zero-two loudspeakers

This 2009 project started with the only FOSTEX FE166E full range driver and finished with two additional drivers - Morel MDT12 and Dayton Audio Euro series woofer. Any fan of a full range driver has to admit, that there is either a lack of high frequencies, or a lack of low frequencies. In most of the cases however, a single full range driver lacks both. Although the frequency range of such driver is limited, it is popular for several reasons (no phase shift, no crossover and other passive components in the signal path, often higher sensitivity, one point sound emission). On the other hand however, sooner or later, it becomes something that might start to bother. Whether it plays a Classical music, Jazz or a Hard Rock, the instruments that are recorded as being full, strong and deep sounding, should be that way also reproduced. This should be the main point of any loudspeaker design. The 6,5" Fostex was doing a fairly good job while tested as a single driver design, but after some time i felt that the sound was missing the message from the original recording. This was a turning point for adding the two new drivers. Since i wanted the full range Fostex to work for what it has been designed for, those two additional drivers were just the supporters of the missing frequency spectrum.

The full range driver got only a simple attenuation circuit (due to higher sensitivity). The Morel tweeter was set up for 12dB/oct. at 14kHz also with an attenuation circuit. The second order crossover was also used for the 7" woofer from Dayton Euro Series. With the crossover frequency computed for 85Hz, its purpose was to help the full range driver fill in the bottom part of the range. With some minor corrections in the crossover, the sound became more full- bodied. I should also mention, that the sound emitted from the Fostex was very directional. A relatively small change in listener's head in the right or left direction significantly influenced the stereo image. This was primarily caused by the listener's distance, so i would recommend to listen to horn drivers from a greater distance of at least 12 feet. The positioning of the loudspeakers is a whole another chapter - a long chapter.

As seen from the third image, the vibration control is also a crucial element of a serious listening. Steel spikes are used to improve the dampening factor between the loudspeakers and the rest of the environment. Standing on a granite, which has a high acoustic impedance, takes the resonance suppression even further. Underneath the granite is currently a quarter inch of cork that serves as a protection for the hard wood floor and at the same time dampens the resonances of the floor. The cabinet itself is divided into two chambers, one for the bass driver and one for the full range Fostex driver. The bass resonator is tuned up for 65Hz and is computed for the full range driver, since the original - one driver Fostex design, came with this recommendation. The loudspeakers have two pairs of terminals, so it is possible to use them without the Dayton bass woofer. The first image shows the internal synthetic dampening material used to suppress the internal standing waves and additional wooden bracing bars to stiffen the cabinet construction. ophichus@gmail.com