QSC RMX vs PLX for subs

Is this amp OK?
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tactix
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QSC RMX vs PLX for subs

#1 Post by tactix » Mon Oct 05, 2020 12:26 pm

Hello all,

I'm trying to sort out what amp to buy (likely used) to power four 3012LF loaded T30s that will be used a a portable PA for DJ sets - mostly outdoors. Given the need for a reasonable amount of headroom and accounts of reliability I have my sights set on either the RMX 4050 (or 4050a) and the PLX 3602. I'm wondering if you might be able to offer me some perspective on which way to go. I've been told and read that the toroidal transformers of the RMX series deliver bass with more authority but I'm looking at the 68lb weight of the 4050 and it definitely gives me pause as I'll be moving it around. I'm also a little concerned about the power draw from both these amps maxing out a typical electrical circuit ( 20A or maybe 15 A) and how they will perform on a generator. The RMX 4050 supposedly draws 10 A at 1/8 power pink noise at 4Ω vs the PLX 3602 which draws 11.5 A. Is there an advantage either way with these in terms of their draw? Add a second amp for tops (2x OT12s with Deltalite II 2512) , a small monitor, booth lights, driverack, plus a bunch of DJ gear (turntables, mixer, fx units, cdjs) and I fear a need a second circuit. Has this been your experience with a similar setup? I haven't investigate the world of generators as of yet for such a system if you have any thoughts about that as well they would be most appreciated.

Which of these would you choose if you were setting up the system I described or would you go in another direction entirely? If so, why?

I look forward to your reply.

Bruce Weldy
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Re: QSC RMX vs PLX for subs

#2 Post by Bruce Weldy » Mon Oct 05, 2020 3:22 pm

I don't see any reason for heavy iron amps on a system of that size. You could run that whole rig on 3 Crown XLS 1500s. Two of 'em bridged with two subs each - plenty of headroom. The other one for the four OTops. All three amps will come in at 30 pounds....total.

I run 3-1500s for my 6 subs (3012LF). 1 XLS2500 for the 4 OTops, a four channel monitor amp, mixer, 3 driveracks and a couple of fans on a a single 15A GFCI outdoors and have never tripped a breaker. Been doing it for several years for several shows each summer.

6 - T39 4-25" 2-22" 3012LF
4 - OT12 2512 Melded/NSD2005
1 - T24
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

Grant Bunter
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Re: QSC RMX vs PLX for subs

#3 Post by Grant Bunter » Mon Oct 05, 2020 3:36 pm

You haven't mentioned what driver you're planning to use in your T30 cabs, but if it's the 3012lf, it has a voltage limit of 50-55V.
At 4 ohms (2 cabs per channel in parallel) that's 625W-750W/channel.

IMO opinion, you don't need 1100-1300W/channel for headroom because you're brick wall limiting, but each to their own.
I would choose the 3602 over the 4050 all day every day now I am older, based on amp weight...
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" BP102 , 2 x 28" 3012lf.
WH8: x 3 with melded array.
Bunter's Audio and Lighting "like"s would be most appreciated...

Seth
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Re: QSC RMX vs PLX for subs

#4 Post by Seth » Mon Oct 05, 2020 4:15 pm

Grant Bunter wrote:
Mon Oct 05, 2020 3:36 pm
...
tactix wrote:
Mon Oct 05, 2020 12:26 pm
...to power four 3012LF loaded T30s...
Build in process - 2 WH6, one Alpha 6a loaded, one PRV Audio 6MB250-NDY loaded

Two 2x6 shorty SLA Pro's
One T39, 16", 3012LF loaded
Tall AutoTuba, 20" wide, 2x 8" MCM 55-2421
TruckTuba, 8½" wide, 2x 8" MCM 55-2421

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tactix
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Re: QSC RMX vs PLX for subs

#5 Post by tactix » Mon Oct 05, 2020 9:46 pm

Grant Bunter wrote:
Mon Oct 05, 2020 3:36 pm
You haven't mentioned what driver you're planning to use in your T30 cabs, but if it's the 3012lf, it has a voltage limit of 50-55V.
At 4 ohms (2 cabs per channel in parallel) that's 625W-750W/channel.

IMO opinion, you don't need 1100-1300W/channel for headroom because you're brick wall limiting, but each to their own.
I would choose the 3602 over the 4050 all day every day now I am older, based on amp weight...
Thanks Grant, the next model down in the PLX line is the 3102 which is 900 W @ 4Ω or 60v. That means pushing the amp to about 83%-92% capacity does it not? I was worried that was pushing it.
The 3602 gets up to 66v @ 4Ω which means running the amps closer to %76-%83 of their rated power output. I guess you're saying I'm being overly conservative. Would the additional headroom not provide some sonic improvement? Scouring the forum suggests the amp would be more reliable if it's not being driven as hard. I guess the advantage of the RMX series amps is they can be reliably driven to 2Ω so adding an extra sub per channel is doable.
Bruce Weldy wrote:
Mon Oct 05, 2020 3:22 pm
I don't see any reason for heavy iron amps on a system of that size. You could run that whole rig on 3 Crown XLS 1500s. Two of 'em bridged with two subs each - plenty of headroom. The other one for the four OTops. All three amps will come in at 30 pounds....total.

I run 3-1500s for my 6 subs (3012LF). 1 XLS2500 for the 4 OTops, a four channel monitor amp, mixer, 3 driveracks and a couple of fans on a a single 15A GFCI outdoors and have never tripped a breaker. Been doing it for several years for several shows each summer.
Thanks Bruce, I hadn't thought about bridging. How are the 1500's setup in your system with 6 subs? It's good to hear about your experience running a system sized as yours is on a single circuit - assuages my fears.

Grant Bunter
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Re: QSC RMX vs PLX for subs

#6 Post by Grant Bunter » Tue Oct 06, 2020 3:55 am

Gees you guys are harsh lol.
Sorry, I missed it..
tactix wrote:
Mon Oct 05, 2020 9:46 pm
Thanks Grant, the next model down in the PLX line is the 3102 which is 900 W @ 4Ω or 60v. That means pushing the amp to about 83%-92% capacity does it not? I was worried that was pushing it.
The 3602 gets up to 66v @ 4Ω which means running the amps closer to %76-%83 of their rated power output. I guess you're saying I'm being overly conservative. Would the additional headroom not provide some sonic improvement? Scouring the forum suggests the amp would be more reliable if it's not being driven as hard. I guess the advantage of the RMX series amps is they can be reliably driven to 2Ω so adding an extra sub per channel is doable.
Ok, tin tacks.
If you're regularly hitting the limiter, very simply put, you don't have enough subs. If you hit the limiter maybe once or twice a song, just briefly, then you're all good IMHO.
Trying to extract every last bit of output out of cabs is flawed thinking in the long run.
So you don't really want to be running a 3102 amp to 60V.

You mentioned earlier you were worried about draw with regard to amps earlier.
If we stick with the figures you mentioned based on the 3102 then at 60V/4ohms per channel there is also 15amps on the output stage, and if you go towards 2 ohms per channel, that becomes 30 amps. That power has to come from somewhere, and while it is designed to withstand that load, it is the harshest on the amp operation.
All things that need considering.

Bruce bridges XLS1500's. I bridge a XLS1000 for my pair of 3012lf loaded T39's. There's never been a time when I've hit the limiter, because I take enough subs for the job at hand (yes, even though 4 of mine a "only" BP102's which I have limited on an amp that puts out 450W/4ohms).

Like Bruce, I've done plenty of shows over the year with one wall outlet. That's been made a heap easier with the advent of LED lighting, and more efficient class D and class H amps etc.

My current thinking, because I have drivers in hand, may be to build a pair of dual loaded cabs utilising series/parallel wiring for an 8 ohm load on a channel. Same volts, least amps, least draw...
Built:
DR 250: x 2 melded array, 2x CD horn, March 2012 plans.
T39's: 4 x 20" BP102 , 2 x 28" 3012lf.
WH8: x 3 with melded array.
Bunter's Audio and Lighting "like"s would be most appreciated...

Bruce Weldy
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Re: QSC RMX vs PLX for subs

#7 Post by Bruce Weldy » Tue Oct 06, 2020 8:33 am

tactix wrote:
Mon Oct 05, 2020 9:46 pm

Thanks Bruce, I hadn't thought about bridging. How are the 1500's setup in your system with 6 subs? It's good to hear about your experience running a system sized as yours is on a single circuit - assuages my fears.
Each XLS1500 runs two subs in bridged mode. It delivers about 1500 watts at 4 ohms bridged, so there's ample headroom. Of course the limiter is a must. I know some don't like bridging - but it made sense with this line of amps as the 2500 didn't quite have enough headroom to run two per side. It's made for an inexpensive solution that has worked for me for several years.

And most importantly, in all those years of running this way I have never lost a single driver in a sub. I have two brand new 3012LFs in my inventory just sitting there waiting to be called into service......I guess it was cheap insurance.

6 - T39 4-25" 2-22" 3012LF
4 - OT12 2512 Melded/NSD2005
1 - T24
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

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tactix
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Re: QSC RMX vs PLX for subs

#8 Post by tactix » Tue Oct 06, 2020 10:04 pm

Grant Bunter wrote:
Tue Oct 06, 2020 3:55 am
If you're regularly hitting the limiter, very simply put, you don't have enough subs. If you hit the limiter maybe once or twice a song, just briefly, then you're all good IMHO.
Trying to extract every last bit of output out of cabs is flawed thinking in the long run.
So you don't really want to be running a 3102 amp to 60V.
Got ya. Yes, my thinking was a bit skewed by the fact that I had previously been running a small sound with one T30 I built and yes, I had been running that right up against the 50-55v limit as a result, trying to eek as much out of the sub as I could. My take away here is that the program output from the sub amp should on average be peaking at say 40v or 45v on the regular with an occasional hot 50+v that gets limited. That would mean a 60v amp would be running around %75 capacity which does seem more reasonable. At the risk of being reminded that hi-fi is not pro sound, my understanding (which has borne out in my limited experience) is that higher output capable amps run at a fraction of their capacity (25%-60%) tend to sound better (punchier bass for instance) than smaller amps driven harder. That's coloring my thinking here as well. But it sounds like the 3102 at 60v is plenty if I'm not driving them to the limit. Or I get the 3602 which offers a bit more power or start bridging with smaller amps as Bruce is suggesting. The only advantage of bridging into 4 ohms that I'm clear on from this discussion is more headroom. That suggests maybe the 3602 makes sense after all if I want to keep it to one amp.
Bruce Weldy wrote:
Tue Oct 06, 2020 8:33 am
Each XLS1500 runs two subs in bridged mode. It delivers about 1500 watts at 4 ohms bridged, so there's ample headroom. Of course the limiter is a must. I know some don't like bridging - but it made sense with this line of amps as the 2500 didn't quite have enough headroom to run two per side. It's made for an inexpensive solution that has worked for me for several years.
Good to know this is a reliable path forward. This gives me some options. - Thanks for that.

nick mineau
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Re: QSC RMX vs PLX for subs

#9 Post by nick mineau » Mon Nov 23, 2020 2:02 pm

I have some first hand experience comparing a plx3602 to a rmx4050hd...

#1 the weight will not matter as far as the "sound", they will (sound) identical to the ear, as I have heard on a double blind test.
#2 the 4050HD has very slightly higher output power @ 2 ohms. 1800watts vs 2000watts. under 1/2 of a db difference . (humans cant even detect that difference)
#3 the 4050HD will run cooler, due to the larger fan, 3u rack, and better cooling system. This however wouldn't be a issue unless driven very hard into 4ohm bridge, or 2 ohm per ch loads.
#4 for normal sub duty, I vote for the PLX3602, unless driving 4ohm bridge loads, on 110deg days, into hard clipping, at which point id want the 4050hd;s better cooling.

Thought, also look for a used plx3402, less $$$ basically same amp. just make sure it was built past 2002 when they had ribbon cable issues. :fingers:

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Re: QSC RMX vs PLX for subs

#10 Post by tactix » Tue Dec 01, 2020 10:15 pm

Thanks Nick,

This is very helpful. Great to hear from someone with experience with these amps. I ended up going with the PLX series but the smaller 3102 as I got a decent deal on a relatively recent one. If it gives me problems driving the four T30's with 3012lfs I can move it to the tops and get a 3402 as you suggest or a 3602. The 3102 is 60V into 4 ohm vs 3402/3602 which are 66V. Not sure how much difference that headroom would make.

Thanks again.

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Re: QSC RMX vs PLX for subs

#11 Post by tactix » Fri Dec 04, 2020 7:29 pm

Folks - I have an opportunity to purchase a plx 1602 or a 2402 built in 2000 and 2001 respectively at a reasonable price. Do you know if the ribbon cable issue Nick referred to with the 3402 applied to the whole line?

Planning to use this on two delta lite ii 2512 loaded Otop 12s. Might get the bigger one to be able to run 4 if i expand at some point.

Bruce Weldy
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Re: QSC RMX vs PLX for subs

#12 Post by Bruce Weldy » Fri Dec 04, 2020 8:05 pm

tactix wrote:
Fri Dec 04, 2020 7:29 pm
Folks - I have an opportunity to purchase a plx 1602 or a 2402 built in 2000 and 2001 respectively at a reasonable price. Do you know if the ribbon cable issue Nick referred to with the 3402 applied to the whole line?

Planning to use this on two delta lite ii 2512 loaded Otop 12s. Might get the bigger one to be able to run 4 if i expand at some point.
A 1602 will run 8 OT12s with 2512s with no problem.....4 will be a walk in the park. I doubt that my OT12s have ever seen 150 watts a piece in all the years I've run 'em.

6 - T39 4-25" 2-22" 3012LF
4 - OT12 2512 Melded/NSD2005
1 - T24
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

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Re: QSC RMX vs PLX for subs

#13 Post by tactix » Fri Dec 04, 2020 8:50 pm

Bruce Weldy wrote:
Fri Dec 04, 2020 8:05 pm
tactix wrote:
Fri Dec 04, 2020 7:29 pm
Folks - I have an opportunity to purchase a plx 1602 or a 2402 built in 2000 and 2001 respectively at a reasonable price. Do you know if the ribbon cable issue Nick referred to with the 3402 applied to the whole line?

Planning to use this on two delta lite ii 2512 loaded Otop 12s. Might get the bigger one to be able to run 4 if i expand at some point.
A 1602 will run 8 OT12s with 2512s with no problem.....4 will be a walk in the park. I doubt that my OT12s have ever seen 150 watts a piece in all the years I've run 'em.
Well that just saved me a little dough. Thanks Bruce. I had found a couple threads about people limiting Otop12s and was sizing based on that.

Bruce Weldy
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Re: QSC RMX vs PLX for subs

#14 Post by Bruce Weldy » Fri Dec 04, 2020 9:04 pm

tactix wrote:
Fri Dec 04, 2020 8:50 pm
Bruce Weldy wrote:
Fri Dec 04, 2020 8:05 pm
tactix wrote:
Fri Dec 04, 2020 7:29 pm
Folks - I have an opportunity to purchase a plx 1602 or a 2402 built in 2000 and 2001 respectively at a reasonable price. Do you know if the ribbon cable issue Nick referred to with the 3402 applied to the whole line?

Planning to use this on two delta lite ii 2512 loaded Otop 12s. Might get the bigger one to be able to run 4 if i expand at some point.
A 1602 will run 8 OT12s with 2512s with no problem.....4 will be a walk in the park. I doubt that my OT12s have ever seen 150 watts a piece in all the years I've run 'em.
Well that just saved me a little dough. Thanks Bruce. I had found a couple threads about people limiting Otop12s and was sizing based on that.
I'd keep 2512s limited around 35volts.....

Anyway, you really want two pair of those anyway.....they won't need as much power each and they sound even better when you stack up two of em. They just get smoother and richer sounding. I use all 4 of mine whether I'm playing to 50 people or 500.

6 - T39 4-25" 2-22" 3012LF
4 - OT12 2512 Melded/NSD2005
1 - T24
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

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Re: QSC RMX vs PLX for subs

#15 Post by tactix » Sun Dec 06, 2020 2:16 pm

Bruce Weldy wrote:
Fri Dec 04, 2020 8:05 pm

I'd keep 2512s limited around 35volts.....

Anyway, you really want two pair of those anyway.....they won't need as much power each and they sound even better when you stack up two of em. They just get smoother and richer sounding. I use all 4 of mine whether I'm playing to 50 people or 500.
Yes I believe I've read in your previous posts that they sound better stacked. I'll try them mono that way and check it out. Two more would be great. Thank you for your suggestion on the limiting- I'll try that. I ended up getting the 1602. It was in excellent shape as it was a backup amp in an install. That also means it has probably not seem much of a workout over its life. Hopefully it proves to be reliable.

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