This thread will document the construction of my custom subwoofer, which has been in-progress for a few months now. Please bear with me this is going to be a doozey.
This sub will be based around a new style RE Audio XXX 18 driver. I went with this driver because it has some big claims made about it, no one else was using them for a home application ( I like to be different) and I got a killer deal on it. The other contender's were the LMS5400 (TC started getting shaky, prices went up, service?), the Acoupower 18 (A few DIYer's finally bought some) and the Aurasound NS18( Unavailable). So there you go.
The best thing about and the main problem with the XXX 18 is that it has so much excursion, but you need a large amount of power to use it all. It also likes a really big enclosure sealed or ported. I decided to go ported with it because I wanted to see what it could do tuned really low. Another problem is since this driver can move so much air you need a big port area to keep from overloading the vent. It's really hard to tune super low AND get a large vent area.
I ended up deciding on 25cuft net tuned to 11hz as what I would like to shoot for. It had a decent simulated response and it would take advantage of the driver's excursion capabilities. The problem is that I also wanted more than an 8" or 2 6" ports for this thing to keep the airspeed down, but for that tune an 8" port is already at 38" long and I wanted a 10"er. A 10 would've needed to be 62.5" long! I was thinking of going with a slot port that was folded inside the cab for a bit when I remembered an old article and calculator I had read about in Audio magazine in the late 90's detailing a patented port and bandpass system used by Polk Audio. There was a file that Polk would send you so that DIYer's could fool around with it. I dug up the files and read through the patents and liked what I found. The patents are as follows...
They are quite an interesting read that I highly recommend.
The port system uses a center flow guide and 2 outer inverted cones to directly match the expansion of the inner and outer flares, channeling the air and increasing the area of the entrance and exit of the port. It also provides no straight line path to the outside air and thus supposedly diminishes any port resonances. It also claims it allows much greater control over chuffing, turbulence and a lower tuning to be achieved. I decided to go out on a limb and try this port system, even though nearly everyone I've spoken with about it seems to think it's a waste of time, will not live up to the hype, or just doesn't comprehend how it works. We will see...just like with the driver.
I also had a certain area in my room that I needed this to fit in so I had dimensional constraints too. I could go no bigger than a 42" X 23" footprint. It will be a huge sub and it will be in plain sight, so I also needed it to be good looking. After running over the logistics of all of this in my head I decided...I don't have the skills,tools, or time to tackle this.
I started looking for someone who I felt was the right kind of person for this job. I looked at some local woodworkers, but they didn't have the required audio knowledge. I looked at ElementalDesigns too, but they were too busy and took forever to get me a quote even. Finally I saw some of the things being done by FunkyWaves Audio and got in touch with Nathan Funk. I layed everything out, all my ideas, wants and I included some 3D mock-ups. He was really helpful and confident about things, we brainstormed a bit, hashed out the game plan and got the ball rolling...
Let me go ahead and say this...I will not talk about cost. Also I know that I could've done a million other things that were:louder, more cost effective, smaller, more practical, blah blah blah, "why not 8 of these sealed with yadda yadda"?. That's great. If you wish to do those things then by all means please do and start a thread about it too
. This is what I wanted to do.
I'll be adding a lot of pictures and other things shortly.