One of the perennial favorite articles in Horn Matters is on the topic of Kruspe or Geyer. Both terms reference the names of classic horn makers (Kruspe still being in business [UPDATE: see the comments]), but both terms in a sense have also become generic terms. How makers work out their individual horn designs will vary a bit, there is no one successful Kruspe or Geyer design but rather many subtle variations on themes.
Which brings us to the topic of Knopf or Geyer. Conventional wisdom is they are similar horns, and many use the terms interchangeably. The essential visual difference is the Knopf has the tube come out of the first valve at an angle and the Geyer has this tube straight across the instrument.
A good place to see a lot of horns is the ever-useful Horn-U-Copia website, the source of these photos. First up is this image of a Knopf horn, and about the maker I would note right away they are still in business (website here). Which is probably why makers don’t often refer to their instruments as being Knopf-style instruments, as Knopf still sells them! Horn-U-Copia dates this instrument to around 1960, but the Knopf family goes way back as a maker of horns of this type to the early 20th century and has been making brass instruments in Markneukirchen, Germany since 1852. Presently this type of instrument is their Model 16.
Then we get to Geyer. According to his bio in the IHS website, German native Carl Geyer (1880-1973) “became an apprentice instrument maker at age 15 in Markneukirchen” and
While working in a music store in 1903, he saw an advertisement in a Leipzig newspaper that Richard Wunderlich was seeking a horn maker because musicians in Chicago were forced to send their instruments to Germany for repairs. Geyer immigrated to the US and arrived in Chicago in 1904. He worked for Wunderlich until Wunderlich retired during World War I.
In 1920 Geyer opened his own workshop to help meet the great demand for American-made horns. His Chicago shop was widely known for both his distinctive horns and his repair service. In 1955, at age 75, he sold the business but continued working for the new owner until he was 90.
The horns he was famous for were ones of this design, again seen in this image from the Horn-U-Copia site. Visually you can see a few dimensions are a bit different. The Knopf pattern opens up the space where the valve mechanism is a bit more so it can potentially be a bit better for valve action. There are also a lot of other dimensions subtly different, the most visible being the leadpipe length and the overall wrap. Where you would notice the latter is fitting the horn in a case; often Geyer-style horns need a little larger case than a horn inspired by the Knopf version of this wrap.
With those two classic makers described, it is worth noting also that their products varied a bit over the years of production. Which brings us to the topic of “almost” Geyer or Knopf horns, there are many ways to vary the basic wrap and still be visually similar, especially at a distance. Every maker has their own take on how to best address specifics of design toward getting the best result.
If I had to pick one I would tend to pick Knopf if only for the elegant look of the bend going into the first valve. This does not get at the topic of which is better though, as honestly both types can be great. Try them both! In the end it is all about the build and the way the maker has worked out the various small dimensional differences toward making a product that meets their expectations.
And for another article getting at the above topic that is one of the most frequently read in Horn Matters see Thoughts on ‘Quality’ and an Overview of Trusted Brands in French Horns.