Frequency Response: Lacquer v Pressing

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Frequency Response: Lacquer v Pressing

Unread postby Dub Studio » Wed Mar 30, 2016 9:27 am

How much would you say the frequency response of a cut changes once its been pressed?

Say I cut an acetate dub plate, and then used the exact same settings to cut the lacquers... would the frequency response play back the same once its pressed to vinyl?
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Re: Frequency Response: Lacquer v Pressing

Unread postby Sillitoe » Wed Mar 30, 2016 11:15 am

Hi Dub Studio,

Here's an image from the Handbook of Recording Engineering by John M. Eargle.

image.jpeg


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Re: Frequency Response: Lacquer v Pressing

Unread postby Dub Studio » Wed Mar 30, 2016 11:45 am

Perfect thanks!

So would it make sense to slightly undercook those frequencies for the lacquer cut?
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Re: Frequency Response: Lacquer v Pressing

Unread postby Sillitoe » Wed Mar 30, 2016 11:55 am

No worries!

Yeah, makes sense to me. However the outter diameters obviously reproduce the frequencies pretty much identically.
So you'd be changing the eq according to diameter...

And not only those specific frequencies of course.
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Re: Frequency Response: Lacquer v Pressing

Unread postby jjgolden » Wed Mar 30, 2016 12:44 pm

Thanks for the post

The above diagram shows diameter loss, not loss from lacquer to pressed vinyl.

Maybe some others can chime in, but I believe exposure to high temperature has a significant effect on high frequency loss. (as well as groove echo)
i.e. after a lacquer master is cut & shipped, it often sits in the back of a truck, or on a hot tarmac at the airport on the way to the plant.

Love to hear thought from others experience here.

JJG
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Re: Frequency Response: Lacquer v Pressing

Unread postby Sillitoe » Wed Mar 30, 2016 12:59 pm

Aaahh, this makes much more sense.
I was staring at that image thinking that it simply can't show the relationship between different states of one cut... (How could the hf be higher on the mother than the lacquer haha!)

Cheers JJ, I shouldn't be posting in the Pro section hehe! :oops:
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Re: Frequency Response: Lacquer v Pressing

Unread postby jjgolden » Wed Mar 30, 2016 1:49 pm

No no that diagram was really cool!
Thanks James!

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Re: Frequency Response: Lacquer v Pressing

Unread postby Dub Studio » Wed Mar 30, 2016 4:52 pm

jjgolden wrote:Thanks for the post

The above diagram shows diameter loss, not loss from lacquer to pressed vinyl.

JJG


But why would the authors present the three graphs next to each other if that wasn't the case?

I think its completely feasible for the mother to sound the brightest, followed by the pressings, then the lacquers. My reasoning being that the softer the material, the duller it will play back?
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Re: Frequency Response: Lacquer v Pressing

Unread postby jjgolden » Wed Mar 30, 2016 5:21 pm

You're so right, it's a valid observation in frequency reponse between the three graphs.
I guess there are a few angles to the question. The Graph relates
specifically to diameter loss and highlights a difference from Lacquer to mother to pressing.
It's pretty interesting how the response in the graph somehow flattens out perfectly between 10" and 8.5" on the mother.

High frequency loss at the outer edge is possible too.
Unless some science is done, it's hard to come to any concrete conclusions to set any cutting standards by.
I've heard pressings come back darker and also brighter than the lacquer.

The silvering & plating process is making a mold/copy of the original shape of the groove….possibly altering it's shape.
The pressing stage is making another copy of the groove shape which is possible to alter it's shape again.

Interesting stuff!
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Re: Frequency Response: Lacquer v Pressing

Unread postby Sillitoe » Wed Mar 30, 2016 6:50 pm

Haha, ok cool... Very interesting!

Dark art indeed!

The book does say that-
"Figure 10-24 shows the relative frequency response characteristics of the master lacquer, metal mold.. and fiinished pressing"

Then goes onto say that the deformation of disc material contributes to these scanning losses.

Will the Buchman-Meyer measurement technique work on mothers etc?

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Re: Frequency Response: Lacquer v Pressing

Unread postby mossboss » Thu Mar 31, 2016 3:38 am

That's been an issue since time immemorial in so far as to what losses are present in the steps of making the final product a record
All the comments are pretty much right may a I just point out that the plating process would be the least contributor to any losses as the growing of the metal parts are done at ionic level, you could not produce anything finer than this method.
JJ makes an interesting observation in the 10.5-8.5" area
Now take a 45 single and place it over that area on a 12" record one will find that it falls within these area assuming that it has around 3 minutes of. Music on it
Often people wonder why 45,s are brighter cleaner and very much alive wel that's the reason.
Best
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Re: Frequency Response: Lacquer v Pressing

Unread postby Sillitoe » Thu Mar 31, 2016 4:03 am

Cheers Mossboss!
I guess disc playback has the quantum physics thing happening, where the act of measuring/ observing the phenomenon affects and changes the results. Hehe!
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Re: Frequency Response: Lacquer v Pressing

Unread postby Dub Studio » Thu Mar 31, 2016 6:31 am

Sillitoe wrote:Haha, ok cool... Very interesting!

The book does say that-
"Figure 10-24 shows the relative frequency response characteristics of the master lacquer, metal mold.. and fiinished pressing"

Then goes onto say that the deformation of disc material contributes to these scanning losses.

James


So by "deformation" we are talking about the playback stylus deforming the grooves as it plays?
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Re: Frequency Response: Lacquer v Pressing

Unread postby Sillitoe » Thu Mar 31, 2016 6:38 am

That's what my (limited :D ) understanding is.

Other variables too, lacquer spring back, heat etc, as JJGolden said.

That graph was made by measuring with a stylus or styli...
There are also optical methods of measuring.
See interferometry.

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Re: Frequency Response: Lacquer v Pressing

Unread postby Dub Studio » Thu Mar 31, 2016 6:55 am

Thanks for clarifying, I wish there was a Youtube video for this interferometry / Buchman-Meyer / Christmas Tree thingy :D ... no idea how its supposed to work :| Any ideas?
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Re: Frequency Response: Lacquer v Pressing

Unread postby GeorgeZ » Thu Mar 31, 2016 6:59 am

Hello guys,

the abovementioned graphs were probably created on the grounds of experimental measurements of various records. The science is a little bit different.

There is no doubt that the material itself affects playback and there can be some difference between a lacquer, nickel mothers (first, second etc. copy) and vinyl records due to thoughness of material. Especially, when the same stylus/pickup is used for recording of all three "grooves". There would be different contact surface when the same stylus force is used OR the stylus force should be changed for every type of material.

But diameter loss should be ZERO when cut properly for a comparison - I mean when all the geometric parameters of grooves are inside limits of mechanical technology: angles in grooves to not exceed velocity limits defined by cutting styli shapes, radii in grooves to not exceed limits defined by playback styli shapes (conical/elliptical etc). And acceleration problems generally (often too loud highest frequencies) due to inability of some parts of cutting/playback systems to accelerate so fast. The curves would be almost flat along the diameter axis when test signals are cut at lower levels.

We preffer to use different pick-ups (and styli of course) for lacquers (Shure SC39ED), nickel mothers (Shure M44MC) and vinyl records (various Shure and Ortofon). All should be calibrated for the good tracking of the given medium and ideally also with linearized frequency response (compensated by filters).

I want to say that the measured so called HF loss near the center of records/mothers/lacquers is mostly some kind of distortion. Suprisingly, you can increase feeling of HF presence when some middle range frequencies are boosted to the state of distortion when additional harmonics are created and they are inside audible range.
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Re: Frequency Response: Lacquer v Pressing

Unread postby Sillitoe » Thu Mar 31, 2016 7:02 am

Awesome, thanks for the info and clarification George!
Especially on the styli that you guys use.

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Re: Frequency Response: Lacquer v Pressing

Unread postby sakuszi » Mon Apr 04, 2016 11:20 pm

even if it is a few percent loss of high frequency, it still pressed vinyl records have super high frequency audible even 30Hz -17kHz at a very high level! I have no idea how it is made! Factory vinyl records are really great! :)
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Re: Frequency Response: Lacquer v Pressing

Unread postby Dub Studio » Thu Apr 07, 2016 9:31 am

OK so I guess my question is.. does anyone here use any sort of pre-emphasis on their lacquers?

I mean there is a quite a lot of difference between the lacquer and the vinyl on those graphs, especially the 10khz @ 6.5 inches. I am not so concerned about the bigger losses toward the centre of the disc... just wondering if a general lift in the top end is needed to counter the inherent different in material?
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Re: Frequency Response: Lacquer v Pressing

Unread postby Greg Reierson » Fri Apr 08, 2016 9:46 am

Everything in the chain between the original source and signal to the head could be though of a as pre-emphasis (not to mention RIAA...) in an attempt to make the playback sound as close to the source as possible, but it's a moving target. The variation of different geometries and especially different cartridges far outweigh any differences between lacquer and vinyl. This is not a linear medium where a specific offset will always give the desired results. The best you can do is aim for the middle hope the end user has a system that can extract all of the care that you put into the grooves.
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