Free field frequency responses of the measured and the generalized loudspeaker (105 mm woofer, bass reflex port back)
In the upper section of the calculator the reverberation time within the listening room is calculated depending on the construction, the size, and the furnishings of the room. Based on the reverberation time, the selected loudspeaker’s frequency response is then calculated in the lower section of the calculator. The frequency response not only depends on the position of the loudspeaker but also on the listening position. The drawn arrow indicates the transfer path for which the frequency response is valid. The colored map shows at which positions a good low frequency response of the selected loudspeaker can be expected. This map is dependant on the listening position as well. In addition the total frequency response of four identical subwoofers can be calculated.
The calculator contains 37 generalized loudspeaker models derived from more than 650 real loudspeakers, which were measured in the labs of the journal Stereoplay. These generalized loudspeakers are described by their dimensions and the Thiele and Small parameters of their bass sources. The thin green lines in the picture on the left show, for example, the measured free field frequency response of 20 compact speakers with an effective diaphragm diameter of 105 ± 5 mm and a bass reflex port on the back side. The thick green line is the calculated frequency response of the corresponding generalized loudspeaker. The blue lines show the sound portions of each driver and bass reflex port.
In order to select the appropriate generalized loudspeaker, determine the effective diameter of your woofer, measured from the center of the rubber surround on the one side to the center of the rubber surround on the other side of the diaphragm. In the case of floorstanding speakers 2-way and 3-way systems are differentiated. If you have a 2½-way floorstanding speaker, select a 2-way system.
To change the position of the loudspeaker or listener, click on the appropriate symbol in the floor plan or section drawing of the room and then move it with the mouse.
Which is the ideal loudspeaker position? The general rule is: The smoother the frequency response, the more balanced the sound of the loudspeaker will be. For most loudspeakers this is the case when they are positioned as solitarily as possible within the room. If the low frequency transfer function shows excessive peaks usually an irritating booming develops at the corresponding frequencies. A sharp drop in the low frequency transfer function, however, is not critical. Only if the level remains low over a relatively broad range the listener will feel the bass to be too faint.
The calculator can help you to find good positions for the loudspeakers. Final adjustment, however, should always be based on listening tests.
The absorption values used in the calculator apply to individual absorber elements with the specified dimensions. If you want to use edge absorbers with other heights, you can enter fractional quantities. It is only important that the total lengths match. The same applies to the panel-shaped wall and ceiling elements. Make sure that the total areas are the same.
Melamine resin foam is available in light grey and white. Many manufacturers offer coloured fabric covers.
The wood wool lightweight panels are available in natural wood tone or dyed. Since the panels are dimensionally stable, they can be easily mounted with a wall or ceiling distance of a few centimetres. This leads to a slight improvement in absorption at low frequencies.
Polyester fibres are usually processed into wool. However, they are also offered in quite stable, felt-like panels. They are available in white, different shades of grey and many colours. Here, too, it makes sense to mount the relatively thin panels with a certain distance to the wall or ceiling.