Speaker impedence

[garys]

I'm looking at different external speakers for my SDS200. Some are 8 ohm, some are 4 ohm. I looked in the SDS200 manual, but can't find what impedence is required. Does anyone know off hand?

 

[n1chu]

You could always go with a Uniden external speaker, either amplified or passive. A post in Radio Reference states there could be a problem below 4 ohms. I use the Uniden amplified external speaker and it does just fine in my noisy pickup.

 

[RandyKuff]

The Uniden speaker I use on my SDS200 says it's 8 ohm's...

 

[n1chu]

8 ohms will work as RandyKuff says. I have a bunch of Motorola speakers that were going to be discarded when they upgraded the local police departments radios. They all work great. I was told the speakers were either 4 or 8 ohms and remember putting a 4 ohm resister both in parallel and then in series to see if I could tell a difference. I don’t recall hearing a difference but it’s been better than ten years and my memory isn’t as good as it used to be.

 

[RandyKuff]

If you drive a 4 ohm speaker with an amplifier rated for an 8 ohm speaker, you are requiring the amplifier to double the power output in order to drive the speaker. At low volume, this might be OK

 

[garys]

Thanks. I was looking at an Icom speaker, but it's 4 ohms.

The Uniden speaker I use on my SDS200 says it's 8 ohm's...

 

[Ubbe]

If you drive a 4 ohm speaker with an amplifier rated for an 8 ohm speaker, you are requiring the amplifier to double the power output in order to drive the speaker. At low volume, this might be OK

It's the ampere, the current, not the voltage that increase with lower impedance speakers. When a low ohm speaker outputs the same audio power the amplifier also outputs the same power, no difference there, but the amplifier needs to be able to handle a higher ampere output at a lower voltage but it will still be the same power output from the amplifier but the volume setting probably has to be set lower to give the same audio level from a low ohm speaker.

Modern amplifier IC's that are used in scanners are both current limiting and temperature sensing that even handles a short circuit. The important thing to concider are if it sounds distorted then it's probably not healthy for the amplifier and needs attention. I have been using a 2 ohm speaker with a SDS100 for a long time and there's no audio distorsion even at higher volume levels.

/Ubbe

 

[RandyKuff]

If a speaker has low impedance, that means it can tolerate more power (a stronger current). A 4-ohm speaker extracts twice as much power than an 8-ohm speaker from an amplifier. The 8-ohm speaker requires less power to generate the same level of volume as a 4-ohm speaker. That is the big difference between the two speakers…

Voltage stays the same. Amperage goes up. More power draw from the amplifier for a 4 ohm speaker…

 

[Ubbe]

More power draw from the amplifier for a 4 ohm speaker…

Yes, if the volume level to the final amp are the same, but then the loudspeaker will also produce twice the output power. You imply that low ohm speakers have half the effecience of a higher ohm speaker. All the power that the amplifier produce are also produced out as audio volume from the speaker.

The 8-ohm speaker requires less power to generate the same level of volume as a 4-ohm speaker.

I think you might confuce ampere/current with power.

/Ubbe

 

[RandyKuff]

You need to do some research... I'm not wrong... And not confusing anything..
You believe what you want... I'm done...
I've been a EE for over forty years...

 

[iMONITOR]

8 ohms will work as RandyKuff says. I have a bunch of Motorola speakers that were going to be discarded when they upgraded the local police departments radios. They all work great. I was told the speakers were either 4 or 8 ohms and remember putting a 4 ohm resister both in parallel and then in series to see if I could tell a difference. I don’t recall hearing a difference but it’s been better than ten years and my memory isn’t as good as it used to be.

I used to buy older Motorola amplified speakers in the steel enclosures. I would bypass the amplifier and wire the speakers directly and they worked very well. The speaker itself in those units were all 32 ohms and had plenty of volume for indoor use.

 

[Brentorious]

Thanks. I was looking at an Icom speaker, but it's 4 ohms.

I’m probably looking at the same Icom speaker you’re referencing, and I’ve been digging for the SDS200 audio specs and can’t find them. Would be nice if a Uniden rep could look this up for us.

 

[WB9YBM]

I'm looking at different external speakers for my SDS200. Some are 8 ohm, some are 4 ohm. I looked in the SDS200 manual, but can't find what impedence is required. Does anyone know off hand?

The majority (if not all) modern equipment's 8-ohms; if memory serves, speakers used with tube equipment's 32-ohms; I've seen 4-ohms but not sure where that's used....

 

[garys]

Motorola used some 4 ohm speakers in the 1990s or so. I'm looking at the Icom SP-35, and the only information I can find seems to indicated it's also 4 ohms. Hence my question.

The majority (if not all) modern equipment's 8-ohms; if memory serves, speakers used with tube equipment's 32-ohms; I've seen 4-ohms but not sure where that's used....

 

[pro92b]

I wouldn't hold my breath waiting for Uniden to weigh in on speaker impedance to match the SDS200.

In the European Union where corporations don't run roughshod over consumers quite like they do in the USA there is apparently a requirement to publish specifications for equipment. So if you locate the Uniden SDS200E owners manual you will find several pages of specifications. There is no mention of anything other than 8 Ohms for a speaker load. The output audio amplifier is bridged and that configuration typically doesn't drive low impedance speakers well. So it looks like 8 Ohms is the right load for the radio.

Another angle to investigate is to look inside the SDS200 and see what chip is used for audio output. I don't own a SDS200 and likely never will but do have a BCD536HP which also has a bridged output. The audio chip inside the 536 is a ROHM BD5413EFV Class D Audio Amplifier. It has a load resistance rating of 6 to 16 Ohms so a 4 Ohm speaker is below the manufacturer's limit. Uniden does have specs in the 536 owners manual and an 8 Ohm speaker is called out.

 

[AI7PM]

That one, Icom SP-35, is 4 ohms, which I find interesting. Icom recommends it for their ID-5100, which in the manual specifies 8 ohms. It is a good sounding speaker, but why the discontinuity in recommended vs specified?

 

[WB9YBM]

Motorola used some 4 ohm speakers in the 1990s or so. I'm looking at the Icom SP-35, and the only information I can find seems to indicated it's also 4 ohms. Hence my question.

Well, I suppose you could try both a 4-ohm speaker and an 8-ohm speaker and the one that works better indicates the right speaker. (At least, that's the simple approach although I suppose someone reading this will come up with something more complicated that will work better...)

 

[ko6jw_2]

Speaker impedances are variable with frequency. Four or eight ohms are nominal values. The same is true of output impedances from radios. A lower impedance generally results in higher output from a solid state amplifier. Otherwise stop worrying about it. There is no magic to it.

Uniden handheld scanners have headphone jacks with an attenuated output to avoid overdriving headphones. They need amplified speakers to produce an acceptable volume.

This subject comes up over and over in these threads. It is really a non-issue.

Personally I use only 6.17499375 ohm speakers.

 

[garys]

So, is what you're saying that it doesn't really matter what the impedance is? A 4 ohm speaker won't harm the radio, it will just be louder at a particular volume setting than an 8 ohm speaker?

Speaker impedances are variable with frequency. Four or eight ohms are nominal values. The same is true of output impedances from radios. A lower impedance generally results in higher output from a solid state amplifier. Otherwise stop worrying about it. There is no magic to it.

Uniden handheld scanners have headphone jacks with an attenuated output to avoid overdriving headphones. They need amplified speakers to produce an acceptable volume.

This subject comes up over and over in these threads. It is really a non-issue.

Personally I use only 6.17499375 ohm speakers.

 

[crippledchicken]

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.