I'm designing a box for an 8" woofer, when I see the air speed graphs in the ducts it's always absurd values and when I fix the duct it's more than a meter in size
What frequency do you recommend for this box? I tried co, 30, 35 and 43.49 Hz
Here are my woofer settings
I tried to make it work in a sealed box so the spl disparity between the sealed and ducted box really discouraged me, as the midrange has a very high spl in comparison.
What frequency do you recommend for this box? I tried co, 30, 35 and 43.49 Hz
Here are my woofer settings
I tried to make it work in a sealed box so the spl disparity between the sealed and ducted box really discouraged me, as the midrange has a very high spl in comparison.
the huge length results from your decision to use 4 vents, 6 cm diameter each.
Also, the woofer you chose has very low vas, which requires a long port (vent) for low tuning or alternatively a small port diameter. The datasheet suggests one port with 5 cm diameter, which I find rather small!
Increasing the total vent surface leads to longer vents (vent surface/length ratio remains more or less the same).
By the way it's much better to have one (big) vent only, to reduce chuffing noises.
If I remember correctly a rule of thumb for airspeed is max 10% of speed of sound, thus 34 m/s.
But I am currently investigating this matter and don't think air speed is a suitable parameter for vent dimensioning.
If you want to calculate the "ideal" vent diameter have a look at my suggested method:
https://www.diyaudio.com/community/...rbers-and-port-geometries.388264/post-7695977
You can also read about the benefits of port flanges/flares!
Also, the woofer you chose has very low vas, which requires a long port (vent) for low tuning or alternatively a small port diameter. The datasheet suggests one port with 5 cm diameter, which I find rather small!
Increasing the total vent surface leads to longer vents (vent surface/length ratio remains more or less the same).
By the way it's much better to have one (big) vent only, to reduce chuffing noises.
If I remember correctly a rule of thumb for airspeed is max 10% of speed of sound, thus 34 m/s.
But I am currently investigating this matter and don't think air speed is a suitable parameter for vent dimensioning.
If you want to calculate the "ideal" vent diameter have a look at my suggested method:
https://www.diyaudio.com/community/...rbers-and-port-geometries.388264/post-7695977
You can also read about the benefits of port flanges/flares!
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You'll want to find out why. Are you able to do something about the upper rolloff, it may be interfering?
I don't really understand this, but I can't do anything I don't think, just change the volume of the box and the size of the duct the resonant frequency of the box as well
Without details I'm concerned others won't be able to help.. but would it not be more direct for you to try using a different box simulator? Whether it's a data entry or a calculation discrepancy, it may come out in the wash..
I didn't expect this problem lol, learning as always, now the challenge is the woofer. On the other hand, which I never mentioned in this forum, I have a 63-liter box for a subwoofer. I don't know if I will be able to use it in the future, the idea was that I wouldn't, but I don't think I will have an exhaust.
I got a sealed 3-way gradient box with a 10-inch woofer and calculating the entire volume of the box is ±30 liters, I wouldn't think that my 3-way box with an 8-inch woofer would be bigger than that
Usually the sensitivity of the driver is not affected by the inside of the box (the outside of the box is another story, but these simulators do not consider the outside of the box). Filters can also change things.
This is why I'm surprised at your results. It is why a person can normally calculate sealed box volumes in their head and not expect any problems.
This is why I'm surprised at your results. It is why a person can normally calculate sealed box volumes in their head and not expect any problems.
I was looking here and the duct starts blowing when I use the full capacity of the woofer (30w which will be the maximum put into it) I'm following the following logic: Woofer (60-70%): 30W to 35W Midrange (20-30%): 10W to 15W Tweeter (10%): 5W I will apply it in 3 ways, maximum 50w
T/S max flat:
net volume (Vb) (L) = 20*12*0.54^3.3 = 31.4 L
box tuning (Fb) (Hz) = 0.42*43.49*0.54^-0.96 = 33 Hz
dv min. (cm) = ((20*(Sd*Xmax/10)^0.5)/Fb^0.25)/10 = 8.97 cm
L' = 23500/(33^2*31.4) = 0.6872
lv (cm) = (0.6872*8.97^2) - (0.73*8.97) = 48.745 cm
HR calcs ~ 18.77 m/s @ 30 Hz, but 'critically' damping the vent drops it to < 2 m/s!, so the 'name of the game' is build the biggest box, vent you can 'afford' and damp to 'taste' and it 'is what it is'. 😉
Attachments
This tool will help you gain insight in the required diameter and flare:
https://www.subwoofer-builder.com/flare-it.htm
https://www.subwoofer-builder.com/flare-it.htm
Please refer to the corrected version here - just in case:
https://www.diyaudio.com/community/...rbers-and-port-geometries.388264/post-7697685