers to be positioned higher or lower than this, however, so check first.

Similarly, the best stand is usually a hefty stand, though some speakers are designed to be used on lightweight open-frame supports. The other purpose of the stand is to keep the speaker still, so that some of the energy of the drive units isn't wasted in moving the whole speaker back and forth by minute distances. Remember school physics...?

To that end, the use of spikes on the stand helps locate it solidly to the floor, by piercing carpets without damaging them. They also let you level the stand by adjustment of the spikes. On hardwood floors you can avoid damage by putting a penny coin under each spike, while on very resonant boarded floors a paving slab under each stand will also help. Top-spikes on stands help by locating the speakers rigidly, while minimising the contact between speaker and stand.

Alternatively, blobs of Blu-Tack between will have a similar, but sometimes sonically different, effect - experiment! Filling stands with sand, lead shot or proprietary materials like Sound-Bytes adds mass, and also deadens resonances, stopping the stands ringing'. If you're going to use sand, use kiln-dried silver sand - not that very yellow builder's sand that's much cheaper or a few bucketfuls off a beach or from the kids' sandpit. Moisture in the sand can rust metal stands and warp wooden ones. Floorstanding speakers also benefit from spikes and mass-loading (where this is designed in). But be careful when fitting spikes to floor standers: the threaded inserts that take the spikes can twist out of the cabinet material if you over tighten things. Use a spike-spanner, and use it carefully!