MC302 driving Klipsch RF7 iis.

Discussion in 'McIntosh Audio' started by Crazeehorse, Mar 9, 2017.

  1. Crazeehorse

    Crazeehorse Active Member

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    I had a quick question before the MC302 gets delivered. The MC302 will drive a pair of Klipsch RF7ii and I think I'm OK hooking them up to the 8 ohm terminals(Klipsch says 8 ohm compatible) but I know when driven hard these speakers can dip into the mid 4 ohm range. Any thought or concerns or am I over thinking things as usual? Thanks for any input.
     
  2. 62caddy

    62caddy Trust but verify Subscriber

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    Those speakers are fairly sensitive; you'd really have to be averaging a good [deafening with those speakers] 100 watts over an extended duration before the amplifier's protective circuitry would kick in, which would also assume the amplifier was seeing 4 ohms all that time.

    Frankly, connections at the 8 ohm taps is rather unlikely to cause problems even if you tried.
     
  3. damacman

    damacman Blown and Injected Subscriber

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    no prob at all
     
  4. Crazeehorse

    Crazeehorse Active Member

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    Thanks guys. I do play things VERY LOUD for a considerable amount of time once a week, usually on a Fridays when the boys are over for pool and beer. :)
     
  5. Chubba

    Chubba Active Member

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    I use the eight ohm taps on the 252 and it seems to sound better than on the four ohm taps.Congrats on your new 302.It is a great amp.My dealer let me bring home a 302 for two weeks and I loved it but the 252 is a keeper.The RF-II's do not mind power if you can take it.Cheers
     
  6. 62caddy

    62caddy Trust but verify Subscriber

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    Fidelity shouldn't be affected but available power will definitely be reduced at the 4 ohm taps. Even if halved, 150 - 200w should still be plenty ample for the RF7s to rock your world to your heart's content. ;)
     
  7. damacman

    damacman Blown and Injected Subscriber

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    Around these parts, we define loud as flashing the Power Guard lamps .... and often!
     
  8. Chubba

    Chubba Active Member

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    If I said they only flash when I turn mine on I would be lying,
     
    damacman likes this.
  9. Chubba

    Chubba Active Member

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    If Mac amps are rated lower than they actually put out ,They do double down as you halve the impedance, throw in the power guard I guess you could hurt your ears/speakers.They are rated for 250 watts and 1000 w peaks. Have Fun.
     
  10. Crazeehorse

    Crazeehorse Active Member

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    lol I will be very careful! My old MX-1000 routinely see 250 to 300 watts peaks and its VERY loud, but still in control and clear. Most of the time in the 10 to 15 watt peak range for normal listening according to the MX's digital peak meter. What I'm hoping for is a warmer sound that mellows out the horns under big loads.
     
  11. c_dk

    c_dk Addicted Member

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    That is not really the amps job but it will certainly drive your speakers in ways you have not heard before.....ENJOY!
     
  12. SilverTpt999

    SilverTpt999 Member

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    This is actually not true, and it's because of the autoformers. The autoformers match the perceived impedance of the speaker load to the rest of the amp, allowing it to deliver the exact same performance and power at multiple different impedance loads. 2 Ohm speakers connected to 2 Ohm taps, versus 8 Ohm speakers on the 8 Ohm taps look essentially identical to the amp. This is why McIntosh spec sheets quote a single level of THD/IMD/etc., and then say something like "XXX watts at 2, 4, or 8 Ohms."
     
  13. Velocityboat

    Velocityboat Well-Known Member

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    Since you got a 302 power difference between MX1000 will be negligble. With my McIntosh speakers the mids and bass excel over the yammie which does 400w in 4ohm. A 500 watt Mc2500 at 4ohm is no cotests. Dual MC2500s at 1000 watts. The Yammie can't even try. Richness and fullness is not and can never be there. Compared to power guard amp. The 91 dB speakers you have please consider a dB meter to keep things safe. You can reach insane dB levels and because all is clean you may want to play louder. The horns can lull you to deafness.
     
    Last edited: Mar 10, 2017
  14. damacman

    damacman Blown and Injected Subscriber

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    You're speaking in generalities that do not necessarily apply to all loudspeakers. The MC302 is rated to deliver peak output current of 60A/ch when driving difficult loads. So, a speaker rated nominally at 8 Ohms, with frequency response dips to 2 Ohms (or even lower), connected to the 8 Ohm tap is no problem for a McIntosh amp such as this one. This has to do with the design of the power supply more than anything.

    The beauty of the autoformer coupled design in conjunction with a power supply capable of very high current is that you connect the speakers to the output tap that best represents the nominal impedance of the speakers without worry of damage to the amplifier. This is simply not possible with many direct coupled designs - especially those with poorly designed power supplies.
     
  15. damacman

    damacman Blown and Injected Subscriber

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    How do the Yammies fare when phase angle is factored? I honestly do not know.
     
  16. Chubba

    Chubba Active Member

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    I have read a few times over the years that if you put a four ohm speaker on the eight ohm tap mac amps stll increase in wattage.Mine sure seemed to heat up quicker and seemed a little louder in that case.Maybe Ron-C could comment on that one.The RF-7II seems more like a four to six ohm speaker.Cheers
     
  17. Matte Grey

    Matte Grey AK Subscriber Subscriber

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    Boy RF 7II 101 dB @2.83V 1 meter. That'll sir things up with an MC 302.
     
  18. Crazeehorse

    Crazeehorse Active Member

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    They do drive easy but can get a bit bright when pushed hard. An a good master though they can be driven to crazy levels with no brightness.
     
  19. 62caddy

    62caddy Trust but verify Subscriber

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    The voltage delivered will be increased however it cannot do so at the same current.

    When you use higher taps than the load is rated for, the amplifier will try to supply the higher voltage at the same current level than it would have done at the matching taps. This can result in overheating because the amplifier is trying to run outside its limits.

    The bottom line is that the amplifier only has a certain [safe operational] capacity of voltage and current, which is what wattage is.There are no shortcuts to getting more power.
     
    Last edited: Mar 10, 2017
  20. Chubba

    Chubba Active Member

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    I was waiting for someone who knows whats going on to comment.Thanks 62caddy.
     

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