[Elecraft] KX1 headphones

[Erik N Basilier]

Brett, I think you are referring to the fact that many audio amplifiers have 
an output impedance which is much lower than the load they are designed for, 
with the result that a lower impedance load receives more power. This is not 
the same as sensitivity, which is measured in sound pressure dB per 
milliwatt. That  said, more power helps create more sound pressure, so in 
practice you should be right in many cases. One person sent me a pm 
recommending Creative (thanks!). They do list sensitivity on their web site:

http://us.creative.com/products/welcomenew.asp?category=437&#subcat861

The Aurvana in-ear at $99 has one of the higher sensitivities I have seen at 
115 dB. The impedance of  42 ohms is rather high, illustrating that high 
sensitivity can come with high impedance, but o.t.o.h. the high impedance 
might counteract the sensitivity so that it is not very loud with a KX1. 
Hmmm... the LM386N in the KX1 is spec'd for an 8 ohm load. The actual output 
impedance is not specified, but I would guess that it is much lower, which 
means that the amplifier is a voltage source. Then with a load of 42 ohms 
instead of 8 ohms, the electrical output power is reduced by about 7 dB. If 
I instead look at the EP-220, which looks similar to my existing Optimus 
earbuds, it is specified at 110 dB sensitivity and 16 ohms.
The impedance of 16 instead of 8 means a loss of electrical output power of 
3 dB. 115-7 = 108 dB for the Aurvana, and 110-3 = 107 dB for the EP-220. 
Thus, *IF* the EP-220 were identical to my Optimus, then I would gain 1 dB 
by getting the Aurvana. However, I can't see paying the $99 for the Aurvana 
unless I could try it for comfort first.

73,
Erik K7TV

----- Original Message ----- 
From: "Brett Howard" <brett at livecomputers.com>
To: "Erik N Basilier" <ebasilier at cox.net>
Cc: "David Woolley (E.L)" <forums at david-woolley.me.uk>; 
<elecraft at mailman.qth.net>
Sent: Thursday, August 20, 2009 10:39 PM
Subject: Re: [Elecraft] KX1 headphones


> If sensitivity isn't specified often impedance is and the lower the
> impedances usually result in higher efficiencies.
>
> ~Brett (KC7OTG)
>
> On Thu, 2009-08-20 at 22:27 -0700, Erik N Basilier wrote:
>> Thanks all for the suggestions!
>> Not having fallen yet for the fashionable pocket music players, I wasn't
>> aware of how much money young people can spend on earbuds, nor that the
>> in-ear style is back into fashion. OK, I have an expensive headset for 
>> phone
>> operation, and I appreciate expensive units for music, but I can't see
>> paying a lot for frequency response when the radio is cw only. When I 
>> looked
>> up all the earbuds etc available from RS, the selection is quite 
>> staggering,
>> but the "spec's" don't say anything about sensitivity; the fine audio 
>> brands
>> mostly don't specify sensitivity either. I think my next step will be to
>> visit the nearby RS where the mgr recognizes me, and then try as many 
>> models
>> as he will let me...
>>
>> 73,
>> Erik K7TV
>>
>> ----- Original Message ----- 
>> From: "David Woolley (E.L)" <forums at david-woolley.me.uk>
>> To: "Erik N Basilier" <ebasilier at cox.net>
>> Cc: <elecraft at mailman.qth.net>
>> Sent: Thursday, August 20, 2009 3:15 PM
>> Subject: Re: [Elecraft] KX1 headphones
>>
>>
>> > 16mm buds are Walkman style and therefore no longer fashionable.  The
>> > current fashion is i-Pod, which do fit in the ear canal and generally 
>> > have
>> > soft foam.  I think most of the recommendations you have had are for 
>> > i-Pod
>> > "in the ear" style.
>> >
>>
>>
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