Projected constraints on in km with the second-generation ground-based detectors (top left), ET (top right), DECIGO/BBO (bottom left), and LISA (bottom right) for black-hole binaries with . The fixed values for and are shown at the top right of each panel. The constraints using the second-generation ground-based detectors have been obtained by assuming that the spins are known a priori. This roughly models projected constraints with precessing black-hole binary observations and may be correct within an error of 30%. For other detectors, binaries are assumed to be spin aligned (or antialigned). The colored contours show the regions of parameter space where the constraints on also satisfy ; thus, the small coupling approximation is satisfied at the fiducial luminosity distances chosen.