I have a device that does this (among other things). It's a discontinued product called the Boomcloud Boomstick. It really does make mediocre headphones sound l

I have a device that does this (among other things). It's a discontinued product called the Boomcloud Boomstick. It really does make mediocre headphones sound like they produce deep bass. There have been other similar devices, particularly the SRS Wow! Thing is still popular among musicians, and commands high prices on eBay. I bought the Boomstick for a DIY BT speaker project, that I had to put on hold. I may pull myself together and actually finish it now :-)