Learn

The quantities a box design depends on, each explained on its own: what it means, what it does to your design, and what it costs you elsewhere. Every one of these opens in the workspace too, by clicking the name of the thing you are looking at.

• Baffle step

  A real cabinet loses 6 dB of bass that a half-space simulation gives you for nothing.

• Bandpass: the driver is sealed inside

  Two chambers with the driver between them, and only the port is heard.

• Bl: force factor

  The motor strength, in tesla-meters; the force produced per ampere of coil current.

• Box losses: Ql, Qa and Qp

  How much energy the enclosure leaks, absorbs or loses in the port, as Q factors; higher means less loss.

• Double tuned reflex: two chambers in series

  A vented box whose port feeds a second vented chamber, giving two tunings instead of one.

• Drive level

  The amplifier voltage the simulation assumes, conventionally 2.83 V.

• Driver size: what the inches mean

  The nominal size is a rough label. Sd and Vas are what the design actually depends on.

• Drivers: what adding more buys

  More drivers give more output and want a bigger box, in fixed proportion.

• F3, F6 and F10: how deep it goes

  The frequencies where output has fallen 3, 6 and 10 dB below the passband.

• fs: free-air resonance

  The frequency at which the moving cone and its suspension resonate in free air, in hertz.

• Group delay

  How long a frequency is delayed passing through the system, in milliseconds.

• Hofmann's Iron Law

  Efficiency, box size and bass extension, you may choose two, never all three.

• How well is this actually known?

  Published parameters describe one sample of a production run, so the honest answer is a band, not a line.

• Is this design any good?

  Where your box sits among the alternatives your driver allows, and what it traded to get there.

• Isobaric: two drivers, half the box

  A pair of drivers mounted one behind the other, moving as one, needing half the cabinet.

• Net and gross volume: two different boxes

  The volume the physics uses is the air inside. The volume you cut panels for is bigger.

• Passive radiator: a port with a suspension

  An undriven cone that does the port's job, tuned by its mass rather than by a length of tube.

• Port ends: why the same tube tunes differently

  How each end of the port is terminated changes its effective length, and so its tuning.

• Port tuning: fb

  The frequency at which the port and the box air resonate, in hertz.

• Qes and Qms: where the damping comes from

  The electrical and mechanical halves of the driver's damping at resonance, both dimensionless.

• Qtc: system Q in a sealed box

  The total damping of the driver once the box air spring is added, dimensionless.

• Qts: total Q

  Total damping at resonance, dimensionless; combines the electrical and mechanical losses.

• Re: the voice coil's DC resistance

  The resistance of the coil itself, in ohms. Re is a measurement; nominal impedance is a label.

• Sd: effective cone area

  The effective radiating area of the cone, in square meters.

• Sealed versus vented

  What the two enclosure types actually trade against one another.

• SPL: how loud, and under what conditions

  Sound pressure level in decibels. Sensitivity is efficiency plus an impedance term, not efficiency on its own.

• The box is overdamped

  A Qtc below 0.5 rolls off earlier than it needs to, trading extension for damping you cannot hear.

• The box is small for this driver

  F3 has ended up well above the driver's own free-air resonance.

• The cone unloads below tuning

  Below fb a vented box stops controlling the cone, and excursion runs away.

• The port is chuffing

  Air moving through the port faster than about 17 m/s starts to be audible as noise.

• The response is peaking

  A Qtc above 1.0 puts a bump before the rolloff and leaves the bass overhanging.

• This is a hard load for an amplifier

  The minimum impedance has fallen below about 3.2 ohms.

• Vas: equivalent compliance volume

  The volume of air with the same springiness as the driver's suspension, in liters or cubic meters.

• Wiring: series or parallel

  How several drivers are connected sets the impedance the amplifier sees, and the level you get.

• Xmax: linear excursion limit

  How far the cone can move in one direction while the motor stays linear, in millimeters.