cc1091 Posted December 12, 2002 Share Posted December 12, 2002 I have my speaker wires connected to my 1981 Heresy model 1 speakers (8 ohms I believe) and the Klipsch RP-3 powered tower speakers (also 8 ohms). Since the RP-3s have a separate high frequency and low frequency input, and my MIT bi-wire speaker wires have separate output wires for high and low frequencies, I have the speaekrs connected like this: High frequency wires go to the Heresy, low frequency wires go to the RP-3 sub-woofer only. Since I believe that the heresy is 8 ohms, and since I believe that driving half the RP-3 is equivalent to 1/2 of 8 ohms or 16 ohms <(1/2)*(1/8) = 1/16 or 16 ohms> then I believe that my amplifier is pushing 1/8+ 1/16 = 3/16 or 5.333ohms. Is this correct? What damage may result to my MIT crossover by driving the highs with an 8 ohm load, and the lows with a 16 ohm load? What could I do to balance this load before I feed it back to the speaker wires without getting too close to a 2 ohm overall load? Quote Link to comment Share on other sites More sharing options...
JohnA Posted December 12, 2002 Share Posted December 12, 2002 Well ... One half of 8 ohms is not 16 ohms. HIs dip below 8 ohms in the bass. I'll have to measure mine when I get back home. The RP-3 could be ANYTHING, but since the woofer is powered, it will have an 8 ohm loading resistor or it will be very high resistance (the power amp doesn't need power from the input). The best you can do is measure the DC resistance of each speaker system and then apply the formula, 1/a + 1/b = 1/combined. Quote Link to comment Share on other sites More sharing options...
lynnm Posted December 12, 2002 Share Posted December 12, 2002 The overall impedance of a speaker is not derived by somehow adding the impedance of the LF and HF drivers together. The impedance rating is rather the measured impedance (ie. resistance to alternating current) at some standard frequency with all drivers connected. This gets a little convoluted because the actual impedance can vary widely depending on the frequencies being reproduced. The setup you describe is probably fine (electrically) because the amplifier will "see" the Heresy's and the RP3 as a single system of a nominal impedance somewhere in the region of 8 ohms on average. If both sets of speakers were being driven full range then the amp would see either a 16 ohm load , ( series connection ie R1+R2 <8+8> ) or 4 ohms ,( if in parallel connection (8 X 8)/( 8+8) = 64/16 =4). This begs the question as to whether the RP3 bottom end is a good timbre match for the Heresy's mids and highs. I have not heard the RP3 but I suspect that you might have better sonic results by wiring the Heresy's full range and use the RP3's as subwoofers. The best solution might well be to sell the RP3's and buy a single high quality sub woofer with the proceeds. Quote Link to comment Share on other sites More sharing options...
cc1091 Posted December 13, 2002 Author Share Posted December 13, 2002 The Heresy has always had an annoying rumble in the 80hz to 120hz frequency range (a range that I would always turn down when I had only my Heresys and used an equalizer). I have used the Heresy with the Klipsch KSW-10 running the KSW through the subwoofer out of my receiver or full frequency through speaker leads. The first set-up helped the rumble in the Heresy, but replaced it with the ported bass rumble that I hate. The Rp-3 uses the same bass driver as the KSW-10 (though different model number) but this time the driver is mouned in a sealed enclosure. The result is a much tighter bass that extends far beyond what the Heresy could manage. I'm not sure where or if the MIT cable splits the low frequencies from the upper frequencies, or where that split occurs, but it seems to clean-up the Heresy greatly while still using the Heresy's woofer to cover the range from 700 hz to whereever the break is made (hopefully at 90 hz where the RP-3 expects it to be made). The success I have had with this combination has made me seriously consider a rebuild using the components from the two speaker systems to make one speaker that sounds goo to me. I just don't want to mess with the cabinets and then find that the volumes for the woofers is all wrong. Cabinet design is another thread though. I wrote MIT with essentially the same question. Though they were not familiar with the RP-3, they felt that if it was like any other powered subwoofer, the load on the low frequency portion of the bi-wire cable would be negligible, so essentially it (the whole circuit of Heresy plus RP-3 bass) would be seen by the amp as an 8 ohm load. They also offered that there would be no problem with the proprietary circuit that is a part of the MIT cable. Thanks for the input. Quote Link to comment Share on other sites More sharing options...
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