Short answer: the Brane X. It ranks #4 of 97 large speakers by sound quality, rated 4.6/5, at $500. The Marshall Kilburn III ranks #41, rated 3.8/5, at $379.99, $120.01 cheaper, not enough of a saving to outweigh the sound-quality gap.
The Brane X is the better-sounding, deeper-bass choice. The Brane X pairs a dedicated RAD subwoofer with two midrange drivers and two tweeters to achieve extraordinary low bass for a 7.7 lbs (3.5 kg) portable: its measured -10dB extension is 31Hz. Its bass reaches about 31Hz before falling 10dB, against 45Hz for the Marshall Kilburn III. It is rated IP57 against IP54 for the Marshall Kilburn III. It supports aptX HD Bluetooth, which the Marshall Kilburn III lacks. The catch: The front-facing design has only moderate dispersion, so sound changes noticeably off to the sides or behind it.
The Marshall Kilburn III is the longer-running choice. Spacious soundstage with broad stereo dispersion from Marshall’s True Stereophonic multi-driver layout, delivering warm, room-filling sound with 45Hz bass extension. It is rated for 50 hours of battery against 12 for the Brane X. It has an adjustable EQ, which the Brane X lacks. Watch for: Noticeable dips in the midrange compromise frequency response neutrality, making vocals and acoustic instruments sound somewhat recessed or muffled compared to more linear competitors like the JBL Xtreme 4 unless the bass dial is dialed back.
Buy the Brane X. It is rated higher for sound quality, and saving $120.01 with the Marshall Kilburn III does not make up for the sound-quality gap.
Looking for alternatives? See the complete Portable Bluetooth rankings.
Specifications Side By Side
| Brane X | Marshall Kilburn III | |
|---|---|---|
| Price | $500 | $379.99 |
| Ranked | #4 of 97 in Large Size Portable Bluetooth Speakers | #41 of 97 in Large Size Portable Bluetooth Speakers |
| Aux Input | Yes | Yes |
| Aux Latency | 295ms default, 33ms with aux pass-through | - |
| Bass Extension (-10dB) | 31Hz | 45Hz |
| Battery Life | 12 hours (Manufacturer specified) | 50 hours (Manufacturer specified) |
| Bluetooth | Yes | Yes |
| Bluetooth Codecs | aptX HD, aptX, AAC, SBC | SBC, AAC |
| IP Rating | IP57 | IP54 |
| Bluetooth Latency | 100ms | - |
| Maximum SPL | 106dB (measured by Alan Ross Reviews) | 91dB |
| Party Mode | Yes (Brane app, up to 8 speakers) | Yes (Auracast) |
| Power Input | AC Power brick | USB-C |
| Stereo | Yes | Yes |
| Omnidirectional | No | No |
| TWS | Yes | Yes |
| Weight | 7.7 lbs (3.5 kg) | 6.3 lbs (2.85 kg) |
| Wi-Fi | Yes | - |
| App | No | Yes |
| Built-in Microphone | Yes | No |
| Voice Assistants | Amazon Alexa | - |
| EQ | No | Yes |
| Power Bank | No | Yes |
| Dimensions | 9.3” x 7” x 6.1” (236 x 178 x 155 mm) | 10.7” x 5.9” x 6.7” (272 x 150 x 170 mm) |
| Drivers | 2x 2.5” midrange, 2x 0.75” tweeters + 6.5”x9” subwoofer | 1x 4” woofer + 2x 2” full-range drivers |
| Frequency Response | 30Hz - 20kHz (Manufacturer specified) | 45Hz - 20kHz |
| Amplifier Power | 200W | 50W |
| Digital Aux Input | No | No |
| Bluetooth Version | 5.1 | 5.3 |
| Strap | No | Yes (built-in strap) |
Related Speaker Comparisons
How Brane X compares with other leading options:
- Brane X vs Vifa Helsinki
- Brane X vs JBL Xtreme 5
- Brane X vs Tribit Stormbox Lava
- Brane X vs Minirig 4 with subwoofer
- Brane X vs Minirig 3 with subwoofer
Prices on this page were last checked October 2, 2026 at 10:18 PM UTC. Product prices and availability are accurate as of that date/time and are subject to change; the price and availability shown on Amazon at the time of purchase will apply to the purchase of this product.
As an eBay Partner, we may be compensated if you make a purchase.
The Two Speakers In Full
Brane X: $500 Amazon eBay
Pros: The Brane X pairs a dedicated RAD subwoofer with two midrange drivers and two tweeters to achieve extraordinary low bass for a 3.5kg portable: its measured -10dB extension is 31Hz. Independent testing finds it loud, with well-balanced mids, a smooth treble balance and useful bass-level controls; Wi-Fi, AirPlay, Alexa, quality Bluetooth codecs and low-latency aux pass-through make it unusually versatile. The medium bass-boost setting is the most balanced. Measured bass extension of 31Hz (-10dB).
Cons: The front-facing design has only moderate dispersion, so sound changes noticeably off to the sides or behind it. Bass response shifts at maximum volume, the default aux mode has very high latency, and some listeners find the upper register edgy or need EQ to achieve their preferred balance. Its claimed 12-hour runtime and premium cost make it more of a compact high-end system than a carefree all-day speaker. The upper bass is boosted around 120Hz, and the robot voice announcements can be annoying.
Full Brane X review and specifications →
| Amplifier Power | 200W |
|---|---|
| App | No |
| Aux Input | Yes |
| Aux Latency | 295ms default, 33ms with aux pass-through |
| Bass Extension (-10dB) | 31Hz |
| Battery Life | 12 hours (Manufacturer specified) |
| Bluetooth | Yes |
| Bluetooth Codecs | aptX HD, aptX, AAC, SBC |
| Bluetooth Latency | 100ms |
| Bluetooth Version | 5.1 |
| Built-in Microphone | Yes |
| Digital Aux Input | No |
| Dimensions | 9.3” x 7” x 6.1” (236 x 178 x 155 mm) |
| Drivers | 2x 2.5” midrange, 2x 0.75” tweeters + 6.5”x9” subwoofer |
| EQ | No |
| Frequency Response | 30Hz - 20kHz (Manufacturer specified) |
| IP Rating | IP57 |
| Maximum SPL | 106dB (measured by Alan Ross Reviews) |
| Omnidirectional | No |
| Party Mode | Yes (Brane app, up to 8 speakers) |
| Power Bank | No |
| Power Input | AC Power brick |
| Stereo | Yes |
| Strap | No |
| TWS | Yes |
| Voice Assistants | Amazon Alexa |
| Weight | 7.7 lbs (3.5 kg) |
| Wi-Fi | Yes |
- Links
- Reviews, Comparisons and Sound Samples
- Alan Ross Reviews: This speaker left me shocked! Brane X, they said it defies the laws of physics! More from alanrossreviews →
- Alan Ross Reviews: Brane X vs JBL Xtreme 5: Maximum Bass, No Mercy
- Alan Ross Reviews: JBL Boombox 4 HUMILIATES Brane X?! Ultimate Bass Battle!
- Alan Ross Reviews: Minirig 2.1 or the Brane X or the Harman Kardon Go Play 3?
- mark: Brane X Speaker Review 2
- mark: Brane X Speaker Review
- Head-to-Head Comparisons
Marshall Kilburn III: $379.99 Amazon eBay
Older model: the Marshall Kilburn II (ranked lower, rated 3.8/5).
Pros: Spacious soundstage with broad stereo dispersion from Marshall’s True Stereophonic multi-driver layout, delivering warm, room-filling sound with 45Hz bass extension. Independent physical bass and treble dials allow quick tonal adjustments on the fly, backed by app-based EQ and placement compensation. Battery life is outstanding at up to 50+ hours with USB-C power-bank charging, IP54 splash resistance, 3.5mm aux input, and Bluetooth 5.3 with Auracast broadcast support. Measured bass extension of 45Hz (-10dB).
Cons: Noticeable dips in the midrange compromise frequency response neutrality, making vocals and acoustic instruments sound somewhat recessed or muffled compared to more linear competitors like the JBL Xtreme 4 unless the bass dial is dialed back. Kilburn II retains slightly punchier perceived loudness at maximum volume due to a more aggressive V-shaped contour. At 2.85 kg with only IP54 splash resistance, it is heavy and cannot withstand water immersion. Lacks a built-in microphone and LDAC codec support.
Full Marshall Kilburn III review and specifications →
| Amplifier Power | 50W |
|---|---|
| App | Yes |
| Aux Input | Yes |
| Bass Extension (-10dB) | 45Hz |
| Battery Life | 50 hours (Manufacturer specified) |
| Bluetooth | Yes |
| Bluetooth Codecs | SBC, AAC |
| Bluetooth Version | 5.3 |
| Built-in Microphone | No |
| Digital Aux Input | No |
| Dimensions | 10.7” x 5.9” x 6.7” (272 x 150 x 170 mm) |
| Drivers | 1x 4” woofer + 2x 2” full-range drivers |
| EQ | Yes |
| Frequency Response | 45Hz - 20kHz |
| IP Rating | IP54 |
| Maximum SPL | 91dB |
| Omnidirectional | No |
| Party Mode | Yes (Auracast) |
| Power Bank | Yes |
| Power Input | USB-C |
| Stereo | Yes |
| Strap | Yes (built-in strap) |
| TWS | Yes |
| Weight | 6.3 lbs (2.85 kg) |
- Links
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
- Marshall Kilburn III vs Marshall Kilburn II
- Marshall Kilburn III vs JBL Xtreme 4
- Marshall Kilburn III vs Ultimate Ears Everboom
- Marshall Kilburn III vs W-King T9
- Marshall Kilburn III vs Marshall Middleton
- Marshall Kilburn III vs Devialet Mania
- Marshall Kilburn III vs Marshall Middleton II
- Marshall Kilburn III vs Sony ULT Field 5
- See all 31 comparisons