Audio Recorded File too large on ios7 but not on ios8. Both with same audio recorder setting

Question

Via AVAudioRecorder I do a 16 second audio recording then upload it on a server via AFNetworking 2.0

On iOS 8 everything is fine. But when running on iOS7 the server returns file is too large(code:413).

-(void)viewDidLoad{
    file_url_str = @"audioFile.m4a";
    audio_duration = 15.0;
    [self initAudioRecorder];
}

-(void)initAudioRecorder{
// Setup audio session
    AVAudioSession *session = [AVAudioSession sharedInstance];
    [session setCategory:AVAudioSessionCategoryPlayAndRecord error:nil];

    NSURL * audio_file_URL = [NSURL fileURLWithPath:[NSTemporaryDirectory() stringByAppendingString:file_url_str]];
    NSDictionary * audio_Settings = [NSDictionary dictionaryWithObjectsAndKeys:
                                 [NSNumber numberWithFloat:44100],AVSampleRateKey,
                                 [NSNumber numberWithInt: kAudioFormatMPEG4AAC],AVFormatIDKey,
                                 [NSNumber numberWithInt: 1],AVNumberOfChannelsKey,
                                 [NSNumber numberWithInt:AVAudioQualityMedium],AVEncoderAudioQualityKey,nil];
    audio_recorder = [[AVAudioRecorder alloc]initWithURL:audio_file_URL
                                            settings:audio_Settings
                                               error:nil];

    audio_recorder.delegate = self;
    [audio_recorder prepareToRecord];
}

-(void)recordBtnPressed:(id)sender{

    //[[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryRecord error:nil];

    record_btn.selected = !record_btn.selected;
    if(record_btn.selected){

        AVAudioSession *session = [AVAudioSession sharedInstance];
        [session setActive:YES error:nil];

        [audio_recorder recordForDuration:16.0];

    }
}

-(void)stopRecording{
   [audio_recorder stop];
}


#pragma mark - AVAudio Delegate Selectors
#pragma mark -
 -(void)audioRecorderDidFinishRecording:(AVAudioRecorder *)recorder successfully:(BOOL)flag{
   NSLog(@"done record");

    AVAudioSession *audioSession = [AVAudioSession sharedInstance];
    [audioSession setActive:NO error:nil];

    [self initAudioPlayer];
    [self setData];

}


-(void)initAudioPlayer{
    NSURL * audio_file_URL = [NSURL fileURLWithPath:[NSTemporaryDirectory() stringByAppendingString:file_url_str]];
    audio_player = [[AVAudioPlayer alloc] initWithContentsOfURL:audio_file_URL error:nil];
    audio_player.delegate = self;
}

-(void)setData{
    NSString * audio_file = [NSTemporaryDirectory() stringByAppendingPathComponent:file_url_str];
    //This is the data sent to the server
    audio_data = [[NSData alloc]initWithContentsOfFile:audio_file];
}




AFNETWORKING 2.0 
- this is under a subclass file of AFHTTPSessionManager
//This is how I set the serializer
//"self" pertains to AFHTTPSessionManager

    self.responseSerializer = [HAJSONResponseSerializer serializer];
    self.requestSerializer = [AFJSONRequestSerializer serializer];

#pragma mark - Audio Upload
#pragma mark -

-(void)uploadAudio:(NSData *)audioFile{
    [self setTokenHeader]; //method that sets token header

    [self POST:@"/users/song/record" parameters:nil constructingBodyWithBlock:^(id<AFMultipartFormData> formData) {

    [formData appendPartWithFileData:audioFile name:@"profile_song" fileName:@"profilesong.m4a" mimeType:@"audio/mp4a-latm"];

} success:^(NSURLSessionDataTask *task, id responseObject) {
    //if (success) success(responseObject);
    if([self.delegate respondsToSelector:@selector(HAHTTPClient:audioUploadRequestSuccessful:)]){
        [self.delegate HAHTTPClient:self audioUploadRequestSuccessful:responseObject];
    }

} failure:^(NSURLSessionDataTask *task, NSError *error) {

    if([self.delegate respondsToSelector:@selector(HAHTTPClient:audioUploadDidFailWithError:)]){
        [self.delegate HAHTTPClient:self audioUploadDidFailWithError:error];
        }
    }];
}