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Help powering my JBL MRX528S Dual 18" Subwoofer


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Im having trouble getting power to the subwoofer. When I get it all connected the sub does not sound...... well almost not at all. I have to turn off the speakers and blast the bass all the way up to hear it. Now it was a used product but do not think it has been damaged. When I can hear it, it sounds very clean and has the potential to blast! But I think the amp is not powering the sub. Im using a behringer ep4000 amp bridged mode. Connected from the sub output of the mixer, and connected to the sub from output one using a speakon cable. There is an option to use banana plugs on the amp bridge mode to speakon, but dont think thats the problem. I thinnk it atomatically bridges the output 1 so I shouldnt need the banana plugs, but not sure. I need help........ could it be a damaged sub?????!!!:confused:

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Im having trouble getting power to the subwoofer. When I get it all connected the sub does not sound...... well almost not at all. I have to turn off the speakers and blast the bass all the way up to hear it. Now it was a used product but do not think it has been damaged. When I can hear it, it sounds very clean and has the potential to blast! But I think the amp is not powering the sub. Im using a behringer ep4000 amp bridged mode. Connected from the sub output of the mixer, and connected to the sub from output one using a speakon cable. There is an option to use banana plugs on the amp bridge mode to speakon, but dont think thats the problem. I thinnk it atomatically bridges the output 1 so I shouldnt need the banana plugs, but not sure. I need help........ could it be a damaged sub?????!!!
:confused:

if it isn't, it will be.

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Good God, you are lucky it didn't make any sound and that you don't understand what you were doing, it may have saved you from an expensive accident.

 

First of all, whe would you even consider using that amp in bride mode? Did you read about it in some DJ magazine? The amp delivers roughly 2400 watts into 4 ohms bridged and your speaker is only rated at 1000 watts RMS and unless you know exactly what you are doing, you should really stock to an amp that delivers around 1000 watts RMS, maybe even a little less.

 

What happened (I am reasonably sure) is that you have an error in the way you are driving the amp relative to the operating mode you have selected. Thinking that it works the way you do, I suspect that you have misread (or was told incorrectly) how things operate on bridge mode.

 

BUT, it doesn't really much matter, since I would recommend that you go back to stereo mode and use only one channel. That will get you around 750 watts RMS which is a far better match and you won't need to wory about the technical aspects of bridging.

 

It is possible that your speaker was damaged by somebody else overpowering it, but not as likely as what I suggested above.

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Good God, you are lucky it didn't make any sound and that you don't understand what you were doing, it may have saved you from an expensive accident.


First of all, whe would you even consider using that amp in bride mode? Did you read about it in some DJ magazine? The amp delivers roughly 2400 watts into 4 ohms bridged and your speaker is only rated at 1000 watts RMS and unless you know exactly what you are doing, you should really stock to an amp that delivers around 1000 watts RMS, maybe even a little less.


What happened (I am reasonably sure) is that you have an error in the way you are driving the amp relative to the operating mode you have selected. Thinking that it works the way you do, I suspect that you have misread (or was told incorrectly) how things operate on bridge mode.


BUT, it doesn't really much matter, since I would recommend that you go back to stereo mode and use only one channel. That will get you around 750 watts RMS which is a far better match and you won't need to wory about the technical aspects of bridging.


It is possible that your speaker was damaged by somebody else overpowering it, but not as likely as what I suggested above.

Yea I dont think the speaker is damaged.......supposedly tested and guarenteed to wrk from where i bought it....... and like I mentioned it sounds very clear and deep. No distortion at all. Just very low. Like the amp is not powering it or somthing. But yea I am new at setting up my own PA system. So I dont need to bridge it then. But when it says "1000 watts continuous with a 4000 watt peak" i thought it ment up to 4000 watt

 

Some specs

 

Frequency range: 35Hz-250Hz

Frequency response: 40Hz-250Hz

Sensitivity: 97dB SPL; 103dB SPL

Nominal impedance: 4 ohms

Power capacity (continuous/program/peak): 1000W/2000W/4000W

Rated maximum SPL: 133dB SPL (139dB SPL)*

Coverage pattern: 70 x 70 nominal

Dimensions: 21"W x 43"H x 27.5"D

Weight: 121 lbs.

*Calculated on half space condition

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A 1000 watt amp does deliver 2000 watts peak, it's just a math conversion... 2 ways of sayingthe same thing. Unfortunately the marketing folks present it differently to try to sell more product. All of us engineers here cringe at this misleading tactic.

 

Another, even bigger suggestion is to get a proper crossover, this will eliminate the sub information from the top cabinets. The difference is substantial.

 

The symptoms you describe are typical of what I posted as your most likely problem.

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You should power near the cont power rating for music playback. The problem with this is that you will be driving the amp near clip for most of the gig. I have been there and done that. I suggest using an amp rated a little higher than the cont. rating so that when there are peaks in the music, your amp does not clip. Just do not use something much higher than 2000rms.

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You should power near the cont power rating for music playback. The problem with this is that you will be driving the amp near clip for most of the gig. I have been there and done that. I suggest using an amp rated a little higher than the cont. rating so that when there are peaks in the music, your amp does not clip. Just do not use something much higher than 2000rms.

 

 

I disagree completely.

 

If you are driving (or planning to drive) the amp to near clip (or limiting in the case of the amp being discussed, as with the limiter engaged the amp can't clip) and you find yourself needing more power, you need more speaker too.

 

In the case that you do drive the amp into limiting, the average power increases which adds thermal stess to the driver. The same can be said of playback of compressed (typical) program material.. even moreso for playback versus live.

 

This is a subwoofer, not a full range passivly crossed over speaker... I am assuming that you are regurgitating (parroting) something that you heard but do not fully understand. Care to explain why your advice is good???

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So from what I understand is that the amp I am using is too powerfull, so no need to bridge it........or buy another with less power. And that a crossover may solve the problem....... well i thought a crossover just seperated the hi mids and lows. Thus leaving me with jus the signal I need. But my mixer already has a sub out......And i am indeed just recieving the lows. But it just seems that the amp isnt even powering the sub. I have to crank the volume on the amp all the way just to hear the sub very weak. Sounds like I am directly connecting the mixer to the sub without an amp.

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Man, you need to find somebody locally to help you. Somebody who really understands what they are doing. You are headed down the road to a potentially expensive end. I hate to ask what high pass filter setting you are using, and if the amp's limiters are indeed enabled.

 

No crossover... not good. The Sub out on your mixer is a feble attempt at kludging together something that will kinda-sorta work, but is a poor solution. I wish these manufacturers would quit making the sub out feature as well as bridging switches on non-professional amps. Yes I know, your amp has the words professional all over it and the manual and the advertising, but it's not a professional amp, in fact, it's an entry level amp with entry level performance and is geared for the throw away, kinda-sorta works mentality.

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Yea Im not really getting a defintive answer, that maybe what i have to do. But if any one else has any other suggestions.....please by all means help!

 

 

Is your speakon cable even wired right? You're not getting any sound because I am ASSuming it is wired for 1+ 1-. And you are in bridged mode. Hint hint

 

Second, try running the amp in stereo and run the sub off of one channel. Tell us if this works and sound goods.

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If you are plugging a standard speakon cable into output 1 of the amp you will not get bridged output, whether the amp is in bridged mode or not. Not sure about the Behringer, but the way most amps work you will still only get channel 1 output unless your cable is wired to the 1+/2+ termination in the NL4 speakon. This should still make your subwoofer thump unless you are doing something else wrong on the input side.

 

You would only want to use the channel 1 input in bridged mode, and the channel 1 gain knob. Keep the channel 2 gain knob turned off.

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Yea Im not really getting a defintive answer, that maybe what i have to do. But if any one else has any other suggestions.....please by all means help!

 

 

Do your own homework is the "defintive answer", spend some time reading manuals before assuming things work the way you think they work.

No crossover?

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Yea Im not really getting a defintive answer, that maybe what i have to do. But if any one else has any other suggestions.....please by all means help!

I have barely any more expertise in this area than you, but one thing I do know is that if someone as knowledgeable as Aged Horse is telling you that you are perilously close to a massive {censored} up then STOP what you are doing.:cop:

 

As far as definitive goes I'd say what you need to know is:

1) Leave bridging to those who really know what they are doing (and I don't include myself there)

2) Use a crossover

3) Power your speakers at about their RMS (or continuous) rating

4) Don't be confused by people talking about using much more powerful amps than the speakers RMS, they're either experts who understand how to apply the correct filters and limiting or lucky fools living on borrowed time.

 

This is a useful guide to power http://www.peavey.com/support/technotes/poweramps/HOW_MUCH_POWER.pdf if you can't be bothered to read it all the most important bit is

If you are looking for a recommendation so that you would be relatively free of

blowing up the speaker under almost any real world condition, you should pick

an amplifier that can deliver the continuous rating of the speaker or a little less.

 

If I was in your position I'd first run the amp in stereo and power the sub off one channel giving it 700w, but remember that even though the speaker is capable of handling 300w more than that, you can still damage it by allowing clipping to take place so make sure the amps limiter is turned on and keep an eye on your mixer level.

 

If you're up for spending some cash I'd then look into a crossover and an amp that can deliver 1000w into the 4Ohm of your speakers, alternatively you could get an amp like the forthcoming Peavey IPR1600 that will give you the necessary power and also has a foolproof crossover built in.

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Actually having looked at the spec the EP4000 puts out 950W per channel RMS into 4Ohm, so it is pretty much on the money as far as the power you need is concerned, just get yourself a crossover. You'll also find that removing the bass from your mains will improve their performance too so forget about the sub output on your mixer and send the main out to the crossover and then split it between sub and tops, you should get a much improved sound all round :thu:

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Good god do not bridge that amp into that speaker! If it were me , I would take everything out of your signal chain except for your console , sub amp and speaker(s). Before plugging the speakers into the amp , play some music or something through the board and make sure youre getting a strong signal to the amp , if you are , turn the amp down , plug in the speaker and turn the amp back up a bit. Not too awful loud because you will not have the signal crossed over. If it works , start adding pieces of your signal chain back in until it stops working. It will help you isolate the problem. Under NO circumstances though do you ever want to put that kind of power to that box! I ran those with 1200 watts and they performed fantastic.

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Actually having looked at the spec the EP4000 puts out 950W per channel RMS into 4Ohm, so it is pretty much on the money as far as the power you need is concerned, just get yourself a crossover. You'll also find that removing the bass from your mains will improve their performance too so forget about the sub output on your mixer and send the main out to the crossover and then split it between sub and tops, you should get a much improved sound all round
:thu:

 

Actually, looking closer at their advertised specs, you will also see the math error that incorrectly corrolates the continuous power to the peak power in continuous stereo mode. The conversion they used is correct for bridged mode however. The EP-4000 does 750 watts per channel at 4 ohms, not 950 watts. They use the .707 factor conversion incorrectly on the power figure, not the voltage as is necessary.

 

Red numbers are incorrect.

 

Output Power

20 Hz

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There should be some kind of law stopping the publishing of incorrect/misleading specs, for someone like me who doesn't know the math all I have to go on is what the spec sheet shows. So thanks for pointing that out.

 

In an ideal world there would be an independent, standardised speccing procedure for all equipment, giving each item an ISO spec sheet so you really could compare like for like and make appropriate partnerships between amps and speakers. Dream on though eh...?

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agedhorse..

 

I have setup and ran sound with many different subs amps, speaker combination. I have learned a lot in the past few years blowing stuff up, trial and error, etc.

 

I will share...

 

I have learned that is it never a good idea to push an amp near limiting/clipping. It sounds worse and could be potentially bad since you could be sending square waves to the speaker, technically doubling the amps rms rating anyway since it is clipping.

 

It is also not good to overpower a speaker or else things get nasty! Believe, me I have blown up a few very nice subs. It was a huge learning experience.

 

 

I would also like to thank Glen (hamonycat) for teaching me a lot of what I know.

 

I have had the best luck getting CLEAN output from an amp without causing ANY damage powering a sub for music playback near the cont rating. Definitely not bridged! Depending on the music, these days, certain songs can have huge peaks that require more power to produce. I was always hitting the limiter with an amp powered at the cont. or below the cont rating based on the subs specs. When I used an amp with a few hundred watts more above the rms rating I, did not clip and got the output I desired. It did not go any louder, I just now had headroom as the amp did not have to work as hard, thus providing better and fuller sound!!!

 

My test sub that I had much experience with was the EV QRX218. I will also say this an amazing sub when powered byt 1600watts. It is a beautiful sound that goes pretty low.

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I have learned that is it never a good idea to push an amp near limiting/clipping. It sounds worse and could be potentially bad since you could be sending square waves to the speaker, technically doubling the amps rms rating anyway since it is clipping.

 

 

Who said to clip the amp? Engage the limiter and that worry goes out the window.

 

Now with the limiter engaged, and at the RMS power level, you are relatively free from mechanical damage (especially if you use the recommended high pass filtering) so all you need to worry about is the thermal rating of the driver which is generally around the RMS value stated. Even with pretty heavy limiting (say 6dB) you should still be reasonably well protected. You will not ever be able to get 2x the RMS power out of the amp with the limiter engaged.

 

You are taking a little bit of knowledge and drawing conclusions that are missing some very important technical facts that you have not considered. This is why I am really recommending powered speakers (which you will find the manufacturers power close to the RMS ratings of the drivers BTW) that contain all the processing and appropriately sized power amps inside, out of the user's view.

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