Help powering my JBL MRX528S Dual 18" Subwoofer

[jaswrx]

Yes... with the limiter engaged it would be protected. I almost always run a limiter. Problem is that the amp with a RMS rating (based on subs spec) is still being pushed to its max and if it is limited, you are not going to get max spl.

 

You still are not getting the full rms rating. What I have found that works best is power a little over and THEN limit it. There is a formula to do this by which you calculate the voltage needed to drive the sub. So you can buy an amp that pushes 2000rms but limit it to 1200. I do this all the time and have great results.

This way you get 1200 of full, clean, unstressed, protected power.

 

There are many threads on thsi on PSW especially when powering the power hungry SRX 728 which I have had a good amount of experience and I can personally tell you it needs the power behind it to shine.

 

btw, I use active speakers now. Yorkville

[DJ eckomike]

Yeah I actually been looking at some crossovers ....... it seems to be everyones advice ...... and I think I have already tried just running it throught one channel on stereo mode ...... and believe me I have been reading the manuals....... I want this baby to work, its just taking up space right now. I will Try it again tho ..... carefully. My main's are self powerd so no issues on that. But will update after I mess around with it a bit.

[agedhorse]

 

Yes... with the limiter engaged it would be protected. I almost always run a limiter. Problem is that the amp with a RMS rating (based on subs spec) is still being pushed to its max and if it is limited, you are not going to get max spl. You still are not getting the full rms rating. What I have found that works best is power a little over and THEN limit it. There is a formula to do this by which you calculate the voltage needed to drive the sub. So you can buy an amp that pushes 2000rms but limit it to 1200. I do this all the time and have great results. This way you get 1200 of full, clean, unstressed, protected power. There are many threads on thsi on PSW especially when powering the power hungry SRX 728 which I have had a good amount of experience and I can personally tell you it needs the power behind it to shine. btw, I use active speakers now. Yorkville

 

 

You most clearly do not understand this topic. This is not how it works, nor does anything you say make sense.

 

I suggest that you take a step back and maybe brush up a little on your learning and book skills before continuing down this path. What you do, what you think you do and what you get away with are all stabs in the dark. This is why most users are better off with powered speakers... let us engineers do the hrad work for you, and do it right. Really right, not kinda, sorts, guess it's ok, yeah I know what I'm doing sort of right.

 

PS... I design amps and speakers and powered speakers for a living and have been doing so for over 25 year. I really do know this subject in excrutiating detail, down to the "2nd decimal place".

[agedhorse]

 

Yeah I actually been looking at some crossovers ....... it seems to be everyones advice ...... and I think I have already tried just running it throught one channel on stereo mode ...... and believe me I have been reading the manuals....... I want this baby to work, its just taking up space right now. I will Try it again tho ..... carefully. My main's are self powerd so no issues on that. But will update after I mess around with it a bit.

 

 

Read the manual very carefully, be sure you understand what all the functions on the amp do and what positions the programming switches need to be in for the correct operating mode. Details are important.

[RoadRanger]

This way you get 1200 of full, clean, unstressed, protected power.

My amp has a switch on it so you can have it stressed on the downbeat for Rock and the upbeat for Reggae and Ska - I think it just flips the polarity ? Oh, and if you're really set on blowing your {censored} up you should stay over on PSW where nobody will dissuade yah .

[jaswrx]

I guess all the guys at psw don't know anything either. I have worked with many sound engineers doing touring acts with Britnry Spears, etc and this is how they set up their amps!

 

I don't see why anybody drives their amps to the max. That is the point I am trying to make. Nothing else. It is best to use a more powerful amp so you have headroom and set the limiter around the Cont. power rating of a sub so it is protected form huge peak spikes in the music and you do not over driver the sub.

 

If you disagree, so be.. but there are plenty of people who do it this way.

[tlbonehead]

I guess all the guys at psw don't know anything either. I have worked with many sound engineers doing touring acts with Britnry Spears, etc and this is how they set up their amps! I don't see why anybody drives their amps to the max. That is the point I am trying to make. Nothing else. It is best to use a more powerful amp so you have headroom and set the limiter around the Cont. power rating of a sub so it is protected form huge peak spikes in the music and you do not over driver the sub. If you disagree, so be.. but there are plenty of people who do it this way.

the ones who have things buttoned down correctly for that cab tend to get away with it. That's far different than less knowledgeable and experienced folks who have the power amp running wild on the speakers, and also tend to have far more oopses. Plus, is that last 2db max really that important if you are taxing the speakers to their limits to get it?

[agedhorse]

 

I guess all the guys at psw don't know anything either. I have worked with many sound engineers doing touring acts with Britnry Spears, etc and this is how they set up their amps! I don't see why anybody drives their amps to the max. That is the point I am trying to make. Nothing else. It is best to use a more powerful amp so you have headroom and set the limiter around the Cont. power rating of a sub so it is protected form huge peak spikes in the music and you do not over driver the sub. If you disagree, so be.. but there are plenty of people who do it this way.

 

 

 

Unless you understand multi-time constant limiters, using a more powerful amp and limiting it down is EXACTLY the same as using a smaller amp with the limiters default at the rated power (as are most). The huge spikes are also limited just as in a bigger amp limited down. No difference whatsoever.

 

Where there is a difference is in some of the details that you do not understand... by designing a limiting algorithem with multiple time constants, you can alter the ratio of short term to long term power relationships, but you better understand the mechanical and thermal models of your speaker if you plan on pushing things very much. This is something well into the professional realm, and the real pros generally have plenty of PA to do the job, compared with the average punter who never really has enough.

 

I make a lot of money from people who overpower their speakers (without proper protection and understaning the limitations)... they typically get away with it for a while until some unfortunate accident or lapse of good judgement. PSW is a great site for the mor professional users but I think they do a general disservice to the lower tier users by recommending things without expanding on some of the important details that typically accompny the pro application of the same use.

 

It's like saying it's cool to hot rod a car, put in a way-big motor but then neglecting some of the important details relating to safety that the pros take for granted... like higher speed rated tires, increaed braking capability, chassis stabilization components, driveline alignments, safety clothing and helmets, special seatbelts, roll cage etc. The details are more important the puting a big motor in the car to go fast.

 

Sure, you may have worked with "big acts" but, and just a hunch, you were not even remotely in the position to really know or even have access regarding what was really going on within the programming (some of the big guys even keep this data private for competative reasons) of their processing. So what position did you hold? A1, A2, SE, BE, ME, TD, PM or a loader on these shows?

[RoadRanger]

I have worked with many sound engineers doing touring acts with Britnry Spears, etc and this is how they set up their amps!

Go for it - too much competition in this biz anyways .

[agedhorse]

And it should also be mentioned that a few of the guys at PSW enjoy giving newbes just enough rope (and encouragement) to hang themselves. I don't care for that approach but I can see where it might be fun with some of the hard-headed newbes actually. Matt V comes to mind as somebody who might have been given a little bit of that treatment actually.

[jaswrx]

Agedhorse-

 

I agree with most of what you are saying. I was not trying to argue. I was stating what I have experienced and have been taught. In conclusion, I have found it is best to have more headroom than not enough power. I also realize what needs to be taken into consideration when powering more than RMS. The potential risk of damaging a speaker is more likely when over powering a speaker for long periods at a time. I know that when I used to power speakers exactly or below the rms rating, I would always be running the amp into its limits and get disappointing results. It wasn't until I was taught that powering a tad over rms would yield better results as the amp would not have to work so hard. Again, it did not really get louder, it just re-leaved stress on the amp thus creating a better sound.

 

In your opinion, what would you power a SRX728 with? Just curious.

[agedhorse]

My point was that taking a large amp and limiting it down is exactly the same as using an amp (with internal limiter) rated at the power you limited the larger amp down to. There is no difference. Remember, I design amps for a living, the very thing you are misunderstanding how it works.

 

Regarding the SRX-700 series, I have found that the point of diminishing returns is 1.5x the continuous rating. Beyond that, power compression eats up almost all of the gains and the risk of long term damage increases exponentially. I also have reconed and serviced JBL products since 1978, so before you tell me how "dumb" I am for "underpowering" them, I can guarantee you that I know more about the most minute details of these drivers than you might imagine. There are other things I would like to share regarding some of these products but I can't due to confidentiality agreements.

[oldschooler]

My point was that taking a large amp and limiting it down is exactly the same as using an amp (with internal limiter) rated at the power you limited the larger amp down to. There is no difference. Remember, I design amps for a living, the very thing you are misunderstanding how it works.

 

So your main point is RMS power is RMS power.

[agedhorse]

So your main point is RMS power is RMS power.

 

Yeah, that's pretty much it.