Buckle-Meister said:
Just.....can't.....stop...................thinking ....
1. Depends on the manufacturer. With cheaper speakers, there is generally nothing in the way of isolation. As you spend more money, manufacturers start doing this with their cabinets. The ultimate in terms of isolation would be a design like the B&W Model Nautilus, where every driver has its own chamber.
2. Reflex I guess is somewhat of a misleading term, as there is no "flexing" going on. It's just a term to denote the movement of the air out of the port in reaction to the movement of the driver.
3. You got it. An
n-way design uses
n crossover points in its crossover topology. You would be somewhat correct. A "crossover point" refers to the specific frequency where the crossover is centered. But you are right in the sense that the three groups in your 3-way speaker are the tweeter, the mids, and the bass.
4. Porting a speaker allows the backwave of the driver to escape the cabinet, which increases sound output. Because the back pressure of the driver is also reduced, it can move more easily which translates to higher efficiency.
The fact that your speakers have three ports is just the design, there is no special name for it.
The air you feel coming out the back of the speaker is the air being pushed by the driver when it is in negative motion [wherin "positive motion" is defined as excursion in the direction away from the cabinet and "negative motion" is defined as the direction into the speaker cabinet]. When a speaker cone moves outward in the positive direction, it compresses the air molecules in front of it. This is called a "compression". The point where it is fully exterted and creating the highest amount of pressure is the peak of the sound wave [for simplicity we're discussing a pure sine wave]. The driver then moves in the negative direction. It keeps going past its equilibrium point [the equilibrium point is the place where the driver will come to rest when no forces are acting on it] to a negative excursion determined by the amplitude of the incident electrical signal. At this point, the driver has created a low-pressure area in the air in front of it. This low-pressure area is called a rarefaction. These two points, the compression and rarefaction, translate to the peaks and valleys on a two dimensional graph of a sine wave. So how does this affect your speaker? Well, you normally are only creating sound from the compressions and rarefactions produced by the front of the driver. When you add a port, a passive radiator, or in the case of the Linkwitz Orion remove the cabinet entirely, you gain the use of the compressions and rarefactions created by the back of the driver cone. This means you have effective two sources of sound waves, operating 180 degrees (or pi radians for you purist types) out of phase. This is the dipole effect. Now, your speakers are not true dipoles because they do not have exposed drivers to the rear. However, the utilization of the backwave is along the same lines as a dipole speaker (like the Orion, Martin Logan designs, or Magnepans).
Note: Bi-pole is not to be confused with Di-pole. A bi-polar speaker has two radiating elements that operate in-phase, meaning that when one exterts outward, the other does the same thing. A di-polar speaker operates 180 degrees out of phase, meaning that when one driver moves out, the other moves in.
And of course, a port on the back of your speaker will increase your bass because it will interact with the room (perhaps a wall) near your speakers and, if they're near a wall or in a corner, you will experience a room-gain.
Edit: Derr...forgot about th port tuning. Thanks Mr. Garcia.
