I finished my cabinet with one UM18 and two PA380s a year ago and I've been itching for something else to build. But we had a baby in October, so my budget for a fun build is basically nil. I got interested in tapped horn subwoofers, and multiple entry horn speakers so I decided, if I could, to build some of those as CHEAPLY as possibly. Just to be clear, low cost is my MAIN goal. And if it can sound good or at least decent I'll be thrilled. Maybe these will just be test beds for future bigger projects.
So first off - a mini tapped horn. Clicking through parts-express I couldn't help but like the no-name, $5.88, 6.5" poly cone midbass woofer. So cheap! I could build anything with that! And if nothing works and it's a waste of time, at least it's barely a waste of money, and I'll be learning. Reviews were really good for such a cheap driver, how could I go wrong?
So I bought six of them.
(pic of 209-699)
Now one thing I learned is that tapped horns don't need as many watts or as much excursion to get decent dB. So I figured why not try to build one with this cheap woofer. Just for fun. To be honest I didn't even bother modeling a horn with this driver in Hornresp until today, weeks after buying them.
And we come to my models. First is the model Hornresp gave me with the initial parameters that I fed into the program. (following some threads here by
and one on hometheatershack)
Not too great looking. A pretty ridiculous peak at 65Hz and just up and down from there.
Anyway, I just started playing with the parameters. First changing L23 (overall length), then changing S1, S2, S3 and S4. (as suggested by lilmike)
Now at first I didn't realize that changing these would make the expansion of the horn change at different rates.
All I was doing was looking for a good Frequency Response. And this is what I got:
Seemed pretty good to me, until I looked at the schematic and found it wasn't really a horn with constant taper any more, just a constant radius pathway. It seems more like a transmission line.
But the frequency response in the Power graph looks really good. Smooth from 35Hz - 100Hz, 106db of output with +/- 3db in that range. Excursion looks good too. Only up to 8mm (xmax is 3.5mm). This is with a full 30watts (11V). :-)
I suppose it really wouldn't be that small - 3.5 cubic feet / 100 liters.
So, is this design any good? Why not try building it if Hornresp shows a decent FR? Or is there something I'm missing?