Stems get real (time) – digitalDrummer

When JBL told me about the launch of the BandBox, I wasn’t expecting a practical, out-of-the-box e-drum amplification system. What piqued my curiosity was the “AI-powered real-time vocal and instrument separation” which the electronics giant was pitching as part of its smart practice amp.

For the record, I have spent the best part of a decade researching drumless tracks for e-drummers. This pursuit has led to clashes with unscrupulous operators who muted the drum stems on commercial products and then sold the output as their own work, flagrantly violating someone else’s copyright. Then there were DAW plug-ins which required a degree in advanced engineering to operate — and even then produced questionable results. Now we have a flood of online stem separators – many of them free, but none delivering drumless tracks in real time.

What’s in the box

I tested the BandBox Trio, the larger of the two launch models. The Solo version, an 18 W amp, is designed for home practice and I’d imagine its single driver may well rip apart at the first serious bass drum hit.

The stylish Trio practice amp houses a modest (by e-drum standards) 135 W amplification array consisting of a 6.5″ woofer and two 2.5″ tweeters.

There are two XLR mic/instrument inputs, a ¼” instrument input, a ₁/₈” aux input, a USB-C input/output which connects to a DAW (Digital Audio Workstation) and a Bluetooth input.

Since this is primarily a guitar/vocal amp, there are a number of features which are not really of interest to e-drummers, including guitar effects and a tuner, but some are potentially useful for stick-wielders: a looper and a metronome.

It’s all controlled via a large colour LCD screen which can be flipped to face inward or outward, depending on your playing position.

In action

It’s not often that I am pleasantly surprised by new products, and even less so when it comes to e-drum amplification — but this little box punched well above its weight.

Driving it via Bluetooth from my DAW, I was amazed at the thump of this amp. It really had more low-end presence than many dedicated drum amps in the home practice market, probably because it’s designed to amplify backing tracks as well as the vocals/guitar inputs for its users. The bass was punchy without distorting, and I really didn’t need to push it beyond the 1 o’clock position in the EQ screen. The treble was crisp and tight, handling the hats and snare with aplomb. If there was one gap in the sonic spectrum for drums, it was the mids, which were somewhat subdued.

Connected directly to a drum module via a pair of TS cables — using separate channels for left and right, the amp again surpassed expectations. The bass was solid and defined, the highs were bright and crisp, and even the mids were fairly well represented.

Mixing drums and backing was easy, thanks to the independent channel controls.

But what about the real appeal — stem separation?

The technology is clearly designed for singers and guitarists, so the AI stem engine produces three stems: vocals, guitar and “others”. Each can be dialled down to zero, and the removal of the first two is very clean and convincing. Dial down the vocals and you get a pretty decent karaoke track. Similarly, if you’re practising your axe, dial out the guitar and you have a blank canvas to fill with your own mastery. The drums are mixed in with the bass and other instruments such as keys and horns, so removal is not as clean or precise. I found that winding that dial just below halfway was enough to substantially remove the drums while still retaining some of the bass. Songs where the bass and kick are tightly synchronised are naturally harder to work with.

Trying my stem testing songs, I got varying results:

For Toto’s Africa, a full instrumental, beat-heavy song, it was virtually impossible to dial out the drums and percussion. Dialling the “Others” channel back to zero eliminated the drums, but also much of the overall arrangement, resulting in a track that was not really playable.
The Shadows’ Apache, where the snare and rhythm guitar are tightly synched, ‘stemmed’ reasonably well and, for the most part, produced a 70% drumless track without too much overall loss, when Others was dialled back.
Elle King’s Ex’s & Oh’s: This song has a lot of floor tom synched tightly with the bass guitar. In order to dial out the drums, we effectively muted the distinctive bass riff as well, creating a very thin rendition – almost passable for practice, but nothing beyond that.
The Beatles’ When I’m Sixty-Four: Although the arrangement is quite sparse, I found it very difficult to dial out the brush drum part without losing a substantial part of the orchestration – horns and keys. So, I’d rate this one a narrow fail.
Santana’s Smooth: This busy, percussion-heavy track with many instruments layered over each other also proved challenging for the AI stem separation. The guitar and vocal removal worked perfectly, but the drums were just too enmeshed in the overall mix. So, again, dialling out the drums almost killed everything else.

So, is it good enough for practice? Overall, it was able to create recognisable playalongs – but always with some drums bleeding into the mix. The drum reduction was probably enough for about half of the use cases in a practice environment.

But what it lacked in clarity, it made up for in immediacy, avoiding the need to upload the song, wait for stemming to finish and then to arm the player with the resulting tracks. BandBox was virtually instantaneous, but when you hit stop on the backing track, you still get a few seconds of music, demonstrating that the audio is delayed during AI analysis and stem processing. The real engineering achievement is running that process in parallel with live inputs so that there’s no perceptible latency.

Bottom line

I should temper my conclusions by stressing that the BandBox is not a dedicated e-drum amp. That said, it did a respectable job handling drum output from my VSTs via Bluetooth or through the aux channel.

The stem separation, even though it’s optimised for singing guitarists, can be tweaked to largely eliminate drums. And the real appeal here is that you can stream a song from Spotify and get an instant drumless track for practice — or even modest performance, although I wouldn’t be brave enough to wing it in public (but maybe that’s just me).

Speaking of public use, the BandBox runs on both mains power and battery, with an optional separate battery pack available. In reality, though, most of us need mains power to run our kit or e-drum controller, so the battery option is probably something we’ll rarely need — along with the tuner and guitar modelling.

As a practice amp, the BandBox exceeded my admittedly low expectations. It holds its own against entry-level dedicated offerings from Roland and Alesis, and Bluetooth backing track streaming is a significant advantage. The stem separation, while far from perfect for e-drummers, is another plus.

What I’d love to see is a dedicated e-drum version of this amp: one with boosted mids and, importantly, a fourth stem — drums. In theory, that last element might be the most complex to implement, but it’s fundamentally a software challenge, so it should be achievable. The major obstacle, I’d assume, is market size. The home guitarist population runs to millions globally; drummers are fewer; and e-drummers fewer still. But reviews like this one might just alert JBL to a market it hadn’t previously considered. You can help the campaign by contacting the company through its website or asking your local music shop.

Specifications

Output power: 135 W RMS

Frequency response: 50Hz–20kHz, –6dB

Speaker configuration: 6.5″ woofer, 2 x 25mm silk-dome tweeters

Bluetooth: 5.4

USB in/out: UAC PCM 48kHz/24-bit, two-channel

AUX and line input sensitivity: 370mV RMS

Mic input sensitivity: 20mV RMS

Instrument input sensitivity: 100mV

RMS Bluetooth and USB input sensitivity: –9dBFS

Headphone output: ¹/₈” Line output: ¼” stereo to secondary speaker

Battery: Lithium-ion, up to 10 hours / ~3 hours charge time (speaker off)