The acoustics we live with


Created on 04.09.2006 21:50.

Updated on 17.02.2020 21:08.

Author: Konstantin Bystrushkin, Larisa Stepanenko ..

The choice of a speaker system and its purchase is the central and most important moment in the formation of your home audio system. This is understandable – not a single component is capable of influencing the quality of its sound as much as acoustics.

A good speaker system will sound great in a duet even with a simple music center, while an unsuccessfully selected one is capable of cutting the sound in the bud even in a top-end High-End complex.

Is it any wonder that this topic is the undisputed leader among the questions asked by our readers, almost half of S & V’s editorial mail and phone calls to the editorial office are in one way or another related to a request for recommendations on the selection of a speaker system. So isn’t it time for us, dear readers, to finally talk about this multifaceted and burning topic?

Basics of acoustics

Let’s start our “acoustic gatherings” simple – with definitions. Under acoustic system in the broad sense of the word, we mean an electromechanical converter of electrical sound signals into acoustic ones. In the vast majority of modern acoustic systems (more than 90%), this transformation is carried out using electrodynamic heads, the principle of which is based on the interaction of the magnetic field of a permanent magnet with a voice coil wire.

When audio-frequency currents flow through the wire under the influence of the electrodynamic force, the loudspeaker coil is alternately drawn in and out of the annular gap of the magnet, depending on the direction of the electric current. Well, then everything is simple: the voice coil is mechanically connected to the emitter – the diffuser, which, in fact, creates in the space the thickening and discharging of air, i.e. acoustic waves.

Since the sound wave emitted by the front (front) surface of the diffuser is in antiphase with the acoustic wave emitted by the back of the diffuser, both of these waves, when the dynamic head is operating in an open space, can extinguish each other, which is called an “acoustic short circuit” (according to analogies with short circuit in electrical networks).

To avoid this nuisance, the heads are placed in a housing, the main purpose of which is to exclude this very interaction of sound waves from the front and rear surfaces of the diffuser. Loudspeakers installed in the cabinet together with cross-over filters form a speaker system, sometimes called a sound column or simply a loudspeaker.

A relatively small number of acoustic systems use emitters based on other physical principles (electrostatic, piezoelectric, isodynamic, plasma emitters). Since these types of “exotic” loudspeakers are practically not used in mass loudspeaker systems, the scope of our today’s conversation will be limited to considering only loudspeakers with electrodynamic heads.

Big or small

Let’s talk about speaker sizes for a warm-up. So, acoustic systems are: expensive and not very small-sized (called “bookshelf speakers” or abbreviated “bookshelf”) and quite the opposite – designed for direct installation on the floor. Therefore, they are called “floor-standing speakers”, which, you see, is quite logical.

Small-sized “shelf” acoustic systems due to their small size have obvious advantages over floor-standing “cabinets” when placed in a small apartment.

In addition, the small dimensions of the bookshelf speakers make it relatively easy to provide the necessary rigidity of the cabinet, which is extremely important for achieving high sound quality (this issue will be discussed in more detail below).

And, finally, the smaller dimensions of the speaker housing will also require less material consumption for their manufacture, which, in general, should reduce the cost of this type of speaker systems. Indeed, if simple, but already well-sounding “shelf” speakers can be purchased today starting at $ 200, then the cheapest floor-standing speakers will cost you no less than $ 300.

However, this is where the advantages of “shelf” speaker systems over floor-standing ones basically end. Along with the above-mentioned advantages, the “shelf” acoustics have very significant disadvantages.

Due to its small dimensions, the elasticity of the air in the internal volume of the case significantly affects the quality and quantity of low frequencies emitted by the system. Naturally, not for the better, since the elasticity of the air reduces the flexibility of the suspension of the woofer cone installed in the loudspeaker cabinet.

Reducing the flexibility of the suspension, in turn, significantly increases the resonant frequency of the loudspeaker. The sad consequences of this are well known – small-sized “shelf” speakers are simply physically unable, at acceptable values ​​of their sensitivity (more on that below), to satisfactorily reproduce the lowest frequencies (below 50 Hz), although the same low-frequency speakers installed in large enclosures, “Basyat” please.

In addition, compared to more powerful and often more sensitive floor-standing systems, shelf units tend to reproduce a lower dynamic range of audio signals. True, this does not mean at all that small-sized speakers, in principle, play poorly. Far from it – the balanced sound of the best “shelf” speaker systems is subjectively perceived perfectly and sometimes gives odds to many “floor speakers”. A prerequisite for good sound from small-sized acoustics is its correct placement.

At the same time, it is vital to ensure that the system is securely installed, eliminating unwanted vibrations and vibrations of its housing. The easiest way to achieve this is by installing the “shelf” speakers on special stands (Speaker Stand), produced by a number of specialized companies (Target, Atacama, etc.).

However, good stands are quite expensive – $ 100-400, so the total cost of buying a “cheap” small-sized system together with stands can “go off scale” for $ 500, which is quite commensurate with the cost of relatively decent floor-standing speakers.

As they say – what were they fighting for? Maybe it’s really better to just buy and buy floor-standing speakers and not bother with the selection of stands for “shelf” speakers?

The idea is interesting, so now let’s start considering the question of what we are losing and what we are gaining in terms of sound quality when buying floor-standing speakers. In principle, by choosing a large floor-standing speaker system, we can potentially count on deeper and more powerful bass due to the large volume of the floor-standing speaker cabinet.

But “there is no happiness in life” – the large size of floor-standing speakers creates new problems for us. Provide body rigidity more …