Tagged: Interview

Watch The Vinyl Factory’s short film on the art of vinyl mastering – by FACT Magazine

The Vinyl Factory’s new short film profiles three of the finest minds in mastering.

Practically everything that is pressed to vinyl passes through the hands of a mastering engineer, who oversees the transition from tape, CD or MP3 onto the master disc or dubplate that will then be sent to the pressing plant for wider production.

Our friends at The Vinyl Factory tracked down three of the world’s foremost mastering engineers for a short film, Sculpting Sound, that looks into their role in the increasingly threatened vinyl manufacturing process.

The filmmakers join Andreas ‘Lupo’ Lubich at Calyx Mastering in Berlin, renowned for its attention to detail in cutting some of the most demanding avant-garde records around, and visit Rashad Becker of Berlin’s Dubplates & Mastering as well Noel Summerville (formerly of Pye Studios and Metropolis, now running his own 3343 Mastering studio) in London.

via Watch The Vinyl Factory’s short film on the art of vinyl mastering, featuring Rashad Becker, Lupo and more – FACT Magazine: Music News, New Music..

Loop_O: Master Of The Grooves | iCrates |2011

Loop_O: Master Of The Grooves

  How does the music get on the record? – Andreas [LUPO] Lubich who signs his cuts as “Loop_O” is one of the magicians who transfers sound-waves into the vinyl. The Berlin-based cutting and mastering engineer co-execs the legendary Dubplates & Mastering studio since famous record store Hard Wax – founder Mark Ernestus and Moritz von Oswald of Basic Channel sold the studio to its engineers in the late 90ies. Loop_O’s cuts set loads of parties and soundclashes on fire in the last decade. So meet the man who provides us with good sounding records, take a deep look down in the grooves and into how to produce a vinyl record!

Are you the only one cutting records like this in Berlin?

In the mid 90`s we actually were the only cutting studio in Berlin, besides a few others in Germany. And within our scene there were The Exchange in London, and at that time, National Sound in Detroit. These were the three main studios cutting for the electronic music scene, or more special the techno scene of that time.
Over all the years it was told, vinyl is dead. But actually more and more cutting studios opened and also pressing plants. On the other hand, of corse a few others closed, but from my perspective these days there are more cutting studios working in the same field than in the 90`s. And still, everyone has enough to do. So the scene grew, but it’s still a really nice, small scene which works quite good by itself.

Why did it grow?

Basically because the media is so great, acoustically and physically. On one side there is the fact that, if the record is cut well, its able to sound more rich and detailed than CD – at least different, because more pleasant to the ear. Beside the sound it’s just great to have this haptic feeling again, to have a record to put on the turntable, to work with it, to spin it and to have the cover-art. So basically to live with it.
Vinyl itself maybe only survived due to the DJ scene. Because since the late 80`s the industry doesn’t care about vinyl anymore. But these days they do, again. So it was all the small individuals, the small labels who kept vinyl alive, heftily the electronic music scene.

But also the Dubplates business has changed. Before the invention of the digital DJ tools like final scratch, the Drum n Bass and the Reggae scene used a lot of Dubplates. These scenes, up to a certain point, were basically based on using and exchanging Dubplates. Reggae more than Drum n Bass. But with Drum n Bass, the whole idea was focused to gettting the loudest and best possible sound onto a dubplate than any other DJ playing at the same party. At that time we had a lot of DJ`s dropping by to check their mixes for the vinyl and the Dubplates. So when there was something wrong and it wasn’t possible to cut that specific track loud enough, then they had to get back on the mix.
In the Reggae business it was different to getting the loudest plate. Here you have the versions of a track and then somebody is voicing this version, usually in one of the studios in Jamaica.
This results in a Dubplate which is played during a soundclash. That was a really interesting and trustfull thing. Because it was important to be discreet about who was cutting the Dubplates for that particular soundsystem as it was seriously important that your Dubplate works and sounds better than the one from the other soundsystem you had the clash with.

Please describe the process, if I come to you with a soundfile to be pressed on vinyl, what do you do first?

First I try to talk with you about the background of the music and your expectations. Then I listen step by step through the whole production if I can get the expected result out of it. But with about 90% of the soundfiles I´m getting I can work work with.

What would make them not work?

One example if the mix has a totally wrong musical and tonal balance. Of course that’s one of the reasons why you go to get it mastered. But at some point you can only repair things. And even then the result cannot be as good as with a better mix from scratch. So then the question is, does the artist, or whoever the client is, have the ability to make it better? And can I help him to make it better, or is what I have also what I have to work with? Generally I can work with nearly everything to get at least a good result, I would say.

Another thing, if you´ve got a mix where people thought like “Oh, I mastered it already kind of halfway through, so save money at the mastering stage”. Like this sometimes the mixes end up in being totally squashed and limited, and with that you can’t do so much. Technically you can’t move in the mix anymore because there´s no dynamic and the whole frequency range is pushed to the max, flat and dead. Maybe it sounds okay and so I can use it just as it is. But you often can`t even solve minor things, depending on how much the mix got squashed. People should care about their music, I care about their sound.
The best mix is of course one with a good overall balance, and enough dynamic, so you can treat it in the way it needs to be treated. In a musical way, in a tonal way, and also in a functional way.
Because I work with every piece differently, depending on the style, the genre and its purpose. So the mastering and cut of a dance track is quite different to one for listening music.

Then there is this myth about that its not possible to get a stereo-bass cut onto vinyl. You can´t generalize this statement. The question is how much stereo-bass you have, within which frequency-range and for what the cut is going to be used for. But I am here to make the adjustments necessary to get it working on vinyl and to keep the musical idea behind that stereo-bass, if there is any. Eventually I have to discuss this with my client if the stereo-bass makes sense anyway. So for example when I cut for home-listening purposes, then there is usually no problem with a stereo-bass. Because home hifi sytems are fully stereo. Then there is only the question if it has to be mono compatible for radioplay etc.
But if its a club-track the point is basically whether it works at the dancefloor or not. With most of the clubs you have the situation that the bass-speakers of the stereo-system are driven by just one mono amplifier. So the whole bass gets monoized. To get the technical background: If you have a stereo-bass you have a time shift between the bass-signal in the left and the one in the right speaker. When you sum these up together, then parts of the bass signal are canceled to a certain amount. So you will miss the bassy bottom of the kick or the bassline at the dancefloor altough the bass is actually on the record. So you have to decide before if your record is intended to be played in a club or not. If so, the bass should be monoized without affecting the musical intention because otherwise it works not for all of the club systems, the P.A.s.

Find a graphic illustration of a stereo signal in a record groove here!

So when I come in with a professionally mastered production, do you still put your hands on it before you cut it?

First I try to get an overview over your production. Therefore I import all the files in my workstation, sequence the individual tracks regarding the tracklisting I´ve got from you and check the levels, gaps, start and endings and of course the sound of all tracks.

When you are satisfied with how the pre-master is sounding I will cut it one-to-one, which means without any changes. Therefore I usually do a test-cut to hear if and how the sound is changing on the vinyl. Afterwards I play it back with some of the different pick-ups I have to get an idea of the sound-range the listener lastly gets at home or in the club. Because a cut is nearly identical with the original only in the best possible case. Especially as not every pick-up and system out there is able to reproduce the sound as it is actually on the vinyl. So during the cut I need to have an idea about which pick-ups the production will be played with.
But if the result of this testcut is convincing I´ll go for the one-to-one cut so the record should sound as close as possible to the pre-master you came in with.

In some cases a certain sound in the mix or the whole perception of the sound is changing at the cut. This can be drastically but great, or just slightly but disturbing, depending on the cutting settings and playback system. Generally this change is what people call the vinyl or analogue sound. You´ll get this kind of extra width and space with extended harmonics, combined with a certain thickness, if done right. Maybe that´s what you`ve been looking for. So you can use the abilities you have with the vinyl to make your record sounding special and to get the best out of it.

But you have to be careful. Because one of these changes is the fact that towards to the inner diameter of the record the reproduction, especially the playback of the higher frequencies, gets difficult. That again depends basically on the pick-up you use.
It´s a thing people often don’t realize before their first own release. You usually don`t recognize it because when you start to listen to a song for a while your ear adapts the sound. So later on you think to hear frequencies which aren´t played back anymore.
Until the 90`s that was known. When you listen to a record from the 60ies, 70ies, up to the 80ies, the tracklisting was always done according to the media, which was vinyl. That means that the top hit or the song with the most complex tonal structure got always cut to the outer diameter, where it sounds the best. In the inner diameter you only find a ballad, an acapella or an instrumental. But later on people didn’t think about this anymore. So these days you get a CD with 10 tracks to be cut for a vinyl release. Imagine the side-split for the a and b-side would be between track 5 and 6. So if track 5 is the hit of this record and track 10 has a lot of highs in it you won´t have that much fun with both of them. Its because these tracks end up in the area of the vinyl which doesn’t sound the best. At least on inferior playback systems. In this case eventually you can discuss with your client to change the tracklisting. If thats not possible you have to prepare the particular tracks individually for the cut.

But for dance music there could be another workaround eventually. Dance records often have not more than 2 tracks per side. If none of the tracks works satisfying within the inner diameter and there is no other track which would work better then, and that´s what I´ve done sometimes in the past, I cut the first track at 33 rpm and the second track at 45 rpm individually. So the second track at 45 rpm even in the inner diameter of the record sounds as good as the track at 33 rpm at the outer diameter. This can be a special solution for dance music solving that problem.
But in the daily routine where there is no way to change the tracklisting you have to adjust the cutting parameters or you have to tweak the relevant tracks to prevent as much loss of highs as possible.

The whole problem depends on the taste of your clients. During the last decade the taste changed regarding how they want their cuts. Especially for dance records. So the time I´ve started with cutting the request was to get a record cut as loud as possible. A good cut was a so called “hot”, means loud cut. A result of this was the fact that a lot of records sounded distorted, but in a good way maybe. This became a sort of style for records of that time. But all of them had this loss of highs towards the inner diameter. And this was also kind of a feature. Because within the last third of a dance-record the next track is mixed in anyway, if played in a DJ-set. So many clients were totally fine with that.
What changed in the new millenium is, that a new generation of clients went on the scene. People who didn`t grow up with vinyl anymore. So for some of these clients, once you know them, you have to cut at a lower level and maybe more within the outer diameter of a record to have the full frequency spectrum over the whole side of a record while playback. Because they only want to have a bit of emphasize to the sound but no loss of highs or distortion at all.
If you have a more detailed piece of music, even to be played at a club, then you know it’s more about sound then level. So you cut it at a lower level anyway.
But in my view, these days the taste is changing back to the old school when it comes to dance music.
These are some of the influences you have to think about when you master and cut a record.
Its generally about to make it better as it was, not just different.
And thats the ongoing question during the mastering and cutting process anyway: is it better? – or just different? I mean, different is easy, everybody can do that. The point is to be honest with yourself and your work – to get the idea behind the production and the music to make it just better, that’s the goal.

A fetal record: one piece of raw vinyl

What is the technical connection between the computer and the music on it and the cutting machine?

For me, the computer in the studio is mainly a recording and playback device. So when I get your tracks I load them into the workstation from where I play them back as well record them, once they are mastered. The output of the workstation feeds a high quality digital to analogue converter from where the processing chain and the cutting console gets the signal.
The cutting console is a control desk with 2 linked stereo channels and all the basic settings I need to prepare the signal to be cut. Here I can set a high and low cut, I can spread the overall stereo image while narrowing the bass image or monoize only the bass below a certain frequency if necessary and I can set the desired cutting level. With all these settings I control how the signal affects the groove and its pitch over the side. Like this I´m able to safe space for a long sidelength to be cut, for example.

From the cutting console one stereo signal goes into the cutting amplifier while the other channel feed the pitch control computer of the cutting machine. From the cutting amplifier, where beside the amplification also the riaa-equalization is applied, the signal goes to the cutterhead. The cutterhead holds the cutting stylus which is driven by two coils, one for the left and one for the right channel. These cutting-stylus actually cuts the groove into a master-lacquer-disc. The pitch-control-computer meanwhile calculates permanently how mutch space the actual groove-modulation takes to prevent overcuts and ensure a safe cut.
Pitch means how much grooves per millimetre is cut onto the record. You can calculate how much pitch you need to have to get a certain amount of time to the record. Resulting from that pitch I have more or less space for the resulting cutting depth. Because the deeper the groove, the wider the groove gets, the less space and running-time I get onto the record. That means for example a long side length results in a relatively thin groove and a lower level. And a club record with less than 10 minutes per side I can cut with deep grooves and loud. Due to the high level on the record, there is a high movement of the groove, so the groove actually needs to be cut deep to be safe. Otherwise skipping can occur in the club.
The calculation the pitch computer does is based on the values I set up at the cutting-machine itself. This is the basic cutting depth and the land inbetween the grooves. Like this I have the ability to choose how close the grooves should be cut together, you can say as close as they can without touching each other.
These are basically all the settings I have to think about and the adjustments I have to make before I cut a record.

How Vinyl Records Are Made

So the cutting level depends on the horizontal modulation or deviation of the groove?

Yes, there is a correlation between the cutting depth and cutting width as well as between the cutting level and the overall modulation of the groove. The depth and width increases with the stereo-image of the music to be cut. The modulation of the groove on the record increases with the cutting level. So at a loud cut and a stereo-cut the groove is more “spread out” and takes more space than a cut which is more quiet and mono.
The same applies to the high and low frequencies. You have to know that the resulting wavelength of a high frequency is relatively short. The wavelength of a low frequency signal is quite long. Thats one of the reasons the neighbours usually hear the bass of your music better than you do, which results in stress sometimes.
So a quite bassy sound takes up much more space on a record than a more mid or high frequency sound.
Here it comes back to the issue of cutting a stereo bass, you have to realise that the cutting stylus we cut consists of only one piece. So one side cuts the left channel, the other side cuts the right channel. When we have a stereo signal, the left signal needs to be cut slightly delayed against right channel signal. But the problem cutting-wise is that the stylus is not able to split itself inbetween to cut the left side different than the right side. So he cut both sides together by a vertical modulation. Like this you can cut both sides of a signal independent with just one stylus at the same time.
But it gets dangerous if the bass frequency is too low and too stereo combined with a quite high cuttting level. Because of the high lateral and vertical modulation the cutting stylus could leave the disc or, thats the worst case scenario, it cuts a hole into the disk. In the first case the record will skip, in the second case I get a serious damage to the cutting-stylus. Because the master lacquer discs only have a thin layer of lacquer, vinyl acetate, we cut into. Below this is there is a core of a aluminium plate. So when you cut too deep, you cut into the aluminum and your stylus is broken. Therefore I have to choose the basic cutting depth carefully according to the signal I have.
But even when I´m able to do the cut I also have to think about if the pressing-plant can do process without problems.
Because the issue with the stereo-bass I tried to describe results in many little pits. In the pressing-plant the soft vinyl has to reach every little corner of the cut. But if there are some really small but deep pits in the cut the vinyl can’t reach the top end of them. So spots of so called “no-fills” can occur. These no fills are recognized as crackles on a record later on.
Its my job to prevent such problems beforehand. So I also agree, there´s a problem with stereo bass as desribed, but I`m here to solve it. You make the music.

How Vinyl Records Are Made Pt. 2

Why does the sound get better when you transfer a digital signal to a vinyl record than a digital signal to a CD?

What you hear as the sound of vinyl is mostly a sideeffect on the playback side. The reality is that a cut, properly done and played back with a really good pick-up and system doesn’t sound much different than the original. Its not better than the original, but in the best case, also not worse. But if you as a cutting engineer know or at least got an idea of what the record will be used for and what system it will be played at, then you can play with the sideeffects while doing the cut. Without getting to much in depth about pick-ups, its given that a high quality pick-up with a high compliance and low tracking force can follow the excursions of the groove much better than a DJ-pick-up which has a high tracking-force as its made for more safe than best groove-tracking and scratching performance. By knowing these backgrounds you can use these facts for your needs. But on the record itself is basically the same and original sound.
Of course the technical specifications of a vinyl record are much worse than of tape or any digital media. There is less stereo separation, a higher noise floor etc. but in fact thats all pleasant to the ear. Its similar to using a tube device to saturate your sound.
The sideffects of the pick-up system are basically distortion and within this the saturation and colorization with 2nd and 3rd harmonics at the playback side. This can give you a much richer, saturated and sometimes more detailed and frequencywise expanded sound.
But of course I usually dont want to have that effect at a classical record. Here I would try to cut one-to-one with as less change as possible. But starting from a jazz record where elements from the drums and double-bass get emphasized up to an acid-techno and breakcore record it is a great feature. Furthermore there are soundstyles which exist only due that phenomenons. Remember for example a roots-reggae record without the typically and in a nice way distorted hi-hats. Without that it doesn´t sound authentic, I would say.

So beauty lies in its imperfections?


Find Loop_O on the web:
Loop_O’s space
Dubplates & Mastering
mail: lupo at dubplates-mastering.com

Photographs by Sheila Seyfert




De:Bug Musiktechnik » Andreas Lubich at Dubplates & Mastering |2006

Dubplates & Mastering

von der Festplatte aufs Vinyl

Seit gut zehn Jahren wird bei Dubplates & Mastering in Berlin-Kreuzberg Musik gemastert und auf Vinyl umgeschnitten. Fünf Engineers arbeiten hier in zwei Studios. Einer von ihnen ist Andreas Lubich, dessen Kürzel “Loop-O” zahlreiche Platten in euren Schränken ziert. Er erklärt, wie man Musik überhaupt auf Vinyl bekommt, warum die Platte ein besseres Frequenzspektrum hat als die CD und warum ein Limiter alles zerstören kann.

von Thaddeus Herrmann

Warum muss man Musik überhaupt mastern?
Nüchtern betrachtet ist Mastern die klangliche und technische Optimierung einer musikalischen Produktion, also der letzte Schritt vor Presswerk und Release. Früher beinhaltete das allein die technische Optimierung eines Premasters. Damals sollte weitgehend keine Soundveränderung stattfinden. Im Laufe der Jahre ist daraus allerdings ein sehr viel kreativerer Prozess geworden. Mastering-Engineers sind heute fast schon Produzenten und sind für den letzten klanglichen Schliff der Produktion verantwortlich und dafür, ob eine 12″ im Club funktioniert oder nicht. Wie gut das gelingt, ist weniger vom Equipment als von den Fähigkeiten des Engineers und der Qualität des Ausgangsmaterials abhängig. Als Mastering-Engineer hört man Musik analytischer als der Musiker. Dadurch geht man an die Endbearbeitung objektiver und effektiver heran.

Mit welchen Vorstellungen kommen die Kunden zu euch?
Das ist ganz unterschiedlich. Manche kommen einfach aufgrund der technischen Notwendigkeit des Umschnitts zu uns. Ein größerer Teil der Kunden kommt, da sie sich einen bestimmten Sound für ihre Produktion wünschen, den sie bereits auf anderen bei uns gemasterten und geschnittenen Platten gehört haben.

Vinylschnitt hat eine lange Geschichte, auch die Maschinen sind fast schon antik. Was hat sich im Laufe der Jahre verändert? Kann die Technik heute überhaupt noch mithalten?
Verändert hat sich vor allem das Frequenzspektrum und die Pegel. Dadurch, dass heute fast alle digital produzieren, ist das Material, das bei uns ankommt, völlig anders als das, was noch vor zehn Jahren im Studio ankam. Und natürlich wird von den Künstlern erwartet, dass dieses Frequenzspektrum und der deutlich lautere Pegel auch so auf die Schallplatte kommen. Früher hatte man analoge Instrumente und Tonbänder mit einem ganz anderen, viel moderateren Frequenzgang. Dazu kam im Aufnahmestudio ein Toningenieur, der die Produktion schon hinsichtlich der physikalischen Gegebenheiten der Schallplatte bearbeitet hatte. Heutzutage gibt es nahezu keine Limitierung mehr zwischen Frequenz und Pegel. Auf CD kann man das auch gut abbilden, die klingt so, wie man sie aufgenommen oder gemastert hat. Auf Vinyl funktioniert das anders. Die Platte unterliegt gewissen physikalischen Limitierungen und vielen Musikern fehlt die Produktionserfahrung im Umgang mit der Schallplatte. Ich begreife das als Chance. Vinyl lebt, die Musik verändert sich, wenn man sie auf Schallplatte umschneidet. Für mich ist das der Reiz des Mediums, da geht die kreative Arbeit erst richtig los.

Gibt es Dinge, die man schon im Mix beachten sollte, wenn der Track später auf Schallplatte releast werden soll?
Ganz wichtig ist mir, dass sich die Musiker nicht zu sehr den Kopf zerbrechen über technische Gegebenheiten und zunächst die Musik so machen, wie sie sie machen wollen. Erst dann sollte man sich man mit dem Medium Schallplatte und seinen physikalischen Begrenzungen auseinander setzen. Wichtig ist ein homogener Mix. Das bedeutet, jeder Sound hat seinen Platz. Sounds, die aufgrund ihres Pegels oder ihrer Frequenz stark aus dem Mix herausfallen, gehen immer auf Kosten des Gesamtsounds und auch der Abtastbarkeit der Platte. Leider wird häufig versucht, die Stücke schon vorzumastern. So werden die Tracks oft schon stark gelimitet angeliefert, um Lautheit zu erreichen. Lautheit und Lautstärke muss man unterscheiden. Die Lautheit entsteht zum einen durch die Auswahl der Sounds und den Mix und dann bei uns durch das Mastering. Die Lautstärke wird erst beim Umschnitt auf die Masterfolie bestimmt. Ein zu stark gelimitetes Master verstärkt einerseits die Gefahr für Verzerrungen und lässt andererseits praktisch keinen Spielraum mehr zur Bearbeitung. Die Devise muss sein: Weniger ist mehr. Ein Mastering-Engineer hört Musik anders als Musiker, eher analytisch, und kann die Endbearbeitung besser und effektiver machen. Bei Vocaltracks bietet es sich an, die S-Laute der Stimme zu de-essen, wenn dies nicht schon bei der Aufnahme passiert ist. Diese S-Laute neigen dazu, auf der Schallplatte zu zerren. Stereoeffekte auf einer Bassline oder Bassdrum können aufgrund der dadurch entstehenden Phasendifferenz zwischen den beiden Stereokanälen problematisch sein. Gerade bei Platten, die vor allem im Club gespielt werden sollen, ist es ratsam, den Bass mono zu halten. Andernfalls kommt es auf einer Club-PA zu Auslöschungen und die Bassdrum geht nicht mehr in die Beine. Das kann aber auch noch während des Masterings, vor dem Umschnitt geschehen. Man sollte auch wissen, dass die mögliche Lautstärke und Spiellänge einer Schallplatte mit anderen Faktoren wie Bass und Stereobreite zusammenhängen. Faustregel: Die Seitenlänge einer möglichst laut umzuschneidenden Clubmaxi sollte nicht länger als 12 Minuten sein.

Wo liegen die angesprochenen physikalischen Grenzen der Schallplatte?
Vinyl hat bei richtigem Umgang einen Frequenzbereich von 5 Herz bis über 25 Kiloherz und liegt damit eigentlich weit über den Möglichkeiten jedes digitalen Systems. Um diesen Frequenzbereich zu nutzen, müssen jedoch einige Voraussetzungen erfüllt sein. So liegen einige Probleme auf der Wiedergabeseite. Denn die Wiedergabefähigkeit der Höhen fällt je nach verwendetem Tonabnehmer mehr oder weniger proportional ab, desto weiter man sich dem Innenteil der Platte nähert. Man sollte daher – egal ob bei Maxis oder Alben – besonderen Wert auf das Tracklisting legen und die wichtigsten oder Höhen- und Attack-lastigsten Tracks möglichst weit außen platzieren.
Interessant ist es zum Beispiel, sich eine Schallplatte einmal mit einem HiFi- und dann mit einem gängigen DJ-Tonabnehmer anzuhören. Da gibt es große Unterschiede in Bass- und Höhenwiedergabe sowie Transparenz. Das hat mit der Abtastfähigkeit des Tonabnehmers zu tun. Viele DJ-Systeme sind nur auf Tracking und Lautstärke ausgelegt und werden mit ca. vier Gramm Auflagekraft betrieben. Mit solch einem System ist es nicht möglich, die feinen Auslenkungen, die eine Rille beschreibt, vernünftig abzutasten.

Wie wirkt sich der Unterschied zwischen 33rpm und 45rpm aus?
Eine Platte mit 45rpm hat durch die höhere Umdrehungsgeschwindigkeit eine sehr viel bessere Auflösung und ist daher für jeden Tonabnehmer leichter abzutasten. Das macht sich sowohl in den Höhen als auch im Bass positiv bemerkbar. Ein Schnitt auf 33rpm wird im Gegensatz dazu of als wärmer bezeichnet. Die Entscheidung, ob auf 33 oder 45rpm geschnitten werden kann, ist maßgeblich abhängig von der Seitenspiellänge und kann vor dem Umschnitt durch Testschnitte bestimmt werden.