ESB Audio 1.10SD2 — 1000 Series 10"/250 mm DVC 2+2Ω Shallow Subwoofer

ESB Audio 1.10SD2 — 1000 Series 10"/250 mm DVC 2+2Ω Shallow Subwoofer

The 1.10SD2 is a 10-inch dual voice coil subwoofer with a 2+2 ohm coil configuration, built on a shallow chassis. It handles 250 W continuous and 500 W peak, with a recommended amplifier range of 100–250 W RMS.

It is the low-impedance version of the 1.10SD4. Same chassis, same enclosure requirement, same 6.5 mm of excursion — a different electrical match to the amplifier.

The 2+2 Ohm Coil, and Why You Would Choose It

The wiring options are what separate this from the SD4:

• Parallel: 1 ohm — for an amplifier that is genuinely 1-ohm stable and makes its rated power there
• Series: 4 ohms — a straightforward match for an amplifier rated at 4 ohms, or for running two drivers on one amplifier

That 4-ohm series option is the underrated one. Plenty of good compact mono amplifiers are specified at 4 and 2 ohms and are simply not happy at 1 ohm, and a single SD2 wired in series gives them exactly the load they want.

The decision between SD2 and SD4 is an amplifier question, not a performance question. Work out what your amplifier is stable into, then pick the driver that lands there — the SD4 gives 2 or 8 ohms, this one gives 1 or 4.

How It Differs From the SD4

The two are not electrically identical beyond the coil rating, and ESB publishes the differences:

• Free air resonance: 32.3 Hz, against 34.2 Hz for the SD4
• Moving mass: 143.9 g, against 137.8 g
• BL: 6.98 N/A, against 8.65 N/A
• Voice coil inductance: 0.54 mH, against 0.87 mH

The SD2 has the heavier moving assembly and the lower resonance; the SD4 has the stronger motor. Both arrive at the same Qts of 0.61 and the same enclosure requirement, which is the design intent — they are meant to behave alike in the box and differ only in what they present to the amplifier.

The lower inductance is a small point in the SD2's favour at the top of its range, where voice coil inductance is what starts rolling a subwoofer off.

What Shallow Buys

ESB's recommended sealed box is 656 × 350 × 130 mm externally, holding 22 litres (0.78 ft³) net.

The 130 mm depth is the whole argument. That goes under a rear seat, behind a seat back, or along a cargo floor, where a conventional 10-inch enclosure at twice the depth cannot. Cone area is undiminished at 327 cm².

The trade is excursion: 6.5 mm of one-way linear travel, which is modest and is the direct consequence of fitting a motor and suspension into a shallow frame. Output comes from cone area here, not from throw.

Sealed by Design

A Qts of 0.61 with 20.7 litres of Vas and a 32.3 Hz resonance is a sealed-box alignment for a small volume.

Qts describes the driver's own damping. In the 0.5 to 0.7 range a driver works properly in a modest sealed box without needing the enclosure to control it — which is exactly what is required when the box has to be 130 mm deep. A lower-Qts driver in 22 litres would sound thin and want a much larger volume.

Follow the enclosure specification rather than improvising: 22 litres net, 18 mm material, damping filling roughly 75 percent of the volume. Material thinner than 18 mm compromises panel rigidity, and a flexing panel converts output into cabinet noise.

System Application

A build where mounting depth is the binding constraint — no boot to surrender, an under-seat or seat-back location, or an installation that has to stay reversible.

It partners with the 1000 Series front stage, the 1.6C coaxials or the 1.6K2X component system, both of which are rated behind an 80 Hz high-pass — which is where this driver picks up.

A compact mono amplifier delivering 100–250 W RMS into whichever load you wire is the right partner. More than 250 W is not useful: 6.5 mm of travel is a mechanical limit, and an amplifier cannot argue with it.

Installation Considerations

Decide the wiring before ordering the amplifier, or the amplifier before ordering the driver. A 1-ohm parallel load on an amplifier that is not truly 1-ohm stable is the most common way this pairing goes wrong — the amplifier runs hot, then protects, and the symptom looks like a subwoofer fault.

Build to 22 litres net in 18 mm material, braced. Shallow enclosures have large flat panels relative to their volume, so bracing earns more here than in a deep box.

Fill about 75 percent of the internal volume with damping material.

Set the subsonic and low-pass filters before playing it hard. This driver reaches its mechanical limit before its thermal one.

Specifications

• Type: component subwoofer, dual voice coil
• Nominal diameter: 10" / 250 mm
• Nominal impedance: 2 + 2Ω (1Ω parallel / 4Ω series)
• Voice coil resistance (Re): 1.0Ω · Voice coil diameter: 2.1" / 53 mm
• Power handling: 250W continuous · 500W peak
• Recommended amplifier power: 100–250W RMS
• Free air resonance (Fs): 32.3 Hz
• Qes 0.69 · Qms 5.69 · Qts 0.61
• Vas: 20.7 litres · Mms: 143.9 g
• BL: 6.98 N/A · Sd: 327 cm²
• Voice coil inductance @ 1kHz: 0.54 mH
• One-way linear excursion (Xmax): 6.5 mm

Recommended sealed enclosure

• Net volume: 22 litres / 0.78 ft³
• External dimensions: 656 × 350 × 130 mm
• Material thickness: 18 mm (0.7") — less may compromise rigidity
• Damping: fill approximately 75% of the volume

HF Audio Perspective

The SD2 and SD4 get cross-shopped constantly, and the comparison people make is usually the wrong one.

They are not a good-better pair. They are the same driver offered in two electrical configurations so that it can be matched properly to whatever amplifier is already in the build, or affordable within it. Buying the SD2 and wiring it to 1 ohm on an amplifier that is only honestly 2-ohm stable produces a worse result than buying the SD4 and wiring it to 2 ohms — and the reverse is equally true.

Work out the amplifier first. Then this becomes a simple decision, and the driver performs to its specification either way.

On the shallow format itself: 6.5 mm of excursion is the honest limit, and it is the price of a 130 mm enclosure. For a vehicle where a conventional box was never going to be accepted, that is a trade worth making — and the published enclosure specification means the result is predictable rather than a guess.