The math behind the fit score | boombox.iamgmb.com

Usable baffle

A case face is a rectangle. Drivers are circles. We subtract a border, then pack circles with a gap between flanges.

usable_w = interior_length − 2 × border
usable_h = interior_width  − 2 × border

cols = floor((usable_w + gap) / (flange_od + gap))
rows = floor((usable_h + gap) / (flange_od + gap))
count_per_face = cols × rows

Parameter	Direct to shell	Face plate	Why
Border	0.75″	0.30″	Wall radius, latch ribs and bolt land on a bare shell; a plate spans the opening.
Gap between flanges	0.25″	0.20″	Room for two bolt heads and a driver's terminal.
Flange, 6.5″ class	7.1″	7.1″	Typical steel frame. Cast frames run to 7.4″.

This is a packing estimate, not a CAD layout. Real baskets have terminals, cast ribs and non-circular frames. Use the count as the ceiling, then lay it out full size before cutting.

Depth budget

usable_depth   = interior_depth − electronics_reserve     (default 2.0″)
per_side_depth = usable_depth / sides                        (1 for one face, 2 for front + back)

fit if driver_mounting_depth ≤ per_side_depth

The electronics reserve is editable in the code, not in the UI yet. Two inches covers a 2.1 board, a pack and wiring in most builds; a build with a big lead battery needs more.

Air volume

gross_in3 = (L_in × W_in × base_depth_in)
net_in3   = gross_in3 × (1 − stuffing%) − (drivers × 36.6 cu in) − 30.5 cu in amp

Base depth is used where published, because the lid is shallow and usually holds the amp. Where only total depth is published, total depth is used and the result is optimistic. Volume is a sanity check against Vas, not a tuning model.

Fit score

Six criteria, each scored independently, then normalized over the ones that could be evaluated. A criterion with missing data is excluded from the total rather than scored zero — and listed as unscored.

Criterion	Max	Rule
Physical fit	15	Flange fits the usable face and mounting depth clears the budget. Binary.
Supply voltage	30	Full marks when the pack sits at least 3 V inside the board's window; 20 near a rail; 0 outside it.
Load impedance	15	Parallel load per channel at or above the board's minimum. Below it, 0.
Power ratio	20	Derated board watts ÷ driver RMS. 0.7–1.6× scores 20; 0.4–0.7× or 1.6–2.5× scores 10–12; beyond that, 0–5.
Enclosure volume	20	Net volume ÷ Vas. 0.5–2.0× scores 20; outside that, partial credit with a warning.
Battery current	—	Informational: draw at full tilt vs the BMS continuous rating.

Bands: 85–100 excellent, 70–84 workable, 50–69 needs changes, below 50 will not work as drawn.

What the score cannot see: frequency response, port or radiator tuning, cabinet resonances, thermal rise, Bluetooth range, and whether the box sounds good. It is a compatibility filter.

Data policy

Transcribed, not invented. Every dimension comes from a manufacturer page or datasheet fetched at build time. Where a figure is not published, the field is null and the cell renders as a dash.
Amazon links are verified or downgraded. Each ASIN was opened and its title matched to the product. Where Amazon blocked the check or the title did not match, the link is a search URL for the exact product name instead of a guessed ASIN.
Prices are snapshots. The date at the bottom of every page is the build date; a price from that date is not a quote.
Manufacturer page wins. If a maker revises a driver mid-run, the maker's page is correct and this table is stale. Tell us and it gets fixed.