ESB Audio 1.6C — 1000 Series 6.5"/165 mm Coaxial Speaker (pair)

ESB Audio 1.6C — 1000 Series 6.5"/165 mm Coaxial Speaker (pair)

The 1.6C is a 6.5-inch two-way coaxial from ESB's 1000 Series — a paper cone woofer on a Y-25 ferrite motor with a 0.8"/20 mm silk dome tweeter on N-35 neodymium, mounted on the woofer's axis. 4 ohms, 90 W continuous and 180 W peak, covering 50 Hz to 20 kHz at 88 dB. Sold as a pair.

Read the Power Rating Carefully

ESB qualifies the 90 W and 180 W figures explicitly: they apply behind an 80 Hz high-pass filter at 12 dB/octave.

That is not fine print, it is an installation instruction. Run this driver full-range from a head unit with no filtering and the low frequencies it was never meant to reproduce will consume its excursion, and the power rating no longer applies. Set the high-pass and the driver takes what it is rated for.

Most factory head units apply no high-pass at all. If the system has no processor or amplifier providing one, that is worth knowing before deciding what this driver can be asked to do.

A Paper Cone, Chosen Rather Than Defaulted To

Paper is the oldest cone material and it remains in use at every price level for a reason: it has an unusually good stiffness-to-weight ratio and it self-damps — internal losses in the fibre absorb resonances rather than storing and releasing them the way a stiffer, less lossy material can.

Here it produces a 12.2 gram moving assembly, which is light for a 6.5-inch driver, on a Y-25 ferrite motor with a 25.5 mm voice coil.

The tweeter is a 20 mm silk dome on N-35 neodymium with a 20.4 mm voice coil. Silk is a soft dome material, and neodymium allows a small enough motor to sit on the woofer's axis without excessive obstruction.

The Qts of 0.99 Tells You Where This Belongs

This is the most useful number on the datasheet and the one that explains the driver's design.

A Qts near 1.0 describes a lightly damped driver — one that does not need an enclosure to control it. Put a low-Qts driver in a car door and it sounds thin, because a door is a large, leaky, poorly defined volume that provides almost no acoustic loading. A high-Qts driver in the same door produces useful bass, because it was designed to work without that loading.

With Vas of 11.2 litres and a free air resonance of 68.5 Hz, this driver is built for exactly one thing: a factory door opening. That is where coaxials go, and this one is engineered for it rather than adapted to it.

Coaxial Geometry

With the tweeter on the woofer's axis, both drivers radiate from the same point — so their outputs arrive at the listener at the same time from the same place. There is no path-length difference to correct, and no crossover region where two separately mounted drivers pull the image in different directions.

What you give up is the ability to aim the tweeter independently. In a factory door opening, where a separate tweeter would have nowhere sensible to go, that costs nothing.

System Application

A direct replacement for factory door speakers, running from a head unit or a modest amplifier. It is the simplest installation in the ESB range — one opening, one pair of wires, no crossover to mount.

Where the vehicle offers a separate tweeter location, the 1.6K2X is the alternative: the same 1000 Series approach as a component system with a 25 mm tweeter and a 12 dB/octave crossover, at 89 dB.

Pair with the 1.10SD2 or 1.10SD4 beneath it. The 80 Hz high-pass this driver is rated behind is precisely where a subwoofer should take over.

Installation Considerations

Check depth before ordering. The driver is 165 mm across the flange with a 144 mm mounting diameter and roughly 59 mm of depth — straightforward in most doors, but worth measuring against the window mechanism.

Set an 80 Hz high-pass at 12 dB/octave. This is the condition the power rating depends on.

Seal the driver to the door. A high-Qts driver working in a door is already relying on that door behaving as a rough enclosure — an unsealed mounting lets the rear output wrap around and cancel the front, which costs exactly the bass this driver was designed to produce.

Deaden the outer door skin if the budget allows. On an inexpensive driver this returns more than any component upgrade would.

Specifications

• Type: 2-way coaxial speaker
• Nominal diameter: 6.5" / 165 mm
• Woofer: paper cone, Y-25 ferrite magnet, 25.5 mm voice coil, Re 3.3Ω
• Tweeter: 0.8" / 20 mm silk dome, N-35 neodymium, 20.4 mm voice coil, Re 2.4Ω
• Nominal impedance: 4Ω
• Power handling: 90W continuous · 180W peak (behind an 80Hz 12dB/oct high-pass)
• Frequency response: 50 Hz – 20 kHz
• Sensitivity: 88.0 dB @ 1W/1m · 91.0 dB @ 2.83V/1m
• Free air resonance (Fs): 68.5 Hz
• Qes 1.22 · Qms 5.29 · Qts 0.99
• Vas: 11.2 litres · Mms: 12.2 g · Cms: 0.44 m/N
• Outer diameter: 165 mm · Mounting diameter: 144 mm · Depth: approx. 59 mm
• Sold as: pair

HF Audio Perspective

An inexpensive driver is worth judging by whether its engineering matches its job, and this one does.

The Qts of 0.99 is the evidence. Somebody chose that deliberately, because a coaxial in a factory door gets no useful help from its enclosure and needs to be damped by its own suspension instead. A driver with better-looking parameters on paper — a lower Qts, a stronger motor — would produce less bass in the same door. Specification sheets do not always reward the right answer.

Where it is genuinely limited is the 20 mm tweeter and the 20 kHz ceiling. If the vehicle has a tweeter location, the 1.6K2X's 25 mm dome and separate mounting is the better use of similar money.

Set the 80 Hz high-pass, seal the mounting, and put something underneath it for bass. Do those three things and this driver performs to its specification — which is all any driver can be asked to do.