Audio Systems: Headphones ..., ohm max, noise cancelling headphones

Question
Hi Kevin.
I'm shopping for a pair of full-size over-the-head stereo headphones and have several questions.
I did buy a pair this past Sunday for which I have a 30 day trial period.  Here are the specifications

Phillips Model hn101: noise cancelling headphones
frequency 20 - 20,000 hz
active noise attenuation 100 - 1,000 hz > 10dB at 300hz
sensitivity 102dB
impedence 27 ohm
max power input 500mW

What exactly does each specification mean and are you in agreement with me that they are not satisfactory for my needs as I'll outline below.

I have slight hearing difficulty.  I listen, primarily in my very quiet home, to all kinds of music.  However, I particularly want to be able to hear softer passages in Classical music clearly.  If at all posible, I'm looking to spend under $100.  I spent $65 for the ones I have: is that high?  And does noise cancellation forfeit volume?
In recommending some models, can you think of any wireless ones which would meet my needs?
I look forward to hearing from you.  Thank you for your interest.-Ken

Answer
Dear Ken,

Noise cancelling headphones have special circuitry which cancels out ambient noise, that is, noise originating outside the sound source feeding the 'phones. If you have a hearing difficulty and you primarily listen in a quiet room, you probably don't need them. They have the added feature of interfering with the integrity of the sound you want to hear. In a sense, they affect volume.

The specs are pretty common.

Frequency response is the range of music they're capable of reproducing. 20Hz is very low. 20,000Hz is very high--out of the range of human hearing actually.

The noise attenuation just tells you how much ambient noise they cancel out.

Sensitivity is their efficiency for working with low powered amplification. 102dB is outstanding.

Impedance is the load represented to the output amplifier. This is insignificant because all headphone amplifiers (built in to your receiver generally) are engineered to deal with very low impedances. 27 is very, very low. 2 is very high. As you'll note, the relationship between the number and the high/low is inverse.

Maximum power: if they'll handle 500 watts, they'll handle anything. Most receivers put out less than 25 watts when playing music a nominal listening levels. 500 watts is extraordinarily powerful.

My recommendations for headphones are the Grado SR-60 and (better) the Grado SR-80, $69 and $95 respectively at www.audioadvisor.com. I use the SR-60s, and they're fabulous. I've listened to the SR-80s, and they're even better.

I do not recommend wireless 'phones. The technology is still in its infancy, and the sound is not that good.

Good luck. And thanks for choosing allexperts.com!

Kindest regards,

Kevin