Members RyanC Posted December 8, 2014 Members Share Posted December 8, 2014 Brochures and manuals for these amps say they are fine running a 2 ohm load on each side, but a local sound engineer I talked to at a gig last night said I shouldn't go below 4 ohms, even with those amps. I have been running up to (3) 8 ohm mains/tops per side with the 1850HD and up to (3) 8 ohm subs per side with the 4050HD. Should I not do that? Link to comment Share on other sites More sharing options...
CMS Author Craig Vecchione Posted December 8, 2014 CMS Author Share Posted December 8, 2014 The manuals are correct, these amps are fine down to 2 ohms. However, speaker impedances are variable depending on the frequency, and it's possible that the impedance at any given moment could be lower than 2 ohms. This usually isn't a problem, but if you're pushing the rig hard, you could eventually have problems. It's also a good idea to both have more rig than you need (so you aren't pushing it hard all the time) and to not run into the minimum impedance...in the event that something does fail, it's good to have the ability to double up a speaker set on one amp channel to make it through a gig. If you're already using the amp at minimum impedance, you don't have that flexibility. So all being said, the person you talked with is essentially right. Link to comment Share on other sites More sharing options...
Members mkfs9 Posted December 8, 2014 Members Share Posted December 8, 2014 Yeah. He said you shouldn't, not couldn't. Link to comment Share on other sites More sharing options...
Members soulx Posted December 8, 2014 Members Share Posted December 8, 2014 Note that we aren't even talking about a 2 ohm load here. This is a 2.667 ohm load, so there's a fudge factor already in play. In my experience with the 1850HD, I've driven 2 ohm loads hundreds (maybe thousands?) of times over probably a decade without a hitch.. YMMV Link to comment Share on other sites More sharing options...
Members agedhorse Posted December 9, 2014 Members Share Posted December 9, 2014 The HD after the model number indicated a power supply modified specifically for 2 ohm, higher duty cycle operation. Link to comment Share on other sites More sharing options...
Members RyanC Posted December 11, 2014 Author Members Share Posted December 11, 2014 The HD after the model number indicated a power supply modified specifically for 2 ohm' date=' higher duty cycle operation.[/quote'] And that's the reason I got those 2 amps (the 1850HD and 4050HD), so that I could run 1, 2 or 3 8 ohm speakers/side depending on the size of the gig. So I should be fine, right? Link to comment Share on other sites More sharing options...
Members nchangin Posted December 11, 2014 Members Share Posted December 11, 2014 Well from personal experience a 2450 doesn't like a 2 ohm load for more than about 5 hours...then it starts becoming unstable. Also the time before it shuts down depends on environment the amp is in, i.e., humid-hot. Link to comment Share on other sites More sharing options...
Members Dookietwo Posted December 11, 2014 Members Share Posted December 11, 2014 I had 2 1850 HD amps and they were fine at 4 ohm bridged , 2\3 ohm per channel loads. Other than the weight they are great amps. The 4050 is a monster as far as output and weight. ☺ Dookietwo Link to comment Share on other sites More sharing options...
Members witesol Posted December 11, 2014 Members Share Posted December 11, 2014 those QSC HD amps can run 2 ohm loads all day.. Link to comment Share on other sites More sharing options...
Members agedhorse Posted December 12, 2014 Members Share Posted December 12, 2014 And that's the reason I got those 2 amps (the 1850HD and 4050HD), so that I could run 1, 2 or 3 8 ohm speakers/side depending on the size of the gig. So I should be fine, right? Yes, IMO, correct. Link to comment Share on other sites More sharing options...
Members agedhorse Posted December 12, 2014 Members Share Posted December 12, 2014 Well from personal experience a 2450 doesn't like a 2 ohm load for more than about 5 hours...then it starts becoming unstable. Also the time before it shuts down depends on environment the amp is in, i.e., humid-hot. Right, but do you see the HD after the model number on the 2450??? The 2450 is NOT designed for high duty cycle 2 ohm loads (per channel) or 4 ohms bridged. Link to comment Share on other sites More sharing options...
Members RoadRanger Posted December 12, 2014 Members Share Posted December 12, 2014 It's my understanding that the 1850HD is basically a 2450 that's had it's rail voltages cranked down so that it can run 2 ohm loads 24/7. Same relationship between the 4050HD and the 5050 ... Link to comment Share on other sites More sharing options...
Members agedhorse Posted December 12, 2014 Members Share Posted December 12, 2014 Correct, the changes improve SOA margins and thermal dissipation. Link to comment Share on other sites More sharing options...
Members dboomer Posted December 12, 2014 Members Share Posted December 12, 2014 in other words they have traded maximum output for thermal stability and operating with lower impedance loads. Link to comment Share on other sites More sharing options...
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