|Driver baskets may be constructed from various types
of metals depending on budget, and design goals, the most
usual solution is use of stamped steel or cast aluminum.
Expensiver speakers usually feature cast aluminum
baskets, though stamped steel baskets are not worse
solely because of production method. Steel baskets are
cheaper to manufacure and have some disadvantages if not
properly engineered . They must be designed with special
care so that the driver magnetic strength will not be
compromised by the baskets magnetic properties resulting
in a less powerful motor structure which will weaken
response time and increase overhang distortions. The most
critical disadvantage of steel baskets is unwanted
coloration in sound, which most frequently accour around
80Hz. Cast baskets do not suffer from the previously
mentioned disadvantages of steel baskets. In most cases,
this should not be an issue providing that the drivers
are properly designed and implemented. However it is
important to note the potential of this problem. If a
basket performs audible colourations, damping it with
something thick, inert and heavy should solve the
Frame can be screwed together as is the case with Yamamura drivers. To make a frame really cheap hollow metal rod or pressed steel but with some kind of dense and inert filler applied to frame.
The aerodinamics of a frame structure is mostly neglected. Technically, in an open baffle or ported enclosure the size and shape of the cutouts would make a difference in the sound because there is actual movement of the air mass behind the speaker as the cone moves. The air movement consists of a pressure waveform that changes with the frequency and intensity of the sound from the speaker. In a sealed enclosure the cutouts don't affect the sound as much because the waveform reaches a constant pressure or equilibrium and remains fairly constant. Of course, even closed back, or sealed cabinets have to leak a little. Over the past 30 years or so, most speaker designers haven't given much thought to the issue of designing basket cutouts because the necessary metal stamping and tooling for speaker baskets is very expensive. Therefore, a few different types have been essentially standardized for the industry. You'll notice that most speakers are either a 4 or 6 trapezoidal hole arrangement, and baskets from most manufacturers look about the same.