ES-28N

SOUNDS YEAH!

Number three out of three.

TECHNOLOGIES

“All good things go by three”—a familiar German proverb, and a fitting way to welcome the newest member of the EPOS family. The ES‑28N is the third model in the current line‑up, and appropriately, it marks a bold step forward: a true 3‑way loudspeaker from a designer long celebrated for mastering the art of 2‑way systems, even with generously sized woofers.

So what changed his mind?

Experience.

After decades of refining 2‑way concepts, one insight became impossible to ignore: when you introduce two woofers into a system, a classic 2‑way architecture simply stops being the optimal solution.

Yes, there’s the well‑known D’Appolito configuration, with a tweeter sandwiched between two woofers. But to place the tweeter at the ideal listening height—around one meter—the cabinet would have to grow into an impractically tall tower. The alternative, placing both woofers below the tweeter, forces a 2.5‑way design, where one woofer fades out in the lower midrange while the other carries the rest of the midband. On paper, that seems elegant. In practice, it tilts the main radiation axis downward, making it difficult to control midrange energy and maintain a coherent soundstage.

So the question became obvious: Why compromise when you can evolve?

And that’s exactly what led to the ES‑28N. A clean, purposeful shift to a 3‑way architecture, unlocking better control, better balance, and a level of performance that simply isn’t achievable within the constraints of a 2‑way or 2.5‑way system.

The result is a loudspeaker that doesn’t just extend the EPOS philosophy—it elevates it.

Frequency Response:
below 30Hz – 25kHz (in room)

Average Impedance:
> 6 Ohm

Minimum Impedance:
3.9 Ohm @ 16kHz

Sensitivity:
86dB @ 2.823V / 1m

Distortion:
average below 0.2% THD @ 86dB between 100Hz and 10.000Hz

Crossover Frequency:
330 Hz, 2700 Hz 2nd order LKR and 4th order LKR

Bass Unit:
Two High Power 7“, 36 mm voice coil diameter, Hybrid Ferrite and Neodymium magnet, injection molded straight cone with Mica filling. Low hysteresis rubber surround.

Midrange unit:
5.25“ (130mm) midrange, 30mm voice coil diameter, Ferrite double magnet, Mica filled PP cone. Low Hysteresis rubber surround

HF Unit:
28 mm tweeter with Aluminum/Ceramic compound dome and no Ferrofluid

Dimensions:
1050 x 250 x 360 mm (HWD)

Weight:
35 kg

Finish:
Walnut, White semi matte, Black semi matte, Jade green

Cabinet:
Reflex loaded, damped Sandwich panels, one dimensional braces, Low Noise Port, Duo layer Frontpanel

Terminal:
Custom made Low Metal Mass 4 mm Banana terminal

In Germany we like to say, “All good things come in threes” — a proverb that fits perfectly here.

The new ES‑28N is the third model in the current EPOS series, and fittingly, it’s also a 3‑way loudspeaker. That’s a notable shift for a designer who has long been known for crafting 2‑way systems, even with large woofers. So what changed his mind?

Experience. A 2‑way layout simply isn’t ideal when you want to use two woofers. Yes, there’s the classic D’Appolito arrangement with a tweeter between two woofers but placing the tweeter at the correct height — roughly one meter — would turn the speaker into an oversized tower. Putting both woofers below the tweeter forces a 2.5‑way design, where one woofer drops out in the lower midrange while the other carries the rest up to the tweeter. In theory that works, but in practice the combined radiation axis of the woofers tilts downward, making it difficult to control midrange energy properly.

So the logical step was to go 3‑way — and that’s exactly what we did.

Jade green

White semi matte

Black semi matte

Walnut

Similar to ES-14N, the cabinet of ES-28N is slightly tilted to get better time alignment for the drivers. The two woofers sit in a Bass reflex compartment, carefully braced for low cabinet colouration. For the same reason, the whole cabinet is made from a sandwich construction with a layer of high-damping glue beside two MDF panels. The front plate is 50mm thick and made from two 10mm sandwich panels and a separate chambered MDF panel of 30mm. The midrange has its own compartment with a triangular backside to avoid reflections. The remaining part behind the tweeter takes the crossover, so the components are isolated from high sound pressure levels. The port tube opening is located on the bottom. That allows an eight-centimetre diameter port in a length that gives the lowest possible output of resonances from the cabinet and the highest maximum output of low frequencies. In addition, the port is equipped with pressure-equalizing holes in the middle to avoid the tube resonance of the port itself. The opening in the socket is big enough, so even in cases where the cabinet is standing on the floor without spikes, the bass performance is not compromised.

The 30cm long port tube output reached its maximum at the tuning frequency of the cabinet/driver combination, 30Hz. The graph shows the difference between a standard port and a version with the pressure-compensated EPOS design, which removes the double-sided open tube resonance by almost 10 dB. Thanks to the correct position in the design, the cabinet’s standing wave modes do not escape through the port tube.

When we started designing our third loudspeaker for EPOS, the question arose of how to choose the driver layout. Being well known for 2-way loudspeakers, the expectation was another 2-way design. However, in this case, we decided to take a different approach.

Why Not a 2-Way Design?
The design called for two woofers. Since the woofers are 7″, two of them arranged in parallel would create far too large an area (in height) to cross over to a tweeter at 2-3 kHz. A classic D’Appolito construction would have been possible, but the speaker cabinet would need to be very tall to keep the tweeter in the correct position.

Another common method to overcome this problem is a so-called 2.5-way design, removing the midband from one of the woofers (typically the lower one). However, this approach has a significant drawback: the radiation axis of such a layout no longer points toward the listener but tilts downward. The best response curve occurs below the listening position, resulting in lost energy in the upper midband at ear level and even more above.

Ultimately, a 3-way design was chosen. With the woofer from the ES-7N, we had an excellent starting point, and with only minor modifications, a midrange driver was ready to go.

The Challenges of a 3-Way Design
Every crossover in a loudspeaker presents a challenging task to achieve the right balance. You need a smooth on-axis response curve, and you need to ensure that the total energy radiated in the crossover region is at the correct level. This requires a carefully chosen topology, and in the case of the ES-28N, a modified LKR circuit is used.

Even more critical is the timing between the two woofers and the midrange—it must be perfect not only around the crossover frequency but also far below and above the crossover point. Tiny timing differences between the drivers are nearly impossible to measure, as they don’t clearly show up in frequency measurements. However, they can be heard, which resulted in a modified filter compared to a classic LKR topology.

The result is the balanced warmth of a 2-way speaker combined with the excellent transparency of the smaller midrange and the power of a twin woofer setup.

Technical Implementation
The crossover itself is housed in a separate enclosure behind the tweeter. Custom-made high-voltage capacitors, high-power inductors, and low-inductance resistors are used to voice the speakers to the desired sound character.

Impedance:

The response curve shows a falling character toward low frequencies from about 300Hz, the corner frequency of the so-called baffle step. The ES-28N is voiced slightly differently from classic designs, taking into account that the woofers are close to the floor. Together with a low tuning of 30Hz, a very deep and tight bottom end results. The impedance is compensated in the midband for better working with tube amplifiers.

Distortion:

The distortion curves, measured at 86dB SPL show an average level of below 0.2% between 100Hz and 10kHz.

The two 7“ woofers share the magnet system and basket with ES-14N but use a straight cone instead of a curved cone. A straight cone is the best solution for the bottom end. A large inverted dustup makes the cone even stiffer for fast and powerful bass. The magnet uses aluminium demodulation rings to stabilise the inductance of the voice coil, so there is no modulation of the crossover, low harmonic distortion, and low intermodulation. The coil is 36mm in diameter and 18mm long. The coil former is made from non-conductive Epoxy/Glassfiber material to avoid Eddy Current.

The midrange is based on the design of the ES-7N woofer – Mica-filled polypropylene cone material made with injection moulding. A low hysteresis rubber surround and a Nomex high-temperature capable spider ensure the suspension is linear with good control of higher excursions. The 30mm voice coil with glass fibre/Epoxy former works in a magnet system with an impedance control ring to minimise distortion and intermodulation. A double magnet compensates the stray field and increases the force of the coil.

The tweeter is identical to the tweeter of the ES-14N and ES-7N, giving the new model the same top-end quality. It’s a 28mm voice coil on an Aluminum alloy, ceramic-coated dome with a powerful Ferrite magnet and optimized inter-cavity airflow. The tweeter does not use Ferrofluid in the gap for stable temperature and low compression.