4Ohms vs 8Ohms

Discussion in 'Soundcards, Speakers HiFI & File formats' started by ASLayerAODsk, Jul 8, 2011.

  1. ASLayerAODsk

    ASLayerAODsk Master Guru

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    better quality? whats your opinion...?
     
  2. Black_ice_Spain

    Black_ice_Spain Ancient Guru

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    40ohms can work without amplifier and 80ohms will work worse without amplifier.

    Both can work without ampli, under 150 they can, but they may sound low

    In other works, more ohms = better w amplifier.
     
    Last edited: Jul 8, 2011
  3. RagDoll_Effect

    RagDoll_Effect Ancient Guru

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    8 ohms is the standard and best imo :)
     
  4. Tom F

    Tom F Ancient Guru

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    Doesn't matter.

    Depends on the crossover and speaker design.

    8ohm loads are easier on the amp driving them, but 4 nets a bit of extra sensitivity usually.
     

  5. TruMutton_200Hz

    TruMutton_200Hz Ancient Guru

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    In general, 8 Ω is better but it requires a more powerful amp to generate the same sound pressure level. Alot depends on the build quality of the speaker cones themselves, though.
     
  6. RexAeterna1987

    RexAeterna1987 Member

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    doesn't matter. and false about 8ohms. lower the impedance curve is, the more current the amp is forced to draw. 4ohms and below is far more stressful to an amplifier and can even melt the wires inside due to large amount of current is being drawn. there were a few electrostatic speakers with nominal impedance of 1ohms and was known to catch amps on fire and melting wires and blowing transistors cause the demanding current that was pushed&pulled.

    8 and 16ohms are much easier to drive. amps are natural voltage sources and speaker impedance spiking on avg to 50ohms to 100ohms at certain frequency ranges is not a problem for most if all amps but when it dips below 4ohms if the amp does not have a large enough power Transformer and large enough Caps to store and release the energy you will run into major issues and can have blown transistors within the amp or worst.

    when in market for amp and speakers. make sure you get an amp built well enough to handle 4ohm loads no problem. a well built amp will double it's power when impedance is cut in half but most of that power is lost through heat. speakers in general are very deficient when it comes to transferring electrical energy into acoustic energy.

    typically in terms it will take avg of 4ohms if both speakers are same sensitivity to get louder requiring more energy transfer. most speakers are rated @1w at given sensitivity with nominal speaker impedance of 8ohms. with same speaker of 4ohms you will need 2w's to reach the same given sensitivity

    there is much more to it and hard to explain and understand but in all usually a considered ''perfect'' amp will have an output impedance of 0 ohms but that is next to impossible for any amp.
     
  7. The Chubu

    The Chubu Ancient Guru

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    I think that electrical resistance wouldnt affect the sound besides how much voltage you need to get acceptable volume levels. It wouldnt make sense if it affected sound in some (positive) way...
     
  8. RexAeterna1987

    RexAeterna1987 Member

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    speakers impedance are dependent on frequency. yea it's true there is no difference between 8ohm speaker and 4ohm speaker in sonic qualities but that's all dependent on how low impedance the speaker dips on avg. manufactures never tell you the speakers impedance curve and only tell you the calculated/measured ''nominal'' impedance curve that is through-out the frequency spectrum. lot of amps are suppose to be able handle 4ohm dips by design but can't handle the large current for longer sessions if the speaker nominal impedance is on avg 4ohms or lower.

    impedance dips and spikes no matter the speaker and crossover. it's the natural design of speakers. they are naturally depended on the impedance curve through-out the frequency range. that's why watts is never important. the most important spec to look for speakers is the nominal impedance and senstivity@1w. with amps it's very important to know it's lowest output impedance and if the power transformer can handle the large current peaks.
     
  9. SabreWulf69

    SabreWulf69 Member

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    Sort of related to 4ohms vs 8ohms and should get some healthy discussions a going -

    Not sure if this has been brought up before but thought I'd give people a little heads up on my interpretation of the impedance switch/selector on a fair few varieties of Receivers and Amplifiers of home theater and the theory behind the bad things in using it -->

    At anytime I have just discovered, do NOT set the impedance selector on the back of the amp to 4 Ohms, make sure it is always set as high as it will go (usually 8Ohms), all that switch there is for, is for the receiver and amp company's to cover their ass, and with it turned on you can possibly damage your speakers, with it in the lower position you almost half the power output of the amplifier, and reduces the sound quality incredibly as it just reduces voltage, hence you would then be underpowering your speakers, hence introducing amplifier clipping overall a lot earlier than rather if the impedance switch was in the highest position. Most receivers if not all within the last 20-30 years have overheating protection to stop things from dying anyway, so this impedance switch really serves as a backup system, which lowers the overall fidelity. With the amplifier that I have the clipping protector that I have is turned off, but that option on my amp is for when speakers are overdriven and as my amp is matched power wise (wattage) well just under actually with both large and small speakerd connected, my fidelity of the system is improved with it off, as well as turning off the short detection which could also activate prematurely with driving difficult speakers or when the speakers could blow yet again from being overdriven power wise which they aren't, yet again increasing fidelity, and seeing as how I have a slight low load at a slightly lower wattage rating having lower impedance options could theoretically kill my speakers which have no overheat protection of their own.

    Unlike my amp as we have (well I have) seen in the past, my single 2 channel amplifier is $1300 worth of just pure amp, has overheated twice now, shutting it'self off for protection in the process. Having it's remaining 3 protection circuits still active (which are unable to be disabled for good reason), has been far and enough to protect itself, and keep it's intended awesome high quality sound. So in short, disable the impedance switch no matter the speakers you use (set it back to 8Ohms from 4Ohms and keep it at 8Ohms if not done so already).

    A lot of Yamaha's receivers still to this day have this antiquated option and as the article describes, the fact that they even put it in the flagship model of Yamaha's range is kind of self defeating, as it would seem from measurements and technical data to not make any difference. A pure ass-covering tactic in the products it's featured in I would believe. Their excuse is they don't have very big transformers, and under full 100% constant load for ages on end may heat up to inappropriate levels for the consumer (burns and stuff) but yet they still have overheat protection to prevent fires and damage to the components of the receiver itself.

    I say if your gonna make a 4 Ohm amp, do it properly or don't do it at all.

    Loosely what I managed to interpret from this very well described article located here --> http://www.audioholics.com/education/amplifier-technology/impedance-selector-switch-1
     
  10. RagDoll_Effect

    RagDoll_Effect Ancient Guru

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    Yeah, I agree and if you use 4 ohm speakers, be careful aswell, they could get damaged... as I said, there is a reason why 8 ohms is standard! :)
     

  11. SabreWulf69

    SabreWulf69 Member

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    Yeah, my Cambridge Audio Azur 740A Integrated supports 4-8Ohms without the need of a stupid switch be it either on the back of the unit or through software. It's just a nice quality 'dumb' amp that sounds brilliant. I am running a set of DALI Ikon 6 MK2's which are 6 ohms through the amp's speakers 'A' output, and a PSB SubSeries 5i subwoofer using the high level inputs on it from the speakers 'B' output of the amp so I can also choose to cut off the sub when I want. This setup works and sounds excellent, and no magical 'impedance switches' are required :)
     
    Last edited: Jul 9, 2011
  12. ASLayerAODsk

    ASLayerAODsk Master Guru

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    interesting discussion going from a few simple words :) awesome :) well Im using a NAD 7120 and I HAVE set it to 4Ohms for now, the highs SEEM a little tighter and more precise but I only really notice it when I turn the volume up a fair amount. Im driving a set of B&W DM610's which upon further research, Ive found that they are NOMINAL at 4Ohms, so with that in mind, I guess it would be ideal? to set the amp to 4Ohms with that in mind as they are designed? for that kind of load? feedback on that...?
     
  13. Tom F

    Tom F Ancient Guru

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    It depends a lot on the type of load the speaker presents at a particular frequency.

    For example, an amp is going to be a lot happier driving a 4 ohm, pure resistive load than an 8 ohm one with a very high reactance.

    I'd be interested to see a schematic of how an 'impedance switch' works. I suspect it may just change the gain slightly to make it harder to run the amp into the ground.

    In theory, a properly designed amp shouldn't have a problem with a 4 ohm load if it's run within its capabilities - similarly a well designed speaker shouldn't place a very low impedance load on an amp.

    4 ohm speakers can be more sensitive, especially when shown with a voltage (e.g. when you see SPL@2.83V) rather than power input - in these cases a 4 ohm speaker will appear 3dB more efficient. Unless you're matching output impedance, 4 or 8 ohms nominal doesn't matter.
     
  14. Mufflore

    Mufflore Ancient Guru

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    Its not a preference thing, it will be dictated by the kit you have/wish to buy and how you intend to hook it up.

    If you have 4 Ohm speakers, dont put them on an amp that doesnt support 4 Ohms or you can kill the amps output.
    ie if the amp is set to 8 Ohms, 4 Ohm speakers will likely overload/overheat the amplifiers output amps.

    8 ohm speakers should be matched with an 8 Ohm amplifer.
    ie if the amp is set to 4 Ohms with 8 Ohm speakers, you will get 1/2 the power to the speakers for the same volume setting. You might never get full power even on full volume (making the point here, not recommending you try full volume ;)).

    If your amplifier supports down to 4 Ohm speakers and allows you to bridge the amp, in Bridge mode, you should use 8 Ohm speakers otherwise you can again kill the output amps.


    I've used 6 Ohm speakers on many 8 Ohm amps and not had a problem.
    However, they could refuse warranty if a fault develops while using this configuration.
    I wouldnt use rated 4 Ohms on a 8 Ohm amp, or less than rated 4 Ohms on a 4 Ohm amp though.
    fyi
     
    Last edited: Jul 20, 2011
  15. ASLayerAODsk

    ASLayerAODsk Master Guru

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    B&W DM610

    Description:
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    2-way second-order closed-box digital
    monitor system
    1 x 26mm high frequency with metal
    dome, high temperature voice coil and
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    1 x 200mm bass/midrange with
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    and 30mm high temperature voice coil
    on Kapton former
    Frequency Response: 70Hz - 20kHz 2dB on reference axis
    Sensitivity: 89dB spl(2.83V 1m)
    Nominal Impedance: 4 ohms
    Power Handling: 30W - 150W into 4 ohms on unclipped programme
    Dimensions: Height: 490mm Width: 236mm Depth: 303mm
     

  16. Mufflore

    Mufflore Ancient Guru

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    Is there another question?
     
  17. ASLayerAODsk

    ASLayerAODsk Master Guru

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    powering those with an NAD 7120...20W/channel@4ohms or 8ohms?

    the sound is very clean on both settings, of course, but any possible repercussions at underpowering them, even with headroom?
     
  18. Tom F

    Tom F Ancient Guru

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    Like I said before, I suspect the 4/8 ohm switch is just a slight gain reduction.

    The output stage of the amp won't be affected by it - the only repercussions of running it with a less powerful amp is that you might clip on the loud bits - which can burn tweeters. Those are reasonably sensitive speakers though so you should be fine as long as you don't expect insane SPL.

    The only solution for this is more power - the switch won't make any difference.

    Edit: Dug out a schematic out of curiousity - looks like the switch changes the supply voltage.

    I'd be tempted the run at 8ohms and monitor the temperatures.
     
    Last edited: Jul 21, 2011
  19. Mufflore

    Mufflore Ancient Guru

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    If the speaker is 4 Ohm and your amp supports 4 Ohm, use 4 Ohm.
    This was covered in my earlier post but I didnt mention specifically to use 4 Ohm with 4 Ohm, my bad :)

    Dynamic range (quietest to loudest sound change) is improved when you match the resistances (rather than using a higher resistance speaker) as well as max power output is increased.

    It isnt a good idea to set the amp to 8 Ohm and use a 4 Ohm speaker on it.

    Is there anything else you are unsure of?
     
    Last edited: Jul 21, 2011
  20. SabreWulf69

    SabreWulf69 Member

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    THIS vvv

    Make sure to read the article here over at Audioholics which tells you all about it :) --> Setting the A/V Receiver Impedance Selector Switch

    Sorry if this seems like spam, I just think it is pretty important, and definitely relevant to '4 Ohms / 8 Ohms'.

    [Edit]
    Another handy article here --> Heavy Load: How Loudspeakers Torture Amplifiers from Stereophile Magazine also explains some of the effects that different loads have on amplifiers. Another reason why as explained here --> Amplifier Optimized Sound Principle @ DALI my speakers are 'amplifier optimized'.

    I hope this helps :thumbup:
     
    Last edited: Jul 21, 2011

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