Vintage ScanSpeak 21W-3804-P2A + D3804
Copyright 2009 Troels Gravesen
       


EXPERT no-name speaker of the Seventies.

An 8 USD purchase from a local second-hand store reveals vintage ScanSpeak drivers from the Seventies. Possibly only of interest to the very few, but the D3804 drivers here were in absolute mint condition and it would be interesting to see how they performed compared to the modern ScanSpeak D3806/8200 used in my SP38/13 construction. These no-name speakers were made in the town of Horsens for the (former) Danish EXPERT chain store. 21W-3804-P2A drivers in mint condition, revealing diecast baskets, alnico magnets and paper pulp cones with a coated paper half-roll surround, actually cone and surround moulded in one piece. Quite unusual and - possibly not that easy to do.

With the small closed box used here, we're into a no-deep-bass design, targeting book-shelf placement and driven by the common tuner-amp integrate of the Seventies, a "radio". These speakers were made under serious economic constraints and most noticeable here by looking at crossover components, i.e. tiny coils and electrolytic caps.
The mid and tweeter are basically driven in parallel with different points of roll-off, providing a decent flat response of upper octaves. The bass driver doesn't even have a low-pass filter, thus depends on its inherent upper roll-off.

The bass driver cone is made from long-fibre paper pulp, today only found in the ScanSpeak 18W/8542-00 driver - and not to forget, the JA8008. To my ears, a cone material that can deliver excellent midrange quality. The voice coil is wound on a 38 mm aluminium former ensuring good power handling compared to coils wound on the usual paper former of that time. The driver display a nice smooth response only up to 800 Hz, from where a steadily decline is seen. Why this is so is a hard to tell, but the surround, a relatively weak magnet and lack of dust cap may all play a role. Mms should not necessarily count for an early roll-off.

 

The Peerless mid features a closed back made from rather resonant metal, creating high Fs and a huge bump in response at 1200 Hz. It could possibly be used as tweeter alone, reaching even higher that the D3804 dome. Crossed at e.g. 3 kHz it might not do bad at all.

The D3804 domes are quite sensitive displaying some 92-93 dB/2.8V/1m and with a little creativeness, a two-way system can be modelled with a decent flat response up to 16-18 kHz as can be seen below.

Is it worth while? If you really fancy old drivers, yes. Make an e.g. 30 liter aperiodic cab, drivers driven from the crossover seen below - and I'm sure you can have some fun hours. As a replacement for modern drivers? Forget it. We can get modern driver with s much better response profile making crossover construction much easier.

Measurements


L: SPL/2.8V/1m of ScanSpeak 21W-3804-P2A in EXPERT cab. R: System sensitivity at 1m/2.8V.


L: Blue = Peerless middriver, 2.8V/1m. Red = D3804, 2.8V/1m. R: System impedance.

The Crossover


I wonder who made this crossover! Bottom line is a decent flat response from final system.


The drivers


New crossover for a 2-way SS

Measurements 21W-3804-P2A and D3804


Left: Response from two 21W-3804-P2A drivers on 30x50 cm front panel placed 20 cm from top. Right: 2 x D3804 on 30 x 50 cm baffle.


Left: Impedance of two 21W drivers in free air and 33.4 L test cabs. Right: Impedance of two D3804 tweeters.


TS data 21W-3804-P2A.