diff --git a/pixelle_video/services/tts_service.py b/pixelle_video/services/tts_service.py
index cef60d3..0432e28 100644
--- a/pixelle_video/services/tts_service.py
+++ b/pixelle_video/services/tts_service.py
@@ -219,10 +219,10 @@ class TTSService(ComfyBaseService):
         # 2. Build workflow parameters
         workflow_params = {"text": text}
         
-        # Add optional TTS parameters
+        # Add optional TTS parameters (only if explicitly provided and not None)
         if voice is not None:
             workflow_params["voice"] = voice
-        if speed != 1.0:
+        if speed is not None and speed != 1.0:
             workflow_params["speed"] = speed
         
         # Add any additional parameters
@@ -259,19 +259,28 @@ class TTSService(ComfyBaseService):
             # Check for audio files in result.audios (if available)
             if hasattr(result, 'audios') and result.audios:
                 audio_path = result.audios[0]
+                logger.debug(f"✅ Found audio in result.audios: {audio_path}")
             # Check for files in result.files
             elif hasattr(result, 'files') and result.files:
                 audio_path = result.files[0]
+                logger.debug(f"✅ Found audio in result.files: {audio_path}")
             # Check in outputs dictionary
             elif hasattr(result, 'outputs') and result.outputs:
+                logger.debug(f"Searching for audio file in result.outputs: {result.outputs}")
                 # Try to find audio file in outputs
                 for key, value in result.outputs.items():
                     if isinstance(value, str) and any(value.endswith(ext) for ext in ['.mp3', '.wav', '.flac']):
                         audio_path = value
+                        logger.debug(f"✅ Found audio in result.outputs[{key}]: {audio_path}")
                         break
             
             if not audio_path:
                 logger.error("No audio file generated")
+                logger.error(f"❌ Result analysis:")
+                logger.error(f"   - result.audios: {getattr(result, 'audios', 'NOT_FOUND')}")
+                logger.error(f"   - result.files: {getattr(result, 'files', 'NOT_FOUND')}")
+                logger.error(f"   - result.outputs: {getattr(result, 'outputs', 'NOT_FOUND')}")
+                logger.error(f"   - Full __dict__: {result.__dict__}")
                 raise Exception("No audio file generated by workflow")
             
             # If output_path provided and audio_path is URL, download to local