> This is not always the case. The headphones that I'm > planning on using are Etymotic ER-4P's which are designed > with a low impedance to remain efficient with portable music > players but have very flat responses.
Unfortunately, the 10 uF coupling capacitors in the output of the K3 headphone amplifier form a voltage divider with the impedance of the headphones (plus the 8.2 Ohm resistors Lyle references). For 8 Ohm headphones the -6dB point in the response is 1 KHz (Xc=16 Ohms). With 200 Ohm phones the -6dB drops to about 75 Hz (Xc=208 Ohms) and with 600 Ohm phones the -6dB point drops to about 25 Hz (Xc=608 Ohms). This is purely a function of the series RC output of the headphone amplifier and does not effect the speaker response. K9AC has recommended replacing the 10 uF caps with 220 uF caps which would reduce the corner frequency for low impedance headsets to about 50 Hz but since my primary headset is the Proset I have not tried it as yet. 73, ... Joe, W4TV > -----Original Message----- > From: Brett Howard [mailto:br...@livecomputers.com] > Sent: Monday, June 22, 2009 1:52 PM > To: li...@subich.com; 'Roy Morris' > Cc: elecraft@mailman.qth.net > Subject: RE: [Elecraft] K3 headphones > > > This is not always the case. The headphones that I'm > planning on using are Etymotic ER-4P's which are designed > with a low impedance to remain efficient with portable music > players but have very flat responses. > > The dip in the top end is intentional as they are sealed into > your ear and they need to put that in so that you don't feel > like there is way too much in the high end. There is much > less rolloff when something is sealed into your ear canal vs outside. > > I've made some plots of the ER4s along side the Grado SR60. > The Grado is an often known standard for relatively > inexpensive cans with good sound. The Grado's run around 60 > to 80 bucks where as the ER4's are around 300 MSRP. But you > can get them for at least half that. > > Response curve: > http://graphs.headphone.com/graphCompare.php?graphType=0&graph > ID[]=733&graphID[]=393 > Impedance curve: > http://graphs.headphone.com/graphCompare.php?graphType=7&graph > ID[]=733&graphID[]=393 > > ~Brett > > > -----Original Message----- > From: Joe Subich, W4TV [mailto:li...@subich.com] > Sent: Monday, June 22, 2009 9:36 AM > To: 'Brett Howard'; 'Roy Morris' > Cc: elecraft@mailman.qth.net > Subject: RE: [Elecraft] K3 headphones > > > Low impedance headsets are the ones with decreased low end > response - or apparent excessive high frequency response and > the resulting "tiring" sound. > > I strongly recommend 200 Ohm (Heil ProSet) or 600 Ohm > (professional) headsets. > > 73, > > ... Joe, W4TV > > > > > > -----Original Message----- > > From: elecraft-boun...@mailman.qth.net > > [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Brett Howard > > Sent: Monday, June 22, 2009 11:47 AM > > To: Roy Morris > > Cc: elecraft@mailman.qth.net > > Subject: Re: [Elecraft] K3 headphones > > > > > > Was it high or low impedance that was causing issues? I'm > > contemplating plugging in two pairs of headphones which is > > probably going to put me somewhere around 11 to 15 ohms > > nominal. I'm sure it'll do fine but hadn't been able to find > > much in the way of specs for the K3 in this regard. > > > > > > On Mon, 2009-06-22 at 11:30 -0400, Roy Morris wrote: > > > Gary, > > > I use a 33 ohm headset with my K3. I have not noticed any > > reduction of audio and the impedence match seems to be good. > > I use an AKG K240 Studio headset and get excellent > > reproduction. Roy Morris W4WFB > > > ______________________________________________________________ > > > Elecraft mailing list > > > Home: http://mailman.qth.net/mailman/listinfo/elecraft > > > Help: http://mailman.qth.net/mmfaq.htm > > > Post: mailto:Elecraft@mailman.qth.net > > > > > > This list hosted by: http://www.qsl.net > > > Please help support this email list: > http://www.qsl.net/donate.html > > > > ______________________________________________________________ > > Elecraft mailing list > > Home: http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/mmfaq.htm > > Post: mailto:Elecraft@mailman.qth.net > > > > This list hosted by: http://www.qsl.net > > Please help support this email list: http://www.qsl.net/donate.html > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
