ESB Audio 1.10SD4 — 1000 Series 10"/250 mm DVC 4+4Ω Shallow Subwoofer

ESB Audio 1.10SD4 — 1000 Series 10"/250 mm DVC 4+4Ω Shallow Subwoofer

The 1.10SD4 is a 10-inch dual voice coil subwoofer with a 4+4 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.

ESB publishes a recommended sealed enclosure for it, which makes this an unusually straightforward driver to build around.

What Shallow Actually Buys

The recommended box is 656 × 350 × 130 mm externally, holding 22 litres (0.78 ft³) net.

A 130 mm external depth is the number that matters. That fits under a rear seat, behind a seat back, or along the floor of a cargo area — places a conventional 10-inch enclosure at twice the depth simply cannot go. The cone area is unchanged: 327 cm² of radiating surface, the same as any 10-inch driver.

What is traded is excursion. One-way linear travel is 6.5 mm, which is modest for a subwoofer, and it is the direct consequence of a motor and suspension that have to fit in a shallow frame. This driver produces its output from cone area rather than from throw.

The 4+4 Ohm Coil, and How to Wire It

Dual voice coils exist so one driver can present different loads to different amplifiers. With 4+4 ohms:

• Parallel: 2 ohms — the usual choice, and where most compact mono amplifiers make their rated power
• Series: 8 ohms — useful when running two of these off one amplifier, or with an amplifier that is happier at a high impedance

Choose between the 1.10SD4 and the 1.10SD2 by what the amplifier is stable into, not by which sounds better. The SD2 is the 2+2 ohm version, giving 1 ohm parallel or 4 ohms series. Same chassis, same enclosure, same 6.5 mm of excursion — a different electrical match.

The SD4 has the stronger motor of the two at 8.65 N/A against the SD2's 6.98, and higher voice coil inductance at 0.87 mH.

Sealed by Design

A Qts of 0.61 with 23.5 litres of Vas and a free air resonance of 34.2 Hz describes a driver intended for a sealed box, and a small one.

Qts is the driver's total damping. Around 0.5 to 0.7, a driver works well in a modest sealed volume without needing the box to do much of the controlling — which is exactly the situation when the box has to be 130 mm deep and cannot be large. A driver with a Qts of 0.35 in 22 litres would sound thin and want twice the volume.

ESB's box specification is worth following rather than improvising on: 22 litres net, 18 mm material, and damping material filling roughly 75 percent of the volume. Thinner material than 18 mm compromises panel rigidity, and a flexing panel is output that turns into cabinet noise instead of bass.

System Application

The bass driver for a system where depth is the binding constraint — a vehicle with no boot to give up, a seat-back or under-seat installation, or a build that has to stay reversible.

It partners naturally with the 1000 Series front stage, the 1.6C coaxials or the 1.6K2X component system. Both of those are rated with an 80 Hz high-pass, which is where this driver should take over.

A compact mono amplifier in the 100–250 W RMS range at 2 ohms is the right partner. More power than 250 W is not useful here — 6.5 mm of excursion is the limit, and reaching it is a matter of the driver's mechanics rather than the amplifier's rating.

Installation Considerations

Build the recommended box, or build to its net volume. This is not a driver with room for enclosure experimentation — 22 litres sealed is what its parameters ask for.

Use 18 mm material. Bracing matters more in a shallow enclosure than a deep one, because the panels are large and flat relative to the volume they contain.

Fill about 75 percent of the internal volume with damping material. In a sealed box this makes the enclosure behave as though it were slightly larger, and it absorbs the internal reflections a shallow, wide box is prone to.

Set the amplifier's low-pass and subsonic filters before playing it hard. With 6.5 mm of travel, this driver reaches its mechanical limit before it reaches its thermal one.

Specifications

• Type: component subwoofer, dual voice coil
• Nominal diameter: 10" / 250 mm
• Nominal impedance: 4 + 4Ω (2Ω parallel / 8Ω series)
• Voice coil resistance (Re): 1.8Ω · Voice coil diameter: 2.1" / 53 mm
• Power handling: 250W continuous · 500W peak
• Recommended amplifier power: 100–250W RMS
• Free air resonance (Fs): 34.2 Hz
• Qes 0.69 · Qms 5.36 · Qts 0.61
• Vas: 23.5 litres · Mms: 137.8 g
• BL: 8.65 N/A · Sd: 327 cm²
• Voice coil inductance @ 1kHz: 0.87 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

A shallow subwoofer is an engineering compromise, and the honest thing is to say where the compromise falls rather than pretend there isn't one.

It falls on excursion. At 6.5 mm of linear travel this driver will not move the air a deep-motor 10-inch subwoofer will, and no amount of amplifier power changes that — past its mechanical limit, more power produces distortion, not output.

What it does have is full 10-inch cone area in a box 130 mm deep, which is the whole point. The alternative in most of these vehicles is not a better subwoofer; it is no subwoofer, or a boot full of enclosure the owner will resent within a month. A system with clean, controlled bass from under a seat is better than a system with no bass at all, and considerably better than one with a large box that never gets used because the space was needed.

The most valuable thing ESB provides here is the enclosure specification. Most drivers at this price leave the builder guessing at a volume; this one comes with dimensions, material thickness, and a damping figure. Build it as specified and the driver does what its parameters say it will.