MEH — single-file editor

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MEH / Lab Build 13.1 · Assisted design

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Entry / cone overlap—
Cone / entry area—
Straight-line path spread—
Design analysis
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VariantEntry
mm / shape		Offset / gap
mm		Projected
overlap		Path spread
mm		Front air
cm³ estimate		Compression

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Experimental tool.

Acoustic predictions still need validation. Check your design before building.

Built using AI tools.

What the editor measures

This is a parametric geometry tool with a reduced linear acoustic circuit for the cone-mid branches. It is not a BEM/FEM field solver, a polar-response predictor, or a manufacturing CAD kernel. Candidates are ranked within this reduced model; they are not validated loudspeaker designs.

Manual and Assisted share the left panel. Assisted starts from its own clean baseline and selected drivers, without carrying over manual dimensions. It derives a starting horn size and searches entry location and area, driver placement, rear volume and rear vent dimensions against the chosen frequency band and voltage. Only drivers with complete reviewed motor data support acoustic recommendations. A bounded search rejects mechanical failures, nonphysical model results and excursion violations, then ranks modeled horn-mouth output, variation and air speed. Cancellation or failure preserves the current horn; Undo restores the preceding design.

The one-dimensional horn network includes complex frequency-dependent loading and a circular baffled-piston radiation assumption. Alternative mouth and throat terminations show sensitivity, not confidence bounds. Rolled-lip diffraction, transverse modes, actual compression-driver termination, HF crossover and rear-port/horn far-field summation require further modeling or measurements.

Functional controls

The design sidebar changes the horn, entries, inspected driver models and rear enclosure. Choose one shared chamber or individual pods, then sealed or ported loading. The shared chamber can be cylindrical or curve continuously from the rolled horn rim around the driver envelopes. Its shape sets the volume and rear-panel position; the air space remains connected. Frequency, excursion, sound speed and T/S inputs live in a separate calculation panel and update the displayed screening estimates. View switches appear only in views where they work.

Hold entry area constant couples entry length and width while changing shape. If a requested dimension cannot preserve that area within the allowed bounds, the dimension is constrained. Manual edits always update the geometry. Coupling and chamber checks appear as advisories, and saved/exported studies retain their validation messages. Driver placement and rear-port fitting run only when requested. Assisted and acoustic screening still reject unsupported geometry. The complete entry must project inside the equivalent active piston for this straight collector model. This conservative geometric rule is not proof of an acoustic alignment. Selecting a port-size study row intentionally starts a new, unlocked area comparison.

Parameter directions

Offset follows the horn-wall tangent; standoff is normal to the wall. Slot rotation is along the wall at 0° and around it at 90°. At 0°, the broad teardrop end points toward the mouth. The nominal horn angle is a profile parameter, not a measured beamwidth.

Curvature and entries

The R-OSSE rev7 equations generate the actual meridian. Mouth diameter, nominal angle, throat opening and the five shape parameters are independently editable. Entry outlines are numerically intersected with the forward horn surface. Edge distances are sampled 3D distances, so they include the finite opening size rather than only its center.

Alignment and paths

The equivalent piston radius comes from Sd. The footprint view projects the entry along its axis onto the mid mounting plane. Its overlap percentage is a geometric description, not a quality score. Path and volume calculations use a conical surrogate; the more detailed rendered cone, surround and dust cap are illustrative. Cone depth has not been measured on the B&C driver. Minimum and maximum straight-line distances run from that surrogate to the entry center. Their phase equivalent uses 360° × ΔL / λ. Actual sound propagation is not a set of independent rays and may differ substantially.

Offset-outlet insert

The offset-outlet option follows the cone surrogate while leaving a passage aligned with the projected horn entry. Its opening retains the entry shape and rotation, can be enlarged with Opening size (equivalent diameter), and includes a 2 mm edge allowance. It moves with driver offset. Center relief lowers the cone-facing apex to form a flat dust-cap recess; its default depth is an editable assumption. The mesh is conservatively below the assumed cone surface, and section and volume use that same mesh. Real cone, dust-cap and surround dimensions must be checked before fabrication. This geometry study has no narrow-gap acoustic model.

Annular insert

Manual can add an annular volume filler attached to the mounting land. Its cone-facing surface follows the editable conical surrogate at an axial clearance of 1–4 mm. The collector meets the insert opening directly, avoiding a wide cavity followed by an abrupt restriction. The opening widens to preserve the complete projected horn entry with a 2 mm edge allowance and a central keepout of 35% of the equivalent piston radius. These are explicit modeling assumptions. The same closed triangle mesh supplies both the rendered insert and its displaced volume. It fills part of the cone recess and mounting land; the collector now transitions directly into that opening. Its reduced air volume is included in the front-air estimate. No equal-path phase plug, real dust-cap/surround fit, narrow-gap flow model or insert-enabled acoustic prediction is claimed. Use actual peak excursion and measured diaphragm geometry before fabrication.

Volume and velocity

Front air combines the matched triangulated collector volume, polygonal neck and cartridge allowance, and a simple cone-recess estimate. The collector shares the exact entry outline at its small end and follows a smooth transition to the driver cutout or enabled insert opening, with zero endpoint slope at the straight neck and mounting land. The exterior has no intermediate cartridge caps. The complete adapter wall has closed annular returns and an embedded horn joint. An enabled insert is integrated into that wall boundary, without overlapping seat faces. With an insert, the passage meets its opening directly; rendering, sections and collector volume use the same boundary. Entry tube length controls the narrow passage; the model adds a fixed 3 mm allowance. Driver standoff controls the whole assembly depth. The volume calculation follows that rendered mesh. It omits the real dust-cap and surround geometry. The velocity proxy is 2πf × cone peak excursion × Sd / port area; it assumes the piston volume flow passes through the opening without compliance storage. It is not a measured port velocity or an SPL rating.

Mechanical fit

Driver and pod overlaps use convex cylinder envelopes and GJK. An envelope overlap may be a false alarm because the real basket is open or tapered. The frame-to-wall value is a sampled rim-to-profile distance minus nominal wall thickness. Representative sockets, flanges, gaskets and fasteners help explain assembly. They are illustrative and are not tolerance-checked manufacturer CAD; wiring and terminals remain omitted. Browser geometry is not a replacement for a detailed CAD interference check.

Wavelength and sealed-box proxies

λ/4 is displayed as a length reference, never as a pass/fail condition or a predicted cancellation notch. The rear-only sealed-box estimate uses Fs√(1+Vas/Vb) and Qts√(1+Vas/Vb); the front chamber and horn are excluded. Ported loading uses a separate compliance-and-vent acoustic circuit with an assumed vent loss. A shared enclosure has one common air volume and one physical vent carrying the combined mid-driver flow. Chamber modes, radiated rear-port SPL and front/rear interference are not solved.

Starting values

A visual example: B&C 6NDL38 × 4, BMS 4594HE, 700 mm mouth, 60° nominal angle, rolled R-OSSE, one curved shared sealed rear chamber sized to fit the assembly and a 700 Hz probe reference. Entry diameter ≈ 45.8 mm; axial position 147 mm. These editable values are not a finished acoustic design.

References

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