PSB Speakers announced a unique two-way hybrid design in-ear monitor for $299. The new M4U 4 features a moving coil dynamic low frequency driver and a balanced armature high frequency driver controlled by a precision crossover network. The company claims this design is ideal for reproducing high frequencies with great transient response and detail. Musical textures are finely wrought, bringing great insight into the music and clearly delineating individual instruments and their unique voices. The precision BA driver used in the M4U4 is individually calibrated to meet the exacting response tolerances of this In-Ear-Monitor. A wave-guide is used to link the sound tube of the BA driver to the woofer, creating time-aligned driver integration. A miniature PCB using surface mount parts creates the electrical crossover network that divides the signal between drivers.
The moving coil dynamic woofer is no less unique, tuned for accurate response with three separate chambers, creating an aperiodic loading that smooth’s response and suppresses resonances. The result is deep, deep bass response that is punchy and crisp without sounding fat or boomy. 
Voiced for a flat, neutral response, the PSB M4U 4 was developed at the NRC (National Research Council of Canada) using the KEMAR dummy head testing system, with the addition of low frequency room gain that one would expect to hear with normal loudspeakers in a room. This is the same room gain compensation transfer function that was developed in the ATHENA PROJECT at NRC.
These findings have led PSB to a unique feature the company calls, RoomFeel. RoomFeel makes music sound more natural by taking into account the effects of the room on music playback. Almost all recorded music is monitored using direct radiating loudspeakers to determine the acoustic balance for the final mix. So the transfer function PSB developed for its M4U 4 headphones takes into account the “room gain” that occurs when playing direct radiator loudspeakers in a room. The result is a much richer, more immersive and more natural listening experience.
Comfort and Ergonomics
The M4U 4 was ergonomically designed to be comfortable even when worn for long periods of time. Comfort was paramount in the M4U4’s development, which led to several useful features. First of all, the cord is detachable and the IEM’s are reversible. The user has a choice of looping the cord over and behind their ear, or they can swap the left for right color-coded cord to allow the cord to drop down in front of the ear.
Three sizes of soft inserts are included to fit any size ear canal, and two types are provided; soft silicone and Comply Foam™ with wax guards. Comply foam is extremely comfortable, precisely fitting the individual ear canal and forming an air-tight seal that blocks outside noise and provides amazing bass extension. Silicone tips are also comfortable and can be cleaned and reused indefinitely.

Convenience and Ease of Use
The M4U 4 can be easily stored and transported in a semi-hard travel case. M4U 4 features a unique detachable cord with a removable shirt clip. Two tangle-free cords are supplied, one is made for iPhone with convenient microphone and telephone controls. Also supplied are a 1/4 inch adaptor and a dual 1/8 inch airplane adaptor.
Features
- Two-way hybrid design with Moving Coil Dynamic LF Driver
- Balanced Armature HF Driver
- Precision Crossover Network
- RoomFeel for immersive, lifelike experience
- Two tangle-free cords supplied, one made for iPhone certified
- Unique detachable cord design with removable shirt clip
- Comes supplied with Silicone and Comply Foam Ear Tips in small, medium and large
- Comes supplied with travel case, ¼” stereo and 1/8” dual input flight adaptors
Price and Availability
The PSB M4U 4 comes in choice of Black Diamond or Arctic White finishes and will be shipping for $299 in June, 2015.
