A good set of headphones will likely have better bass response than a hearing aid. For low frequencies, perhaps you're actually hearing them through the vent and not the hearing aid at all? If so, no fancy wireless connection will do as well.
I'm actually stone deaf at high frequency (I cannot hear a 'sh' sound, even with hearing aids) but have some amount of hearing at low frequency. It is possible that I'm hearing partially through my ear vent with the headphones but the hearing aids definitely assist.
