Cut 300 Hz with a wide Q.

That’s your starting point for taming muddiness without killing the lo-fi character. Julia Jacklin’s vocal recordings live in that warm, slightly boxy zone—it’s part of the aesthetic—but on a PA the low-mid buildup turns into a wooly mess.

Here’s the quick fix:

• High-pass filter at 100 Hz. You’re not reproducing sub bass. Anything below that is just stage rumble and mic thumps.
• Cut 3–6 dB around 250–400 Hz with a wide Q (0.7 or so). Aim at 300 Hz first, listen, and adjust. The wide Q keeps it musical instead of making the vocal sound hollow.
• If it’s still muddy after that, also try a narrow notch around 200 Hz. That’s where a lot of “bad room” energy sits. But don’t overdo it—you’ll turn her voice into a telephone.

One thing I’d skip: boosting high frequencies to “fix” muddiness. That only adds sibilance and noise. Clear out the low-mid gunk, and the air comes through naturally.

Trust your ears, not a chart.