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Car Audio Equipment
Subwoofers
help with rms vs peak watts
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<blockquote data-quote="zako" data-source="post: 7448670" data-attributes="member: 629735"><p>There is ABSOLUTELY no reason to match subwoofers RMS wattage with amplifier power exactly. Sometimes, you can run a 600watt RMS subwoofer off a 250watt amplifier with no problems. In other cases, you should have those 600watts available in full.</p><p></p><p>One good rule of thumb is to give your subwoofer just enough RMS wattage so that at this wattage in the given box configuration, the subwoofer reaches its xmax limit at say 30Hz. If this wattage is higher than subwoofer's own RMS rating, then take the lower number. The logic behind this is that there is no point to provide more continuous power than what's allowed by essentially mechanical xmax limit. Of course, the cone usually can excurt way beyond its xmax, but in that region it's non-linear, and we basically don't know what's going to happen, specially in SQ area. One way to answer this question is to download the latest WinISD alpha. Load into it the T/S parameters of the woofer, switch to excursion plot, and keep adding wattage until the excursion exceeds drives xmax limit at say 30Hz.</p><p></p><p>You can ignore this rule of thumb if you can also predict from the modeling software that you can reach the necessary SPL with a much lower RMS wattage than what's necessary to reach a subwoofer's xmax limit. Example: I know very well that my 300wrms RE Audio SRX12 subwoofer will play louder than necessary in my car while running off my 250wrms amplifier. So I can use this subwoofer as a yardstick in the modeling software. To reach 103dB SPL at 50Hz, this sub needs 90watts according to WinISD. Loading into WinISD (in their respective sealed box configurarions) subwoofers RE Audio SE/X12, Infinity Kappa12 120.9w (2ohm), and Image Dynamics IDQ12 (dual 4 ohm), shows that each one of these subwoofers will reach exactly the same SPL with 90watts or less power. Based on this analysis, I can conclude that I can run all of these three subwoofers off a 250watt rms amplifier, even though they're rated for 600watt, 350watts, and 700watts RMS respectively. To make a second illustration, I load into WinISD Dayton Reference HO12 (DVC) and Alpine Type-X12. To reach the SPL of 103dB at 50Hz, both of these need over 200watts. Based on this analysis (ignoring xmax for the monent), it is clear to me that to run these subwoofers I probably need at least 250watts time 3 = approximately 700-800watt amplifier.</p></blockquote><p></p>
[QUOTE="zako, post: 7448670, member: 629735"] There is ABSOLUTELY no reason to match subwoofers RMS wattage with amplifier power exactly. Sometimes, you can run a 600watt RMS subwoofer off a 250watt amplifier with no problems. In other cases, you should have those 600watts available in full. One good rule of thumb is to give your subwoofer just enough RMS wattage so that at this wattage in the given box configuration, the subwoofer reaches its xmax limit at say 30Hz. If this wattage is higher than subwoofer's own RMS rating, then take the lower number. The logic behind this is that there is no point to provide more continuous power than what's allowed by essentially mechanical xmax limit. Of course, the cone usually can excurt way beyond its xmax, but in that region it's non-linear, and we basically don't know what's going to happen, specially in SQ area. One way to answer this question is to download the latest WinISD alpha. Load into it the T/S parameters of the woofer, switch to excursion plot, and keep adding wattage until the excursion exceeds drives xmax limit at say 30Hz. You can ignore this rule of thumb if you can also predict from the modeling software that you can reach the necessary SPL with a much lower RMS wattage than what's necessary to reach a subwoofer's xmax limit. Example: I know very well that my 300wrms RE Audio SRX12 subwoofer will play louder than necessary in my car while running off my 250wrms amplifier. So I can use this subwoofer as a yardstick in the modeling software. To reach 103dB SPL at 50Hz, this sub needs 90watts according to WinISD. Loading into WinISD (in their respective sealed box configurarions) subwoofers RE Audio SE/X12, Infinity Kappa12 120.9w (2ohm), and Image Dynamics IDQ12 (dual 4 ohm), shows that each one of these subwoofers will reach exactly the same SPL with 90watts or less power. Based on this analysis, I can conclude that I can run all of these three subwoofers off a 250watt rms amplifier, even though they're rated for 600watt, 350watts, and 700watts RMS respectively. To make a second illustration, I load into WinISD Dayton Reference HO12 (DVC) and Alpine Type-X12. To reach the SPL of 103dB at 50Hz, both of these need over 200watts. Based on this analysis (ignoring xmax for the monent), it is clear to me that to run these subwoofers I probably need at least 250watts time 3 = approximately 700-800watt amplifier. [/QUOTE]
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help with rms vs peak watts
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