Saturday, 7 December 2013

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