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Damping Factor - Actual listening tests?
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<blockquote data-quote="John Roberts" data-source="post: 145763" data-attributes="member: 126"><p>Re: Damping Factor - Actual listening tests?</p><p></p><p><span style="font-size: 10px"></span></p><p><span style="font-size: 10px">I'm not that young and I have never used a tube Pa amp. </span></p><p><span style="font-size: 10px"></span><span style="font-size: 12px"><span style="font-size: 10px"></span></span></p><p><span style="font-size: 12px"><span style="font-size: 10px">How could a speaker accelerate faster than it should? Do you perhaps mean something like when the driving signal changes direction, and want's the speaker cone motion to stop or change direction ? </span></span></p><p><span style="font-size: 12px"><span style="font-size: 10px"></span></span></p><p><span style="font-size: 12px"><span style="font-size: 10px">There was a good thread years ago on another forum related to the classic myth about speakers over-herating while standing still during square waves (they don't stand still from square waves and I'm sorry I repeated that). A speaker geek (much smarter than me) posted the equations controlling speaker cone motion, the short version is the voice coil voltage imparts a force in and out. Cone position is the the result of that force working on that mass, and associated spring compliances like speaker surround, air in the box, moon's tidal forces (kidding about that last one.) </span></span></p><p><span style="font-size: 12px"><span style="font-size: 10px"></span></span></p><p><span style="font-size: 12px"><span style="font-size: 10px">Maybe they didn't make it to your continent or it was before your time if you are a young pup, But Tom made a belt driven servo controlled LF cabinet where the speaker cone was literally driven from a low mechanical impedance. (ServoDrive Bass tech 7 or something like that). </span></span></p><p><span style="font-size: 12px"><span style="font-size: 10px"></span></span></p><p><span style="font-size: 12px"></span></p><p><span style="font-size: 12px">As I mentioned Sondermeyer made an amplifier that "could" deliver negative source impedance, way back last century. Patent may be expired by now. As I mentioned there might be some merit for use inside a powered speaker if you know all the driver and box particulars. </span></p><p> <span style="font-size: 12px"></span></p><p>Maybe you didn't see Jason's question?</p><p></p><p>OK here's another hypothetical null test. Take two identical subs, place them side by side and drive them with opposite polarity. Perhaps first listen with short wires feeding both, to see how good of a bass frequency null you can get. Then add your couple hundred feet of wire in series with one sub. Tweak the gains to compensate for level loss and see how close to the short wires null you can get. Any dynamic artifacts you hear that you can't EQ out, will be your damping factor phenomenon. While I don't expect you to find much, or anything that nasty.</p><p></p><p>JR</p></blockquote><p></p>
[QUOTE="John Roberts, post: 145763, member: 126"] Re: Damping Factor - Actual listening tests? [SIZE=2] I'm not that young and I have never used a tube Pa amp. [/SIZE][SIZE=3][SIZE=2] How could a speaker accelerate faster than it should? Do you perhaps mean something like when the driving signal changes direction, and want's the speaker cone motion to stop or change direction ? There was a good thread years ago on another forum related to the classic myth about speakers over-herating while standing still during square waves (they don't stand still from square waves and I'm sorry I repeated that). A speaker geek (much smarter than me) posted the equations controlling speaker cone motion, the short version is the voice coil voltage imparts a force in and out. Cone position is the the result of that force working on that mass, and associated spring compliances like speaker surround, air in the box, moon's tidal forces (kidding about that last one.) Maybe they didn't make it to your continent or it was before your time if you are a young pup, But Tom made a belt driven servo controlled LF cabinet where the speaker cone was literally driven from a low mechanical impedance. (ServoDrive Bass tech 7 or something like that). [/SIZE] As I mentioned Sondermeyer made an amplifier that "could" deliver negative source impedance, way back last century. Patent may be expired by now. As I mentioned there might be some merit for use inside a powered speaker if you know all the driver and box particulars. [/SIZE] Maybe you didn't see Jason's question? OK here's another hypothetical null test. Take two identical subs, place them side by side and drive them with opposite polarity. Perhaps first listen with short wires feeding both, to see how good of a bass frequency null you can get. Then add your couple hundred feet of wire in series with one sub. Tweak the gains to compensate for level loss and see how close to the short wires null you can get. Any dynamic artifacts you hear that you can't EQ out, will be your damping factor phenomenon. While I don't expect you to find much, or anything that nasty. JR [/QUOTE]
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