This is a case for the HackRF Portapack H1 that comes with two mini speakers. There is a certain cavity inside the case, which is designed to enhance the bass effect.

However, these two speakers are still monophonic at present; the Portapack H1 does not support stereo output.

To enable the speaker under the Mayhem firmware: Go to the "Options/Interface" menu. The checkbox at the top must show a red "X". At this time, the speaker icon will appear at the top of the screen. Click to enable it

Speaker specifications: A pair of 8-ohm, 1-watt speakers, with dimensions of 28×9×4 mm.
Please connect them in series

I bought it from the KY WIN ROBOT store on AliExpress:
https://www.aliexpress.com/item/32923824898.html?spm=a2g0o.productlist.0.0.71ae25de7TZYOQ&algo_pvid=3460079d-0530-40c8-8761-bedaeda33767&algo_exp_id=3460079d-0530-40c8-8761-bedaeda33767-6

Please also refer to my other Portapack accessories:
https://www.thingiverse.com/thing:4892365
https://www.thingiverse.com/thing:4907118
https://www.thingiverse.com/thing:4924478