Should I use Impedance 4 or 8?

Considering the purchase of a CJ ART 150 amp, I realized that there is only one tap for 4 ohms - and my speakers are rated 8. I tried to find an answer online and I've seen a range of answers from "no problem at all" to "risky for amp and/or speakers" - all with a good degree of certainty. Unfortunately that kind of distribution makes it very hard to actually answer the question. Some suggested calling the manufacturer, so that's what I did last week. The following is what I heard from CJ (I think I understood correctly - don't shoot if details are not fully accurate - but the conclusion remains the same):

A "nominal" 8 ohm speaker is based on a measurement at a given fixed frequency (I believe 1kz but don't quote me on that) and as agwca above was saying, the impedance varies quite a bit with the frequency. For many speakers it dips below 8 esp. in the lower frequencies where it is closer to 4. Therefore they picked 4 as a better match, and according to CJ it works for 98% of the speakers. Only those speakers rated higher than 8 ohms may be a problem, in that case they can reconfigure the amp to a 16 ohm tap but otherwise 4 ohm is the preferred choice (and the only choice on ART 150). 

When I read the technical review of my speakers (Paradigm 9H), the reviewer stated that the "real" impedance (measured) was lower than 8 ohm (less than 4) given the frequency changes and related fluctuations. This is consistent with the above.

One thing to keep in mind is that it is not only about impedance: one needs to also consider amp power (which also changes with impedance) vs. speaker sensitivity. Therefore I assume switching taps on a 25 watt amp paired to low-sensitivity speakers may have more of an impact than a 150 watt amp paired to same speakers. If the amp has to work harder this could explain a less happy sound. In my case, my speakers are 93db sensitivity which is reassuring on the power-matching standpoint.

Anyway, I think I answered the question for my specific case and learned something along the way. Your results may vary due to amp and speaker specs, so your best option may not be same as mine, but based on the comments from a reliable source, 8 ohm speakers should be able to be plugged in 4 ohm taps without blowing up the system. I hope this was helpful.

Considering the purchase of a CJ ART 150 amp, I realized that there is only one tap for 4 ohms - and my speakers are rated 8. I tried to find an answer online and I've seen a range of answers from "no problem at all" to "risky for amp and/or speakers" - all with a good degree of certainty. Unfortunately that kind of distribution makes it very hard to actually answer the question. Some suggested calling the manufacturer, so that's what I did last week. The following is what I heard from CJ (I think I understood correctly - don't shoot if details are not fully accurate - but the conclusion remains the same):

A "nominal" 8 ohm speaker is based on a measurement at a given fixed frequency (I believe 1kz but don't quote me on that) and as agwca above was saying, the impedance varies quite a bit with the frequency. For many speakers it dips below 8 esp. in the lower frequencies where it is closer to 4. Therefore they picked 4 as a better match, and according to CJ it works for 98% of the speakers. Only those speakers rated higher than 8 ohms may be a problem, in that case they can reconfigure the amp to a 16 ohm tap but otherwise 4 ohm is the preferred choice (and the only choice on ART 150). 

When I read the technical review of my speakers (Paradigm 9H), the reviewer stated that the "real" impedance (measured) was lower than 8 ohm (less than 4) given the frequency changes and related fluctuations. This is consistent with the above.

One thing to keep in mind is that it is not only about impedance: one needs to also consider amp power (which also changes with impedance) vs. speaker sensitivity. Therefore I assume switching taps on a 25 watt amp paired to low-sensitivity speakers may have more of an impact than a 150 watt amp paired to same speakers. If the amp has to work harder this could explain a less happy sound. In my case, my speakers are 93db sensitivity which is reassuring on the power-matching standpoint.

Anyway, I think I answered the question for my specific case and learned something along the way. Your results may vary due to amp and speaker specs, so your best option may not be same as mine, but based on the comments from a reliable source, 8 ohm speakers should be able to be plugged in 4 ohm taps without blowing up the system. I hope this was helpful.

Considering the purchase of a CJ ART 150 amp, I realized that there is only one tap for 4 ohms - and my speakers are rated 8. I tried to find an answer online and I've seen a range of answers from "no problem at all" to "risky for amp and/or speakers" - all with a good degree of certainty. Unfortunately that kind of distribution makes it very hard to actually answer the question. Some suggested calling the manufacturer, so that's what I did last week. The following is what I heard from CJ (I think I understood correctly - don't shoot if details are not fully accurate - but the conclusion remains the same):

A "nominal" 8 ohm speaker is based on a measurement at a given fixed frequency (I believe 1kz but don't quote me on that) and as agwca above was saying, the impedance varies quite a bit with the frequency. For many speakers it dips below 8 esp. in the lower frequencies where it is closer to 4. Therefore they picked 4 as a better match, and according to CJ it works for 98% of the speakers. Only those speakers rated higher than 8 ohms may be a problem, in that case they can reconfigure the amp to a 16 ohm tap but otherwise 4 ohm is the preferred choice (and the only choice on ART 150). 

When I read the technical review of my speakers (Paradigm 9H), the reviewer stated that the "real" impedance (measured) was lower than 8 ohm (less than 4) given the frequency changes and related fluctuations. This is consistent with the above.

One thing to keep in mind is that it is not only about impedance: one needs to also consider amp power (which also changes with impedance) vs. speaker sensitivity. Therefore I assume switching taps on a 25 watt amp paired to low-sensitivity speakers may have more of an impact than a 150 watt amp paired to same speakers. If the amp has to work harder this could explain a less happy sound. In my case, my speakers are 93db sensitivity which is reassuring on the power-matching standpoint.

Anyway, I think I answered the question for my specific case and learned something along the way. Your results may vary due to amp and speaker specs, so your best option may not be same as mine, but based on the comments from a reliable source, 8 ohm speakers should be able to be plugged in 4 ohm taps without blowing up the system. I hope this was helpful.

sorry about the multiple posts : I thought it didn't work and pressed several times...

Ok....my comparison experiment went pretty well. And don't get me wrong. When I say 'hum' I am talking about OCD hum here. The 4 ohm taps have almost 0 hum. I mean quiet quiet quiet BUT the snap and 3-D quality goes too. At 8 ops the music is more lively somehow. The 4 ohm speaker connections present a more two dimensional sound stage. Either one could be a livable sound but I'd rather hear that ever so slight hum presence than lose even an ounce of the dynamics of the music. So my conclusion is: for me my Klipsch Lascalas II sound best at 8 ohms which is exactly what the manufacturer recommends after all is said and done. According to my DB meter neither registers any significant difference in volume. My speakers rate a 104 or 105 db sensitivity rating so power is never an issue. My amp produces 20+ watts which will blow me out if I even think about using a full WATT! Thanks everyone for the feedback