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 |
- 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 |
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 |
Take the speaker apart below. Sizes are drawn to scale from the measurements; each one is tagged as measured, estimated from photos or assumed, and the assumed ones are still being checked.
Pick a part above, or point at it in the drawing.
33 measurements taken, 30 estimated from photos, 41 assumed for now.
Still to measure (71)
- Cabinet wall thickness
- 6.5 mm Estimated from photosThe rim around the rear panel in the ruler photo is about 6.8 mm. A baffle that fits inside walls this thick is 211.44 mm tall, within 0.1 mm of the grille height (211.33), which supports it.
- Baffle screw x from centre
- 53.5 mm Estimated from photos
- Baffle screw y from centre
- 97 mm Estimated from photos
- Tweeter centre height
- 68.6 mm Estimated from photosCentred left to right
- Port centre x from centre
- -40.7 mm Estimated from photosNegative is the viewer's left. This is the S-1B; the S-1A is presumably a mirror image.
- Port centre height
- 40.3 mm Estimated from photos
- Woofer centre height
- -39 mm Estimated from photosCentred left to right
- Grille tab width
- 43 mm Estimated from photosTwo tabs, centred on the top and bottom edges
- Badge height above the grille
- 1 mm Estimated from photosThe badge stands slightly proud of the grille; about a millimetre is a guess
- Badge black piece sunk below the gold
- 0.4 mm AssumedThe black piece is a separate part set a little lower than the gold
- Grille hole pitch
- 1.38 mm Estimated from photosCentre to centre, scaled from a close-up photo against the badge's measured 9 mm width. The holes are square with rounded corners and go right through.
- Grille hole size
- 0.92 mm Estimated from photos
- Badge x from centre
- 56.8 mm Estimated from photosUpper right when upright, about 7 mm in from the grille's right edge
- Badge y from centre
- 95.6 mm Estimated from photosAbout 7.5 mm below the grille's top edge
- Terminal plate size
- 54 mm Estimated from photosSquare, four screws, pebbled black plastic
- Terminal plate screw inset from the corner
- 5 mm Estimated from photos
- Terminal plate bump diameter
- 45 mm Estimated from photosThe round dished recess on the outside is the back of a tapered bump that passes through the rear panel into the box
- Terminal clip x from centre
- 11 mm Estimated from photosSeen from the back, black (minus) is on the left and red (plus) on the right; x here is as seen from the front, so the signs look swapped
- Terminal clip below the plate's centre
- 6 mm Estimated from photos
- Rear label width
- 60 mm Estimated from photos
- Rear label height
- 33 mm Estimated from photos
- Rear label centre height
- -65 mm Estimated from photosCentred left to right, below the terminal plate
- Tweeter magnet cup diameter
- 32 mm Estimated from photos
- Tweeter gasket outer diameter
- 62 mm Estimated from photosFlat white foam ring, doubled at the factory
- Tweeter gasket inner diameter
- 47 mm Estimated from photosAn earlier photo read about 42 to 44; 47 lets the frame's dish through
- Particleboard front panel width
- 129.5 mm Estimated from photosScaled from the photo with the ruler in it; it sits inside the bezel
- Particleboard front panel height
- 218 mm Estimated from photos
- Woofer screw x from the woofer's centre
- 47.5 mm Estimated from photos
- Woofer screw y from the woofer's centre
- 50 mm Estimated from photos
- Terminal plate centre height
- 11.2 mm Estimated from photosCentred left to right and a little above the middle of the back
- Grille sheet thickness
- 0.8 mm Assumed
- Flange inset from the grille's edge
- 3 mm AssumedThe flanges sit inside slots on the front, so they stand back from the edge of the face
- Flange length
- 190 mm Assumed
- Tab inset from the grille's edge
- 3.25 mm Assumed
- Bezel plate thickness
- 3 mm Assumed
- Bezel rim wall thickness
- 2.5 mm Assumed
- Gap between the bezel plate and the drivers' flanges
- 10 mm AssumedThe collars, the port boss and the corner standoffs on the back of the bezel are about this tall; the screw heads sit in the gap
- Bezel collar wall thickness
- 3 mm Assumed
- Bezel corner standoff diameter
- 9 mm Assumed
- Particleboard front panel thickness
- 12 mm AssumedThe baffle screws go about 9 mm into it
- Woofer hole in the particleboard panel
- 100 mm Assumed
- Port gasket thickness
- 2.5 mm Assumed
- Tweeter gasket thickness
- 1 mm AssumedBoth layers, squeezed
- Woofer frame flange thickness
- 3 mm Assumed
- Woofer cone diameter
- 100 mm Assumed
- Woofer basket front diameter
- 96 mm Assumed
- Woofer basket
- 0.75 mm AssumedThe basket is a cone-shaped dish with large windows
- Woofer basket depth
- 38 mm Assumed
- Woofer magnet diameter
- 72 mm Assumed
- Woofer magnet depth
- 24 mm Assumed
- Woofer dust cap diameter
- 34 mm Assumed
- Tweeter depth behind the flange
- 22 mm Assumed
- Tweeter cone diameter
- 46 mm Assumed
- Tweeter ear width
- 10 mm Assumed
- Tweeter flange and ear thickness
- 2 mm Assumed
- Tweeter magnet cup depth
- 8 mm Assumed
- Tweeter frame
- 0.7 mm AssumedThe frame is a cone-shaped dish
- Tweeter dust cap diameter
- 18 mm Assumed
- Port tube length
- 70 mm Assumed
- Port tube outside diameter
- 35.5 mm AssumedGlued to the back of the panel around the 31.75 mm hole
- Rear panel thickness
- 6 mm Assumed
- Rear panel protrusion past the housing
- 2 mm Assumed
- Terminal plate bump depth behind the plate's face
- 28 mm AssumedThrough the rear panel and about 20 mm into the box
- Terminal clip width
- 12 mm Assumed
- Terminal clip height
- 18 mm Assumed
- Terminal clip depth
- 5 mm Assumed
- Damping felt thickness
- 8 mm Assumed
- Damping felt centre height
- 0 mm Estimated from photos
- Terminal plate thickness
- 3 mm Assumed
- Crossover capacitor diameter
- 10 mm Assumed
- Crossover capacitor length
- 17 mm AssumedLies sideways under the bump, held on with glue; leads run to the terminal tabs
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
- HiFi Engine: Nakamichi RS-1
- Tapeheads: CP1, R1 and SP1 mini system thread
- Audiokarma: Nakamichi R1 mini-receiver thread
- hifi-guide: Nakamichi S-1A
- Wikipedia: Nakamichi
- Retro Thing: Nakamichi System One
- Seller listings: WorthPoint, WorthPoint, eBay, eBay, SpenCertified, Audiogon, PicClick, HifiShark, Barnebys, Reverb
- Teardown and inspection of this pair (September 2026)
To the extent possible under law, Adrian Chen has waived all copyright and related rights to this post and its data under CC0 1.0. Quotations and material from the sources it cites remain their owners'.