Report "Response Hi  Thanks for your quick response and helpful answers. I've done some research and since found out some interesting things about Shure and wireless mikes in general.  Consider the following; 1. In a theatrical environment where more than 2 mikes operate in proximity, I've been informed Shure is not the way to go. 2. The Sennheiser 100 and 300 series is a more superior and CHEAPER purchase. 3. Sennheiser is better built (German I believe) Shure is Chinese manufacture. 4. If you buy 1 X 300 series Senn, you get free software that from a laptop can scan your wireless environment for interference problems. 5. System Sound, one of the biggest operators in Australia, was offered the most expensive Shure mikes for FREE and they turned them down for quality reasons. 6. Sennheisers are metal cased and can be encased in rubber for water resistance and toughness. At this stage, but with more research to make 100% sure, I will be trading in the Shures for top of the line Sennheisers. In essence, replacing the whole system. Distance from mixer to receivers is approximately 10 metres by the way and there is a wall between them, so i'll check positioning there. Thanks for your help Cheers Paul"