We at Hifi Pig recently bought and absolutely raved about the half speed master version of the John Martyn album Solid Air released on vinyl by Abbey Road. Miles Showell is the mastering engineer behind the project and Hifi Pig caught up with him for a chat.
Hifi Pig: Half speed mastering will be a new concept to many Hifi Pig readers, can you explain in simple terms the process. 

Miles Showell: Half speed mastering is a vinyl cutting process where the both source is played out and the cutting lathe is running at half the real time rate (effectively the source and the disc cutting lathe are locked together but both are running at precisely half the correct speed). The advantage of this is that the system is not stressed. The cutter-head draws somewhere between 1/4 to 1/3 of the current from the drive amplifiers than would be required for real time cutting and the recording stylus has twice as long to carve the intricate groove into the lacquer master disc. Unfortunately however, it is not as simple as running everything at half rate. There is an EQ curve (RIAA) applied to all vinyl records and by running the lathe at half speed, all the frequencies are wrong. Abbey Road have installed custom designed and built RIAA filters into the cutting amplifiers that feed the modified VMS 80 lathe. These custom filters apply the correct EQ curve when cutting at half-speed. 

Hifi Pig: And what do you believe the sonic benefits of half speed mastering? 

Miles Showell: All the difficult to cut high end frequencies become relatively easy to cut mid-range frequencies. This results in cuts that have excellent high frequency response (treble) and very solid and stable stereo images. What you need to bear in mind is that the only way a pressing plant can press a really high quality record is if the process starts with a really high quality cut. 

Hifi Pig: Are there any negative aspects to the process?

Miles Showell: The most negative aspect to half-speed mastering by far, as well as its Achilles’ heel is de-essing which is a process that is often required to avoid sibilance (vocal distortion) on the record. None of the tools I would ordinarily use for de-essing on a real time cut work at half speed so I need to pre-treat everything by capturing all the audio at high resolution digital then treating every “sss” or “t” sound in every vocal on every song before progressing. Because I wanted to make sure these cuts were as good as possible I used a very time consuming but incredibly accurate method. It would have been easy to strap a de-esser across the signal path when making the high resolution transfer but the de-esser would not be able to differentiate between a bright vocal, a loud snare drum, hi-hat, bright guitar, tambourine and all manner of other high energy sounds that do not require any reduction or limiting. My method is slow but doing it this way only treats the offending vocal problems and leaves the rest of the music untouched. 

Hifi Pig: Clearly we at Hifi Pig heard distinct sonic benefits with half speed mastering, why do you think the practice has not been more widely adopted. 

Miles Showell: The process has a few drawbacks from the point of view of the engineer. Most notably having to listen to all the music at half speed. It does tend to make you a little stir-crazy if you are not careful. Also it is far more labour intensive than a regular cut as well as obviously time consuming (especially as we insist on an acetate as part of a half-speed cut so both myself and the client can be sure everything is alright). Owing to the extra work from me, having a half-speed cut done is quite a lot more expensive for the client compared to a regular real time cut. Finally, the grove spacing computer on the lathe operates in a very different manner at half speed which has meant I have had to learn a new set of skills in order to get the lathe to cut as efficiently as possible. Happily all these issues melt away as soon as I listen to a half-speed cut, there is such a marked improvement that any issues suddenly seem insignificant. The fortunate thing for my clients is that I have spent the best part of the last 12 years developing my skills in this precise area. When I was getting going I had a huge amount of help via email from Stan Ricker in California. Stan was my hero and the King of Audiophile half-speed mastering. He had cut a great many records for Mobile Fidelity Sound Labs and it was his work with them that inspired me. He was amazed that anyone else was interested enough to try cutting at half-speed and I was amazed that he would share his knowledge and offer advice to me. Sadly Stan died last year but I will be forever grateful to him for his inspiration and encouragement. Without wanting to sound too big headed, I now have more experience at half-speed cutting than anyone else and Abbey Road has become the home of half-speed mastering. 

Hifi Pig: The John Martyn recording is taken from a high-resolution copy of the quarter inch master, why are you not cutting straight from the master tape? 

Miles Showell: The biggest variable when cutting from tape is the replay machine. Every individual roller in the tape’s path will have a direct effect on the quality of the audio emanating from the machine. In addition to this, the 35 Hz low-frequency roll off on a Studer disc-cutting advance head tape machine is in effect coming into play at 70 Hz at half speed. This is a problem if you want to hear as originally intended the lowest register of the bass end on a recording. In addition the masters for John Martyn’s album were encoded with Dolby A noise reduction. Dolby only ever made a very small quantity of half-speed enabled Dolby A cards, none of which are available to me. Although the technical team at Abbey Road are more than capable of modifying some spare Dolby A cards for half-speed use, to do so would require an intimate knowledge of the expansion circuit in the card which has never been made available outside of the Dolby Company. Finally, analogue tape becomes degraded with each pass over the replay heads. These tapes are getting old and it is no longer considered good practise to play and play and play precious old original masters for fear of damage and general wear and tear. Far better then to eliminate the variable of the reply machine, to decode the Dolby noise reduction correctly and to minimise wear of the master by capturing the music digitally at very high resolution using professional converters locked down with stable external word-clocks. To capture from an Ampex ATR-102 with extended bass heads is a far superior method in my opinion. 

Hifi Pig: The market for vinyl is growing every day, do you think vinyl playback offers sonic benefits over high-resolution digital playback? If so, what are the benefits? 

Miles Showell: I would say vinyl offers a very different and unique experience over high-resolution digital. For obvious reasons it is a very hands-on music carrying format and for a lot of people having a nice thing to hold on to and to cherish is very important. Whereas playing a data file on a hand held device or from your computer is far less rewarding .That said, vinyl is not a format that is not suited to everyone. It takes a huge amount of effort to care for your records as well as correctly set up your turntable, arm and cartridge combination, but if you manage to get it even remotely right, the sound quality is capable of impressing the most vehement sceptic. Another advantage is that the user can “tune” their system to their particular requirements. For example, do you go for the super sweet top end of a moving coil cartridge or the power of a good moving magnet design? Then there is a huge choice of phono pre amps some of which retail for silly money but even a budget unit will in most cases improve the sound over the on-board phono stage in many integrated amplifiers. The scope for tweaking the signal path is infinite with a vinyl playback system. Compare that to choice of high-resolution digital replay systems and the differences between the different converters are on the whole much smaller. 

Hifi Pig: Currently there are only a small number of recordings available in this format, are there plans to expand the albums available and if so what titles are in the pipeline? 

Miles Showell: There are indeed plans for further albums in this series. Sadly I am not at liberty to disclose any titles as yet. What I can say is that there will be one further album this coming autumn from a very big artist. This album has been half-speed mastered but the big difference is that it will be released as a double 45 R.P.M. LP. This will raise the quality bar even higher. Currently, the cut I did is working its way through the processing department of the pressing plant (Optimal in Germany who produce consistently excellent pressings). This is the same plant that pressed the initial six albums for the Universal / Abbey Road Half-Speed classic re-issues. If everything goes to plan, there will be another set of albums released early next year. The delay is largely due to ever growing lead times at every pressing plant on the planet. Both Universal and I are totally committed in making these releases as good as they possibly can be. Consequently this takes a lot of time. If every record was made this way we would need at least twice as many cutting rooms and engineers as there currently are and that is pretty much impossible.

Hifi Pig: Is it a struggle for Abbey Road to keep the old disc cutting lathes operational. 

Miles Showell: Yes it is. The vast majority of the lathes still running were made in what was then West Berlin by Neumann, the company better known for their microphones. There have been no new lathes made since the mid 1980s and all the men at Neumann who built them have since died. Unfortunately, they did not write everything down so some of their collective knowledge has gone with them. Because of this, there will almost certainly never be any new lathes. Therefore we have to look after and treat very carefully the ones we have. Luckily they were masterpieces of engineering excellence which is a huge benefit. However Neumann built them for a life cycle or 10 years or so and here we are more than 30 years in and we are working them as hard as ever. Abbey Road have been cutting grooves in discs since the doors first opened in the early 1930s so the technical team here have amassed a huge library of experience in maintaining them which makes our lathes among the very best working examples anywhere.  For any really specialist lathe work we have a very close working relationship with two of the six people on the planet that know how to fix the tricky stuff.

Hifi Pig: These albums are branded as Universal / Abbey Road. What are the origins of the  relationship with Universal and what was the goal at the start?

Miles Showell: Universal own Abbey Road as it was one of the assets they acquired when they bought EMI. I am freelance here but shortly after I started I was able to persuade the management that half-speed mastering was worth the investment. Initial feedback from my early clients was so good that it was the management who approached Universal and said you have a fabulous library of recordings and we have a world expert on half-speed mastering in the team. There is resurgence in vinyl sales and a demand for good quality pressings. Therefore why do we not get together and create the highest quality vinyl records possible by pooling our resources and playing to all of our strengths. Thankfully, Universal thought it was an excellent idea. 

Hifi Pig: Many audiophiles are passionate about analogue playback and reel2reel tape is becoming increasingly popular as a format, any plans for reel2reel releases in the future? 

Miles Showell: I had noticed the return of ¼” tape and the forthcoming new machine from the re-vamped ReVox brand. To be honest pre-recorded reel to reel tape has never been anything other than a niche consumer product. While I certainly wish ReVox the very best of luck and I certainly do not want to rain on anybody’s parade, I am not really sure domestic open reel tape will ever break out of its niche fanbase. As far as plans for releases go, that would be a question for the record companies. I have no say in the work I do. I certainly cannot choose what I work on but given the difficulty in making good quality domestic pre-recorded reel to reel tape, I would be very surprised if any major record company would ever want to embrace it.