I am doing some research and am hoping that Mr. Atkinson could share with me which speakers he has measured in the past decades has the narrowest dispersion. The reason is I am looking for speakers that will least interact with a room. 

I am aware that many ESL dipoles have fairly narrow dispersion. E.g., the Innersound/Sanders. Are these the most narrow dispersed designs? What about for dynamic cone speakers? Horns?

Thanks.