The 1-meter-on-axis frequency response of the KM 150/185 is attached below (with the KM 145 shown for comparison, since it is specifically sold as a "speech cardioid").
For more distant sound sources, the bass reduction would be greater than shown. Proximity effect affects a microphone more, the more it's based on the pressure-gradient pickup principle rather than the pressure pickup principle--and that means that there's more proximity effect with figure-8, hypercardioid and supercardioid microphones than (for example) cardioids.
HOWEVER, since the polar pattern of the KM 150/185 is essentially the same at all frequencies, it is very amenable to equalization. If you make a recording with them, have no fear of trying to boost the bass in playback or post-production. If the room was better than you anticipated, you can restore more of the missing bass.
But on the third hand, it is remarkable how a smooth, gradual bass rolloff can be acceptable to the ear. That's not to say that the low-frequency energy wouldn't be welcome if it can be returned to the recording; it's just that the reduction can change the illusion without necessarily destroying it, to a degree that might surprise a person. Typically, a classic "speech cardioid" is about -12 dB at 50 Hz in the type of measurement shown, while the KM 150/185 provides about 2/3 of that, which is a useful way to split the difference, I think.