Radio-speaker compatibility

[Mark Gordon]

I received a Retrosound Zuma radio for Christmas and have a pair of modern speakers (I think that they're Bose) that look like they will fit in the console. The specs for the radio say that it is compatible with 4-8 Ohm speakers. I don't see anything on the speakers that identifies their resistance, but when I put an ohmmeter across the + and - contacts, it registers 3 ohms. Two questions: is that the correct way to measure resistance in the speakers and if so, will that lower resistance harm the radio?

[norman m. macleod]

Hi mark,
The DC resistance taken with an ohmmeter has little relevance. The actual working resistance of a speaker (or more properly impedance...) varies as the frequency of the applied signal from your radio output....for instance, the impedance may well be 4 ohms at 50 Hz, but could be 15 ohms or more at higher frequencies. So the rating is a nominal average, if you will, the output (on music) is a complex mix of frequencies. I doubt if you will have any problems with the components you have nominated.....Bear in mind, however, that if you connect them (2 speakers) in series, you will have a nominal 8 ohms, but if you connect them in parallel, the impedance "seen" by the radio output terminals will drop to a nominal 2 ohms, which may give you a problem.......
Kind regards,
Norman.

[norman m. macleod]

Hi again Mark,
Just thinking about what I said, please note that my comments on speaker connections would only apply to a mono output set-up radio. With stereo FM, (or any other stereo input), there will be 2 separate speaker outputs on the radio, which should be connected separately and conventionally, and my previous comments on impedance still apply. I've just had a look at that Retrosound Zuma on the internet, looks good, just what I've been looking for, for my Series 1 2+2...!
Kind regards,
Norman.

[Mark Gordon]

Thanks, Norman. From what you have probably learned from looking up the Zuma radio online, it is a stereo system with four speaker outputs (two front and two rear; I will only be using the front outputs). It looks like I will be OK using the speakers that I have on hand. If we get some reasonably warm weather this weekend (predicted high today 35 deg. F.), I will try to get it installed and try it out. I will report back once I know more.

[Heuer]

Agree with Norman - you will be able to use those speakers without problem.

[Mark Gordon]

"Agree with Norman - you will be able to use those speakers without problem." In theory, I'm sure you're right, David and Norman. Unfortunately, once I got the console out and took the original speakers out, I found that the Bose speakers wouldn't fit into the sides of the console without making a pair of adapter rings to secure the slightly smaller (diameter) Bose speakers. I ended up just using the original speakers which were after market jobs that had been installed by one of the PO's. After hooking everything up, the system works just fine, but I doubt that I'll be listening to the radio very much once the weather warms up and the hood goes back down for some cruising. But it certainly looks a lot better than the modern Kenwood radio that I removed. As always, thanks for the advice!