[KR...]

I just had this info, I have had the need the share :

HP-1000 = 40ohms at 94db sensitivity.

RS-1 = 32ohms at 98db sensitivity.

Now can anyone explain which these numbers mean?

 

[joelongwood]

I think they mean that the HP-1000s require more power than the RS-1s to acheive the same loudness level, measured in decibels. Based on those numbers, the RS-1s would be considered the more efficient headphone........more efficient at translating electrical energy into acoustic energy. Speaker sensitivity is usually stated as something like 98db/1 watt/ 1 meter, meaning that with 1 watt of power applied to the speaker terminals, the speaker will output sound measured at 98 decibels, measured 1 meter in front of the speaker. I don't know how much electrical energy is applied to the headphone....I'm guessing 1mw? I believe the Sony CD3000s are more efficent still. They measure 32 ohms at, I believe, 104 db.......very efficient!

 

[sackley]

HP-1000's, oh how I love thee, let me count the ways. Someday one of you will be mine, oh yes, you shall be mine.

 

[ophir]

The impedance/efficiency numbers show how easily the headphone/speaker can be driven, i.e. how loud (in dBs) a certain amount of mW will get (headphones, I believe, are stated in dB/mW and speakers in dB/W). Anyway, a sample calculation may make it easier:

Say a pair of phones has an imp. of 32ohms, and is 98dB/mW efficient, and I have an amp (like that on my Aiwa HX70 MDP) that can output 8mW into 16ohms. The math goes like this

P=(V^2)/R and since voltage is constant,
P1*R1 = P2*R2 => 8mW*16ohms=P2*32ohms; P2=4mW

How it goes is stated in this fashion (broken down for simplicity):

Loudness= efficiency rating + 10*log ( amount of mW the amp can output to the driver, or P2)

mathematically: loudness = 98dB + 10*log (4mW) = 104.02dB at full power, whereas the 40ohm, 94dB phones would only go to 99.05dB at full power.

One more thing, Grado's, to my knowledge are measured in dB/mV not dB/mW. So one would have to find out what the power rating was in mV through P=(V^2)/R ...

PS - if any of my calculations are wrong, please excuse me, it's been 2 years since my last EE class and I'm a little rusty (the fact that I slept through it doesn't help either)

 

[eeyssjr]

Were the HP-1s the RS-1 equivalent in thier day? Wehre do they fit into things?

 

[DanG]

Yes, the HP-1 was the top-of-the-line Grado headphone when Joe Grado, John Grado's uncle, was still owner of Grado. They were discontinued in the early 90s and replaced by the RS-1.