Monitoring stompbox with HEADPHONE

[rogeryu_ph]

Guys,
Yesterday I bought an headphone here's the the brand and the specs 32ohm, 100db sensivity and 500mw
http://www.p4c.philips.com/files/s/shp2000_00/shp2000_00_pss_aen.pdf

I did monitor the sound against the speaker and without speaker on, why is it the volume is lower when using headphone while not adjusting volume? Is the new headphone is defective....
Strange...an ordinary MP3 earphone is louder.....

I'm not familiar with headphone quality and the specs  can someone shed light and help a brother here.

THANKS
Roger

[any]

what did you plug it in to?

[rogeryu_ph]

Direct to my FENDER FM DSP 65w amp headphone output 

Roger

[sean k]

If I remember rightly when I built a mixer with headphone outs I specifically built it to drive low ohm headphones which tend to be higher quality. Most headphones are up around 2k so they don't have such a high current draw. If you check the specs on yer headphone out on the amp it might be 600 ohms to 5k, something lower that what it's usually driving. So your quality 32ohm  headphones just aren't recieving the push they need to get them pushing the magnets... I think... maybe?

[montezuma]

As a rule of thumb, headphones with lower impedance ("consumer grade") are louder with headphone outputs on most devices. They draw more current than high-impedance ("studio grade" or Hi-Fi) headphones. The latter, in contrast, need more voltage to be driven well. MP3 earbuds normally have only 8 or 16 ohms, they are easy to drive loud, but they are also more prone to distort. So, the impedance is a factor in perceived volume. And, like with any speaker, efficiency is another factor. Two different speaker models with the same impedance can produce different volume levels.
To sum it up, probably your headphones are OK. There is no way for a manufacturer to make a headphone output which gives the same volume level for all headphones.
HTH

[rogeryu_ph]

One thing I forgot to mention beside low volume is my individual stompbox sounds not same with speaker even I add some volume on it    and strange, my MFX sound was almost same with speaker with volume added..... degraded sound on analog when monitored with headphone.
Is this the classic case of digital versus analog?
BTW Montezuma and Sean k thanks for the input.....

Roger