The boxspringbett test (box spring bed) is a term still used to describe a bed that is formed of two major parts. The piece below the mattress would originally have been a wooden frame covered in fabric that housed a series of springs that lend support to the mattress. The thinking behind this particular design is that with two independent elasticated systems the lower element would take stress away by absorbing some of the shock from the mattress giving a greater softness to its feel.
The term is outdated now as improvements in how a mattress is constructed have given less need for the substructure to be sprung. With the introduction of better technology via the use of innovations such as memory foam there is less need for the lower element of the bed to absorb shock through a series of springs. It is more of a foundation but its function is similar whether it contains springs or not. This foundation is there not only to assist the mattress as a shock absorber but it will also give a flat and consistent surface for the mattress making it nice and even to lie down on. For convenience the bed is raised to a height that is much easier to get into and get out of. Beds that have mattresses with less or no support are considerably harder to transfer in and out of.
In choosing what style of bed that you need there are a few basic options. Firstly and most basically, the mattress can be put on the floor. This sounds somewhat primitive but it will suit some individuals. Back sufferers, those that do not need require a lot of sleep or those of a more humble disposition may feel that a hard bed will be just what they need. It will keep the back rigid but for most sleepers it is too stiff and harsh on the body in general so is most likely to cause sleep depravity.
Secondly, just up from placing your mattress on the floor is the Japanese style futon. This is a multi-function bed and sofa with a wooden frame and padded mattress usually topped off with a quilt. These are space and money savers but not the most comfortable sleep you will ever have. The wood is rigid and often the mattress is simply stuffed with no additional spring system; just a little further up from sleeping on the floor.
The next option is to have a foundation under the mattress but in a lower position and often using the support of struts or slats. This is known as a platform bed and is most commonly found in Europe. It will not possess the height gained with a full foundation bed but does offer some support from the mattress and it raises it off the ground so should, in theory be a more forgiving support for the mattress and better comfort for the user. These are not as robust as the stronger foundation style beds.
The box spring bed is generally regarded as the best bed design to use for a number of reasons. It has a height advantage over other methods; the support given to the mattress gives much more room for a softer nights rest. Thirdly the flatness of the surface gives a much more even mattress to lay down on. There are styles available today that will even allow more movement and changes in angle by using motors to adjust the attitude of the foundation and improve the suitability for the user.
Like everything, there will come a time when your foundation bed will not feel as good as it once did. There are possibly areas of the bed that are not as resistant as they once were and consequently feel out of line with the rest of the mattress. It may be that the mattress is the issue or it may be that it is the box spring test that needs to be carried out. To test the lower component you should start by lying on that part having removed the mattress. Overt time the springs will not be as elastic as they once were when new. When depressed they will not reform to their original shape. They will sag and this will cause a depression in the surface of the support surface. Consequently this can have an effect on the mattress and ultimately in how the bed feels. If the box spring has failed the test it is time for a new bed, not just a new mattress.