2. Cabinet Design & Concepts
On first inspection, most monitor speakers can appear very similar in design, apparently differing only cosmetically other than their size. Of course in reality, there are many differences between models, and you should familiarise yourself with the key features and specifications before deciding on which speakers are right for you.
Infinite Baffle or Reflex
There are two major types of studio monitor design - infinite baffle and reflex. The infinite baffle design has a sealed cabinet, whereas the reflex is ported, usually by a hole on the rear, and there are pros and cons to both designs.
The sealed infinite baffle design houses its drivers in a controlled environment - the air inside the cabinet has to be compressed or expanded for the drivers to move. This helps to create a smooth phase response, and as such is favoured by many engineers. Its drawbacks become apparent particularly with low frequencies though, as the low frequency driver or woofer has to work hard against the high air resistance within the cabinet, and as such this type of speaker tends to suffer from limited bass response. A common example of the design is the ubiquitous (but now discontinued) Yamaha NS10M.
The more common ported reflex cabinet makes use of its semi-open characteristics by allowing greater air flow in and out of the cabinet, which in turn allows the woofer to move more freely. Most manufacturers also tune the port length and diameter and the cabinets internal dimensions to boost the lower frequencies. The ultimate aim of a monitor speaker is to provide a flat and accurate representation of its input signal, so excessive bass response from incorrect design or port placement is less than ideal - its a fine balance to strike.
Passive, Powered or Active
This is an important subject to understand and is an area often surrounded by confusion. The passive type monitor was the only game in town for many years - they require the use of an external amplifier to boost the audio signal up to a sufficient level to power the speaker cones or drivers. Before reaching the drivers, the audio signal is passed through a passive crossover, splitting it up and sending the lower frequencies to the woofer and the higher frequencies to the tweeter. The frequency at which the signal is split is called the crossover point, which in a 2-way system (of which more later) is typically somewhere in the region of 2kHz.
Particular care should be taken when matching an amplifier to passive monitors - most people are aware that you can damage your monitors with an amplifier that is too powerful, but in fact an amplifier that is underpowered can be more dangerous. This is because a low-powered amplifier can easily run out of headroom when a sudden peak in the signal comes along, and speaker drivers are actually much more easily blown by this kind of distortion at a relatively modest level, than they are by a clean signal at a higher level. In the same way that car tyres are not covered by warranty if you get a puncture, speakers are not covered by warranty if you blow them so take great care! In general, you should aim for an amplifier whose RMS power rating per channel matches or slightly exceeds the program power rating of the speaker, at the speakers rated impedance. This assumes that the manufacturer uses sensible parameters to measure the program power, so if in doubt, use the RMS rating of the speaker and go a little higher with the amplifier power. More information on these specifications can be found in the terminology section of this guide.
Active and powered speaker types are often mistaken for each other. A powered monitor is best described as a passive monitor with the amplifier and passive crossover circuitry described above built in. The main advantages over a passive system are simpler setup, better amplifier to speaker matching (in a well designed speaker), and much shorter speaker-cable lengths.
The active monitor is becoming more and more popular in studios, and differs to powered and passive monitors in two ways - firstly, the crossover contains active circuitry which typically operating at line level and allows for easier and more accurate control of the signal. Secondly, the separated signals are sent to multiple amplifiers whose output is then sent to the relevant drivers. This separation of systems within a single enclosure allows better and more efficient amplifier matching, and more accurate and independent control over the splitting of the signal.
Generally speaking, monitors have either two or three drivers to enable them to handle the full frequency spectrum. 3-way systems house a woofer, midrange driver and tweeter to handle the bass, mid and high frequencies respectively, whereas 2-way systems let the woofer deal with both the low and midrange. In most instances a 3-way design will outperform a similar 2-way system, however this is not always the case - the extra cost associated in producing 3-way crossovers and additional amplifiers can force manufacturers to make savings on other components - trust your ears! You will sometimes come across 2-way designs that have two low-frequency drivers these operate in tandem and are either used simply to provide more bass from a given cabinet shape (producing similar results to a single driver with the combined surface area of the two cones), or, in a DAppolito configuration, with one either side of the tweeter to additionally improve dispersion. Finally, there exist a few 1-way designs these are not exactly hi-fi, but instead are designed to be used as a secondary reference to give you an idea of what your mix will sound like on a typical domestic system. Auratones 5C is a classic of this type, and although long discontinued, there are modern equivalents.