My owners manual for my Icom R-75 specifies an external speaker at 8 ohms. Would it be alright to use a 4 ohm speaker instead? (It's a small speaker) 
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4 ohm speaker
- Thread starter riverrat373
- Start date
Shouldn't be a problem at all with the audio output of that radio. If you're worried, you can put two four-ohm speakers in series.
My car stereo amp speaker outs can be run in a 4 ohm or 2 ohm configuration. With 2 ohm,I can double the output going to each channel. The amp runs hotter in a 2 ohm configuration though but within design specifications if I match it with the right speaker. For your application,making sure your speaker out is seeing 8 ohm so it won't overdrive the output transistor with too much current. Plus try to match the speaker rms with your radio's speaker output power. A bigger wattage speaker than your radio's specified output can result in reduced audio volume.
How's that work? My 100 watt Cerwin Vega stereo speakers are really loud with just a Kenwood TS-820S driving them with one watt or less. LOL it's all about the SPL (Sound Pressure Level) figure.
As for the OP yes you can use a 4 ohm speaker in place of an 8 ohm speaker however be aware that at high volume levels you may get more distortion and the audio amp run hotter. In most cases however when using a 4 ohm in place of an 8 ohm you will not have to run the volume control up as high for the same volume.
Yes,spl is a factor. If your speaker has a really good sensitivity rating then you don't have to put as much power into them to get as much volume.
An example would be one speaker with a sensitivity rating of 93db vs. 90db. A greater sensitivity rating means that you won't have to put as much power into them to get a descent volume level. The sensitivity rating a speaker has is a major game player as well as frequency response and power handling and impedance.
Car Speakers Glossary
My brother used to run 8 ohm speakers on a stereo designed for 4 ohm operation. He got a higher volume level as compared to using a 4 ohm speaker but along with that he had a higher distortion level.
P.S. I'm thinking about using a hifi speaker for a external speaker myself but it has to have a good spl rating plus it has to have a power handling specifications that match my transceiver's speaker power output. You can look in your transceiver's owner's manual in the specification section to find the radio's speaker power rating.
Example manual: http://www.ftldist.com/media/manuals/PRO505XL.pdf
This is what I use in my mobile:
Uniden Bearcat BC7 Compact CB Speaker
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A couple things You should Know..
replacing 8 Ohm speaker with a 4 Ohm
It is the Speaker ( not the amp ) that decides what Power to Pull and thus Feed the Speaker..
So using a 4 Ohm in place of an 8 Ohm can cause several issues with an amp Designed for 8 Ohm's
given these radios you are using do Not pump( or designed to pump ) much power...It may or may not be an issue..
However...at the Very Least..
Following will Happen..
You will Shorten Lifespan of the Amp driving the speaker..
You will get Louder and perhaps clearer sound at Low volume settings..
You in turning up Volume settings will start to distort much quicker..
You in turning to higher volume settings will cause the amp to provide more and more power to run the speaker..thus start to over heat and or even cause amp failure ..
Getting cheep and or good 8 Ohm speakers is easy for the radio you have..So why use a 4 Ohm one in its place ?
replacing 8 Ohm speaker with a 4 Ohm
It is the Speaker ( not the amp ) that decides what Power to Pull and thus Feed the Speaker..
So using a 4 Ohm in place of an 8 Ohm can cause several issues with an amp Designed for 8 Ohm's
given these radios you are using do Not pump( or designed to pump ) much power...It may or may not be an issue..
However...at the Very Least..
Following will Happen..
You will Shorten Lifespan of the Amp driving the speaker..
You will get Louder and perhaps clearer sound at Low volume settings..
You in turning up Volume settings will start to distort much quicker..
You in turning to higher volume settings will cause the amp to provide more and more power to run the speaker..thus start to over heat and or even cause amp failure ..
Getting cheep and or good 8 Ohm speakers is easy for the radio you have..So why use a 4 Ohm one in its place ?
Spent many times selecting and testing speakers to suit a specific environment where they were used as studio monitors.
Hmmm....odd. It should have been the other way around. Any amp I have seen the specs for always produced more power output into a lower impedance speaker.
What does the audio power output rating have to do with speaker power handling other than to make sure the speaker will handle the couple watts from the radio? They certainly do not have to match ratings.
Been looking at tech specs of radios and audio gear for going on 40 years now. You are preaching to the choir now. LOL
Interesting how in that link it states the audio power out is 3 watts into 8 ohms and then states that the internal 8 ohm speaker is rated at 2 watts. LOL
What you say is all true however most radios have a series resistor in the output of the audio amp that helps it handle lower a impedance anyway. Most of the time the manufacturer simply specs an 8 ohm speaker as that is what is normally available when in fact the amp will operate into some very low impedances. I have used some audio amps that were designed to operate into a 0.1 ohm impedance. Yes that is one tenth of an ohm. You could operate them into anything higher with slightly reduced output and they were pretty much short circuit proof.
Yes that's exactly what I meant. 3 watts of audio available and a 2 watt speaker to handle it. Most external speakers are rated for 5-10 watts anyway.
I always pay attention to the distortion numbers. The 505's distortion figure is less than 10% at .5 watts @1000 hz. I wonder what the distortion figures are at other sound frequencies They might as well say 9.99%. Clean sound reproduction is usually not at max volume levels.
I ordered a Astatic 302-V4 5 watt noise cancelling external speaker for my base station setup. I'm going to try that out.don't know exactly just yet how that works on a speaker.
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10% THD is about the limit anyone wants to listen too hence that is pretty much a standard spec. They also use 1000 Hz as that is a standard reference frequency where most level and distortion tests are done. It is also a frequency where the human ear tends to be most sensitive. Also clean sound reproduction is almost NEVER at max volume levels. As an amp runs out of headroom distortion products increase however some amplifiers are designed such that they will produce maximum rated output while maintaining enough headroom such that the distortion at full output is no more than at 1/100th of rated output. Most radios and low end audio gear use 10% THD as a benchmark while higher end gear uses somewhat less. My Yamaha MX-830 stereo amp is speced at a true 170 watts per channel into 8 ohms at 0.003% THD. with 2 dB additional headroom. That is not much more than what it produces at only 1 watt output.
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...runna pile-up on 6m SSB