Marshall Kilburn III vs JBL Xtreme 4: here's which Bluetooth speaker I'd spend my own money on

I've tested a lot of Bluetooth speakers during my time here at TechRadar – everything from mini audio companions to colossal boombox-style models. But so far, two of my favorite models sit somewhere in the middle of that – they're portable, yet decently bulky units that are ideal for gatherings, parties, or personal listening.

The speakers in question are the Marshall Kilburn III and the JBL Xtreme 4. Both of these have blown me away with wonderful sound quality, a high standard of build, and plenty of flashy features.

But if you're in the market for one of the best Bluetooth speakers, which one of these should you buy? Well, it's not all too easy to pick a winner – but I've tried my hardest to pick my champion. So, let's take a look at what sets these models apart, and ultimately, which model I'd spend my own money on.

Marshall Kilburn III vs JBL Xtreme 4: price and availability

The Kilburn III released in May 2025, almost seven years after its predecessor, the Marshall Kilburn II. With a list price of $379 / £299 / AU$599, it comes in at $80 / £50 / AU$100 more than its predecessor at the point of its launch. But that price does reflect a host of major improvements, including superior waterproofing, playtime, and acoustics. The Kilburn III is available in either Black & Brass or Cream.

Meanwhile, the JBL Xtreme 4 is a little older, having first released in March 2024. Despite carrying a list price of $379.95 / £329.99 / AU$499.95, you’ll regularly find it for less. After a quick search, I spotted it going for less than $280 / £240 / AU$380. Like the Kilburn III, JBL’s speaker is available in multiple colorways – there’s black, blue, and camo.

Marshall Kilburn III vs JBL Xtreme 4: specs

Marshall Kilburn III vs JBL Xtreme 4: features

Both of these Bluetooth speakers are packed with tons of smart feature goodness. Each have the usual good stuff – multi-point connectivity, fast-pairing, and the ability to charge external devices. But there’s so much more to discover in each model’s respective companion app.

For instance, the Kilburn III offers placement compensation, enabling you to optimize the speaker’s sound relative to its position in a room. That’s especially useful if the speaker is close to a wall or corner, say. This is something the Xtreme 4 does not offer, unfortunately.

Another thing the Kilburn III has that JBL skips on is a shortcut button. Using the Marshall companion app, you can pick two EQ calibrations to switch between using the speaker’s physical ‘M’ button. This lets you seamlessly switch between the standard tuning and a bass boosted mode, for example.

But the JBL does have a few tricks up its sleeve too. For example, there’s multi-speaker pairing, which you can access via the Xtreme 4 itself or the JBL Portable app. That’s something the Kilburn III left out. It's also got an option called PlayTime Boost, which extends the speaker’s maximum battery life by six hours, though it does disable EQ settings.

Still, the Kilburn III does have its own battery-related settings. It’s got preservation settings like an optional maximum charge cap, temperature reduction, and adaptive charging speed. It's also got a replaceable battery – something the Xtreme 4 boasts as well.

It's worth noting too, that the Kilburn III has a colossal battery life of 50 hours, which considerably outdoes the Xtreme 4’s very respectable 30 hours (with PlayTime Boost on). Both speakers also have Auracast and custom EQ options – but also skip on an inbuilt mic for hands-free calling and USB-C audio passthrough.

In spite of that, the Kilburn III does have an AUX port for wired listening – which combined with its placement compensation and superior battery life make it the stronger option features-wise – even though multi-speaker pairing was left out.

Marshall Kilburn III vs JBL Xtreme 4: sound quality

Right, there wasn’t a lot in it features-wise, and perhaps unsurprisingly, the same can be said in terms of sound quality. That’s because both of these Bluetooth speakers perform very well indeed in the audio department, offering highly tuneable, impactful, and clean sound. And that’s even without any fancy codecs like LDAC or aptX Adaptive.

Each model is crammed full of tech for an optimized listening experience. I already discussed the Kilburn III’s placement compensation feature, but there’s even more at play here. First of all, there’s dynamic loudness, which automatically adjusts bass, mids, and treble, ensuring that you don’t lose out on subtle details, even at high volumes.

On top of that, the Kilburn III makes use of Marshall’s ‘True Stereophonic’ sound, meaning you get a great listening experience from all angles. When using the speaker at our music testing space, I couldn’t detect any discernible blind spot, with full-sounding, expressive audio serviced to every part of the room.

But JBL didn’t come to play, it came to compete. As a result, the Xtreme 4 has some smart audio tech of its own – namely AI Sound Boost. Basically, this utilizes an AI algorithm to identify speaker movement and response in real-time, helping the Xtreme 4 to plate up “better and more powerful” sound, and reduce distortion at loud volumes. And during the testing process, I certainly found this to be very effective – there was little to no noticeable distortion, even when I cranked up the loudness real high.

Something I do like more about the Kilburn III is its sound signature out of the box. When listening to a track like Keep That Groove by Vitess, I was treated to heavy, pumping low-end output – though the bass never overwhelmed synths or vocals. But the Xtreme 4 left me wanting a bit in terms of low-end power: the thumping bass of Moloko’s I Want You, for instance, lacked the raw energy I’d expect from a speaker claiming to offer “next level massive” sound.

With a bit of tinkering in the JBL Portable app, though, my concerns were soon put to bed. With the right tuning, this thing is capable of seriously mighty, yet expertly balanced audio output. Using Custom EQ, Black Eye by Allie X was replicated excellently, with a responsive, emphatic interpretation of the track’s deep, rapid drum machine. Vocals were also given plenty of room to breathe, and crashing percussion never sounded harsh.

The Xtreme 4 is more powerful than the Kilburn III, making use of two 30W woofers and two 20W tweeters – as opposed to Marshall’s single 30W woofer and dual 10W full-range drivers. So, if sheer strength is what you’re after, it may well be the better pick. However, I have to say that I would edge the Kilburn III in terms of overall quality.

I’ve already mentioned its credentials as far as bass is concerned, making it more than capable of ramping up a party atmosphere. But beyond that, it provides a wide, engrossing soundstage and surprisingly strong instrument separation. When listening to Are You Gonna Go My Way by Lenny Kravitz, intertwining guitars sounded pleasantly forward, while fantastically positioned drums and piercing vocals tied up a head-banging listening experience.

Marshall Kilburn III vs JBL Xtreme 4: design

This tightly contested battle remains just that as we tip-toe into the realm of design. But while these speakers have shared a lot of strengths so far, this is where they diverge a bit.

See, the Marshall Kilburn III is a marvel in design, but predominantly because of its drop-dead gorgeous construction. I’m a huge fan of its amp-inspired look – a nod to Marshall’s rich history in the music space. Its tactile control knobs, red velvet-adorned handle, and golden details are also stand-out aspects, helping the Kilburn III to surpass its predecessor and, indeed, the JBL Xtreme 4, as far as appearances go.

Both is Black & Brass and Cream colorways perfectly complement its retro-style aesthetic too.

Meanwhile, the JBL Xtreme 4 goes in a slightly different direction, focusing on a rough and ready build rather than premium looks. It’s got a real tough feel about it, an outdoorsy style – especially in its camo colorway – but above all, excellent protection against the elements.

Specifically, JBL’s speaker is IP67-rated, meaning it’s well-shielded against dust, as well as water. It's so weather-resistant, in fact, that it can survive being submerged in up to a meter of water for 30 minutes. Not bad, eh? Combine that with a floatable build and this thing’s ready to go for pool parties, beach-sided bashes and, well, just about anything.

The same can’t quite be said about the Marshall Kilburn III. It’s only IP54-rated, which is a significant upgrade over the IPX2 Kilburn II, but means it can only withstand water splashes, rather than full on immersion. Previously, I quizzed Marshall on this, and it told me that the Kilburn III is intended to be more of an “interior statement piece”, due to models such as the IP67-rated Marshall Emberton III and Marshall Middleton occupying the rugged space.

Still, it's safe to say that the Xtreme 4 is the winner when it comes to durability. It's also lighter and has a shoulder strap, making it more portable overall.

Personally, though, I’m not a big fan of how it looks. Its pseudo-cylindrical build and color options don’t grab my attention – especially not compared to the Kilburn III. Still, I think it's only fair to call this category a tie, with each model excelling in their own distinct way.

Marshall Kilburn III vs JBL Xtreme 4: value

Let’s not beat around the bush. If you’re in the market for a cheap and cheerful Bluetooth speaker, neither of these models are going to cut it – they’re closer to the premium side of things.

But in this case, these speakers’ high price is indicative of high quality. With both models, you’re getting high-calibre audio for parties, outdoor gatherings, or personal listening. On top of that, both speakers have great build quality, plenty of features to have fun with, and plenty of playtime.

Now that the Xtreme 4 is regularly on sale, I’d argue that it's a good value pick. It doesn’t have the battery life or beauty of the Kilburn III, but it’s an awesome option if you’re the outdoorsy type or want a touch more power.

The Kilburn III is newer, so sales are few and far between, but honestly, I still think it’s well-priced, especially against rivals like the Bose SoundLink Max. The improvements on its predecessor are seismic, it supplies exemplary sonic performance, and that playtime is out of this world.

In the end, each of these offer plenty of bang for your buck. I’d probably give the Kilburn III a slight edge on value, due to its slightly superior audio and luxurious appearance, but there’s a lot to love about JBL’s rugged rival, especially with a price-cut.

Marshall Kilburn III vs JBL Xtreme 4: verdict

Ultimately, I think that both of these speakers remain worthy of my recommendation – but the model you pick will depend on what you need it for.

If you’re going to be using your flashy new audio companion outdoors – especially near a body of water – the additional power and durability of the Xtreme 4 could be your best bet.

Meanwhile, the Kilburn III is a fantastic statement piece, and offers up stunning build quality for the price. If you want a speaker for personal listening or indoor gatherings, I’d give it the edge, for its slightly superior audio performance.

But if I could only pick one of these in general, I’d also pick the Kilburn III – it just oozes class. I’m a big fan of its 50 hour battery life and room calibration capabilities – plus it did take the edge overall across our four categories.

Anyway, what’s your view? Do you own either of these speakers, and if so, what do you make of them? I’d love to hear your thoughts, so make sure to get chatting in the comments!

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