Posted by Wayne Parham [ 70.234.130.147 ] on January 09, 2007 at 21:34:17:
In Reply to: Pi Studio One Tower posted by FredT on January 09, 2007 at 17:40:37:
I really like your speaker, Fred.
I thought about adding it to the line, as we discussed. But I think it's just as well that we just let people know your version is around - that's kind of how the Professional Series three π is too. This all started out as hobby stuff anyway, and it isn't too hard to make the speaker with existing kit parts or whatever.
Another hybrid I wanted to toss around is a dual woofer version of your speaker. Might do this with the tower two π as well, but in that case, the larger enclosure volume is really useful for additional damping. The characteristics of the Alpha 8 make it suitable for very small boxes, so you don't really need the enclosure volume. Adding another woofer is no trouble at all in the space you have.
What is gained when adding a second woofer is elimitation of floor bounce amplitude notch in the midbass, where distance to the floor is 1/4λ. This gives a smoother response curve, overall.
When you measure a tower speaker or a bookshelf speaker on a stand, what you see is a dip in response at the frequency where woofer distance from the ground is 1/4λ and a peak where distance is 1/2λ. There is sometimes a slight rise where distance is 1/8λ and a slight dip where distance is 3/4λ, rising slightly again at 1λ. Above this, it tends to level off. Lay the speaker down on its side, woofer closer to the ground, and response is smooth. But move the woofer up away from the ground more than a couple of feet, and floor bounce starts making these notches and peaks.
By adding a second woofer, you can fill in the dips and average the response. This is one of the characteristics I like about your arrays, they tend to average out the response curve and remove the problem of floor bounce. By using a second woofer, this can be accomplished. Moving the woofer lower will do it too, but that hurts midrange, if the driver is acting as a midwoofer. The Alpha drivers are inexpensive enough that adding a second to eliminate floor bounce is a good option.
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