Roy #4

Roy 4 is a loudspeaker system built for a friend to appease aesthetic concerns over a previous pair of speakers, as well as to create a great pair of speakers for roughly $100. The major hallmark of this set is the fact that it uses two different similarly sized woofers in different chambers covering much of the frequency range; it is more or less a 2.5-way speaker.

Driver Selection

A Dayton 5.25 was reused in the woofer with a Peerless 5 added in the polypropylene woofer. These two woofers are in full range and then are rolled off with a low-pass filter. The Peerless is crossed off higher than the Dayton as it has a better high frequency response while the Dayton has a much better bass. Each woofer has its own chamber. The tweeter is a 1 inch Hi-Vi fabric dome tweeter chosen for its low distortion and workable frequency response.

Crossover Design

The crossover is interesting, and is certainly much more advanced than previous low budget efforts. A second order crossover was used on the woofers with the Dayton rolling off a little bit before the Peerles. For the tweeter, a third order filter was used to get a proper roll-off, as well as to account for the acoustic center offset between the tweeter and the woofers. The affect cannot be seen or heard, but it is still beneficial.

The graph to the right shows a very flat frequency up to roughly 1800Hz, then attenuates steadily until 3KHz, where it flattens once again at 4KHz. This was done in order to account for baffle step compensation. Essentially, the wavelength becomes longer than the width of the baffle, and the sound wave warps around the speaker while energy is lost in the room and is not directed at the listener. While some energy is reflected back to the listener, a better solution is to use as thin of a baffle as possible, as was done with these speakers with a 6 inch baffle. The simulations for baffle-step compensation are somewhat finicky and was adjusted for a decent tonal balance. This allowed for a warm tonal balance that could be appreciated with the poorest of music files, but could also be used for high quality items.