We compare products from their published specs and features; the verdicts below are our independent editorial opinions.
Updated: 2026-09-25 · 7 min read · Independent comparison
If you want to combine two stereo sources into one clean headphone feed for mixing and monitoring, choose SOLUPEAK M21; if you need to restore the comfort of a worn OneOdio mixing headphone you already own, choose SOULWIT Headband.
• SOLUPEAK M21 — biggest strength: a true powered 2-in / 1-out stereo mixer with independent volume knobs, so you can blend a computer and a phone into a single pair of headphones without swapping cables.
• SOLUPEAK M21 — biggest trade-off: it is a desktop box that needs its included 12 VDC adapter, and it takes 3.5 mm connections only — no 1/4-inch jacks and no wireless.
• SOULWIT Headband — biggest strength: a curved-stitch protein leather replacement headband made specifically for a long list of OneOdio mixing models, which is exactly the kind of part that wears out first on a working pair.
• SOULWIT Headband — biggest trade-off: it does not make sound and does not fit every headphone — it only helps if you own one of the listed OneOdio models.
• Pick the M21 if your problem is routing and blending audio sources. Pick the SOULWIT Headband if your problem is a tired, flaking headband on headphones you still like.
The M21 is a small aluminum stereo mixer built around 3.5 mm sockets: two inputs, one output. Both inputs are summed into that single output continuously, which is the whole point. You plug your computer into one input and your phone into the other, and you hear both at once — no unplugging, no switching, no dongle juggling. Each input gets its own front-panel knob, so you can pull the music down and push a reference track up, or balance a call against a backing track.
That makes it a genuinely useful little hub for a desk where more than one device feeds one pair of headphones. Think of a laptop plus a tablet, a PC plus a hardware synth with a 3.5 mm out, or a phone plus a portable player. The chassis is solid aluminum rather than plastic, and the compact footprint suits home desk audio. SOLUPEAK describes the potentiometers as smooth-turning and durable, and the low-noise design is meant to keep the signal clean as you blend.
SOULWIT Headband: Who It's For
The SOULWIT Headband is a replacement headstrap pad, not an audio device. It is made from protein leather with a curved-stitching construction that is designed to follow the contour of the original headband and cut down on gaps and wrinkles where a flat cover would bunch up. The pitch is simple: if your OneOdio headphone still sounds fine but the top of the band has gone flat, cracked or uncomfortable, this restores the feel of the headphone without replacing the headphone.
Compatibility is the entire ballgame here. SOULWIT lists it for the OneOdio Pro-10, Pro-30, Pro-50, Studio Monitor & Mixing DJ, A71, A70, Studio Wireless C, Studio Pro-C and Y80B. The product listing is explicit that you should check your headphone model before buying, and that is the right advice — a headband cover that does not match your band's shape and width will either not fit or will look sloppy once installed. Installation is a peel-and-apply job: remove the old cover, then work the new one on following the included instructions.
Who should buy it: owners of one of those listed OneOdio models whose headband has worn out or become uncomfortable, especially anyone using them for long mixing sessions where pressure on the crown of the head adds up. Who should skip it: anyone with a different brand or an unlisted model, and anyone hoping this somehow changes the sound — it won't, because it is a comfort and repair part. Note that SOULWIT states there is no warranty on this item, so treat it as a consumable refresh rather than a long-term guarantee.
Side-by-Side: Which Should You Choose?
• Best for blending two sources into one headphone feed → SOLUPEAK M21. Two 3.5 mm ins, one out, both heard at once.
• Best for independent level control → SOLUPEAK M21. Separate knobs per input let you ride each track without touching the other.
• Best for reviving headphones you already like → SOULWIT Headband. A comfort and repair part for a specific list of OneOdio models.
• Best for long listening or mixing sessions on OneOdio cans → SOULWIT Headband. Protein leather and contour stitching target head-top pressure and wear.
• Best if you own 1/4-inch or balanced studio gear → neither, as-is. The M21 is 3.5 mm only, and the headband only fits the listed models.
• Best if you want wireless or battery power → neither. The M21 is adapter-powered; the headband has no electronics at all.
• Best upgrade path if you're unsure → check your gear first. If your source routing is the problem, it's the M21. If your headband is the problem and your model is listed, it's the SOULWIT.
In my opinion, these two products solve completely different problems, so the honest answer is that most people only need one of them. If you are building a small desk setup and you constantly find yourself swapping cables between a computer, a phone or a tablet and one pair of headphones, I would buy the SOLUPEAK M21 — the two-knob, two-in/one-out design is exactly the tool for that job, and the aluminum build suggests it will sit on a desk for years without fuss. I would buy the SOULWIT Headband only if I already owned one of the listed OneOdio models and the top of the band had worn out. If you're torn, ask yourself which is actually broken: your signal flow, or your comfort.
how to connect studio headphones
For a headphone like the OneOdio models listed here, you connect the cable to the headphone's input jack and the other end to your source — a computer, interface, phone or mixer. With the SOLUPEAK M21, that same headphone plugs into the single 3.5 mm output while your two sources feed the two 3.5 mm inputs, and you control each with its own knob. The M21 needs its included 12 VDC adapter connected before it will pass signal.
how to test studio headphones
A practical check is to play a track you know well and listen for balance between left and right and for any rattle or distortion at moderate volume. If you want to compare two sources or two mixes through the same headphones, the M21 lets you feed both in at once and switch attention between them by turning one knob down — no cable swapping. If the headband itself is uncomfortable or worn during that session, that's the signal to look at a replacement cover like the SOULWIT.
how to bluetooth studio headphones
Neither product here adds Bluetooth. The M21 is a wired 3.5 mm mixer that runs on a 12 VDC adapter, and the SOULWIT Headband is a passive leather replacement part with no electronics. If your headphones are wired-only, they stay wired; to go wireless you'd need a separate Bluetooth transmitter or a different pair of headphones entirely.
can you mix with just headphones
Yes — plenty of people do their critical listening on headphones, and a headphone-only workflow is common in small rooms and apartments. The catch is that headphones remove the room from the equation, so cross-checking on another system is wise. The M21 helps here by letting you keep two sources live at once — say, your mix and a reference track — and balance them with its two independent knobs instead of unplugging anything.
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