Dan's custom Tannoys

These cabinets were a challenge as they became heavy very early on, ending up at 200 lbs. each without the drivers or crossovers installed! The drivers for these enclosures are the Tannoy HPD-315 12" Monitors. (picture is of the 15" models) Here are some specs from the Tannoy literature I borrowed from the Kiewa Valley site:

"The HPD-series was the last model in the classic series first launched in 1947. All models from the Monitor Black through the Silvers, Reds, Golds and lastly the HPD's used the same basic design with minor refinements to LF cone surrounds, dustcovers, rear-loading of the HF diaphragm.

Perhaps the most significant performance changes were achieved through the use of more sophisticated crossovers on the later models like the Monitor Gold's and Monitor HPD's.Desirable features of the HPD series are:

• Ticonal-G magnet (a trade-name for Alnico)
• Very low-resonance LF cone (around 20Hz, versus closer to 30Hz for all previous designs). A down-side is that the high-compliance close-cell roll-surround on the LF unit disintegrates after about 15 years, requiring replacement).
• High power rating of 85 Watts integrated programme material
• A more transparent dust-cover than the Monitor Red and Monitor Gold, giving better treble clarity
• Well controlled LF cone with the so-called "girdacoustic" ribbed strengthening on the rear face (as shown at left). "

Dan also found the crossovers from some original enclosures which I forwarded on to Dave Schulte in Michigan for some upgrades. There were two design options available, one 42 litre called the Devon, and one 65 litre design, the Cheviot . Further research turned up a recommendation for 150 litres, tuned to 35 Hz with twin 4" ports. We decided that the larger enclosure would be better and used this as our design starting point. I am not usually involved in the technical design as I try to put all my efforts into the build quality and let the designers do the math. I felt confident putting together this bass reflex design however and drew up the plans below (drivers were rebated in final version and two additional braces were added).

We also felt that a really thick wall would assist in eliminating panel resonances and chose to layer up some 1-1/8" MDF with some 3/4" for a total wall dimension of 1-7/8" throughout. An eggcrate foam was used to kill internal reflections, and time will tell if any further stuffing will be needed. Dan chose some really nice Sapelle Pomelle veneer for the exterior and I started working. The WBT polished platinum topline terminals were quite expensive so we opted to include the crossovers in the speaker box and eliminate some expense. I changed some dimensions in order to maintain the correct internal volume and built the crossovers into a chamber at the lower rear of the cabinets. The trim plate around the crossover (shown in lower picture) is made from solid Sapelle.

I had been wanting to try some of the Italian high gloss acrylic urethanes by Ilva instead of my usual nitrocellulose lacquer finish. This turned out to be quite a challenge and in the end took several weeks and many more dollars more than I anticipated as I had to tool up for the process. No lesson worth learning is easily come by! I called in Dennis Markley of Markley Custom Drums to assist me in this finishing process as he produces beautiful drums using this same product, and with his help eventually the finish was completed. I believe they are striking with the Sapelle revealing some fantastic grain and colors. I have shipped them to Dan and await his report on how they sound after he installs the drivers, crossovers and floor spikes. I imagine that they will be quite nice indeed!

Update: Dan loves the cabinets and they sound fantastic! You can visit his commentary on AudiogoN at this link:

Here is one comment from a visitor to his home;" The Tannoys are beautiful to look at, but the music which they produce is heavenly.
Sitting in Dan's room feels like you are in an opera house, bar, concert hall or studio. The music is clear, tonally balanced, dynamic, without a hint of boomyness or harshness. Rarely have I heard such a worldclass set."

Dan has forwarded several emails to me from his audiophile friends and everyone really loves the speakers. A success story!