A visit — yours or an inspector's — is the surest check on a new supplier. Send a date and what you want to see; the request reaches them as an enquiry you can track.
Address
GUANGZHOU SHUANGLONG AUDIO CO., LTD 2nd floor, Building 3 , Unit 2,2nd floor Building 1,No. 32, Zhushui First Road, Jianggao Town, Baiyun District, Guangzhou