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Do Off-center Holes Affect Sound?

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Do Off-center Holes Affect Sound?

Postby wojo58 » 14 Nov 2017 18:28

When the hole in the center of a LP is off-center, the record wobbles in a horizontal plane. As long as the cartridge can track this "oval", does the sound suffer? I know a warped record will deflect the cartridge vertically, but it seems universally accepted that this DOES NOT affect sound. Same too for the horizontal bop? \:D/
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Re: Do Off-center Holes Affect Sound?

Postby OneyedK » 14 Nov 2017 18:43

Since the platter speed is fixed. An off center pressed record will have a relative speed that is faster on one half of a turn and slower on the other.
Speed equals pitch so played notes will sound sharp on one half and flat on the other.

Wether it bothers you is another question, as some people are very sensitive to pitch variations other seem not to notice it and just enjoy the music.

Me personally, I can't stand it, especially on piano notes...

The variations in speed are much smaller with warped record, but still, they can be audible...
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Re: Do Off-center Holes Affect Sound?

Postby billshurv » 14 Nov 2017 20:27

It's IMO the biggest issue that needs fixing with replay. 0.55Hz FM doesn't sound bad, but the level is high so adding a continuous vibrato.
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Re: Do Off-center Holes Affect Sound?

Postby chiz » 14 Nov 2017 20:45

billshurv wrote:It's IMO the biggest issue that needs fixing with replay.

Agreed.

I buy both new and vintage records and in my experience this fault is quite common regardless of when they were pressed.

The effect gets worse closer to the label.

If they're really bad I sometimes enlarge the hole so I can centre them manually.
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Re: Do Off-center Holes Affect Sound?

Postby ripblade » 14 Nov 2017 21:23

I'm more sensitive to pitch wow caused by warps than I am to eccentric records. That said, I have one that's so bad it makes me sea-sick lol.
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Re: Do Off-center Holes Affect Sound?

Postby Sunwire » 14 Nov 2017 21:44

I wonder why you would say: "it seems universally accepted that this DOES NOT affect sound"

Clamps, rings, record flatteners, and arm/cartridge matching are all solutions to dealing with problems caused by warped records.

I find both warps and off-center records cause audible effects.

The Nakamichi Dragon turntable automatically recentered off center records in order to address this problem.
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Re: Do Off-center Holes Affect Sound?

Postby Sunwire » 14 Nov 2017 21:47

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Re: Do Off-center Holes Affect Sound?

Postby wojo58 » 14 Nov 2017 22:00

What in the vertical plane goes awry that causes the distortion? I'm guessing SRA/VTA, and maybe a smidge of VTF....?
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Re: Do Off-center Holes Affect Sound?

Postby billshurv » 14 Nov 2017 22:02

Hold a metal ruler on a table with the end sticking into the air and twang it. That's what your stylus does over a warp!
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Re: Do Off-center Holes Affect Sound?

Postby lini » 15 Nov 2017 00:37

wojo: Not only that, but there also is some speed variation due to so-called "scrubbing". I.e., on the majority of tonearms designs the axis for the vertical arm motion is not lowered onto record height, so that the actual effective length varies a tiny bit (or respectively more than necessary) with the arm angle (and with it also the alignment geometry). And the tracking force of course also varies a tiny bit with the arm angle - how exactly also depends on the particular design, though (mainly on whether its statically or dynamically balanced and how the counterweight is shaped and attached...).

Well, and regarding excentricity, you can pretty simply calculate the effect, as the speed deviation is directly proportional to the radius deviation. Typically one will tend to apply it to a playback radius of 100 mm, as that makes it easy to calculate and represents roundabout the middle of the LP playback area. So at 100 mm an excentricity of 0.2 mm would already mean a peak wow of +/- 0.2 % (or an RMS wow of that times 0.5^0.5 = ca. +/- 0.141 %). And due to the radius dependence with a playback radius range of ca. 60 to 145 mm one can of course also conclude, that the effect has to be almost 2.42 times as bad near the end of the record than at the beginning.

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Re: Do Off-center Holes Affect Sound?

Postby Sunwire » 15 Nov 2017 05:17

Warps are extremely low frequency signals, as far as the phono cartridge is concerned.
Watch your speaker's woofer as the stylus rides over a warp.
The woofer makes very large excursions in and out.
These low frequency signals can damage your woofers and the signal mixes with the musical signals to cause intermodulation distortion.
The amplifier can also be driven into clipping due to the amount of power needed to move the woofer so much at such a low frequency.

A low filter on your amp or preamp can reduce the effect, but sometimes won't eliminate it.
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Re: Do Off-center Holes Affect Sound?

Postby jdjohn » 15 Nov 2017 16:06

I'm surprised no one has mentioned channel imbalance. With the stylus moving back-and-forth horizontally, it slams into the groove walls with excess force, creating an imbalanced stereo signal. This can cause excess wear in the groove walls as well.

Warps are like riding a roller coaster, pulling more g-force in the dips (more amplitude in the signal...and again more wear), and less in the peaks (less detail as it rides lighter in the groove over the crest).
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Re: Do Off-center Holes Affect Sound?

Postby billshurv » 15 Nov 2017 18:30

Never heard of this 'slamming into the walls'. Any citations?
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Re: Do Off-center Holes Affect Sound?

Postby derspankster » 15 Nov 2017 19:59

billshurv wrote:Never heard of this 'slamming into the walls'. Any citations?

Sounds dangerous.
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Re: Do Off-center Holes Affect Sound?

Postby jdjohn » 15 Nov 2017 20:17

Perhaps 'slamming into' is a bit dramatic, so maybe 'riding up' on the groove walls is more palatable. Of course this is just centrifugal force, similar to riding in a car down a FLAT (no embankment) curvy road, where you slide in the seat back-and-forth around every curve - pressing against either the car door or the center console. The stylus will alternate riding up on the groove walls as it moves back-and-forth with an off-center record.

The February 1959 issue of Popular Mechanics has an article titled, "Hi-Fi Buyer's Guide: Tone Arms", which mentions this concept, and warps as well.

"Vertical motion of the record surface, due to warp, works against the arm's inertia to send tracking forces skyrocketing. Back and forth lateral motions of the arm due to record eccentricity produce destructive side forces with a high-inertia arm."p.215

Regarding viscous damping of tone arms, "On warped or off-center records, it offers the same drawbacks as high-intertia arms."p.216

Clearly, heavier tonearms create more of an issue with warped or off-center records.
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