Freetts is not working with external speakers

I have used Freetts.jar file in my java application that announces the token number. My application is working perfectly in my laptop but is not working in my desktop that has an external speaker. I get a null pointer exception. NOTE: I use Windows 7 in both my computers.

The Below Code is the Sample Format I used.

package tsapp;

import java.util.Locale;
import javax.speech.Central;
import javax.speech.synthesis.Synthesizer;
import javax.speech.synthesis.SynthesizerModeDesc;
import javax.swing.JOptionPane;
public class TextSpeech {
 public static void main(String[] args){
 try
 {
   System.setProperty("freetts.voices",
    "com.sun.speech.freetts.en.us.cmu_us_kal.KevinVoiceDirectory");

   Central.registerEngineCentral
    ("com.sun.speech.freetts.jsapi.FreeTTSEngineCentral");
   Synthesizer  synthesizer =
    Central.createSynthesizer(new SynthesizerModeDesc(Locale.US));
   synthesizer.allocate();
   synthesizer.resume();
   String str;

        str=JOptionPane.showInputDialog(null,"Voice Check");
        if(str==null)
        return;
        synthesizer.speakPlainText(str, null);
   synthesizer.waitEngineState(Synthesizer.QUEUE_EMPTY);
   synthesizer.deallocate();
  }
   catch(Exception e)
   {
       System.out.println(e.getClass());
     e.printStackTrace();
   }
 }
}

Can we do one simple thing:

1. Download binary https://netix.dl.sourceforge.net/project/freetts/FreeTTS/FreeTTS%201.2.2/freetts-1.2.2-bin.zip
2. Add to your project
3. Write simple code.

Like this

import com.sun.speech.freetts.Voice;
import com.sun.speech.freetts.VoiceManager;

public class TestVoice {


    public static void main(String[] args) {

        String text = "Voice check!";

        Voice voice;
        VoiceManager voiceManager = VoiceManager.getInstance();
        voice = voiceManager.getVoice("kevin");
        voice.allocate();
        voice.speak(text);

    }

}

Just be sure that all these libs are on your desktop too.