Need help with cab and head matching...?
spacemissing: A few facts
A few facts: Power output is continuous Only if there is a Continuous Signal at a Constant Level. This is Very Rare with individual instruments because there are spaces, however small they may be, between notes. An electronic keyboard can hold a note indefinitely; a guitar can't without outside help (such as a loop pedal). Most of the time, with a typical amplifier, the actual output power is continuously varying from a tiny fraction of a watt to maybe 5 or 10 watts if the volume is turned up "generously" (loud, but not to maximum). The number of drivers in the cabinet makes No difference. What Does make a difference is the composite impedance presented by the entire cabinet. Using speakers of Higher impedance than specified will Never do any harm to an amplifier unless it is Very delicate. In most cases, using a Lower impedance than specified will cause no harm. Only when the limits are pushed does damage readily occur. Solid state amplifiers are by their nature relatively tolerant of wide variations in speaker impedance. Higher impedance loads will reduce the actual power output, but this Doesn't Matter in most cases. And yes, you can safely use a 16-ohm 300-watt cabinet with a 100-watt 8-ohm amplifier. As with any other sound system, if you hear anything that sounds bad, Reduce The Volume Immediately.
Short answer...your sound guy is wrong. The guy who sold you the amp is right. You will not damage the amp or cab as long as you keep the volume level reasonable.
Well I'm maybe old-fashioned here but I'm not any kind of electronics expert and I'd just go with what was received wisdom when I started playing over forty years ago and the only people giveing advice were experts: the impedance of the amp and the cab need to match. Note that some amplifiers are able to cope with a range of impedances.