We recommend daisy-chaining your Flexes together with an XLR-to-TRS cable. Connect the female XLR end to your primary Flex's Mix Out output and the male TRS end to your secondary Flex's channel 1 or 2 input.
If you connect a straight XLR-to-XLR cable, the secondary Flex will distort! This is because the SRM-Flex interprets XLR input as mic-level audio and greatly boosts the input gain, resulting in clipping. Using a TRS connector bypasses this behavior and allows the second unit to treat the signal appropriately as line-level audio.
If using a mixer, the same rule applies. Use XLR-to-TRS cables from your main outputs to the inputs of each SRM-Flex to avoid clipping.
For more information or questions about Mackie products, please contact us here.