problem with POST angular5 method?

It turns out that I am doing a project with angle 5 and when saving an audience in my case ... it shows me as a result a [Object Object]

I would appreciate a hand!

service

audiencias(anio: string, mes: string) {
  const httpParams = new HttpParams()
    .set('anno', anio.toString())
    .append('mes', mes.toString());
  const options = { params: httpParams };
  const uri = AudienciaApiUris.audiencias;
  return this.http.get<any[]>(uri, options);
  }

guardarAudiencias(audiencias) {
  const payload = audiencias
    .map(event => {
      return {
        codSala: event.codSala,
        fechaAudiencia: event.start
      }
    })
    ;
  return this.http.post(AudienciaApiUris.audiencias, payload)
    .pipe(
      tap(result => console.log(result)),
      map(() => 'Audiencias creadas exitosamente')
    );
  }

component

private _crearAudiencias(audiencias) {
this.agendaService
  .guardarAudiencias(audiencias)
  .takeWhile(() => this.alive)
  .subscribe(
    msg => this.snotifyService.success(msg),
    errMsg => this.snotifyService.error(errMsg),
    () => this.audiencias = []
  );
}