🔊 Audio Half-speed mastered vinyl

Rudy

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This post will help clarify what half-speed mastered vinyl is all about.

The process of half-speed mastering was used by Decca from the late 50s to the early 60s for some of their classical recordings. The audiophile label Mobile Fidelity Sound Lab began releasing half-speed mastered LPs in 1977, pressed on virgin vinyl*. (Engineer Stan Ricker was one of the pioneers of using half-speed mastering for records.) Ever since, numerous audiophile releases have used half-speed mastering due to its advantages.

So, what exactly is half-speed mastering? When an LP is cut, both the master tape and the cutting lathe are reduced to half of their original speed. A master tape at 15 inches per second would be slowed to 7.5 ips, and the cutting lathe from 33⅓ to 16⅔ RPM. The equalization parameters also had to be cut in half in frequency--instructions** to set a slight boost or cut at 500Hz would have to be lowered to 250Hz, for example, or the records would not sound correct.***

Why would half-speed mastering be preferable? Mastering at half speed, remember, cuts the frequencies in half. The cutting head on the lathe can more easily handle lower frequencies without distorting. The electronics are also not as easily overloaded by high frequencies. The resulting lacquer (or metal) master† thereby can have less distortion than those records cut at full speed. This is especially helpful in recordings where there is a lot of high-frequency content like cymbals, percussion, brass, etc.

Can half-speed mastered records always sound better, and is it noticeable? It depends. There are many factors at play when discussing vinyl releases. (But keep in mind that all of these apply whether or not half-speed mastering is used to cut the record.)

First of all, the master tapes used to cut the record can make a difference. If it is an original two-track master that has proper equalization added, it can sound very true to the original tape. Record companies also had safeties (backups), cutting masters (which already had the original mastering engineer's cutting equalization applied), and today even digital files†† can be used to cut the records with.

Second, the engineer doing the mastering can have a large effect on how it sounds. Many familiar names are still mastering vinyl today, and each engineer might have a different "signature" sound to what they produce. This was true even back in vinyl's heyday.

Finally, the quality of the vinyl itself makes a difference. As mentioned above, virgin vinyl has an advantage over recycled. (And today's records don't use recycled vinyl anymore, making it a moot point for new vinyl production.) Thicker records can be harder to press well, but they can often play back quieter with almost no rumble or "vinyl noise" (aside from minor ticks, which can be present in any new vinyl for a number of reasons†††), and are often flatter.

So again, does half-speed mastering sound better than standard speed? Nobody has ever done a direct comparison of two identical titles cut at the same time with the different speeds, so it is hard to tell. Some mastering engineers don't even use it. Regardless, the process is a little more difficult, and usually only saved for the better vinyl releases. The benefits of half-speed mastering are heard are in combination with all three factors above.

And as always, "quality" depends on what equipment is used to listen to a record. Those with more money invested in playback will easily hear a difference. Others with more basic equipment may not.

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* In the 70s during the energy crisis, record labels began pressing thinner records using recycled vinyl. Virgin vinyl is brand new, non-recycled vinyl. Often, the formula for virgin vinyl was better (stiffer, quieter) than standard vinyl that most labels used back then.

** For an LP cutting master, the original mastering engineer made notes about equalization settings used to cut the original LP release, and those notes were kept with the reel of master tape used for future engineers to cut a record that sounded the same. (Studios typically use parametric equalizers.)

*** Columbia Records tried to cash in on the half-speed mastering phase with their Mastersound releases. Only, someone forgot to remind them they needed to cut the EQ settings in half. Many of those discs sounded awful as a result, and the sad thing was, most consumers never knew this, and assumed the Mastersound was the best sounding vinyl version of those titles.

† The discs originally used to cut 78 RPM masters to (or originally recorded acoustically) were cut to wax discs. Lacquer on an aluminum plate has since become the standard for long-playing 33⅓ and 45 RPM records. There is also a process called DMM (Direct Metal Mastering) where the sound is cut directly to a copper disc.

†† Records cut from digital files is often controversial. But keep in mind that due to the effects of the cutting head on a lathe, and the physical properties of the lacquer master, the sound will change compared to the original digital file a record is cut from. Some off-brand labels may use existing CDs for mastering vinyl, but most major labels will use a high-resolution digital file as a source.

††† Ticks in new vinyl can be caused by a number of things. Very rarely, a small particle of dust or dirt could end up cast into the stampers used to create the records. More commonly, the ticks in new records can be caused by dust and dirt from the pressing plant, along with the mold release compound used to release the newly-pressed record from the stampers. In a few cases, mishandling during pressing or packaging can result in clicks or pops in the record.
 

Bobberman

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I understand more now why When A&M were doing their Audio master plus Half speed mastering they mentioned on the inner sleeves they did them in a "Clean Room" pressing plant and allowed the Disc's to "Cool" a full 24 hours before they began packaging them It explains to me why the A&M audiophile discs sounded Great and didn't have the pops and ticks explained in this ththreads well as other labels as well
 

JOv2

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the A&M audiophile discs sounded Great and didn't have the pops and ticks
Agreed. I purchased a couple of those A+M/CTi reissues back in the early 1980s. The first thing I noticed at the time was how low the noise floor was (and I was running a dbx expander back in those days, too) and how clear the defined the instruments were. (Like a fool I sold them later only to upgrade to the lousy CD versions; luckily, I've since found passable CD reissues. I recently purchased an SS Nat Adderley and an NM K&JJ from the early '80s A+M LPs -- beautiful pressings all around.)
 

Rudy

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The few used copies I've purchased of the AM+ titles have pretty much cleaned up really well, and were taken care of. They do get noisy from dirt over the years, but running through the cleaner helps quite a bit there. Copies from the 60s, used, don't hold up so well and have a bit of wear (groove burn), which is why I went out of my way to find sealed copies of my recent additions.
 

Rudy

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It's been my nemesis for the past 15 or so years. I took to buying sealed new old stock records since I got burned too many times buying used records locally. Visual grading can't pick this out either.
 

JOv2

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It's been my nemesis for the past 15 or so years. I took to buying sealed new old stock records since I got burned too many times buying used records locally. Visual grading can't pick this out either.
Touche`!
 
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