Building Resonance Free Subwoofers

@rhg3 That is an understatement! Those woofers used a total of 230 shop hours. The going rate is $250/hour or $57,500!! Materials totalled $2300. Cost to manufacture $59,800. If they were direct marketed they would sell for $120,000. Most people only need a pair for $60,000 and you need a crossover and amps. Very few people will spend that much on passive subwoofers not to mention I have already told my friends with big systems that I am not making any more. Perhaps a manufacturer will see the post and find efficiencies to get the price down low enough to make them commercially viable. All I want is credit for the design. 

@rick_n ​​@audioquest4life Thank you both.

@blackbag20 They cross to the ESLs at 100 Hz 10th order. The first thing you notice is you can hear every bass note clearly. Many systems including my previous designs have one note bass. You hear bass but you can not make out the note or rather each note is the same. What you are hearing is cabinet resonance. Put on a set of headphones and you can hear each note clearly, that is what these subwoofers sound like. I put on Primus, My Name is Mudd which has an insane bass line and tell people to put their hand on one of the subs. They always then put their hand on the driver to make sure the sub is playing! Then, I get this look of amazement. 

$250/hour! I got in the wrong businesses. Beautiful workshop. Nothing like enjoying the fruit of your labor.

That's quite a project, thanks for posting.  I really envy some of those machine tools. 

@baylinor The $250 includes labor, tooling, supplies, electricity and rent if applicable. There is also a distinct danger element. Much of the work woodworkers use to do has been taken over by CNC machines with which we can not compete. For me it is the challenge of doing things that mark everything I do as handmade, things that a machine can not possibly do. 

@brunomarcs I think you envy the wrong tools. I can make anything with a band saw, a lathe and my hand tools. All those other machines just buy me time which is important but secondary. I encourage young aspiring woodworkers to start collecting hand tools, get a band saw and learn how to sharpen. The other stuff comes down the line. 

Wow, and I thought my design and build was extreme!

I originally was going to make the enclosure for the Rythmik F15HP DIY kit employing the design Danny Richie shows on his GR Research website: a double-wall box, with the space between the two walls filled with sand.

After considering the resulting weight, I instead built a dual-wall box, the inner layer MDF, the outer Baltic Birch plywood, with no space for sand. I then braced the Hell out of it: a 1.5" x 1.5" BB ply brace every 5" in every plane---front-to-back, side-to-side, and top-to-bottom. The bracing prevents the enclosure from "expanding" in reaction to the low frequencies contained in recordings, minimizing the resonance of the walls and raising the frequency of that resonance to way above the frequencies the sub reproduces.