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My Behemoth Subwoofer

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Project by Gianni posted 02-13-2014 04:02 AM 1130 views 1 time favorited 5 comments Add to Favorites Watch

Was watching the olympics and realized I never posted a pic of these. This was one of my first woodworking projects and one of the things that sparked my interest in making stuff from wood. I was a bit of an audiophile, and a physics geek through high school and college, and have always liked playing with the equations for speaker building and trying to come up with designs. Through the years I have drawn up some pretty wierd stuff, so it’s a little strange that these are so traditional.

My goal was shattering effects when watching movies and first-rate sound for listening to music. To keep response flat to 20Hz, the sub cabinet would’ve had to be nearly 8ft tall, and I didn’t think I could sneak that by the wife as “normal,” even for me. I was able to keep a manageable size and only lose a little bit of the rock bottom: this cabinet and driver are flat to ~24Hz with about a 2.5dB rolloff at 20. The driver is a Dayton titanic iii with a 1000W plate amp mounted in the back.

The design cues for the sub, with the truncated octagon, were taken from the satellite pair. These are sealed cabinet 2-ways with a pair of Dayton 6.5” woofers and a Pioneer dome tweeter. Inside there is a 2-way passive crossover at around 3.5kHz at 12dB/octave. The cabinets are duodecagons (sp?), 12 sided polygons with elongated front/back. Each side has alternating oak and birch veneers, and the stain matches the coloring of my tv cabinet quite closely.

The sub and satellite cabinets were constructed using mdf, because of it’s audio properties. The main cabinets were veneered and then solid oak tops and bottoms were added, along with mitered decorative mouldings to help break the large vertical surface of the sub. The satellites are in the 15-20lb range, being 1/2” mdf with bracing and damping. The sub is probably close to 150+ lbs, being made from 3/4 mdf, braced every which-way internally, lined with around 3-inch thick damping, plus the driver itself is probably over 20lbs, and the amp’s heat sink.

The gloss black grills are also mdf. They are removable, though I don’t think they have been off since moving them in the house.

I have been extremely happy with the looks, but the sound is spectacular. I did have to add felt pads to all the pictures and clocks and anything that hangs on the walls in the living room and kitchen, especially when playing 80’s hair metal or Grateful Dead (strange combo, yes, but again… “normal” is for posers). Whe listening to TV, they provide a solid, uniform sound without the rolloff at the bottom. Not “boomy” but there is a lot of sound on tv that you never realize is there.

Thanks for looking.





5 comments so far

View Brett's profile

Brett

937 posts in 2221 days


#1 posted 02-13-2014 02:33 PM

Wow! The speakers must work very well, I can see that they have melted the candles right off! ha ha

Really, nice job. It sounds like you put a lot more effort into building yours than I did with mine. In high school, I just built a plywood box and screwed some $12 flea market woofers into the holes. It worked anyway.

-- Hand Crafted by Brett Peterson John 3:16 http://www.TheCrookedNail.blogspot.com

View SawdustTX's profile

SawdustTX

240 posts in 1786 days


#2 posted 02-13-2014 08:53 PM

Awesome design and craftsmanship!

You mention MDF grills. Do you have MDF grills you install over the speaker elements? Seems like MDF would absorb too much of the sound unless it was mostly perforations. Very curious what your grills look like – is that them in the background of the sub picture?

here’s why I ask: I have a pair of JBL L 100’s in my shop but the grills are just cloth stretched across an open frame. I want to protect the speaker elements from the occasional impact when I’m negotiating a long piece of stock through the room (already crunched one tweeter). But I don’t know enough to design them to not impact the sound quality.

View Gianni's profile

Gianni

228 posts in 1436 days


#3 posted 02-14-2014 03:29 AM

When I say grilles, I just mean the gloss black “8” shaped faces that you see in the pics. They are attached to the cabinets using little press-fit nipple/socket pairs so that they are removable, but offer no protection for the drivers themselves. I did round over the edge surrounding the driver to dampen any diffraction effect.

If I wanted to build a protective grill, I think any cross or mesh design would be ok, so long as you were cautious to avoid hard edges on either the driver or the outside face, and keep the gaps distant from any of the audio wavelengths that the driver it protects is generating lest it act as a horn. This is all speculative, of course – I haven’t really studied grill design much, just sort of adapting general rules to a very small area around the driver. Will be interesting to see if anyone else chimes in and teaches me a thing or two. If you want to go for max protection, I would suggest an inverted horn cabinet. I tried to google, these used to be fairly common (klipsch used them on their larger speakers) but they must have fallen out of style.

View Rick's profile

Rick

8287 posts in 2495 days


#4 posted 02-15-2014 06:08 AM

*

-- Hope Everyone Is Doing Well! .... Best Regards: Rick

View SawdustTX's profile

SawdustTX

240 posts in 1786 days


#5 posted 03-06-2014 04:11 AM

thanks for the info. I’ll do some googling and see what I can learn.

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