Configuring limits in a usercontrol
There are quite a few issues in this code to worry about on top of the virtual call in the constructor...
abstract public class MatlabData:eSoundMaster

The accessibility modifier should always come first and classes in C# are always PascalCase.
public abstract class MatlabData : ESoundMaster

You are using public readonly fields in the base class:
 public readonly int numTonspuren = 32;


It's usual to have public readonly fields use PascalCase
You then hide them with constants in the derived class and pass them to the base class's constructor. Don't hide the fields!

Don't abbreviate in your code. If you are going to, be consistent about it. E.g. nTonspuren vs numTonspuren.
Methods in C# should be PascalCase. isEQAMAvailable should be IsEQAMAvailable. That said, EQAMAvail should be a readonly property and the method should be removed.
In general, and without a good reason not to*, one should prefer properties to fields in C#. It's idiomatic to do that and it's an extra level of abstraction and leaves you free to change how that property is implemented without breaking consumers.
From the example, it's not clear why you have a class hierarchy at all here. It looks like you need one class with a factory:
// Typed directly on CodeReview, apologies for errors.
public class LabelDefinition 
{
    public string Text { get; }
    public string Name { get; }
    // etc.
}

public class MatlabData : eSoundMaster
{
    public bool EQAMAvail { get; }
    public int NumTonspuren { get; }
    public int NumSubgroups { get; }
    public int NumStandardTS { get; }
    public int NumPremiumTS { get; }
    public int NumOutputs { get; }
    public int NumSoundtrackLUTs { get; }

    public MatlabData(
        int numTonspuren, 
        int numIntermediateMixerChannels, 
        int numStandardTS, 
        int numPremiumTS,
        LabelDefinition[] labels,
        string[] additionalLabelNames)

    {
        NumTonspuren = numTonspuren;
        NumSubgroups = numIntermediateMixerChannels;
        NumStandardTS = numStandardTS;
        NumPremiumTS = numPremiumTS;
        LabelText = labels.Select(l =&gt; l.Text).ToArray();
        LabelName = labels.Select(l =&gt; l.Name).Concat(additionalLabelNames).ToArray();
        // etc.
    }
}

public class MatlabDataFactory
{
    public MatlabData CreateDefault =&gt; new MatlabData(...);
}

*There are vanishingly few reasons to use a public field over a property.