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Cube Cubed - a Passive Radiator Subwoofer Build

8873 Views 5 Replies 3 Participants Last post by  Brian Steele
I have always loved passive radiators, so I thought I would finally do a build log along with all the parts needed. Thanks to Parts Express, I am able to bring one of these Passive Radiator Builds to life. My goal was to make a small subwoofer that would still have high spl, for a smaller room all while keeping the cost of the major parts under $200. As I looked around, I haven't found many great subs in that price range, so I thought DIY work might give the best bang for the buck. Here's a list of all the parts chosen for this project along with links:

Dayton Audio DCS205-4 8" Classic Subwoofer 4 Ohm
2 - Dayton Audio SD215-PR 8" Passive Radiator
Dayton Audio SA100 100W Subwoofer Plate Amplifier
Harrison Labs FMOD Inline Crossover Pair 30 Hz High Pass RCA

I didn't have a separate DSP, so I had to go with an FMOD for the High pass to protect the woofer from over excursion. I did test it, and it was an issue. ALthough, if you have a DSP you would not need the FMOD. The total cost with the FMod is $190.

The Enclosure is a very small footprint sitting at a 14" cube with 3/4" MDF or a 13.5" cube using 1/2" MDF. So it is a great footprint for a smal room.

Later I'll post the theoretical response before room gain via WinISD. I will say, I have been playing this and it blew me away. I was very pleased with the SPL this thing can put put out, especially for it's size.
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Very unique build. Thanks for sharing that.
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Thanks! I thought I would share some of the graphs that inspired me to build this.

Theoretical Frequency Response with no added mass in a 1 cubic foot cabinet.

Theoretical SPL using 100 watt amplifier (106DB)

Cone Excursion without a High Pass

Cone Excursion with 30hz High Pass

When I get it all assembled, I'll post the actual graphs via REW and my UMIK1.
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Finished Pictures: I may repaint it. My wife likes it so much, she wants it in the living room. That means, it'll need to be white. Oh well..

Size and Cutouts:

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Nice build. I'm currently building a subwoofer for my multimedia system (its existing little 4" driver in a gnat-sized box doesn't constitute a "subwoofer" by any stretch of the imagination) and I opted to use the Dayton DCS205 8" driver as well, though I did go for an "MLTL" type alignment instead. Net box size is about the same as your build, but my Fb is slightly lower (I plan to use a little EQ around Fb to pull it back up and extend the response of the subwoofer to 30 Hz). The build it still underway - I still have to sand and paint the box.

Have you done any sort of frequency response or linearity tests on your build? I'm curious to see what the results look like. I've done a linearity test on mine (basically run the sub at different input voltages to see if the response curve changes) and I'm quite happy with the results.


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Oh, I forgot to mention - I used 21mm MDF, and run into a little problem with the DCS205 - there wasn't enough clearance between the push terminals and the side of the cutout for the driver, which resulted in them getting pushed in and the cables to the driver getting disconnected when it was screwed into the box. The driver kept cutting out during testing, but otherwise tested perfectly (when out of the box). It took me a while to figure out what was going on, LOL. Chamfering the side of the driver cutout resolved the issue.
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