Introduction
The UNIT-4 was always a slightly awkward object to travel with. The speakers ran on battery for 20 hours, the audio arrived uncompressed over W+ Link, and then you packed the bag and remembered that the transmitter needed a powered USB port and each speaker needed its own 20 V power brick with a regional cord. A battery-powered wireless monitor that still made you carry three power supplies was the one joke every review eventually made.
MKII is AIAIAI answering that, and almost nothing else. The spec sheet on AIAIAI's own product page now reads "Model: MKII", and if you put it next to the MKI sheet the only line that actually moved is "Power supply": it used to say "ACDC Converter, 120/240V to 20VDC 120W", and it now says "USB-C".
That's a small entry in a table and a large change in what the thing is. Charge the speakers over USB-C, drop the X04 transmitter into an MPC or a Digitakt with no power feed at all, and the UNIT-4 finally packs the way it always marketed itself.
Watch It in Action
AIAIAI's own overview of the platform. It was shot for the previous generation, and since the cabinet, drivers and W+ Link behaviour carry over unchanged, everything in it still applies.
What Actually Changed
- USB-C charging: the MKI spec sheet lists an AC/DC converter, 120/240 V to 20 VDC, 120 W, and the box shipped with power supplies plus regional cords. MKII lists "USB-C", and the set ships with two USB-C power supplies. One connector type for the speakers, the transmitter and the laptop.
- X04 transmitter with its own battery: the old X02 was a USB-C dongle that drew its power from whatever it was plugged into, which ruled out most standalone gear. The X04 carries an internal battery and a right-angle 3.5 mm lead, so it will hang off a groovebox, a mixer or a DJ setup with no USB host in sight.
- The carrying case is in the box: the MKI pair came with two compostable fabric pouches. The MKII set ships with the moulded UNIT-4 carrying case, which AIAIAI otherwise sells for €70, with room for both speakers, the transmitter and the cables.
- A white finish: black is still there, and white is new.
- Pricing: €300 for a single speaker, €600 for the set. The MKI launched at €800 for the pair.
What did not change: the 4 inch paper cone woofer, the 1 inch silk dome tweeter, the 2 x 30 W bi-amp, 105 dB peak SPL, the 77 Wh battery and its 20 hours, W+ Link at 16 ms and 12 m, Bluetooth 5.2, the 3.5 mm and 6.3 mm inputs, the 3/8 inch stand thread and the glue-free repairable chassis designed with Panter&Tourron.
One correction worth making, because it has already been repeated: Gearnews reported on 23 September 2026 that MKII has "a lighter build that takes the weight down to just 2.5 kg per speaker". AIAIAI's own spec tables list 2540 g per unit for MKI and 2540 g per unit for MKII. The speaker didn't get lighter. What changed is the charging: the 120 W, 20 V bricks are gone, and the set now ships with two USB-C power supplies instead.
Key Features & Benefits
- Uncompressed wireless, not Bluetooth with a nice name: W+ Link sends 44.1 kHz 16-bit audio uncompressed at a fixed 16 ms over 12 m, with dual antennas. Bluetooth 5.2 is still there for casual playback, and the difference between the two is audible.
- A transmitter that works with gear that has no computer in it: this is the practical consequence of the X04's battery. An MPC Live, a Digitakt, a mixer booth output, a field recorder: anything with a headphone or line out becomes a wireless source.
- 20 hours per charge, 2 hours to refill: a full day of tracking off a 77 Wh cell, then back to full over the same USB-C charger you already carry.
- Reference tuning in 3 litres: 50 Hz to 20 kHz at ±2 dB, extending to 40 Hz at -10 dB, from a cabinet the size of a hardback book.
- The bass vent is the handle: the rear port is shaped as a grip, so there's no accessory to buy in order to carry one in each hand.
- Mono, stereo or one on its own: a rear switch pairs them as a stereo set or runs a single unit in mono, which is what makes a single €300 speaker a sensible purchase rather than half a purchase.
- Built to be opened: glue-free construction, two screwdrivers, and replaceable batteries and driver units. AIAIAI publishes the repair guides and runs a trade-in programme for old units.
- App EQ: a 5-band EQ with saved profiles, plus control over the LED ring around the woofer.
Real-World Reactions
MKII has only just been announced, so nobody has reviewed it yet. The platform underneath it has been reviewed thoroughly, and in this case the old reviews are unusually useful, because the thing they complained about is the thing AIAIAI just fixed.
"Uncompressed, CD-quality wireless monitoring. Natural, balanced sound with lots of power available."
Hollin Jones, MusicTech, 9/10
That same review lists exactly two cons. The second is that W+ Link has to matter to you to justify the price, which is still true. The first is printed as "No USB-C power option". That line is now out of date, which is about the best outcome a hardware revision can hope for.
"Great sounding and (almost) latency-free wireless monitoring, we never thought we'd see the day. While you might not absolutely need Unit-4, this is undoubtedly a very desirable monitoring setup."
Andy Jones, MusicRadar, 23 November 2023
His pros were the sound, the near-absence of latency, the setup and, charmingly, the LEDs. His single con was a question: "Do you really need wireless studio monitors? (Be honest)". He also reported "the odd interference crackle, very slight and very quiet", on a review unit of the original. We'd treat both as still open until someone tests MKII, since the radio hasn't changed.
Gallery
Every angle in one place. Click any shot to open it full size.
Who It's For
- Producers who actually move. If your studio is a laptop, a controller and whatever table is free, the MKII is the first version where the whole system fits one bag and one charger.
- Groovebox and hardware players. The X04 running on its own battery is aimed squarely at the MPC, Digitakt, SP-404 crowd who have no USB host to power a dongle from.
- DJs practising away from a booth. Line out of the mixer into the X04, two speakers wherever there's room, no mains run.
- Small rooms where a wired pair would mean visible cable. A single unit at €300 is a genuine option here, not a compromise, because mono is a switch on the back.
- Anyone who keeps gear for a decade. Replaceable batteries and drivers, published repair guides, two screwdrivers.
Who should look elsewhere:
- Existing UNIT-4 owners. The sound is identical. You'd be buying a charging port and a bag.
- Anyone mixing loud in a treated room. 4 inch woofers and 105 dB peak are honest numbers, not big ones, and a wired pair at this money will move more air.
- Anyone who needs room correction. The app gives you a 5-band EQ and nothing more clever than that.
- Anyone whose sources are all Bluetooth. You'd be paying for a W+ Link radio you never switch on.
Quick Specs
- Type: 2-way active battery-powered monitor, bass reflex
- Woofer: 4 inch high-excursion paper cone
- Tweeter: 1 inch silk dome
- Amplification: 2 x 30 W continuous, 2 x 80 W peak, bi-amped
- Frequency response: 50 Hz to 20 kHz (±2 dB)
- Frequency range: 40 Hz to 40 kHz (-10 dB)
- Peak SPL: 105 dB
- Wireless: W+ Link, uncompressed 44.1 kHz 16-bit, 16 ms latency, 12 m range, via X04 transmitter
- Bluetooth: 5.2
- Analog inputs: 3.5 mm mini-jack and 6.3 mm TRS balanced
- Battery: 77 Wh, 20 hours playback, 2 hours to charge
- Power: USB-C
- Mounting: 3/8 inch thread for a standard mic stand
- Dimensions: 156 x 258 x 114 mm per unit
- Weight: 2540 g per unit
- Finishes: black, white
- In the set: 2 speakers, 2 USB-C power supplies, X04 transmitter, carrying case
- Model designation: MKII
Pros & Cons
✅ Pros:
- USB-C charging replaces the proprietary 20 V power bricks that undermined the whole portable premise
- The X04's internal battery opens W+ Link up to standalone hardware with no USB host
- The €70 carrying case is now included with the set, and the set costs less than the MKI did
- Uncompressed 16 ms wireless that nothing else in this class offers
- Repairable by design, with replaceable batteries and drivers
⚠ Cons:
- Nothing about the sound changed, so there's no reason for an existing owner to upgrade
- Still 2540 g per speaker, despite reports to the contrary
- 4 inch drivers and 105 dB peak put a real ceiling on room size and level
- App EQ only, no room correction
Where to Buy
The UNIT-4 MKII set is now live in the Soundium catalogue as a pre-order at €599, in black or white, with two speakers, two USB-C power supplies, the X04 transmitter and the carrying case in the box. Our first units are still on their way from the distributor, so the product page carries an expected-arrival month, and the EARLY5 code takes 5% off if you order before they land.
- Free pickup shipping on orders over €149
- Free courier shipping on orders over €299
- Authorised AIAIAI warranty
- Support from people who actually know the gear
AIAIAI UNIT-4 MKII: €599 · AIAIAI at Soundium · Talk to our team
Final Thoughts
There's a version of this launch that would have been a new driver, a new DSP and a new price. AIAIAI did something less exciting and more respectful: they read the reviews, found the one sentence that kept appearing, and deleted it. "No USB-C power option" was the only real complaint anyone had about a speaker that otherwise did something nobody else did. Now it charges over USB-C, the transmitter runs off its own battery, the case comes in the box and the set is €200 cheaper than the original pair. That's not a new product. It's the same product, finally finished.
Still Unsure?
Tell us what you'd be feeding them, how big the room is and whether you need one speaker or two, and we'll tell you honestly whether the UNIT-4 is the right call or whether a wired pair at the same money will serve you better. Reach out to our team.