Subject: Re: USB sound cards From: James Johnston <audioskeptic@xxxxxxxx> Date: Wed, 17 Dec 2014 00:03:45 -0800 List-Archive:<http://lists.mcgill.ca/scripts/wa.exe?LIST=AUDITORY>--047d7b11198d3495f3050a64eac9 Content-Type: text/plain; charset=UTF-8 It's a bit more complex than that. The response is damped by the speaker motor working against the 2nd order loudspeaker (not 1st, 2nd) impedance. The speaker impedance's resistive parts is in series with the source impedance AND the crossover inductor resistance. This total sets the Qts of the speaker. The box design is a very critical function of Qts for any good design (those of you using sealed enclosures can argue with me in another thread) and must combine with the box's acoustic impedance to provide a good low frequency response that does not either just be missing OR alternatively peak terribly. Vented boxes and passive radiator boxes are especially sensitive to this problem. Source impedance does matter. It also can matter in headphones, and most expect a voltage driven system. jj On Tue, Dec 16, 2014 at 9:28 AM, Richard F. Lyon <dicklyon@xxxxxxxx> wrote: > > I understand that at the low end of the frequency range, the resonance you > guys are talking about is inductive and is damped best by a lower source > impedance. But at higher frequencies, esp if there are crossovers and > such, there may be other resonances, and impedances that look more > capacitive in the relevant region. Source impedance will affect these in > different ways, and with higher-order systems the damping factor is perhaps > too simple a concept. Nevertheless, my point remains that the source > impedance will affect the spectrum of the sound, in possibly complicated > ways, and the traditional use of low driving impedance only optimizes one > aspect of that, which may not correlate with the benefit that some say they > get with added resistance. > > It's worth looking at more closely. > > Dick > > -- James D. (jj) Johnston Independent Audio and Electroacoustics Consultant --047d7b11198d3495f3050a64eac9 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable <div dir=3D"ltr"><div><div><div>It's a bit more complex than that. The = response is damped by the speaker motor working against the=C2=A0 2nd order= loudspeaker (not 1st, 2nd) impedance.<br><br></div>The speaker impedance&#= 39;s resistive parts is in series with the source impedance AND the crossov= er inductor resistance.=C2=A0 This total sets the Qts of the speaker. The b= ox design is a very critical function of Qts for any good design (those of = you using sealed enclosures can argue with me in another thread) and must c= ombine with the box's acoustic impedance to provide a good low frequenc= y response that does not either just be missing OR alternatively peak terri= bly.=C2=A0 Vented boxes and passive radiator boxes are especially sensitive= to this problem.<br><br></div>Source impedance does matter. It also can ma= tter in headphones, and most expect a voltage driven system.<br><br></div>j= j<br></div><div class=3D"gmail_extra"><br><div class=3D"gmail_quote">On Tue= , Dec 16, 2014 at 9:28 AM, Richard F. Lyon <span dir=3D"ltr"><<a href=3D= "mailto:dicklyon@xxxxxxxx" target=3D"_blank">dicklyon@xxxxxxxx</a>></span>= wrote:<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-= left:1px #ccc solid;padding-left:1ex"><div dir=3D"ltr"><div>I understand th= at at the low end of the frequency range, the resonance you guys are talkin= g about is inductive and is damped best by a lower source impedance.=C2=A0 = But at higher frequencies, esp if there are crossovers and such, there may = be other resonances, and impedances that look more capacitive in the releva= nt region.=C2=A0 Source impedance will affect these in different ways, and = with higher-order systems the damping factor is perhaps too simple a concep= t.=C2=A0 Nevertheless, my point remains that the source impedance will affe= ct the spectrum of the sound, in possibly complicated ways, and the traditi= onal use of low driving impedance only optimizes one aspect of that, which = may not correlate with the benefit that some say they get with added resist= ance.<br><br></div><div>It's worth looking at more closely.<br><br>Dick= <br><br></div></div> </blockquote></div><br clear=3D"all"><br>-- <br><div class=3D"gmail_signatu= re"><div>James D. (jj) Johnston</div><div>Independent Audio and Electroacou= stics Consultant</div></div> </div> --047d7b11198d3495f3050a64eac9--