Conversion of a GEC radio 1947

[tomdoughty]

Hello all
Loudspeaker advice.
I'm converting a GEC radio into bluetooth speaker using the cabinet.
Will be stereo. max 50w/channel @ 4ohms
There are two panels where each speaker or combination (woofer/tweeter) will fit. Size of these panels are 9" high x 10" deep
I want the best sound possible; not interested in bass heavy bull full range.
There was an 8" speaker in there as shown on photos. Cabinet is all wood and I will be making it more rigid.
Any thoughts or recommendations about single speakers or pairs with crossovers and suggestions for make. ? thanks Tom

 

[Galu]

Do you have an upper price limit in mind, Tom?

What's your country of location as that helps in regard to availability of components?

 

[tomdoughty]

Hi Galu; I'm in the UK and thinking £150 max. thanks

 

[Galu]

Thanks Tom. Just to narrow down the field regarding speaker choice, do you envisage the radio cabinet being open-back, completely sealed or reflex ported?

What volume do you estimate will be available to the speakers inside the cabinet?

I think good quality 8" full range speakers would present the least hassle regarding fitting into your radio cabinet, but their parameters have to suit your intended method of loading as questioned above.

 

[tomdoughty]

I can seal the cabinet, or use a port.
Volume inside the cabinet 1200cms

 

[Galu]

I'll give your thread a nudge, Tom.

I don't have a firm suggestion as yet, other than to say you'll likely need fairly small drivers in order to match the limited volume available.

1200 cubic centimetres is 1.2 litres which means 0.6 litres is available to each driver.

A frontal photo of the radio cabinet would be nice and would give a better impression of its size.

 

[tomdoughty]

GEC 1947

here you go...

 

[turk 182]

any chance we could see from the inside with speaker removed?
i bet that the curved louvers create a cavity space that may be resonant , might not want to use a two way topology just a good full range and equalize it, heck i'd try a pair or even a quad of TC9's

 

[Galu]

I think turk is referring to the TC9FD18-08 from Peerless by Tymphany, which are little 3.5" drivers: Blocked

 

[tomdoughty]

1947 GEC

image attached. the curved outsides are flat insides. This is getting interesting. Still researching, but I've looked at these and would build suitable crossovers. Buying a SB Acoustics SB16PFC25-4-COAX woofer? - SoundImports
Tom

 

[Galu]

Have you considered the T/S parameters of that 6" COAX woofer, Tom?

It needs a sealed box of minimum volume 4.25 litres to be 3dB down at 90Hz.

For reference, the crossover circuit is available here: https://www.madisoundspeakerstore.com/pdf/SBAcoustic_PFC_Coaxial_Crossover_Designs.pdf

 

[tomdoughty]

1947 GEC

I've considered it, but not in enough detail?

 

[Galu]

You say you don't need heavy bass, so you may be able to bend the volume rules and accept less bass extension.

I would question buying expensive hi-fi drivers though, as more basic full range units may be more appropriate in the circumstances.

I'm not heavily into loudspeaker design, so I hope you get more driver suggestions soon!

 

[turk 182]

well those photo's aren't what i was hoping to see...i take it that the side with the loudspeaker has a cloth between the baffle and grill and the other side is still a mystery as to whether or not removing the panel would access the louver space...the coax is a tad overkill...this is going to be a bluetooth speaker,no? what amp is going to drive it?


is that a harp in the background?

 

[egellings]

Keep little ol' radios original. Don't desecrate them with new technology. One of my goals in life is to make the world safe for little ol' radios.

 

[tomdoughty]

1947 GEC

sorry dear chap. It's repair was beyond my skills. I have the internals, you're welcome to them?

 

[tomdoughty]

1947 GEC

well those photo's aren't what i was hoping to see...i take it that the side with the loudspeaker has a cloth between the baffle and grill and the other side is still a mystery as to whether or not removing the panel would access the louver space...the coax is a tad overkill...this is going to be a bluetooth speaker,no? what amp is going to drive it?


is that a harp in the background?

Amp is Dayton Audio KAB250V3; yes, a harp (my wife's)...
; feel free to suggest. thanks Tom

 

[Kay Pirinha]

i bet that the curved louvers create a cavity space that may be resonant ,

image attached. the curved outsides are flat insides. This is getting interesting. Still researching, but I've looked at these and would build suitable crossovers. Buying a SB Acoustics SB16PFC25-4-COAX woofer? - SoundImports

I bet turk might have been right, as most probably the space between the curved louvres and the flat inner mounting panels aren't filled with anything. Anyway, as it is going to become just another BT unit...
Best regards!

 

[Galu]

This little BMR driver is designed specifically for compact audio applications such as table radios, wireless speakers and Hi-Fi systems.

It has a diameter of 108mm, a high Qts of 0.95 and is available in 8 or 4 ohm.

TEBM65C20F-4 | Tectonic Round Speaker Driver, 30W nom, >60W max, 4Ω | RS Components

https://docs.rs-online.com/d86c/0900766b816b9923.pdf

 

[tomdoughty]

1947 GEC

thanks Galu.. they look suitable and inexpensive too.