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Ricci's Skram Subwoofer & Files


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This is the long delayed single driver sub similar in design to the Skhorn. Overall the performance goals and criteria were quite similar. Big surprise there! The Skhorn works so well at what it does that I didn't feel the need to reinvent the sub for this one. This is primarily designed as a professional sound reinforcement or live sound style subwoofer. Big output and clean sound in very big spaces, while covering the typical bass heavy range of music, has always been the primary mission for this sub. Same as it was with the Othorn and Skhorn. It can and I'm sure WILL be employed for other types of situations, but it's a festival or club sub that just happens to be flexible and neutral enough to work in a variety of scenarios. 

The main differences between the Skram and the Skhorn are as follows. 

Optimize it more for the cost effective 21's like the 21DS115 and Lavoce SAN214.50 rather than the Ipal drivers like the Skhorn. The Ipal's still work of course, but I relaxed things a bit for the drivers that are a little easier to afford and power. 

Increased size: Originally I wanted to basically saw the Skhorn in half and slap a top panel on there with modded bracing. It would be a very compact 21" sub, which is great, but the driver would fire directly into an outer panel and even with bracing this is a lot of energy being beamed on axis into a large outside panel. I've never been a fan of high pressure loadings with big drivers that do this. I always want the direct on axis energy from the cone to act on internal panels that are going to keep this energy inside of the cabinet better. This required a rearrangement of the internals. I also added a bit of size while I was at it. I decided to stop at a size that was significantly smaller than the full Skhorn, but not as small as a true half. If this cab is too big or heavy you could always build the true half Skhorn, which would be 24x32x27.71. 

Increased vent area and slightly increased vented chamber volume. This should help the noise, compression and output near the vent tuning.

Increased vent area and length means that the vent pipe resonance is lower in frequency than the Skhorn. I'm, expecting that the response will be less smooth above 150Hz, but that's the tradeoff made for bigger vents. 

The Skram has 4 vents instead of 3 like on the Skhorn. I decided to add one more for even more tuning options. Tuning with all vents open is basically the same. 

Being a single driver design, the Skram does not have the dual opposed drivers for mass induced vibration control like in the Skhorn.

Other than these changes I would expect that this design behaves and sounds very similar to the Skhorn. I'd expect that the two could be used together without issue. They are more alike than dissimilar. 


Skram Dimensions: 24"x32"x36" (609.6mm x 812.8mm x 914.4mm)

Weight: Cab=115lbs or 52kg projected (Driver will add another 25 to 55lbs (11 to 25kg) depending on the driver. 

Vent Tuning: All vents open = 29.5Hz / 3 vents open = 25.5Hz / 2 vents open = 20.5Hz / 1 vent open = 14.5Hz

Each vent is greater in area than a 6" pipe. All vents open is equivalent in area to 4x 6" ports. 

All of the usual pro 21's should be a good match.

18Sound 21ID, 21NLW9601

B&C 21DS115, 21SW152, 21Ipal

RCF LF21N551 looks decent

Lavoce SAN214.50

Eminence NSW6021-6. 


NOTE about the prints!

These are extremely detailed due to being designed in Solidworks and the plans from which my personal cabs would be built. The simplified layout drawing is really all that should be adhered to to build this sub. The bracing and hatch can be simplified to suite your own ideas or the tools available to build the cabs. Just make sure it is solid! Any or all of the hardware can be deleted or substituted or modified to suite your needs. Even outer dimensions can be adjusted within reason. Think of the plans as a chassis guideline that can be modified to taste. You don't have to put all of those holes in your braces or use the handles, a half inch roundover on the cab edges, add a cutout for a plate amp on the hatch, etc...

Skram print.pdf





DXF files...

Back Brace 1^Skram_TI x2.DXF

Back Brace 2 ^Skram_TI x 2.DXF

Bottom Braces^Skram_TI.DXF

Bottom Brace^Skram_TI x 2.DXF

Front Brace^Skram_TI x 2.DXF

Mid Brace x 4^Skram_TI.DXF

Top Brace^Skram_TI.DXF









Hatch Brace Small^SKHorn.DXF

Hatch Brace^SKHorn.DXF



Double - Middle Two.SLDPRT

Double - Middle Two.SLDPRT.DXF


Single - Left or Right.DXF









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8 hours ago, Ricci said:

Sorry guys I meant to make this topic hidden. Kinda jumped the gun a bit. Thought I would have the files ready but Ice been too busy to wrap them up the last couple of days. Hoping to get to it before the week is out.

Sweet, maybe I can build one or four this weekend then.

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Well I added some info and screenshots at least. 

I don't have real cabs or test data yet but it will happen this summer. Based on the results from my last couple of designs I've got a high confidence of what these are going to behave like. 

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10 hours ago, Ricci said:

Well I added some info and screenshots at least. 

I don't have real cabs or test data yet but it will happen this summer. Based on the results from my last couple of designs I've got a high confidence of what these are going to behave like. 

You'll most likely get this built and fully tested before I get anything done with my projects. Thanks for sharing the renderings and concept.

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Looks awesome Josh!  Since I am in wood cutting mode I believe I am going to give this a go!   I would assume the 21sw152 will still be a good match for this?  Quick question for anyone.  When Josh says we can follow the images he posted (I don't see a file link) to build the box, what would be the best way to go about this?  I am thinking print out the images and try to scale the images up to the desired dimensions?  Any thoughts how to best to do this?

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Figure I might as well throw this out there while I'm at it. Im not in love with the skids I have on there for stacking. Anyone have better suggestions for hardware/ feet for stacking?

Im looking to be able to stack bottom to bottom and top to top. That's the 24x32 sides.

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Good looking (and likely performing) single-build of the SKhorn - anticipating measurements/testing.

Do you see yourself returning to Tapped Horns or even Front Loaded Horns with future builds? Does the SKhorn (singles or not) sound like TH or FLH's with similar tuning frequency - seeing that it houses its driver hidden inside the enclosure, or how would you describe it sounding different?


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