Hi everybody!
With Brian Steele's spreadsheet published many years ago, I calculated the volumes of rear and front boxes for a bandpass subwoofer with the specs of the Dayton Audio UMII8-22 subwoofer. I found a nice option for Qbp = 1.0 (1.25 dB ripple) and S = 0.5, that requires Vf = 4.73 L (0.167 cubic feet) tuned at 61.3 Hz and Vr = 10.82 L (0.382 cubic feet). I apologize for not translate to English the texts in the spreadheet.
I also simulated the design with LTspice and got with agreement with those of the spreadsheet.
My main worry are the dimensions of the vent of the front box: 2.5 cm diameter and 6.5 cm long, that agrees with the calculation for a Helmholtz resonator. I will not try a bigger diameter for the vent because the length results too big, difficult to accommodate into the front chamber of box-
I would like to read your comments.
Kind regards.
With Brian Steele's spreadsheet published many years ago, I calculated the volumes of rear and front boxes for a bandpass subwoofer with the specs of the Dayton Audio UMII8-22 subwoofer. I found a nice option for Qbp = 1.0 (1.25 dB ripple) and S = 0.5, that requires Vf = 4.73 L (0.167 cubic feet) tuned at 61.3 Hz and Vr = 10.82 L (0.382 cubic feet). I apologize for not translate to English the texts in the spreadheet.
I also simulated the design with LTspice and got with agreement with those of the spreadsheet.
My main worry are the dimensions of the vent of the front box: 2.5 cm diameter and 6.5 cm long, that agrees with the calculation for a Helmholtz resonator. I will not try a bigger diameter for the vent because the length results too big, difficult to accommodate into the front chamber of box-
I would like to read your comments.
Kind regards.
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FWIW, I wouldn't use that driver in a bandpass alignment. Many modern drivers simply aren't a good fit for such alignments, unless perhaps you replace the vent with a passive radiator, and that would significantly increase the cost over a simple vented or MLTL alignment with the same driver.
Thanks a lot Brian. I tell you that I couldn't find many options for a vented box with that driver. Only an "optimum" alignment of 65 L that is too big in comparison with the bandpass box that sums 25 L with the rear and front volumes.
That's what I get in VituixCad
Vr 9L, stuffed / Vb 7L, stuffing on the walls / Fb 65Hz Dv 6cm Lv 22cm
You will loose 4-6dB because of baffle step, but the driver takes a lot of power and Xmax is plenty.
@ 326W
Vr 9L, stuffed / Vb 7L, stuffing on the walls / Fb 65Hz Dv 6cm Lv 22cm
You will loose 4-6dB because of baffle step, but the driver takes a lot of power and Xmax is plenty.
@ 326W
The optimum alignment does allow for a very extended bass response. The bandpass subwoofer is much more limited, and doesn't seem to offer all that much apart from higher SPLs.
Your 25 litre bandpass enclosure will have quite a bit of woodwork internally. If we switch to a plain vented enclosure, then we should save some internal wood volume, giving a net enclosure volume approaching 30 litres or so.
The VituixCAD simulation of the Dayton Audio UMII8-22 subwoofer in a 30 litre enclosure is shown below. The simulation includes the effect of an 80Hz 4th-order Linkwitz–Riley low-pass filter, which would be used for bass management. The enclosure is tuned to 32Hz, with Dv=7.5cm and Lv=36.1cm, which seems quite reasonable.
The low-frequency response has turned out to be quite good―it looks quite optimum in fact. It's relatively flat in the passband, with a maximum output of around 102dB for 100W re 4ohms of power input. The −3dB point is a very respectable 28Hz or so. At this power level, we have a relatively high peak air velocity in the vent at around 30Hz, as expected, but that stays below the warning level for frequencies above 35Hz or so (i.e., for most program material).
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