Speaker No.1630 Plans

Speaker No.1630 was developed as a compact floorstanding loudspeaker with a strong emphasis on resolution, coherency and clarity. Its relatively modest driver complement allows the system to retain much of the immediacy and point-source presentation associated with high-quality full-range loudspeakers while extending low-frequency performance through dedicated woofers.

The design provides a highly dimensional soundstage with excellent image focus and a naturally full tonal balance. Particular attention was given to avoiding the forward or "shouty" character sometimes associated with full-range driver systems, resulting in a presentation that remains lively and detailed while maintaining tonal richness.

See our YouTube video on Speaker No.1630 .

The original plan package includes the PDF assembly and detail drawings required to build this compact floorstanding loudspeaker, together with the passive crossover schematic.

Please note: the original plans specify discontinued Fostex drivers and should therefore be considered a legacy version until the revised driver package and crossover are released.

Plan Package Includes

• Plans priced in USD
• PDF plans automatically emailed after purchase
• Assembly and detailed construction drawings
• Passive crossover electrical schematic
• Construction based primarily on simple right-angle cuts

Original Design Features

• Compact footprint: 214mm wide × 900mm tall × 202mm deep
• Double-layer stepped front baffle
• 12mm Baltic birch plywood construction
• Dual passive-radiator system
• Separate enclosure for the full-range driver
• Original 4" Fostex FE108NS full-range driver — discontinued
• Dual 5" Scan-Speak woofers
• Original frequency response approximately 40Hz–19kHz
• Original optional T96A super tweeter extension above 30kHz — discontinued
• 90dB sensitivity at 2.83V / 1m
• 8-ohm nominal impedance

The original driver and crossover component kit is no longer recommended because the Fostex FE108NS and T96A are discontinued. A revised component specification will be published with the updated plans.

Original specification sheet: view PDF.

Application

Speaker No.1630 was specifically developed for near-field listening at low to moderate levels, with an intended listening distance of approximately 2m or less. The tonal balance was deliberately tuned to remain full and engaging at these lower playback levels.

The bass and mid-bass regions were voiced approximately 4dB above a conventionally flat alignment, providing a form of passive loudness compensation. The original system was optimized around a typical listening level of approximately 75dB while retaining the ability to reach substantially higher levels when required.

In the original configuration, the system was capable of approximately 90dB SPL at 1m while maintaining very low measured distortion across much of its operating bandwidth. Piano, acoustic instruments and vocals particularly benefit from the system's combination of body, transient clarity and point-source presentation.

Speaker No.1630 was designed for listeners who appreciate the coherency of a full-range driver but want greater bass extension, lower distortion and a more balanced tonal presentation than is typically possible from a single driver operating alone.

Original Full-Range Implementation

The original design used the Fostex FE108NS as the primary midrange and high-frequency transducer. Its lightweight cone and strong motor structure provided excellent transient response and a lively, immediate presentation through the vocal range.

The full-range driver operates in its own enclosure with a rear-facing passive radiator. Internal diffraction-control panels are used to reduce internal standing-wave effects and improve midrange clarity.

Dual 5" Scan-Speak woofers operate into the mid-bass region, reducing the amount of low-frequency energy demanded from the full-range driver. This arrangement also minimizes the need for conventional baffle-step compensation and allows the full-range driver to operate without crossover components directly in its signal path.

Original Optional Super Tweeter

The original system could also be fitted with the Fostex T96A super tweeter. Its purpose was not simply to extend the measured bandwidth above 20kHz, but also to increase upper-treble off-axis energy and perceived soundstage width.

The T96A is now discontinued and will not be specified in the revised version of Speaker No.1630. We are evaluating currently available alternatives as part of the late-2026 design revision.

Construction

Speaker No.1630 was intentionally designed to be approachable for DIY construction. The enclosure can be built primarily using simple right-angle cuts, without the complex compound angles required by many high-end loudspeaker cabinets.

One stereo pair can be produced from approximately one sheet of 12mm plywood measuring 48" × 96" (1220mm × 2440mm), making the project particularly suitable for builders with relatively modest workshop equipment.

Fostex FE108NS — Original Specification

The original Speaker No.1630 used the Fostex FE108NS, which followed the limited-production Fostex SOL series. The FE108NS incorporated a copper cap on the pole piece for reduced distortion together with a treated cloth pleated surround, dual-layer paper cone and additional damping behind the dust cap.

The FE108NS has since been discontinued. The revised Speaker No.1630 plans will specify a commercially available replacement and any corresponding enclosure or crossover changes required to maintain the design's intended performance.

Scan-Speak Discovery 15W/4434G-00

The dual Scan-Speak woofers provide the system with relatively high sensitivity while maintaining a tube-amplifier-friendly nominal impedance. Bass extension reaches approximately 40Hz in the original design.

These Danish-made woofers incorporate aluminum demodulation rings to reduce motor distortion. Our original testing measured intermodulation distortion through the bass region at approximately -50dB, or 0.30%, at levels up to approximately 90dB SPL at 1m.

Passive Radiators

Passive radiators are used instead of conventional vent tubes, avoiding port turbulence and reducing several of the dimensional constraints associated with conventional bass-reflex ports in a cabinet of this size.

Fostex T96A Super Tweeter — Original Optional Specification

The original plans included a crossover network for integrating the optional Fostex T96A super tweeter. The T96A extended the system's measured bandwidth beyond 30kHz and increased off-axis energy in the upper treble, contributing to a wider perceived soundstage.

The Fostex T96A has now been discontinued. A currently available replacement, together with an appropriate crossover network, is being evaluated as part of the Speaker No.1630 revision scheduled for late 2026.