rt55i and rti10 and ohms

[thejck]

aren't the rt55i's and the rti10's 8 ohm speakers. i was messing around with the back of my receiver and had the speaker cables unplugged and a multimeter sitting close by so i thought I would test them out and they were showing a 4 ohm load. i run 14 guage wire to my speakers and dont biwire. am I missing something.

what happens to the ohm rating if you remove the bridge..

the way i am looking at it right now is if the total resistance showing with the bridge on is 4 then each set of terminals on its own should be 8 the formula to calculate total resistance in parrallel would be 1/R1 + 1/R2 = 1/R

1/8 + 1/8 = 2 /8 = 1/4 there total resistance is 4.... so the rti10 is a 4 ohm speaker??

[MADGSF]

I have seen this stated before but it's important to remember the rating listed by Polk is an average resistance over the frequency range supported by a speaker. I don't think Polk provides an Ohm plot for it's speakers to double check. I also don't think just checking the static resistance is a valid way to measure a speakers average resistance.

[thejck]

yeah i was reading some more stuff about it and just using a ohm meter is not an accurate reading. However how does that apply to the power amp. Wont the power amp look at it and see a 4 ohm speaker for some part.

[MADGSF]

Since the speaker resistance will vary over the frequency range the resistance seen by the amplifier will also vary. Designers know this and the amplifier rating is also for the nominal resistance.

Remember while the speaker resistance may drop to 4 ohms or lower at some point it will also be much higher at another point. I have seen ohm plots of speaker that reach 16 ohms which is of course much easier for the amplifier to drive.