This is easy. Just chase a used NAD 7100, 7400 or 7600 receiver.
They had a Bass EQ switch that pumped up the bass from 35-80 Hz or so, with a steep drop below 30Hz. This is pretty effective with WELL-DESIGNED 5 or 6 1/2" two-ways that don't have noisy ports (that as well are tuned below 60Hz or so). Gives good extension WITHOUT the excess warmth of a regular tone control. You have to start with a decent speaker, though. The other nice thing is that you could leave this EQ in and still bypass the other controls for a cleaner signal. Yet the preamp as a whole was the weakness of these receivers...the FM tuners the highlight. Still using my 7400 in the HT/second system.
They had a Bass EQ switch that pumped up the bass from 35-80 Hz or so, with a steep drop below 30Hz. This is pretty effective with WELL-DESIGNED 5 or 6 1/2" two-ways that don't have noisy ports (that as well are tuned below 60Hz or so). Gives good extension WITHOUT the excess warmth of a regular tone control. You have to start with a decent speaker, though. The other nice thing is that you could leave this EQ in and still bypass the other controls for a cleaner signal. Yet the preamp as a whole was the weakness of these receivers...the FM tuners the highlight. Still using my 7400 in the HT/second system.