• 10-23-2007, 08:28 PM
    Fleet1950
    Low resistance with Boston CR6 need help
    I have a set of Boston CR6s. I was just messing around and tested the resistance of the speakers. They both test out at 3.6-3.8 Ohms. I know that this is not the most accurate method, but I did test all of the other 8 ohm rated speakers and they all test out at about 5.6-5.8 Ohms

    I am really worried about using such a low impedance speaker with a 8 ohm rated reciever. Am I totally missing something with this? Can a speaker degrade and lose resistance? Please let me know what all of this means.

    Thanks so much for any advice.

    Ok I just went and tested my Boston A40s and they are the same. What am I missing? Thanks!
  • 10-25-2007, 04:34 AM
    SAEA501
    By tested, I am assuming you put a volt meter across the terminals....correct?

    If so, you have measured DC resistance of the assembly. Speaker manufacturers state a nominal or average resistance as this resistance varies with frequency. A stated 8 ohm speaker, depending on it's design, can vary between 2 and 10 ohms, which is determined by the frequency it is reproducing. If Boston presents the speaker as 8 ohms then I would go ahead and use them with your receiver. If they are presented as a 4 ohm system then you can try them with your system but I would keep a close watch on the temperature of your receiver, especially when driving it at a little higher volume. Less resistance allows the receiver's output stage to pass more current and in turn generate more heat.

    A lower impedance load may also present a stability problem to your receiver. As impedance drops current flow increases. Most receivers look at this as approaching a dead short and their protection circuitry will attempt to limit current flow, which will degrade audio quality. Worst case, it is possible you may damage the amplifier. If you are not sure, call Boston and ask what the original specs were for these speakers.
  • 10-25-2007, 06:30 PM
    Fleet1950
    I had looked at a few pages discussing the effects of frequency on the impedance. I knew that testing DC resistance was not the most scientific way to do this, but it just had me worried that all of my other 8 ohm speakers were about 6 ohms. I had called BA yesterday but the guy I talked to had no answer. I called back today and spoke to the head of the tech department and he explained that this is perfectly normal DC resistance for these speakers that when AC impedance is averaged out it is very close to 8 ohms. Thanks for the advice.