i just recently reviewed these earphones the new site i write for, about.com's home recording site (due to launch next week).
basically? absolute best bass of any universal fit earphone i've ever tried. the soundstage is natural and without exageration.
here's more pasted from my review:
Pros
* Incredible, natural bass response.
* Many fit options available, including custom molds.
* Highly affordable price.
Cons
* Cable length.
* Cable microphonics.
Description
* Transducer: 10mm, Future Sonics MG5 Proprietary Miniature Dynamic Driver
* Input Sensitivity: +/-112dB @ 30Hz/1mW
* Frequency Response: 20 Hz to 20 Khz
* Accessories Included: Various fit sleeves, earwax cleaner, carrying case.
* Robust audio quality, legendary Future Sonics bass response.
Guide Review - Future Sonics' XtremeMac FS1 In-Ear Earphones
Future Sonics are well-known in the professional audio circuit; their products have been used by some legendary artists; The Grateful Dead and U2 just to name a few. They pride themselves on producing high-quality products using a proprietary speaker design that utilizes dynamic technology, whereas most in-ear monitor manufacturers use balanced armature drivers, the same type of speakers used in hearing aids. Because of this, Future Sonics' products are touted at reproducing bass extremely well, down to 20Hz, even at low volume.
I received the Future Sonics FS1 earphones from Xtrememac and was immediately blown away. These products are extremely useful for not only iPod/casual listeners, but artists on stage looking to monitor in-ear on a budget with extremely rich audio delivery (the bass does in fact extend down to 20hz, very accurately, and with little volume push from my iPod). I can listen for hours with the volume relatively low, and still get very robust audio reproduction.
The only drawbacks? The cable is a little short for stage use, especially if you're a tall guy like me. But when you're looking for extremely high quality audio reproduction (I still can't get over the bass response of these earphones), the Future Sonics FS1 are a top-choice pick.