If the horns on your motorcycle are like most blasters installed on modern motorcycles now-a-day, changes are that you not impress the average car when you hit the horn button. While the main culprit might be the horn themselves, a contributing factor to poor horn performance is often the simple fact that with some older motorcycles the horns are activated and powered by the horn button instead of being wired through a relay, as is common on most motorcycles you find currently in the dealer showrooms.
The problem is that switches – especially on some older motorcycle models – can be poor conduits for voltage. That's because they typically involve a pair of contact faces that wear against each other every time the switch is activated producing residue and attracting grime that diminishes the contact area and reduce the voltage passing through the switch. It's not at all unusual to discover that a powered switch with 12 volt fed into it only letting 9 or 10 volts through.
That kind of voltage drop is bad and can damage circuits, and it certainly doesn't encourage optimum performance in critical components like horns, lights and ignition systems. A switched relay, however, handles the actual voltage to the relay to tell it to open of close a circuit. Further, voltage drop in the switch becomes a minor concern as even a 6-volt signal will activate and hold most 12-volt relays. And while a relay still has a pair (or more depending on how many functions it controls) of contacts, they're housed in a sealed cartridge that typically lives under the gas tank or inside another hidden away location where it's protected from rain and other undesirable elements. That alone tends to improve their life span considerably.
If your motorcycle wasn't originally equipped with a relay, you could try to upgrade the electronics to a relay-activated system. You can buy 12-volt relays especially designed for automotive use for less than 250 THB, and they're not that difficult to install.