The minima in the excursion plots should closely correlate with the impedance minima's. They may not match exactly, but they should be very very close.
When you say the Fb's were off from the plots, how did you measure?
The simulation program uses round ports located away from cabinet walls.
Slot ports on cabinet walls tune lower.
The difference between 70 and 80 Hz is only about 1/6 octave, the sub is going to crash a little lower than it would "as designed".
Ether way, it is covering only an octave with steep rolloff above and below, which is why it sounds "boomy".
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also, inductance plays a large role in these box designs. If your inductance in the program is not what it really is, it can cause nasty peaks.
I would have done
Vr=63L
Vf=15L
Fr=30Hz
Ff=72Hz
Good from about 30Hz - 110Hz.
The tricky part is the tuning. As was said, slot ports that use enclosure walls as the port-walls tune lower. In one particular enclosure I have here, the end correction k=5.6, which means ports will tune about 10% lower than what calculations spit out. Correlates some-what with what you seem to have found---your lower tuning is ~3Hz off from 37, and your upper tuning is ~8Hz off (obviously I'm fudging the numbers to make myself look smart
)
I would have done
Vr=63L
Vf=15L
Fr=30Hz
Ff=72Hz
Good from about 30Hz - 110Hz.
The tricky part is the tuning. As was said, slot ports that use enclosure walls as the port-walls tune lower. In one particular enclosure I have here, the end correction k=5.6, which means ports will tune about 10% lower than what calculations spit out. Correlates some-what with what you seem to have found---your lower tuning is ~3Hz off from 37, and your upper tuning is ~8Hz off (obviously I'm fudging the numbers to make myself look smart
)
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Woow, no, I did not measure a thing yet! I was still talking about the simulated plots! The ones BassBoxPro Generated..
And i tried to take the lower tuning of slot ports in account when designing the box, but I have not measured it!!!
I was just wondering why the simulated cone displacement minima is the same as the simulated FB, But not the same as the simulated impedance minima.
It will take some time before I get the chance of actually measuring the impedance plots.
And i tried to take the lower tuning of slot ports in account when designing the box, but I have not measured it!!!
I was just wondering why the simulated cone displacement minima is the same as the simulated FB, But not the same as the simulated impedance minima.
It will take some time before I get the chance of actually measuring the impedance plots.
Ok, I tried to simulate a TH with hornresp, I have about the same size (177L), about the same -3dB and efficiency is 2-4dB lower then the bandpass sub, assuming BassBoxPro simulates in 4 Pi too... And excursion is about double... Am I doing something wrong or something? I'm 100% noob with hornresp, I made this with some tutorial from the AVSforum.
An externally hosted image should be here but it was not working when we last tested it.
Ok, I tried to simulate a TH with hornresp, I have about the same size (177L), about the same -3dB and efficiency is 2-4dB lower then the bandpass sub, assuming BassBoxPro simulates in 4 Pi too... And excursion is about double... Am I doing something wrong or something? I'm 100% noob with hornresp, I made this with some tutorial from the AVSforum.
An externally hosted image should be here but it was not working when we last tested it.
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