How to get high frequencies at the end of recording

[Alfred]

Hi dear trolls..
.. I have been looking for a thread related to my doubts and the truth is that the result has been negative, or at least I have not been able to find it.
I am a lover of 7-inch singles at 45 rpm....
As is known, in a cutting recording, as the end of the record is reached, the spiral becomes narrower and therefore the separation of the grooves as well. ..
This means that the low frequencies are present, but the high frequencies are not in the same proportion as at the beginning of the disc.
To solve this situation in a non-professional environment in which I find myself, what can I do? ..
As I understand it, maybe I should increase the rotation of the lathe screw, or I increase medium and high frequencies, or both options at the same time, or I am completely wrong and neither of them is the solution.
Your enormous knowledge will surely help me find the light to this dilemma I have.
Cheers from Barcelona
Alfred

[farmersplow]

...I am a lover of 7-inch singles at 45 rpm....
...As is known, in a cutting recording, as the end of the record is reached, the spiral becomes narrower and therefore the separation of the grooves as well. ..
This means that the low frequencies are present, but the high frequencies are not in the same proportion as at the beginning of the disc.

Cheers from Barcelona
Alfred

Hello Alfred,

the groove spacing does not usually get narrower towards the center And even if they were narrower, you would have problems with low frequencies and not with high frequencies. Low frequencies require much more space than high frequencies (despite IRIAA).
What changes towards the center is the speed at which the needle moves across the groove. At the outer edge of a 12" record (diameter 300mm, circumference approx. 942mm) and a record rotation of 45 rpm (0.75 rpm/sec), the stylus travels about 700mm in one second. At the outer edge of a 7" record it is only 400mm and at the inner edge only 260mm in one second. This means that there is less and less length left towards the middle to accommodate one second of music material, which reduces the quality and therefore demanding pieces of music with high dynamics are usually played at the beginning of LP records. However, the distance between the grooves usually remains the same as at the beginning.
PS. With classical music, it often happens that nothing happens at all in terms of volume for 15 minutes and only then does a musical climax come - with timpani and trumpets, which makes it very loud. This was exactly wrong for long-playing records, which is why people (rarely) experimented and the record was cut from the inside out.
Do you have the problem with all recordings or only with certain songs? If you have the problem, you could always cut at a lower volume and/or change the EQ curve with the recording time and slowly increase the high frequencies - but this is very difficult.
Thomas

[markrob]

Hi,

The reason for cutting inside out was to make the transition from a multiple disc performance seamless for broadcast. If you start cutting inside, you have lower fidelity. As you move to the outer diameters, the fidelity improves. When you reach the end of the side, the next disc starts its recording from the outside in and is at the same fidelity level as the last disc. If you ended part one of a two disc program at the inner grooves and then began part two at the outside the change in quality would be very noticeable. This was a clever method to overcome this problem.

Mark

[farmersplow]

Hi,
The reason for cutting inside out was ...
Mark

... and I've learned something again! Thank you Mark!

[Sylvere]

thx mark !

[Alfred]

...I am a lover of 7-inch singles at 45 rpm....
...As is known, in a cutting recording, as the end of the record is reached, the spiral becomes narrower and therefore the separation of the grooves as well. ..
This means that the low frequencies are present, but the high frequencies are not in the same proportion as at the beginning of the disc.

Cheers from Barcelona
Alfred

Hello Alfred,

the groove spacing does not usually get narrower towards the center And even if they were narrower, you would have problems with low frequencies and not with high frequencies. Low frequencies require much more space than high frequencies (despite IRIAA).
What changes towards the center is the speed at which the needle moves across the groove. At the outer edge of a 12" record (diameter 300mm, circumference approx. 942mm) and a record rotation of 45 rpm (0.75 rpm/sec), the stylus travels about 700mm in one second. At the outer edge of a 7" record it is only 400mm and at the inner edge only 260mm in one second. This means that there is less and less length left towards the middle to accommodate one second of music material, which reduces the quality and therefore demanding pieces of music with high dynamics are usually played at the beginning of LP records. However, the distance between the grooves usually remains the same as at the beginning.
PS. With classical music, it often happens that nothing happens at all in terms of volume for 15 minutes and only then does a musical climax come - with timpani and trumpets, which makes it very loud. This was exactly wrong for long-playing records, which is why people (rarely) experimented and the record was cut from the inside out.
Do you have the problem with all recordings or only with certain songs? If you have the problem, you could always cut at a lower volume and/or change the EQ curve with the recording time and slowly increase the high frequencies - but this is very difficult.
Thomas

Hi Thomas. Thanks so much for your explanation.
Ooops.... well I was really wrong.
I thought that if I increased the separation of the grooves it was ideal for the high frequencies to appear in the recording, and it turns out that is not the case.
One is always learning.
I detect a certain degradation in quality and volume in all the recordings. Maybe it's that I am very demanding with the equipment configuration I have, and at a non-professional level there is nothing more that can be done.
Alfred

[Alfred]

Hi,

The reason for cutting inside out was to make the transition from a multiple disc performance seamless for broadcast. If you start cutting inside, you have lower fidelity. As you move to the outer diameters, the fidelity improves. When you reach the end of the side, the next disc starts its recording from the outside in and is at the same fidelity level as the last disc. If you ended part one of a two disc program at the inner grooves and then began part two at the outside the change in quality would be very noticeable. This was a clever method to overcome this problem.

Mark

Hi Mark, how much knowledge do you have...good lesson I have learned
Then, at the amateur level where I am, nothing can be done to improve volume and high frequencies?
Alfred

[Phinster]

Alfred,what cartridge and arm are you using?

[Greg Reierson]

If you are having unusually poor HF response towards the center you can check a few things. First, double check your repro side. It's critically important that your repro is properly calibrated, especially tonearm alignment. And while it's a good idea to use a modest cartridge for playback compatibility testing, it's not a good indication of frequency response. You need at least a decent elliptical stylus to understand frequency response, even at 45 RPM. Check response with a test record. Even then it's not all that reliable above 10k or so but it will get you in the ballpark.

Once you are sure your repro is in good shape, check a few things on the cutting side. Double check the zenith of your cutting head. IOW, the make sure your cutting stylus is perfectly perpendicular to the disc. To check, drop the head on a non-spinning scrap blank and move the head on its carriage from the outermost position to the innermost position. This will scribe a line on the blank. It should point directly toward the center of the disc. No room for error here.

Also make sure the cutting stylus is dead straight in the head.

Notice these are all mechanical things. That's where you'll find most problems in cutting and repro systems.

[dmills]

There are certain hard limits that particularly come to a head in the the 7 inch single format.

Firstly, the radial velocity of the cutter can never be allowed to exceed the tangential velocity at the cutting diameter, this is because the back angle of the cutter is 45 degrees so if you do blow that limit the back corner of the cutter will destroy the groove you have just cut!
It is actually a bit worse then this as the cutter is not at 90 degrees to the disk surface so the damage starts earlier then that.

This is a velocity limit and so falls at 6dB per octave.

On playback there is an acceleration limit which is dependent on the stylus geometry and is driven by the osculating circle of the stylus at the point it touches the groove wall, if the radius of curvature becomes too tight the stylus can no longer track along the wall. This is an acceleration limit, hence -12dB/Octave (But starting from higher up).

Note that the cutting engineer has to make a decision about what they expect their customers to have in terms of styli. You might be markedly more conservative if cutting rock intended to be loaded into jukeboxes then you could be if cutting classical for a a specifically audiophile label.

Given the 26cm/s tangential at the inner edge of a record, that implies that you need high frequency limiting with the appropriate frequency response curves to avoid this problem, usually done as a two band limiter with appropriate processing in the sidechain.

This limiter is also useful as it SUBSTANTIALLY reduces heating of the cutter head at high frequency.