Everything starts with the driver. Load one from the library, paste a spec sheet, or type the numbers in. The tool works out the rest of the physics from there.
What kind of speaker is this?
Driver library
Paste a spec sheet
Enter parameters
Driver parameters
The three that set box size
Electrical & mechanical
Cone & travel
What the tool worked out
Tweeter
Pick the high-frequency driver
Every enclosure is a trade between size, depth of bass, accuracy and loudness. Tell the tool which of those matters most and it ranks the workable options for your driver.
What matters most for this speaker?
Ranked options
Side by side
The chosen design, with the four checks that decide whether it survives contact with real music: how it responds, how far the cone travels, how fast the air moves in the port, and how loud it goes before something gives.
Enclosure
Drive conditions
Frequency response
How the bass rolls off
Anechoic half-space. The −3 dB point (F3) is where output has fallen to about 70% of the midband — the usual shorthand for "where the bass ends". A room will typically add back several dB below 60 Hz.
Cone excursion vs Xmax
The most important plot here. Cross the red line and the coil leaves the magnet gap: distortion, then mechanical damage. Ported boxes unload badly below tuning — that's the steep rise on the left.
Port air velocity
Air speed in the port. Past roughly 17 m/s it starts to hiss and chuff on bass notes; past 25 m/s it's obvious and the tuning itself starts to shift. Bigger or flared ports fix it.
Maximum SPL — how loud before something gives
Two ceilings at once. The excursion limit is where the cone runs out of travel; the thermal limit is where the voice coil runs out of power handling. The lower of the two is your real ceiling at that frequency.
Numbers
Where you hand over from woofer to tweeter, and what that costs. The component values below are exact for a resistive load — real drivers aren't resistors, so treat them as the design you build and then measure, not the one you ship.
Crossover
Component values
The box as an object. Drag any dimension and the others move to hold the volume — so you can chase a proportion the industrial design needs without ever losing the acoustics. Braces and ports are real geometry here: what you place is what gets subtracted from the air inside.
Dimensions
Bracing ?
Ports
Driver on the baffle
Net acoustic volume is not the box you build. The magnet, the port tube and the bracing all steal air back. Build to the acoustic figure and the finished box comes out undersized — this page adds it all back.
Material
What else steals air
Volume, step by step
Cut sheet
Panel behaviour
Standing waves inside the box
Everything on one card
Speaker design has its own vocabulary, most of it named after the two engineers who formalised it — Neville Thiele and Richard Small. Here's the whole set in ordinary language.
How the tool does the maths
Sealed box. Vb = Vas / ((Qtc/Qts)² − 1) and Fc = Fs · Qtc/Qts.
The response is an ordinary 2nd-order high-pass, so F3 has a closed form and no searching is needed.
Ported box. The response comes from the full 4th-order vented transfer function including box leakage,
with s⁴ + a₁s³ + a₂s² + a₃s + a₄ where a₁ = 1/Qts + h/QL,
a₂ = α + h + 1 + h/(Qts·QL), a₃ = h/Qts + h²/QL, a₄ = h²,
h = Fb/Fs and α = Vas/Vb. F3 is read numerically off that curve rather than
from the usual approximation, which can be a couple of Hz out.
Cone excursion. Derived from real motor parameters: Cms = Vas/(ρc²Sd²),
Mms = 1/(ωs²Cms), Bl = √(ωs·Mms·Re/Qes), and peak displacement
x₀ = e·Bl/(Re·Mms·ω²). In a ported box the cone displacement carries the numerator
s² + (h/QL)s + h², which is why it notches at tuning and runs away below it.
Port. Lv = c²Av/(4π²Fb²Vb) − k·r, with the end correction k set by how the ends are finished.
Air velocity is computed from the port's own volume velocity at the drive level you set, not from a worst-case assumption.
Loudness. Reference efficiency η₀ = (4π²/c³)·Fs³·Vas/Qes, sensitivity
= 112 + 10·log₁₀(η₀) dB at 1 W / 1 m into half space. Maximum SPL is the lower of the
excursion-limited and thermally-limited curves at each frequency.
What it does not model. Baffle step, edge diffraction, room gain and room modes, driver non-linearity, power compression, motor inductance effects above a few hundred Hz, or passive radiators. Real in-room response below 100 Hz is dominated by the room and will differ substantially.