This is a review and detailed measurements of the PSB M4U-1 headphone. It is on kind loan from a member. It is currently discontinued and seems to have come out back in 2012, costing US $230.
Time has not been kind to the specific sample I received which suffered from significant wear:
Anything that can wear out in it, has. It looks better in these pictures than in person:
The included cable has four pins and includes a microphone.
Overall comfort is good.
Note: The measurements you are about to see are preformed using standardized GRAS 45CA headphone measurement fixture. Headphone measurements require more interpretation than speaker tests and have more of a requirement for subjective testing as a result. In addition, comparison of measurements between different people performing it using different configurations requires fair bit of skill. So don't look for matching results. Focus on high level picture. Listening tests are performed using RME ADI-2 DAC and its headphone output.
Mounting the headphone on my test fixture was challenging, resulting in quite a lot of variation between channels and overall response. I optimized this as best as I could but like there are some error in low frequencies.
PSB M4U 1 Measurements
Let's start with frequency response of M4U-1 and comparison to our preference target to figure out tonality of the headphone:
I looked for measurements from others and only found a couple which showed much elevated bass than what I got. We will have to verify who is right with listening tests. Taken as is, bass is obviously deficient as critical range between 1 and 5 kHz which has a strong influence on spatial qualities and presentation of female vocals.
I expect the sound to be rather dull and uninteresting but also not annoying due to highs being controlled.
Distortion was remarkably low:
High-end headphones with tons of distortion should take note!
The low distortion should give us freedom to boost the holes in frequency response without fear negative consequences on that front.
Group delay shows messiness below 1 kHz which we also saw in frequency response:
As always, massive spikes in high frequencies indicates reflections inside the cup and not a sign of frequency response errors. So don't be tempted to narrowband correction.
Impedance is flat but also low so current delivery matters:
Then again, this is one efficient headphone:
So you should be able to use it on just about any source.
PBS M4U1 Headphone Listening Tests
The M4U1 sounds exactly like it measures. Nothing annoying but not too exciting either. I pulled out the parametric EQ in my Roon player and dialed in some sub-bass EQ and that fit like a glove. Added a quick filter for 1 to 5 kHz and job was basically done:
I had my son here so had him listen and he voted thumbs up on both fronts and the fact that the sound was not boomy or bass heavy post EQ.
I wanted to do more listening but alas, Roon folks just broke Tidal integration causing me to have a fraction of my test clips available for testing.
Based on what I did hear, with EQ, the sound was quite good. The boost between 1 and 5 kHz opened the soundstage and detail/instrument layering. The boost in bass was good although not quite substantial. It could stand accepting more based on taste.
Conclusions
The M4U1 has clear response errors that fortunately are correctable using EQ due to very low distortion. Good results can be had as a result. The problem is that the headphone itself seems to age poorly so not sure about getting a used one. Anyway, you have the data to make a decision.
Since the PSB M4U 1 is a discontinued item without performance that jumps out at you, I can't recommend it.
------------
As always, questions, comments, recommendations, etc. are welcome.
Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
Time has not been kind to the specific sample I received which suffered from significant wear:
Anything that can wear out in it, has. It looks better in these pictures than in person:
The included cable has four pins and includes a microphone.
Overall comfort is good.
Note: The measurements you are about to see are preformed using standardized GRAS 45CA headphone measurement fixture. Headphone measurements require more interpretation than speaker tests and have more of a requirement for subjective testing as a result. In addition, comparison of measurements between different people performing it using different configurations requires fair bit of skill. So don't look for matching results. Focus on high level picture. Listening tests are performed using RME ADI-2 DAC and its headphone output.
Mounting the headphone on my test fixture was challenging, resulting in quite a lot of variation between channels and overall response. I optimized this as best as I could but like there are some error in low frequencies.
PSB M4U 1 Measurements
Let's start with frequency response of M4U-1 and comparison to our preference target to figure out tonality of the headphone:
I looked for measurements from others and only found a couple which showed much elevated bass than what I got. We will have to verify who is right with listening tests. Taken as is, bass is obviously deficient as critical range between 1 and 5 kHz which has a strong influence on spatial qualities and presentation of female vocals.
I expect the sound to be rather dull and uninteresting but also not annoying due to highs being controlled.
Distortion was remarkably low:
High-end headphones with tons of distortion should take note!
The low distortion should give us freedom to boost the holes in frequency response without fear negative consequences on that front.
Group delay shows messiness below 1 kHz which we also saw in frequency response:
As always, massive spikes in high frequencies indicates reflections inside the cup and not a sign of frequency response errors. So don't be tempted to narrowband correction.
Impedance is flat but also low so current delivery matters:
Then again, this is one efficient headphone:
So you should be able to use it on just about any source.
PBS M4U1 Headphone Listening Tests
The M4U1 sounds exactly like it measures. Nothing annoying but not too exciting either. I pulled out the parametric EQ in my Roon player and dialed in some sub-bass EQ and that fit like a glove. Added a quick filter for 1 to 5 kHz and job was basically done:
I had my son here so had him listen and he voted thumbs up on both fronts and the fact that the sound was not boomy or bass heavy post EQ.
I wanted to do more listening but alas, Roon folks just broke Tidal integration causing me to have a fraction of my test clips available for testing.
Based on what I did hear, with EQ, the sound was quite good. The boost between 1 and 5 kHz opened the soundstage and detail/instrument layering. The boost in bass was good although not quite substantial. It could stand accepting more based on taste.
Conclusions
The M4U1 has clear response errors that fortunately are correctable using EQ due to very low distortion. Good results can be had as a result. The problem is that the headphone itself seems to age poorly so not sure about getting a used one. Anyway, you have the data to make a decision.
Since the PSB M4U 1 is a discontinued item without performance that jumps out at you, I can't recommend it.
------------
As always, questions, comments, recommendations, etc. are welcome.
Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
