XTL2500 alternative speaker?

[torquative]

Hey all

Just wondering if there is any chance of using an alternative speaker on an XTL2500 or must it be the standard Motorola HSN40XXX speaker?

The dilemma I am facing is that I am doing an install into a car with very limited space. The Motorola speaker is too large to fit anywhere suitable without needing to sit well under the dash somewhere.
The local auto parts store sell a generic external UHF radio 8 Ohm speaker which is much smaller in size and would be alot easier to mount.

I'll be honest I'm not too confident with the speaker hence why I'm asking, as I don't want to stuff the audio board on the radio. If need be I'll find somewhere for the original Motorola speaker to mount, but I thought I would ask in the off chance someone may have used an alternative speaker in the past or can guide me on what I need to look for so as to not risk the life of the componentary of the radio.

Cheers

 

[triptolemus]

Sure.

Just check the Basic Service Manual (which can be found on this site) for the parameters on the speaker the radio expects to see. At 8 ohms, you push less power which means less volume. At 3.2 ohms, you push more power which means more volume. The circuit seems pretty forgiving, but I would not exceed either the high or low resistance parameter.

It's also VERY IMPORTANT that the speaker attached to the radio is NOT attached to the vehicle's ground. Very important. If it's me, I would verify negative continuity from both speaker terminals to the speaker frame using the appropriate tester.

 

[steve_jacobson]

What about the RSN4003A? It's a lot smaller than the HSN4031B and both are still 7.5w.

 

[KJ6PNN]

It's also VERY IMPORTANT that the speaker attached to the radio is NOT attached to the vehicle's ground. Very important. If it's me, I would verify negative continuity from both speaker terminals to the speaker frame using the appropriate tester.

What is the reasoning behind this? (Just curious). Shouldn't it pull to ground, or am I missing something?

 

[JMR061]

Grounding a motorola radio audio circuit will damage it and blow the audio amp or something in the audio circuitry...no more audio.

 

[KJ6PNN]

Grounding a motorola radio audio circuit will damage it and blow the audio amp or something in the audio circuitry...no more audio.

Interesting. I was told to not do it, but never why.

 

[Alpha]

The technical reason is that both speaker outputs float at +12 VDC, and the audio AC is developed across them in common-mode. Since there is no reference to external ground, it doesn't know it's floating up around +12V, all it sees is the audio between the speaker terminals.

This is fairly common in most automotive audio; most internal car radios have the same issue, except for Fords, notably. They used unbalaced speaker audio referenced to vehicle ground instead of the more common balanced outputs.

 

[BobbyBoucher]

OUCH!
Looked it up on MOL, $48 list price.
However, it does appear to be a great option for a smaller sized speaker.
Any idea how the audio compares to the regular sized mobile speakers?

What about the RSN4003A? It's a lot smaller than the HSN4031B and both are still 7.5w.

 

[com501]

View attachment 7972

XTL's should NOT have either outputs grounded!!