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Building the Tidewater TROIKA

Apr 19, 2018
3 min read
  • TROIKATolex2
  • TROIKATolex3
  • 19429706_552897271766812_7641017641663076155_n
  • TROIKARearPanel4
  • TROIKAPartition2
  • TROIKAInputjack1
  • TROIKAHandleFelt
  • TROIKACaster
  • TROIKA10
  • TROIKA9
  • TROIKA4
  • IMG_5279
  • TROIKATerminals3
  • IMG_5206
  • IMG_5205
  • IMG_5203
  • IMG_5179
  • IMG_5176
  • IMG_5171
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A couple months ago, I built a 2x12 speaker cabinet for a recent acquisition - a Two Rock Classic Reverb. It sounded amazing. I had a spare 1x15 cabinet, loaded with a JBL D130F and thought that I'd run it in tandem with the 2x12... OMG! It was like I stumbled onto some sort of ancient tone secret. The only problem was this: To achieve that tone, the pairing of voices was cumbersome and frankly unsightly.

DESIGN: The thought occurred to me that I should try to consolidate the speaker cabinets into a singular component, while aiming to replicate their environments. As I studied speaker cabinet design, I learned a little bit and decided to recreate the popular, sexy, and enduring Marshall 1960 cabinet design for the shell, then come up with some variation to accommodate internal volume tuning and sonic projection. The result is a 35.5" tall slant cab, 5.5" taller than a standard 1960A. GOAL: What I hope to achieve in the design is excellent projection, a focused, tight bass, and sonic excellence. I desire this cab to sound its best with big, loud cleans, but be just as suitable for overdriven tone. The main goal is for this cab to accompany a 50-100w clean amp. SPEAKERS: I currently envision using the same speakers I had in the two cabs in the photos above: Early '70s JBL D130F; 1966 Celestion Silver Vox T1088 w/ original 003 cone; 1965 Jensen C12NA. That may change. I have several speaker options available in my shop. I also have considered the new Celestion 150w Red Back, and another type of 15". STRUCTURE: At this point, I have some ideas about isolating the 12"ers from the 15", as well as what kind of back(s) I'll design - But for now, the birch ply is standing by for marking and cutting:

  • Most assuredly, I will segregate the interior between the 12"ers and 15" speaker. • At the very least, I will incorporate a removable partition between the top compartment containing the 12" speakers, and the bottom where the 15" will be mounted. • There will be two compartments. Rattling is a concern with any internal walls, especially one that is removable, so I'll approach the design with that in mind. • Because I'll remain true to the 1960A design, I cannot affix any permanent structure behind the baffle. It would be nearly impossible to remove the baffle if I did.

  • Completely closed back? Not likely, because I intend to use at least one alnico speaker and I don't prefer those in an infinite baffle environment.

  • Completely open back? That's how the inspirational rig was configured. Before I begin cutting any rear panel(s), I will test drive the cab with a full and partial open back (for each compartment).

  • Open top, closed bottom? Most likely, an in preparation, the 15" compartment baffle is ported.

  • I will test the 15" compartment environment with acoustic foam lining on the L & R sides, and the top.

  • I am researching the effect of rib bracing on the inside rear panel of the 15" compartment.

  • A lot of research has gone into this design so far. The proof will be realized in testing. NOTE: I don't have testing equipment or software, per se. I'd love to acquire the gear and knowledge to use it to qualify/quantify, but for now I'll rely on my senses to tell me whether the sonic properties are adequate.

COVERINGS/HARDWARE:

  • Marshall red elephant tolex

  • Wheat heavy cane grille cloth

  • Medium white grille piping

  • Gold channel string

  • Marshall black plastic corners & gold tacks

  • Replica metal handles supplied by @Scumback Speakers

  • Aluminum caster sockets & Marshall casters

  • 8-32 machine screw fasteners - stainless steel and brass

PROGRESS: The shell and the baffle are complete.

  • The metal handles will fasten with 8-32 SS cap machine screws into brass inserts.

  • The speakers will attach with 8-32 SS pan head machine screws

  • The rear panel(s) will use 8-32 brass slot oval head screws with brass cup washers into brass inserts.

  • The only wood screws used will fasten the caster sockets to the underside, and the baffle to the shell - this is due to the angle required to secure the fasteners in a tight space. They'll be SS as well, with SS cup washers

  • At this point, only fastening agents are Tite Bond II and oak dowels. There are no metal fasteners (screws, nails, staples, etc) between the shell and the frame, nor will there be.

Some photos of the build process as it sets right now, and to illustrate the techniques mentioned above:


 
 
 

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