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General speaker questions for audio and home theater.

RE: Acoustic suspension design speakers....

At first I assumed Wiki was wrong. Anyone can write for it and there is no real editing. But I did a quick look up and it is basically correct. You either missed the explanation or misread it. Infinite baffle and closed box mean the same thing. Acoustic suspension is a closed box with a very loose spider, so loose that it's control of the driver is poor. What fixes this is the air in the box. As a driver it's compressed pushing the driver back out and vice versa. If the air in the box is not a significant portion of the control of the woofer, it's closed box but not acoustic suspension. A good example is the old Bozak speakers which are closed box and not acoustic suspension. The large Advent was acoustic suspension.

The size of a woofer has NOTHING to do with the roll off point of any box speaker, ported included. In the case of closed box the relevant values are the free air resonance of the driver, the enclosure volume and the Qts, overall damping of the woofer. What is also missing in your reply is forgetting the Q of the speaker(box included) which determines the control of the woofer. This can be as important as the roll off point. If the Q is high the speaker is a boom box even if the roll off is low. You must design for the Q as well as bass extension.

Where the port on a reflex speaker has almost nothing to do with its response unless its very close to a wall. Port frequencies are so long they don't see the box at all. They wrap around the box and are omnidirectional. Port area only matters at high levels. You can design a big port or a small one to act essentially the same at low levels. But at high sound levels the port out put levels out simply because it can't play beyond a point and then it no longer reinforces the driver at these high levels. a large area port can reinforce up to higher levels.

Testing speakers has nothing to do with making them sound better in the bass. You simply need to know the relevant driver numbers, the type of box you want(closed or ported), the size of the box and what quality of bass(how well damped it is which is basically the Q of a closed box or what's called the alignment of a ported box). A good designer knows how he wants the damping. Then it's all mathematics and these days it's even simpler since a computer can do the math in minutes.

I could go on but this is merely a mini lesson and it's way too big a subject foe an Audio Asylum reply. But you have picked up a lot of stuff that really doesn't work.


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