[Elecraft] 4-ohm to 8-ohm question

[Don Wilhelm]

Ed,

There is no need to match speaker impedances.  That may have been the 
case when audio output stages had output transformers, but it is no 
longer desired or needed.

The audio output stage is a low impedance source - which means that the 
available output is determined by the load.  You can get more power into 
a 4 ohm load than you can into an 8 ohm load.
The power is determined by the load.

A parallel example - consider the AC receptacle in your wall - it is a 
veery low impedance source.
If you plug in a 40 watt light bulb, enough current will be drawn to 
light that lamp to its full brilliance - drawing about 40 watts of power.
Now plug in a 25 watt bulb.  It will draw less current, but will still 
light to its full briliance -drawing only 25 watts.  The point here is 
that with a low impedance source, the output power is mainly determined 
by the impedance of the load, and no amount of Impedance matching is 
going to make a big difference.

73,
Don W3FPR



On 5/2/2016 4:15 PM, Eddy Avila wrote:
> My K2 audio output is 4-ohms which I drive into an 8-ohm ICOM speaker with filters. Yes, it works OK, but I would like to match them better.
> In the "olden" days I would simply use a 4-ohm to 8-ohm audio transformer, but I can't find them anymore! Really, I've looked at all the suspect places, including eBay and Amazon.
> Any suggestions, I just want and easy, simple way to matching the two impedance's without losing power which would happen if I used a resister across the ICOM speaker. I know I can just drive a small audio amp between them, but that means more wires to power up the amp......
> Thanks to all
> 73
> ed 		 	   		
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