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Loamy 12th November 2012 06:29 PM

pair of JRX125s - use one EP2500 or two?
I have two JBL JRX125s on the way and I have two Behringer EP2500s. I'm thinking of running both amps into 4 Ohm mono, one per speaker...
Anyone have experience with a setup like this? Am I on crack and better off running one amp stereo at 4 Ohms or can I pull this off if I have a sense of discretion with the gain?

Power Capacity:
1 500 watts
Peak Power Capacity:

1 2000 watts
Recommended Amplifier
Power: 500-1000 watts @ 4 Ohms

Either it's 750 watts per channel in stereo with one amp or 2400 per amp if I run mono with one per speaker...

Any thoughts?

TMOY2000 13th November 2012 07:37 PM

hmmmmmmmmmm are these the only speakers you plan on running for your rig?..that's my first response......if so then aternativre to basic stereo wiring is possible yet I don't know about such efforts making the sound better....when figuring amp vs speaker rms it looks like this pair of speakers and using one of these amps is going to be just about right. actual use the Behringers will not bring the actual amperage to life as the stated power ratings..nothing against them it's just a natural fact as tested by many many pro users. .my experiences and that of my peers is usually about 15% less than stated actual live and loud may google other's results but i feel comfotable stating that ..others here please update me if I am incorrect!
Bearing that fact in mind, one also doesn't actually want to run their speakers wide open so to speak, for any length of time, unless an open budget for reconing and new diaphragms is an option, which none of us can afford nor would even contimplate I'm sure. So with the speakers advertising 500 watts @ 4ohm and the amps advertising 750 watts RMS in stereo @ 4 ohms you've got the perfect combination in my estimations. Bravo! (somehow this seems to be so hard for most to do, also it is one of the most debatable subjects to many) But think, to succeed with headroom to spare and not under-driving the speakers (death to voice coils) nor over driving the amp (death to amp, never use an amp rated below the speakers as bad things happen including fires!) many make it an easy calculation by suggesting whatever the speakers can handle simply double that in the power of the amp. Sure easy for the amp makers to say, but this can easily get us into a huge investment in money for headroom never used. More closely calculated is the idea of using amps rated at 50% more than the speakers maximum rated watts. And always use the RMS rating not peak nor the medium of usable unless you plan on getting out the scientific calculator and doing mucho math! Many say RMS is out dated but then again we are speaking in generalities and , well, EASY figuring of these things, I will anyways.
Also these JBL's are more of a Dj type of use speaker in my experience,I run JBL Sp-x series, older but higher power handling per transducer. Used for my medium p/a d/j rig and I have had many compliments and also questions on how these 15's respond with much more power than the JRX series some of my local friends/ competetors run. Altho very similar these speakers have much larger voice coils and what I call "true" HR drivers, 2426's vs the littler 2412s.
The LPF transducer of these speakers you have ordered are the M115-18 style rated at 250 watts RMS vs the SR-x series I have housing their 2226 LPF transducers.with an RMS rating of 600 watts each.
The reason I am trying to go thru all this is because I believe you'll possibly damage these JRX series speakers trying to run them with the mono set-up on these amps. Just too much power available and besides running any amps in bridged or mono increases the heat and fast...remember loss of sound is a bad bad thing in live work of any kind, in D/J work it can ruin your rep.which is hard gained and so easily lost!
These Behringers with their 750 rating run in stereo @ 4ohms should give you perfect response with your chosen speakers, one amp per pair run in stereo.besides the sound reproduction options running in stereo alone outweigh the more power mono use of this set-up, IMHO!.....
Right now I do actually ruin my 4725's in mono, but also bi-amped with one amp per side hf and one lf........just because to run them as designed costs alot more than I can afford right now...again most amplifier designers will suggest close to double the amp power rating vs. speaker rating for the desired effect plus headroom powering my speakers thus would require 1200 watt rms per side in stereo amplifiers, .......those dont come cheap so using my older crown amps I have had for years (altho heavy as stones these never seem to wear out nor give trouble, never have!) bridging them to 1600 watts per side allow me run two speakers per amp with power to spare! It's nice to have chest thumping sound with half or more of volume on the sliders to go at any given time, and still with the amps only occasionally turning their fans on
All that having been said, check this out.......Electro-Voice is the only brand I know of that actually designs their amps with 30% more power than they are rated, just to allow for enough headroom for any application.....also they can easily run @ 2ohm for hours at a time. Now unless one gets into the super amps of the top end (Crown, Electro Voice, Lab Gruppon, Crest Etc.) amps out there, such isnt possible nor feasable with the amps we run at the moment.
You didnt describe the point of use you are going for with this set-up, which of course is the basic starting point of it all.....but since you have these amps and have ordered these speakers I personally would recommend using one of these amps for stereo use, one speaker per side of the one amp.....adjusting the gain on the amp to about 75-80% should ensure perfect loudness with-out fear of any clipping didn't mention having or desiring to use any form of speaker controller devices, eq's or feedback destroyers so i remain with my suggestion on settings, although I highly recommend some for of eqing, over and above the board, and there are many combination devices that work well at the lower price points for these smaller systems, and they include delays, subversive clipping protection (instead of just shutting down the sound!) equalization and even reverb and time delaying variousparamiters as may be needed. The more the merrier, but alas so is the more options the higher the cost. I use an older EV speaker controller Dx34, which has way more options than i care to use but then again it does come in hany, altho it does take awhile to get used to.and tho many newer and better items are out since I have had this for years it suits the purposes just fine, amazingly so actually. So there you have it.much more than one bargained for i imagine but again, easy subjects are never so easy as they appear.........D.
This leaves your other Behringer amp for future possibilities such as running it mono for future subs....adding another pair of JBl's....etc etc.......also if you look into the various speaker controllers available, although they remain pretty high priced they offer great flexibility in the use of your sound system in the future. One can also consider using a cross/over to run your speakers bi-amped.again depending on the venue or desired use of these units remember, you have 4 15 inch tranducers and only two pretty small dirvers oin the top-end in the may bring this combination into a much better light depending once again one the actual desired use of the set-up. All in all the desired use is the basic integer,everything else developes following that specific, with-out it everything, including my meanderings written here, are a mute point actually..but here is some food for your thoughts.good luck let us know more about what you plan to use these for or what you actually decide to do and the reuslts reached for everyone's knowledge base!

Loamy 13th November 2012 09:06 PM

I heard it wasn't really worth it trying to bi amp a JRX125 but could be a bunch of hearsay...

Anyway for more info it's for live sound at a gallery that often holds events / weddings...
It's one main floor with a 2nd level loft space.

Originally had a really hoopty speaker set up with a crossover splitting the signal between the two EP2500s to a pair of tower speakers and some old JBL 4646a subs that fell in to my hands for free.

A lot of the conditions for the use of the system are out of my control so the concept is cheap and cheerful in case someone decides to destroy something in my absence.
Also the less speakers the better because I will constantly have to move them to accomodate for however the event is set up. I plan on running 50 ft 12 gauge speakon cables for better flexibility.

All the inputs come through a Pioneer DJM 800 mixer (some 1200s and CDJs)
Had a crossover but not using it any more with this set up.

The EQ has feedback detection and limiters but this system will probably never see a mic... (I'm saying this now but watch someone want a live band).

My thoughts were to go for bridging both amps (just because I have two available) and going for headroom and pulling down the input on the EQ to limit the damage of someone trying to turn up the gain all the way (big knobs being more attractive to mess with than the small ones with illegible text on the eq). By no means do I believe my "2400" watts is real but I also don't want to under power the speakers with 650/750 Behringer watts.

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