Celestion 300 floorstander

Celestion 300 floorstander

hfnvintageThis slim design gives the standard advantages of transmission line bass loading but manages to beat the drawbacks, says Martin Colloms

New concepts are being launched at Celestion to convey its upmarket SL sequence into the Nineteen Nineties. The first instance, designed by Bob Smith, was the 100 [HFN Nov ’91] adopted now by the 300 reviewed right here. This is a £1000 floorstander that goals to convey improved bass extension, energy dealing with and superior dynamics to the style, whereas sensitivity stays under common at 84dB/1W. A exceptional facet of the 300 is its transmission line loading, a primary for Celestion, and developed with an unusually authoritative theoretical method, by the designer Martin Roberts.

Tall Story

The 100 sequence styling is spinoff of the SL sequence, with the unique positive horizontal ribbing of the entrance casting changed by fewer vertical grooves. The 300 seems for all of the world like a 100 perched on a positive mahogany veneered pillar-stand (different finishes embrace Black Oak and Walnut). It seems good with or with out the grille, although I most popular this left off for crucial listening. Two horizontal bars assist to guard the delicate alloy foil tweeter dome however certainly not do they preserve out inquisitive little fingers. More safety could be welcome in regular home environments.


On its carpet-piercing spikes, the 300 stands an imposing 985mm tall, is 210mm extensive and a substantial 326mm deep together with the moulded grille. A posh inside quantity of 47 litres is quoted for the 300 and this compares with the 12 litres of the outdated SL6S, 600 and 700 fashions. A most energy enter of 120W programme is specified, with an 8ohm rated impedance. Celestion additionally signifies a considerable bass extension with the –6dB restrict given as a low 26Hz, this taking it into the territory of small subwoofers.

On Point?

Pillar audio system such because the 300 are rising in popularity, since they obviate the necessity for a stand, with its attendant disadvantages. Rarely does a stand correctly complement a speaker, whereas questions stay regarding one of the best interface between stand and speaker; ought to this be factors, cones, mastic or felt? The stand represents a variable which the pillar speaker avoids. Meanwhile, electrical connection is by the use of gold-plated binding posts that may be bi-wired. There aren’t any fuses or different safety units.

The Technology

Fundamental to the Celestion 300 is the event of a transmission line which steers a course between ineffectiveness attributable to overdamping and over-activity attributable to secondary resonances which can be underdamped. An ideal transmission line is a construction that receives power with out reflection, conducting it down an outlined path which can inevitably embrace some loss.

For acoustic functions, when back-loading a bass driver, a transmission line needs to be lengthy in contrast with the bottom frequency of curiosity, say 20Hz. If of excessive absorption, the road might successfully terminate all of the power coming into it, with the outcome that the far finish of the road could also be open or closed with little impact on the general outcome.


Original pages from the Oct ’92 difficulty of HFN during which Martin Colloms took a deep dive into the design of the Celestion 300, the corporate’s first transmission line loudspeaker

In apply, finite-sized audio system require traces of finite dimensions, slightly lower than the 17m wavelength of 20Hz. In truth the road part within the Celestion 300 is 1.7m, which locations the quarter-wave pipemode resonance, the one which is in part with and reinforces the frontal output of the motive force, at 50Hz roughly. In principle, at frequencies decrease than 50Hz the road output falls progressively out of part and by 35Hz little output can be accessible. In apply, loading and line damping will increase the efficient mass within the pipe or line, the outcome being a reducing of the cut-off frequency to 30Hz.

Life for the system designer could be comparatively easy if the behaviour of the road was confined to simply the 1⁄4 wave mode. Unfortunately for the loudspeaker (although thankfully for musical devices primarily based on pipes or tubes), extra higher-order resonant modes are current. These are positioned roughly on the odd-order values, 3⁄4, 5⁄4 and seven⁄4, along with the prime 1⁄4 wave resonance. These additional modes add welcome color and character to an instrument, however from the point of view of the loudspeaker driving the road, this complicated behaviour will be seen as a non-uniform acoustic termination supplied by the entry to the road. The sequence of higher resonances may also embrace reactive elements, that’s, the acoustic equivalents {of electrical} inductance and capacitance.

Martin Roberts had researched an preliminary paper on transmission traces revealed in 1990 which explored varied fillings and timings. Later work has involved different methods for terminating the upper modes. Normally the pipe is stuffed with an absorptive materials. This should not be allowed to maneuver since such random movement is equal to lossy hysteresis and may have an effect on the transient efficiency within the bass in a nonlinear method. Roberts’ work signifies that line tapering has little impact on the higher modes whereas ample absorbency for his or her management additionally usually leads to extreme loss on the ‘elementary’ 1⁄4 wave mode.

Critical Load

Roberts’ work, which exploits the method taken by G Letts, issues the usage of a low-pass acoustic filter forward of the pipe and loaded by it, which terminates the motive force at increased frequencies. In {the electrical} analogy, that is an LC filter which, within the case of the 300 system, is fashioned by a stiffness part represented by an ‘growth’ chamber behind the motive force resulting in a pipe entrance that’s considerably smaller.

For Celestion, the precise proximity of the pipe entrance to the again of the motive force is exploited, giving a transparent differentiation within the lumped evaluation for the system, and this distinguishes it from the chamber entrance to a tapered line which is extra generally employed.

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November 21, 2023 at 10:29PM

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