Pneumatic splice chambers are the industry method for splicing yarns. Most investigations in the literature occurred with ends-opposed splice chambers. For several applications, ends-together splicing is industrially interesting to consider. In this paper, we determine the importance of some process and splice chamber design parameters for ends-together splice chambers. We find that splicing pressure can be maximized, splicing duration needs to exceed a minimum duration and optimum splice length depends on yarn type and chamber design. Important splice chamber design parameters are chamber size and both yarn inlet and air inlet size relative to chamber size. This study also demonstrates the usefulness of three-dimensional printing to evaluate new splice chamber designs.