Today we’ll cover another aspect of vital importance for our recording and listening sessions: loudspeakers. This is certainly a broad field, so my idea is to start by describing what loudspeakers and speaker cabinets are, how they work, the division of speaker types according to their basic differences, and so on... I suppose that, as usual, our pages today will fall a bit short, so we will split this section into two parts:
a) Loudspeakers. Introduction, description, and types.
b) Studio Monitors.

What Is a Loudspeaker, Basically?
We could say that the loudspeaker is the reciprocal transducer of the microphone; the device in charge of converting electrical energy into acoustic energy, in the inverse way to a microphone.

Loudspeakers (broadly speaking) have two transducers, and we will classify them according to these:
TEM, a motor that transforms electrical energy into enough force to move the diaphragm.
TMA, a mechano-acoustic membrane that converts that force into pressure radiated into the air.

Types of Loudspeakers
Piezoelectric Speakers
This type of speaker is commonly found in high-frequency drivers. They consist of a motor built from ceramic or polyester (generally) which, on receiving the voltage difference between its metallized surfaces, produces compressions and different types of elongation.
Advantages: inexpensive, they radiate with little electrical power, and simple construction.
Drawbacks: difficult to get them to respond in the low-frequency range.

Electrostatic Speakers
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Their standard construction is based on placing two plates, one fixed and one moving (the diaphragm), in a capacitor structure in which a supplied electrical charge is stored. The audio power amp then boosts that energy (stored between the two plates), causing the diaphragm (the moving plate) to move and generate pressure.
Advantages: excellent response in the mid and high frequencies. Capable of generating significant sound pressure levels without needing large amounts of electrical power.
Drawbacks: high prices, need for a voltage source, difficulty responding at low frequencies.

Dynamic Speakers
I think it wouldn’t be wrong to say that these are the most widely used compared with the previous types. Their construction (broadly) is based on a coil that produces force on the diaphragm when an electrical current flows through it.

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The diaphragm, elastically suspended, will move, generating a pressure wave.
The voice coil is usually formed by aluminum or copper turns, using a flat wire that gives us excellent conduction.
As for the diaphragm, as you already know, if the speaker is intended to radiate low frequencies its cone will have a large surface area.

We could evaluate the purchase of our speakers according to:

- Their electrical impedance: which can be defined as the natural opposition the speaker presents when it is “driven” by an electrical current. In a speaker, we want the impedance peak to be as high as possible for good performance. (Measured in ohms.)

- Their power: distinguishing electrical power on the one hand and acoustic power on the other. The first tells us the amount of power the speaker can absorb before being damaged.
As for acoustic power, as a quick summary for reference, we could measure sensitivity by checking the amount of sound pressure a speaker produces at a distance of one meter with one watt of excitation.

- Sensitivity:
Above 100 dB, high (public address)
Between 100 and 90 dB, medium (monitors)
Below 100 dB (hi-fi systems)

- Their directivity. Logically, this characteristic defines how the speaker distributes its radiation in space. Manufacturers usually include polar plots from which we can see the directivity of the product we are buying.
So as not to complicate this tangled chapter too much, here are a few somewhat “rough” observations that could help us understand directivity.
We could say that a woofer would have the widest directivity, while a tweeter, on the contrary, would have the narrowest; for this reason, we should aim the highs toward the listening position so that the listener doesn’t lose these frequencies.
In short, I think a speaker with reasonably uniform directivity across frequencies toward the front and with minimal side and rear radiation, to avoid unwanted reverberation, would be desirable.

- Distortion. What can I tell you about distortion? We all know this unwanted element screeching out of our speakers and making us fear, if we let our guard down, their sad demise.
Focusing a bit more on distortion, let me note that, without going into technical explanations, low frequencies are usually the most prone to generating distortion in our equipment. For this reason, when we want a strong low-frequency presence, it’s a good idea to relieve our speakers by using suitable subwoofers (large cones) that take care of giving our bass some “muscle.”

Horn Speakers
We shouldn’t forget the horn speaker. It consists of a motor and (here is its fundamental difference) a rigid diaphragm that radiates into a horn.
Without going on too long, we could underline that horn speakers (for a series of physical reasons relating to the behavior of air, pressure, etc.) give us a greater capacity for low, mid, and high frequency output than a cone speaker of the same surface area.
I don’t have extensive experience working with horn speakers, but we could sum up their advantages as:
a) Wider working range at low and high frequencies.
b) Higher efficiency and sensitivity.

Speaker Cabinets
To reinforce the sound of the low frequencies, speakers are always “mounted” in a corresponding cabinet.

The cabinet has more to it than it seems at first, since inside it a series of movements, reflections, air compressions, and so on are generated that will change the sound of our system, producing very distinct colorations depending on its construction, its interior, the absorbent materials used, whether it is sealed or has air vents (bass reflex), etc.

Conclusions
It’s important to keep in mind that today’s discussion refers to loudspeakers as a whole, since I preferred to devote a second part especially to our studio monitors. Monitors are going to be of vital importance in our home studio, and special care must be taken when choosing and setting up the most suitable ones.

I also believe it is important that we get a basic idea of speakers in general before going into our specific case, monitors. That way we’ll better tell apart the essential differences our studio speakers should have, and the overall picture will be more complete.

To conclude, let me say that there are countless speakers, and in this chapter I have tried to summarize, without too many technicalities, the most important ones and the broadest characteristics we need to keep in mind.