GRF Enclosures (from Tannoy sales information)

The GRF enclosures provide a compound expanding source, an exclusive feature first introduced in the Tannoy Autograph enclosure. The effect of this is that the wave front area varies with frequency, giving an outstanding illusion of realism to both solo and orchestral music. In addition, the system has all of the well known advantages of horn loading (eg: excellent bass radiation and transient response, but none of the spacial distribution defects associated with conventional horns or multispeaker systems.

The low frequency diaphragm of the 15-inch Dual Concentric Loudspeaker is rear horn loaded down to 30 Hz, while between 350 Hz and 1,000 Hz a new acoustic coupling device gives much improved front radiation. Above this frequency the non-directional horn loaded high frequency unit, which forms an integral part of the Dual Concentric Loudspeaker, takes over, serving to preserve the impression of loaction so necessary to ensure realistic reproduction of vocal and solo instrument music. The result of this entirely new form of horn loading is that, while large orchestral and choral works have a snese of spacious wave front, both chamber music and solo and vocal music possess that intimacy very necessary for full enjoyment.

The GRF enclosure is a fitting compliment to the 15-inch Dual Concentric Loudspeaker, when the highest standard of performance is required.

Technical Specification

Frequency Response: 30 Hz to 20,000 +/- 3dB

Power Handling: 50 Watts

Efficiency: 10% approx

Bass Horn Development: Effective loading down to 30Hz

Height: 46 inches
Depth: 26.5 inches
Max Width: 40 inches
Frontal Width: 23.5 inches

Finish: Sapele Mahogany, or Figured Walnut

Fabric: Vynair.

Corner GRF Design Plans (courtesy Alain Kobsch, France)

Drawing-1; Drawing-2; Drawing-3; Drawing-4.

Drawing-1 may be used as a cutting template if it is printed at full-scale. This template was kindly computer re-drawn by Alain Kobsch of France.
Above: The Tannoy corner-GRF horn speaker.

Rectangular GRF

The Rectangular GRF was introduced to simplify the accomodation of a pair of loudspeakers for stereo. The enclosure is designed to give similar performance to the corner version and the electrical characteristics are identical.

Height: 42.5 inches
Depth: 19 inches
Width: 23.5 inches

Rectangular GRF Design Plans:

These plans provide a reasonably complete information on how to make the Rectangular GRF enclosure, but I cannot attest to the accuracy or completeness of them as I have not used them "in anger". (Copy of plans kindly provided by Alain Kobsch, France):
Drawing-1; Drawing-2; Drawing-3.

See also the design plans for the Rectangular GRF as drawn by P. Stinson of Australia.


Tannoy Corner GRF (re-tinted from a
black and white original)


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