Headphone Reviews

It was a real treat being able to talk with Paul Barton about the PSB M4U 8 and NAD HP70 at RMAF last year. Paul has lead acoustic design for PSB, NAD, and Bluesound for a long, long time now; he's got a strong understanding of audio and when he designs a product it speaks of this knowledge. In listening to this headphone, I find myself listening to both the headphone and what Paul may be trying to tell us with them. It's been an interesting dialog.

PSB M4U 8 ($399)
The PSB M4U 8 is a fully featured around-ear, noise canceling, wireless headphone. Styling is a bit clunky to my eyes with large oval gimbals around the rear capsule housing as the main design feature.

Visible materials are mostly plastics but apear of good quality. The headband has a sturdy internal spring steel structural element; headband hinges apear to be of chromed metal. Adjustment sliders are detented and slide in and out of the headband end/yoke piece, which is matte black, somewhat flexible, and slightly rubbery to the touch. Fit is secure and stable once set.

Headband and earpad covers are a nice quality leatherette. Ear cushions are memory foam. Earpad openings are somewhat small at 35mm x 60mm, but earpads are undercut on the rear side to permit room for the pinna to fit more comfortably. Overall fit on my slightly larger than normal head is cozy; this headphone hugs my head. I loosened the fit a little by bending the headband outward carefully, but I do think headphones for travelers should be quite secure on the head. A good seal is important for noise canceling to be effective.

The M4U 8 is amply accessorized with: a 59" analog cable (which can be plugged into either earpiece) terminated with a straight 3.5mm plug on the headphone end and a 90 degree 3.5mm plug on the player end; a 59" USB cable for charging and digital playback from a computer to 24/96; a 1/4" to 3.5mm adapter; an airplane adapter; a hard clamshell travel case; and, surprisingly, an extra pair of earpads.

Operation
The PSB M4U 8 has numerous modes of operation. It can be used in both analog and digital wired modes with the supplied analog and USB cables. With the analog cable, the headphones can be run passively without need for battery power. Active mode turns on the internal electronics and the analog signal is converted to 24/96 audio internally. The digital signal then passes through a digital signal processor (DSP) to impose the "RoomFeel" tuning. Another click up on the mode switch and active noise canceling (ANC) is engaged to further reduce interference from outside noise. When the USB cable is used the headphones must be turned on; only Active and ANC modes are available with the USB cable. The M4U 8 will accept up to 24/48 digital signal bit rates/depth over USB. When used wirelessly power must be on and "RoomFeel" tuning is always active. Again flipping the switch up to ANC will engage noise canceling.

Batteries for the M4U 8 are two AAA rechargeable batteries mounted behind the aluminum cover plate on the left earpiece. PSB claims about 15 hours of wireless active noise canceling run time on a full four hour charge. Should your batteries run out while on the move, in addition to just running them passively off the wire, you can replace the rechargeables with store bought AAA alkaline batteries. If you forget they're in and try to recharge them, there is a sensing system in the headphone to know it's loaded with alkaline batteries and will not attempt to charge them.

In both active and noise canceling modes a momentary push on the volume toggle will lower the volume of the music played and turn on the external microphones so you can hear external sounds like the flight attendant asking you if you want peanuts or cookies with your coffee.

The heart of the M4U 8 is Qualcomm's latest whiz-bang CSR8675 Bluetooth Audio SoC (system on a chip). This chip has all sorts of cool stuff on it including: Bluetooth 5.0; USB 2.0; aptX, aptX Low Latency, aptX HD, MP3, AAC, and SBC codecs; and 24-bit fixed-point 120MHz Kalimba DSP. This chip does have digital noise canceling capabilities, but PSB opted for an analog feed-forward and feed-back noise canceling circuit. Paul claims it delivers much lower latency for a more effective noise canceling circuit. My measurements indicate to me this is this headphone does a very good job of noise canceling—not quite as good as the Bose QC35, but close.

There are a total of six microphones on the M4U 8: two within the ear cup for noise canceling feedback; two on the top outside of each ear capsule behind the headband yokes, which are used for noise canceling feed forward and as the listening mics to hear your environment in 'Transperancy Mode'; and two mics on the bottom of the right earpiece, which are used only as a beam forming array for your voice in telephone conversation.

All controls are mounted on the rear of the bezel of the right earpiece and act precisely as one would expect. Both NFC and standard pairing is initially quick and easy. Subsequent pairing is lightening fast and reliable. Controls are ergonomically easy to identify and operate with your right thumb tip.

In sum, I found the PSB M4U 8 a solid, fully featured noise canceling headphone. Styling is a bit old school but finishes are tidy and well executed. Build quality and materials are very good at this price. Controls and electronics work flawlessly and lickity-split. Accessorization is very good. If sound quality is good, this is a solid product offering...let's have a listen.