A Tannoy 15'' Enclosure for the Enthusiast – Part I

Hello to all interested people into Tannoy enclosures,

after I've already reported about the Autographs and even when the final contribution unfortunately is still pending, I would like to start a multi-part series on DIY Tannoy enclosures. For twenty years I have been building housings for these great vintage speakers, i.e. for 12'' and 15'' chassis. Such speakers with its powerful drive moments, their large mass and their strong magnetic drives need other housing parameters than most speakers today or what haunts the so-called literature since the speaker DIY boom of the 1970s. La Maison L'Audiophile, Auditorium 23, and many people from that circles, recently such as the Wolf von Langa have been busy about cabinet design principles of historic professional designs. It can not be said enough how important the conservation of the historic proofed knowledge is, if you want a quality product with exceptional abilities. Todays consumers don't need anymore loudspeakers, they are happy with earphones as lifestyle accessories.

So today, even internationally, the small group of people with high quality demands and exceptional high quality tube amplification chains concentrate on Western Electric products or its later successors of good availability from the Altec era. Asian copies of WE equipment give this incomparable products a wider availability again. One of my major interest was, when I did start this blog, to give the classic Tannoy speakers a auditorium of interests and exchange of informations. These speakers are unique in their design and quality, their typical sound is different from any other coaxial speaker made. The older vintage 16 ohm hard edge chassis are exquisite in terms of finesse and listenability, I think better than any other duplex speaker made. So they are much sought after in the asian markets (alone in Japan there are three companies existing with a huge production line of enclosures for Tannoy), but Tannoy don't have a wide acceptance in Europe, where they came from. One reason might be that the most people only have real practice with the latest models, the HPD line, which which was the worst incarnation of this speaker line. The typical Tannoy enclosures are made for private home use, since the company Lockwood made the professional cabinets for the use in recording studios, which was the main business profile and success. Since the death of Tannoys founder in 1977, when the company has been sold, japanese customers have bought Tannoy speakers in Europe for the export to Japan. A edition of 500 Autograph speakers have been made solely for the japanese market in the late 1970ties.

The most people I know with this speakers use standard original hifi-cabinets, which are generally not ideal. They are furniture products to fit the british home, instead of being serious music reproducers. They are made from particle wood boards with nice verneers, nothing to take care about. So it makes sense to improve on cabinet designs to work out the full potential of this exceptional speakers.

A lot Tannoy users are in search of optimized cabinets for years and try to do it themselves, mainly with the wrong concepts based on theories of small scale highly filtered loudspeaker concepts of the 1970ties or the diagrams published by Tannoy itself in this period. But big chassis with hard edged cones need completely different concepts work best. It does not matter wether this search is for the 12-inch or 15-inch chassis, the starting point is for most people the original cabinets to be modernized. The early cabinets from the 1950ties are so called vented port designs, but they are made from quite good materials, since they were developed through listening tests. The later ones from the 1970ties followed the reflex philosophy of Thiele&Small and are extremely rigid, damped to dead in terms of resonances and made from mdf-boards. Often due to their dissemination you will see Lancasters or their successors the Berkley cabinets, both generations have a rough volume of 120 liters. Many have chosen this cabinets because of their size as compromise for their living rooms. Both generations have had a bigger cabinet as brother, so the Lancaster had the Amesbury and the Berkley had the quite common Arden (image). Both had a rough calculated volume around 220 liters, a much better value than the smaller versions. But if you look at the qt-parameters for hard edged paper surrounded 15'' Tannoy chassis like the Golds, Reds or Silvers, you will see a closed 360 liter cabinet will do the job of a quite more linear low frequency response much better. Anything smaller sets compromises as a major fact, but who wants really such big cabinets?The Onken cabinets from Japan published in the 1970ties are a first step forward, but are still quit big. Or it needs to look for other ideas of compromise like open baffle?

A modern cabinet is more an instrument than a dead piece of furniture

A good cabinet is made from grown wooden materials, which will have a tremendous influence on the sound qualities, in particular if you handle such big motor units. For Altec users with separated HF-horns the "Voice of the theater A7" is a enclosure, which is a very good base of size to frequency response ratio (roughly 410 liters volume). These cabinets are known to be working very well, but are still a lot to big for the most of us and will not match the HF-horn opening for the Tannoy. The most of us would go further to accept some restrictions to shrink the volumes of a speakers to match their living room aesthetics. The well known wife acceptance factor WAF is the most compromising aspect to match a speaker to a living room as furniture. The most people I know want cabinets for their Altec/Tannoy/Vitavox/Stephens/University/etc. 15'' speakers, which will fit to such preferences, ideally not bigger than 200 liters with a furniture friendly design. Since we are not the typical aficionados or are living in Japan and accept rooms to be filled with hifi equipment, were you cannot open the window anymore. All others seem to have enough space/money to incorporate special listening rooms for their WE15 setups with two 18'' field coil in a suited baffle per side. I do not.

In this series I will try to show the detailed development of a 200 liter enclosure with integrated front loaded horn from the very beginning. Lot of the construction aspects are based on informations coming from the traditional music instrument designs. Uncountable tests about energy transmission of wood types, their resonant properties and construction secrets from guitars or violins, as well pianos, different conditions of dryness of the wood have been taken into account before the final wood will be ordered. 

For the beginning a test set up will be very helpful. From earlier tests with WE-compatible speaker designs I had a so called "dipole-enclosure" for a 15-inch chassis lying around with a quite suitable size for the first tests. It has ugly proportions with a 0,75x0,85m baffle size. Since its two identical parts were originally faced to each other before to form the H-dipole, one half is now only 0,30m deep. It is made from perfect materials, 25mm northern hemisphere coniferous plywood for the boards and stripes as strives from the same boards for the reinforcements. This enclosure has been originally made to act like a low frequency sub-200hz-cabinet with a 15'' speaker. For a hefty full range unit of the same size, I rather would use thinner materials like 16 mm plywood of the same type. From my experience the thinner plywood works better with the important transmitted 1000 hz frequencies, so later on I would do the real enclosure with thin materials. Other people tell me the same experience from the original "VOT A2-cabinets", which are made as well from 16mm plywood comparing these with modern versions.

I definitely wanted a front loaded horn to extend the lower end of the high frequency unit, like it is used in the Westminster enclosure or similar at the Autograph. I did use such a front loaded horn since two years in in front of my berkley enclosures. When I started to test the effect, I did make the funnels from gray card board of 2mm thickness. Since almost 20 years I wanted to test the loading effect at my speakers, but I never did that. When I realized the funnels two years ago, I realized that this was my biggest mistake I made with Tannoy speakers during all that time not to go for "front loaded". It has an amazing positive effect and completes the unique design principle of the Tannoy speakers in a perfect way.

Berkley cabinet made from medium density particle boards with card board funnel for testing.
On top the new made wooden funnels for the new cabinets to be made soon.
at the cut out for the crossover the little switch can be seen were it can be switched to full range mode.

Were the cone completes the HF-horn, the funnel completes the cone further on. But this construction needs the customizing of the crossover, otherwise the effect does not do the trick. The funnel works like a mechanical amplifier for the distributed frequencies and it extends the high frequency horn for a lower cut off. I have never made measurements, but it is clearly noticeable, that the frequency between 400 hz to 1000 hz will be distributed. The speaker sounds  a whole lot more naturally detailed with a much better HF-dispersion. The illusion of space is wider and deeper, so the amount of listenable air in the recording grows dramatic. For me this effect is always a sign for a remarkable quality upgrade. I copied the funnel of the Westminster design. Both, the Westminster as well the Autograph have customized crossover designs in order to integrate the extra energy of the middle frequencies. Both designs open up the frequency cut off around 1000 hz to higher cross over points. 

Test cabinets with 220 liter volume for a 15'' Tannoy speaker with front loaded horn extension just screwed to the baffle

I did work out through the years something completely different. Coming from my personal preference of the smaller 12'' units of the Monitor Red and Silvers, where Tannoy coupled the cone as full range units, I tried to do the same with the 15'' Red recently. In combination with a front loaded horn the speaker just did struck me down by its shear energy distribution and much more colorful tonal spectrum of the middle frequencies. I use my 15'' Monitor Red as full range unit, while the HF-unit gets cut below 1000 hz with a soft 6db filter. This filter is made with oil paper caps and copper foil inductors with wax isolation. I still have the classic 1000 hz filter for the LF-unit built in, I did it switchable, so I can test it always in different enclosures, but for me the full range set up beats all other options. At least my favorable sound option of the 12''-chassis was just the full range option of the cone and did not have anything to do with the size of it or any better sound qualities arising.

Read on soon about my first impressions, Volker

Jaqueline du Prè – A Cellist Without the Same

Hello everybody,

I would like today, different from my previous practice to present classical music. As well in the classic music genre examples can be found which are for me incomparable musical moments. So I've always been interested in the different interpretations of the cello play. In particular, but it is the supreme joy of incomparable Jaqueline du Pré, which I would like to present here with some essential records today. Due to her early tragic life end, the list of original recordings on vinyl is short, all first releases were published with EMI or Angel label for the US-market. The Edward Elgar's Cello Concerto with Sir John Barbirolli and the London Symphony Orchestra was her first recording in 1965, which established her fame arose (LP record can be seen lying in the back).
Other recordings of the major cello concerts and an extensive concert career followed on. As well a lot of chamber music was recorded in the first years. One of my favored records is the exceptional take with Stephen Bishop for the Beethoven cello sonatas (LP lying in front). Very typical for du Prés play is the incomparable vitality and the playing pleasure, which is in this case more than exceptional. The recording gives a deep intimate insight into the music and delivers a exquisite conserve in terms of dynamics, presence and energy of both performers. With good play back equipment it will give a reasonable illusion of the live event in your listening room. Something which is almost impossible with greater orchestrated pieces like a symphony. The sheer mass of the instruments, i.e. amount of moved air and the size of the location is impossible to capture with hifi.

Through du Prés friendship with Daniel Barenboim, Itzhak Perlman, Zubin Mehta and Pinchas Zukerman, the famous film by Christopher Nupen on Franz Schubert's Trout Quintet was formed. In 1967, Jacqueline du Pré married the pianist and conductor Daniel Barenboim. Their marriage was the basis for a fruitful musical collaboration that can be proven as a pianist or conductor through many recordings with Barenboim.

Jacqueline du Pré was born at the 26th January of 1945  and died at the 19th October of 1987 in London. She grew up in a musical family - her mother was a pianist and piano teacher - and at the age of five years showed interest in the cello. At the age of ten she studied with William Pleeth as her main mentor. She studied as well in the following years with Pablo Casals, Paul Tortelier and Mstislav Rostropovich. In 1961 she received a Stradivari cello of 1673, which is now called "Du Pré Stradivarius". Since 1964 she played on the "Davidov Stradivarius" of 1712. Both instruments were gifts from her godmother Ismena Holland.

In the fall of 1973 she was diagnosed with multiple sclerosis. Then she occasionally worked as a teacher until her health deteriorated so that she could no longer perform and died at the age of 42 years. Only a few records were published in that decade, but some of these are some of the best interpretations of the 20th century.

Read on soon about other soloists, Volker

Yma Sumac – Exotica on Vinyl

Yma Sumac was born as Zoila Augusta Emperatriz Chávarri del Castillo on September the 13th 1922 and died November 1st 2008. She was a Peruvian soprano. In the 1950s, she was one of the most famous proponents of exotica music. She became an international success based on her extreme vocal range, which was said to be well over four octaves and was sometimes claimed to span even five octaves at her peak. Yma Sumac recorded an vocal range of slightly over four octaves from B2 to C♯7 (approximately 123 to 2270 Hz).
Stories published in the 1950s claimed that she was an Incan princess, directly descended from Atahualpa. Her New York Times obituary reported that "the largest and most persistent fabrication about Ms. Sumac was that she was actually a housewife from Brooklyn named Amy Camus, her name spelled backward. The fact is that the government of Peru in 1946 formally supported her claim to be descended from Atahualpa, the last Incan emperor.
Chávarri adopted the stage name of Imma Sumack before she left South America. Yma Sumac first appeared on radio in 1942. Sumac and orchestra and bandleader Moisés Vivanco were married that year. She recorded at least 18 tracks of Peruvian folk songs in Argentina in 1943. These early recordings for the Odeon label featured Moisés Vivanco's group, Compañía Peruana de Arte, a group of 46 Indian dancers, singers, and musicians. In 1946 Sumack and Vivanco moved to New York City, where they performed as the Inka Taky Trio, Sumack singing soprano, Vivanco on guitar, and her cousin Cholita Rivero singing contralto and dancing. She was signed by Capitol Records in 1950, at which time her stage name became Yma Sumac.

A variety of Yma Sumac's first releases from the Capitol range in the 1950ties

During the 1950s, Yma Sumac produced a series of lounge music recordings featuring Hollywood-style versions of Incan and South American folk songs, working with the likes of Les Baxter and Billy May. The combination of her extraordinary voice, exotic looks, and stage personality made her a hit with American audiences. Sumac appeared in a Broadway musical, Flahooley, in 1951, as a foreign princess who brings Aladdin's lamp to an American toy factory to have it repaired. Capitol Records, Sumac's label, recorded the show. During the height of Sumac's popularity at the peak point she released "Mambo!" in 1954 as 10 inch album with Capitol. From todays point of view her most eccentric album of all her carrier, so it does not wonder that it is used to represent her web page today. Its mixture of south american folk elements with popular band arrangements typical for that period and a intonation style of the classic opera songs make her unique voice at this album a true legend. If you want to own a Yma Sumac album, this is the one which goes beyond all others and the must to have. Later she appeared in the films Secret of the Incas (1954) and Omar Khayyam (1957). She became a U.S. citizen on July 22, 1955. In 1959 she performed Jorge Bravo de Rueda's classic song "Vírgenes del Sol" on her album Fuego del Ande.

Apparently due to financial difficulties, Yma Sumac and the original Inka Taky Trio went on a world tour in 1961, which lasted for five years. They performed in 40 cities in the Soviet Union, and afterward throughout Europe, Asia, and Latin America. Their performance in Bucharest, Romania, was recorded as the album Recital, her only "live in concert" record. Yma Sumac spent the rest of her life performing sporadically. As well later record releases had been rare and can be summarized as exotica in a strongly commercially classified music business. 1998 her music was part of a feature film by the Coen brothers, The Big Lebowski and the Cirque du Soleil show Quidam. In May 2006, Yma Sumac was awarded the main peruvian medal for El Sol del Perú. The same year, her song "Xtabay" became soundtrack of the German film The Austrian Method.


Read on soon, Volker

notes: most informations are from wikipedia and her web page.

Mazda TM2 – A French Military DHT

Military or post tubes are generally designed for long life service, independent from country of origin or dedication of use. So the early direct heated triodes for different professional applications, mainly for wireless systems were designed for long term flawless operation, compared with their standard consumer replacement types. Today I want to present a quite rare tube type manufactured for the early french military amplifiers (Télégraphie Militaire), the TM2. Made by Mazda this tube is technically almost identical to several civil types, like Phillips A409, A410N or the German RE 084 from Telefunken. Different to these equivalents the TM2 has a solid fixed metal shielding and a isolation made from foam underneath. The typical sensitivity for shock or electromagnetic stray fields of the direct heated tubes is minimized a lot. Together with its low heater consumption heating system of 0.08 ampere at 4.0 volts heater power, these special parameters make this tubes a wonderful device for preamplifier concepts. Comparing this tube with other DHT-Tubes like the 26 or 801, the low heater consumption makes the TM2 a very good alternative, because the heater power supply can be designed a lot simpler with several improvements in the daily use. The tubes are equipped with the typical european 4-pin socket B4 and their quite low Plate resistance make the tubes a very good alternative to other DHT's, because they can be implemented very well with output transformers available from the standard catalogue of the most brands like Lundahl, Tango, Tamura.

For people who are interested to see the inner construction of the TM2 here at Jogis Röhrenbude you can see it stripped down.

Keep on reading, Volker