I'm considering buying the headphones at this link: http://www.musiciansfriend.com/product/Sennheiser-HD201-Pro-Closed-Back-Headphones?sku=242417 to use with i-doser. Are these headphones in the right frequency range? If not, what are another pair of cheap headphones that will work with i-doser that...

I'm not sure. Maybe something like alcohol or marijuana?