Driverack PX Limiter

[shawnondrums]

I was using all active speakers at one time and now I'm slowly changing that. I built some T48's and down the road I'm going to be building some BF top boxes. I have a Driverack PX. it's designed for active speaker and I called DBX and they told me it's fine to use it with passive systems too. I'm using it on the T48's. is the limiter in it good enough to use for protecting my T48's. someone told me they don't think it has a brick wall type limiter in it.

[David Carter]

My understanding is that the PX, PA, and PA+ do not have brickwall limiters, and you have to step up to the 260 (or get a Behringer DCX2496) before you get that. Having said that, there are plenty of people here who don't run brickwall limiters. The main question you need to answer is whether anyone else is going to have access to crank things up (intentionally or not) while your gear is running or will you always be at the wheel? If you set up your gain structure properly, and you can guarantee that no unwanted hands will touch the gear, you're probably OK.

[Landl.livesound]

My understanding is that the PX, PA, and PA+ do not have brickwall limiters, and you have to step up to the 260 (or get a Behringer DCX2496) before you get that. Having said that, there are plenty of people here who don't run brickwall limiters. The main question you need to answer is whether anyone else is going to have access to crank things up (intentionally or not) while your gear is running or will you always be at the wheel? If you set up your gain structure properly, and you can guarantee that no unwanted hands will touch the gear, you're probably OK.

And actually it is a good thing to not have/use brickwall limiters since unless your amp is rated much past the mechanical limits of the driver. (Which most on here don't.)

Most would actually benefit much more with a limiter with very slow attack and release times over seconds, not mS, which is much harder to find. (Unless you use an iTech amp and then it is built in.)


The big thing is depending on the type of music to use an amp that is 1-2x the thermal rating. If you are doing Dubstep or other types of music with very low crest factor on the low end an amp rated closer to the thermal/continuous/RMS rating of the driver is much safer. But if using it for more top 40 type music and live bands, closer to 1.5-2x the thermal rating of the driver is just perfect. And then just watch your clips lights and if you don't let it do more than flash for a split second on peaks you should have no problem with a well designed driver.


Take Care!
Phil

[shawnondrums]

Thanx David. I did a little digging and found the DriveRack PX does not have a brick wall type limiter. But I do have a MDX2600 Behringer compressor/limiter with a Peak limiter laying around. I'm thinking I could put it after the sub outs on the driverack. Because I don't have the money right now to replace it with a DR260 and I use the crap out of the RTA auto EQ on the PX. I have all my club EQ settings programed in it. Makes my set up extremely fast. all it lacks is a good limiter. bummer. do you think this will work for now.

[Landl.livesound]

Thanx David. I did a little digging and found the DriveRack PX does not have a brick wall type limiter. But I do have a MDX2600 Behringer compressor/limiter with a Peak limiter laying around. I'm thinking I could put it after the sub outs on the driverack. Because I don't have the money right now to replace it with a DR260 and I use the crap out of the RTA auto EQ on the PX. I have all my club EQ settings programed in it. Makes my set up extremely fast. all it lacks is a good limiter. bummer. do you think this will work for now.

As long as your amp isn't super large for the T48 you should be good just know that when the clip light starts to flash you are out of rig. I'd say get that limiter out of the way since most of the cheaper ones don't sound that good anyway.

Take Care!

[BrentEvans]

And then just watch your clips lights and if you don't let it do more than flash for a split second on peaks you should have no problem with a well designed driver

Two problems with this. First, the word "should" does not enter into engineering. Second, how do you watch your clip lights if they're at the amp, and you're at FOH. Remote camera? Don't think so. Brickwall limiters are there not to be hit, but to protect. Further, running an amp with about double the thermal rating with a properly configured brickwall will protect the driver and allow the amp to run cool and in low distortion.

"You should always match your speakers and amp" is what they taught us in training at RadioShack (even though we never had speakers and amps with matched ratings ). It's what they teach the Guitard Center and Sam Rash people too. It's bad advice based on what looks right, kind of like trap arrays.

[shawnondrums]

I am using 3015LF drivers in 2-T48's with a PLX 3602 and I want to limit it to 50 v. as in the plans to protect my investment (Drivers). Live band with no sound man. been doing it for years and haven't smoked anything yet. and don't want too. LOL this is the first time I've run Horn subs and I don't have a feel for what they can handle yet. and you can't hear them peak.

[shawnondrums]

I'm assuming the limiter in the MDX2600 Behringer is basicly the same as the one in the DCX2496. everyone seems to like that one. unless I'm wrong.

[Landl.livesound]

I am using 3015LF drivers in 2-T48's with a PLX 3602 and I want to limit it to 50 v. as in the plans to protect my investment (Drivers). Live band with no sound man. been doing it for years and haven't smoked anything yet. and don't want too. LOL this is the first time I've run Horn subs and I don't have a feel for what they can handle yet. and you can't hear them peak.

Oh ya, Shawn, you are fine, IIRC the T48 is 10 ohms nominal which would mean the PLX3602 would be capable of up to about 600 watts. The 3015LF is rated for 450 continuous and 900 program. So even if you are running very low crest factor, low end, music with a worst case 3dB crest factor. That means that when the amp just starts to clip on peaks the average power the driver will be receiving will be around 300 watts, which is a decent amount under the thermal rating of 450 watts.

And actually usually a worst case scenario is closer to 6dB crest factor, so when your amp starts to just clip on peaks the driver will only be receiving about 150 watts average which is a decent amount under the 450 thermal rating as well.


I just realized you are a live band, when I run sound for my bands I usually run with a crest factor of about 10dB on the low end. Meaning when I would clip your PLX3602 it would only be putting out an average of about 60 watts to the T48's.


So what will happen if you really "peak" limit your T48 is that it will start to compress those 6-10dB peaks very quick and your dynamic punch will start to be lost as it compresses the dynamics. Plus that will raise the average level going to your drivers making them heat up even more and get closer to burning out the VC.


So I would say you could conclude that you will be just fine as long as you don't let the amp get into hard clipping, as there is no "for sure" limiter and they can many times make things worse.

Also if you are worried, the 3015LF is not too expensive to buy a backup driver or 2 if you are really worried.

Take Care!
Phil

P.S. Just make sure you employ the correct HPF that your Driverack should be capable of.

[Landl.livesound]

And then just watch your clips lights and if you don't let it do more than flash for a split second on peaks you should have no problem with a well designed driver

Two problems with this. First, the word "should" does not enter into engineering.

Hey Brent,

The reason I used "should" is because it is almost impossible to guarantee that you will never destroy a driver. There is always the chance you will get a nice long blast of LF feedback that last for several seconds that will take out a driver, but as long as you have some crest factor you are fine.

Just realize that for you to make it *almost* entirely foolproof is to set a limiter for less than 1/2 the thermal value of your driver which can cut down a lot on performance.

Second, how do you watch your clip lights if they're at the amp, and you're at FOH. Remote camera? Don't think so.

2 Things:

-Have enough rig for the gig so you don't have to worry about even getting close to the limits of your rig
-The best thing is to know the limits of your rig, and if you use it enough you will know when you are running out of gas without seeing the clip lights.

I would never expect everyone to be able to position there amp rack so they can see it from FOH, but surprisingly I always seem to be able to position the Amp rack where I can see it from FOH.

Brickwall limiters are there not to be hit, but to protect. Further, running an amp with about double the thermal rating with a properly configured brickwall will protect the driver and allow the amp to run cool and in low distortion.

If I was using a brickwall limiter I would put it somewhere way out of the way (At least 2x-3x the continuous rating of the driver since that is where a good driver can get close to taking mechanical damage on peaks. And why it is called a peak limiter to protect from large peaks, not from continuous power heating up and burning up the VC.) And since most people won't use an amp larger than 2x the continuous rating of the amp you will be into super hard clipping in the amp before the limiter even kicks on.


Much of this comes from just my basic trying them on systems. For example, the PL380 I use on subs puts out up to 1500 watts. The driver it is powering has no problem taking much more than 1500 watt kick hits. The crest factor on my low end stays around 10dB. So when that PL380 starts to clip the average power is in the 150-250 watt range which is way under the continuous rating of the driver, so I am in no way close to burning out the VC. (Even if the crest factor goes down to 6dB the driver will only get around 400 watts which is still much less than the continuous rating.

I have tried out basic peak limiters just to see what they do, like the ones included on the DCX2496, BBE DS24, DR PA and they just sound really bad when you when even not that far into them. So I just said to get the darn things out of the way.




*Now, what I wouldn't mind employing is a limiter with a very slow attack and release, like the thermal limiters in the iTech amps. I considered switching my rack from QSC to iTech just for this reason but decided against it so far. Maybe when the iTech HD's start hitting the used market for cheaper like the last iTech's are now doing.

Actually for protection I would much rather take a limiter like the one I described above since the amps most of us are using won't get close to the mechanical limits of the drivers. What I would want it to do would be to protect against the random long feedback, or LF keyboard/synth lines. Something like if X voltage is crossed for more than 3 seconds it will turn it down X dB/second. This then will let the peaks go through so as not to take away from the dynamics and lower the crest factor at the same time.


Hope this makes some sense. Again nothing is foolproof, unless you take away a good amount of performance from the cabinet. But again the biggest protection is enough rig for the gig.


And don't worry this isn't some Banjo Center voodoo magic matching amps to speakers stuff. This is about that the music we put through is usually not sine waves.




Take Care!
Phil

[BrentEvans]

The reason I used "should" is because it is almost impossible to guarantee that you will never destroy a driver. There is always the chance you will get a nice long blast of LF feedback that last for several seconds that will take out a driver, but as long as you have some crest factor you are fine.

Not if the voltage limiter is set up properly to ensure that that much voltage never reaches the driver. Voltage is an absolute. If you limit to X Volts, and you're well into your limiter trying to get more volume, you don't have enough rig.

Just realize that for you to make it *almost* entirely foolproof is to set a limiter for less than 1/2 the thermal value of your driver which can cut down a lot on performance.

Yup. That's when you add cabs.

-Have enough rig for the gig so you don't have to worry about even getting close to the limits of your rig
-The best thing is to know the limits of your rig, and if you use it enough you will know when you are running out of gas without seeing the clip lights.

Horns don't sound like they're running out of gas.

I would never expect everyone to be able to position there amp rack so they can see it from FOH, but surprisingly I always seem to be able to position the Amp rack where I can see it from FOH.

Clipping amps sound bad, and near-clipping amps sound bad. In portable land sometimes you can position an amp rack so you can see it, but that's an almost-never in install land, and sometimes you're too far away to be able to see it anyway.

If I was using a brickwall limiter I would put it somewhere way out of the way (At least 2x-3x the continuous rating of the driver.) And since most people won't use an amp larger than 2x the continuous rating of the amp you will be into super hard clipping in the amp before the limiter even kicks on.

And that would be the wrong way to deploy a brickwall limiter. Again, these limiters are there to protect the drivers, and they're not supposed to sound good. If you're hitting the limiter, you need to turn down, or add cabs.

Much of this comes from just my basic trying them on systems.

Learning the math goes a long way. Reading is beneficial too.

For example, the PL380 I use on subs puts out up to 1500 watts. The driver it is powering has no problem taking much more than 1500 watt kick hits. The crest factor on my low end stays around 10dB. So when that PL380 starts to clip the average power is in the 150-250 watt range which is way under the continuous rating of the driver, so I am in no way close to burning out the VC. (Even if the crest factor goes down to 6dB the driver will only get around 400 watts which is still much less than the continuous rating.

If your nice 1500 watt amp hits 1500 watts, then you're in distortion territory, not to mention way into the power compression range of the driver. Bad news all the way around. Again, bigger amps also help with heat, longevity, and distortion. Clipping an amp may not damage a speaker, but it sure doesn't sound any better than going into a limiter, and then you're in an uncontrolled environment. The system will sound better overall with an amp that is not clipping, or anywhere close to it.

I have tried out basic peak limiters just to see what they do, like the ones included on the DCX2496, BBE DS24, DR PA and they just sound really bad when you when even not that far into them. So I just said to get the darn things out of the way.

3rd time, limiters aren't to be hit, they're to be protection. If you're hitting the limiter, not enough rig.

*Now, what I wouldn't mind employing is a limiter with a very slow attack and release, like the thermal limiters in the iTech amps. I considered switching my rack from QSC to iTech just for this reason but decided against it so far. Maybe when the iTech HD's start hitting the used market for cheaper like the last iTech's are now doing.

Actually for protection I would much rather take a limiter like the one I described above since the amps most of us are using won't get close to the mechanical limits of the drivers. What I would want it to do would be to protect against the random long feedback, or LF keyboard/synth lines. Something like if X voltage is crossed for more than 3 seconds it will turn it down X dB/second. This then will let the peaks go through so as not to take away from the dynamics and lower the crest factor at the same time.

Not necessary if the system is deployed properly. Nifty, but not necessary. A far better way is to mix with tasteful compression and deploy the rig with proper lmiting. The compression will control the dynamics in a way that doesn't sound like the whole system getting turned down, and the overall mix comes together better. I'm spoiled with SAC though, because its compressors are completely transparent, as is the Levelizer plug, which allows for brickwall limiting without flat-topping the signal. I have a feed going into a nursery that smashes against a brick wall about 95% of the time to keep the volume very stable (sleeping babies and all) and it's perfectly listenable. You'd never know it was hitting a brickwall except for the fact that the volume is very constant.

Hope this makes some sense. Again nothing is foolproof, unless you take away a good amount of performance from the cabinet. But again the biggest protection is enough rig for the gig.

Not really. Do you redline your car? Most people don't. This is Tim Allen syndrome - more power does not fix problems. Doubling cab count is far more effective than doubling power.

Having enough rig is not protection, it's smart business sense. Knowing what gigs to take and not to take based on your rig is smart business sense. Knowing when to stop (turn down) is also smart business sense, as your investment is protected and so is your paycheck, and your customer base.

And don't worry this isn't some Banjo Center voodoo magic matching amps to speakers stuff. This is about that the music we put through is usually not sine waves.

Sine waves are horrible on the ears, great for calibration. If one is to get the most out of a system, one had better be calibrating that system with math and science, not "This amp is this much and this driver can handle about this much so we'll probably be OK." At that point, you are relying on marketing specs and figurin'. That's just as much voodoo as the knowledge cheerfully dispensed by the salesman at *pick your music emporium*. I'll take my multimeter and calculator any day of the week.

[Landl.livesound]

Hey Brent,

I say we agree to disagree on this topic. As of right now, I have no use for peak limiters with super quick attacks and releases as they will only be a detriment to my system.



*Re: Power compression and 1500 watt amp* From my understanding power compression is caused by heating power, which is the average power in the signal you are sending to your drivers. Now when I am using that 1500 watt amp with 10dB crest factor that means that the average power is less than 200 watts. The driver that I am sending this power to has a power compression rating of -3.2dB at 800 watts continuous. So I don't think I would yet be getting into much power compression with only 200 watts of heating power. If I was only using an amp capable of say 750 watts, when the amp started to clip and chop off the peaks the amp would only be putting out about 75 watts average. And I would be loosing a good amount of of output since the 1500 watt amp isn't close to burning out the VC.


I am also all for efficient speakers, but I am also all for them being accurate to their cut-off point and sounding good, and the couple horns I am looking at that meet those requirements are out of my budget as of right now. (The subs I use now are both around 100dB 1W/1M so its not like they are super inefficient, but they are flat, accurate and sound good. I would like a couple larger horn subs with 103dB+ 1W/1M that go flat to 35hz, but that's for when the business is expanding any I need larger subs like that.)


I totally agree that red-lining all the time is not the way to go. I will thankfully say I still have plenty of headroom in the driver even with the 1500 watt amp so I haven't been worried.

I would have to say I would rather do the smart business thing as you say and bring enough rig for the gig. To be honest with you, it's not like I an looking forward to burning up some drivers, but I know one can learn a good amount in the process of doing that.


I say let's agree to disagree,

Take Care!
Phil


P.S. Here is a pretty good article: http://campuspa.com/downloads/Loudspeak ... entals.pdf

[BrentEvans]

Phil, you can run your system however you want, but you need to realize that horns play by different rules than you're used to. Running horn subs without voltage limiting is not smart, period. You can't hear the telltale distortion telling you to turn down, so you simply have to do the math and science with a limiter or run amps that aren't capable of cooking the driver (which isn't desirable). Tops arent such a big deal, because the distortion is audible.

Further, it's smart to run anything the way its designer intends. Bill specifies voltage limits in the plans, and reccomends a brickwall limiter. That is what most people should do.

[Landl.livesound]

Phil, you can run your system however you want, but you need to realize that horns play by different rules than you're used to. Running horn subs without voltage limiting is not smart, period. You can't hear the telltale distortion telling you to turn down, so you simply have to do the math and science with a limiter or run amps that aren't capable of cooking the driver (which isn't smart). Tops arent such a big deal, because the distortion is audible.

Further, it's smart to run anything the way its designer intends. Bill specifies voltage limits in the plans, and reccomends a brickwall limiter. That is what most people should do.

Hey Brent,

I do run horns without any limiting without any problems. I power them with up to 1000 watts available without a problem.


And you are correct, it isn't as obvious that the horn is reaching its limits but there are some tell-tale signs that I have noticed with different horns when they are reaching their limits.


The thing I am curious is if you have ever done some testing to see how much it actually takes to blow the drivers in your horn subs? That is always a good learning experience. I am not going to tell you to destroy some $100 drivers but much can be learned.

If you have already blown a bunch of drivers in your subs then I can see why you are paranoid, but then we would have to see what is actually causing you to blow all these drivers?


The thing that makes it hard is that music is very dynamic and you can't use even most good, expensive volt meters to get good readings of the voltage with music. You must use sine waves which is not what music is. Which makes it not a "perfect" science to setting limiters.



Take Care!
Phil

[jcmbowman]

Also if you are worried, the 3015LF is not too expensive to buy a backup driver or 2 if you are really worried.

For the same amount of money you'd spend on a spare 3015LF or two you could buy a DCX2496. And with the DCX set up properly with your amplifiers, you won't ever -need- the spare 3015LF.


For the record, I haven't blown a driver since 1997, and I regularly find myself in scenarios where a pop, click, or dumb@$$ lights up the levels on my board full out. Yes, it's possible to run a system without a limiter and never blow a driver, and it's also possible to drive a car without wearing a seat belt and never get thrown through the windshield. It doesn't mean that it's a good idea, especially for people who are just starting to get their feet wet in the business.

And Phil - while it's nice in a philosophical debate to agree to disagree, the primary purpose of this forum is not for philosophical debates. It's a product support forum for Bill's speaker designs. When Bill himself has repeatedly suggested that best practices with his speaker designs involve measuring the voltage to set a limiter properly, and basing the voltage calculation on a value well below the stated RMS rating of the drivers, it smacks of disrespect to continue to argue the counterpoint to that. Just sayin'