small_lump_of_green_putty Posted June 26, 2009 Share Posted June 26, 2009 [quote name='escholl' post='524602' date='Jun 26 2009, 08:25 AM']i believe they use various forms of feedback to help increase the linearity of the cone movement -- basically giving the amp more control over the driver.[/quote] wasn't billy sheenan using them at one point? Quote Link to comment Share on other sites More sharing options...
escholl Posted June 26, 2009 Share Posted June 26, 2009 [quote name='small_lump_of_green_putty' post='524623' date='Jun 26 2009, 09:40 AM']wasn't billy sheenan using them at one point?[/quote] haha i have no idea ^_^ Quote Link to comment Share on other sites More sharing options...
alexclaber Posted June 26, 2009 Share Posted June 26, 2009 I thought servo drive subs were beltdrive, using a rotary electric motor to push and pull the cone back and forth, hence no ability above ~100Hz. Googled: [url="http://www.ultimateavmag.com/features/704way/index3.html"]http://www.ultimateavmag.com/features/704way/index3.html[/url] Alex Quote Link to comment Share on other sites More sharing options...
escholl Posted June 26, 2009 Share Posted June 26, 2009 (edited) [quote name='alexclaber' post='524658' date='Jun 26 2009, 10:09 AM']I thought servo drive subs were beltdrive, using a rotary electric motor to push and pull the cone back and forth, hence no ability above ~100Hz. Googled: [url="http://www.ultimateavmag.com/features/704way/index3.html"]http://www.ultimateavmag.com/features/704way/index3.html[/url] Alex[/quote] that is one type of mechanical servo drive, however there are electronic versions as well, which tend to be better and much much more common. some use electronic feedback, while others, such as the [url="http://www.meyersound.com/products/studioseries/x-10/"]Meyer X-10[/url] you mentioned the other week, use other forms such as acoustic (pressure) feedback (hence the microphone on the bar in front of the LF driver). edit: all this talk of mechanical servos has reminded me of the [url="http://www.rotarywoofer.com/"]Rotary Woofer[/url]. Edited June 26, 2009 by escholl Quote Link to comment Share on other sites More sharing options...
small_lump_of_green_putty Posted June 26, 2009 Share Posted June 26, 2009 Just found this too, which makes for interesting reading : [url="http://www.diyaudio.com/forums/showthread/t-140741.html"]http://www.diyaudio.com/forums/showthread/t-140741.html[/url] I can't visualise how the motors transfer the rotary motion into linear motion though. Quote Link to comment Share on other sites More sharing options...
escholl Posted June 26, 2009 Share Posted June 26, 2009 (edited) [quote name='small_lump_of_green_putty' post='524686' date='Jun 26 2009, 10:36 AM']Just found this too, which makes for interesting reading : [url="http://www.diyaudio.com/forums/showthread/t-140741.html"]http://www.diyaudio.com/forums/showthread/t-140741.html[/url] I can't visualise how the motors transfer the rotary motion into linear motion though.[/quote] there used to be a really good image on the internet somewhere that showed it clearly. can't find it though basically, the servo motor controls a shaft in the middle of two speakers -- these speaker cones are attached to two belts which wrap around the central shaft powered by the motor. when the motor turns, the speakers move in and out in unison; that is to say they both move in or out at the same time, not one in and one out. edit: [url="http://www.rythmikaudio.com/index.html"]this site[/url] gives an idea of how the electronic ones work. Edited June 26, 2009 by escholl Quote Link to comment Share on other sites More sharing options...
alexclaber Posted June 26, 2009 Share Posted June 26, 2009 I've always thought of those cabs that use pressure sensors, laser interferometry or microphones as part of a feedback system as servo controlled as opposed to servo drive. Rotary motion to linear motion is easy - just like the reverse of a car engine or bicycle cranks - the problem is getting dealing with higher frequencies as even an F1 engine can't exceed ~300Hz. Alex Quote Link to comment Share on other sites More sharing options...
escholl Posted June 26, 2009 Share Posted June 26, 2009 [quote name='alexclaber' post='524755' date='Jun 26 2009, 12:02 PM']I've always thought of those cabs that use pressure sensors, laser interferometry or microphones as part of a feedback system as servo controlled as opposed to servo drive. Rotary motion to linear motion is easy - just like the reverse of a car engine or bicycle cranks - the problem is getting dealing with higher frequencies as even an F1 engine can't exceed ~300Hz. Alex[/quote] sorry, i suppose i didn't make much of a distinction between controlled and drive haha. good thing the rotary woofer has a low-pass filter with a cut off at 20 Hz then not very practical though, really, as you need to build the house around it. Quote Link to comment Share on other sites More sharing options...
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