Please recommend replacement for Rola 10" Speaker for Bush PB12

[BrianAllen]

I have tried to stop the speaker buzzing/vibrating but unsuccessful, so is anyone able to recommend a suitable replacement please?

Thank you.

Brian

[cathoderay57]

Well the good news is that it's a permanent magnet speaker, and so no energising coil to worry about. I haven't checked the service sheet (you should) but I assume it is a 3 to 4 Ohm speaker. Measuring the dc resistance will show a value less than that; 3 to 4 Ohms is the impedance. So any 10-inch speaker of 3 to 4 Ohms impedance will work fine. You might have to fit the output transformer somewhere on the baffle-board if the transformer mounting holes are absent, or don't line up. Don't be tempted to drill holes in the replacement speaker frame because if you get magnetic swarf into the speech coil, you'll be back where you started. Jerry

[BrianAllen]

Thanks Jerry, great information (as usual).

The cone had cracked part way around the circumference of the speaker and as far as I recall a couple of tears nearer the centre. I repaired the small tears with tissue and PVA and the outer repairs with Copydex.

It's a lovely sounding radio with excellent reception without having to use an external aerial, so will definitely replace that speaker.

Thanks Jerry.

Brian

[BrianAllen]

D.C. resistance of speech coil is 2.5 ohms as per service sheet.

[cathoderay57]

You might struggle to find one that is suitable if you buy new; reason being that most of the 10 inch drivers that I could find on a quick search were woofers and/or rated at 100W+. If you used one of these, while it would work, it would lack sensitivity and higher frequency response, albeit the Bush AM radio won't generate much audio above 5-8 kHz, unless you feed in a bluetooth signal. You'd be better off with a period speaker. First off I'd place a wants ad here on the Forum - you never know, somebody might have an exact replacement. If you can't get the exact size, you could also consider a secondary baffle-board to adapt to a smaller speaker, even an elliptical one which would be easier to find new since they are still available for the car radio market. Jerry

[cathoderay57]

If you made the secondary baffle this would work https://www.ebay.co.uk/itm/167894672279 (although make sure there is enough space to accommodate the magnet depth

[Silicon]

Have you checked the 'spider' near the voice coil?

[Techman]

Are you sure that's a 10" speaker?

I'm not familiar with that radio, but 10" is normally large floor standing and radiogram size. I would have thought that the original speaker was repairable from what the OP has said and it looks like an 8" one to me.

[BrianAllen]

Thank you all, plenty to go on, will do as you recommend.

Yes, definitely a 10 inch speaker re: the service sheet and to be sure I have just measured it. It won't be a problem to remove and check it out again as I left long leads/wires and only used connectors and not soldered as I knew that I would be returning to address the problem

Thanks,

Brian

[Techman]

Originally Posted by BrianAllen

Yes, definitely a 10 inch speaker re: the service sheet and to be sure I have just measured it.

Ah-ha, so it does...and even gives a part number for it. It's deceiving, and certainly looks smaller than it actually is.

These are often to be found in early 50's radiograms that nobody wants. There was one offered free recently in the for sale section. Someone was clearing a house and if nobody wanted it then it was going in a skip. It was there on offer for weeks until it was finally thrown in the skip when there were no takers. I know this particular radiogram had a 10" speaker, as I've worked on that model in the past. I had thought about suggesting that the chap remove useful items such as the speaker and output transformer, also to pull the valves and rather rare pickup head/s, before chucking it, but noted the recent clamp down on posts about items in for sale threads not directly regarding actually buying the item, so decided to keep my gob shut on this occasion. It's worth keeping a close eye on this section when you're restoring a particular set.

[Radio Wrangler]

Wharfedale made 8 inch and 10 inch speakers with whizzer cones (DD = Dual diaphragm) which were quite popular. The dual cone type will give you a bit more treble response, but you might only find 8 Ohm ones. If so, you could change the output transformer for one with a suitable ratio. These were much better than average quality, well made, and quite efficient. Model numbers were something like "Super8RSDD" where the number is the diameter in inches. RS means Roll surround, a roll made of cambric cloth nd so avoids the rubber rot affecting modern drivers.

David

[Ed_Dinning]

Ref David (RW)'s comment on changing the OP trans. The speaker winding is on the outside of the transformer and fairly thick wire, so quite simple/ easy to rewind for a different impedance

Ed

[Aub]

https://www.hotroxuk.com/celestion-ten-30-8ohms-speaker.html

Found this one, but its 8 Ohms. It would work with a lower output.

Cheers

Aub

[BrianAllen]

Lots more very useful and interesting information; thank you gents.

Brian