Members Plankeye Posted August 4, 2003 Members Share Posted August 4, 2003 I have a pair of EAW LA 1x18 subs (1,000W @ 8ohms) and a pair of EAW LA 1x12 mains (500W @ 8ohms). Which power amps would I need to buy out of the QSC RMX series? PLX series? And Microtech series? Link to comment Share on other sites More sharing options...
Members groove.77 Posted August 4, 2003 Members Share Posted August 4, 2003 Ask MrKnobs about using the PLXs for subs:D Link to comment Share on other sites More sharing options...
Members tlbonehead Posted August 4, 2003 Members Share Posted August 4, 2003 Originally posted by SoundtechSD Ask MrKnobs about using the PLXs for subs:D Or myself or Agedhorse for differing opinions. Those look like program ratings right? I certainly wouldn't put more than their program rating into them,probably a bit less. Personally,I would stick to about 600-700 watts to the subs and 300-400 for the mid/high cabs. Link to comment Share on other sites More sharing options...
Members agedhorse Posted August 4, 2003 Members Share Posted August 4, 2003 Originally posted by tlbonehead Or myself or Agedhorse for differing opinions. Those look like program ratings right? I certainly wouldn't put more than their program rating into them,probably a bit less. Personally,I would stick to about 600-700 watts to the subs and 300-400 for the mid/high cabs. That seems about right to me. I would choose the PLX if weight is a concern, otherwise the RMX 2450 is a pretty good value and it has the ol heavy weight transformer that makes Terry all war and fuzzy! Link to comment Share on other sites More sharing options...
Members 5slinger Posted August 4, 2003 Members Share Posted August 4, 2003 Terry (TBL) and Andy,Please explain quote:--------------------------------------------------------------------------------Originally posted by tlbonehead Or myself or Agedhorse for differing opinions. Those look like program ratings right? I certainly wouldn't put more than their program rating into them,probably a bit less. Personally,I would stick to about 600-700 watts to the subs and 300-400 for the mid/high cabs. --------------------------------------------------------------------------------I would run the subs with RMX bridged 2450 watts and use an RMX 1450 for the tops bridged or another 2450 using each side (about 400 watts per channel at 8 ohms).Is that what your saying? CJ:D Link to comment Share on other sites More sharing options...
Members agedhorse Posted August 4, 2003 Members Share Posted August 4, 2003 I prefer not to bridge amps if possible for reliability reasons. I think the RMX-2450 is a good choice on the subs in stereo too. 500 watts RMS is good, increasing to 700 watts adds about 1.35dB (barely audible) or so with reduced reliability on the sub driver. The Terry vs Andy thing refers to suitability of the PLX (or other) amps with switching power supplies to deliver suitable bass. I have not experienced the problem, but Terry has. We haven't found an explaination that makes sense to me yet. Link to comment Share on other sites More sharing options...
Members Kennykeys Posted August 5, 2003 Members Share Posted August 5, 2003 Originally posted by agedhorse "I prefer not to bridge amps if possible for reliability reasons." ///// On the other hand, I've been runnung the RMX2450 bridged mono at 4 ohms on subs for well over a year now with no probs at all. The RMX1850 is even more robust and a bit more in line with the appropriate power requirements. "I think the RMX-2450 is a good choice on the subs in stereo too. 500 watts RMS is good, increasing to 700 watts adds about 1.35dB (barely audible) or so with reduced reliability on the sub driver." //// What driver is in that LA Sub? Is it the RCF L-18-P 300? "The Terry vs Andy thing refers to suitability of the PLX (or other) amps with switching power supplies to deliver suitable bass. I have not experienced the problem, but Terry has. We haven't found an explaination that makes sense to me yet. " ///// I've seen this mentioned numerous times on the LAB too, PL or PLX amps having less balls when powering subs compared to Crown MA. Of course, it's often in the context of fairly big rigs with labor to wheel and lift amp racks, so who cares what it weighs. Link to comment Share on other sites More sharing options...
Members agedhorse Posted August 5, 2003 Members Share Posted August 5, 2003 Kennykeys, I can appreciate that you have not had problems running bridged. You are doing this with a single amp, and hopefully with proper and well maintained cabling which will reduce the chances for catastrophic failure. A single amp's history is not a statistically significant sample. My experience comes from real-world applications where faults do occur and amps do fail. Generally, an amp operated in bridged mode is more vulnerable to catastrophic failure under some fault conditions that a non-bridged amp may survive with little to no damage. I oversee service for a company that owns and operated about 2000 QSC amplifiers so I see a bit more of a cross-section of the applications. My comments about power levels into a single drive relate to reliability curves under real-world conditions where accidents happen, screw-ups and "un-controlled events" can apply full output to the speaker. Also, common sense and professionalism are not allways afforded to the sound system. Generally, a speaker will survive these "events" with higher reliability when powered by an amplifier between 1x and 1.25x the RMS rating of the driver. There are many failure modes, but in general this is true of most drivers in the marketplace. Under professional operation, with common sense and proper protection applied, drivers CAN be safely powered at 2x the RMS rating. Driven hard at 2x power rating will reduce the life of LF drivers due to extension into the suspension component's non-linear range. I am responsible for design reliability for many speaker products with 10's of thousands of drivers in operation world-wide. Reliability is very important to the overall success of a product line. Regarding switching power supplies and amplifiers, provided the amp is operated within the linear range (not clipped), I do not see how the power supply type could affect bass output. The power supply rails are independent of the amplifier until clipping occurs. When clipping occurs, the potential for artifacts exists, though I have not experienced anything that I could attribute to this on the PLX series. There may be differences in amplifier topology that could account for this (damping factor, output VI limiting, output impedence, frequency response, HPF style etc) but that would not involve the power supply. I am just providing some insight from the design and support side of the business, sometimes rumors and stories perpetuate themselves. of the facts get distorted and they become "urban myth". Link to comment Share on other sites More sharing options...
Moderators MrKnobs Posted August 5, 2003 Moderators Share Posted August 5, 2003 Originally posted by SoundtechSD Ask MrKnobs about using the PLXs for subs:D :mad: Sigh. I have a PLX3002, and have used other PLX's on many occasions. IMO, they completely suck as sub amps, they're not even remotely flat on the low end. They're.... bright. Bass players LOVE them because they all say something like "They're so clear! I can hear every note I play!" Which makes guitarists get that same look as the bassists have when we crank the bass on our Marshall stacks and step on THEIR toes. Sure, you can apply massive EQ to make them sound deeper, but then your headroom is gone, and you have to use several of them. That gets expensive, and negates the size/weight/current draw reasons you bought them in the first place. But don't take my word for it. Just A/B one next to a MacroTech or a K2 and you'll see what I mean, it's apples and oranges. Even my geriatric Peavey CS800 beats the 3002 on low end, at least until it's crowbar triacs sieze up. My K2s kill it. I confess I'm at a loss to understand why other experienced people have a difference of opinion on this. For a while, I considered that my PLX might be defective. After I'd heard more PLX's in operation, I knew they were all that way, ball-less. Why anyone would buy a PLX beats me. Sure, they're light weight and don't draw a lot of power, but then that description fits a styrofoam ice chest and those are only $3.50 and can't get the job done either. BUT... you can put your beer in an ice chest. The only thing I can guess is that opinions vary as to what bass is supposed to sound like. The PLX is certainly "articulate." On the other end of the spectrum, if a PLX ever wound up in the trunk of a hip hop guy, he'd immediately pull the car over and put a couple of well-deserved 9 mm rounds through it! As well he should. Terry D. P.S. Don't make the mistake we all did when we were getting started, and buy the cheap thing. Get a Crown K2 (lightweight, low draw, quiet, reliable power) or MacroTech (choice of most pros). Sure, that stuff costs more, 'cause it's the best. But how much will it end up costing you if you keep buying and selling because you're not happy with the cheap stuff you buy? Like Phil says, buy once, cry once. If you must go cheap, the QSC RMX stuff doesn't suck. Link to comment Share on other sites More sharing options...
Members Kennykeys Posted August 8, 2003 Members Share Posted August 8, 2003 Dear Andy Agedhorse, OK, we havn't been through this in a few months and some of these summertime newbies might have missed it, so....... 1) Of course I can appreciate your experience with the large quantity of installed amps. Now consider the typical small bar band: limited funds, limited truck space, do your own load in/out, limited AC power. The most prevelant need for amp power is the subs so do you carry several large amps and run each driver on it's own amp channel at 8 ohms, or do you bridge a smaller amp at 4 ohms and run two drivers with it while wringing every available watt out of the amp. Multiply my one amp situation by the thousands of similar set-ups and you're also looking at a considerable data base. Now, what kind of catastrophy is going to take down that bridged amp while the stereo-at-8-ohm amp might survive...a dead short? I agree, the potential for failure is there, but I really do wonder just how often does it occur? What percentage of the time? And is the security of the stereo-at-8 amp worth the extra cost/weight/space at gig after gig? Using today's robust amps (that CAN run all day in the tropical heat at 4ohms bridged mono on subs), I am more than willing to play the odds (and I don't even gamble. ) 2) I didn't take issue with you on the watts to driver thing. I just wondered what driver was in the box (too lazy to look it up.) And actually, you'd be proud to hear that I am reducing my sub power (somewhat) after I removed a dead RCF to find the cone had literally disintegrated (from fatigue ?) Anyway, a friend is building a whole slew of new bins, so it's "bring on the B&C's." 3) I don't know a damn thing about the switching power/no bass-balls issue. The posts I've read were not second or third hand...there were from system providers and/or engineers themselves who, like Mr. Terry Knobs, had done A-B comparisons or had just noticed the difference. 4) I promise not to respond to any of your posts for at least a month or so. Regards, Kenny Link to comment Share on other sites More sharing options...
Members agedhorse Posted August 8, 2003 Members Share Posted August 8, 2003 Kennykeys, On the bridged mode thing and subs, I prefer to run 2 drivers per channel (4 ohm load) and look for an amp in the 800 - 1200 watts per channel at 4 ohms. This is the best of both worlds... high reliability and reasonable number of amps.... reasonable power per driver too. I have yet to discover the reasons for the negative impressions for switching power supplies and sub amps. Sometimes you can hear something that's not there if your mind is "preped" for the experience. Reasonable sub power levels will pay big dividends in the long run. The 1 or 2dB SPL sacrafice is a very small trade-off. No replies for a month, I'll suffer from withdrawl! Link to comment Share on other sites More sharing options...
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