We compare products from their published specs and features; the verdicts below are our independent editorial opinions.
Updated: 2026-09-21 · 7 min read · Independent comparison
If you want a compact, do-everything recording front end for a mic and a guitar, choose Kellards Focusrite Scarlett Solo; if you need a full monitoring-and-tracking setup built around a pair of Bluetooth studio speakers, choose M-AUDIO BX4. That single sentence is the whole decision. Everything below explains why I split it that way.
• Kellards Focusrite Scarlett Solo — biggest strength: a genuine studio-grade 2-in / 2-out USB-C interface with 24-bit/192 kHz converters, 120 dB dynamic range, an ultra-low-noise mic preamp, a Hi-Z instrument input and a selectable Air circuit — plus a bundle that already includes headphones, a pop filter and an XLR cable.
• Kellards Focusrite Scarlett Solo — biggest trade-off: it's a recording input device, not a playback system. There are no speakers in the box, so you're monitoring through the supplied headphones unless you already own monitors.
• M-AUDIO BX4 — biggest strength: it's a complete studio bundle — a pair of BX4 studio monitors, a dual XLR audio interface and headphones — with Bluetooth streaming for casual listening thrown in.
• M-AUDIO BX4 — biggest trade-off: the published spec sheet is much thinner. There's no stated sample rate, dynamic range or preamp noise figure, so you're buying on the strength of the bundle concept rather than documented converter specs.
• Who each pick is for: the Scarlett Solo is for the singer-songwriter who records one mic and one guitar at a time. The BX4 bundle is for the producer who needs speakers in the room and more than one input at once.
This is, in the manufacturer's own framing, "the songwriter's interface" — and the specs back that up. You get two inputs and two outputs in a USB-C box: an ultra-low-noise microphone preamp and a Hi-Z instrument input, which means you can plug in a vocal mic and a guitar simultaneously and capture both. For someone who writes on acoustic guitar and sings over it, that's the entire job description handled by one small device.
The numbers here are the real story. The 4th-gen Solo runs 24-bit / 192 kHz AD/DA conversion with up to 120 dB of dynamic range, and Focusrite states these are the same converters used in its flagship interfaces. Air mode adds brightness and harmonic drive to lift vocals and guitars forward in the mix. There's also a Loopback feature that lets podcasters, streamers and gamers blend audio from other apps on the computer into what the interface records — a genuinely useful trick for anyone doing live content rather than just music. It can even run in standalone mode without a computer, which makes it more flexible than a purely USB-tethered box.
Who should buy it: solo artists, guitar-and-voice songwriters, podcasters and streamers who record one or two sources at a time and want documented converter quality with almost no learning curve.
Who should skip it: anyone who needs speakers in the room to mix on, or who regularly records a drum kit, a full band, or several mics at once. Two inputs is the ceiling here, and there's no monitor pair included.
M-AUDIO BX4: Who It's For
The BX4 bundle attacks the problem from the opposite direction. Instead of giving you one excellent input device and letting you sort out monitoring later, it hands you the whole room: a pair of BX4 Bluetooth studio monitors, a dual XLR audio interface, and a set of monitoring headphones. The pitch is a comprehensive audio setup in one purchase — monitors for mixing and critical listening, interface for capture, headphones for isolated detail work.
The dual XLR interface is the practical upgrade over the Solo's single preamp path. Two XLR inputs means you can record multiple sources at the same time — two mics, a mic and a DI, a stereo pair — without swapping cables between takes. For a producer tracking a vocalist and an instrument together, or a podcaster running a two-person show, that's the difference between a workflow and a workaround.
Bluetooth is the feature that separates this bundle from a strictly studio-only kit. You can stream music wirelessly to the monitors for casual listening, reference tracks, or just background audio while you work. That makes the BX4 pair double as a decent everyday speaker system, which is more than you can say for a bare audio interface.
The honest caveat is the documentation. The spec sheet lists the monitors' driver type as dynamic and confirms the bundle contents, but it doesn't publish sample rate, dynamic range, or preamp noise figures the way the Scarlett Solo's sheet does. The description promises "exceptional clarity and accurate sound reproduction" for mixing, mastering and critical listening — which is exactly what you'd expect a monitor bundle to claim — but there's no converter specification to compare against the Focusrite's 120 dB figure. If you like to buy on hard numbers, that's a real gap.
Who should buy it: home studio producers and engineers who need speakers, more than one input, and a wireless listening option, and who want it all arriving together.
Who should skip it: anyone who already owns monitors and just needs a clean two-input interface, or anyone who specifically wants published converter specs before committing.
• Best for a singer-songwriter recording voice and guitar → Kellards Focusrite Scarlett Solo. One mic preamp plus one Hi-Z instrument input is precisely that use case.
• Best for a full monitoring setup out of the box → M-AUDIO BX4. Monitors, interface and headphones arrive as one package; the Solo gives you headphones only.
• Best for documented converter quality → Kellards Focusrite Scarlett Solo. 24-bit/192 kHz, 120 dB dynamic range, converters shared with Focusrite's flagship line.
• Best for recording two XLR sources at once → M-AUDIO BX4. The dual XLR interface covers simultaneous multi-source capture; the Solo tops out at one mic plus one instrument.
• Best for podcasting and streaming with app audio → Kellards Focusrite Scarlett Solo. The Loopback feature mixes computer audio into the recording, and standalone mode means it works without a laptop attached.
• Best for wireless casual listening → M-AUDIO BX4. Bluetooth streaming to the monitors is something the Solo simply doesn't do.
• Best for a guaranteed software and accessory bundle → Kellards Focusrite Scarlett Solo. Pro Tools Artist, Ableton Live Lite, Hitmaker Expansion, headphones, pop filter and an XLR cable are all included.
• Best for buyers who want published specs before spending → Kellards Focusrite Scarlett Solo. The BX4 sheet is far lighter on measurable detail.
If I were spending my own money and my goal was to actually record music well, I'd buy the Kellards Focusrite Scarlett Solo. The reason is simple: it's the only one of the two with a fully documented audio chain — 24-bit/192 kHz, 120 dB dynamic range, an ultra-low-noise preamp, Air mode and Loopback — and it arrives with the accessories and software needed to start immediately. I'd pick the M-AUDIO BX4 instead if my priority were having speakers in the room, two simultaneous XLR inputs, and Bluetooth playback, and if I were comfortable buying a bundle whose converter specs aren't published. One is a precision input tool; the other is a room-filling starter studio. Decide which of those two you actually need, and the choice makes itself.
For a single vocal take, yes — in my opinion. The Solo publishes an ultra-low-noise preamp, 120 dB dynamic range and Air mode for vocal presence. The BX4 bundle doesn't publish equivalent preamp or converter figures, so there's less to compare against.
Yes. The bundle includes a dual XLR audio interface, which supports recording multiple sources simultaneously. The Scarlett Solo is limited to one microphone input plus one instrument input.
Not to start. The bundle includes Polsen HPC-A30 studio monitor headphones, so you can record and mix on headphones. You'd add monitors later if you want to hear your mixes in a room, which the BX4 bundle covers from day one.
That depends on what you already own. If you have no speakers, the BX4 bundle covers monitoring, capture and listening in one purchase. If you already have monitors and just need a clean interface, the Scarlett Solo's documented specs and included software make it the more focused buy. Check the current price on Amazon for both before deciding, since bundle contents and pricing shift over time.
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