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<blockquote data-quote="thylantyr" data-source="post: 1250830" data-attributes="member: 560358"><p>In car audio, you did this;</p><p></p><p>Amplifier -&gt; 4 Ohm sub in parallel with another 4 Ohm sub = 2 Ohm load.</p><p></p><p>-- no passive crossover.</p><p></p><p>If you did this;</p><p></p><p>Amplifier -&gt; passive crossover -&gt; 4 Ohm sub in parallel with another 4 Ohm</p><p></p><p>sub = 2 Ohm load.</p><p></p><p>Both woofers are connected together in parallel.</p><p></p><p>You arn't doing this with tweeters. You are not paralleling tweeters with</p><p></p><p>midranges and woofers.</p><p></p><p>The amplifier is driving three seperate crossover sections that in turn drives</p><p></p><p>each speaker {tweeter, midrange, woofer}.</p><p></p><p>You have to remember that this is impedance, impedance changes with</p><p></p><p>frequency. Each driver can have a different impedance depending on</p><p></p><p>what frequency is playing. Effectively, you can assume the impedance to</p><p></p><p>be 8 Ohm when you make a loudspeaker with passive crossovers if the</p><p></p><p>tweeter, midrange and woofer is 8 Ohm nominal, but this 8 Ohm 'total'</p><p></p><p>impedance isn't written in stone either, it changes.</p><p></p><p>Even when you paralleled those two 4 Ohm woofers for 2 Ohm, that 2 Ohm</p><p></p><p>rating is still nominal, it will change also, could be higher or lower but can't</p><p></p><p>drop below the DC coil resistance of the woofer. So, if your 4 Ohm woofer is</p><p></p><p>3.2 ohms DC coil, two in parallel would be 1.6 Ohm load worse case when</p><p></p><p>you think it's really 2 Ohms. /hehe Could be higher, the box affects impedance</p><p></p><p>too. What if it's really 2.8 Ohm playing some frequency? You thought it's suppose</p><p></p><p>to be 2 Ohm.. /hehe</p><p></p><p>Suppose you made a 3 way loudspeaker using 16 Ohm tweeters, 8 Ohm</p><p></p><p>midranges and 1 Ohm woofers using a passive crossover. The amplifier will</p><p></p><p>get punished by that 1 Ohm woofer because impedance is very low. The other</p><p></p><p>drivers won't drain the amp by comparison.</p><p></p><p>What if you use a 1 Ohm tweeter, 8 Ohm midrange, and 16 Ohm woofer in a design? The amplifier wouldn't freak out as much as the 1 Ohm tweeter won't</p><p></p><p>consume alot of power like a 1 Ohm woofer can. Also, that 1 Ohm may not</p><p></p><p>be 1 Ohm as it is also dependent upon which frequency plays.</p><p></p><p>When you build loudspeakers you can use lower impedance tweeters as long</p><p></p><p>as you have a 'dumb' amplifier. Even lower impedance midranges are ok as it</p><p></p><p>won't thrash the amplifier. Woofers are hogs, you really punish an amplifier.</p><p></p><p>A dumb amplifier would be one with no protection circuit that may detect</p><p></p><p>a low impedance and turn off to protect itself... Even though the tweeter</p><p></p><p>won't cause the amp to overheat, the amplifier may not cooperate with you.</p><p></p><p>I prefer amps with no impedance detection circuits. Heat sensor is fine, if it gets</p><p></p><p>hot then turn off. //content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif</p></blockquote><p></p>
[QUOTE="thylantyr, post: 1250830, member: 560358"] In car audio, you did this; Amplifier -> 4 Ohm sub in parallel with another 4 Ohm sub = 2 Ohm load. -- no passive crossover. If you did this; Amplifier -> passive crossover -> 4 Ohm sub in parallel with another 4 Ohm sub = 2 Ohm load. Both woofers are connected together in parallel. You arn't doing this with tweeters. You are not paralleling tweeters with midranges and woofers. The amplifier is driving three seperate crossover sections that in turn drives each speaker {tweeter, midrange, woofer}. You have to remember that this is impedance, impedance changes with frequency. Each driver can have a different impedance depending on what frequency is playing. Effectively, you can assume the impedance to be 8 Ohm when you make a loudspeaker with passive crossovers if the tweeter, midrange and woofer is 8 Ohm nominal, but this 8 Ohm 'total' impedance isn't written in stone either, it changes. Even when you paralleled those two 4 Ohm woofers for 2 Ohm, that 2 Ohm rating is still nominal, it will change also, could be higher or lower but can't drop below the DC coil resistance of the woofer. So, if your 4 Ohm woofer is 3.2 ohms DC coil, two in parallel would be 1.6 Ohm load worse case when you think it's really 2 Ohms. /hehe Could be higher, the box affects impedance too. What if it's really 2.8 Ohm playing some frequency? You thought it's suppose to be 2 Ohm.. /hehe Suppose you made a 3 way loudspeaker using 16 Ohm tweeters, 8 Ohm midranges and 1 Ohm woofers using a passive crossover. The amplifier will get punished by that 1 Ohm woofer because impedance is very low. The other drivers won't drain the amp by comparison. What if you use a 1 Ohm tweeter, 8 Ohm midrange, and 16 Ohm woofer in a design? The amplifier wouldn't freak out as much as the 1 Ohm tweeter won't consume alot of power like a 1 Ohm woofer can. Also, that 1 Ohm may not be 1 Ohm as it is also dependent upon which frequency plays. When you build loudspeakers you can use lower impedance tweeters as long as you have a 'dumb' amplifier. Even lower impedance midranges are ok as it won't thrash the amplifier. Woofers are hogs, you really punish an amplifier. A dumb amplifier would be one with no protection circuit that may detect a low impedance and turn off to protect itself... Even though the tweeter won't cause the amp to overheat, the amplifier may not cooperate with you. I prefer amps with no impedance detection circuits. Heat sensor is fine, if it gets hot then turn off. [IMG]//content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif[/IMG] [/QUOTE]
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