JBL Synthesis 4429 studio monitors: The thrilling truth

Professional gear doesn’t often cross over successfully into the domestic hi-fi domain. But the JBL Synthesis monitors have a reputation for managing just that. The result is both realistic and musically thrilling

On paper, professional audio equipment – amplifiers and monitors in particular – should do a sterling job in a less taxing home entertainment environment. However, the priorities and applications of pro gear are significantly different.

For instance, professional speakers don’t have to blend into beautifully decorated home environments: they are workhorses, handsome in a form-follows-function kind of way, but with little in the way of lifestyle appeal.

They’re also meant to deliver an unwaveringly honest and accurate representation of the music across a broad bandwidth, often for hours on end, at above-average levels, while ensuring robust reliability.


The JBL Synthesis 4429 studio monitors fit that bill perfectly. Their large, slightly retro enclosures feature a compression horn system for tweeter and super tweeter, linked to a beefy woofer.

Both the 50 mm tweeter and 19mm super tweeter employ titanium diaphragms, while the bass driver features a 300 mm pure-pulp cone. The claimed frequency response extends from 40 Hz to 45 kHz (at -6 dB), and sensitivity is an efficient 91 dB.

The horn array occupies the upper part of the enclosure and uses a dense, mechanically inert material dubbed SonoGlass for the bi-radial horn. It’s flared to obviate resonance and boost overall clarity.

A removable cloth grille below the horn system hides a trademark blue-toned baffle and dual front-firing ports below the woofer, as well as adjustable attenuators for the HF and UHF frequencies. The rear panel has dual gold-plated binding posts, allowing bi-wiring.

The substantial enclosure is constructed from 25 mm MDF with real-wood veneer. At 635 mm tall and 400 mm wide, they’re larger than conventional standmount speakers, but not tall enough to be used in a floorstanding role.

As a result, they require custom-height stands – the review pair came with a pair of locally sourced and superbly made metal stands just 255 mm high, which places the super tweeter at around ear height. Total actual height of the JBL plus stand the comes to 890 mm.

Blue baffle is a JBL Synthesis monitor hallmark


For this review, the JBLs were placed in a free-standing location, well away from side and rear walls, and specifically avoiding corners, as these monitors are tonally generous, with a particular penchant for fast, powerful and full low frequencies.

They were toed in towards the listening position, but not completely, the idea being to find the optimum balance between image focus and generous staging. The review pair had already been run in, so there was no need for any extended break-in period.

Instead, I ran them just enough to get them settled in, hooked up to our Parasound Halo A21 power amp, partnered by a Primare PRE32/MM30 pre-amp. Source signals were provided by a Lumin D1 network streamer and a Marantz KI Pearl Lite CD/SACD deck, both running via a Bryston BDA-3 D/A converter.


From the outset, the US speaker duo delivered a full, big-hearted sound.  And yet, despite their tonal generosity, the 4429s never lost their agility or poise, always maintaining an athletic, succinct pace.

Initially, I felt that the monitors were adopting a slightly over-lavish approach, especially in the lower midrange, adding a certain warmth and richness to the sound, compared to more conventional hi-fi speakers.

However, it didn’t take long to get used to that full-range sound and to revel in the ability of the JBLs to do full justice to the complete tonal scope of the music. It added an underlying realism to the sound that made voices and instruments come vividly alive.

Attenuation controls allow performance to be customised

Equally important from a believability perspective was the fact that the JBLs did not allow the tonal richness to weigh them down. In fact, it was combination of tonal breadth, precise control and unbridled agility that allowed them to paint a sonic picture brimming with energy and enthusiasm.

And if you thought that those big boxes would get in the way of the music, think again: they managed to become almost completely invisible as point sources, with a level of transparency quite unexpected given their less than subtle visual presence.

Listening to Pat Metheny’s ‘Rise’, off the unusually titled Kin <–> set, the shimmering guitars were spread wide across the soundstage, interspersed with percussion and hand-claps, spotlighting the light-footed dexterity of the speakers.

They created an instant sense of dimension and presence, with the instruments occupying a real, identifiable position on the soundstage. The sheer speed of the speakers was showcased by the spectacular percussion, delivered with real punch and bite.

The 4429s expressed the joy and effervescence of the music with an zeal that was as mesmerising as it was infectious. The tenor sax tended towards brightness to the extent that I actually turned down the UHF by a quarter turn, which also  prevented cymbals from sounding too splashy..

This was more a measure of the recording’s balance that a shortcoming on the speakers’ part, and while purists might frown at such attenuation, it highlighted the additional versatility those controls provide, if used with care.

Metheny’s guitar sounded smooth and mellow, though, and the JBLs afforded it ample presence and timbre. The delivery was rich without sounding too abundant, allowing his flowing style to be interpreted beautifully.

The guitar provided a smooth, easy counterpoint to the spiky, incisive percussion. Staging was expansive, easily capturing the ambience of the recording, and allowing the music to escape the physical constraints of those bulky cabinets.

Indeed, you really do forget that they are there, becoming completely engaged by the music instead.

On the Mathias Landaeus Trio’s marvellous Opening set, the title track focuses on an expressive piano in close conversation with a sonorous upright bass, while the thoughtful percussion keeps careful, almost delicate pace.

The piano sounded vivid and intense, and the speakers had no trouble following the often intricate passages, delivering them with an almost liquid ease that was utterly enthralling.

Fine detail and nuances were presented with clarity and assurance, while always remaining perfectly integrated into the overall sonic picture, adding to a pervasive sense of presence and realism.

Indeed, there was something inherently visceral and exciting about the sound that was quite different from ‘normal’ hi-fi speakers. The JBLs had a compelling ability to make the music sound convincing, and, yes, authentic.

Compression horns look after midrange and treble

The Reference Recordings release of Benjamin Britten’s Young Person’s Guide To The Orchestra, performed by the Kansas City Symphony under Michael Stern’s baton, is a majestic rendering of this classical work – and the JBLs made the most of it.

They had the tonal scope, the timbre and the sheer pace to bring the full impact and muscle of the orchestra into the listening room.

The 4429s easily reflected the substantial, challenging dynamic swings of this performance, while capturing both the intensity and the delicacy of the music with a relaxed ease, but without blunting the music’s energy or passion.

The orchestra’s physical presence was potently rendered, so that individual instruments were instantly and easily identifiable across a vast and deep soundstage. Again, the tonal generosity of the JBLs stood them in good stead, ensuring that the orchestra’s full impact could be as much heard as felt. Yes sir, those big 300 mm woofers move a lot of air!

On the classic Doobie Brothers track ‘Black Water, from their Southbound album, it was the transparency and sparkle of this multi-layered recording that stood out: it rewards the resolution and the dynamics of a good system with a sonic feast.

Despite a busy arrangement with lots of musical action, the JBLs remained unflustered and precise, providing a full-hued, foot-tapping and detailed delivery. Again, expansive staging afforded the performance plenty of breathing space.

The big monitors precisely rendered the splendid fiddles, the boisterous bass and the bright guitars, but also showed off a talent for cohesion that ensured a seamless, immersive sound picture and a pervasive dimensionality.

The 4429s are studio monitors that make home hi-fi seem tame


The JBL Synthesis 4429 monitors are not for those who like their speakers slim, polite and unobtrusive. They are unashamedly bold and functional and ideally deserve a large room in which to ply their musical trade.

But what a great job they do of playing music, and making that music come alive, thanks to a real talent for impact, tonal generosity, expansive staging and, surprisingly for such big boxes, transparency.

There’s a vitality to their delivery that is quite different from the hi-fi norm, as if they have a better, more believable grasp of the original performance. And for all their pace and boisterous personality, they never lose sight of vital nuances and subtleties.

Linked to an equally high-quality source and amplification with ample headroom (despite their inherent efficiency) these studio monitors create a magically musical listening experience. – DEON SCHOEMAN

Makes the music come alive.
Not exactly a lifestyle speaker.

Enclosure type: Bass-reflex, front-ported
Drive units:
19mm titanium diaphragm ultra-high frequency compression driver
50 mm titanium diaphragm high-frequency compression driver
300 mm pure-pulp woofer
Bi-wiring: Yes
Impedance: 6 ohms nominal
Sensitivity: 91 dB (2,83V/1m)
Frequency response: 40 Hz – 45 kHz (-6 dB)
Power handling: 200 watts RMS
Dimensions (HxWxD): 635 x 400 x 300 mm
Weight: 32,3 kg each
R89 562 (pair)
HFX Systems.

Pat Metheny – Kin <–> (Nonesuch 44/16 WAV)
Mathias Landaeus Trio –  Opening (MA Recordings 176/24 WAV)
Benjamin Britten –  Young Person’s Guide To The Orchestra – Kansas City Symphony/Michael Stern (Reference Recordings 176/24 WAV)
Doobie Brothers – Southbound (Sony Music 44/24 FLAC)

Bryston BDA-3 DAC
Marantz SA-KI Pearl Lite CD/SACD deck
Lumin D1 network player
Primare PRE32/MM30 pre-amp
Parasound Halo A21 power amp
KEF R500 loudspeakers