ESB Audio 5.028 — 5000 Series 1.1"/28 mm Soft Dome Tweeter (pair)

ESB Audio 5.028 — 5000 Series 1.1"/28 mm Soft Dome Tweeter (pair)

The 5.028 is the 28 mm tweeter of the ESB 5000 Series, sold as a pair. It is a 4-ohm driver handling 110 W continuous and 220 W peak, with a recommended amplifier range of 40 to 150 W RMS.

The dome is a carbon fibre reinforced polymer matrix composite — not silk. That is a different design choice from ESB's 9000 Series and it produces a different driver, so it is worth stating plainly rather than letting the category label stand in for it.

The 28 mm Voice Coil

ESB's reasoning here is explicit, and it is the kind of trade-off worth understanding.

A 25 mm voice coil is the common size and it is light, which helps high-frequency extension. A 32 mm coil handles far more power but carries more mass. ESB specifies 28 mm as the compromise — enough coil to take 110 W continuously, little enough mass to stay linear well past the audible band.

The coil is wound on an aluminium former, which conducts heat out of the coil rather than letting it accumulate. Power handling in a tweeter is a thermal problem before it is anything else.

Motor and Ventilation

An oversized neodymium magnet drives the dome, with the metal parts of the magnet structure designed through FEM analysis to concentrate flux around the voice coil and keep it linear across the coil's full excursion. The pole cup is CNC machined from a solid piece of ultra-low-carbon steel.

Ventilation comes through a large opening in the bottom of the motor, protected by a filter with calibrated holes. That vent does something specific and useful: it lowers the impedance peak at the driver's resonance, which makes the tweeter easier for a passive crossover to work with. A tall impedance peak near resonance is exactly what makes passive networks behave unpredictably close to the crossover point, and reducing it is a design decision that pays off in a passive system.

Body and Damping

The body is 7000-series aluminium alloy and brass, machined entirely by CNC. ESB's stated reason is rigidity with near-zero tolerances — consistency between units, and a structure that does not contribute vibration or resonance of its own. The finishing ring is CNC-machined aluminium alloy.

Beneath the dome, dB Cloth damping material absorbs residual resonances. That extends usable response downward and reduces harmonic distortion, which is why this tweeter can be crossed as low as 1.2 kHz behind a steep filter.

A removable grille protects the dome.

System Application

ESB publishes the usable band against filter slope, and it is the most practical part of the datasheet:

• 1.2 kHz – 25 kHz with 48 dB/oct high-pass
• 1.6 kHz – 25 kHz with 24 dB/oct high-pass
• 2 kHz – 25 kHz with 12 dB/oct high-pass

The steeper the filter, the lower the tweeter can safely play. Behind the passive 5.6K2 CX, which is a 12 dB/oct network crossing at 2.1 kHz, the driver is being used exactly at its rated limit — that crossover point was chosen against this table, not arbitrarily.

In a three-way it sits above the 5.050 or above the 5.UMA's midrange section, crossed at 3.6 kHz by the 5.6K3 CX. With a DSP running 48 dB/oct slopes, 1.2 kHz becomes available and the midrange's job gets easier.

Installation Considerations

The tweeter is 51 mm across the flange and roughly 11 mm deep, which makes A-pillar, sail panel, and custom pod mounting straightforward.

Aiming matters more than the mount. A tweeter fired straight across the cabin at the opposite window puts a strong early reflection into the listening position; one aimed toward the listener, or deliberately across at a shallow angle to balance the near and far sides, gives a more stable image. This is worth experimenting with before the pillars are finished.

Never run it without a high-pass filter, and set that filter to the slope table above. A tweeter is destroyed by low frequencies, not by high ones — and it is destroyed quickly.

Specifications

• Type: component tweeter
• Nominal diameter: 1.1" / 28 mm
• Dome: carbon fibre reinforced polymer matrix composite
• Nominal impedance: 4Ω (Re 3.5Ω)
• Continuous power handling: 110W · Peak: 220W
• Recommended amplifier power: 40–150W RMS
• Sensitivity: 91.0 dB @ 1W/1m · 94.0 dB @ 2.83V/1m
• Free air resonance (Fs): 710 Hz
• Qes 1.73 · Qms 1.95 · Qts 0.91
• Voice coil: 28 mm, aluminium former
• Magnet: oversized neodymium
• Body: CNC-machined 7000 aluminium alloy and brass
• Flange diameter: 51 mm · Depth: approx. 11 mm
• Sold as: pair

HF Audio Perspective

Two things separate this tweeter from the price bracket it sits in.

The first is the vented motor. Lowering the impedance peak at resonance sounds like a footnote, but it is what allows a passive crossover to behave predictably near the crossover point — and it is why the 5.6K2 CX can cross at 2.1 kHz with a 12 dB/oct slope without the response wandering. Most tweeters at this level leave the installer to work around that peak.

The second is that ESB publishes the bandwidth against slope instead of quoting a single optimistic number. That table tells you what the driver will actually do behind the filter you are actually using, which is more useful than a frequency response specification measured under conditions nobody installs in.

On voicing, we will stay out of it. The composite dome is a different engineering approach from the silk domes higher in the ESB range, and which one suits a given system is a matter of the rest of the build and the listener. What we can say is that this driver is rated, filtered, and documented honestly — and that is what makes it straightforward to design around.