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Old 2nd Mar 2011, 7:28 pm   #45
mhennessy
Dekatron
 
Join Date: Jul 2007
Location: Evesham, Worcestershire, UK.
Posts: 4,241
Default Re: Hacker Speaker Survey

Hi Eamonn,

Thanks for that - it fits in with expectations, which is always nice . And your set was added to the Hacker group database some time back as well. I presume that's it in your avatar?

Perhaps it's time to revise the conclusions:

5" by 8" Loudspeakers:

The Goodmans loudspeaker was the "general purpose" model that was used in many of the larger sets. It is available in two versions: the earlier ones had 3 bolts visible on the rear of the magnet, which was unpainted. These were 30 ohms in the earlier sets (RP10, 18, 30/31/32). This speaker was also seen in early RP25/35/36 sets, but in 15 ohm guise. Later ones, also 15 ohms and also seen in the RP25/35/36 (and by now the RP37), have no bolts and the magnet is painted the same colour as the chassis. The change happened at around the time Hacker switched from germanium to silicon in the AM sections of the set (the handle style also changed around this time).

Later in Sovereign II and VHF Herald production, the Goodmans loudspeaker was replaced by a Celestion speaker (AM-only sets retained the Goodmans). This new speaker has a silver painted chassis and magnet, and "Celestion" is pressed into the terminal board. Roughly, this change happened just before the change from RP25 to RP25A.

Later versions of the Celestion had a black chassis (retaining the silver magnet). These are seen in later RP25B production (no-one has spotted one in a late VHF Herald yet - it's possible that VHF Herald production stopped before the Sovereign - certainly there was never an RP37B).

Note that the Celestion doesn't fit in an AM Herald (RP35) because the switchboard interferes with the slightly larger chassis.

An alternative loudspeaker - an Elac with a large ceramic magnet - was usually fitted to RP37A VHF Heralds instead of the Celestion. The available data suggests that the Elac was the preferred choice for the VHF Herald, with the Celestion being considered a suitable substitute. When this Elac is used, the amplifier PCB is rotated through 180 degrees. And while I haven't tried it, I suspect that this Elac won't fit in a Sovereign II because of the magnet.

There is another Elac, this time with a smaller Alnico magnet and gold-coloured frame/magnet, which was fitted to RP38A Hunters. Early RP38 Hunters used the later Goodmans, but switched to the Elac fairly early in production - but the earliest Elac examples had a grey painted chassis (the magnet was unpainted). There should be an "Elac" sticker on the side of the magnet, but these frequently fall off. These are 15 ohms.

This Elac reappears in the Sovereign IV and RPC1 sets, only it's 4 ohms now - as a result of switching from 18 to 12 volt operation.

Late Bournemouth production Sovereign (IV) and RPC1 sets had yet another loudspeaker - this time with a ceramic magnet. At this stage, I've not taken a close look at it and can't see who makes it. Although the magnet is generally hidden in most internal photographs, you can recognise it from the frame - there is more metal, and more smaller openings in the basket. I will post a photograph and more details in due course.


5" by 7" Loudspeakers:

The Sovereign III family (Black Knight, Super Sovereign, etc) used a smaller 5 by 7" speaker, which has no identifying labels or markings. Luckily, forum member "safria17" asked Hacker at the time, and they told him that it is was made by Peerless. Having recently seen an advert for Peerless loudspeakers in a magazine from the same time, I can only agree - although the advert showed a range of round speakers, the distinctive magnets confirm this.

I didn't notice until recently that the Super Sovereign uses a version of this loudspeaker with a slightly larger magnet.

4" by 6" Loudspeakers:

Many of the smaller sets used a 4" by 6" loudspeaker - the Mini-Herald, the Autocrat (both versions), the Democrat and the Harrier. The earlier sets used a unit made by Goodmans, which was 25 ohms in the Mini-Herald, and 15 ohms in the Democrat. The later Mini-Herald also used a unit made by Rola-Celestion.

The Mk1 Autocrat also used the Goodmans speaker in 25 ohm form. The same speaker was used in many Dynatron sets of the period.

The Mk2 Autocrat and Harrier used different loudspeakers - these had larger magnets and, reflecting the 9V operation, were 5 ohms. There are two different versions; one painted grey, one gold-coloured like the Elac units. At this stage I'm not sure of the manufacturer, or the significance between the different finishes - still gathering data.

Miscellaneous Loudspeakers:

The Ranger and Aviemore sets used a round loudspeaker, about 4 inches in diameter, and I've seen 3 or 4 variants. In general, earlier sets used larger magnets and sounded better. Various models have been seen, including the infamous plastic Philips model in very late production. A model from Audax with a grey painted frame was popular. Unfortunately, they seem to get worse (cheaper?) as production continued.

Later sets (the Consort RP79, Herald RP82 and Knight RP85) use a 4" by 7" model made by Audax. It's not a patch on the earlier Celestion or Goodmans units, but a welcome upgrade from the round speakers mentioned above.

I think that's pretty comprehensive, and should definitely help when buying or repairing sets. Thanks to everyone who contributed data, and please feel free to continue doing so - remember to include serial numbers and I'll be able to add them to the Hacker group database

Thanks again,

Mark
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