Adrian Chen

Nakamichi S‑1A / S‑1B Speaker Spec Sheet

AudioTeardown

Identity

The S-1A and S-1B are the left and right speakers of Nakamichi’s RS-1 “Auxiliary Music System,” a compact system dated 1988. No official Nakamichi spec sheet for the speakers has been found online, so this sheet combines forum-quoted service-manual details, seller listings, and a hands-on teardown of this pair.

Item Detail Confidence Source
Model S-1; cabinets marked S-1A and S-1B as a left/right pair. One forum post calls it “SP1.” High WorthPoint listing
System RS-1 Auxiliary Music System, dated 1988 Medium-high HiFi Engine
Companion units R-1 AM/FM receiver (14 W per channel at 10% THD) and CP-1 CD/cassette combo player High Tapeheads
Production span About 1988 into at least 1990 (one CP-1 unit is marked July 1990) Medium SpenCertified
Country of manufacture Taiwan R.O.C., confirmed from this pair’s back label (matches two eBay listings) Confirmed eBay, eBay
Intended orientation Upright, tweeter above woofer (5.5” W x 9” H). I run this pair on its side to fit under my monitors, woofers outward and tweeters inward. Confirmed WorthPoint listing

Drivers

A 2-way design: a roughly 4.5” paper-cone woofer rated 8 Ω / 15 W and a 2” cone tweeter rated 8 Ω / 6 W, both generic OEM units with stamped steel frames. Ratings and part numbers below are read from the magnets of this pair; sizes combine the service manual quoted on Tapeheads with inspection.

Spec Woofer Tweeter
Type Paper cone, zinc-plated stamped steel frame Small cone with center cap (not a dome), stamped steel frame
Nominal size About 4.5” frame (service manual: 5”; listings: 4”) 2” (service manual); measured: 52 mm round frame, 74 mm overall with ears, 48 mm baffle cutout
Impedance (stamped) 8 Ω 8 Ω
Power rating (stamped) 15 W 6 W
Part number (stamped, partly legible) Begins “4002…” 4001286138D
Mounting 4 screws, square frame, no gasket 2-ear bracket, 2 screws, foam gasket
Connections Push-on spade terminals Push-on spade terminals
Wiring Red and black leads White (through the crossover capacitor) and black leads
Tweeter fits a 48 mm hole; slots sit 65.06 mm apart Front view of one tweeter, measured with calipers, in millimetres
74 mm overall, ear tip to ear tipØ52 mmframe body65.06 mm, slot center to centercalculated from the 59.58 and 70.54 mm readings
  • Ø48 mm hole in the baffle (calipers read 47.62, 47.82 and 48 mm; 48 taken as true)
  • Mounting slot, 5.48 × 3.94 mm, long side along the ears

Stamped on the magnet: 8 Ω, 6 W, part no. 4001286138D

Not yet measured: depth behind the flange and cone diameter. Ear width, cone and dust cap are drawn schematically.

The tweeter has a 52 mm round frame with two slotted ears and sits in a 48 mm hole in the baffle. The slots are 65.06 mm apart, so a replacement needs the same mounting pattern or an adapter.

Crossover

The entire crossover is one 3.3 µF / 50 V bipolar electrolytic capacitor in series with the tweeter; the woofer runs unfiltered. This was confirmed by inspection of this pair.

Item Detail
Topology First-order (6 dB/octave) high-pass on the tweeter only
Component Bipolar (non-polarized) electrolytic, marked “3.3 MFD 50 WV” (MFD = microfarads)
Location Soldered to the back of the rear terminal plate; the white tweeter lead is crimped to it
Nominal crossover point About 6 kHz, assuming a flat 8 Ω tweeter load
Woofer filter None; the woofer rolls off naturally
Level matching (L-pad) None
Impedance compensation (Zobel) None

fc=12πRC=12π·8 Ω·3.3 µF≈6.0 kHz

The real crossover point differs because a tweeter’s impedance isn’t a flat 8 Ω. A like-for-like restoration part is a 3.3 µF polypropylene film capacitor rated 100 V or more. The capacitors are branded Luxon. Measured on this pair with a V79 multimeter, with the tweeter lead disconnected: S-1A about 4.3 µF and S-1B about 4.43 µF, both roughly 30% above the marked 3.3 µF and matched to each other within about 3%. At 4.4 µF the nominal crossover point is about 4.5 kHz, assuming a flat 8 Ω tweeter load.

Cabinet and construction

A front-ported particleboard box measuring 5.5” x 9” x 9”, with an estimated 4–5 L internal volume. Construction details come from the teardown unless a source is linked.

Item Detail Confidence
External dimensions 5.5” W x 9” H x 9” D (WorthPoint) High
Volume About 7.3 L external; estimated 4–5 L internal Estimate
Enclosure Bass reflex, front port, passive 2-way (hifi-guide) High
Material Particleboard (chipboard), not MDF High
Front baffle Particleboard, removable via 4 corner screws, black outer trim High
Port Round, front-mounted, cardboard tube High
Damping One pad of recycled-fiber felt on the rear wall, partial coverage High
Seals Tweeter: foam gasket, doubled at the factory. Woofer: none. High
Terminals Removable rear terminal plate with push-on tabs; houses the crossover capacitor High
Hardware Black Phillips pan-head wood screws High
Grille Removable High
Weight One listing claimed 10 lb, unclear whether per speaker or per pair Low

Acoustic performance

No published frequency response or sensitivity figure has been found. What is known: 8 Ω nominal impedance and roughly 15 W power handling.

Spec Value Basis
Nominal impedance 8 Ω Driver labels and listings
Power handling About 15 W, set by the woofer; tweeter rated 6 W behind the crossover Stamped ratings
Matching amplifier R-1 receiver: 14 W per channel at 10% THD Service manual via Tapeheads
Crossover About 6 kHz, 6 dB/octave on the tweeter Calculated from the capacitor
Bass extension Estimated −3 dB somewhere around 70–90 Hz Estimate from driver and box size, not measured
Sensitivity Unknown —
Frequency response graph None published Measure with a mic and REW

Pricing

No speaker-only MSRP has been found; used pairs typically sell for about $35–70.

Item Price Source
Original R-1 + CP-1 system with speakers $750, claimed by one seller (unverified) Audiogon listing
Used S-1A/S-1B pair From about $35 (one eBay listing); $60–70 typical PicClick
Used complete R-1/CP-1 systems About $109–$199 (eBay sales, 2025–2026) HifiShark

Reception

No magazine reviews from the period have been found. Modern owner opinions are split, and condition after 35 years seems to explain much of the difference.

  • Positive: A 2018 HiFi Engine reviewer rated the system very good for its size, with good mids and treble and surprisingly good bass. A 2013 Audiokarma owner who bought the system new about 25 years earlier never wanted to upgrade. A 2016 owner in the same thread found the speakers pretty good given their size and small amp.
  • Negative: In the same Audiokarma thread, one 2010 member called the stock speakers poor, and another heard them distort at higher volume but suspected his pair had been abused. A 2018 member called them poor too, though his receiver may have needed new capacitors.
  • Context: A 2006 Retro Thing post noted that compact systems like this were once a sign of sophistication and expense.

Don’t confuse with

Several similarly named Nakamichi products show up in searches and listings.

Name What it is
Nakamichi Speaker 1 Gray speaker from a different compact system (Compact Receiver 1 + CD Cassette Player 1); one set dated December 1991, listed as made in Japan. Similar 9 x 9 x 5.5” size; its relationship to the S-1 is unconfirmed.
Nakamichi Receiver 1 Full-size 80 W per channel receiver, unrelated to the tiny R-1
Modern Nakamichi products Soundbars and car audio sold under the brand name. The original company entered bankruptcy protection in 2002 after being acquired by Hong Kong’s Grande Holdings in 1998 (Wikipedia).

This pair

Bought on eBay; both speakers work, sound clear, and remain completely stock. Notes from the teardown:

  • Woofer surrounds intact, with no foam rot.
  • Minor cosmetic damage to the outer shell.
  • Some baffle screws have surface rust, suggesting past humidity. Check cabinet edges for swelling; reuse screws after wire-brushing and tighten gently into the particleboard.
  • Tweeter foam gasket is doubled; woofer has no gasket.
  • Damping felt covers only part of the rear wall.
  • Original Luxon 3.3 µF / 50 V bipolar capacitors in place; both measure about 4.3-4.4 µF (see Crossover). One tweeter was damaged during teardown: a dented center dust cap and crushed paper along the outer cone edge. Replacement is under consideration.
  • Current setup: onboard Realtek audio or a UGREEN USB DAC into a Nobsound NS-06G amp. Swapping the DAC made no audible difference.

Open questions

  • Read the back label for country of manufacture, power rating, or a date code
  • Confirm intended orientation from the grille badge
  • Read the full driver part numbers
  • Measure internal dimensions for an exact box volume
  • Measure port diameter and length to calculate tuning
  • Measure frequency response (measurement mic + REW) and impedance

Upgrade notes

  • Restoration: Replace the original capacitor with a 3.3 µF polypropylene film capacitor rated 100 V or more; bag the original.
  • Full modern rebuild: The Overnight Sensations kit uses a HiVi B4N 4” woofer and Dayton ND20FA-6 tweeter in a 4.5 L box tuned to 53 Hz with a 1-3/8” x 6” port (SoundImports). Its 9” x 6” x 8-3/8” cabinet (Parts Express) is nearly the same size as the S-1. Building it on a new baffle and terminal plate would keep the original parts intact and swappable. Expect more bass than stock.

Sources