4 ohms vs 8 ohms speaker & reciever

Discussion in 'AV Receivers & Amplifiers' started by i9000gt, Jul 31, 2012.

  1. i9000gt

    i9000gt
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    hi guys i got a newbie question and was wonderin if anyone could answer it.

    so my reciever yamaha rx-v673 is spec'd to handle

    7-channel 1,050W = 150W x 7 (4 ohms, 1 kHz, 0.9 % THD, 1 ch driven [European Model])630W = 90W x 7 (8 ohms, 20 Hz-20 kHz, 0.09 % THD, 2 ch driven)1,050W = 150W x 7 (8 ohms, 1 kHz, 10 % THD, 1 ch

    and my speakers are,

    Continuous power handling (IEC - Long Term)140 Watt*Pulse load capacity (IEC - Short Term)180 Watt*Sensitivity (2.83 V / 1 m)85 dB*Minimum amplifier output power recommended50 Watt*

    Impedance 4 - 8 Ohm*Frequency range from/to52 - 20000 Hz*Crossover frequency internal switch300 / 3000 Hz*Tweeter (number)1*Tweeter (diameter)28.00 mm*Tweeter (material)Fabric*Midrange driver (number)1*Midrange driver (diameter)130.00 mm*Midrange driver (material)Cellulose-sandwich cone*Woofer (number)2*Woofer (diameter)130.00 mm*Woofer (material)Kevlar black*MiscellaneousWaveguide tweeter, Long throw bass driver, phase shift compensation*Acoustic principle3-way*Housing structureBass reflex*Housing materialMDF 18 mm*Housing surfaceFoil*Equalisation openings1*Equalisation openings (pos.)Bottom*Removable front coverYes*Net internal volume23 Litres*Integrated standYes*Magnetic shieldingYes*MiscellaneousFront cover material: MDF frame + fabric, Stand: fixed*Terminal clampsScrew terminals*Suitable for banana plugYes*Bi-Amping/Bi-WiringYes*Maximum cable diameter10.00 mm*Lowest frequency (-3 dB)52 Hz

    the yamaha reciever is set to 8ohms by defualt and my speakers can do 4-8ohms. the question is will i benefit in terms of sound quality if i reset my reciever to 4 or 6 ohms instead of the current 8ohms setting?

    thanks guys hope someone can anzwer my question...
     
  2. Nevaborn

    Nevaborn
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    Leave it.

    Lower the ohms the higher the resistance the more work your receiver has to do which will reduce its working life.
     
  3. i9000gt

    i9000gt
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    ok cool. i thought 4ohms sound better then 8ohms also are louder.

    i'll just leave it as it is sounds fine i guess
     
  4. Nevaborn

    Nevaborn
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    Louder may be due to pushing harder as the amp thinks youve a weaker speaker. Id think this would reduce sound quality not enhance tho.

    more ohms less stress on receiver. Thats the main thing.
     
  5. i9000gt

    i9000gt
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    oh cool thanks man i'll just leave it as it is!!

    thankz :)
     
  6. steverobertsbbc

    steverobertsbbc
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    Hmmmm. I disagree with this. If the speakers can present a load as low as 4 ohms, then I would certainly tell the amp that it's driving 4 ohm speakers. Contrary to what Nevaborn states, the lower the ohms, the *lower* the resistance (or impedance) - ohms is a measure of resistance, after all! You're much better off matching the amp and speaker impedances.

    http://www.ehow.com/facts_5913837_speakers-ohm-vs_-ohm.html
     
  7. Nevaborn

    Nevaborn
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    He said the speakers are rated 8-4 ohms. If they are 4 ohm speakers yes tell the amp. I wouldnt run 4 ohm speakers anyway as like i said the increased resistance isnt good for the life of the amp.
     
  8. steverobertsbbc

    steverobertsbbc
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    But it *isn't* an increased resistance! 4 ohms is a *smaller* resistance than 8 ohms. If the speakers are presenting a variable impedance load to the amp that can go as low as 4 ohms, he should be telling the amp to expect a 4 ohm load.
     
  9. i9000gt

    i9000gt
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    hmm very interesting im carefully following this one.
     
  10. Nevaborn

    Nevaborn
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    Oh my your right i feel such an idiot.

    My heads been all screwed around this morning. Im sorry, yes Steve is right 4 ohms will show increased volume due to less resistance to flow of voltage.

    4 - 8 ohm speakers yes you can go to 4 ohm.

    I apologise.

    You can run 4-8 ohm speakers off a a 4 ohm receiver but you cant run 4 ohm speakers off an 8 ohm receiver.

    Aslong as the speakers arent lower ohm rating than what the amp can produce then yes your fine.

    Again im sorry for previous bad advice
     
    Last edited: Jul 31, 2012
  11. dante01

    dante01
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    There's no such thing as a 4 or 8 ohm amplifier. Amplifiers output power to speakers and ohms are units of resistance. Only the resistance a speaker imposes on an amplifier can be expressed as ohms and the output of the amplifier has no influence on this.

    LOwer impedance may mean less resistance be will cause more drain on power from the amplifier. Low power/current amplifiers are not advisable for use with low impedance speakers because the amp cannot keep pace with the the higher rate flow of current from amp to the speakers.

    Home Technology eMagazine - Speaker Impedance, Your Amplifier And You. | HomeToys


    Impedance switching does nothing to improve audio or the flow of current to low impedance speakers and is just something implemented by the manufacturers because of legislation in the USA:

    More here:
    Setting the A/V Receiver Impedance Selector Switch — Reviews and News from Audioholics


    Basically always set the impedance switch on AV amps to the higher value regardless of the impedance of the speakers. The switch does nothing to improve the flow of current to the speakers and merely reduces the rail voltage. You underpower speakers if you choose to set the switch to a lower impedance.
     
    Last edited: Jul 31, 2012
  12. Nevaborn

    Nevaborn
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    I wish you had posted that before i wandered in and got myself all confused lol.

    Yes theres no real ohm rating receiver its all about speakers. Using an ohm compatible rating for a receiver with the load it can handle would possibly be a better way of putting it.
     
    Last edited: Jul 31, 2012
  13. i9000gt

    i9000gt
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    wow very useful information indeed thanks :)
     
  14. Jim2012

    Jim2012
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    Couple of things I can add here.

    Any amplifier has an output impedance (the equivalent of resistance, but for alternating current, which of course is what you have in an audio signal). Power amps have a very low (but measurable) output impedance. This is what allows them to pump out a lot of power without the voltage dropping.

    If you feed a 4 ohm speaker from an amplifier, it will automatically take more power from the amp than an 8 ohm speaker simply because the lower impedance allows more current to flow through the speaker.

    However, generally speaking a higher impedance speaker will produce more actual sound for the same power than a lower impedance one because it is more efficient, so the net effect is the same sound volume while putting less strain on the amp.
     
  15. steverobertsbbc

    steverobertsbbc
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    Conversely, depending on the design of the amplifier, you can end up producing much more heat in the amplifier stages even in the quiescent state when the volume is turned down - and we all know that heat is the long-term killer of electronic devices. Some interesting observations here:

    A/V Receiver Impedance Selector Switch - Page 3 - Audioholics Home Theater Forums

    You also open up the potential for much higher voltage transients to be presented to your speakers.

    At the end of the day, unless you're thrashing it, I don't imagine it makes a blind bit of difference. Most of us here have probably bought both amps and speakers that are operated at a fraction of their safe power handling anyway, due in most part to those pesky things called wives and neighbours. ;)
     
    Last edited: Jul 31, 2012
  16. dante01

    dante01
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    Regardless of the heat dispersion, all modern AV amps have protection circuitry that would protect it regardless of the impedance switching. The switching is surplus to requirements.

    Yamaha have seen no decrease in faults related to heat since the introduction of impedance switching. This suggests that there was never any issue in relation to the impedance and heat induced faults to begin with.

    Use the switching and you are underpowering your speakers.
     
    Last edited: Jul 31, 2012
  17. steverobertsbbc

    steverobertsbbc
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    Which might be a very good thing if you have a nice pair of 25W speakers and an amp capable of delivering 150W p/c, as most of them seem to be these days... My speakers are worth three times my amp, I know which I'd prefer to lose first. :p

    My point about heat was not to do with protection circuits etc, but that pervasive heat is what eventually will kill most electronic kit, usually as a result of the heat drying out the electrolytic capacitors. I spend half my working life replacing capacitors in broadcast kit, or so it seems. Anything you can do to make an amp run cooler is a good thing...

    I don't know we're arguing the toss about this, irrespective of the switch position I doubt any of us are even close to hitting the rails during normal listening, as I previously pointed out...
     
    Last edited: Jul 31, 2012
  18. surfdue

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    I hope I can add another question to this thread???

    I currently have an AV amp with a set of Tannoy 5.1 speakers in the corners of the room and good quality monster cable “hidden”.

    Due to “household” pressure, I am being encouraged to lose the “big” chunky AV amp 

    I am looking at one of the Samsung Home Theatre systems the E5500 or E6500 as it will match the D8000 tv we have.

    I want to keep the wiring and speakers I currently have – will it work? The Samsung speakers are 3ohm and the tannoy’s are 6ohm. Reading all the above it looks like it should be fine.

    I realise the Samsung has proprietary speaker connecters so I will have to “join” my existing cable to the Samsung cable – not ideal (although I have found a US site where you can buy the connectors, so might do that)
    Thanks
     
  19. ashenfie

    ashenfie
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    Four-ohm speakers are becoming more common Most people want slim speakers these days. To accommodate this, speaker manufacturers use multiple small drivers rather than one larger driver. Using two 170mm bass drivers instead of one 210mm driver allows a manufacturer to build a much slimmer cabinet, while actually increasing the bass radiating area (acoustic power) of the speakers. As most drivers are 8ohms, using two (in parallel) results in a 4ohm speaker system. For a given volume setting, a speaker using two bass drivers (a 4ohm speaker) will draw more current from the amplifier than an 8ohm speaker, but it will produce a higher listening volume. This allows the listener to turn the volume down on the amplifier while maintaining the same acoustic level. In this case, the amplifier is not working harder, even though it is driving 4ohm speakers. If, on the other hand, you were to leave the volume control at the same position, your 4ohm speakers would be about 6db louder and your amplifier would be working harder because of the extra current drawn. In my humble opinion, apart from very cheap budget amplifiers and some esoteric output transformer-less valve amplifiers, if an amplifier cannot drive a 4ohm speaker, it shouldn't be on the market.

    I understand the switch are is there because of US requirements, so Pressing the button maintains the Volume readings on the display when using 6Ohm or 8 Ohm Speakers (display DB values are consistant).
     
  20. dante01

    dante01
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    Impedance and Ohms Ω Simplified

    Think of your water pipes and pump at home. The pipe diameter represents the impedance of your loudspeaker; the water flowing through it is power, and the water pump is the amplifier (or receiver). Now, if you have a pipe large in diameter, it allows a large amount of water to flow through it, but requires the pump to work extremely hard to keep up the pressure, this would be considered a “low impedance” situation, the large pipe does not lighten or impede the large flow of water. Likewise, if the pipe were small in diameter, it would allow less water to flow, we will call that “high impedance”, because the smallness of the pipe is impeding or slowing the flow of water, or electricity. Let’s recap: Low impedance equals large flow: High impedance equals slow or low flow.

    Using this same analogy let’s consider voltage and current; voltage (water pressure) and current (water flow) together create power. Now, if your pipes at home were suddenly to widen in diameter the pump would still pump the same or voltage doesn’t change, but the flow (current) would; and therefore you would receive less water flow. The pump would have to provide more power to keep up the flow, therefore lower impedance (large pipes) requires a stronger amplifier (water pump). Now reverse that theory for high impedance, and remember if the pipe is small it is restricting the flow or impeding it and pressure can build up and flow becomes more difficult.

    Impedance is not difficult to define, it’s more defining the actual application of impedance that is challenging.

    · Low Impedance equals large or free flow of power, but requires the amp to work harder to drive enough current to maintain flow. This added demand can be too much for an amplifier and cause it to over heat and shut down.

    · High Impedance equals slow or low flow of power, and can cause restricted flow of current. The level of current influences the volume at which the speaker plays; low current equals low volume.

    Most speakers (the vast majority) are still rated 6 to 8 ohm, even those with multiple drive units.

    Many of the lower end receivers may have problems adequately driving a 4 ohm load. However, many of the better receivers today have a large enough power supply, heat sink area, and current capability in the amp sections to handle 4 ohm loads. You are usually safe running these speakers on the higher end models.

    Some receivers have an impedance selector switch. In most cases it is recommend that the 8 ohm or more setting be used regardless of the actual impedance of the speakers the receiver is powering. The manufacturer puts them there for UL/CSA approvals (in the USA) as well as easing consumer concerns about driving low impedance loads. These switches step down voltage feed to the power sections which will limit dynamics and overall fidelity. Keep the switch set for 8 ohms regardless of the impedance of your speakers and ensure proper ventilation of the receiver. The vast majority of receivers now incorporate a separate safety cutoff anyway so even if the amp does start to reach temperatures above its safe operating range then the amp will shut itself down and put itself into safety mode. More on this here:
    Setting the A/V Receiver Impedance Selector Switch — Reviews and News from Audioholics
     
    Last edited: Oct 18, 2012
  21. PSM1

    PSM1
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    The only issue with running the Tannoys with the Samsung is that it may not have enough grunt to run them. The higher impedance of the Tannoys will mean a lower volume for a given input. hence they will sound quieter. Most all in one systems have pretty puny amps in them so you may struggle to power the speakers at a good volume. You will have to turn the volume up more on the Samsung and this will reduce sound quality (and it is not the best from the start!!!!!). Also I suspect the Samsung amp is passive while the Tannoy is active so you may have issues connecting the 2 together. What receiver do you have? Could you get a slimline one like the Marantz 1403 instead? I would not be going from an AVR to an all in one system no matter what 'pressure' there was!!!
     
  22. surfdue

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    Thanks for the responses.

    I agree the Samsung is not going to really do the job.

    Re AV - last year I had a large Yamaha AV, when we switched to the new LED it came with a slim silver column stand with a glass shelf that can only hold the SKY box.
    I changed the Pioneer VSX-S300, but that could not assign the optical with HDMI. So i switched to the NR1403! I have it sitting on top of the Tannoy Sub in the corner behind the TV and it all works and sounds good. BUT ...
    She wants less "stuff", and I want Surround Sound with a bit of kick.

    maybe I will look at one of the Yamaha soundbar's - the trouble is connecting it to the column of the floor stand !
     
  23. nickfrog

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    Tell her who's in charge, simpler. :thumbsup:
     
  24. dante01

    dante01
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    Why would telling her that she is in charge change anything? :confused:
     
  25. nickfrog

    nickfrog
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    Lol
     
  26. dante01

    dante01
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    I suggest you kidnap her shoes until she submits :lesson:
     
  27. hifibloke

    hifibloke
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    I run my MA Rx8 (4Ohms) on 8 ohm yamaha 1065 setting with no problem
    plus 6 ohm setting has annoying double click one more reason not to use :)
     
  28. dante01

    dante01
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