I am trying to help my friend buy a receiver/amplifier for his home audio setup.

He has 8 ceiling speakers with 4 wires (red,black,green,white) and 4 wall speaker with 2 wires (red,black) throughout the house. The ones with 2 wires produce a crackle when attached to a AA battery and have a DC resistance. The 4 wire ones have a small DC resistance, and do not crackle (although maybe the speaker is out of earshot).

Based on these observations, I think the ceiling speakers are 70V because based on this forum, the DC resistance would be high due to 70V speakers having a transformer.

I think the wall speakers are 2/4/8 ohms because they have a low resistance, but the multimeter he is using is not good so I don't have a precise measurement.

Is this assessment correct?

If so, would this mixing amp work?

  • 1
    You might also try asking this on Electrical Engineering. Oct 7, 2022 at 2:36
  • 1
    Not a good fit for EE. And @jb0, your link doesn't work, so perhaps you could provide more detail than "this" about whatever the heck it is. Few things will happily run both type of speaker, so you generally need one amp for each type (also, 70V speakers are almost always rather low-fi to put it mildly - simply replacing them might be the better approach.)
    – Ecnerwal
    Oct 7, 2022 at 2:41
  • @Ecnerwal sorry about the dead link, should be fixed now. Has both 70V and 4-16 ohm outputs.
    – jb0
    Oct 7, 2022 at 2:49
  • Amazingly, there isn't an "audio" stack here. While adding a whole house audio system is a home improvement, I don't know that identifying existing speakers is quite within our realm. You've found a forum that's directed you somewhat in the right area, I'd suggest registering and asking there, as they're much more likely to have the specialized knowledge to help you than we are here.
    – FreeMan
    Oct 7, 2022 at 14:15
  • That sounds correct. If you remove one of the 70V ones it will have a transformer. It may be another voltage and that would be marked on the transformer.
    – Gil
    Oct 7, 2022 at 15:19

1 Answer 1


The correct way to determine what type of speakers you have is to remove them from the wall or ceiling and look at them. They are not part of the wall/ceiling, they are removable.

Heck, I've installed speakers I didn't strictly need because the speaker, housing and grille were cheaper than an access hole cover, and I needed the access hole...


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