Question about how many power circuits we should be using (and addition of new cabs)

[Craig Vecchione]

 

Well, the OP states he has some 540 shows on those subs while running them hard with no failures. At a typical 4 hours per show, that would be over 2000 hours on the subs with no failures. Based on the above, they should have failed mechanically long ago, but they haven't. The OP has had several sound company operators look at his system and states no one has had a problem with the setup. Based on that and the long performance without failures, I would assume it's well set up. Powering speakers with the 'program' power rating rather than the 'continuous' is not uncommon, and properly set up, does not necessarily mean a drastically shorter life. Many people have good results either way.

 

 

This sounds a lot like a guy who used to post here, and was driving another brand of speakers in the same range as these SRX...at program power. He had several years of shows under his belt with them, and couldn't be told anything. He was "right" because his rig sounded great, and we were "wrong" because it hadn't failed.

 

It wasn't long after he left this forum for a "more professional forum" that he posted there asking why both of his subs failed catastrophically during a show. The consensus of the "more professional" guys over there....too much power.

[Jealousblues]

 

I'm in the wedding band circut, I run sound for a lot of different bands at weddings both outdoor and indoor. My main system is JBL MS105 (reloaded with better guts and biamped) and SP128s (2x JBL 2242's). Never, and I mean never have I needed double stacks for anything under 400 or so. I keep the SPL around less than 100dB on the dance floor, people at weddings want to talk etc and enjoy time with thier family. All these are being driven with less than 1100w per box. I will run double stacks for very large corporate and outdoor festival type settings but really it's not that often. I had a pair of 728's for a while, I really liked them, sold them because they didn't integrate with my line up of subs. But at 1100w each they were great boxes, very deep sounding and work well in multiples. I guess I can't see dragging 4 out for a lot of gigs. 15 a month is every other day, that's a lot of gigs, it's a good reason to be scaleable too. Match your top boxes and center cluster the subs when you need more out of the rig, you'll be suprised.

 

 

yeah, Im not sure we would bring 4 cabs to each show. Certainly not all would need them or would they all realistically fit them.

But it would be nice to have the option.

 

what do you mean by match your top boxes?

 

Id love to be able to put the subs in the middle, but at weddings thats really not much of an option as they take up a LOT of space and our tops we use dont go on poles so we stand the subs up and stack them on top (the smaller tops do go on poles but we prefer the others for most gigs)

 

Ive emailed JBL as well for some advice but havent heard anything back yet (its only been a day)

so we shall see how we procede

[minn12]

This sounds a lot like a guy who used to post here, and was driving another brand of speakers in the same range as these SRX...at program power. He had several years of shows under his belt with them, and couldn't be told anything. He was "right" because his rig sounded great, and we were "wrong" because it hadn't failed. It wasn't long after he left this forum for a "more professional forum" that he posted there asking why both of his subs failed catastrophically during a show. The consensus of the "more professional" guys over there....too much power.

 

Nope, not me, if that's what you were suggesting. And of course, your anecdote doesn't prove anything, since there are no specific facts as to what happened. I simply pointed out the OP's own experience did not correspond with another poster's claims of limited speaker life at higher power levels. The OP is free to look at the contrasting opinions, and along with the input from the other sound company operators he had look at his system, make up his own mind.

 

I now see the OP has emailed JBL. I would guess if JBL says he's fine running those amps, we'll see even more posts claiming how wrong JBL is.

[agedhorse]

Harman owns both JBL and Crown. There's a lot more profit on selling large amps regardless of the outcome.

 

If you look at how their engineers actually power the self powered versions of speakers with the same drivers, you will find that they powewr them at betwen the RMS and 1.5x the RMS rating of the speaker AND that's with proper protective processing. It's the classic case of do as they do not as they say. Why you might ask? Because as soon as you marry a speaker to an amp, you are wed to the whole package and the manufacturer finds that it's more difficult to distance yourself from claims of defective speakers that were in fact overpowered. The costs would be staggering.

[Jealousblues]

Nope, not me, if that's what you were suggesting. And of course, your anecdote doesn't prove anything, since there are no specific facts as to what happened. I simply pointed out the OP's own experience did not correspond with another poster's claims of limited speaker life at higher power levels. The OP is free to look at the contrasting opinions, and along with the input from the other sound company operators he had look at his system, make up his own mind. I now see the OP has emailed JBL. I would guess if JBL says he's fine running those amps, we'll see even more posts claiming how wrong JBL is.

 

that is if JBL emails me back ;-)

[Pro Sound Guy]

 

Hey guys just want to give a big thank you for all the help so far with my other threads. Ok, heres our situation nothing huge but Im wondering about power. We do lots of weddings and private shows with our own PA and lots of outdoor gigs where we really could use a little more PA right now we have two JBL SRX 728 subs (passive double 18's) and two JBL PRX two way tops with the two 15" speakers and sometimes we use the PRX single 12" as well for sound out to our side at weddings or a little extra at outdoor gigs. two crown XTI 4000 amps to power the subs. We are thinking about picking up two more of the double 18"s if we can find them. We currently run 2 keys, a pod (guitar effects), VDrums, and our presonus mixer and amp rack and LED lighting (we do have 2 moving lights and 2 scanners that are not LED however, dont know how much power that takes. I know the LEDs are much less)...so I dont think any of that other than the speakers are huge power draws? Right now we use 2 20 amp circuits to power that. One of the subs and one for everything else. IF we can get three we will use that as well. We almost never have any issues unless the place is really old or has really crappy power. I assume thats the correct way to run that? Anyway I was wondering if we got the new subs (and maybe two more tops in the future) if we are going to run into any power troubles and if so how many circuits should we be using and how would you run it? (say two sub amps on one circuit and two more on the other and the rest on the third ect..) I just dont want to buy more speakers and then find out we cant really even use them or start blowing power. thanks guys, I really do appreciate your knowledge and how much you have helped me over the years.

Two things to point out. You are running bridged amps @3200w per amp into clipping? NOT a good idea at all. Also, High pass filter?

Did I miss you saying you had one? If NOT then you need to engage high pass

and I dont know what JBL recommends for a high pass but get that in line right away!

As others have posted here you are much better off to have more subs instead

of driving your subs at XMAX or beyond all the time. In fact by driving more subs and

at half the cone excursion your loudspeakers will last longer and it will sound better.

Also, as others have stated you get whats called power compression. The voice

coils heat up and resistance increases, and it takes more power to drive

the loudspeaker then when the voice coil is cool. This means that by having

more subs reducing cone excursion and keeping your voice coils cooler you

will have better performance. For gosh sakes man dont be driving a bridged

amp to clipping!

[Jealousblues]

NO idea about a high pass filter (again, I dont run and didnt set up the system myself)

Is that something that is on the crossover or is it its own piece of equipment?

 

Part of me wonders, since there are digital amps if there is something that is tweaked on them or a setting to protect the subs?

 

Ill take pictures tonight of the amps (we only use one tonight as we only use half of our PA at this smaller club) as well as the crossover if I can think of it.

[Jealousblues]

Http://m.flickr.com/lightbox?id=7423506246

 

 

http://m.flickr.com/lightbox?id=7423519318

[agedhorse]

Photos don't show up.

[Jealousblues]

Darn it

Tried from my phone at gig last night

 

Will try to get them up this weekend

Going to set up at komen race this morning then wedding afternoon-tonight

Then baby shower tomorrow

Busy busy

[RoadRanger]

 

That's just soooo wrong .

[Unalaska]

Uh, I see 2 things: there is a BBE processor. 2nd is the crossover point for ch2 is at... 40hz maybe? Can't tell but that low/high knob oughtta be around 100. Turn that little knob and I think you'll hear those subs. And turn the high output up closer to 0.

[tolstoy]

Is that a picture of the poster's crossover setup? If it is, than yeah.......you need to raise the crossover point up to around 100hz, but before you do take the low gain down to 0. I just hope that someone bumped the rack with thier leg and that isn't where it's actually been set. My guess is at that point you'd be happy with the sub output. That is if this is truly how this system has been being run (I find that hard to believe because I don't see how that would sound like anything at all".

[agedhorse]

Before anybody should be aloowe to bridge an amp, they should be required to understand how their simplest of simple crossover works. Ugh.

 

(Perfect example of how things get "blowed up", makes me a lot of money in my shop as I do a lot of recones that never should have happened.)

[Jealousblues]

It doesn't sound like waaaaaaaaaaay out of wack like you would have me believe ("doesn't sound like anything at all") to my ears anyway.

I know that probably sounds completely ridiculous to you right now

 

 

Here's the thing, if its working right right now for whatever reason...and I move the crossover point to what you say will it be "too much" for the subs?

Do you think its set that way to compensate for the bridge subs for whatever weird reason?

 

Judging from that crossover setting visually what would you expect the system to sound like?

(All miss, way too boomy, zero low end, no highs...???)

 

Thanks again guys

I know this system isnt sounding awful right now, its not an offensive mix or anything if that makes sense

But I bet it soils sound better

[Jealousblues]

 

 

heres our system (all the settings SHOULD be the same as what you see)

it just recorded from wedding video cam so I dont know if the audio quality if great or anything.

 

honestly I appreciate you guys helping straighten this out.

 

I just wish one of you guys were local or something

 

I wish I could get you guys some more video of it but all I would have is crappy cell phone video that would distort and not get how it actually sounds fully

 

 

***edit***

thats our old mix wizard board and we had an ashley EQ that we dont use anymore in this video.

Now we have a presonus board and we use the eq in it. I do not believe that sound is that much different from the recording however.

 

Thanks

[Jealousblues]

and heres the thing...I dont know if the guy who set it up did so in relation to the maximizer (and of course im no expert when it comes to all the stuff so I have no idea what IM saying and telling you guys too :-()

 

but maybe he had the maximizer all jacked up one way before the cross over and used the crossover to "tame" that or compensate or something weird?

 

Again I have no idea just throwing this out there

[Jealousblues]

One more thing

Are we red lining sometimes on the sub amps because that crossover setting is strangling the low end some?

[agedhorse]

 

One more thing Are we red lining sometimes on the sub amps because that crossover setting is wriggling the low end some?

 

 

Possibly, if the sub passband gain is too high because the subs are not capable of reproducing much below 40Hz anyway. I am also suspect of the lack of suitable high pass filtering under these conditions if the passband gain is way too high. 40Hz as a crossover point is just plain wrong, I can't think of a single case where it would not be horrible.

 

The BBE device may also be adding a lot of sub passband gain as well.

 

I wish I knew a system tech I could trust in your area, that would be too easy.

[Jealousblues]

It's just annoying because I can educate myself but I won't know half as much as some of you guys have forgot you know?

And you pay people to set this stuff up...and if its {censored}ty and damaging stuff its really annoying.

 

 

So here's my questions

Our settings are wrong but I don't understand why

Can you please tell me what's wrong with our crossover settings (how it sounds) and how it will sound with the correct settings and why so I can relate that to the band

[Unalaska]

My guess is the subs are operating between 20 and 40hz the severe boost coming from both the bbe and the +6 low out (and -10db high out). What youre mostly hearing are the tops only with a very small amout of sub info.

 

I like the subs to be about 6db louder than the tops, others have different views but that's me. Raising the high out to 0 and lowering the low out to 0 would be where I'd start. Right off the bat you're going to have to turndown the master volume, suddenly the rig will be effectively 10db louder.

 

Next advice would be to take the sub amp out of bridge mode and use in stereo, raise the crossover low out to +6db after you've done this. Before the next gig spend sometime and listen to the new balance of sub and top, it should be pretty usable too, I doubt you'll think about adding subs after this.

[agedhorse]

Are you willing to go through the set-up step by step? Do you have any help that is willing to follow directions and learn?

 

I am willing to walk you through it in a way that I know will deliver what the JBL engineers intended, but you will have to be willing to learn as you go. It's a great learning opportunity for others here (lurkers as well as active participants) and I have done this a few times before with good results.

 

Note that I do the design side of this for a living, I write presets and know your speaker system intimately. If you are willing to learn the DSP on your amps, that's one option but generally I find using a single DriveRack PA processor a less painful experience overall.

 

Do you have access to somebody who can make good quality XLR cables locally? Mark at Audiopile has everything you need on his website but that may take longer to complete the job. By the time you are done, you will know a lot more about how this stuff works. You already have enough of the expensive stuff, it's a shame that you aren't getting the results that you should.

[tolstoy]

Start with the basics........

 

The purpose of the crossover is to divide the frequencies and send them out to the speakers that are designed to faithfully create those frequencies. Lows go to the subs, everything else goes to the tops in a 2-way system. This is how you're set up is being run........lows go out from the low out on the crossover to the sub amps that then amplify the signal being sent to them from crossover and sends it to the subs. You can set where the frequency is divided. Most sub systems cannot reproduce much under 40hz......yours included, and most top speakers really shouldn't be producing much below 100hz.....yours included. From what we can tell in that picture, your crossover is set to send only the frequencies below 40hz to the sub amps(actually I don't remember what the lowest freq setting is on that crossover, but it looks like it may more like 20hz)! Now that means that your top speakers are still tring to reproduce everything all the way down to 40hz (Not what the should be doing with the pressence of subs). Your subs are mainly tring to reproduce frequencies that they really can't reproduce at any kind of level that you can actually hear.

 

I think you may believe that it sounds ok (and it probably does since you actually have pretty decent tops) but you are not experienceing the sub system at all. The other thing about you're crossover is that the 40hz cut is engaged and the crossover point is set below 40hz. The cut is there to drop freq below 40hz that most sub systems have a hard time reproducing as a form of protection, and to free up that amplifier power to reproduce the frequencies that the subs can actually reproduce. Basically, your subs setup this way wouldn't reproduce much that you could hear at all...........and it wouldn't matter if you sent it 1watt or 3600watts......you still won't hear it. You might as well just leave them in the truck. Which is probably why the low out control is maxed out........in an attempt to hear what you'd expect from a sub system but arn't because of where the crossover freq is set.

 

Your subs inability to reproduce the frequencies your feeding them is probably what led to cranking the low out gain on the crossover, and why someone decided to add that god awful bbe thing above it.

[Tomm Williams]

 

Are you willing to go through the set-up step by step? Do you have any help that is willing to follow directions and learn? I am willing to walk you through it in a way that I know will deliver what the JBL engineers intended, but you will have to be willing to learn as you go. It's a great learning opportunity for others here (lurkers as well as active participants) and I have done this a few times before with good results. Note that I do the design side of this for a living, I write presets and know your speaker system intimately. If you are willing to learn the DSP on your amps, that's one option but generally I find using a single DriveRack PA processor a less painful experience overall. Do you have access to somebody who can make good quality XLR cables locally? Mark at Audiopile has everything you need on his website but that may take longer to complete the job. By the time you are done, you will know a lot more about how this stuff works. You already have enough of the expensive stuff, it's a shame that you aren't getting the results that you should.

 

 

OP---------you would be insane to pass on this.

[Unalaska]

I'd say take Andy up on the walk thru, this isn't rocket surgery and no one will die in the process. Thanx andy!