Amps for MRX sub

[heath_eld]

I've been upgrading my PA piece by piece of late. Brought some MRX512ms before christmas. Still working on getting the best out of them.

 

Some time i plan on upgrading my subs. Not immediately because i dont have the cash, but i like to plan these things.

 

have considered Peavey SP, as well as the more expensive SRX and QW. Could have had a killer deal on some QW 218s last week but just have no money...

 

Thinking probably the MRX. I think i will probably go 4x518 rather than 2 x 528.

 

I am upgrading from the old Behringer B1800pro powered by Yamaha P7000s.

 

My question is how would i best power these MRX. The mrx 518 is a 4 ohm box, so running 2 a side would give me 2 ohms. The Yamaha would do the job with the 528s (1100w at 4 ohm) but officially can't run to 2 ohm, and if it did, would really be too powerful.

 

Would i be better off with something like the RMX1850, Crown XTI 2000 or Peavey CS 2000 that would give me around a thousand watts at 2 ohm, or something more like 2 RMX... i think it was 1450 maybe? that would give me 4 channels at 500w each channel 4 ohm?

 

Practically each has its advantages (weight versus flexibility) but i mean for sound and reliability.

 

Sorry if that doesnt make perfect grammatical sense, on the train.

[agedhorse]

The 1850HD would be fine, even the 2450 would be ok (with a little common sense). Use the 30Hz HPF's.

 

The singles are easier to deal with than the 218's, especially in tight spaces or stairs.

[heath_eld]

Actually... thats what i meant... the 2450 for the 2 ohm and the 1850 if i was to run with 4 ohm...

 

other amp suggestions of course welcome... the RMX are heavy but they seem well respected and cheap enough.

[NUSound]

Honestly, using the 1850 is just more conservative than the 2450, 2 or 4 ohm operation. If you're planning on operating at 2 ohms most of the time, I'd opt for the 2450. That having been said, I've found that there is a sort of stigma against running at 2 ohms... (I don't buy into it).

 

 

 

Has it ever been reasoned out why JBL opted to use a 4-ohm driver in the 518's?

[heath_eld]

 

Has it ever been reasoned out why JBL opted to use a 4-ohm driver in the 518's?

 

 

Wish i knew... i guess they were more focussing on people who use one each side, and want to get the full power out of their amps.

 

Is there any sort of, documented evidence of there being a problem with running amps which are designed to be run at 2 ohmm, like the RMX, at 2 ohm?

[Bugzie]

Well I know at the time the 518 came out there were a few amps that pushed 750 WPC at 4 ohms. If you wanted to push the sub at 1.5 times the RMS value it was easy to find an amp that met that mark. Maybe Andy can give a remark, but I feel much safer pushing the MRX series closer to the RMS value. I run the 528's off a PL236 QSC in stereo and have never been left wanting any more in a club. Outside would be a different story of course. At 1100 WPC channel they perform well enough. Outside I have bridged a pair of 2450's into them, but limited them at something like -8db. I forget what the calculation came up to. I wish I had a pair of 1450's to bridge into them.

[heath_eld]

Do you generally like the MRX subs in that price point?

[ckcondon]

I have 2 MRX subs run with a 2450 in stereo. Good combo!

[jwlussow]

To my ears, the MRX subs are one of the best at that price point.

[dcastar]

Call me crazy, but I think doubling 2 MRXs a side would be foolish. Why not get a single SRX's per side and a bigger amp. If you ask around... (cough: Mike Pyle) it would probably cheaper too! Not to mention less stuff to carry around and setup.

 

Or delving deeper into the proverbial rabbit's hole...

 

- If you're set on 2 MRX's a side, grab the MRX528s, stick with 4 ohms so your amp doesn't scream for mercy.

- Have you considered the PRX718s? It's a powered version of the SRX's.

[tombo007]

I just went from 4 MRX518's using a XTi4000 to 2 SRX718's and I am very happy. I using the XTi4000 in Bridge mono. (I have more room in my Edge) I play in a 4 pc classic rock bandand we don't get too loud. But those 718's do a real nice job on the dance floor and fill the room with good solid bass.

 

Question: I will be using my MRX512m for monitor duty now.

What would be HPF for those boxes? 80-90 or 100.

[RoadRanger]

Call me crazy, but I think doubling 2 MRXs a side would be foolish. Why not get a single SRX's per side and a bigger amp.

+1 , less expensive, louder and lower. Unless you need the exercise of carrying around a bunch of extra cabs ? Actually you don't need a bigger amp - a bridged RMX1850HD would be about perfect I'd think?

[agedhorse]

+1 , less expensive, louder and lower. Unless you need the exercise of carrying around a bunch of extra cabs ? Actually you don't need a bigger amp - a bridged RMX1850HD would be about perfect I'd think?

 

This is not accurate.

 

2 MRX-518's would be louder and go lower (or as low as) than a single 718. This is due to LF coupling as well as the net increase in power without the issues of power compression.

 

The tradeoff is the additional cabinets.

[agedhorse]

 

I just went from 4 MRX518's using a XTi4000 to 2 SRX718's and I am very happy. I using the XTi4000 in Bridge mono. (I have more room in my Edge) I play in a 4 pc classic rock bandand we don't get too loud. But those 718's do a real nice job on the dance floor and fill the room with good solid bass. Question: I will be using my MRX512m for monitor duty now. What would be HPF for those boxes? 80-90 or 100.

 

 

Somewhere around 80Hz is fine.

[agedhorse]

 

Call me crazy, but I think doubling 2 MRXs a side would be foolish. Why not get a single SRX's per side and a bigger amp. If you ask around... (cough: Mike Pyle) it would probably cheaper too! Not to mention less stuff to carry around and setup. Or delving deeper into the proverbial rabbit's hole... - If you're set on 2 MRX's a side, grab the MRX528s, stick with 4 ohms so your amp doesn't scream for mercy. - Have you considered the PRX718s? It's a powered version of the SRX's.

 

 

Why would the amp scream for mercy? 2 ohms is a valid load, and the RMX/PLX amps do not have a problem with this.

[lifeloverwg]

 

Call me crazy, but I think doubling 2 MRXs a side would be foolish. Why not get a single SRX's per side and a bigger amp. If you ask around... (cough: Mike Pyle) it would probably cheaper too! Not to mention less stuff to carry around and setup. Or delving deeper into the proverbial rabbit's hole... - If you're set on 2 MRX's a side, grab the MRX528s, stick with 4 ohms so your amp doesn't scream for mercy. - Have you considered the PRX718s? It's a powered version of the SRX's.

 

 

+2

Better sound for less dollars and weight. Of course, 4 x MRX would look louder than 2 x SRX.......

 

My experience is that if QSC says their amp will run at 2 ohms it will and it will sound good doing it.

 

Winston

[agedhorse]

 

+2 Better sound for less dollars and weight. Of course, 4 x MRX would look louder than 2 x SRX....... My experience is that if QSC says their amp will run at 2 ohms it will and it will sound good doing it. Winston

 

 

Not just look louder, but sound louder too.

 

The sensitivities are almost identical, the tuning is higher on the MRX but that changes when 2 boxes are coupled.

 

Calculate out the two options, correct for power compression, and the MRX's are louder. My guess is that the -10dB points will merge to within a couple of Hz of each other.

 

Also, it should be noted that the 718 is a pretty large box... quite a bit larger than the 518.

 

If maximum volume per cubic volume or per minimum number of cabinets is what's important, then a single 718 would be a better choice but if it's maximum volume per dollar then perhaps the 518 would be better. It alos allows for scalability.

[RoadRanger]

 

2 MRX-518's would be louder and go lower (or as low as) than a single 718.

From JBL docs:

MRX528S = Frequency Response (

[Rezrover]

Multiple subs wouldn't change the specs, louder but no lower than a single cab, right?

[rotebass]

1. Dimensionally, the 718 is deeper than the 518, but the 518 is actually 2" or so taller than the 718.

 

2. 2x518 does not equal 1x528.

 

I have used the 728 and 718 many times, I've used the 518 a couple times but I definitely prefer the 718 for the little bit of extra coin.

[RoadRanger]

Multiple subs wouldn't change the specs, louder but no lower than a single cab, right?

Front loaded subs gain about 5hz on the low end when you couple a pair. Horn loaded subs generally gain more than that. Many of the latter sound best (both smoother and go lower) in clusters of 4 or more.

[zbad55]

Just to add my .02 cents, here, I currently run 2 MRX518's off a QSC PLX3402 at a 2ohm load, and I have haven;t had any problems with the amp. The amp is designed for 2ohms so why would it be a problem?

 

I think if I ever needed more subs then I would add a couple more of the MRX518's, that would provide some flexibility to allow me to scale based on the gig, and I do like the weight of the single 18 vs a double 18 cab,

[The Chinese]

I don't perceive my LA400's (horn loaded) going that much dramatically lower when I couple them in a cluster of 4. Maybe a total of 6Hz for all 4.I think it has to do with the box.

 

T

[The Chinese]

 

Outside I have bridged a pair of 2450's into them, but limited them at something like -8db. I forget what the calculation came up to. I wish I had a pair of 1450's to bridge into them.

 

 

-8db? Then why bridge the 2450? You're better off with the 236. A 2450 Limited to -8dB would deliver less than 1/4 power, which would be

 

Todd

[Rezrover]

 

Front loaded subs gain about 5hz on the low end when you couple a pair. Horn loaded subs generally gain more than that. Many of the latter sound best (both smoother and go lower) in clusters of 4 or more.

 

 

Really? Learn something new everyday.