frame
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 problem.

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.