A mic with an omni polar pattern - so either a large/small diaphragm condenser (large with multi-pattern switching, or a small condenser with an omni capsule). The omni will pick up the sound of the machinery and the sound of the hall. With regards 'what mic', too many options as you've not stated a budget. Also, are you aiming to capture a stereo recording, or just mono? That will also determine mic selection. Also, is the machinery sound big deep and boomy, or shrill and high pitched. That will also be a factor in choosing a mic. What mics do you have at hand already?
thank you for the information. I´ll use an omni-pattern mic then. I´ll capture the machine sounds in mono, later i´ll mix spoken words to the machine sound ambience (it´s for a short movie). the machines sound deep, so there will be low freqencies in the spectrum also.
because I also need a mic for measuring/analyzing purposes, I have decided to purchase a beyerdynamic MM-1.
nevertheless, imho this will be a good investment, because i plan to record a lot of ambience sounds too.