Background and Design Premise
I built my first pair of DIY speakers 22 years ago, and despite planning something much more ambitious and expensive just a few years later, I managed to instead build speakers for friends and family and indulge other hobbies in those intervening years. Now I have made up for lost time by building something overly ambitious. I made the cabinet construction more difficult than it needed to be, not only to get an nth degree of additional performance, but to make something visually striking and different, to experiment with new techniques and materials, and to confirm I am capable of doing all of this. It had a lot of educational and entertainment value. Deliberate hurdles include:
Project Highlights
All 3D modeling was done in Sketchup, although there is additional routing and shaping I do not know how to do in Sketchup that I did on the completed speakers. I designed the exterior shape first, then worked my way inwards placing collections of parts on a separate layer so I could work on them in isolation. What I ended up with was the ability to explode the speaker and dimension all parts. Anything too complicated to build from a picture was printed 1:1 and adhered to plywood for cutting. For example, the horizontal bracing that is not perpendicular to the baffle has a different shape on the top than it does on the bottom, as the angle to the side of the brace changes several degrees from the front to the back. I had to first cut to the larger of the top/bottom profile for these pieces and then cut/sand at a variable angle to taper to the smaller profile. This worked reasonably well, but with ~1mm tolerance on all finished dimensions, it added up to a lot of slop during assembly, and I had to fill a lot of gaps with glue or resin.
Project Details
TMWW + SS: 3-way active tower speakers plus dual driver mono sub with 8 channels of amplification.
Drivers:
Sample construction details:
Full design and build galleries.
I built my first pair of DIY speakers 22 years ago, and despite planning something much more ambitious and expensive just a few years later, I managed to instead build speakers for friends and family and indulge other hobbies in those intervening years. Now I have made up for lost time by building something overly ambitious. I made the cabinet construction more difficult than it needed to be, not only to get an nth degree of additional performance, but to make something visually striking and different, to experiment with new techniques and materials, and to confirm I am capable of doing all of this. It had a lot of educational and entertainment value. Deliberate hurdles include:
- Physical design impossible with pencil and paper; blueprints needed to be created using CAD.
- Complicated construction techniques beyond my initial skillset.
- Unproven materials and joinery.
- Shape requires painting, which is 100x as difficult for me as staining and finishing real wood.
- I have never been happy with the reliability of my measurements <500Hz, and this is a 3-way.
Project Highlights
- Unique, sculpted appearance.
- Cabinets are low diffraction, high mass, highly damped.
- Creative construction techniques to account for my lack of tooling and skill.
- All drivers from Scanspeak. Tweeters and mids decoupled from cabinet with Sorbothane gaskets and anchors. Construction-wise, this worked as anticipated, but I have no measurements to prove it was worth the hassle.
- Active DSP crossovers.
- Hypex amplification with one amplifier channel per crossover region.
All 3D modeling was done in Sketchup, although there is additional routing and shaping I do not know how to do in Sketchup that I did on the completed speakers. I designed the exterior shape first, then worked my way inwards placing collections of parts on a separate layer so I could work on them in isolation. What I ended up with was the ability to explode the speaker and dimension all parts. Anything too complicated to build from a picture was printed 1:1 and adhered to plywood for cutting. For example, the horizontal bracing that is not perpendicular to the baffle has a different shape on the top than it does on the bottom, as the angle to the side of the brace changes several degrees from the front to the back. I had to first cut to the larger of the top/bottom profile for these pieces and then cut/sand at a variable angle to taper to the smaller profile. This worked reasonably well, but with ~1mm tolerance on all finished dimensions, it added up to a lot of slop during assembly, and I had to fill a lot of gaps with glue or resin.
Project Details
TMWW + SS: 3-way active tower speakers plus dual driver mono sub with 8 channels of amplification.
Drivers:
- Tweeters: Scanspeak Illuminator D3304/6640 1” beryllium
- Mids: Scanspeak Revelator 18M/4631T00 7” slit cone
- Woofers: Dual Scanspeak Revelator 22W/8857T00 8” aluminum
- Subwoofers: Separate, part of previously completed project. Dayton Audio RSS315HF-4 12" Reference HF Subwoofer 4 Ohm
- Portability of extremely heavy cabinets improved by building separate TM cabinets which sit on top of WW cabinets, isolated by Sorbothane sheets.
- 1-1/2” thick baltic birch baffle laminated from two sheets with silicone adhesive constrained layer. Exterior of baffle slightly curved horizontally, with 1-1/4” roundovers on vertical edges, expanding into additional shaping around tweeters.
- Driver recesses inside baffle enlarged with cove bits to improve airflow and avoid resonances.
- Mids and tweeters decoupled from cabinet with 1/8” Sorbothane gaskets, and are bolted to hurricane nuts which are also decoupled from the cabinet with Sorbothane isolation bushings.
- Woofers are rigidly mounted with T-nuts.
- Baffle tapers from the floor up, and is tilted back 5 degrees to improve physical time alignment.
- Skeleton built from dimensioned parts printed 1:1 and transferred to plywood using a light spray adhesive.
- Curved walls built using internal and external shells with a 3/4” gap and minimal use of spacers.
- Hollow cabinet walls filled with 60/40 mix of dry cement powder and epoxy to provide mass, strength, and damping. Exothermic heat is kept low via the mass of the cement and the use of a slow hardener. Experimentation has resulted in castings that are substantially more inert than baltic birch.
- Additional internal damping provided by aluminum-backed butyl sheets and 3M rubberized auto body undercoating.
- Internal stuffing is blue jeans insulation and pillow stuffing.
- Exterior seams sealed with shellac prior to priming to prevent showing through paint. This has worked well for me in the past, but did allow a few seams to show through this time.
- Painted with textured Rustoleum aerosol paint which provides a matte finish and some scratch resistance. However, getting an even texture on a large surface is difficult.
- All connectors are invisible, as is the star quad 14g cable run under the carpet.
- Tweeter passive circuit:
- 33uF Mundorf Evo Oil cap for protection, in series with
- 2 paralleled 10.0 Ohm 12W Mills resistors to reduce hiss.
- Active: Pair of MiniDSP 2x4 HD, one per L/R channel
- EQ each driver ~1 octave past each crossover point and apply textbook filters
- Room correction of bass frequencies.
- Initial implementation:
- LR4 IIR at 80Hz, 250Hz, 1.8kHz.
- Final implementation:
- LR4 IIR at 80Hz, LR2 FIR at 300Hz and 2.5kHz made possible by well-behaved wide bandwidth drivers
- Tweeters: Hypex NC400 stereo amp with single SMPS600, already tested at ASR
- Mids: Hypex NC400 stereo amp with single SMPS600
- Woofers: Hypex UCD400 + HXR stereo amp with single SMPS1200A400
- Subs: UCD400 stereo amp with single SMPS1200A400
Sample construction details:
Full design and build galleries.
