Sunday, February 13, 2011

30Hz Tapped Horn, or A Really Big Subwoofer

Although its very large, and some of you may not think that 30hz is very low, this small footprint subwoofer will knock things off the walls of your home.  When placed in a corner, this subwoofer has an incredible efficiency.  Enough to keep up with any main speaker and will keep up with almost any system, even if only powered by 100 watts.  This subwoofer has an efficiency of 105db per watt, a maximum output of over 125db from 29hz up (when placed in a corner), and only takes up a spot on the floor that is 2ft wide and 18 inches deep.  The only downside is that it is 5' 8" tall.  However, if you have a room where your wife or girlfriend doesn't care about asthetics, then the height of this beast shouldn't matter.  This sub uses 4 Aurasound NS8-385-4A woofers loaded into a tapped horn designed using hornresp, downloadable here  The woofers are available from Madisound at
I really only reccommend this sub to those who don't need output below 30hz, and to those with very efficient main speakers or like their music VERY loud.  This subwoofer will do very well with music as it can hit the lowest notes of bass guitars and pianos easily, and with incredible fidelity and ease.  I also reccommend a high order active crossover of 24 to 48 db per octave starting at any point below 90hz.

Frequency Response

Impulse Response

Aura NS8-385-4A

I hope this explained it enough.  Also, This sub could be folded another time or a few more times so that it would be able to fit into a car.  Well, probably not a compact car, but an SUV.  Just ask in the comments and I'll put a double folded one up here.
Another thing I just thought of, it would be advantageous to put two of the woofers with the cone facing the opposite direction of the other two and wiring those two out of phase with the others.  This would help cancel out second harmonics caused by asymmetrical electromagnetic forces in the motors.  Some people claim that this has a huge effect while others don't seem to hear it, but if the magnet will fit the other way in the horn, then it should be a good thing to try.


  1. Did you use Aura's aspects or did you measure T/S parameters? The Fs on my set of NS8s was off by quite a bit, changing the modeling in horneesp.


  2. I used auras specs, I didn't build this particuar sub, but I built the smaller version and it sounds fantastic. Blew the insulating plastic over a window in my living room into my side yard.