Musical Instruments in Audio – The Headshell

Everybody who has driven down the hifi road for several years knows immediately what I mean if I talk about the sound influence of different materials. In analog audio components mechanical energy is stored and as a result the ability to damp this energy has a profound influence to its sound character. In the earliest stages of a analog amplifying chain this influence is a lot more obvious and listenable, because the signal is very small and the proportion to the resonances can be quite big. In later stages the ratio gets better in favor of the signal strength. In reversal to this fact it means that materials with different resonant abilities will have at the beginning a more massive influence than in later stages.
The earliest stage of a analog audio chain is the pickup cartridge and its mounting to the tonearm, the component were the electrical signal is created. Any sort of cartridge will be exposed to tremendous mechanical energies arising from the excursioned grooves, a process which inserts energy through the diamond to the cantilever to be introduced it into the arm wand, together seen as a complex compound. In an article published in the early 1990ties in the Swiss magazine Hifiscene the energy at the cantilever was figured with almost 5G at a 33 speed and a 30 Hz peak. I do not know if this is right, but if you have listened to a diamond in the groove without any electrical amplification, just the mechanical resonances, I believe the energy must be enormous. At this point it starts to be understand, that a higher mass (of the arm) and a lower compliance might have positive benefits to handle this energies. A pick up cartridge with low compliance of 8x10-6cm or lower handles naturally the bigger mass of a stainless steel tone arm wand better than a high compliance cartridge can do, since the whole systems has much more damping mass. Therefore the resonant energies are a lot better controlled than a low mass system can do. In the 1970ties it was understood that a lower mass does not support such resonances thoughout. This misinterpretation have created thousands of high compliance cartridges and high tech light weight tonearms in order to bypass that handicap with a lower mass (and less dynamic soundstage as result).
Today we know better, this handicap is as well a big chance towards a more natural response. A wider spread tonality, by far better dynamics and a deeper and wider soundstage are the benefits of a good implementation of a low compliance cartridge into an a heavy mass tonearm with controlled resonances.

A range of headshells I did evaluate within the last years, from top left: Denon original broadcast headshell (plastic); 2nd row: Ortofon Gold aluminium G-headshell; Diy thick-walled headshell zebrawood; standard lw-headshell; 3rd row: vintage Ortofon bakelite G-headshell; diy zebrawood A-headshell;solid lightweight headshell;  4th row: diy G-headshell zebrawood; casted zinc Lenco headshell.

Outgoing from these facts I would like to talk about my experiences with different headshells and their materials in combination with such a converted SME 3012 high mass version. The heavy and stiff stainless steel arm wand will bring cartridges with less than 8x10-6cm compliance into perfect physical balance and its internal balsa wood damping helps further on to prevent ringing which is always obvious in tubes. So these cartridges can produce their best possible fine and coarse dynamic soundstage combined with the highest stage of musicality. Cartridges like the Ortofon SPU, the Denon DL103, the EMT, the Fidelity Researchs, the Koetsus and the Ikedas will profit enormous from the heaviness for damping the arising resonances. So far – so good. I started decades ago to evaluate several of these cartridges and decided like a lot of other people to use a classic Ortofon SPU (with sperical stylus tip) as my standartd pick up cartridge. At these times Decca FFRS and Denon DL103 were in competition in my home system. A lot of my friends did use as well Platine Verdier turntables as I do till today, but in these times they all did use the Shindo modified Ortofon tonearms, which have a slightly different geometry than the classic SMEs. They used the SPU in the shorter dedicated A-type headshell, I did use of course the classic G-type headshell with my standard 3012/II. My friends always stated the A-type to sound better. I could not compare both versions in these days in my set up. To me it always arised a main question: will a square shaped closed box design, like the Ortofons have a principal advantage to the open standard light weight shapes (or its perfect derivate Orsonic)?

Typical vintage Ortofon G-shells, left (hardly corroded aluminum), right bakelite

In the middle 1990ties I got a first vintage SPU with elliptical stylus tip which I did like better than my quite new one with spherical tip. The all around warmer character of the older cartridge I preferred in almost every aspect of presentation of sound. Some years later a friend of mine brought a SPU gold (limited edition from 1980ties with elliptical tip and silver coiled generator instead of the ordinary copper version) to my house. I tried it and I liked it as well a lot, it had a bit better resolution of the higher frequencies than any other SPU-version I did know. I thought it must have been due to its silver coils of the generator. With ebay in the middle of the 1990ties it got very easy to find used SPUs online, mostly in the UK. So I got the next vintage one with elliptical tip. I tried it out and indeed it was very nice in a different way, very warm and with fine resolution and with perfectly integrated extended higher frequencies.

Very untypical, the SPU Gold in the bakelite shell on top, and the standard SPU in the Gold shell. I added a extra weight into the bakelite shell to compensate different total weight for direct exchange.

I compared both vintage cartridges to each other and I realized a good portion of differences. Looking at both cartridges in my hand, I realized one had the typical casted metal G-headshell and the other came in a earlier version made from bakelite. To make it safe, I switched both cartridges in their headshells. It was absolutely obvious, that the bakelite headshell made the difference of a smoother presentation. We made the same test with the A-type cartridge of my friend (the A-type headshells are always made from bakelite), he had now as well the adapter to compensate the length difference for the SME arm. The same result, the differences between both types of bakelite headshells was to negligible. It is not the smaller size, i.e. stiffer design, it is just the material itself, which creates the difference. Now I did understand why the A-type is so much higher rated. I would go as far as to state, the headshell material has a bigger influence to the final soundstage of a SPU than the shape of its diamond.

But this experience brought me to the next question about other materials to be used as headshell instead the bakelite. Obviously the bakelite material and its stronger wall size did damp the resonances of the cartridge better than the casted metal type. It seemed to resonate in the higher frequencies parts and creates a all around lighter and a bit harsher soundstage. My arising question was: How would wood change the sound of such a headshell? For the widely spread Denon DL103s there were already some after market products available made from ebony wood. For the SPU in these days there was nothing made from wood, just the original three types from Ortofon. I decided to make my own headshell from wood to test it. Best material would be some northern coniferous wood sorts, but the long fibers with lots of resin is mechanically not a good material to be milled to that fine wall sizes. Instead I did use a long fiber tropical wood to test it out, african zebra wood. I would have liked ebony, but I could not get rough sticks of that size. So I milled almost three headshells which I ruined by doing. The fourth was the first one with thin enough walls (almost 1mm thickness). I started with the classic G-type design. When finished, I was trained enough to make as well a shorter A-type shell in order to compare both types with their bakelite equivalent. As in the original Ortofon design I used for connection details inside brass parts and screws.

The first impression was quite good, but by far not that good as I did expect before. I tested the G-type first. It produced hefty resonances in the important middle frequencies, I would appreciate around 1000 Hz. This is the by far the most difficult part of the tonal audio spectrum. It is the region were almost every instrument and voice will be covered. I did stop very soon and decided to make a second try with a approved design. This time I milled the shorter A-type design in the hope that the shorter body will not give the same resonances than the long bodied one. I did understand that typical Ortofon design to work like an wooden boxed instrument with its four sided walls. So I tried to mill out the inside more than the first one and with respect to thinner wall sizes of 1mm. I thought as well about constructing a chamber from 0.8mm panels instead of milling a massive piece out, but decided for a increased connection design. For me it was a real mechanical challenge to get it made.

But the new shorter type did showed almost the same resonances. To be honest the difference to the thicker longer version was not listenable. I was really sad, because I did like the look and feel of the wooden headshells a lot. But my ears did tell me a total different story. By far the bakelite headshell was my favourite one, a lot smoother, refined and still more dynamic than anything else.
I did do another series of competions with the original professional plastic headshell from Denon, the heavy casted metal headshell from vintage Lencos and finally the very solid open frame types from the 1970ties. To make it short, the bakelite headshell from Ortofon is the thing to go for. It is in every respect a lot better than anything else. The box type design is stiffer than any later design (skeleton, light weight, etc.). I missed out any tests with C-37 laquer, as I did not set a golden clamp at the arm wand for further improvement... ;-).

Because I like the SPU Gold with its smooth fine extended resolution of the higher frequencies as best SPU pick up, I transfered it into a vintage bakelite headshell for my everyday use. I have owned almost every classic low compliance moving coil cartridge in history (as well the rare early Grados), I did try several moving iron types (Neumann DST, Decca FFRS), as well the early low compliance moving magnet types from Fairchild and Elac, but I have settled down with a SPU Gold in bakelite case. I have stopped thinking about other pick up cartridges, even if I would like to listen to a selection of different cased Koetsu cartridges made by the passed away master Sugano himself. He must have made very extensive experiences, otherwise I cannot explain to myself all the different materials he did use with his cartridges? Or was it just a japanese sort of attracting people with some bling bling? I might survive without knowing exactly...?!

Read on soon, Volker

Sony PUA-114 Tonearm converted to 12''

Hello to everybody. My speakers are still in work, so they are not ready for the public viewing. Instead I want to show a conversion of a unknown high quality japanese 9 inch tonearm into a 12 inch version. For this conversion I did use one of the arm wands from my SME conversion kit.

I had this japanese Sony tonearm lying around for years. I did buy it once because it has a mechanism to adjust the vertical tracking angle on the fly, it can be made during the pick up process. There is a knurled round plate just under the bearing to operate a thread, which will rise the whole bearing shaft up and down. Only a few very expensive tonearms give this luxury extra as option. So, what is the idea behind such a mechanism? If you use different moving coil cartridges, each needs to be exactly mounted into its perfect position to give its best result. Perfect geometry of arm and cartridge is the one thing to reduce errors of the pick up process. But the vertical angle varies the angle of the diamond tip in the vinyl groove. This angle has some influence into the ability of the best high frequency response which is obtainable with a given angle. So a changeable angle will result in more or less a perfect position of the diamond, i.e. in a more or less better defined high frequency response of a cartridge.  All cartridges are normed for a 15° angle in relation to the record surface. So this option gives some extra opportunity for adjustment of the response of each cartridge. If a tonearm has this option it will be very easy to match a pick up into a system just by listening evaluation. The classic heavy arms from SME, Ortofon, Fidelity Research and Ikeda do not offer this option.

This extra was my basic interest when I bought this arm some 10 years ago. But I never tried it with my turntable. Since I have the conversion kit to offer, I was thinking I should try this tonearm once. But first of all it needed to be converted into a 12 inch length.
For that reason the original s-shaped 9 inch aluminum arm wand got detached. The most japanese tonearms do fix the arm wand to the bearing house with one or two screw, here it is made with two worm screws from underneath. The SME armwand has a outer diameter of 9.5mm, almost all tonearms did follow more ore less this size, only a few tonearms use thinner tubes of 8 to 9 mm size. As well here the 9.5mm did perfectly fit into the bearing house. This is milled from solid aluminum with more than 2mm material surrounding the tube fixing.
When I dissembled the bearing house, I was surprised about the built quality of this arm. A lot of japanese mass arms incorporate the two tipped bearing principle with steel tips. Here the tips are counter positioned into micro ball bearings with stainless steel end caps. These little bearings (2mm outer diameter) are precisely positioned in caves, which are milled into the center shaft. So the depths of the tips need to be fine adjusted with a tension tool. The tips itself are made from chrome plated polished steel. This mechanical principle is only found in fine crafted tonearms, other than ordinary tonearms mounted on turntables from the typical mass suppliers.

The headshell connector on the other side of the arm wand is fixed with a little screw from underneath, similar like the typical SME arms from the 1970ties, but the screw is positioned some millimeters closer to rim of the tube. This made a cut necessary to adjust the difference, which will result in a 3mm shorter arm geometry, comparing the SME 3012 size. The effective length between center of the shaft and pick up diamond is now 302mm instead of 305mm of the 3012. I think it can be lived with that loss...

Another problem might be the new heavier weight of the arm tube. So the counterweights are a bit underrated for that tube, but if necessary, it is possible to add extra weights for compensation (Sony did offer a additional weight in the 1970ties). Of course I did use the balsa inlay to damp any ringing in the tube and I did use silvered copper litz for the signal connections inside. For a propper set up it would be necessary to make a solid base, where the shaft will be clamped in and were the whole arm will be mounted to the player. If made from a round bronze bar, like used for heavy metal shaft bearings would be the ideal choice.
I did some test without this stage of perfection, just to figure out were this arm will find its ideal use. It was no surprise that it would give a extremely precise imaging of the music, comparing it with more simple designs (like the knive edge of the SME). The other side of this medal is always a bit of the lack of sheer dynamics other arms can show. This arm might improve in this discipline with a better base construction. But never less, it is a 12 inch tonearm. It has a wide stereo image and a giant depth of stage illusion, 9 inch arms don't come by. Together with its possibility of VTA adjustment on the fly, it is the perfect tonearm for people which want to evaluate several different cartridges in their system. To find something similar in terms of comfort and in this range of quality, you need to spend some more thousand dollars.

If there is somebody out there, who might have an interest into that rare tonearm, I will be open for any reasonable offer to sell it, of course without the nice bakelite headshell and the pickup.

Stay tuned, Volker

Trio EM – Eva Kruse, Michael Wollny, Eric Schaefer – Jazz for the Next Generation

Last year in February a friend of mine asked me if I would like to come over and visit a small jazz festival in the city of Essen. He was set into interest because of his trumpet teacher, who did act with a band there and he had recommended this little jazz festival. Without being personally involved I was in the first stage a bit reserved about going there. But I got persuaded to visit and at some saturday night in February the event did take place. The concert was opened up by a very young quartett of musicians who all had found together after finishing the quite well known Folkwang Music School. They played some moderate "resumee-jazz", a bit from all directions without any real emphasis. I started already to regret being there, in particular when I realized to see another two songs of this young band.
The next band was a quintet (here my friends trumpet trainer played himself the horn) with typically well known influences from the 1970ties as some sort of rock-jazz-crossover. I never was a real fan of rock music, nor did I like this sort of typical mixture with classic jazz elements from the bop era. I noticed after the second song that my interest did fall against zero and I would have fallen asleep, if the pa would have been not so loud. My friend told me in the meanwhile, that the third band of this evening, a young trio from Berlin, has a very good reputation already and that his trumpet teacher does not only know them well, but likes their music a lot. Ok I said to myself, I hope I will survive till the end of this evening, it already had got 22:30h. A good half hour later the last act of the evening started and on stage were three young people in their end twenties setting up a classic trio with piano, contra bass and drums. When they started it did not take longer than 10 seconds for me to be back completely alive and able to immidiate that there something extremely good and very exiting new happened. There was a presence of energy with all three, which did overcome me completely. Now I did feel very well again, my feet snapped and my brain started to relax, I could enter into the mood for the first time at that day. Trio EMs music has a very intense energetic drive as a typical component. This energetic drive is a result of a deep percussive understanding of each musicians instrument. Eva Kruses bass is often setting the pace, were Eric Schaeffers percussions add rhytmic structures and Michael Wollny often turns the piano into a giant percussion instrumentation. I have never seen a pianist sitting so agile and limber at the keyboards, he is extremely nimble and shifts from explosive maneuvers into sedative passages back almost lying completly in the inside of his piano plucking the strings with his fingers and beating them with the his underarms.

A small selection of CDs from the last couple of years, but there is a lot more to find out.

This music was some of the best jazz music I have heard in my live due to the incomparable performance all three are acting. At this evening they played four or five acts and I went home completely satisfied from what I saw. I was so convinced that I would rate the trio as one of the best jazz acts for years. Immediatly it did buy all existing recordings and went to three further live acts. When I did "google" them I found out that they had been rated in 2011 as best young jazz act since 25 years by the Süddeutsche Zeitung. This is the first time in my blog that I show work released on digital media, if you are looking for contemporary music, there is no other chance. At youtube you might get a good impression about their phantastic work.

In the meanwhile Michael Wollny is a rising star in the jazz world, he brings out lots of records were he  acts together with other musicians, and it is not allways jazz, he is trying some unusual crossovers to new music and other conceptual ideas. For example the work with Heinz Sauer and Wolfgang Kühn is exceptional as well the CD shown called "Wunderkammer XXL". I think he is one of the most interesting musicians of todays music scene without any category.

Stay tuned, Volker

The motor unit part II

Hello to everybody, sorry for a long delay with this new entry but my other activities and two fairs have  catched my complete attention within the last two weeks.

Today I will extend my former article about my motor unit for the Platine Verdier turntable with a new and easier to built round housing. A friend of mine uses two Platine Verdier turntables at different appartments in very similiar set ups. He did ask me for almost a decade to get a nice looking motor housing, similiar to mine since he followed my observations about different motor concepts. He ended up all the years with stripped down Thorens TD160 record players, without tonearm as motor units for both of his set ups. Mostly jacked up with books or card board crates to level the platter height of the Platine Verdier (minimum 22 cm, which is a lot). It looked always a bit like a neglected disaster zone beside the wonderful reduced crafted materiality of the player. Recently he burnt down his Valhalla board which I had built into his Thorens some years ago.

So when he brought the Valhalla board for repair, I thought about a way to build up a nicer looking housing as a complete integrated unit. Ten years ago I had to rebuilt my housing two times from casted concrete after accident, I decided almost never to do it again. The amount of work is just to much to make it again. Since I am in the process of bending plywoods for the front loaded funnels for my new Tannoy cabinets, I thought it might be possible as well here to bend a round housing for the motor unit, but the radius is a lot smaller. So its is a lot more difficult.

With a diameter of roughly 30 cm the wood has to be bend to its physical limits. For this reason I did use bendable plywood of 4mm thickness. In its technical specification it is determined to a minimum diameter of 26 cm. But the tension in the wood at this diameter is enormous, it can be bend but it needs to be fixed extremely solid within this position to glue. So I used the same outer round cast mold, which did use for the concrete casting a decade ago. Inside this mold I did bring three exactly cut layers of 4 mm plywood into each other, so that the single layers stabilise the others just by their own tension. It needed a lot of tests to cut the exact length of each layer so, that each layer slipped nestles into the next without any air in-between and the tensions adjust the sandwich perfectly. In order to get 9 cm height I did glue 11 cm wide stripes of almost 1 m length into each other. Finally, after drying out the wood glue, I could cut the ring on the table saw to its ideal height of 9 cm.

  

After building the ring I needed to to make a base and a cover to form a housing. In this design I wanted to reduce the mechanical outlay and I did it without the spring suspended subchassis my unit uses. I decoupled the main center bearing from the motor resonances just throughout the materials. The bearing is solidly set into the main construction with a massive wooden support, since the motor itself is just mounted to the 4 mm plywood top cover. Inside the housing acts like a chimney for the warm air, where the valhalla board is mounted in the center. The heat radiation of the power resistors is enormous and therefore it needs a good heat transportation inside. The most of the inner cavities can and should be filled with quartz sand in order to get mass and weight into the final unit. The filling is necessary due to the housing design, which acts more or less like a guitar or violin, with all positive and negative side effects. The unit can be adjusted to find a optimal height position for the string. A guide winded from spring steel keeps the string in central position of the platter. This guide is a must, otherwise the fine mono filament string will wander off the platter immediatly!

If somebody out there is interested to get a motor unit like this, feel free to contact me. If you are physically located close to my place in Düsseldorf I would be happy to show the advantage of this motor comparing it to your dc-motor unit, which is commonly used with such record players. Feel free to arrange a listening date.

Read on soon, Volker

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

Today I want to talk about the first few weeks of experience with the test cabinets. At the beginning I had difficulties to displace the slight bass boost of the Berkley cabinets from my listening habits. A fuller tone is also easier at the ear even by a skilled listener rather than a light-footed to vote. Even if one knows about the wrong tonality, this vote is more popular as a less woolly, faster and deeper -ending low frequency support.
I've never measured it, but probably the 120 liter net volume of the Tannoy cabinets ( i.e. Berkeley, Lancaster)  have a strong boost in the area between 80 and 150 Hz. This boost had now given way by the open cabinets to a much more linear performance. After a few days I liked the newly acquired qualities, such as fast transient response and by far deeper resonance frequency noticeably better than my usual set up. I started to prefer the dry fastness as new and rarely to obtain quality, which is almost impossible to realize with a ducted port design and is in theory reserved to the horn principle. Acoustically I never was a fan of the sound compromise coming from the "resonator theory of Mr. Helmholtz". But in normal rooms with its typical modes it is very difficult to realize a good low frequency response with sealed cabinet designs or with alternative concepts, which in theory might do better. Everybody who knows a little bit about low frequency horns, might know the life task to realize a design sufficiently working...

Both above images show private horn installations in order to get the fastest and best LF-response possible.

With my new and ugly cabinets I started my personal "open baffle"-concours, the first time with 15" Tannoys. The open baffle principle has got very popular again in the last two decades with lightweight vintage 8" radio console speakers, due to their cheap costs, its easy realisation and quite musical results. This wide success is not only a triumph of simplicity, but as well a clear statement about abilities of commercial standard 2-3-way hifi-speakers sold for real money during the last 30 years. On top of this there are some extremely nice speakers in the 8" full range category, which are playing in the top range independent of size. The legendary WE/Altec 755 line, the long time favorites from french Supravox and the their modern equivalents from PHY-Salabert. All of them find a perfect home in open baffle designs and are able to deliver an extraordinary musical performance with a positive reduction of complications other principles contain. Crossover design, massive resonant energy and physical size are named for a lot more complex questions to solve with bigger speakers or frequency divided designs.

Using a 12" or 15"-speaker of the 10-15kg weight range in fullrange mode with casted frames and solid magnets in open baffle designs is another challenge. Where a 12mm plywood board will do the job with small drivers, it needs here some more rigid materials and a clever design to work best. A typical 8" full range chassis will work with good results in the range of 150-8000 hz just mounted to a relative small thin board. If we want to bring a 15" chassis to support a medium frequency horn up to 200-300 hz, some old cinema designs give good advice. But If the 15" driver acts like a full range driver up to 4000 and more Hz with its inherent mechanical energy it is another question. Now the most important frequencies from 500 to 2000 will be transmitted and react with the resonant properties of the baffle design. Now it is going to be delicate and will act like an wooden instrument and other terms like solidness and size are in account. Harmonic properties are requested, just mechanical strength is the half truth to come by.
A look back into history helps a lot. Companies like Western Electric, RCA, Klangfilm and Zeiss have realized their early cinema systems with baffle designs for the low frequency support.

WE-cinema installation with three 18" field coil drivers

WE-ASO8122 design schematic, roughly 2,40m h  x 2,70m w with funnel for a 12" speaker.
With this overall size the speaker should be able to work down to 50 hz. 

In the above drawing the design and construction principle of the baffle board it is clearly visible. It is made from 25mm pine plywood. These boards are highly reinforced by solid pine thick boards of 5 x 5 cm. The alternate positions of this strutting is precisely considered to prevent resonances in every part of the boards. The single boards are systemized to be screwed together to build up to final size. A overall size of 2,40x2,70m should get the system down to 50 hz, before one of the two dipolar waves will extinguish the other.

Here in my set up the cabinets act like a folded open baffle board, with a minimum distance of 125 cm from the front cone edge to the back side of the cone. It sounded almost complete, I did not miss a lot of the deeper frequencies. So I did screw 25cm stripes of plywood boards in order add depth to the frame, so the total length added to altogether 175 cm. This might have set the frequency cut down to around 60 hz. It has brought a little more increased fundament into the sound structure, but as well supported the lower mids. Since I have realized this step I am thinking about a complete inside case sliding into the outer case, which might give the perfect adjustment for the LF-resonances to couple to the room modes.

More about that ideas soon, Volker

Harmony – Aspects of Technically Reproduced Sounds

Today I want to introduce a entirely fundamental questioning about qualities of speaker cabinets in sound reproduction. Under the influence of the evaluating my actual test cabinets a long time covered questions arose again. For years I am in the process of finding answers about timber woods, acceptable resonances and construction details of different loudspeaker cabinet design principles. Is there a relationship between the used materials and their harmonic properties? Does a speaker sound any better when built into a housing designed like an musical instrument? How does it compare against a technically advanced design aimed to reduce all resonances by the use of compound materials? Are directed resonances and inherent  harmonious effects superior than multi layered compound materials or even as far as dead damped materials? Let me ask in this specific case, does a speaker sound in a piano case more natural, subtile and more expressive as in a dead damped box? Is it even similiar with wooden instruments that certain types of wood in combination, their optimal growth, location and age, the degree of drying can harmonize a perfect housing for a moving coil cone speaker unit?

I think yes, these issues are important – indeed critical, and their optimized implementation can significantly improve a speaker cabinet dramatically towards its natural sounding capabilities. This actual understanding stands in contrast to the fundamental research project BBC RD 77/3 of classic loudspeaker cabinets done by H.D. Harwood for the BBC research department in 1977. This research was based on the speaker designs exclusive developed for the BBC in the late 1960ties, were companies like Rogers and Spendor have built several speakers for monitoring use like the BC1 and the well known LS-series. This research has build rails for the classic school of british loudspeaker design, commonly known as two way systems with small scale drivers (KEF), small baffle, rigid enclosures, complex crossover design and at the end highly inefficient properties.

Cabinets for BBC LS3/5a (30x19x15cm HWD )with synthetic foam damping

Less resonant materials have been researched, compound layers, even sometimes doubled with sand filling and highly strengthened constructions to find the acoustical "dead case". No wonder that cabinets made from three inch concrete came into account, just "to give resonances no chance". It ended up, as everybody knows with dwarf coffins, shoe box size speakers and 5 kg filter units for the crossovers (LS 3/5a, etc.) – loudspeakers with off-trained attitudes – sound generators with the need of 200 watts class a power to work with decent dynamics. Todays studio speakers have taken the relay race.

This is going to be a discussion between two contradictive positions, "the precision engineered system" and the traditional crafted musical instrument. We are talking about the technical advancement and its reliable proof by measurement, as we talk about the down passed traditional knowledge from generations of crafted masters over centuries of acoustical hand built instrument production at the other side. We are talking about the believe in technical advance and its opposition the faith into the higher order of natural superiority. There is no high tech stradivari nor a electronic enhanced piano known, able to displace this classic acoustic instruments. I cannot recall lots of arguments why a subtle harmony distribution should be different with loudspeaker cabinets?

Today we are looking back again to that time of the early beginning, the time were Western Electric, RCA, Klangfilm and others developed systems for professional use in theaters and cinemas in the late 1920ties. We are looking back to that time of inventors, were the difficulty of lacking amplifying power was confronted with the need to match the size of several thousand people filling halls. The shear physical demand of loudness made the mechanical support of the amplification necessary. Wood was the material of use to form funnels, cabinets and baffles for this reason. These inventors used constructive timber to strengthen their designs, northern coniferous wood sorts like they were used for other construction in other fields. They evaluated their designs by extensive listening tests and refined the results step by step. The designers did not have the opportunity to use modern composite materials, so they used solid timber wood and traditional wooden conjunctions to strengthen the constructions.

Today listening to such a system from Western Electric or Klangfilm shows us a lot about that principles. These huge size systems work with resonances and other side effects. Their tonality is colored and expressive, but they bring us a lot closer to the distribution of harmonies like the natural sound of acoustical instruments and its energetic content than contemporary solutions can do. Almost a whole century we tried in the believe of this myth – the technical advance as mastermind for any sort of progression. We have already learned about the shadowside of this believings and as well here, we need to rethink some basic ideas about sound reproduction.

Klangfilm  system with original baffle board made from solid timber woods in a japanese weekend residency. 

A huge speaker  (like a 12", or a 15" or even a 18" unit, permanent or field coil magnets) is a motor unit initiating a lot of mechanical energy during operation. This power of energy cannot be removed, it cannot be compensated by damping or with other forms of mechanical isolations. This energy is always present, it is just a question if its resonances will be used to distribute harmonies in order to complete the sound structure with emotional content.

I would be happy, if a sort of discussion will arise from this article and some of the countless readers of this blog, will start to comment this article with their personal experience and expertise in this field.

Read on soon, Volker

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

My first listening evaluation with the test cabinets started in a sealed mode. For that reason I had build connecting boards into the inside to connect the baffle with the back board in the central area. Here in the center the resonances are most substantial, in particular with such sizes of enclosures. All reflecting walls inside needed to be damped with layers of woolen materials, the cover quilts for transport protection are a very good and cheap solution. These can be used folded to form several layers and fixed with cleats to get a good damping effect to the inside reflexions. Woolen materials damp a lot better than foam, it was introduced to loudspeakers in order keep the amount of labour low during production. Before commercial aspects got into account, several other techniques and materials like felt have been used with a lot better success. I will show this methods further on in this articles, but for now the woolen quilts will do well.

The first listening showed a quite good overall balanced soundstage, not that far from what I am used to. Despite the bigger volume of the crates, the general sound structure was very detailed and refined, in particular in the mids and upper tonal spectrum. These cabinets work with a quite slim lower end, but in a excellent and undistorted manner, which should be normal with huge sealed designs. It was clear before, that the missing of the typical bass boost (somewhere around 80 to 120 hz), which is always present with small reflex cabinets like the Berkleys. The small volume of the Berkleys boosts this upper bass even more than a bigger type ported design like the Arden would do.
I did listen for a while and did find it very refined with lots of air, details and depths, but for me it lacked some low frequent energy, even when they get a lot deeper , maybe down to 40 hz. I did find the sound bit thin, less authoritative and with reduced energy in the low frequency ends. I missed the expressive timbre and its dedicated "foot snapping" effect, which I am normally used to and which is very typical for a 15'' speaker. So I decided to open up the back boards of the cabinets completely to try them as open baffles and to use the backward radiated energy as well.

I did take this step into account, when I finished the test cabinets, so I did mount the electrical terminals at the outer frame. This option gave me the opportunity just to unscrew the back boards. I did add some more woolen damping material into the chambers, in order to act like a resistance for the backside radiated energy. Such open baffle constructions in history have been made with adjustable blinds by Western Electric, so the cabinets could precisely been adjusted for compensation. I am still thinking about such a feature for my final design, but I am not sure about. On the other hand this feature gives a good opportunity to adjust a speakers to a given room, but I don't move that much speakers around. So it might be a unrealized complication or a silly option?
In my room the speakers are positioned quite close to backing walls, normally they need a minimum distance of 50 cm between their back and wall to get the reflections reduced. It is always absolutely listenable, if the speakers are positioned close to the walls with a distance less than 50 cm or even 1 m as other extreme. Sitting in a listening position of 3,50 m away, these differences have a dramatic influence to the illusion of the stage of sound. Direct radiated waves will be mixed with indirectly ones, in addition reflectied waves from ceiling and walls will blurry the precision of the sound structure. Here the front loaded horns show their positive abilities. Their concentrated projection reduce wandering reflections in rooms a lot, so they give projected frequencies a tight imaging and sound stage.

Everybody with large middle frequency horns knows what I am talking about. In their best option, let's say with a typical middle frequency horn installation like the WE 15/16 or the late 1970ties japanese Sato-horns, the soundstage can be completely holographic and as well free of any room reflections. Wider dispersing speakers (like the most cone radiating speakers with a typical 120-180° degree directionality) will always bounce a lot of energy into the room, which will be reflected certain times and therefore mix up with the direct radiated waves. So the illusion of a precisely projected stage suffers a lot. This effect explains the inevitability for damping the walls in listening environments with conventional radiating speakers. The front loaded horn at my set up act that way similar like such WE-horns, the distributed frequencies get projected to the listening position and avoid bouncing of uncontrolled reflexions in the room. Finally it leads as well to a wider fanning of the frequencies from 400 hz to 2500 hz, the spectrum distributed from the cone acting like a full range speaker. In addition the HF-horn has a physical support for its lowest cut off frequencies as well.
The middle tone spectrum has the most important tonalities and covers the human voice and almost a important part of any musical instrument. A perfect undistorted sound stage here, is the basic key for a natural impression of a technical reproduced sound. The harmonic resonances of the northern wood as materials of the cabinets give a natural tonal support and are very similar acting like musical instruments. Using both waves of radiated tones lead to a increase of sensitivity, with the Tannoy in full range mode this means a increase of LF up to 4000 hz.

Conclusion
I will stay for a while with this set up, than I will do final decisions about the speakers to be build soon. In order to make sure that I don't take any sort of inhabitation of the Berkley cabinets into justice I will stay on listening to this test setup. In the moment I am not sure, if a smaller enclosure will work more universal and more independent from different room parameters. If I am going to integrate the funnel into a cabinet, it will take 35 l of its gross volume. If will be very rigidly made with lots of strives to strengthen the structure, with pillows at all surfaces for the damping of the interior reflexions (exactly like the original Tannoy cabinets were made in the 1950-60ties, a gross volume of 170 l will be a good starting point. This will make possible a room friendly design, where the center of the chassis is not to low located. With roughly 90cm x 55cm x 43cm (HxWxD) it will fit the most living rooms.

Read on soon, Volker