When sold, an Alto TS4 speaker is set for the region in which it was made. Alto Professional always recommends buying a speaker locally for the region you plan to use it in for compatibility.
Should you be travelling with the speaker, the process to change the speaker's voltage can only be done by an authorized service center without being considered a modification under the manufacturer's warranty. As it is not a process to repair damage to the speaker, the process would not be covered under a manufacturer's warranty or repair.
Please submit a new ticket at www.altoprofessional.com/support for more help in locating your closest a service center.