8 OHM Speakers connected to 3 OHM Amp

Discussion in 'Home Cinema Speakers' started by richardc1983, May 11, 2009.

  1. richardc1983

    richardc1983
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    Hey all,

    Hope someone can help me, I have 2 x Speakers, rated at

    Input Impedance: 8 ohms
    Power Handling: (RMS) 300 watts

    I have had these connected to a Sony Mini System that is rated at

    100 + 100 watts (8 ohms) for the front L & R Channels

    The speakers that came with the system have never been used. I used my own as they are much better quality.

    The system has rear surround and centre speaker for prologic.

    Obviously my speakers are rated at 300watts RMS. However on my old amp I have been able to turn the volume up very loud never had any problems with distortion or clipping or overheating of the Mini System amp.

    I am now upgrading my system to a newer Panasonic system that has more features as the cd player section is faulty on my 10yr old Sony system. I am having a mini system as dont have the space for separates.

    Question is, will my own speakers work ok on the new system and be sufficiently powered.

    New system is rated at:

    95 + 95 Watts (3 ohms) for the front L & R Channels

    Have done searches of the internet and on here and I am still very confused.

    I seem to understand that less is more and have read that a 3 ohms channel is more output than an 8 ohms channel and that it is better to have an amp that is 3 ohm with 8 ohm speakers attached as the amp doesnt have to work as hard.

    I know that the max I will get is 95 Watts per left and right channel (10 watts less than old Mini System) but hoping that the amp being 3 OHM wont mean the system will give less output? As my speakers are rated at 300watts RMS this should be ok as I know im only going to get 95 watts into them.

    Any help appreciated as I am totally stuck and not sure what is what.

    My previous system matched the speaker impedance, so is this why I never had distortion when it was on high volume?

    Will I get distortion on the new system as the impedance is 3 ohm instead of 8ohm?

    Kind regards
    Richard.
     
  2. Andy98765

    Andy98765
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    Those mini systems as you call them may produce 100watts per channel on paper but never all channels driven. The clue is in the power consumption of the unit, what is it 120-150 watts, you can not get more out than you put in.
    Another factor is most amps that deliver 100 watts into 4 ohm will deliver 50 watts into 8 ohm.
    Those systems are designed to drive the speakers supplied.
    Clipping would be your worse nightmare.

    From the Mission site

    Why is it necessary to match my speakers to my amplifier?
    When trying to match the output of your amplifier to the power handling capacity of particular loudspeakers, please try to match them as closely as possible. Remember that more damage can be caused to a pair of speakers using an under-powered amplifier than an over-powered one. Driving loudspeakers with an under-powered amplifier introduces elements of distortion resulting in clipping of the signal. This in turn can lead to damage of the electrical components within the speaker or even damage to the output transistors of your amplifier. If your amplifier is rated at 100w/c, consider speakers with a similar rating. By the same token, if you already have speakers that can operate with amplifiers rated between 25-100w/c, consider purchasing an amplifier towards the top end of the scale, namely 100w/c, rather than towards the lower end.

    The above assumes a REAL AV amp which can in the REAL world reproduce high volume levels.
     
  3. richardc1983

    richardc1983
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    Thanks for that

    How come my existing system works perfectly and is very loud even with oversized speakers?

    This is what I am not understanding, the only diff with the new system is that its 3ohm instead of 8ohm.

    Could this be why my current speakers work ok on the system?

    If I switch onto full volume on current system there is still no distortion.

    I guess they are getting 100 watts per channel currently and this is going to drop to 50watts per channel if I get the new system. :(
     
  4. alsina

    alsina
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    With your 8ohm speakers, the Panasonic amp will technically be able to deliver 35 watts per channel. You shouldn't have any problems with distortion at moderate volumes, but the maximum volume will be drastically reduced.

    Out of interest, what is the Panasonic system you are considering?
     
  5. richardc1983

    richardc1983
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    It appears they have stopped selling here in the uk, but I am getting it off a friend who paid nearlly £550 for it brand new 6mnth ago and only selling cos its too complicated for him. Am paying £180 so getting a bargain really. 6months old still in warranty.

    So I searched the internet and its got good reviews, I love the compactness and it looks neat and the speakers look good.

    They do some really good systems in middle east and america non seem available here that have the 5:1 setup.

    Heres the link to the system on Panasonic Middle East Website:

    Panasonic Middle East - ideas for life

    You can view it on the right hand side in PDF documents, specs etc.

    Theres a manual I found here:

    Mini Hi-Fi Owner's Manuals (SC-NC9 - DVD Home Theatre System with Pumping Bass) - Panasonic Australia

    Download it at bottom of the screen (PDF)

    EVeryone will tell me to spend my money on separates but I have tried this and tried a yamaha AV amp. That provided 8ohm and 90watts per channel and this just didnt have the depth to the music.

    Even with the bass turned right up there wasnt that punchyness that these midi systems give you with the bass boost buttons that they have.

    It didnt seem to be powerful enough for my speakers despite the 8ohm and 90watts per front speakers.

    I think AV amps are meant for film and tv, whereas the midi systems have two amps in I think that uses a dedicated music amp when prologic not being used.

    Despite my current sony RX100AV midi system that runs them fine at 100watts per front speakers @ 8ohm.

    Its mainly for dance music you see and watching films on tv. Until I buy my house which will be in a few yrs I wont be spending a fortune on entertainment until I can do it all in my own place. I rent at the mo.

    Confused with it all, some people are saying I will get about 50watts per front speaker on 3ohm. Others less?

    The speakers I run are PA Speakers as we use the room as a party room too they are Mackie C300. Everyone will say im mad for using them but I like the nightclub sound you get from PA speakers.

    Like i say existing MIDI system handles them fine apart from cd player is faulty now after heavy use and 12yrs age!
     
  6. BlueWizard

    BlueWizard
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    It sounds like the speakers you have are relatively large. Most people think that bigger speakers are harder to drive, but in general, that's not true. Bigger speakers have bigger magnets and bigger cabinets, and that usually makes them more efficient.

    Next in the issue of impedance, there is no such thing as a 3 ohms amp. There are only amp whose power is rated at 3 ohms. But that is something of a cheat by the manufacturer as the lower the impedance, the higher the apparent power.

    But amp power is inversely proportional to impedance. In a perfect amp, if it puts out 100watts to 8 ohms, then it will put out 200watts to 4 ohms, and 50 watts to 16 ohms. But keep in mind, that regardless of the demands of the speakers, the amp is the same. It has the same power supply regardless of output impedance, and the voltage limits and current capability of the power supply are the true limits of the amp.

    In your case, the alleged 95 watts to 3 ohms, is 35.625 watts to 8 ohms. That's not great, but it will probably get the job done.

    Lastly, lets talk about amp power relative to speaker power, again, these are maximum sustained values. If you have 100 watt speakers, you can use up to a 100 watt amp on them. Though if you use common sense you can safely use up to a 150 watt amp with 100 watt speakers. Since you have 300 watt speaker, you have nothing to worry about.

    In some cases, you will see speakers with a minimum power requirement, but even that is not absolute. If you see something like 40w to 100w, that simply means the manufacturer is recommending at least 40watts to get the best out of the speaker. But also remember that the speaker Sensitivity rating is made at only ONE watt. So, the speakers are certainly capable of functioning with less than the recommended minimum power.

    Since you are getting a pretty good deal in general, and the overall price is very low, you have little to lose. Try it out, if you like it, then problem solved. If not, find someone to buy it from you and look for something new.

    In short, if you have 8 ohm speakers, you've got nothing to worry about. The amp should have no trouble driving them. If may not drive them to perfection, but in terms of damage or things to worry about, there is little to be concerned with.

    Just one man's opinion.

    Steve/bluewizard
     
  7. Andy98765

    Andy98765
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    That Panasonic unit has a power input of 165watts, allowing for losses the electronics get 140 watts, split that over 6 speakers to allow ALL Channels driven and you get 23 watts per channel (ALL Channels driven) or around 60watts per channel two channels driven. THAT is REAL world figures. When these systems quote 100watts per channel they often mean 1 channel driven.
    As for the 6500watts output it quotes that would be for about 1 micro second for one instance, basically bumkum and a totally pointless completely over inflated figure to quote. It does quote 590watts RMS out well yes if ALL channels COULD be driven at the same time, split that figure over 6 speakers and you are back at 100watts output as I stated above into one channel.
    The rules of Physics do not allow output to be greater than input.
    Agree budget AV amps like the Yamaha again with only 200+watts power in would struggle.
    If you want MUSIC power then look at something like this with 850watts power consumption (5x100watts all channels driven) CAMBRIDGE AUDIO AZUR-540RV3-SIL at Richer Sounds - HI-FI Separates, Home Cinema, Speakers, MP3 DVD Portables, Plasma LCD, etc.

    All good Musical amps, either AV or stereo have very large power supplies/consumption, i.e. far greater than the output.
     
  8. richardc1983

    richardc1983
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    Thanks for that Steve, I have passed on my thanks.

    How come then my current system is rated at 8ohm and outputs 100watts per front speaker.

    yet the new one its going to be 35watts per front speaker into 3ohm? So its considerably less power? Whereas the current system is rated for 8ohm.

    It even lists what the output is for each speaker when connected.

    Your right I use PA speakers for the front due to having big parties etc and this is used in the party/tv room. THey are Mackie C300 as I say the current system powers them fine even on full volume no distortion but people tell me thats because they are large speakers and can handle it.
     
  9. richardc1983

    richardc1983
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    Thank you also for your informative post. I thought that they had transformers etc inside to step the power up this is how i thought they worked.

    My current system is rated at 250w power input with an RMS of 250watts. Which would seem correct and all the rms adds upto the input (input is same as out put) Shared out across them all that adds up, 100w x 2, 1 x 25w & 2 x 12.5w = 250w. I use it in 2 channel music mode for music so that extra 50watts gets shared out 25watts to each front speaker extra.

    But the new system doesnt add up because the power input is a lot less than the RMS power.

    As you say 165watts is a lot less than what I have now, so its probably not going to be as punchy and im only going to get max 60watts per channel in 2 channel mode... not so good.

    The yamaha I had was only 250watts im sure. That sounded flat and weak despite a claimed 95watts per channel into 8ohm? I take it this was wrong? BUt the current mini system I have is 250watts input and drives them perfectly. I know I dont get the 300watts rated input the speakers have on them though.

    It seems like I need a high powered amp like you suggest but why cant I get another amp that runs the speakers like mine does now that uses 250watts?

    I was looking at high range yamaha that quote 910watts output RMS but it dont give the input power.

    Is there any other amps on line that would suit my needs that would run my speakers perfectly with plenty of power to drive them?

    Cheers for ur help so far guys.
    Richard.
     
    Last edited: May 11, 2009
  10. BlueWizard

    BlueWizard
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    As Andy points out, it is unlikely that your previous system truly delivered 100watts in real life, but none the less, a rated 100 watts per channel is a lot more than a rated 35 watts per channel.

    A 100 watts in a dynamic music situation is a lot better than vaguely 35 watts in the same situation.

    Also agree with Andy in saying that even a better AV amp, is still not as good a a first rate stereo amp. Though the suggested Cambridge 540R is excellent value for the money. Far better would be the Cambridge 640R, but the price tag on that is not cheap.

    Let's look at your potential new system in a different perspective. It is, if I understand correctly, an all-in-one micro system. Take all the components, and divide them into the total cost, and then tell me the value and worth of each component?

    Basically, what you are buying here is a glorified boombox, but for some people, that's all they want.

    Likely, the excess bass you are hearing, is merely a bass boost circuit to give the impression of bass, that and certainly a substantial amount of distortion that you are perceiving as bass weight.

    Next I would ask what your priorities are? If you want to Rock The House playing music, then four substantial speakers and a nice stereo amp are going to do a better job of it. And, you can still listen to video through the stereo system, you just don't same whooshing and swooshing sound effects. Or, you get them, but not in the same way.

    All-in-one systems seem like a good deal, but combined together, each component is of crappola quality. Far better to build a component system over time, where you can control the quality and put it where you need it most.

    Again, the new system you are look at, is going to be usable. But it is not going to equal a true 100w to 8 ohm amp. And, in my opinion, for music, an AV amp is never going to equal a stereo amp.


    Steve/bluewizard
     
    Last edited: May 11, 2009
  11. richardc1983

    richardc1983
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    THere is a groove button on the curreny sony system that increases the bass output this makes it sound full. But my friends are impressed at how it sounds in music mode.

    So even the Cambridge Audio mentioend above is that not going to sound as good in music on my speakers as my sony system currently does? Despite using 850watts power input?

    I mean how do the midi systems do it? Do they have a separate AV amp and a separate stereo amp? Despite cheaper components to do so?

    There doesnt seem any point in getting this small system as 35watts is a substantial difference from 100watts. IF it was rated at 8ohm then at least we wud have figures that were closer to what my speakers are rated and we could go with this.

    my current midi system was probably one of the last true type Midi system, as the new ones all seem to be rated at 6ohm so clearly cheaper components and not designed to last the 12 yrs that mine has done.

    My brother had one rated at 100watts RMS per channel and didnt sound nearlly as loud.

    The cambridge audio does sound a goer though if it can do all that.
     
  12. kfalls

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    The 8ohm load will actually be an easier load for the receiver to handle. The lower the impedance the more current is drawn. It's actually when the current draw exceeds the spec for the amp that the outputs or other components will heat and fail.

    Most listening is done using less than 30W of power, which is loud depending on the efficiency of the speaker. If the speakers are in the 87db/w/m to 90db/w/m your receiver should be able to handle them without problem.

    If on the other hand the receiver was rated at 100w 8ohm and your speakers were rated at 3ohms, the amp may not be able to handle the extra current. It's possible the wire in the transformer could be too thin, or the outputs too small for the extra current.

    Another thing to consider is Panasonic receivers in general (even their non HTIB systems) have higher distortion. Where a good AV receiver, such as the Yamaha may have a spec of .01% THD at rates output, the Panasonic could have between .6%-.9% or almost 90 times the distortion. Still not to worry since the human can't hear distortion until it gets above 1%.

    As long as you listen at reasonable levels and pay attention to warning signs, woofers bottoming out, cymbals sounding like eggs frying and the amp getting HOT, you should be OK.
     
  13. Jwr1985

    Jwr1985
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    Hi sorry to butt in. I have a smilar question. I recently sold my Denon dra-f101 and matching cd player running acoustic solutions av120 floorstanding speakers. I kept my speakers.

    I bought a panasonic sc-akx400 which is 600w its a lot more powerfull than my previous system. But the bass isnt as deep its more powerfull but punchy.

    My main question is can i try using my acoustic solutions speakers in place of the panasonic speakers. The acoustic are 8ohms and the panasonic are 3ohms. I love the system asthetically but i have a bit of buyers and sellers remorse. Will i damadge either the speakers or the system? Thanks to anyone who can give me some advice. Many thanks. John
     
  14. noiseboy72

    noiseboy72
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    Yes, you can. You will just end up turning the volume control up a bit more.

    To get good efficiency , many budget systems use low impedance speakers and some derivative of a class D amplifier. These need a smaller, lower power, lower voltage power supply which is much cheaper to make. Same thing has happened in car Audio for years.

    The system will have about half the power available on an 8 Ohm load, which is only a few db quieter in real terms.
     

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