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Brian Steele wrote:Some background reading...
1. Good results can be achieved with a flare radius that's equal to the *length* of the vent, but if designing for HIGH output levels, flaring should actually be kept pretty low.
2. BOTH entrances to the vent should be flared. Flaring only one makes the port asymmetric and can increase distortion and cone offset at high playback levels.
Another thing about using long slot vents and aero vents in a box is that the textbook calculations for determining the correct length tend to off a bit, and sometimes by a lot. That means that you need to confirm that you hit the target Fb and adjust the length of the vent accordingly if you didn't (or just live with the difference). It's easier to trim an aero vent than it is to trim a slot vent .
Finally, another problem with large vents are the organ-pipe resonances that they generate. These are a function of the vent's length, so the longer the vent, the lower the resonances. Typical rule of thumb is that the effective passband of the sub is one octave below the first resonance, so if that resonance is at 100 Hz, the effective passband of the sub reaches up to only 50 Hz.
All of this can be avoided by avoiding the whole box with large vent scenario and model and build an MLTL instead that will take up the same amount of space, and offset the driver in the MLTL to address the first vent resonance. The example I provided above basically hit the target Fb and the "vent" is large enough to keep compression down to less than 2dB at Fb at peak output levels. The driver is offset in the MLTL to reduce the impact of the first vent resonance at 200 Hz, pushing the effective upper limit of the design from 100 Hz to 150 Hz (the next vent resonance is at 300 Hz).
ruffneck_12 wrote:Weys boy Brian type all that and can't get a thanks too self
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