The min-height is set to 164px by default, you can change this on line 1954 in your css to around 70px or whatever you feel comfortable with –
.header-image .site-title a {
float: left;
min-height: 70px;
width: 100%;
}
Also, if you want to add some space to the top of the logo, add this code and adjust if needed –
.epik-black .head-wrap {
padding: 30px 0 0;
}