  I study the diffuse flux of electron antineutrinos from stellar collapses
with direct black hole formation (failed supernovae). This flux is more
energetic than that from successful supernovae, and therefore it might
contribute substantially to the total diffuse flux above realistic detection
thresholds. The total flux might be considerably higher than previously
thought, and approach the sensitivity of SuperKamiokande. For more conservative
values of the parameters, the flux from failed supernovae dominates for
antineutrino energies above 30-45 MeV, with potential to give an observable
spectral distortion at Megaton detectors.
