Review: JBL Synthesis HDI 3800

With a license to print concert tickets

The floor-standing JBL speakers should be approached with caution, because once you are hooked…

Published 3 August 2021 - 8:00 am
JBL Synthesis HDI 3800
Lasse Svendsen

They are large, but much smaller than the huge Synthesis speakers we tested earlier this year. Still, the slimmer speakers really pack a bite, that you will notice physically. Six eight-inch woofers with rigid aluminium diaphragms, feel like having a six-cylinder engine bolted to the chest, when playing loud.

In other words, they are not for the faint of heart, because even though the speakers like to play at moderate volumes, it is only when you crank up the volume that the fun begins.

With a height of 110 cm, they dominate the room visibly. But they are easier to place than you think, despite the fact that the bass reflex ports are located at the back, and they can easily be matched with a 60-watt amplifier.

The JBL Synthesis HDI 3800 is the flagship of the HDI series, which is the more decor-friendly variant of the huge studio speakers from JBL. There is an HDI 3600 also for those who do not have room for the 3800 model, and a relatively compact tripod model called HDI 1600. For those who like surround and cinema sound, there is also a 12-inch, 1000 W powerful subwoofer and a center speaker in same series.

We have not tried the HDI series in surround, but after the test of 3800, we do not doubt for a second that HDI in six channels plays tougher than most.

For a pair 3800 is able to push so much sound out into the room, that you get dizzy and dizzy, but it has not become possible without JBL’s engineers have squinted at the professional speakers, and the studio monitors.

The HDI series consists of a number of speakers, including a sub and a center speaker.

Compression tweeter

All models in the HDI series – except the subwoofer, have a variant of JBL’s HDI compression horn, High-Definition Imaging. Here is a 2410H-2 horn with a 25 mm v-shaped polymer element at the back, where the sound waves are dispersed from a horn whose geometry is shaped for a uniform frequency response in the high range.

Together with the v-shaped diaphragm, JBL has tried to dampen breakup under load, and reduce distortion and time slip.

HDI 2410H-2

Instead of two woofers and one midrange, JBL has chosen to use three woofers per speaker, but use one of them in a higher frequency range – 800 to 1800 Hz. It provides a more efficient speaker that delivers more energy in the midrange while keeping the distortion low.

The three 20 cm woofers use an aluminium-based Matrix-like cone that can withstand a lot of power. The one and a half inch voice coil has a long stroke, and is equipped with a flux ring that concentrates the magnetic field, and a copper ring that can withstand a lot of heat and energy without the element breaking up and distorting.

Black, glossy paint with hardened top coat as on a car paint.

Two and a half way construction

This 2.5-way speaker would fall apart like a cardboard box when you turn up the volume, had it not been strengthend and braced well enough. JBL says that is precisely why they have chosen curved cabinet sides. It gives a stiffer outer shell, than if the cabinet surfaces were just that, flat. Inside, there are vertical braces especially where the woofers are located, which absorb the energy from 3 x 8 inches at 100 dB+ sound pressure.

For these beasts play loud. Very loud. But at the same time they manage to hold the sound image together, that is, if you have chosen the right amplifier.

Just forget the data, they are admittedly relatively sensitive at 92 dB, but that does not mean that the random old 30 W NAD amplifier from the 80’s is a good match. Even the powerful Hegel H120 had problems with the control when it was pressed on the 3800.

The amplifier of 60 W, played superbly to a certain point, after which it was not so easy to control the six woofers with the same tight grip. A switch to the far more potent H590, solved the problem. THEN things really took off.

Two pairs of terminals for bi-wire, or bi-amping.

Careful with the dental fillings

It was when James Blake’s Limit To Your Love thundered into the room that I felt my jaw vibrate. By then, the swaying deep bass had already crept into the spinal cord, and I thought the sight became a little blurry. When the drumstick fell on the snare drum, I had to turn down the volume.

Then I felt that the tooth fillings were cracking.

But bass is not the only thing that is tough with a pair of HDI 3800. It is also how they manage to play music so loud, and at the same time with steel control, without the sound image breaking up. One of the reasons is of course a thorough and solid construction, but JBL has chosen to let the bass fall off (-6 dB @ 37 Hz) below 40 Hz so that the woofers manage to play as optimally as possible.

Deep bass fans need to add a subwoofer, but as the example with James Blake shows, it is not really necessary.

The rest of the frequency range is reproduced with the same steel control as the bass. I have heard more neutral and correct piano sound, and strings are not the favorite instrument here either, but look at Grant Green’s Green Street, and you get semi-acoustic jazz that automatically dims the lighting in the room, and it is not the sound of a pint being tapped into the background, I hear, believe me?

Here they are really at home. The swing beats from the speakers, and the round guitar sound gets a lovely warm, plump sound where you can hear how well the bassist treats the standing bass without making an effort.
Seratones Fear sucks you against the speakers, the vocal harmony is beautifully rendered, and the room is filled with a massive punch, which never sounds hard or woolly.

The even harder Devil Worm from Ola Kvernberg’s album “Steamdome II”, gives me a sensational feeling of being at a live concert, where the bass and drums fight for attention in an intense soundscape full of details. You hear everything. For the JBLs are also transparent in the way that they let through more shades than a pair of Klipsch RF7 III, or B&W 702 S2 Signature can handle.

After another amplifier change, this time to the Devialet Expert Pro 250, Keith Jarrett’s trio recordings got a little more air and the soundscape stretched further back in the room. It gave more room for the musicians’ instruments, and showed that the JBL speakers are not just about dynamics and control. They tackle finesse too. What about Luciano Pavarotti? Or the mezzo-sound of Cecilia Bartoli? Right here, Devialet proved to be the best choice. The vocal sound shone more with the French amplifier, and the strings got a little more warmth and depth, which suited both the music and the speakers well.

HDI 3800 in gray oak veneer.


The closest you get to finding a direct competitor to the HDI 3800 is the Klipsch RF-7 III, which is a rugged speaker with an enormous sound pressure – and two 25 cm woofers that you feel on the body. It may have even a little more energy in the bass, but is not as refined and balanced as the JBL speaker, still definitely a fantastic fun speaker that is worth considering. The more elaborate cabinets on a pair of Sonus faber Sonetto V, will probably appeal to many, and here the sound is even better balanced with more warmth and glow. Dynaudio Evoke 50 and the aforementioned Bowers & Wilkins 702 S2 Signature, are two other options, which are not as hard-hitting, but slimmer options that are easier to place.


The JBL Synthesis HDI 3800 is the decor-friendly version of JBL’s professional speakers, and offers very much of the same features. A hard-hitting and powerful bass, with enormous dynamics and the ability to play both crazy loud and cleanly at the same time. They still tower well in the room, but can be delivered in three finishes with fine furniture quality, and look good as eye-catchers in a large living room. But it is when you turn up the volume that you understand why the HDI 3800 is so good. It is in fact one of the most useful speakers in the class, and one of the few that can give you a real feeling of being at a concert at home in your own living room.

JBL Synthesis HDI 3800

We think

Plays loud and clear, with a power you rarely experience the like of. Not as easy to drive as you may think. Physically large, and the deep bass is subdued.

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