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  1. #1
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    Amp Power & Speaker

    Hey, just like to know how much amplifer power can a speaker take so as not to damage the driver ?

    I heard that higher power wattage is better for a speaker. Example amplifer with more than 100W per channel at 8 ohm can drive a speaker rated at 100W 8 ohms more efficiently.

    If that's so, how much amplifer power should a speaker ( example 100W 8 ohms ) be driven that will not damage its driver ? Is there a calculating method ?

    Thanks.

  2. #2
    Suspended markw's Avatar
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    There's no set formula. All those ratings are approximations anyway.

    The speaker ratings are virtually meangless and most revceiver's power ratings are highly exaggerated in order to look good on paper.

    You can safely drive any speaker with any amplifier as long as you use common sense and remember the main rule in hi fi, which is: "If it sounds bad, turn it down ...NOW!"

    When something starts to sound bad, it's either the speaker or the amp complaining. The amp may be driven well into clipping (not good) or the speaker may be trying to move more air than it's capable of safely doing. In either case, the speaker won't last too long.

    I've driven teeney minimus 7's (rated @ 40 watts) with a Marantz 2270 (rated at 70 wpc but actually more like 90 in the midrange) to satisfying, but sane, levels for quite a while without damage.

    Of course, if I were to be stoopid enough to try to boost the bass to wall shaking levels and/or try to achieve room filling levels I'd have a problem but, using the above rule, all has been well.
    Last edited by markw; 06-18-2005 at 02:43 PM.

  3. #3
    Super Moderator Site Moderator JohnMichael's Avatar
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    More tweeters are destroyed by a low powered solid state amp clipping long term than a powerful amp giving undistorted power.

  4. #4
    Forum Regular N. Abstentia's Avatar
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    Impossible to answer that question. Even if you got it down to getting someone to say "you should be running a 50 watt amp to your speaker" that's useless. There's a big difference in cheap Sony/Yamaha/JVC 50 watt amps and nice Aragon/Anthem/McIntosh 50 watt amps. The cheap Sony/Yammy/JVC will send lots of distortion along with the power so the speaker actually won't handle as much because of the distortion. Howver the higher end amps will send nothing but clean power so they will actually handle more than the 50 watts.

    Plus the cheaper amps are not rated the same way as the high end amps, so 50 watts from a cheap amp is not the same as 50 watts from a high end amp.

    It also depends on how the speaker and crossover are rated. So, as I said...impossible to answer simply.

  5. #5
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    Quote Originally Posted by markw
    The speaker ratings are virtually meangless and most revceiver's power ratings are highly exaggerated in order to look good on paper.

    You can safely drive any speaker with any amplifier as long as you use common sense and remember the main rule in hi fi, which is: "If it sounds bad, turn it down ...NOW!"

    When something starts to sound bad, it's either the speaker or the amp complaining. The amp may be driven well into clipping (not good) or the speaker may be trying to move more air than it's capable of safely doing. In either case, the speaker won't last too long.

    I've driven teeney minimus 7's (rated @ 40 watts) with a Marantz 2270 (rated at 70 wpc but actually more like 90 in the midrange) to satisfying, but sane, levels for quite a while without damage.

    Of course, if I were to be stoopid enough to try to boost the bass to wall shaking levels and/or try to achieve room filling levels I'd have a problem but, using the above rule, all has been well.
    Bravo! I'm happy to see people wich understand the rules of hi-fi and good common sens!

  6. #6
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    Quote Originally Posted by JohnMichael
    More tweeters are destroyed by a low powered solid state amp clipping long term than a powerful amp giving undistorted power.
    You're right too!

  7. #7
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    Quote Originally Posted by N. Abstentia
    Impossible to answer that question. Even if you got it down to getting someone to say "you should be running a 50 watt amp to your speaker" that's useless. There's a big difference in cheap Sony/Yamaha/JVC 50 watt amps and nice Aragon/Anthem/McIntosh 50 watt amps. The cheap Sony/Yammy/JVC will send lots of distortion along with the power so the speaker actually won't handle as much because of the distortion. Howver the higher end amps will send nothing but clean power so they will actually handle more than the 50 watts.

    Plus the cheaper amps are not rated the same way as the high end amps, so 50 watts from a cheap amp is not the same as 50 watts from a high end amp.

    It also depends on how the speaker and crossover are rated. So, as I said...impossible to answer simply.
    Very good answer too!

  8. #8
    Loving This kexodusc's Avatar
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    Quote Originally Posted by JohnMichael
    More tweeters are destroyed by a low powered solid state amp clipping long term than a powerful amp giving undistorted power.
    In my experience, most tweeters are destroyed by low powered SET's and SS amps with high distortion that send upper harmonic information to the tweeter...the tweeders load goes from a fraction of a watt to multi-watt figures pretty fast and then boom.

  9. #9
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    Grigore,

    I just posted this in another thread, but it's worth reading:

    The max power handling rating generally refers to the voice coils ability to absorb electrical energy without damage...bigger coils handle more. This figure is quoted RMS so in reality, the musical power rating is much, much higher (which is part of the reason why you can drive more power to a speaker than its rating).

    The problems begin at the low frequencies though. Excursion demands increase the lower you go, and power handling mechanically drops really fast as you approach the frequency of resonance of the driver. For most 5 or 6" woofers I've seen, this happens rougly in the 30-50Hz region. 8" woofers handle power a bit better, and subwoofers better still. When excursion reaches max, you can hear lead slap and your woofer can bottom out. Physical damage at this happens at this point. I should add, this can occur at significantly lower power levels than the speaker's ratings, sometimes just a few watts. This is one reason why it's a good idea to set speakers to "SMALL" (even on floorstanders) if you have a subwoofer connected to your receiver.

    The minimum power rating is to protect tweeters from poor amplifiers. Good SET's and SS's won't feed much distortion, but poor ones will. You get a lot of upper harmonics added to the tweeters load, and the power to the tweeter soars from the normal miliwatt range to full watt figures - during peaks you can easily damage the tweeter. This is bad.

    Clean power, undistorted, not clipped is good and most speakers can handle more than their ratings when fed the good stuff, just don't push it.

  10. #10
    Silence of the spam Site Moderator Geoffcin's Avatar
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    Clipping is bad, more power good!

    Quote Originally Posted by kexodusc
    .

    Clean power, undistorted, not clipped is good and most speakers can handle more than their ratings when fed the good stuff, just don't push it.
    I can't help it but everytime I hear a speaker driven by a more powerful amp it just sounds better. I got to hear a set of maggies just like mine that were bi-amped and the bass was like "WTF"?! Of course they were feeding 800 watts into just the bass panels ( panel is totally not rated for that kind of power) and it just kept sounding better and better the louder we pushed it!

    Vince Bruzzese of Totem told me personally that the Hawks really needed more power to sound thier best, and he was using a 200wpc amp to drive them! (which sounded just right on the Rainmakers) The Mani-2 was being driven by 400wpc (into 4ohms), and it really plumbed the debths like no standmount I ever heard.
    Audio;
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  11. #11
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    Quote Originally Posted by Geoffcin
    I can't help it but everytime I hear a speaker driven by a more powerful amp it just sounds better. I got to hear a set of maggies just like mine that were bi-amped and the bass was like "WTF"?! Of course they were feeding 800 watts into just the bass panels ( panel is totally not rated for that kind of power) and it just kept sounding better and better the louder we pushed it!

    Vince Bruzzese of Totem told me personally that the Hawks really needed more power to sound thier best, and he was using a 200wpc amp to drive them! (which sounded just right on the Rainmakers) The Mani-2 was being driven by 400wpc (into 4ohms), and it really plumbed the debths like no standmount I ever heard.
    This is interesting, electrically, if the burden is not placed on the amp, a 40 watt, 60 watt, 200 watt amp should all deliver the same clean signal, hence no audible difference until you do place that demand on the amp. Even transients aren't terribly burdensome, most 40 watt amps rated RMS can hit 160 watt peaks or more without issue. While I haven't personally never, ever heard bigger amps (specifically within the same product line) sounding better than small amps when played within design limits, I get this comment so often from people whose ears I trust that it I can't descredit it that for some combination it is true. There's also the camp that says smaller amps sound better than larger ones.

    We know capacitance and inducatance characteristics of a speaker can make it more or less agreeable with amps, if I had to guess, I'd say when the component sizes increase inside a larger amp maybe they become more favorable? Could be damping factor etc too?

    I've always just bought the most power I could afford simply because it's cheap. Might not be a bad way to approach it, but surely there must be a point where it just doesn't make a difference.

  12. #12
    Forum Regular Florian's Avatar
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    You can generally say that you wont kill a speaker if you use common sense and dont make the drivers, jump in an out ;-)

    On some exotic speakers like my Apogee Scintilla you have to be VERY carefull with your choice of AMPS. The impedance drops to 0.5 ohms and generally stays at 1ohm. This is a brutal load on any amplifier and therefore restrict you to exotic amps. Within the Krell series you need to stay either in the big FPB or in the KSA series. My new Sphinx equipment will properbly run them too. (will see soon). So the load is very important too !!
    The more power you have the better it will control the speaker, this might not be as-true with bookshelves but once you have a fullrange speaker with many drivers the controll issue beomes a factor too.

    But in general if you have a 8 or 4 ohm speaker you should be fine with any amp and you wont kill them unless you over do it.

    -Flo
    Lots of music but not enough time for it all

  13. #13
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    if you match an amp of 150watts per channel with a speaker rated at 20-120watts won't it have a hard time performing on the lower bass frequencies resulting in woofer jumping??

  14. #14
    Forum Regular Florian's Avatar
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    Not if you crank it up a 100% where the amp and speaker distorts like crazy :-)
    For instance my recent Krell amp pushed 1.7kw (kilowatt) into one panel. This is the theoratical max output, but the problem is the control at that power output. Most amplifiers with ratings of 150wpc max will never reach that without distorting badly.

    You can use a 1000wpc amp like a Krell MRA on a 50wpc max bookshelf speaker too! As long as you dont crank it :-)
    Lots of music but not enough time for it all

  15. #15
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    Quote Originally Posted by ninetynine
    if you match an amp of 150watts per channel with a speaker rated at 20-120watts won't it have a hard time performing on the lower bass frequencies resulting in woofer jumping??
    If the speaker has a hard time on the lower bass frequencies, the amount of power in the amp isn't going to change much. The speaker is the limiting factor, not the amp. It's not related in the fashion you are implying. The speaker might have a hard time performing bass frequencies, but if that's the case, adding more power isn't really a great idea because you'll push the speaker to it's mechanical (excursion - movement) limit. Adding more power would damage the speaker.

    When we worry about not having enough power it's because the amp has used up all it's headroom and is clipping the signal. This limits dynamic range can introduce all kinds of nasties and isn't really desireable.

    I'm not sure how big your room is, or what volumes you play at, but by the time you get to 20 watts average power, things are pretty damn loud on most speakers. You'd have plenty of headroom left on a quality 150 watt amp with next to zero distortion before things start to go bad. I have 150 watt rated speakers powered by some 60 and 80 watt amps .
    I'm betting you don't listen at a volume so loud that a 150 watt amp is going to start clipping.. The maximum power out put of an amplifier is really used for handling instantaneous musical peaks. That RMS figure is misleading, because amplifiers can deliver short instantaneous bursts of power for music at much higher levels than their RMS rating without clipping or distortion.

    The power the amp delivers is related to the volume (gain) you apply. As you turn it up, more power is fed to the speaker. For average listening, at pretty loud volumes, you are only using a few watts on average, sometimes even less than 1 watt (well below the "minimum" rated power of the speakers) You might get peaks as high as 10 to 20 watts. Maybe.

    Ninetynine, the Monitor Audio B4's have a sensitivity of 91 dB. That's really good. That means they'll play 91 dB with only 1 watt of power. At only 10 watts of average power you're playing music at live Orchestra levels, rock concert levels's etc. Pretty darn loud.

    I listen on average between 70 and 85 dB in my room. I have to yell at the person beside me for them to hear.

    That's a great combo you are thinking about, I wouldn't worry about power handling.

  16. #16
    Silence of the spam Site Moderator Geoffcin's Avatar
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    It's funny but a lot of different speaker guys think the same.

    Quote Originally Posted by kexodusc
    While I haven't personally never, ever heard bigger amps (specifically within the same product line) sounding better than small amps when played within design limits, I get this comment so often from people whose ears I trust that it I can't descredit it that for some combination it is true. There's also the camp that says smaller amps sound better than larger ones.

    I've always just bought the most power I could afford simply because it's cheap. Might not be a bad way to approach it, but surely there must be a point where it just doesn't make a difference.
    As you know, DIY'er are not into "blowing smoke up you ass", as DIY guys simply know way to much about how things work to be carried away on flights of fancy, but something about this setup clicked in a big way. I think it's telling how much heavy wattage they are pushing, I don't think you would get the same effect with a 100wpc receiver.

    This is what Dan Wiggins of Adire Audio had to say from a review of the new Exodus Audio LCR kit these guys built.

    "Those who know me know I don't ever do this, but I'm going to break my rule: this is probably the finest sub $10,000 set of speakers I've heard. Seriously. Never strained, never congested, full range output down to below 30 Hz. I'm still stunned.

    Power was our QSC PLX3402 on the L&R speakers (~850WPC), and our Plinius amp bridged into the center (~600W). I think I heard the Plinius clip once, and the main speakers bottom just once or twice, but that was at volumes where we had to shout at each other.

    The best thing - at the end of the movie as the credits roll, the Marine band chorus sings. There's a deep drum "whump" that accompanies them. It just happened - it was just there. It was like listening to a large chorale performing in front of you. That real, that well placed, that dynamic and unrestrained."


    OK, from my own point of view;

    On the movie Drumline, when I have it all hanging out, it's JUST about enough to make you feel that there's a REAL marching band in front of you, and I bring almost 2000 watts to the table. For chamber music you can have your 8 watt SET and that will be fine, but if you want to reproduce something like this, or a full Orchestra with 8 Timpani then you better be using heavy iron.
    Audio;
    Ming Da MC34-AB 75wpc
    PS Audio Classic 250. 500wpc into 4 ohms.
    PS Audio 4.5 preamp,
    Marantz 6170 TT Shure M97e cart.
    Arcam Alpha 9 CD.- 24 bit dCS Ring DAC.
    Magnepan 3.6r speakers Oak/black,

  17. #17
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    Quote Originally Posted by kexodusc
    If the speaker has a hard time on the lower bass frequencies, the amount of power in the amp isn't going to change much. The speaker is the limiting factor, not the amp. It's not related in the fashion you are implying. The speaker might have a hard time performing bass frequencies, but if that's the case, adding more power isn't really a great idea because you'll push the speaker to it's mechanical (excursion - movement) limit. Adding more power would damage the speaker.
    Hmm im not sure I understand this part, are you saying ONLY in the case where the speaker has a hard time with low bass frequencies, adding the 150watt amplifier power to a speaker rated below that 150watt rating it will the damage the speaker?
    my room is quite small thats why I would like to stay with bookshelf speakers I really have my mind set on some B&W DM602 S3 bookshelves ( 90db ) 8 ohms 20-120watt 49hz-20khz. the monitor audio floorstanders might be to big for the room I have.

  18. #18
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    ninetynine:

    Not exactly. I'm saying every speaker has a maximum excursion distance that it reaches at certain frequencies when fed different amounts of power. This generally occurs well above listening levels, but if you plan on feeding a speaker 150 watts it's something to keep in mind.

    Adding more power to most speakers below their capable frequency range will cause the speaker to move more as it tries to output low bass. It typically maxes out it's movement at extremely loud volumes. To produce loud bass of a certain level, the woofer has to move further than it would to produce the same level of midrange output.

    I tried posting a graph of what's going on but the site won't let me and I can't shrink its size.
    I could send you an excel graph showing you the relationship between power, frequency, and woofer excursion (called xmax measured in milimeters) for a typical 6.5" woofer to help you better visualize what's going on. If you're interested, please pm me with an e-mail address.

  19. #19
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    Quote Originally Posted by kexodusc
    ninetynine:

    Not exactly. I'm saying every speaker has a maximum excursion distance that it reaches at certain frequencies when fed different amounts of power. This generally occurs well above listening levels, but if you plan on feeding a speaker 150 watts it's something to keep in mind.

    Adding more power to most speakers below their capable frequency range will cause the speaker to move more as it tries to output low bass. It typically maxes out it's movement at extremely loud volumes. To produce loud bass of a certain level, the woofer has to move further than it would to produce the same level of midrange output.

    I tried posting a graph of what's going on but the site won't let me and I can't shrink its size.
    I could send you an excel graph showing you the relationship between power, frequency, and woofer excursion (called xmax measured in milimeters) for a typical 6.5" woofer to help you better visualize what's going on. If you're interested, please pm me with an e-mail address.
    that'd be great! Isn't this scenario usually the case where you have lets say an amp of 40 watts with a speaker of 60-120watts? This is actually a problem I have with an old vintage receiver where the speaker woofer moves more trying to output low bass like you say. But, are you saying this is also the case with an amplifier exceeding the power ratting of the speaker?

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