Cotswold Sound (CS), which is based in the UK, designs, manufactures and distributes Balanced Mode Radiator (BMR) drive units internationally into the specialist loudspeaker market. Whilst the company has its own exclusive range of drive units called The Inventor Series, currently available ex-China, it also undertakes custom design for larger customers.

Most loudspeaker designers start by considering the loudspeaker as approximating to a "perfect point source", and then accepting the limitations of such an approximation for practical devices. Analysis shows that there is, in fact, an alternative prototype for a device that behaves like a "perfect point source", but it does not indicate an obvious embodiment. With this prototype in mind, a practical flat diaphragm loudspeaker has been developed, which has a substantially flat on-axis frequency response and an extended, smooth acoustic power response.

In the case of a modal object, the complete response may be considered as a sum of partial responses, each of which is related to an individual mode of that object. The on-axis pressure of any flat object is a sum of the "pistonic" response and the modal contributions. For the case of a free disc, the mean volume velocity of the non-pistonic modes is zero, so that they will not contribute to the on-axis response. By now applying an "ideal force" to this disc, we can turn it into an "ideal loudspeaker" with a flat on-axis response and an extended, smooth acoustic power response.

In the practical case, however, the force delivered always has mass associated with it. This mass at the drive point unbalances the mode shapes and perturbs both the pressure and power responses. However, by adding additional masses at prescribed positions, it is possible to recreate the mode shapes of the free disc and thereby restore the original response.