I believe need to remove front bumper to install. In my case, when I DIY install my PIAA horn. In order to remove the stock horn need to remove the center grill only can reach the bolt. I position my horns on the same location as the stock and not at the lower grill so removing the front bumper will have more ease of access to all the empty bolt holes to mount the brackets.

dear zeone,

thank you for reply me.
any tip for install only horn w/o open bumper,
my hand langsung x boleh masuk lar....
or u all install from bottom..?

zeone here's how my horn is fitted.

Got difference of L and R la....Civic is L Saga is...positive terminal in different direction but now I know the size is same then I can use the battery tie down kit for Civic FD

Tmr or friday will try and c, but need to buy new wire, wana redo all wiring. Damn messy antm wire degrated.