Hi everyone,
So about two months ago I began probing the forums after being inspired to build my very own Hartsfields. I was asking questions about drivers, crossovers etc. I had very little knowledge about JBL product line, other than a few of the classic guitar and bass instrument speakers. Since then, I have learned a lot from everyone and continue to learn about the history and the JBL product line. The project is now well under way so I thought is was time to document the progress.
So way the Hartsfields?
Drawbacks? Many! Massive, heavy, expensive, dated, complicated.
Pros? Folded horn, dynamically revealing, powerful, JBL has the best drivers around, fantastic sound, and totally cool.
The main attraction for me was JBL's no compromise attitude in trying to blow Klipsch out of the water. JBL had the leg up, even though the klipshorn predated the Hartsfield, since JBL had the best drivers in the industry. This coupled with the best cabinet in the industry would surely be magic.
Second, I love the idea of high efficiency horns. Perhaps this is just the engineer in me, but minimizing driver movement while getting desired listening levels makes sense. I guess this is a little backwards from the initial days of horn speakers.
Volume level was the most desired characteristic, shaping the development of horn speaker systems. Theaters and stadiums needed louder PA systems and horns were the answer. Minimized driver movement was simply a side effect of the horn design. For me, minimal motor distortion and unparalleled transient response seems key for high fidelity; and are all benefits of a full horn system. That is if you can make a horn structurally sound, which does not add coloration. (Enter JBL)
For drivers the current lineup is: 15" 130A, 2441 Compression driver, 075 tweeter. I’m using JBL 3115 can N700 Crossovers (500 and 7000Hz), which I soon plan to rebuild with air core inductors and better caps.
The woodwork involved with these cabinets is simply staggering. Complex joinery, small pieces with complex angles, lots of fitting and gluing. Even using JBL plans in conjunction with CAD drawn plans, it is hard to wrap your bran around the project. Plenty of errors in both plans also help bring about headaches!
So... instead building it myself I have hired a good friend, Fred Goldstein of Heartwood Custom Interiors LLC, to do the building. His craftsmanship is second to none and attention to detail is spectacular, as I have come to know his work well over the years. I should also note that he has made small modifications along the way to better the design. For instance, the baffle for the midrange horn has been contoured to continue the shape of the horn, rather than leaving a hard 3/4" deep lip at the mouth. This kind of detail has been added everywhere in its construction.
For materials we are using mainly 3/4" Baltic Birch for all of the structural pieces and 3/4" medx moisture resistant MDF for large flat surfaces that are to be veneered. Joinery is biscuit-ed for pre aligning and added strength. Everything is glued as well as screwed together. They really are the nicest cabs around and much better than other repros or what JBL would have used at the time. No Home Depot cheap-o ply or cut and shaped 2x4's in this cabinet!
A good chunk is out of the way.
Next steps: Assembly of inner horn to outer cabinet. Caulk and smooth all facets and joints in the pathway of the bass horn. Then spray the assembly with black paint to smooth the wood inside of the horn pathway.
More to come,
Matt
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