Monday, 1 February 2016

The TrueFi Tannoy Enclosure – The Manufacture

Hello to everybody,

continuing reading here in the new year 2016. So I will start with a new article about my Tannoy speaker design. Still I cannot believe how exceptional these speakers in such a cabinet design do work out, even after two years of every day use I do not miss anything. People who know standard alnico versions from Tannoys classic or prestige range (mostly with reflex designs and a more or less too small scale volume) do not have a close perception of what this speaker is able to do. Almost refined and rich textured invisibility with fast transient response, due to its dipole design, combined with finest detailed natural musical resolution show a stage of musical completeness, tannoy normally are not known for. The typical bold, hardly textured and more than rich sound of historical Tannoy speakers, has been improved to a before unknown level for such 15-inch speaker. They remind me a lot more to the typical cinema horn installations with their impressive refinements in micro acoustic terms. Of course such a speaker is not able to show the same degree of micro acustic resolution, its physically handicapped to do so, but you never will ask for anything missing. A exceptional homogeneity, hard to obtain with such complex horn installations, has indeed more affinity to small scale full range speakers, but with a much improved dynamic ability. So these speakers do mark a full unique alternative option in size, living room ability and performed quality, last not least seen from the money point of view. The only natural predator in this league might be Voice of the Cinema-types of speakers, which would be from certain points no alternative for me...

The by now first manufactured samples are finished and are in deliver to their new owners. I have spend a good amount of time of the last year to find refinements for the production and manufacture process. The front loaded dipole enclosure is some sort of ultimate cabinet for the 15-inch Tannoy Dual Concentric speaker with the 15 ohm hard edged version of cone, i.e. Monitor Black, Silver, Red and Gold with 8 ohms. Almost any detail of my prototype cabinets got improved for the series production.
The most problematic detail is still the curved front horn extension. It is made from solid layers of 3 mm mahogany veneers, each glued to the next within a specially made press form, to a final thickness of 18 mm solid wood. Mahogany wood is a ideal material, since it is grown in long strong fibers, which will be bendable in a perfect way and will give the necessary elastic stiffness for preferred sound values. I still hope that FSC certified tropical wood is not only a placebo for the conscience of the consumer and will give some extended sort of sustainability.

Different stained fronts are available to customer requests

 The front of this speaker design is exceptional important design feature, since it is acting as a relevant extension of both different speaker units. The HF-compression part will be extended to lower frequencies, since the LF-cone will be supported in the important lower mid frequencies of 400 to 1000 hz. In the same time the fronts are acting as frontal part of the well known h-dipol design (original WE 7331), they need to mount mechanically the more than 10 kg heavy Dual Concentric speaker to the enclosure with all known advantages and problems. This is a highly delicate question to solve and one main issue bringing vintage alnico equipped Tannoy speaker enclosures into a refined singing mode. Within a misunderstanding of this little detail lots of generations of Tannoy speakers from last 40 years didn't reach their inherent built world class smooth expression.
The open back needs to be completely lined with 10 mm woolen felt in order to minimize direct reflections inside the cabinet, the extension cases are lined with low density boards. These extension cabinets are just movable only for transportation reasons to keep the enclosure sizes small.

Here shown with slightly stained and oiled oak veneer for the main corpus and dark brown
stained color for the extension enclosure in the back.

All veneers are thick types of minimum 2mm thickness to give the enclosures a robust surface
and a solid wood appearance since they are made from lumber core plywood, the best sounding
wooden boards for speaker enclosures.

Listening to these Tannoys shows a well expected improvement in the naturalness and liquidity of the  typical tonal impression, comparing these with my plywood cabinets. The coniferous solid wood inside sounds better articulated with less resonant edges in the tonal accuracy. They will improve within the next month even more, when they get played in, a process known well from a typical wooden musical instruments.

10 mm woolen felt is my preferred damping material inside enclosures, in order to minimize
reflections inside cabinets. pine strives of 10mm thickness add some controlled strength to
cabinets. These are arranged in proportions of the the "Golden Cut" to find the best dispersed
reconance distribution.

I was almost shocked when I did refurbish the first pairs of chassis with original "recone kits" supplied by Lockwood Audio. These typical preassembled units (paper cone with surrounds, centering unit and voice coil) don't make a lot of problems to the experienced and get perfectly installed into the well known chassis of the dual concentric loudspeakers. It struck me down when I did a first listening test after the reconing process, I was save about the fact that both high frequency units are defunctional. Even if I did measure them before, I stopped the listening test and reopened the tweeter for a second inspection. I was quite save that the didn't work by listening. But I was wrong, the paper cone was absolutely not able to perform its dedicated frequency ends, i.e. the lower frequencies below 150 hz, as it could not resolute the frequencies above 500 hz. So these units over roared with 200 to 500 hz frequency parts so loud, that it was impossible to hear the hf unit or some lower bass.

Variants of the enclosure in different stained color and again with retractable back.
This option needs a precise felt gasket between outer and inner case-

After almost 4 hours of first playing the music started to open up and was already sounding in a way which did remind me a bit to the typical Tannoy sound. After 50 hours play from radio they started to sound quite well, still with a reserve of resolution of 5 % to match. It will show in future, I think it  will need another good 100 to 200 hours till they will show their best attitudes.
As well the cabinets itself need a extensiv cuing in process very similar to wooden musical instruments. At the very early beginning they don't sound refined. Quite edgy and inharmonious in their musical behavior within the first hours, they start to brake in after eight hours play of music. After another 20 hours play in time, they show some first musical insight and convince with some first harmony distribution. I expect them after 100 hours playing time to reach their final exceptional transparency and harmony in a stage, where thy are already acoustically invisible. This process seem to be very similar to the run in process of wooden instruments. Interesting, normally when you build a speaker one time, you can not realize such effects. But if you listen to a new sample of your well known speaker, you are able to observe even the smallest changes.

The crossovers are made from copper foil inductors and oil-paper capacitors and solid 2mm copper wire. They have got a metal housing, close in design to the original crossovers known from the legendary Tannoy Monitor Silver and Reds. So I have spared no effort to take care about any technical but as well optical detail to match the original or better standard these speakers were known for. I think it might be a pleasure for the future customer to see how much attention has given into any detail of these speakers. Details which haven't been seen for more than 50 years from commercial sold speakers, even if they were manufactured in low amounts. I did try to make one of the best loudspeakers in history even better and keep its almost legendary standards to the highest possible level. Like several other recently issued remakes from history, like the LineMagnetic series of speakers or the Western Electric 15A horn replicas from Aldo in Italy, I try to manage a similar idea of reissuing with a main interest to a before unavailable quality with vintage Tannoy speakers. I am happy to present with such speaker a stage of improvements, which was never available before, nor it can be found in in their current own pricy legacy releases known as "Prestige Series".

Fresh reconed chassis are looking like new

Of course they have got the TrueFi logo
I prefer felt gaskets like known from the early Monitor Silver, better than the later
introduced high density foam in black or white (shown in one image above),
known from Monitor Red, Gold or HPD.

These speakers are available to order as complete loudspeakers equipped with refurbished Red units or can be alternatively equipped with own speakers from the Tannoy Monitor Silver, Red or Gold line. They can be made with different veneer types as they can be customized in several details on request.

It's always good to have some spare Reds in house, you never know what will
happen...As well some spare recone kits might give safety.

Read as well what other say who have listened to this speaker!

Sizes and technical informations:
95cm high to 60cm wide, with a minimum of 65cm depth variable extendable between 45 to 80cm.
Made from 18mm lumber core plywood, veneered with 2mm furniture veneers.
Funnel made from solid mahogany 3mm veneers.
All used solid wood from coniferus sorts between 1.5 to 6 cm strength.
Soft rubber rollers integrated in the base.
Total weight 52 kg each equipped with speaker and crossover.

Read on soon,