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Originally Posted by jCube The AR 65V, a flared port, has an internal dia of 2.4" |
Sure, but what about the pipe behind it that you have to pick up locally?
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Originally Posted by jCube On what basis does one decide upon the tuning frequency? I know it depends on the box volume. But assuming I can build a box of any volume and a port of any length/diameter, how do I decide upon a particular tuning frequency? |
No, the other way around. The box volume is calculated from the other parameters, including the frequency to which you want the box to be tuned to.
That tuning frequency depends on what driver you pick up (sub characteristics, incl. Fs) and how low you want to hear the notes. Sometimes you don't want to go down to the 1st octave, if the kind of music you hear doesn't have instruments that do.
Don't confuse it with the apparent 'goodness' of bass - not much is actually heard but felt (not everyone's ear 'listens' down to 20Hz) and that feeling is actually bolstered by sub and mid-bass drivers' ability to reproduce in a controlled manner the overtones (harmonics) of the lower notes. So, if you use a good sub and a bad mid-bass, the result would still be lacking. Bad drivers & systems make the harmonics linger around longer than required making the music sound "boomy" and "muddy".
The advantage of the bass-reflex (ported) enclosure is that the system mechanically boosts the output produced by the driver around the tuned frequency. But not that it can make 45Hz Fs driver sound like a 27Hz Fs driver.
So, rolling back to the start, first you select a driver (sub) based on what you need: Price, Loudness (electrical power handling AND driver sensitivity), size (depth), construction (frame, coils, ventilation etc.) and mech/elect parameters (depending on Q, some sound best in a sealed box, some in higher order like BR).
Follow LBM's process - he is doing it right now. He has been using IDQ divers in a ported box, and his system is SQL (he got 152.7dB of LOUD but accurate music). He is now revamping his bass system - and has just selected a driver.
Navin, B&T, Gunbir et al have written a lot on the forum regarding driver selection and influence of different parameters - search and read, that is the real Knowledge Base.