Help: When an Amp can output more than your speakers can handle...

Discussion in 'Archived Threads 2001-2004' started by Greg Robinson, Jun 15, 2002.

  1. Greg Robinson

    Greg Robinson Stunt Coordinator

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    Hi everyone. I have what may be a very silly question. Up until now, I've always used an A/V receiver (currently HarmanKardon 310) for my amplifying needs. I'm currently powering 5 Axiom "bookshelf class" speakers (4 M1Ti's and 1 VP50 center). My receiver lets me call them all "SMALL" and my Energy eXL-s10 sub takes the brunt of the signal. Now my HK receiver outputs 60 Watts x channel (WPC). My Axiom bookshelves are rated at a max of 125 WPC. (Don't worry, my question is rapidly approaching...)

    Recently I've started work on finishing half my basement to create a Wife-Approved Home Theater. As a result, in addition to front projectors, I've started looking at 6 and 7 channel hardware, namely the Outlaw 950/770 combo. The Outlaw 770 Amp is rated at 200 watts RMS. First off... this has always been a mystery to me - what is RMS and how does it relate to WPC? Same thing? Assuming the Outlaw's rating of 200 and my HK's rating of 60 is an apples-to-apples comparison - does this mean my Axiom's are useless with this badboy? Does the "SMALL" setting on the 950 reduce the power to each speaker or purely the amount of bass?

    BOTTOM LINE... If I want the 950/770 - do I need a full set of new speakers that can handle a minimum of 200 watts? Or do I have my specs and math wrong? THANKS!!!
     
  2. Mark Larson

    Mark Larson Supporting Actor

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    No, you don't need a new set of speakers. Rarely does a speaker die from too much power (although you will fry the coils if you use megawatt power).
    The speaker's enemy is too little power, which leads to amp clipping. Have you looked at the HTF Primer? Follow the link from the Basics forum.
     
  3. Joseph_W

    Joseph_W Stunt Coordinator

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    Greg,
    First of all, RMS is root mean square, the method used in measuring Watts. I expect everyone uses RMS now so I wouldn't worry about the comparisons. Just don't compare peak watts with average (RMS) watts.

    Don't worry about driving speakers with powerful amps. The speakers will draw no more current than they need. The beauty of large amps is the "headroom", the ability to provide clean voltage and current at any volume. Smaller amps may clip and distort at higher volume which is much worse on a (any) speaker.

    The small setting on your receiver diverts low frequencies (bass) to the sub instead of the speaker. There is a small relationship to power since the speaker will not draw as much low frequency current.

    The 950/770 will work great with your existing speakers.

    Joe
     
  4. Greg Robinson

    Greg Robinson Stunt Coordinator

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    Wow - that's great news! Can't say I was looking forward to replacing my Axiom's - they're great! So if I might... why does Axiom, for example, state in their speakers specs "Max Amp Power" if it's not really an issue? What causes a "blown speaker?" Thanks!
     
  5. David Werner

    David Werner Stunt Coordinator

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    Greg -
    RMS (Root Mean Square)
    Generally, the average continuous power output an amplifier is capable of producing; power output an amplifier can produce consistently over extended lengths of time. RMS power contrasts to peak power, which is used for brief moments in order to recreate sudden, high-energy sounds (transients). RMS power can be produced continuously for the length of time the amplifier is in operation. It is the most important of the two power ratings (RMS versus peak) when researching an amplifier. RMS is technically the value of a particular waveform. When we say an amplifier has power output of some RMS figure, then we mean that amplifier is able to produce a particular waveform continuously (with that waveform requiring a certain level of power to be reproduced based on its amplitude).
    W/ch (Watts per Channel)
    Measurement of power output for each channel in an amplifier. A two-channel amplifier, for instance, may have a rating of 200 watts per channel (200 W/ch). This means that each channel of the amplifier can output 200 watts of power driving two separate speakers each with 200 watts.
    Almost all amplifiers with more than one channel will feature equal power across their channels (equal watts per channel). Surround sound audio systems should feature equal power output (equal watts per channel) across the front three speakers (left front, center, right front). While it is less important to feature equal power for the surround channels (power equal to the front channels), digital surround sound formats such as Dolby Digital and DTS are making this more and more vital. The optimum configuration for a surround sound system is equal watts per channel across all channels (except for a subwoofer, which often may need more power if possible).
    This and other info can be found at http://www.audiovideo101.com/dictionary/
    I read the online manual of the 770 and it states on page 2, they are not responsible for damage to speakers that are not rated for the power of their amplifier. Good luck.
     
  6. Joseph_W

    Joseph_W Stunt Coordinator

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  7. Chu Gai

    Chu Gai Lead Actor

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    RMS=root mean square basically it means continuous power and is generally specified into how many ohms and what %distortion. so you may see specs like 100 watts [email protected] ohms THD
     
  8. Greg Robinson

    Greg Robinson Stunt Coordinator

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    thanks everyone for the great info. That legal disclaimer mentioned above from Outlaw's manual does concern me, I'll admit. I guess I'll have to do some reading on this and see how important it is. Are there any other 7 channel amps out there (in this price class - doubtful i know) that don't output quite so much power? Perhaps one that would be less risky for my speakers? I realize I'm being the ANTI-Tim Allen right here asking for LESS Power! [​IMG] Just curious. Thanks again!
     
  9. David Ison

    David Ison Stunt Coordinator

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    Greg
    i still think you missed the point, the amp you are considering will be just fine , you run the risk of damage with aLOWER powered amp , by driving it into clipping this is what causes most damaage to spkeakers, usually blowing the tweeter, also remember when and if you do upgrade your speakers you will have the power to do so.
     
  10. Chris PC

    Chris PC Producer

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    The thing to be careful is to make sure not to overdrive the amp into clipping. For instance, if your speakers handle 100 watts RMS each and you use a 50 watt RMS per channel amplifier or receiver, you can overdrive the amp into clipping. If you get a 100 watt amp, you still have to be careful not overdrive the amp. There is a point where there is so much power, that you won't clip, and that is ok, but its still possible to blow speakers without clipping. Its really the most likely to blow speakers when an amp is overdriven into clipping. So what I am getting at, is that don't think because your amp is powerful, it won't clip, its just less likely to clip. In your case, I think its safe to say the amp is unlikely to clip. If you had an amp with 150 watts and your speakers were rated for 120 watts, believe me, IF your amp did clip, it'd be worse than a 60 watt amp clipping.
     
  11. Greg Robinson

    Greg Robinson Stunt Coordinator

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    David - I thought I had the point understood - but the comment about the Outlaw manual stating that they're not liable if you use speakers that can't handle the amp's power was (i thought) in contradiction to "the point." As I'm reading you all - more power is better as it allows more headroom and greatly reduces the risk of clipping, which is what is dangerous to speakers. if that's it - i got it. But then why would Outlaw say that? Wouldn't they, if that were the ideal setup - ENCOURAGE the higher powered amp with any speakers? Off to do some reading in the Primer thread. Thanks again everyone.
     
  12. Mark Larson

    Mark Larson Supporting Actor

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    Probably because they don't want to be held responsible for all the people reading this thread, going home, and pumping their music till the amp clips and the tweeter vaporizes! [​IMG]
    In moderation, you'll be fine. If you lived with your speakers in many environments and a lower powered receiver, i don't think you'll have problems.
    The volume knob on my TX-8511 (100 wpc) has only gone to the 1 O Clock position once - when i was holding a party. And the amps haven't clipped once... So you know.
    (Stereo reciever, two-way towers, 91 dB efficiency)
     
  13. Mark Tranchant

    Mark Tranchant Stunt Coordinator

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    Just to clarify the main point here - if you're going to run the new system at the same perceived volume as with the old system, you'll be using the same power as before.

    The worry here is similar to "I've just replaced my old slow car with a really fast new car - will I lose my licence?". Just observe the speed limit as you did before.
     
  14. Mark Larson

    Mark Larson Supporting Actor

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    Hmm...more like, "Will i have problems if i feed my Taurus 100 RON racing fuel?" [​IMG]
     
  15. Holadem

    Holadem Lead Actor

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    With that much power, your ears will go first - which is a good thing 'cause then you won't have to worry about the speakers going anymore, ever [​IMG]
    --
    Holadem
     

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