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Scanner / Speaker Compatibility / Ohm Value

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Feb 13, 2002
Birmingham, AL
OK........... I'm not an electrician, but I do love my scanner.

Please answer in layman's terms....plain english.

I run an external speaker on my Uniden 785 in my car.

When I look at Motorola or GE speakers on eBay, I see a range of Ohm ratings along with the wattage rating of the speaker.

Ohms as I recall is a measurement of resistance.......hmmm??? I have seen formulas for Ohms law. (If I break Ohms law, do I get a ticket??? LOL) Sorry.... Lest I digress.........

How important is the Ohm rating of a speaker when applying it to a scanner or other receiver????? Does the sanner audio "system" have a specific Ohm rating?

Thank you in advance for your help.


Premium Subscriber
Apr 7, 2004
Ohm Ranges Frequently Nominal

From my readings most speakers/receivers ohm ratings are nominal/in name only at least to a point. Generally, interchanging 4 ohm speakers with amps/radios made for
8 or six is ok. Although if it were 2 ohm I'd be a little less confident at least in home stereo applications. In any event I'm told that the ohm rating of a speaker is nominal
because the actual value depends quite widely depending on the audio frequency in question.

Bottom line, hooking just about any speaker within reason, other than something like a
dual voice coil subwoofer, should be just fine for your scanner.



Pastor and Chaplain Responder
Oct 22, 2005
Hey, Julian - look at this link for BC 785 spec's and note that the internal speaker is 8 ohm. Since the miniplug disconnects the internal speaker when an external is used, that circiut would be 'happiest' with an 8 ohm external load. That will give you roughly the same characteristics as the original, but will allow you to position it so it can be heard better, in a vehicle.

Use an 8 ohm, 3 watt (or higher) rating on the external and happy listening. The second link shows the one that we are using in several of our vehicles. They have noise cancelling and they are bulletproof...




Dec 21, 2005
Not allowed...infraction.
Look at your other post for my answer to your question.

Also, there is a BIG difference between DC ohms and AC impedance in ohms. Think, why is some coax cable 50 ohms and other 72 ohms??? You can't measure any resistance (ohms) on the coax between the conductors with your ohmmeter can you?? An 8 ohm speaker could very well have an 8 ohm voice coil, but it could just as well have a 25 ohm DC resistance voice coil!!!!. One is an impedance otherwise known as Z, in ohms, and the other is a DC resistance in ohms ,otherwise known by the Greek letter Omega! In short, if the radio's audio amp is designed for a 8 ohm IMPEDANCE speaker, it's best your external speaker be just that. If you use a lower impedence speaker, then the audio circuit, particularly the active componets, will overheat and possibly fail! If you use a higher impedance speaker, the radio won't care but the audio will continue to become lower the higher you go in impedance.
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