As I recall, the Dataproducts band printers BP1000, BP2000 only had a single hammer per column. But the band containing the full character set moved so quickly into position for each column that the print speed was incredible. We had both models at one point and the 2000 was an absolute screamer.
Paper just flew over the paper guides to the collection basket in the rear.

It was impressive and incredible to watch in action. 

The bands were easily replaceable via a release lever.  So you could change fonts,  replace damaged bands, etc. 
Sharp as heck as I recall on the edges.
You also had to make sure it lined up just right before engaging the tension lever.

With cover down, they were remarkably quiet in comparison to other "high speed" printers I had been around. Real good at multipart forms at making clean clear impressions on the backmost layer.

On Mon, Mar 29, 2021, 5:16 PM Erik E. Fair <> wrote:
Technically, the DEC DECwriter series were dot-matrix printers, not line printers. They differed from their Teletype predecessors only in print-head technology, but both printed a single character at a time. Daisywheel printers were similar.

Line printers are distinguished not by the width of the paper but by the printer having enough print heads to print an entire line of output at a time. That speed advantage made them the preferred output device for many-page program listings, as opposed to a teleprinter terminals which were more suitable for interactive computing.

There were dot-matrix line printers of the late 1970s made by Printronix, which is apparently still around.

        Erik Fair