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The Basement
Hello, first post, noob question... - Amplifier Power Ratings
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<blockquote data-quote="Carl Klinkenborg" data-source="post: 213904" data-attributes="member: 12770"><p>Hi Steve Smith,</p><p></p><p>In essence you are absolutely correct, however it is important to be aware that quoting a power output without stating conditions is open to outlandish advertising claims. I'm sure you will have come across the terms 'Peak' and 'RMS' in connection with power ratings, and whilst these narrow down Marketing Departments' creativity and abuse somewhat, they can still be misleading. Further, power output generally increases with reducing load impedance until the amplifier shuts down/blows a fuse/goes up in smoke... </p><p>A better specification would read something like: 120Wrms continuous per channel into 4ohms, 20Hz - 20kHz, both channels driven, max. 0.1% THD.</p><p></p><p>Matching amplifier power to speaker rating is a considerably more grey area! Your 120W amplifier could be used <em>with care</em> driving 5W speakers; equally it could be used to power 500W speakers, just not to their full potential. In a nutshell, the speaker power does not have to precisely match the amplifier output. I always use an amplifier of a higher rating than the speakers (400Wrms on an 80W tweeter for example, and 2000W on a 1200W sub) to maintain as much dynamic headroom as possible - not easy as the frequency goes lower! (I like to use the car-on-the-motorway example: Both a 1300cc VW Beetle and a 4.2l turbocharged Porsche can achieve 70mph, but the latter has considerably more power in reserve to overtake). </p><p></p><p>Stated simply, The 120W amp would blow the 5W speaker, but the very same amp might fail if running continuously flat out for hours into a 500W speaker - both extremes could be damaging with no understanding of the setup.</p><p></p><p>Returning briefly to impedance, you are also quite correct in stating: '... a combination of speakers... ...with the correct impedance...'. You could connect 8 x 8ohm speakers to give 4ohms impedance, or 16 x 4ohm to also give 4ohms; the quantity of speakers per se is irrelevant to the impedance which the amplifier sees at its output terminals.</p><p></p><p>Good luck with your project and feel free to ask away - no question is foolish if you do not know the answer! Cheers, Carl.</p></blockquote><p></p>
[QUOTE="Carl Klinkenborg, post: 213904, member: 12770"] Hi Steve Smith, In essence you are absolutely correct, however it is important to be aware that quoting a power output without stating conditions is open to outlandish advertising claims. I'm sure you will have come across the terms 'Peak' and 'RMS' in connection with power ratings, and whilst these narrow down Marketing Departments' creativity and abuse somewhat, they can still be misleading. Further, power output generally increases with reducing load impedance until the amplifier shuts down/blows a fuse/goes up in smoke... A better specification would read something like: 120Wrms continuous per channel into 4ohms, 20Hz - 20kHz, both channels driven, max. 0.1% THD. Matching amplifier power to speaker rating is a considerably more grey area! Your 120W amplifier could be used [I]with care[/I] driving 5W speakers; equally it could be used to power 500W speakers, just not to their full potential. In a nutshell, the speaker power does not have to precisely match the amplifier output. I always use an amplifier of a higher rating than the speakers (400Wrms on an 80W tweeter for example, and 2000W on a 1200W sub) to maintain as much dynamic headroom as possible - not easy as the frequency goes lower! (I like to use the car-on-the-motorway example: Both a 1300cc VW Beetle and a 4.2l turbocharged Porsche can achieve 70mph, but the latter has considerably more power in reserve to overtake). Stated simply, The 120W amp would blow the 5W speaker, but the very same amp might fail if running continuously flat out for hours into a 500W speaker - both extremes could be damaging with no understanding of the setup. Returning briefly to impedance, you are also quite correct in stating: '... a combination of speakers... ...with the correct impedance...'. You could connect 8 x 8ohm speakers to give 4ohms impedance, or 16 x 4ohm to also give 4ohms; the quantity of speakers per se is irrelevant to the impedance which the amplifier sees at its output terminals. Good luck with your project and feel free to ask away - no question is foolish if you do not know the answer! Cheers, Carl. [/QUOTE]
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Hello, first post, noob question... - Amplifier Power Ratings
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