Subject: Re: USB sound cards From: Ilpo Martikainen <ilpo.martikainen@xxxxxxxx> Date: Tue, 16 Dec 2014 06:58:51 +0000 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>--_000_4FDD35C99B14406D9BD1A27BA08E33FFgeneleccom_ Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable It is not lossless, there is the voice coil resistance, which absorbs the e= nergy. It does not matter whether the resistance is internal or external. I= t is true that almost all audio amplifiers are voltage amplifiers with prac= tically zero output impedance, but ironically lot of problems would disappe= ar in loudspeakers, if driven with current amplifiers. The main reason for = using voltage amplifiers is just the electromechanical damping it offers at= the low frequency resonance. The same would be achieved with acoustical re= sistance elements behind the diaphragm - just like in many headphone driver= s - but this is not currently done. Loudspeaker drivers from 30=92s and 40= =92s often have basket openings covered with a mesh serving just this purpo= se. At mid and high frequencies the driving source impedance does not matte= r as the diaphragm does not vibrate as a piston but bending waves are propa= gating along it. What matters there is the diaphragm internal damping, i.e.= mechanical losses. Ilpo On 16 Dec 2014, at 07:30, Richard F. Lyon <dicklyon@xxxxxxxx<mailto:dicklyon= @xxxxxxxx>> wrote: On Sun, Dec 14, 2014 at 6:15 AM, Bob Masta <audio@xxxxxxxx<mailto:audio@xxxxxxxx= daqarta.com>> wrote: However, if instead of disconnection the leads were *shorted* after the pulse, the generator would be driving all its current into the zero-ohm load, giving a maximum damping effect. I'm not buying that. A zero-ohm load is lossless, just like an open circui= t. Damping requires loss. Whether higher or lower resistance makes more d= amping depends on the nature of the resonance. Dick --_000_4FDD35C99B14406D9BD1A27BA08E33FFgeneleccom_ Content-Type: text/html; charset="Windows-1252" Content-ID: <199F92DC62FF104BA19B676469737299@xxxxxxxx> Content-Transfer-Encoding: quoted-printable <html> <head> <meta http-equiv=3D"Content-Type" content=3D"text/html; charset=3DWindows-1= 252"> </head> <body style=3D"word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-lin= e-break: after-white-space;"> It is not lossless, there is the voice coil resistance, which absorbs the e= nergy. It does not matter whether the resistance is internal or external. I= t is true that almost all audio amplifiers are voltage amplifiers with prac= tically zero output impedance, but ironically lot of problems would disappear in loudspeakers, if driven with= current amplifiers. The main reason for using voltage amplifiers is just t= he electromechanical damping it offers at the low frequency resonance. The = same would be achieved with acoustical resistance elements behind the diaphragm - just like in many headphone dri= vers - but this is not currently done. Loudspeaker drivers from 30=92= s and 40=92s often have basket openings covered with a mesh serving just th= is purpose. At mid and high frequencies the driving source impedance does not matter as the diaphragm does not vibrate= as a piston but bending waves are propagating along it. What matters there= is the diaphragm internal damping, i.e. mechanical losses. <div><br> </div> <div>Ilpo<br> <div><br> <div><br> </div> <div><br> <div> <div>On 16 Dec 2014, at 07:30, Richard F. Lyon <<a href=3D"mailto:dickly= on@xxxxxxxx">dicklyon@xxxxxxxx</a>> wrote:</div> <br class=3D"Apple-interchange-newline"> <blockquote type=3D"cite"> <div dir=3D"ltr">On Sun, Dec 14, 2014 at 6:15 AM, Bob Masta <span dir=3D"lt= r"><<a href=3D"mailto:audio@xxxxxxxx" target=3D"_blank">audio@xxxxxxxx= .com</a>></span> wrote:<br> <div class=3D"gmail_extra"> <div class=3D"gmail_quote"> <blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p= x #ccc solid;padding-left:1ex"> However, if instead of disconnection the leads were<br> *shorted* after the pulse, the generator would be driving<br> all its current into the zero-ohm load, giving a maximum<br> damping effect.<br> </blockquote> <div><br> </div> <div>I'm not buying that. A zero-ohm load is lossless, just like an o= pen circuit. Damping requires loss. Whether higher or lower res= istance makes more damping depends on the nature of the resonance.<br> <br> </div> <div>Dick<br> <br> </div> </div> </div> </div> </blockquote> </div> <br> </div> </div> </div> </body> </html> --_000_4FDD35C99B14406D9BD1A27BA08E33FFgeneleccom_--