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Impedance important question

Discussion in 'Home Cinema Speakers' started by arielshiran, Jan 30, 2005.

  1. arielshiran

    arielshiran
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    Hi,
    During my search for the best possible sat+sub system in my budget I have listened to some M&K speakers from the K series. I wanted to use them with a receiver like Denon's 2105/Marantz 5500 or something alike. However, I've noticed that some of the K series speakers are 4 ohms of impedance while others are 8 ohms. I wanted to know:
    1) Is there any problem connecting two different impedance speakers in the same system?
    2) Can there be any damage to the speakers or to the receiver because of connecting 4 ohms speakers to these receivers? Can the receivers handle such speakers (In their specs all of the data is written about 8 ohms impedance)?
    3) What impedance should be used with a more powerful receiver/amplifier- the 8 ohms or the 4 ohms? Will these receivers be powerful enough for "pushing" 4 ohms speakers? will they be powerful enough for 8 ohms speakers?
    4) I have seen that most of the speakers systems (MS Genie, MA Radius, Castle CC3, Tannoy Arena) are all 8 ohms of impedance and heard that for using 4 ohms speakers I need a much more powerful receiver but this is something I don't understand. It seems to me that the opposite is true and using 4 ohms speakers can cause them damage. What is correct? Why are the M&K K7 and K4 4 ohms of impedance? Does this give them any advantge?
    Please help.
    Thanks guys,
    Ariel.
    :thumbsup:
     
  2. KHCC

    KHCC
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    Mornin'

    I'm going to have to keep this short, as the theory and physics behind this is quite complicated. In the short, using 4Ohm speakers with any amp will get you a more dynamic sound, some might say gritty or bright, as the amp has half the resistance therefore producing more power (although not twice the power as amplifiers tend tobe about 50% efficient) To produce that bit extra, it is having to draw more from it's power supply than the designer intended, so therefore strains a little which then gives you the more dynamic sound liked for movies rather than the laid back sound associated with hifi. If you have an amplifier that 1) has the reserve power or 2) is designed to run down to 4Ohms i.e. THX amps (as most THX speakers are 4Ohms) then you have nothing to worry about apart from matching the right speakers to the right amp for the desired sound i.e. bright amp/bright speakers = possible harsh sound preferred by some for movies (and some for music), laid back amp/laid back speakers = soft sound preferred by some for HIFI (not by others - uninvolving), laid back speakers/bright amp (or visa versa) = possibly good all-rounder, (not bright enough for some, too bright for others!!!) There are other factors to take into account like the actual character of the speakers of amp etc...

    M&K produce 4Ohm speakers as they assume their speakers will be used with kit that is on a par with them, whereas other brands that you mention are either aimed at the starter market or their background is HIFI so therefore don't believe in the 'cinema sound' it's all personal taste not right or wrong.

    Different impedences of speakers in the same system isn't a problem, as I know of at least one company who use 4Ohm speakers on the front three and 8Ohm speakers for the rears in a THX system.

    To answer your question, I don't think that the 2105 is quite man enough for the job with the M&K's, I have heard the M&K on our Denon 3805 and it was quite breath taking. The 2805 would probably do an admiral job, it all depends on your size room and how loud you like it.

    Any other questions, give me a call as email takes so long.
     
  3. KHCC

    KHCC
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    Oh I forgot to add, if you use low impedance speakers with an amp that can't do the job, it can damage the speakers as the amp may go into clipping therefore heating up the voice coils and blowing the speakers. Damage can also occur to the amp, although these days they seem to have protection against impedance and heat.

    Hope this helps.
     
  4. Reiner

    Reiner
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    No problem at all.

    A speaker with a lower impedance presents a higher load, thus is more demanding on the amp. The same applies to a low sensitivity (measured in dB). A combination of low impedance and low sensitivity is therefore the worst case.
    However most amps have a protection circuit that will prevent damage to the amp itself but it's possible that the amp is driven into overload and clips (outputs DC instead of a sine wave), which in return can damage the speaker as they don't like DC (direct current).

    However practially it should be no problem to connect 4 Ohm speakers, just keep your volume within normal levels and lower the volume when it starts to distort or switch off the amp if it keeps on shutting-down.

    Hint: Setting speakers to SMALL (thus routing the bass to the subwoofer, if present) helps to reduce the load.

    I think the first question cannot be asked, a powerful amp can be used with any impedance.
    A good, or very good, amp will double it's output power if the impedance is halved (those that do up to 1 Ohm cost more money than a middle-class car though).

    Generally you do not want to put too much load on the amp, but if you have speakers that are hard to drive you do need powerful amps, which means they have a potent power supply and hence are usually big 'n heavy (and expensive).

    That is correct, see above.

    As said a 4 Ohm speaker presents a higher load but doesn't necessarily cause damage, it can (in the unlikely event that the amp's protection circuit fails or it doesn't have one).


    Most receivers, in particular those in the budget market, have weak power supplies and hence don't like high loads, obviously causing the manufacturers to be over-cautious and thus they do not "allow" 4 Ohm loads.
     
  5. arielshiran

    arielshiran
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    Denon 2105/Marantz 5500/Yamaha 750 work well with the following set:
    2 M&K K5s at front (8 ohms resistance), M&K K7 as a center speaker (4 ohms), 2 M&K K4 as surrounds (4 ohms resistance)? The room's area is about 30m^2 (5mX6m) or should I stick with other speakers (Tannoy Arena, MA Radius, JMLAB sib&cub, MS Genie) if I want to use such receiver?
    Thanks a lot,
    Ariel. :thumbsup:
     
  6. eviljohn2

    eviljohn2
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    Very good explanation by Reiner.

    The Marantz might just do them justice but I think you should be looking at a more expensive amplifier or speakers other than the M&K's.

    The downside of expensive things is that you need more expensive things to make it all work. :)
     
  7. arielshiran

    arielshiran
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    and some sellers said that there won't be any problem using the configuration of K4s as surround, K7 as center and K5s as front with a Denon 2105 and that there will be no problems at all-not of power, not of damaging the speakers and not of damaging the receiver. According to what you wrote here, this configuration may be faulty and/or not powerful enough. I am quite confused...
    Please let me know what you think I should buy as my speaker system if used with a receiver in the Denon 2105 level:
    1) M&K K5 X 4 (8 ohms) + K7 (4 ohms) as center.
    2) 5X M&K K5.
    3) MA Radius 90 X 4+Radius 180.
    4) Tannoy Arena.
    5) MS Genie.
    6) JMLab Sib & Cub.
    There are so many good reviews on M&Ks K series speakers. Are their performance justify their price? Would a set of 5 K5s be a better perormer than (for example) MA Radius 225X3 (Center+Front)+MA Radius 90X2(Surround) which cost about the same?
    Thanks,
    Ariel.
     

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