Yamaha v1.01 User Manual download pdf (Page 2)

Page 2/58 INTRODUCTION

GOING ONE STEP FURTHER IN LOW FREQUENCY CONTROL: RAY SUB TECHNOLOGY

Radiation control of low frequencies is hard to achieve due to wavelength being larger

than cabinet size. Consequently, most of current subwoofers available on the audio-

professional market are omnidirectional.

Drawbacks in using omnidirectional subwoofers are known by experienced engineers:

- Low Frequency sound pressure level is typically higher on stage than over the

audience; high-pass filters are mandatory in almost all microphones inputs to avoid

feedback from the microphones to the subwoofers. Moreover, gain from microphone

to speakers is highly limited due to that feedback (reinforcing a double-bass can be

an enormous challenge);

- Indoor environments typically have much higher reverberation time in the Low

Frequency range than in the mid and high Frequencies. This characteristic is

emphasized by the omnidirectional pattern of conventional subwoofers (all sound

engineers experienced kick drum lasting forever);

- Many outdoor shows occur nearby residential areas where noise constraints are very

restrictive; in such cases, low frequencies levels over the audience have to be

limited so that environment criterias are fulfilled (possibly leading to unacceptable

wideband limitations).

Gradient subwoofers provide an elegant solution to the above issues, based on a

technology that is a simple transposition to sound sources of what has been applied for

decades in microphones: radiated field derives from pressure differences generated

from two (or more) sources:

- Rear radiation is lowered by more than 12 dB, which benefits to stage as well as to

neighbours;

- Direct to reverberant ratio is increased by nearly 6 dB in the low frequency range

(which potentially gives back a kick drum its original “punch”).

However, there are efficiency limitations: gain in lower bandwidth is reduced when

sources become too close in relation to wavelength, and pattern control is limited in

upper bandwidth when both sources interfere destructively in the radiation axis.

Operating bandwidth were efficiency combines with pattern control is around 2 octaves.

Poor correlation between cabinet design and targeted specifications leads to two (and

eventually more) drivers in directional mode producing less energy than one driver in

omnidirectional mode, which is not acceptable for simple practical aspects such as

weight and volume.

It is now 5 years that NEXO has released its first gradient subwoofer – the CD12 -,

complemented since then with the CD18 and the GEO SUB. These have been quickly

adopted worldwide as standards, and are considered today as state of the art

subwoofers. This success is a consequence of proper cabinet design and optimized

definition of phase relations through sophisticated DSP algorithms leading to high

directional control and SPL output.

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Yamaha v1.01 User Manual Page 2