I have one, I just don't want to remove the scanner from where it's mounted to measure. In fact, I know what the impedance of the scanner is. The question is now if a 4 ohm speaker will work well with an 8 ohm output.
Speaker impedence
- Thread starter garys
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My Yaesu FTM-400 specified its output impedance as 4-16 ohms. Power output into an 8 ohm speaker is 3 watts. With a 4 ohm speaker it is 8 watts. Neither will damage the radio. One will be louder.
Stop worrying and get a nice speaker. Maybe consider an amplified speaker with DSP.
Stop worrying and get a nice speaker. Maybe consider an amplified speaker with DSP.
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I want to thank everyone in this thread. I play mandolin in a little country band. We're our own roadies so we set up our own sound equipment. I've tried to explain speaker impedance to the rest of the band but they haven't been able to wrap their brains around it. Some of the examples and information in this thread was passed on to them and (I think) they understand it now. Who'd a thunk it?
Ubbe
Member
My Uniden SDS100 doesn't have any limitations from the earphone jack, it has plenty of power to drive a 2 ohm speaker. So no limiting resistors or it would just be a whisper from a low impedance speaker.
Speakers use a coil to build a magnet field that works agains a permanent magnet to move the membrane that pushes air to produce sound. The magnet fields strenght increase with the current thru the coil. An amplifier outputs a certain voltage at a certain volume setting. A lower ohm speaker draws more current at a specific voltage compared to a higher ohm speaker and then produce more power. An amplifier specifies to be used with a specific speaker impedance where it is still able to produce enough current where the voltage doesn't drop and gives less power, which will be at the lowest frequencies and still maintain a flat frequency response. The human ear can just barely detect a 3dB difference in audio level, half the power from a speaker, so a perfectly flat frequency response are not that important in a scanner.
If an 5 watt amplifier can output max 5 watt to a 8 ohm speaker doesn't mean that it can output 10 watt to 4 ohm speaker. It will still be 5 watt but you will get that already with the volume turned up half ways and turning it up more will only produce distorsion and clipping, that are very evident to most human ears.
My Motorola speaker are labeled as a 2 ohm speaker and the speaker element are stamped with 2 ohm. When I measure its DC resistance it is 2,4 ohm. To be able to measure its impedance at 1000 Hz I would need to output a signal from a tone generator and have a known resistor in series, something like 10 ohm, and measure the signal drop over the speaker, compared to any signal drop from the generator, to be able to calculate its impedance using ohms law. But it is giving a much better audio quality than the internal speaker and max audio level from both speakers are about the same.
/Ubbe
I don't need an amplified speaker. Plus where I have the speaker mounted makes running power wires a pain.
I'm going to order the speaker from Amazon. If I don't like it on my scanner, I can always use it on my dual band ham rig.
Thanks for the info.
I'm going to order the speaker from Amazon. If I don't like it on my scanner, I can always use it on my dual band ham rig.
Thanks for the info.
You could look at the internal speaker if it doesn't say what ohms, you could check it with an ohm meter if you have one.
actually an ohm meter only measures DC resistance while speaker resistance is actually "impedance", i.e. AC resistance at (like stated by someone else earlier) a given frequency.
That is correct but, usually you can get a good idea just from a resistance check.
This is probably more than any of us need to know but I'll post it anyway!
I ordered the Icom speaker and it came this morning. I installed it and I am very happy with the audio. It's clearly a better speaker than the no name one I was previously using. First, the magnet is much heavier, so it's a better product. The audio is much crisper and more clear even on weaker signals.
I fit in the same spot where the other speaker was, I didn't have to do anything but take the old bracket out, put the new on in, and run the wire inside the door weather stripping.
I have a 100mfd cross over capacitor in the old speaker to even out the analog and digital audio. I'm not going to do that with the new one until I've run it a few days to see if I really need it. Initially, I don't think I will.
I fit in the same spot where the other speaker was, I didn't have to do anything but take the old bracket out, put the new on in, and run the wire inside the door weather stripping.
I have a 100mfd cross over capacitor in the old speaker to even out the analog and digital audio. I'm not going to do that with the new one until I've run it a few days to see if I really need it. Initially, I don't think I will.
Ubbe
Member
Analog has a high pass filter of 250Hz to cut out the CTCSS/DCS subtones but isn't used in digital mode which then sounds to have more bass. That's not a bad idea to have a 100uF in series that will give a 8 ohm reactance at 200Hz, if it's a non polarised capacitor that can handle the alterating current. I wish that Uniden would give us the possibility to adjust those filters and levels to our own taste. They are now hidden in service mode and cannot be easily accessed.
/Ubbe
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