Laboratory Jottings

Radio Record, Volume IV, Issue 34, 6 March 1931, Page 12

Laboratory Jottings

The Jensen Speaker

EESSRS. Fear and Company have sent a concert model Jensen Dysa numie Speaker for test. It is smale ler and lighter than the usual dynamie speaker, but it is nevertheless thoroughly efficient. A ten-inch cone is employed, and this is fastened to a supporting ring of moulded one-piece construction. The flexible material allows for ample movement and yet holds the cone firmly, The centring device is of a design which is robust enough to stand up to fairly hard, work without sagging to cause rattl The pot magnet has been reduced to yery small dimensions on account of the new material being used. The model we tested was worker directly from the A.C. mains, and used with a 280 Arcturus rectifier. THe concert model is designed for ordinary power output supplied by 245’s single or in push-pull or in the Loftin-White. It \ ‘Il supply an undistorted output suffcient for the average large room, and might even. be used in a very small hall, although it is not designed for this purpose, Our tests were carried out with the Loftin-White amplifier and constant frequency records, the speaker being used behind a fairly large baffle. We found that the response from 75 to 7000 cycles was fairly constantslightly more so than our standard. At the extremes there was a fairly sharp cut-off, but actually we could get notes of 45 and 8000 cycles through fairly clearly. Tested on ordinary records the added brilliance due te the strong treble reproduction was apparent. It is very pleasing after to find that this speaker reproduces music with some semblance of upper register fidelity. The speaker when used with a standard amplifier, such as we have previously mentioned can be. relied upon to give really first-class reproduction. This speaker has been used in quite a number of the American and British receivers we have tested.