Sometimes something really new can be found in updated legacy devices.

SR-L700 MKII Earspeaker and the SRM-D10 Portable Driver Unit for Earspeakers

That’s the case with the latest incarnation of the Stax SR-L700 MKII Earspeakers, a reference design which is one of the most impressive devices for listening to music that I’ve ever heard.

This latest ‘earspeaker’ from Stax, who feels that the term ‘headphones’ doesn’t do justice to their products, impressed me and every audiophile that auditioned my review unit. They are comfortable, highly revealing, and really require the best quality program material. Playing some garden variety CDs will immediately make it clear that the recordings are not the best. Even little details in the recording room like the HVAC or the movement of music stands are quite apparent. This is both a blessing because the Stax SR-L700 MKII Earspeakers are so revealing and a curse because you will hear ‘everything.’ Stax headphones will spoil you for anything else. While expensive, they deliver, and people who enjoy listening to headphones in a serious way will want to audition them.

SR-L700 MKII Earspeaker


SR-L700 MKII Earspeaker and the SRM-D10 Portable Driver Unit for Earspeakers

  • Best headphones I’ve heard and these are not the top of the line products from Stax.
  • Comfortable, but they do require an external driver unit. The sheep leather ear pads are easy on the ear and head.
  • Exchangeable cable structure
  • Extremely wide frequency response (7-41,000 Hz!)
  • Open Air design will appeal to many who don’t want to be cut off from room sounds.
  • Expensive, but the advantages are immediately audible.
  • I reviewed the SRM-D10 Portable Driver Unit which does not require AC current, but it is heavy and something extra to carry around.

First off, what is an electrostatic driver and how is it different from other headphones?

SRM-D10 Portable Driver Unit

I’ll give you a simplified explanation of the differences.

Most headphones use dynamic drivers. They are basically a scaled down version of the speakers that might be powering your desktop speakers. A small coil carrying the signal moves the driver and produces music.

Planar drivers are now getting very popular among discriminating listeners. They are similar to dynamic drivers, but instead of focusing the magnetic field on a small section of the driver, a planar driver is wired to work on the whole panel of the driver, using more points of contact and more magnets.

Electrostatics have a long history, and Stax was a pioneer in the design. Koss also offered, and still offers, some electrostatic designs. Simply put, electrostatic drivers are usually a thin mylar that is sandwiched between two conductive plates. Electrostatic headphones require an amplifier or energizer box to set the drivers in motion, so we’re reviewing the Stax Headphones with the required accessory amplifier. Stax has a variety of amplifiers at different price points, but I liked the idea of a portable driver unit so that’s what I’m evaluating here.

The SR-L700 MKII Earspeaker has the classic Stax electrostatic sound, and by that I mean smooth and extended high frequencies, fast transient response and deep bass. The company has been in business since 1938 starting with the design and sale of condenser microphones and then moving on to electrostatic tweeters and then finally to headphones – aka Earspeakers in the late 1960s. Stax has also produced Electrostatic speakers and even an amplifier.

I owned a pair of the Stax electrostatic Lambda Earspeakers many years ago when I was in college. Sadly, the driver box went out after a couple of years, and I was a poor student and couldn’t afford to fix them. I sold my Stax as-is to a more well-off student, and he enjoyed them for many years after that. I envied him.

When I heard that the descendant of that very Earspeaker was alive and well in a much more evolved product, the SR-L700 MKII, I just had to hear it.

While Stax makes many driver units that will power their headphones, I was most interested in a portable unit that did not need to be plugged into house power. The SRM-D10 is a rechargeable unit. You can listen anywhere without need of AC power. It seemed like the way to go for my lifestyle.

SRM-D10 Portable Driver Unit Front