I have looked around but only found discontinued projects. What audio equalizers are able to be used in 15.10.
The PulseAudio-Equalizer is the best for Unity and Gnome desktop environment. It has 15-band Graphic Equalizer with many presets available and it's completly integrated with Audio-Indicator on system tray of Ubuntu 15.10 Wily Werewolf and also with VLC media player and Popcorn Time.
To install, just follow the steps below:
sudo add-apt-repository ppa:nilarimogard/webupd8 sudo apt-get update sudo apt-get install pulseaudio-equalizer
There are 2 PulseAudio EQs I know of: qpaeq and pulseaudio-equalizer (ladspa-sink). The issue I ran into with PulseAudio EQs is that they tend to introduce audio latency and crackling/popping sounds when starting/quitting applications on my hardware (Xonar DX).
The best solution I came up with is to use the JACK audio server that is used for professional audio production on Linux and put that between PulseAudio and ALSA (the hardware connection). This allows for various EQ modules to be applied on a low-latency basis while still keeping the PulseAudio interface for your applications, so you don't have to adjust them in any way.
It is a rather non-invasive approach; you can give it a try using my guide here: https://github.com/M4he/Linux/tree/master/JACK/PA_through_JACK