DIY Subwoofer Project

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Well I'm going to be building a small sub for my room. It will go along with the HK 3485, and Inifinity Beta 20s. The room is small...and I really won't be driving this too loud.

Here is my current idea:
ED 11Kv.2 (D2) Subwoofer
ESP P68 Amplifier (300/500W? (not sure yet))
.5cF sealed enclosure

So my questions:
1) What do you think?
2) Should I go with 300W since the room is small...
3) Is a .5cF enclosure big enough?

1. Quickly modeling the woofer in WinISD reveals it is a poor choice for home audio use. f3 = 66hz, yuck. This woofer is designed for a car, where massive cabin gain will yield a flat response in a small box.

2. 300watts is just right for this woofer.

3. It's big enough to sound good in a car, or a closet. In a room, you will need bass boost to flatten things out. Going to 1 cu ft would only help a little, really you need a woofer designed for HT.


I agree with Owdi if a 0.5 cu ft closed box is the case. See picture 1(7) where the 0.5 cu ft closed box is modelled.

I’ve also modelled this driver in a 1 cu ft, closed or ported box, see picture 2(7) and in picture 3(7) comparing this driver with a more suitable slot ported box of about 2.74 cu ft.

Picture 4(7) to 6(7) shows a more complete simulation of the slot ported box that could be powered with a > 250 W Rms if the bass amp is fitted with a filter cutting off at about 20 Hz.

Note the 1 cu ft ported box shows a high port air velocity when fed with 13.5W Rms input power, which makes this solution a poor choice.

Of course the box could be equipped with an external wider-longer port like 2 x dia. 4” x 80” ports to tune the box slightly below fs, but for this case the unavoidable severe port resonances would be very difficult to tame.

Better is to increase the internal volume and for the case of the slotted ported box I’ve used 1.175 x Vas and kept the port in the box.

This box allows easy port trimming and the port = duct lower BW end is calculated to be 5 Hz with an input power of 250W when the port air velocity is at a low 12.5 m/S. See picture 7(7).




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