I've just finished modelling and drawing up a vented enclosure for the Dayton Audio RSS315HF-4 12" Subwoofer.
Can anyone give me a critique on the design or see if I've made any errors?
I've modelled it as an 80L vented enclosure, tuned to 24.35 Hz with a 200w input signal. The amp is a 500w BASH plate amp. I'll set the HPF to 20 Hz.
I've read in some forum that the driver displacement is 3.8 L but no idea if this is correct.
Any input would be greatly appreciated.
Parameters as follows:
Impedance 4 ohms
Fs 24.2 Hz
Re 3.1 ohms
Le 0.96 mH
Qms 2.83
Qes 0.45
Qts 0.39
Vas 84.1 liters
Cms 0.23 mm/N
BL 13.99 Tm
Mms 188g
Xmax 14.3 mm
Sd 514.7 cm²
Vd 736.0 cm³
Can anyone give me a critique on the design or see if I've made any errors?
I've modelled it as an 80L vented enclosure, tuned to 24.35 Hz with a 200w input signal. The amp is a 500w BASH plate amp. I'll set the HPF to 20 Hz.
I've read in some forum that the driver displacement is 3.8 L but no idea if this is correct.
Any input would be greatly appreciated.
Parameters as follows:
Impedance 4 ohms
Fs 24.2 Hz
Re 3.1 ohms
Le 0.96 mH
Qms 2.83
Qes 0.45
Qts 0.39
Vas 84.1 liters
Cms 0.23 mm/N
BL 13.99 Tm
Mms 188g
Xmax 14.3 mm
Sd 514.7 cm²
Vd 736.0 cm³
514.7 cm2 x 1.43 cm = 736 cm3
That is 0.736 liters
3.8 liters seems to be unrealistic, even if considering a p-p displacement and allowing more (distorted) excursion.
sorry, I completely missed the point! The intalled driver occupies 3.8 liters, right?
I created a VituixCAD model of this driver in your vented box. The results are shown below and are quite like yours in many respects. I adjusted the input power to correspond to 150W re 4ohms to achieve a maximum cone displacement of 9mm at about 32Hz.
You will notice that my computed SPL response curve sags a little compared to the one produced by your simulations. That is due to the lower tuning frequency of Fb=21.7Hz, which results from using a vent end correction of k=2.27 instead of k=0.732. The value that I used is the best one that I know of. Maybe someone else can chime in and confirm this value or propose a different one. Here the low-frequency cut-off point is f3=27.1Hz.
You mentioned that you intend to use a 20Hz high-pass filter. The results look like the following with a 2nd-order Butterworth 20Hz high-pass filter added. The displacement below Fb is considerably reduced, and the low-frequency cut-off point is still quite low, being at f3=30.8Hz.
With a little bit of EQ at around 20Hz, say by adding a 2nd-order 20Hz high-pass peaking filter with a Q=0.85, it should be possible to achieve the result shown below. The displacement peak below Fb is only increased slightly, while the low-frequency cut-off point has been significantly reduced to f3=25.6Hz. That's a 5Hz reduction, which would be quite worthwhile in getting the best performance out of the driver in this size of enclosure.
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There was an error in the previous simulation that included the use of the peaking high-pass filter, as the model used k=0.732 instead of k=2.27 as the vent end correction factor. Apologies for the oversight.
With k=2.27 and a 2nd-order 20Hz high-pass peaking filter with Q=1.20, producing a boost of about 2.4dB at 25Hz, the results of the VituixCAD simulation are shown below. The low-frequency cut-off point is now f3=22.1Hz, and the driver's Xmax is reached at 15.4Hz. Note that very similar results could be achieved by simply applying a parametric EQ of 4.6dB at 20Hz with Q=1.20 on top of the 2nd-order 20Hz Butterworth high-pass filter.
With k=2.27 and a 2nd-order 20Hz high-pass peaking filter with Q=1.20, producing a boost of about 2.4dB at 25Hz, the results of the VituixCAD simulation are shown below. The low-frequency cut-off point is now f3=22.1Hz, and the driver's Xmax is reached at 15.4Hz. Note that very similar results could be achieved by simply applying a parametric EQ of 4.6dB at 20Hz with Q=1.20 on top of the 2nd-order 20Hz Butterworth high-pass filter.
I don't like slot vents, especially those as wide and narrow as you have shown. You would likely be better off with one of these on either side of the enclosure, for vibration cancellation. This way, you won't have any any problems with vent chuffing.
https://www.parts-express.com/Dayto...Series-Aluminum-Cone-Passive-Radiator-295-504
Model it and make sure it works,
https://www.parts-express.com/Dayto...Series-Aluminum-Cone-Passive-Radiator-295-504
Model it and make sure it works,
A slot port does not compare favourably with a round one, its area is pretty small, and the length to area ratio is very high. (If it's limited by what you can fit in the box, fair enough...).
No port shape compares favourably with a single round port!
No port shape compares favourably with a single round port!
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I've explored the PR route. I can't justify the expense at the moment.
With the slot port, do he dimensions matter if the air velocity remains below 17.5m/s?
Thanks for doing all this. I need to get a copy of this software and start playing around with it.
Round is certainly the most efficient, but for those of us that prefer moving towards aperiodic, the high aspect ratio ducts are the way to go. 😉
The only issue that I can see and others have addressed is the ratio of the slot port. Simulation programs will only get you so far with the behavior here. A stead fast rule for slot ports has been a ratio of no more than 1:8 which is about the threshold for laminar flow of air.
My suggestion would be to reconfigure your drawing/plan including a suitable length and cross section port to give you your desired tuning. Don’t sweat the small stuff…..if your off a liter in displacement or 5% of the port calculation, that’s well within the variance of the system overall.
Your drawing doesn’t show any internal bracing?……..I’d add at least one window brace spanning top to bottom and side to side. Two would be better of course. And don’t forget to line the inside with a suitable wool/fiber material. Enjoy!
My suggestion would be to reconfigure your drawing/plan including a suitable length and cross section port to give you your desired tuning. Don’t sweat the small stuff…..if your off a liter in displacement or 5% of the port calculation, that’s well within the variance of the system overall.
Your drawing doesn’t show any internal bracing?……..I’d add at least one window brace spanning top to bottom and side to side. Two would be better of course. And don’t forget to line the inside with a suitable wool/fiber material. Enjoy!
You will lose a few dB of output and increase distortion, but not so you would notice, and also depending on if you plan to run them to their absolute maximum output capability, which is never, EVER a good idea. Big output requires big cone area; how did you choose the Dayton driver, and how much is it?
Move a Lot of Air - GENTLY!
The Dayton Audio RSS315HF-4 12" subwoofer driver is available from Parts Express for $220 USD with FREE SHIPPING.
Reasons for choosing this driver may include the following. For its class (12-inch subwoofer), it is a reasonably high-performing driver, with an Xmax of 14.3mm. Its sensitivity is quite reasonable at 90.3 dB @ 2.83V/1m. If the frequency response curve is accurate, the raw driver frequency response is also very smooth up to 1kHz or so, making it easy to filter even at slightly higher crossover frequencies if necessary. Its Thiele–Small parameters make it well suited to closed-box as well as moderately compact vented box enclosures. In an 80-litre vented enclosure, the driver produces a slightly rounded response, which should help to integrate it in a room. With 100W re 4 ohms of power input, which isn't that high, the vented alignment can produce 100dB SPL at 22Hz with the 20Hz high-pass filter in place. The excursion is only around 1/2 of Xmax at that power level, and the vent air velocity isn't all that high. Even with 300W re 4ohms of power input on peaks, the system should still be behaving relatively linearly. The vented-box low-frequency alignment also seems to be quite amenable to a little bit of judiciously placed low-frequency EQ if some extra low-frequency extension is desired but without too great a risk of overloading the driver.
Of course, 15-inch or 18-inch subwoofers can produce more maximum SPL, or work a little bit more gently to get to 100dB or 105dB SPL with relatively low excursion and lower power requirements. However, their enclosures are likely to be quite a lot larger, unless sealed enclosures are chosen.
Reasons for choosing this driver may include the following. For its class (12-inch subwoofer), it is a reasonably high-performing driver, with an Xmax of 14.3mm. Its sensitivity is quite reasonable at 90.3 dB @ 2.83V/1m. If the frequency response curve is accurate, the raw driver frequency response is also very smooth up to 1kHz or so, making it easy to filter even at slightly higher crossover frequencies if necessary. Its Thiele–Small parameters make it well suited to closed-box as well as moderately compact vented box enclosures. In an 80-litre vented enclosure, the driver produces a slightly rounded response, which should help to integrate it in a room. With 100W re 4 ohms of power input, which isn't that high, the vented alignment can produce 100dB SPL at 22Hz with the 20Hz high-pass filter in place. The excursion is only around 1/2 of Xmax at that power level, and the vent air velocity isn't all that high. Even with 300W re 4ohms of power input on peaks, the system should still be behaving relatively linearly. The vented-box low-frequency alignment also seems to be quite amenable to a little bit of judiciously placed low-frequency EQ if some extra low-frequency extension is desired but without too great a risk of overloading the driver.
Of course, 15-inch or 18-inch subwoofers can produce more maximum SPL, or work a little bit more gently to get to 100dB or 105dB SPL with relatively low excursion and lower power requirements. However, their enclosures are likely to be quite a lot larger, unless sealed enclosures are chosen.
That driver in 80L performs well. I would just change to a round port and do the final port length tuning by measurement after it's built. I always make my ports removable initially to make adjustments. Your port has 2 curves and a poor aspect ratio which will perform worse than the good ol pvc pipe.
I'd go with 4" round port as long as you can fit the pipe length of about 45cm. Much easier to built and flexible to tune. Just keep in mind this pipe will resonate at around 390Hz (you can use a LPF to cut before) and will take about 3.5 liters from your box.
It is expected to sound really cool (FR down to 24Hz @ -3dB on simulation) and powerful.
It is expected to sound really cool (FR down to 24Hz @ -3dB on simulation) and powerful.