, ▁a ▁large ▁reson ating ▁structure ▁is ▁not ▁required ▁to ▁project ▁the ▁sound ▁into ▁the ▁air . ▁This ▁minimal ▁body ▁greatly ▁reduces ▁the ▁bulk ▁and ▁weight ▁of ▁the ▁instrument . ▁E UB s ▁must ▁always ▁be ▁connected ▁to ▁an ▁ampl ifier ▁and ▁speaker ▁cabinet ▁to ▁produce ▁an ▁ade qu ate ▁aud ible ▁sound . ▁ ▁The ▁E UB ▁retain s ▁enough ▁of ▁the ▁features ▁of ▁the ▁double ▁bass ▁so ▁that ▁double ▁bass ▁players ▁are ▁able ▁to ▁perform ▁on ▁it . ▁ ▁Types ▁There ▁are ▁two ▁types : ▁solid - body ▁E UB s ▁and ▁h ollow body ▁E UB s . ▁Sol id - body ▁E UB s ▁have ▁no ▁h ollow ▁en closure ▁for ▁the ▁body ▁and , ▁as ▁such , ▁they ▁produce ▁almost ▁no ▁sound ▁without ▁electronic ▁ampl ification . ▁Sol id - body ▁E UB s ▁are ▁connected ▁to ▁an ▁ampl ifier ▁for ▁practice ▁and ▁live ▁performances . ▁H ollow body ▁E UB s ▁have ▁a ▁wooden ▁en closure , ▁which , ▁whilst ▁having ▁a ▁much ▁smaller ▁h ollow ▁body ▁cav ity ▁than ▁that ▁of ▁a ▁double ▁bass , ▁is ▁still ▁large ▁enough ▁to ▁give ▁the ▁instrument ▁some ▁sound ▁output ▁without ▁ampl ification , ▁at ▁least ▁for ▁individual ▁practice ▁in ▁a ▁small ▁room . ▁▁ ▁For ▁performing ▁it ▁is ▁connected ▁to ▁an ▁ampl ifier ▁and ▁speaker . ▁Wh ilst ▁the ▁E UB ▁retain s ▁some ▁of ▁the ▁t onal ▁characteristics ▁of ▁the ▁double ▁bass ▁but , ▁being ▁electron ically ▁ampl ified , ▁it ▁produces ▁it ▁its ▁own ▁unique ▁sound .