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During the design of the crossover network the acoustic, mechanical and electrical interactions of the high and low frequency sections
have been fully analysed. The crossover is therefore an integral part of the design of the system. The crossover network provides complex
equalisation in both amplitude and phase for each section and fully integrates the response at the crossover point. All components are
high precision, low-loss and thermally stable. A unique shunt element technique controls the motional impedance of the drive units.

All components in the crossover network are hard wired to eliminate unwanted metal-to-metal contact and ensure freedom from
vibration. The components are laid out to minimise inter component coupling and are placed well away from the driver magnetic field.
Specially selected components of the highest quality are used, such as Hovland polypropelene capacitors, non inductive thick film
resistors with extensive heat sinking, and very low loss laminated iron core inductors. Wiring is by Acrolink (99.9999% purity) copper,
having a large crystal structure and stable atomic arrangement.

High current switch blocks with gold-plated screw terminals permit user adjustment of high frequency sound radiation to suit differing
listening environments.

The complementary design of crossover and drive units means that the loudspeaker system as a whole behaves as a minimum phase
system over the audio band and therefore the acoustic sources of the high and low frequency sections are aligned in time and space to
ensure accurate reproduction of stereo images.

The Crossover Network

A Note on Auditory Perception

Our hearing mechanism locates natural sound sources with great accuracy by using the naturally occurring phase differences (or arrival
times) at middle frequencies, and intensity differences at higher frequencies, between each of our ears. Naturally occurring sounds pass
through the air to the ears at constant speed (345 metres/second or 1132 feet/second). All frequencies travel at the same speed and
therefore a frequency independent time delay is associated with the distances involved. (The familiar time delay between a flash of
lightning and the associated clap of thunder is an example).

Human hearing relies on the constant nature of the time delay with the intensity to locate natural sounds accurately. A pair of Tannoy
Prestige loudspeakers can uniquely reconstruct stereo images and provide excellent localisation of recorded sounds. The Tannoy Dual
Concentric™ principle ensures that the source of sound at high frequencies is on the same axis as the source of sound at low frequencies.

The careful design of crossover network complements the drive unit to provide a coincident sound source at frequencies where the
human ear derives phase information for localisation. The loudspeaker system exhibits a time delay response that is in essence independent
of reproduced frequencies. In addition, the amplitude (or intensity) response is linear, smooth and consistent. This provides the correct
intensity information to recreate the original sound stage.

The Westminster Royal SE Compound Horn Loudspeaker -

Technical description

A horn loudspeaker consists of an electrically driven diaphragm coupled to a horn shaped device. The horn increases the coupling
between the oscillating diaphragm and the listening environment by increasing the air loading presented to the diaphragm. Ordinary
direct radiating loudspeakers are relatively inefficient because the energy present in the moving diaphragm is not transmitted to the
air particles in the listening environment particularly efficiently.

The presence of a horn, loading the diaphragm, greatingly increases the resistive portion of the air load and more energy can be
transferred to the environment for a given diaphragm energy.

Conversely, for a given level of sound generated by a horn loaded diaphragm, the amplitude of movement of the diaphragm will be
lower than for the equivalent sound level generated by a direct radiating loudspeaker. Therefore the distortions present in the diaphragm
at larger amplitudes will be reduced further, because the diaphragm has a larger air load that has a higher resistive value and also because
the damping on the diaphragm will be greater. This results in a better transient performance.

The compound horn loudspeaker consists of a diaphragm with one side of the diaphragm coupled to a straight axis horn and the other
side coupled to a long folded horn.

The Westminster Royal SE cabinet generates both horns using a rigid network of 30 individual panels. The internal construction is
not easy to visualise.

Figure 5

shows a perspective view of the internal construction of the rear folded horn with the front straight axis

horn removed for clarity.

Figure 8

shows that although the drive unit is a two way system (low frequency cone, and high frequency compression unit) the total system

behaves as a three way loudspeaker with the lower crossover point, at 300 Hz, performed by the acoustical mechanism of the cabinet.

Figure 6

shows a developed section through the horn with the rear folded horn straightened out for clarity. This gives an acoustic

engineering model that can be used to describe how the compound horn operates.

Figure 7

shows the electrical analogue of the acoustic system shown in developed cross section.

Mms and Cms represent the moving mass and suspension compliance of the drive unit respectively. Zf, represents the acoustic load
impedance presented to the driver by the front horn and Zr the impedance presented by the rear horn. The volume of the air between
the driver and the throat of the rear horn behaves as an acoustical compliance (capacitance) shown in the network as Rms in parallel
with Zr.

Perspective view of Westminster Royal SE

cabinet with front horn section removed

to show the internal construction of the

horn development comprising the

rear folded horn. The arrows show

the direction of radiation from the

drive unit to the listening environment.

At 300 Hz both horns radiating -6 dB

Below 300 Hz rear horn radiates

( low resistance, high reactance)

(power disspitaes in )

FIG. 5