Sleeping
Concerts
Motorcycle
Swimming
Work
Kids
On stage
In the studio
Rehearsals
Writing music
Mixing at home
Daily commute
Long journeys
Listening at home
- Official UM partnerUK & EU, genuine stock
- 2-year warrantyHandled by our own team
- 14-day returnsUniversal Fit, seal unbroken
- Hand-builtBy UM's master artisans
The Mason FS feeling
Music that feels played, not reproduced
Reviewers describe a smooth, full-bodied sound where real instruments sound real and long sessions pass without fatigue.
Find your Unique Melody in 3 taps
Is the Mason FS the one for you?
Three questions, honest answer. If another model suits you better, we will say so.
1What do you play most?
2How do you feel about treble?
3What is your budget?
Your match
3 questions to go
Answer the questions and we will match you to the right model.
Watch before you buy
Don't take our word for it.
Mason FS has few video reviews. Three of them show the original 2021 Mason FS, which used an earlier bone-conduction driver; they are marked (2021).
Independent reviews. Plays right here, and only loads when you press play.
No time for 20 minutes?
Skip straight to what you care about
Each one plays the review from that exact moment.
The sound
Rich, analogue and naturally warm
A work of art you can listen to: Van Gogh’s Starry Night or a falling sun, with 13 drivers inside.
BOLLSEN sound map, summarised from independent reviews.
Maybe not for you if you want fast, punchy bass for EDM or a lean, analytical sound; the Multiverse Mentor is leaner and more resolving.
Inside Unique Melody
Hand-built by people who have done it for a decade.
Every pair is assembled, soldered and tuned by hand in Unique Melody's own five-storey workshop, then listened to and measured before it ships.
Photos and facts © Unique Melody.
Inside the shell
13 drivers, two drive systems
Twelve balanced armatures run on your player’s current, while the BC-Turbo booster steps it up to drive the frequency-shift bone-conduction driver, all through a 5-way crossover.
- 014 × BA bass: fullnessRounded, textured lows that reviewers liken to a dynamic driver.
- 024 × BA mids: voicesFuller lower mids for a rich, natural tone.
- 032 × BA mid-treble + 2 × BA treble: clarityA lower-treble lift adds definition without harshness.
- 04BC-Turbo bone conduction: depthA micro booster drives the bone-conduction driver for texture and stage.
As seen on YouTube
6 honest reviews. Watch, listen, decide.
Life with Mason FS
Wherever the music takes you.
Choose your fit
Ready to wear, or moulded to your ears.
Custom Fit is moulded to your ears for a perfect seal and all-day comfort. Universal is the fast, flexible way in.
| Universal Fit | Custom Fit | |
|---|---|---|
| How it fits | Ear tips in several sizes | Hand-built from impressions of your ears |
| Bass and isolation | Great with the right tip | Steadier bass, more isolation |
| Bone-conduction effect | Subtle | Strongest |
| Delivery | DHL Express, 5–7 working days | 3–4 weeks after we get your 3D scans |
| Returns | 14 days, hygiene seal unbroken | Made to order: free refit instead |
How Custom Fit is made · UM has built custom monitors since 2006
Find where to get your ears measured
Custom Fit monitors are made from ear impressions or a 3D scan of your ears. We accept both. Audiologists and hearing centres across the UK and Europe can take them in a short appointment.
- 1Order Custom Fit
- 2Book impressions or a 3D scan
- 3Send them to us
- 4Yours in 3–4 weeks
When you call, ask for “ear impressions for custom in-ear monitors”.
Most clinics charge a small fee. Our ear-impression guide arrives by email after you order.
When you call, ask “Do you offer 3D ear scanning for custom in-ear monitors?”
Not every clinic has a scanner, so ask first. Our guide email after you order explains how to send us the scan file.
Reviews
What owners and reviewers say
independent video reviews on this page
Twister6 and a detailed Head-Fi owner review agree the 2024 Mason FS is a full-bodied, neutral-warm flagship with natural timbre, textured bass and a big, holographic stage. The main caveat is synergy: treble energy shifts with the player and ear tips, and some listeners find the upper mids a touch edgy.
What they love
- Natural timbre: piano and strings sound real (Head-Fi)
- BA bass with the texture and rumble of a dynamic driver (Twister6)
- Wide, deep stage with precise imaging
- Equally convincing with male and female vocals (Head-Fi)
Worth knowing
- Source-sensitive: some players push the treble too hard (Twister6)
- Upper mids can sound a little edgy to some ears (Smirk Audio)
- Laid-back bass, not a tight, fast punch for EDM (Twister6)
Summarised from Twister6, Head-Fi review, IEMRanking (reviewer scores).
Own the Mason FS? Add a photo and tell other listeners what you hear.
The details
Everything you need, nothing to add.
In the box
- Mason FS monitors (pair) in the edition you choose
- UM First Times Shielding Pro cable, 4.4 mm balanced (included)
- Leather case and hard shell case
- Oval and ring cable clamps, tote bag and spare filters
- AZLA SednaEarfit Xelastec and UM silicone ear tips
- Cleaning cloth and warranty card
Contents as supplied by Unique Melody and may vary slightly by batch.
Key specs
- Drivers: 13 per side: 4 BA bass, 4 BA mids, 2 BA mid-treble, 2 BA treble, 1 BC-Turbo Micro Booster and frequency-shift bone conduction
- Crossover: 5-way
- Impedance: 23 Ω
- Frequency response: 20 Hz – 40 kHz
- Connector: 2-pin
- Cable included: UM First Times Shielding Pro (blue with Nuit Étoilée, red with Soleil Tombé), 4.4 mm balanced
- Fit: Universal or Custom Fit
Delivery
- Universal Fit: DHL Express, 5–7 working days
- Custom Fit: 3–4 weeks after we receive your 3D ear scans
- Price includes UK VAT
Warranty & returns
- 2-year BOLLSEN warranty with UK & EU support
- Universal Fit: 14-day returns with the hygiene seal unbroken
- Custom Fit: made to order, free refit if the fit is not right
- Your statutory rights are not affected
Product safety
Compare the range
Mason FS, Mentor or Fortune?
You are here Mason FS |  Multiverse Mentor |  MEST Fortune | |
|---|---|---|---|
| Character | Full-bodied, analogue, natural | Leaner, more resolving | Airy, detailed, deep stage |
| Bass | |||
| Vocals | |||
| Staging | |||
| Selected | View Multiverse Mentor | View MEST Fortune |
Character summarised from independent reviews.
FAQ
Your questions, answered
Is this the same as the 2021 Mason FS or FuSang?
No. It keeps the 12-armature layout, but the 2021 models used a dual-sided piezo bone-conduction driver; the 2024 editions add the BC-Turbo booster and FreqShift bone conduction. Twister6 heard more bass weight and smoother treble than the earlier Le Jardin edition.
Does my player make a difference?
More than usual. At 23 Ω it is easy to drive, but Twister6 found warm, tube-style players brought out its natural tone, while one bright player made it V-shaped with hot treble. Ear tips matter too: AZLA and Symbio W suited it best.
Which edition should I choose?
They sound the same. Nuit Étoilée is blue and gold after Van Gogh’s Starry Night; Soleil Tombé is red and amber like a sunset. Each comes with a cable in a matching colour.
Which plug does it come with?
The cable is included and ends in a 4.4 mm balanced plug, the connection dedicated music players and balanced DACs use. If your source only has a 3.5 mm socket, add a 4.4 mm dongle DAC or ask us which one suits you.
Is every pair unique?
Each shell is carved and finished by hand, so small differences in colour and pattern are part of its character.
Is there a Custom Fit version?
Yes. Choose Custom Fit above: Unique Melody hand-builds it from a 3D scan or impressions of your ears, taken by a hearing specialist near you. It arrives 3–4 weeks after we receive them, with a free refit if the fit is not right.
Universal or Custom Fit: which should I choose?
Universal Fit arrives fast and uses ear tips. Custom Fit is moulded to your ears: a perfect seal, steadier bass and the strongest bone-conduction effect.
How does ordering a Custom Fit work?
Choose Custom Fit and order. We email our 3D-scan guide, a hearing specialist near you takes a 3D ear scan or ear impressions (usually charged separately), and your monitors arrive by DHL Express 3–4 weeks after we receive them. Not right? We arrange a free refit.
How fast is delivery?
Universal Fit is delivered by DHL Express in 5–7 working days. Custom Fit is made to order: delivered 3–4 weeks after we receive your 3D ear scans.
What warranty and returns do I get?
A 2-year BOLLSEN warranty handled by our UK & EU team. Universal Fit can be returned within 14 days with the hygiene seal unbroken. Custom Fit is made for your ears, so instead of a change-of-mind return you get a free refit. Your statutory rights are not affected.
Why buy from BOLLSEN?
BOLLSEN is the official Unique Melody partner for the UK and EU: genuine stock, a 2-year warranty from our own team, clear delivery times and help choosing.
Bought from a hearing company. Looked after for 2 years.
The official Unique Melody partner for the UK & EU: genuine stock, help choosing and warranty support from our own team.
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