Mandolin, Curved Cabinet, Floorstanding

Mandolin 2-way designed by Jeff Bagby

Curved Cabinet, floorstanding speaker, with 15L of "dead space" below
CNC cut front baffle and internal braces
Sides are 6 1/8" plies of Baltic Birch plywood, MDF, and HDF
Front panel is solid White Oak
I decided to make a small floorstanding speaker with curved sides using Jeff Bagby's Mandolin design. What attracted me to this design was the ability to get full-range extension, smooth midrange, and detailed highs in a faily compact package. I did a LOT of research before deciding which speakers to make. One of the critical factors was reading Jeff's Evaluation of his own design- he has an excellent reputation for quality designs. The second was some extensive measurements that John "Zaph" Krutke made of the SB Acoustics drivers, which by all accounts seemed to offer tremendous value at the price point they were at, comparable to midrange Scan Speak and Seas transducers.
I have always been intrigued by curved cabinet designs, and they do offer several benefits over traditional box design. First, they reduce standing waves inside the enclosure since the width mode and the depth mode are in a state of constant change. This reduces the resonant frequencies inside the cabinet. Second, they are very strong and stiff, with the layers being in constant mild tension. Lastly, the 6 layers of 3 different materials provide some internal damping of cabinet resonance and provide a mix of strength and mass. (MDF is dense, plywood is less dense but strong).
In addition to that, I decided to make these a robust floorstanding speaker. The reason for this is that I normally don't put bookshelf speakers on a bookshelf, and I figured if I was going to make speaker stands, why not build them into floorstanding. Of course, my decision to do so is something I have and continue to question. A floorstanding speaker is not as flexible for placement. I could conceiveably convert these into bookshelf speakers now. They would be 18" high though, which would be a little bit on the tall side.

SB Acoustics

SB Acoustics

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Sketchup of Internal bracing and curved sides- some changes would be made later

Box model using several sources of T/S data

18" DIY Subwoofer

Something Wicked this way comes!

18" Dayton Audio RSS460HO-4 subwoofer

Sealed 110 liter Plywood/MDF/HDF enclosure with intricate internal bracing

Airtight Speakon connector, 1" Industrial rubber feet.

Painted with Rustoleum Hammertone "Black"



Internal braces

Braces dry-fit, this is the back of the subwoofer

Detail of internal bracing system. It's a tight fit.

Gluing it up with corner clamps and bar clamps

The box is made of 3/4" plywood and some 3/4" MDF



All seams were screwed and glued. Uneccesary.

Added more braces to my braces

These corner braces were meticulously cut to fit tightly

Looking through the front hole. This is one baffle, the next is comign soon.

Adding the second baffle, using all my clamps

A little bit of squeeze-out

A little gap there, but it's clean.



The woofer sits just slightly proud

DIY family: 12" Raven subwoofer, 18" Wicked subwoofer, and curved Mandolin speakers

Added hardboard to the top and sides, and then flush-trimmed the front. This actually wored really well.

The hardboard made it thicker, smoother, and covered up the screw holes

The back was also skinned with 1/8" hardboard

woofer cutout with all internal bracking visible. This is a stiff cabinet

I added about 4 layers of grey spray primer, and now Rustoleum Hammertone is going on

I probably could have masked off the inside, but I didn't really care about some overspray

Airtight speakon connector with rubber gasket

Added some R-13 fiberglass insulation. Actually this is overstuff and I need to remove most of this.

18" subwoofer next to 12" subwoofer

One subwoofer is a little proud, the other is recessed

DIY family, part 2

Hiatus

I currently am undergoing an audio Hiatus because of 2 major things going on right now.

1) It's 14er season, so we are hiking almost every weekend! You have to make hay while the sun shines. Next year, the season will be scaled back a lot.

2) I am finishing my basement! I am making a theater room / music room, which will be 12' x 18'. It's going to have a lot of soundproofing features built into it, a built-in 9' x 40" bookshelf (5 shelves), and a built-in ventilated equipment cabinet for the AVR / DVD / BD / SAT. This project is going to take a lot of time and money. 3) I am also doing some landscaping this year. That being said, I still need to finish my Mandolin speakers, which I have now disassembled to protect the fragile woofers and tweeters from damage and UV rays- they are safely in their boxes for now. The mandolins need 2 things. 1- bases on the bottom and 2- cosmetic finishing. They basically need to be sanded smooth, filled in with bondo, fully sealed, and then painted.

Current systems

Currently this is what I am using.

Upstairs: (living room)
Marantz SR5005 AV Receiver
Panasonic BDT-110 Blu-ray Disc Player
Pioneer Elite DV-45a SACD/DVD-A Player
Paradigm Monitor 9 v3 Speakers (2.5 way floorstanding)
Paradigm CC-290 v5 Center Speaker (3-way)
DIY Subwoofer- Dayton Audio RSS460HO-4 18" subwoofer in 2.8 cubic foot sealed enclosure

Downstairs: (man cave)
*UPDATE* The man cave system has been disassembled, for now. HTPC; Intel i5 CPU, 8GB RAM, 1TB Hard Drive, etc
HRT Music Streamer 2 external Asychronus USB DAC
Emotiva Mini-X a100 amplifier (50WPC @ 8 ohms, 80 WPC @ 4 ohms)
DIY Mandolin Speakers (SB Acoustics components, DIY crossover)
DIY Dayton Audio RSS315HF-4 12" Sealed Subwoofer

The Downstairs system to me is really great. The quality and clarity of the midrange and treble is superb. I need to get the basement finished to fully appreciate this system, as the open design doesn't reinforce the bass well. But overall it's a pleasure to listen to music on this system.

What is this blog about?

What is Sound Enthusiam?

This is a blog to document my ventures into Home Audio and Home Theater. It will probably delve into DIY stuff quite a bit, as I can be both frugal and somewhat handy. DIY allows me somewhat of a creative outlet as well.

I hope to document speaker builds, sub builds, home theater setups, and possibly a "theater room" we are hoping to build.

Current builds in Progress:

Dayton RSS460HO-4 18" Sealed Subwoofer build, approx 4 cubic feet.
Status: Almost ready for paint

Mandolin curved cabinet floorstanding:
SB29RDC 1 1/8" Ring Radiator Tweeter
SB17RNCX 6" Paper/Reed Cone woofer
Crossover design by Jeff Bagby:
Status: Fully assembled but needs a lot of finishing work and stands.