The first Gradient speakers

Gradient 1.0 - a loudspeaker with controlled directivity

Based on the research findings from the early 80s, Jorma Salmi began developing the first commercial product for Gradient.

The stated design objectives were as follows:

Minimizing early reflections relative to direct sound
Maximizing the time gap between early reflections and direct sound
Achieving flat free-field and power response curves
Ensuring low distortion
Providing a wide listening area
Delivering sufficient acoustic power

After two years of experimenting with prototypes, a model (1.0) was developed that not only met these objectives but also featured a neat construction and an economical price.

The hidden factor

Gradient's primary design principle was the control of directivity. This meant that minimal early reflections would reach the listener, allowing for a frequency response that was as flat and even as possible. Controlled directivity also ensured that the frequency response at the listener's ear height in the horizontal plane remained consistent over a wide area. As a result, the frequency response curve measured at 45 degrees off-axis was almost identical to that on-axis. Few speakers achieved such excellent results. The Gradient 1.0 speakers provided an extensive good listening area, with minimal early reflections, resulting in clear and pure sound quality. The spatial quality of the recording was faithfully reproduced.

Most importantly, the acoustics of the room in which you listened had less impact on sound reproduction with Gradient speakers compared to ordinary speakers. While it was not particularly remarkable to design speakers that sounded good in heavily damped rooms with dead acoustics, it was much more challenging to create a speaker that sounded good in any room.

Minimization of early reflections in the mid-frequency range

According to research, early reflections are most detrimental in the mid-frequency range. Directivity can be achieved in various ways, such as using a mechanical horn structure in front of the drive unit or by leveraging the speaker's physical properties. Gradient employed the latter method. Directivity in the mid-range was ingeniously achieved using a 30 cm dynamic drive unit, tilted backward, to handle the mid-frequencies. Since the unit was open, it also radiated sound to the rear. The technical term for this is a "first-order bi-directional gradient radiator," from which the brand name Gradient is derived. By using an open drive unit, the resonances of a speaker cabinet and reflections caused by its edges were avoided.

Treble reproduction through controlled line source

Treble sound reproduction was handled by a line source consisting of four drive units. The effective length of the line source was electronically shortened, with all four units handling the lower treble frequencies and only one handling the highest. This allowed for controlled directivity in the desired manner. This column of tweeters covered frequencies up to the upper limit of hearing and was also free from disruptive reflections caused by cabinet edges.

Enhancing bass response with floor-coupled design

Bass reproduction always depends on the placement of the speakers in relation to the room boundaries (floors, ceiling, and walls). Proximity to these surfaces tends to increase bass levels. This should be considered when designing speakers. If they are designed to the standards set in an anechoic chamber (i.e., bass level equal to midrange and treble), the bass frequencies may be reproduced too powerfully at the listener's position, making the speaker sound boomy and fatiguing the listener.

Gradient had positioned the bass driver facing the bottom of the bass enclosure, which operated on the bass reflex principle.

Since the woofer was almost in contact with the floor, the difference between the direct and reflected sound was small relative to the wavelength (at 50Hz, it was 7m). The reflection caused by the floor could therefore be fully utilized. In practice, the material of the floor surface rarely affected bass reproduction. The sensitivity of the low-frequency unit was set so that a Gradient 1.0 speaker placed on the floor produced an even-sounding bass in a living room setting.

Gradient 1.0: a new era in speaker design

Gradient 1.0 was, in many ways, a completely new type of speaker in terms of its operating principle. The model was followed by versions 1.1, 1.2, and 1.3 with minor changes. Simultaneously, models 2.0 through 2.3 with larger bass enclosures were produced, as well as the intermediate model 3.0. The last Gradient 1.3 was manufactured in 1997.

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