Air Chief Push Button Radio

[Brad_Povey]

I am looking to get a speaker for an Airchief Push button Radio.  Can anyone tell me what sort of resistance is necessary for the speaker?  None of the audio outlets I've spoken to have any idea and nor do I.    

[craiga]

Brad,

Speakers for these early radios usually have an impedence of 24 Ohms. You can't purchase this exact type any more, however some one on the forum may be able to assist. One of the radio restoration companies may also be able to help. I've seen an ad for one in Restored Cars. Any one have contact details?

You could also use a new speaker that fits the housing and modify the input impedence to suit (so your radio thinks its seeing a 24 Ohm speaker) .

Cheers,

Craig.

[craiga]

Brad,

I have just done some reading and you will need to put a 24 Ohm resistor in series with one of the speaker wires. This will increase the impedence of a modern 4 Ohm speaker to the required 24 Ohms. You will need to use a 5 Watt version, which you can buy from Dick Smith or another outlet that stocks components. Dick Smith stock a 12 Ohm 5 Watt resistor, buy two of these and connect them in series and you'll have the required 24 Ohms. Bargain at 48 cents each.

http://www.dse.com.au/cgi-bin/dse.storefront/4039904609303e7a273fc0a87f9c06be/Product/View/R1628

Here is the formula:

X = impedance of the speaker
R = resistance of the resistor

The impedance of the total unit will be given by the following formula:
square root of (X squared + R squared) =
square root of (4 squared + 24 squared) = 24.33 ohms.

Close enough to 24 ohms.

You could use the 4 Ohm speaker without modification but your original radio's output amplifier will eventually fail.

I have attached a picture of a rear view of the original type 24 Ohm speaker.

Cheers,

Craig.

[Shayne]

This excellent website may or may not confuse you more!
http://203.44.53.131/Airchief/Airchief.htm

regards, Shayne.

[zulu]

G'day all, I thought that these old radios ran a 15 ohm speaker, which are very hard to find.
Gary

[leon]

 :)Hi Gary.
The speaker in the FE special I got from the bush it has a speaker in it and it is a rolla brand with it's original lead and plug. I'm just suggesting that this may have been the original.
Regards Leon .

[zulu]

G'day Leon, Yes, I have a couple of Rola speakers down in the shed that came with Air Chief radios attached, & from memory they are 15ohm.
Regards, Gary

[craiga]

Thanks Gary, I'll stand corrected. Maybe there were different impedances for different radios? The 24 Ohm unit I have is fitted to an AWA valve push button unit.

If the speaker should have an impedence of 15 Ohms, and you want to use the modern 4 Ohm speaker, just fit a 14 Ohm resistor in series instead of the 24 ohm previously suggested.

Cheers,

Craig.

[Rodney Zivkovic]

From my understanding the Speaker were of the 15 Ohm type (but am not sure).

I am going to get a custom Speaker built (by Total Recoil in Melbourne). So I hope it is 15 Ohm. He quoted about $160.00 for it and should should be designed much more efficient than a new one (or even the original one).

Does anyone have the exact dimensions including mounting holes for the original Speaker (so I can get it copied).

I may get a couple extras made up???

[Brad_Povey]

Thanks everyone 15 - 16 seems to be the GO.