Wow and flutter of belt vs direct drive turtables question

[KentTeffeteller]

The quality of the belt can change W&F of my Thorens Td 125 MK II by over 300%. Most of the time after 50 hours the differences are between , 04 % and .08 %. But thats nothing like a great DD turntable with much lower W&F. .. A belt can also effect rumble figures. Empire TT with a cheap belt really compromises its performance.

This applies to most if not all belt drive designs to some degree. A poorly chosen aftermarket belt will degrade performance on many a good turntable in this genre, I see this often repairing and maintaining these turntables new and old. Patience is often necessary. And I've had to do my due diligence in this respect as a repair technician. Words of truth, well rationalized, and spoken. Respect and likes back at you for that post.

 

[KentTeffeteller]

How does one measure the wow and flutter on a belt drive without using a test album? How many DD tables are measured off a test album, and not motor electrical readings? Any two test albums punched the same exact way?. Ever notice they give no warp wow measurements?

All reputable manufacturers who are honest explain how those specifications were arrived at and what test records and instruments were used. It is equally up to you and I as owners and restorers to keep our turntables in fine mechanical order to the best of our abilities to maintain those performance limits.

 

[NoTransistors]

Anyone here remember Julian Hirsch?

Everything he reviewed was perfect. Why? Because he never used his ears, only an oscilloscope.

The primitive Garrard 301 or Thorens TD-124 can have most other turntables for lunch. Explain that .

 

[ETI_5000]

How does one measure the wow and flutter on a belt drive without using a test album?

Well, some manufacturer’s belt drive turntables, such as the Philips Direct Control models (e.g. AF-977), monitored the speed of the platter directly, and adjusted the speed via servo electronics if it wasn’t correct. See below for a picture of how they did it.



So they could (but they didn't ) have measured wow and flutter directly from the platter the same as some direct drive manufacturers did. Specifically Denon, Sansui (with some top-end models – their XR and XP-series) and Sony used tape heads to monitor the speed of magnetic marks on the inside of the outer rim of the platter – with Philips it was done using a tachometer near the centre spindle.

How many DD tables are measured off a test album, and not motor electrical readings?

Well, the majority are specified using that method, with some also using motor or platter direct readings, although some just used the direct reading method, which is perfectly valid, as long as it's compared only with readings taken the same way.

They (usually) tell you in the specifications when it's measured directly, although some just include abbreviations such as ‘FG’ or ‘servo’ to indicate it was measured from the motor or platter. The better manufacturers, such as Sony and Technics, stated in clear language for laymen how the motor/platter measuring method differed.

For instance, from Sony (PS-X600), “This new measuring method concerns only the turntable assembly, including the platter. It excludes wow and flutter caused by the tonearm, the cartridge, or the record. Measured by obtaining signal from magnetic pickup head.” The magnetic pickup (tape) head they’re referring to is the one which measures the speed of the magnetic marks on the inside of the outer rim of their platters. From Technics (SL-1200Mk2), “This rating refers to turntable assembly alone, excluding effects of record, cartridge or tonearm, but including platter. Measured by obtaining signal from built-in frequency generator of motor assembly.”

Some manufacturers used to provide both sets of specifications – measured from the motor or platter, and also measured playing a record, occasionally using several different measuring standards, such as both DIN (peak weighted) and Weighted RMS (WRMS). The figures using a record are typically much higher, as they’re measuring any inherent wow and flutter on the record, as well as caused by stylus drag. Here are some typical specification figures:

Denon DP-47F: 0.01% WRMS (measured from inside of platter outer rim, via tape head), 0.02% WRMS (using a record)

Pioneer PL-640: 0.012% WRMS (from motor), 0.025% WRMS (using a record),

Sony PS-X600: 0.015% WRMS (from platter), 0.025% WRMS (using a record)

Technics SL-1200Mk2: 0.01% WRMS (from motor), 0.025% WRMS (using a record)

 

[Gibsonian]

Wow! That's not much flutter......

 

[vinyl1]

Those are interesting numbers. I'd like to see the WRMS reading on a high-end belt-drive turntable playing a record, one of the ones where they get their speed stability from a massive platter.

 

[marcmorin]

All reputable manufacturers who are honest explain how those specifications were arrived at and what test records and instruments were used. It is equally up to you and I as owners and restorers to keep our turntables in fine mechanical order to the best of our abilities to maintain those performance limits.

OK, I get that.........but my question was about how it's actually tested, and if those tests reflect anything about actual playback of a given album.
I've never seen published in W/F specs in tables, the effects of the whole table. And I'll C/P from further on in this thread.

“This rating refers to turntable assembly alone, excluding effects of record, cartridge or tonearm, but including platter. Measured by obtaining signal from built-in frequency generator of motor assembly.”

And then back to my question, as why warp wow figurers for the arm are never given. There's certainly a lot more to playback than how the motor assembly is controlled.

 

[bobins08]

I used to live by specs when I was young. Finally started listening and learning what I like. Specs are guidance to me and that is all. Listening is most important.

I really like the sound I get from my upgraded belt drive AR XB. The table is quiet,the music is well presented. I tend to favor belts, also have a Thorens TD160 w/ SME 3009 arm.

Direct drives in my stable are SL1600 mk II. I bought that for its blend of quality and automation but I do not think it sounds as good as the two non stock belt drives mentioned above. I have a KD 550 in storage , would like to put a great arm on it someday. Have no qualms about it being direct drive except for parts availability.

I don't have an idler, maybe someday.

 

[4-2-7]

Wow and flutter specs are all fine and dandy, and as long as they are low enough not to be heard, A percentage point here and there means little if the lower spec W&F table misses other aspects like musicality, isolation, resonance, speed stability.

 

[4-2-7]

There's certainly a lot more to playback than how the motor assembly is controlled.

Bingo

We use a "System" of components in our play back and one can't just look at one small function of one component. The chain has to function as a whole and that includes the most veritable component we use in vinyl play back...the record.

 

[Mister Pig]

As hobbyists we like methods that allow us to rationalize and guide our purchase decisions. Specifications do that for us. And they are a barometer for manufacturers to guide the design process. How could anything be engineered without specifications at the sub component and materials level? Of course we need tolerances and specifications.

However, turntables are a summation of mechanical and electrical systems, and are an exercise in resonance control. The cartridge is the focal point of all mechanical information being inputted from a turntable. Drive system, chassis, tone arm, acoustic vibration, and so on and so forth. So what we experience in analog playback is a synthesis of what it takes to play a record, and the drive system is only one small part. But of course, getting speed right is a significant concern, it is something that has to be done right in order to get the basics of playing music right.

In the past the problem I have had with direct drive turntables is that they lack the ability to present fine detail and shading. I was using Technics SP 25 and SP 15 tables, and never could get them to sound as good as my tape drive and idler tables. The question of why is not one I could definitively answer. I always suspected that the energy created by a high torque motor passed back through the plinth, and the platter/bearing assembly....back into the cartridge. This extra energy created a noise floor that the lowest detailed information would get obscured by. This did not happen with my tape drive table, and I really wonder why it did not happen with my TD 124 which is a hybrid belt/idler design. But the differences were easy to hear.

But I am not ready to give up. I moved the SP 25 and 15 on to new owners. I currently have a Technics SP 10 MK II that is getting fitted with a quality plinth, and will be pressed into service. It will be interesting to see what a higher mass platter and stiffer chassis will bring to the experience. Perhaps this will be a direct drive table that I can enjoy. Time will tell.

Regards
Mister Pig

 

[JP]

I always suspected that the energy created by a high torque motor passed back through the plinth, and the platter/bearing assembly....back into the cartridge.

During playback those motors are loafing along.

 

[Mister Pig]

During playback those motors are loafing along.

Very well could be. But there has to be an explanation of why the table sounds as mediocre as they do I really wanted to like that SP15, it has such a nice feel to it, looks attractive, is convenient to use, had a very nice plinth and SAEC arm with it. And it sounded dead and lifeless with a significant loss of detail. I moved arms around, different cartridges, and never could get that table to come close in sound quality to my Serac. Never could figure out an answer for that one.

Regards
Mister Pig

 

[twoengine]

Mister Pig,

What's a tape drive turntable?

 

[Mister Pig]

Mister Pig,

What's a tape drive turntable?

Uses a Mylar tape as a belt. It is not elastic like a typical belt, but does exhibit belt creep like any other belt.

Regards
Mister Pig

 

[JimmyEJames]

See the post immediately above mine.

Still makes no sense
Turntable end table lack table.......?
Please be specific
JJ

 

[marcmorin]

During playback those motors are loafing along.

correct........right up to the time that it senses any change in speed via info provided by sensors.....and then the motor is "full on" until the sensors say everything is back to normal.

 

[gusten]

I think that W&F measurements in reality are very difficult to do correctly. Most must be taken with a lot of salt. But if following DIN-standard, using a DIN or B&K test record, getting under 0,05% is good. It will mean that all FM is included, both from arm and record. Of course playing normal records the contributions from record and arm will normally increase.

 

[grottyash]

Still makes no sense
Turntable end table lack table.......?
Please be specific
JJ

Sorry, I don't understand. Lack is a cheap bedside table made by Ikea that is lightweight but its construction is ideal for absorbing vibration. It makes an excellent turntable stand. Does that make sense now?

 

[NoTransistors]

I love it when a 'discussion' goes around and around in circles, just like a record player.