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<blockquote data-quote="hispls" data-source="post: 7475985" data-attributes="member: 614752">The amp may or may not ever even see 1 ohm.&nbsp; Here we see an impedence curve of a woofer (probably 3 ohm DCR coil)<img src="http://www.churchsoundcheck.com/Resources/IMAGE1%202.GIF" alt="" class="fr-fic fr-dii fr-draggable " style="" />All subs are different of course, and it&#039;ll change depending on the box, but the point is, within useable bandwidth you would never see below 5 ohms.&nbsp;&nbsp; Now this is definitely not to say that you can count on running an amp at half rated impedence and be safe, but to illustrate that ONLY taking into account voltage unless you know precisely the impedence at a given test frequency is a very inaccurate method to set gains.&nbsp;&nbsp; As Wen said, higher frequency will generally put you at a lower impedence...your highest impedence is the Fs of the woofer.&nbsp; In fact if they publish z-max spec you can use that as a known impedence and calculate power at that frequency, but really most amps don&#039;t put out gobs of power at 30 or 40 ohms.</blockquote>

[QUOTE="hispls, post: 7475985, member: 614752"] The amp may or may not ever even see 1 ohm. Here we see an impedence curve of a woofer (probably 3 ohm DCR coil) [IMG]http://www.churchsoundcheck.com/Resources/IMAGE1%202.GIF[/IMG] All subs are different of course, and it'll change depending on the box, but the point is, within useable bandwidth you would never see below 5 ohms. Now this is definitely not to say that you can count on running an amp at half rated impedence and be safe, but to illustrate that ONLY taking into account voltage unless you know precisely the impedence at a given test frequency is a very inaccurate method to set gains. As Wen said, higher frequency will generally put you at a lower impedence...your highest impedence is the Fs of the woofer. In fact if they publish z-max spec you can use that as a known impedence and calculate power at that frequency, but really most amps don't put out gobs of power at 30 or 40 ohms. [/QUOTE]

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