Foam or rubber surrounds?

The whole story, practical and technical: For B&O we have also manufactured a rubber surround next to a foam surround version (3 inch midrange). This is a very thin and light surround, and listening research has led to no difference. With woofers it is often a bit more precise.

There are brands and types such as Tannoy, Dynaudio, Vifa, etc. where the production is exactly manufactured with the same loudspeaker parts but where the foam is replaced by rubber.

For example, with the Dynaudio type surround SR192/2 where in later versions exactly the same parts are used, but the foam edge is replaced by a 192/2 rubber edge with exactly the same properties .. If a surround is replaced by a rubber surround it must be thin and often flexible. Especially with hi-fi speakers.

For speakers in cars, a rubber edge can be a solution. Warm, sunlight, smoke etc. are often seen as bad for foam surrounds.
The more technical story:

We have rubber surrounds, but they are less in demand compared to foam surrounds. A foam surround is an essential part of the speaker unit and it could sound completely different with a rubber surround instead of a foam surround. The advantage of rubber is that it does not decompose. This is partially true; however, rubber may dry out and/or harden.

The foam surrounds we offer are made of top-quality and are durable. The following text is a direct quote from the Dutch edition of the book ‘The Loudspeaker Design Cookbook‘ by Vance Dickason. This is not just any book, but a Bible among books used by designers of loudspeakers:

'For this reason the surround is an essential part of the cone construction, and also a part that in an important way is reponsible for the frequency-charateristics.'

'The surround can dampen membrane vibrations and refractions to the center of the membrane, affecting both the amplitude and the phase of resonance modes'.

Furthermore, when the speaker is designed, the mechanical mass MD is also determined by the weight of the surround. Rubber surrounds are a lot heavier than foam surrounds. In the calculation, the MD includes half the weight of the surround. For example, by another MD, the Fs = resonant frequency and other parameters also change, so that the original design can be lost.

If you want rubber edges that are as close as possible to the original, is the specialist in the professional repair and placing appropriate rubber surrounds.

© Copyright 2012 – Audiofriends – Fred Buist – All Right Reserved