Does this design meet the target?
Port calculator
Comparison builds
Group delay, explained simply
Group delay describes how the timing of signal variations changes across bass frequencies. A value of 20 ms at 30 Hz is about the behavior near 30 Hz; it is not a 20 ms delay of the entire song.
The enclosure and crossover filters both contribute. A resonance may create a rise in response and a rise in delay. The number alone cannot tell you whether bass will sound “tight” or “slow”; the room and the rest of the system also matter.
A cycle is one complete vibration: 50 ms at 20 Hz, 25 ms at 40 Hz, and 10 ms at 100 Hz. In cycle mode, the target in milliseconds changes with frequency. Colors mean within target, near target, or above target—not audible versus inaudible. Negative delay, if present, is labeled separately.
Box designer & wood cut plan
Model, assumptions & references
This version uses a coupled electrical, mechanical and acoustic lumped-element model. Box compliance and the lossy port load the same driver motion used for pressure, excursion, impedance and airspeed. Identical drivers share one chamber and move in phase. All-series and all-parallel wiring are supported.
Fs, Qts, Qms, Vas, Sd and Re define a consistent parameter set. Cms, Mms, Qes and Bl are derived; Le is modeled as a simple series inductance. Qms, box leakage Ql, and port loss Qp must be entered or accepted as estimates. A supplied Qes from an imported database is used to derive Qms when possible.
SPL is a small-signal half-space estimate at 1 m, with coherent cone and port output, no room gain, no propagation delay, no thermal compression or nonlinear turbulence. “Limited SPL” reduces selected drive voltage as needed to respect Xmax, coil heating and the selected peak port-velocity cap. Port end corrections and the first duct resonance are approximations, especially for slots, flares and bends. The straight duct calculator does not design folded ports.
The default 0 dB reference is the response at 200 Hz. The curve, signed peak/dip values and rolloff crossings all use that level. This normalization moves if the response at 200 Hz changes with tuning or filters. The optional theoretical flat-passband reference uses the same driver and drive with inductance and filters excluded from the reference calculation only; it does not change with Fb or box volume. The plotted response always includes the selected inductance, losses and filters. Ripple is measured only in the user-selected band. −3/−6/−10/−20 dB markers are low-side crossings relative to the selected reference, searched downward from the band’s response peak. A response dip may create multiple crossings; inspect the graph. The frequency sweep is 5–500 Hz. Filters are Butterworth, 12 or 24 dB/octave.
References: Klippel: small-signal parameters · Linkwitz: subwoofer equivalent circuits · Theory of a Speaker in a Vented Box · REW: group delay