Joseph Crowe
Speaker System No.2314 --- Wide Baffle BLH plan set -- Fostex FE106NS
Speaker System No.2314 --- Wide Baffle BLH plan set -- Fostex FE106NS
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Design Update — Revised Plans Coming Late 2026
The Fostex FE108NS 4" full-range driver originally specified for this design has now been discontinued. We are currently revising the speaker to use a commercially available full-range driver while preserving the original design objectives, cabinet format and performance characteristics. Updated plans are expected to be available in late 2026.
This DIY plan set includes the detailed drawings required to construct this wide-baffle back-loaded horn loudspeaker. The files are delivered automatically by email after purchase.
The speaker was designed by Troy J. Crowe using acoustic simulation software together with extensive measurement, listening evaluation and prototype development.
The original design uses the Fostex FE108NS 4" full-range driver, selected for its combination of sensitivity, transient response and overall sound quality. Because the FE108NS has now been discontinued, the current plan package should be considered the original or legacy version until the revised driver specification is released.
Original Design Specifications
- Designed for small to medium-sized listening rooms
- Near-field listening or listening distances of approximately 2.5m or less
- Well suited to low-power tube amplifiers such as 300B and Type 45 amplifiers
- Optimized around an average listening level of approximately 75dB
- Wide-baffle configuration
- Back-loaded horn enclosure
- Relatively simple construction
- 12mm Baltic birch plywood construction
- Very high sensitivity, approximately 92.5dB through the 70Hz region in-room
- Bass extension to approximately 40Hz
- Expected cancellation dip of approximately -12dB at 145Hz
Included in the Plans
- PDF drawing package
- Assembly drawing
- Detailed component drawings
- Nested plywood cutting layouts
Assembly Drawing
Detail Drawing
Nested Cutting Layout
Two sheets measuring 762mm × 1524mm (30" × 60") are required per speaker.
Efficiency Comparison
The following measurements are calibrated for approximately 1 watt of amplifier power and provide useful context for the sensitivity of several different loudspeaker systems:
- Markaudio CHR120 in a 1 cu. ft. bass-reflex enclosure — 75.5dB
- Signet SL16 two-way stand-mount loudspeaker with SEAS 6.5" woofer — 76.0dB
- Fostex FF165WK in a transmission-line enclosure — 90.0dB
- Speaker No.1630 with dual 5" Scan-Speak 4-ohm woofers wired in series — 89.5dB
