The efficiency of underwater low-frequency sound sources can be improved by using tunable high-quality resonators, increasing the emission aperture, or using source clusters. A very low frequency tunable resonator is hard to build. Large aperture sources are difficult to deploy. This study shows that the efficiency of a cluster of sources can be much higher than that of each source. Low frequency sources separated by distance operate independently, the sources add up the pressure, and the emitted pressure is proportional to the number of elements in the cluster. As a result, the radiated power of the cluster increases according to the quadratic law of the number of its elements, and the efficiency of the cluster increases in proportion to this number. To prove this, finite element modeling of an array of underwater sources was carried out. The simulation included the internal structure of each sound source with Helmholtz bubble resonators driven by standard audio 2 kW subwoofers. Indeed, the cluster efficiency increases when the distance between the sources exceeds several of their diameters. Simulations showed that a cluster of 32 broadband sources with a frequency of 10– 100 Hz could produce sound pressure levels equal to a standard air gun.