An obvious speaker hole is missing; instead there's just a tiny pin hole on the back. (the-ebook-reader.com)
Then pin the holes together, matching at the seams and sew. (acolourfulcanvas.com)
I found such a report, which claimed that the leaks are primarily due to formaldehyde in indoor air, which results in formic acid that eats pin holes in the newer thinner coils. (carlineconomics.com)