Motorola HSN4031B Speaker Question

[KR7CQ]

For someone familiar with this speaker, what is the ohm rating? I've poked around but can't seem to find out. I am thinking about buying a few for scanners which specify 8 ohm speakers, so I'm trying to figure this out. If they are 4 ohm, I've been told it's no big deal by some to plug them a 8 ohm scanner jack, but others have said the opposite. I know some use the 4 ohm speakers on scanners without issue but the scanners I'm looking to hook up are somewhat collectible, so I want to be sure.

 

[pro92b]

The Batlab forum lists the HSN4031B as 8 Ohms.
Any audio difference between HSN4030A - HSN4031B speakers ? - Batboard

That said, I have read of instances where the speaker actually inside some Motorola speaker cases can vary in impedance. If you have the HSN4031B in your possession, open it up and read the info printed on the speaker magnet.

The use of 4 Ohm speakers with a scanner should generally not be a problem. What particular scanner models will be connected to the speaker?

 

[KR7CQ]

Thanks. Four scanners I have in mind, Uniden BC780XLT, Uniden BC9000XLT, Realistic PRO-2006, Whistler WS1065.

They all have external speaker jacks on the back that I plan to plug into with 1/8" mono plugs that I solder on.

***Edit, the BC9000XLT only has an external speaker jack on the front.

 

[pro92b]

The BC780XLT, BC9000XLT and PRO-2006 all use a TDA1905 audio amplifier chip. The TDA1905 is rated to operate with a 4 Ohm load.

The WS1065 is supposed to be equivalent to a PRO-197. The PRO-197 also uses a TDA1905 audio chip.

 

[KR7CQ]

The BC780XLT, BC9000XLT and PRO-2006 all use a TDA1905 audio amplifier chip. The TDA1905 is rated to operate with a 4 Ohm load.

The WS1065 is supposed to be equivalent to a PRO-197. The PRO-197 also uses a TDA1905 audio chip.

Thanks, so it sounds like using these 8 ohm speakers will mean I have to turn the volume way up to have a decent sound level, correct?

Any risk of using the 8 ohm speakers?

 

[cmdrwill]

The problem is NOT the audio amplifier chip. But the output coupling capacitor in scanners, ect, may be a lower value and does not work well with 4 ohm speakers.

 

[pro92b]

8 Ohm speakers are probably what is in the scanners so there should be no problem with an external 8 Ohm speaker.

Regarding the use of 4 Ohm speakers, first establish that the amplifier will work without strain into 4 Ohms. The coupling capacitors are 100uF for three of the scanners and 220uF for the PRO-197. 100uF with a 4 Ohm load has a -3dB frequency of 400Hz which is adequate for reproducing voice frequencies. There is no issue with using 4 Ohm speakers with these scanners. It's a moot point since the external speaker in question is expected to be 8 Ohms.

 

[KR7CQ]

The problem is NOT the audio amplifier chip. But the output coupling capacitor in scanners, ect, may be a lower value and does not work well with 4 ohm speakers.

OK now that makes sense with what I'm seeing. I must say it's amazing that none of the four scanners I mentioned specifies an impedance for the ext. speaker jack in the manuals.

The BC9000XLT manual suggest the ESP25 speaker for external use and it's 8 ohms. The PRO-2006 specifies an RS part number 21-549 external speaker that is 8 ohms. Looking in manuals for the WS1065, the PRO-197, the PSR-600, and the BC780XLT, no speakers are suggested, and there is no specification for recommended speaker ohms (seems like an oversight to me). All un-powered speakers advertised as "external scanner speakers" are 8 ohm, as far as I can tell.

 

[Project25_MASTR]

OK now that makes sense with what I'm seeing. I must say it's amazing that none of the four scanners I mentioned specifies an impedance for the ext. speaker jack in the manuals.

The BC9000XLT manual suggest the ESP25 speaker for external use and it's 8 ohms. The PRO-2006 specifies an RS part number 21-549 external speaker that is 8 ohms. Looking in manuals for the WS1065, the PRO-197, the PSR-600, and the BC780XLT, no speakers are suggested, and there is no specification for recommended speaker ohms (seems like an oversight to me). All un-powered speakers advertised as "external scanner speakers" are 8 ohm, as far as I can tell.

Whistler notes it for the TRX-2 as 8 Ohms Resistor Load at speaker terminals, BTL: 500 mW.

The Batlab forum lists the HSN4031B as 8 Ohms.
Any audio difference between HSN4030A - HSN4031B speakers ? - Batboard

That said, I have read of instances where the speaker actually inside some Motorola speaker cases can vary in impedance. If you have the HSN4031B in your possession, open it up and read the info printed on the speaker magnet.

The use of 4 Ohm speakers with a scanner should generally not be a problem. What particular scanner models will be connected to the speaker?

There are actually two speakers in the same housing offered by Motorola. The standard 7W speaker which uses a 8 Ohm speaker and the 15W speaker...which uses a 3.2 Ohm speaker.

 

[KR7CQ]

Whistler notes it for the TRX-2 as 8 Ohms Resistor Load at speaker terminals, BTL: 500 mW.

Wouldn't you know it, that's the one digital scanner I have not owned yet.

There are actually two speakers in the same housing offered by Motorola. The standard 7W speaker which uses a 8 Ohm speaker and the 15W speaker...which uses a 3.2 Ohm speaker.

Fortunately I just purchased four of the 7 watt 8 ohm models.

 

[KR7CQ]

Well I finally got the speakers, and three were HSN4031B and one was HSN4031A. Opening them up, both speakers are 8 ohm, and 20 watt. I cannot see any difference between the two models. Any ideas on what might be different? I looked around, including at Batlabs, but couldn't figure it out.

 

[Anderegg]

I just tested my TRX-2 on both a 4 and 8 ohm Motorola speaker...both sounded fine at MAX volume, no audible indication of strain, and the 4 ohm speaker seemed around 20% louder than the 8 ohm. P25 was about HALF the volume of analog as you max out the volume on the scanner.

Paul

 

[Project25_MASTR]

Well I finally got the speakers, and three were HSN4031B and one was HSN4031A. Opening them up, both speakers are 8 ohm, and 20 watt. I cannot see any difference between the two models. Any ideas on what might be different? I looked around, including at Batlabs, but couldn't figure it out.

Different revisions. That’s all.


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[KR7CQ]

Different revisions. That’s all.


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Thanks. They are slowly getting mounted one by one...great sound...much better than anything else I've tried.

 

[Anderegg]

If buying used Moto speakers, always a good idea to take them apart and clean the shaving s off the back magnet, and wipe the dust and debris off of the cardboard cone.

Paul

 

[KR7CQ]

If buying used Moto speakers, always a good idea to take them apart and clean the shaving s off the back magnet, and wipe the dust and debris off of the cardboard cone.

Paul

Solid advice. I've been lucky enough to find new / old stock speakers. They are still out there.

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[N4KVE]

If buying used Moto speakers, always a good idea to take them apart and clean the shaving s off the back magnet, and wipe the dust and debris off of the cardboard cone.

Paul

I always do this to check the impedance of the speaker, & mark it on the outside. I use the 3 ohm speakers in my car where I need more volume, & 8 ohm speakers in the house.

 

[KR7CQ]

I always do this to check the impedance of the speaker, & mark it on the outside. I use the 3 ohm speakers in my car where I need more volume, & 8 ohm speakers in the house.

I opened all of mine up to verify the speaker wattage and ohms, and to make sure they were clean. Mine are all 8 ohm and marked 20 watt, but the volume and quality of sound produced dwarfs my other external speakers.

The vocal range is so rich and strong that there's just no comparison. The larger speakers also naturally attenuate hiss and static simply because cones that large just don't favor that high of a frequency.

It's funny too because I know these speakers have probably been sitting on shelves for 20+ years.

Now trimming and connecting those big wires in little 1/8" mono plug assemblies is a challenge and tedious, but it can be done.

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