Loudspeakers are drivers, an enclosure and the room they end up in

These are listed in the order worth acting on, which with loudspeaker construction and rooms is not the order they are usually presented in.

How a driver makes sound

A driver moves a diaphragm back and forth, and the pressure variations that motion creates in the air are what you hear. Producing low frequencies at useful levels requires moving a large volume of air, which needs either a large cone or a long excursion. This is a physical constraint rather than an engineering shortfall, which is why very small speakers cannot produce deep bass at high levels.

Cone material trades stiffness, mass and damping, and every choice among those three affects a different part of the response. The motor assembly of magnet and voice coil determines how accurately the cone follows the signal, especially at higher excursions.

Why speakers use several drivers

One diaphragm cannot cover the whole audible range well, because the ideal size for deep bass is wrong for high frequencies. Splitting the range between drivers allows each to work where it performs best, at the cost of needing a crossover.

The measurable part is this: the crossover divides the signal by frequency, and its quality and complexity strongly influence how the drivers integrate. Around the crossover frequency both drivers contribute, and the physical distance between them affects how their outputs combine. This is why speaker measurements are taken at a defined distance and angle, and why listening position affects what you hear.

The enclosure is part of the instrument

Sound radiates from both sides of a moving cone, and without an enclosure the two outputs cancel at low frequencies. A sealed enclosure controls the cone with trapped air and gives a gradual low-frequency roll-off with predictable behaviour. A ported enclosure uses a tuned opening to extend output lower, at the cost of a steeper roll-off below the tuning point.

Cabinet walls vibrate and radiate sound of their own, so mass, bracing and damping in the enclosure are genuine engineering rather than packaging. The trade between size, low-frequency extension and efficiency is fixed by physics, and no design escapes all three at once.

Sensitivity, impedance and what drives them

Sensitivity describes how much sound results from a given electrical input, and it varies enough between designs to matter substantially. A less sensitive speaker needs considerably more amplifier power to reach the same level, which is a system consideration rather than a fault. Nominal impedance is a simplification of a curve that varies with frequency, and the difficult parts of that curve are what stress an amplifier.

After the warranty ends, power handling figures describe what a speaker can survive under a defined test signal, not what it needs or what it will sound like. Matching is about the amplifier coping with the impedance curve and delivering enough current, rather than about numbers agreeing on paper.

The room decides more than you expect

Low frequencies have wavelengths comparable to room dimensions, so the room reinforces some notes and cancels others by position. Moving a speaker or a listening position by a modest distance can change bass response more than changing the speaker would. Boundaries reinforce output, which is why placement against a wall or in a corner increases bass and often muddles it.

In the small print, reflections from hard surfaces arrive shortly after the direct sound and affect clarity and imaging noticeably. Because of this, published frequency response measured in a controlled environment describes the speaker rather than your experience of it.

Manufacturer figures are measured under conditions the manufacturer chose.

Judging without listening in your own room

Look for measurements taken under defined conditions, including on-axis and off-axis response, since off-axis behaviour shapes what a room returns to you. Treat single-figure specifications with suspicion, and particularly frequency ranges quoted without any tolerance band attached to them.

Consider size honestly, since deep bass at volume requires displacement and there is no way around that requirement. Plan placement before purchase, because a speaker that cannot be positioned properly will not perform as it was designed to. Where a return period exists, listening at home is the only way to include the room in the assessment.

Everything above, in order of what to do first

1. How a driver makes sound. A driver moves a diaphragm back and forth, and the pressure variations that motion creates in the air are what you hear.
2. Why speakers use several drivers. One diaphragm cannot cover the whole audible range well, because the ideal size for deep bass is wrong for high frequencies.
3. The enclosure is part of the instrument. Sound radiates from both sides of a moving cone, and without an enclosure the two outputs cancel at low frequencies.
4. Sensitivity, impedance and what drives them. Sensitivity describes how much sound results from a given electrical input, and it varies enough between designs to matter substantially.
5. The room decides more than you expect. Low frequencies have wavelengths comparable to room dimensions, so the room reinforces some notes and cancels others by position.
6. Judging without listening in your own room. Look for measurements taken under defined conditions, including on-axis and off-axis response, since off-axis behaviour shapes what a room returns to you.

The takeaway

Decide where a speaker will stand before you decide which one to buy, because the room is part of the product.

Buy for the failure you can live with, not the feature you will use twice.