Speakers
1920s onwardsEverything upstream deals in electricity. The speaker is where that becomes moving air — a mechanical job, in a room, subject to physics that no amount of electronics can route around. It is why two systems sharing every other component still sound different.
How a driver works
A coil of wire sits in the gap of a permanent magnet and is glued to a cone. Send current through the coil and it becomes an electromagnet, pushed or pulled by the fixed magnet depending on the direction of the current.
The cone moves with it, pushing air away and pulling it back thousands of times a second. That pressure wave is the sound. The whole principle is a century old and has not needed replacing.
Why there is more than one
A cone big enough to move the air for deep bass is far too heavy to start and stop fast enough for treble. So the job is divided: a woofer for low frequencies, a tweeter for high, sometimes a midrange between them.
A crossover — a filter network inside the cabinet — decides which frequencies go where. It is a large part of why speakers using identical drivers can sound entirely different, and one of the harder things in the whole chain to get right.
The cabinet is not just a box
The back of a cone radiates sound too, exactly out of phase with the front. Left alone those two cancel each other, and the bass disappears. The cabinet exists to stop that.
A sealed box traps the rear wave and uses the compressed air inside as a spring. Acoustic Research popularised this acoustic-suspension approach in the 1950s, and it is why genuinely deep bass became possible from a bookshelf-sized enclosure rather than a piece of furniture.
A ported box instead lets the rear wave out through a tuned tube, in phase, to reinforce the bass — more output for the size, at the cost of control below the tuning point.
The room is part of the speaker
Most of what reaches your ears indoors has bounced off something. Room dimensions reinforce some bass notes and cancel others, and hard surfaces smear detail.
This is why placement changes sound so dramatically, and why moving a speaker away from a wall often does more than replacing the amplifier. It is the cheapest upgrade in audio and the one people try last.
Names that mattered
Listed because of what they did, not as recommendations. Velorex Music did not make any of these.
Did you know?
- Speaker sensitivity is quoted in dB for one watt at one metre; a few dB difference is worth more than a large power increase.
- Getting a speaker 's two drivers to arrive in step matters as much as the drivers themselves — that is the crossover's real job.
- Bass is the hardest thing to reproduce in a room, and the frequency range most affected by where you stand.
- Cone materials are a trade-off between stiffness, mass and damping; no single material wins on all three.
Remember this?
Speakers were furniture. Big boxes on the floor with fabric grilles that came off to reveal the drivers, positioned by trial and error, and argued about. Taking the grilles off was, and still is, the first thing anyone does.
Sources & further reading
Written from these sources, not copied from them. External links open in a new tab.