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6 ohms speakers into 8ohm amp

Discussion in 'Home Cinema & Hi-Fi' started by babyface uk, 8 May 2006.

  1. babyface uk

    Wise Guy

    Joined: 5 Aug 2003

    Posts: 1,145

    Location: Lazytown

    Am demoing ( demoing - a real word?) some speakers which are 6 ohm with my amp thats 8 - 16 ohm, there is a warning on the amp that anything under 8 ohm with cause safty circuitry to cut the amp out, do you guyrs think its going to be a problem.

    Amp = Marantz pm7200

    Speakers = Monitor rs6


    Babyface UK
  2. Doug


    Joined: 18 Oct 2002

    Posts: 4,293

    Location: Newcastle

    DO NOT DO IT!!!

    *takes a deep breath*

    A while back I was running a 6ch rotel for my centre and rears. With the amps bridged (to give, in effect, a 3ch amp), the minimum impedance was 8ohms. My centre was 6ohm. All was well for a good 20 mins.

    Cue the smell of burning plastic.

    Suffice it to say, I learned a valuable lesson, and the 2nd amp in that rotel hasn't worked since.

    The speaker survived, though. ;)
  3. DRZ


    Joined: 2 Jun 2003

    Posts: 6,986

    Location: In the top 1%

    I would expect most amps to survive an 'onslaught' like that, 6 ohms isnt a dramatic increase in load compared to 8 ohms.

    It is probably worth noting that whatever quoted impedance is given, it is only an estimation. For certain notes, my speakers present a load of about 3.5ohms - thats from a rating of 8ohms! Usually that sort of thing only applies to low notes and transients but you can see that all amps have to deal with lower than rated impedances from time to time. 6 ohms for the actual amplifier shouldnt do anything dramatic.

    Weaker power supplies may well struggle though, and I cant see the power stage in the Marantz being up to much, because its not actually that powerful (looking at the Class A figures, it is 25W/ch!). Hitting the limits of the internals just comes about faster with 6 ohm speakers, you are asking more from the amp at every amplification level.

    For a demonstration of a speaker, this has clear ramifications - you dont know what is under more scrutiny, the power handling of your amp or the speakers themselves! You cant expect 11/10ths from your amp and also expect to judge the speakers - an amp operating outside of its optimum range isnt ever going to do anything justice.

    If you are going to move to something like a Monitor RS6, you probably want to look at some better amplification.

    For the same money, I have seen Dynaudio Audience 62s go s/h - a 4ohm loudspeaker that is truly magnificent (IMO, of course).

    Let us know how you get on with the speakers anyway :)


    To the poster above:

    I have often wondered what gives Rotel amps the sound they have, I wonder if it is all down to putting in a pathetic power supply? To cook a channel from a load like that (unless you were showing it no respect at all) means something in there is seriously under-rated to my mind!
    Last edited: 9 May 2006
  4. babyface uk

    Wise Guy

    Joined: 5 Aug 2003

    Posts: 1,145

    Location: Lazytown

    update, looking at the Marantz web site, its says....

    The Marantz PM7200 Stereo Integrated Amplifier offers music enthusiasts uncompromising audiophile sound quality and superior flexibility of operation. It delivers 2 x 95 Watts (RMS into 8 Ohms), rising to 155 watts with 4 Ohm speakers.

    Hmm 1 bit of paper says one thing, web site says another...?

    Can't really afford over £700 for upgrade atm, I was thinking speakers first ( with a suitable cd player if I like what I here ) then Amp, trying to get all 3 past the wife after only haveing the current lot 9 months is pushing it. ( but theres nothing wrong with it....etc.... ). No point getting new anything is my hearing is shot from a major earbash. :D

    Babyface UK
  5. daz


    Joined: 18 Oct 2002

    Posts: 24,032

    Location: Bucks

    Looks like the power supply and other components are fine down to a 4 Ohm load in that case. :)

    Most hefty amplifiers shouldn't have a problem with most speakers, certainly at least if you don't crank the volume too far. DRZ has pretty much said everything I would have said, and there's no point re-iterating it. :o
  6. babyface uk

    Wise Guy

    Joined: 5 Aug 2003

    Posts: 1,145

    Location: Lazytown

    Ok thanks, just wanted my mind put at rest, :)

    Babyface UK
  7. chino


    Joined: 20 Oct 2002

    Posts: 387

    Location: Division Street

    I have a PM7200 and some Monitor Audio S6's, pretty sure they're rated as 6ohm, and it works completely fine at any volume I've ever listened at (It's seriously loud at anything over a 1/3 volume).

    It is much better than when I was running them off my old NAD C320 which often sounded strained, fortunately that was only for a month.
  8. babyface uk

    Wise Guy

    Joined: 5 Aug 2003

    Posts: 1,145

    Location: Lazytown

    Had the demo today, Listened to some B&W DM603 s3, Monitor RS6 and Kef IQ7's along with some B&W 602 s3's ( what I'd already got ).Took along my PM7200 amp.
    First the 603's were pretty much the same as the 602's ( funnily enough :D ) so they were out, next the monitors - much tighter sounding, less harsh at the top end than my 602's and a much more balanced listen plus more detail came out that my 602's were missing, lastly the Kef's, I thought they were a little lean in the midrange compared to the monitors.

    So you guessed it, a pair of monitor rs6's are coming my way shortly.
    me thinks me got the upgrade bug :D

    Babyface UK