Doing without limiting, what's the dealio?

[Gregory East]

Before I knew what highpassing subs meant I bought a Behringer cx3400 crossover which was going to be used for biamping my bass rig. Long story short, now putting together the budget mono BFM PA system from hell. Left channel of mixer will feed monitor and right channel FOH.

Can I "chain" the channels of the crossover so the 1st one cuts lows and feeds +45Hz on to the 2nd channel crossing 100hz? Or will that cause buzzing/smoke?

2nd question is about limiting. No limter aside from the "broadband" one in the cx3400. I'm not too concerned about blowing things up as I will be the only one operating it but what overloading situations should I be concerned about in a live band with electonic drums?

My amps are old school 300W RMS /ch and 200W RMS /channel. I figure pair of BP102 T39 on one channel of the "big" amp ought be safe enough and the two J10 on the other will about keep up. The 200W one will not be working hard for the monitors.

[Greg Plouvier]

You could do that - patching out of the high output of the 1st channel crossed at 45 into the input of ch2. Might be kind of inaccurate - trying to land right on 45 Hz. I wouldn't sweat the limiter for now - just keep the amps out of constant clipping. If the clip light lights occasionally on the sub channel not a big deal. Probably should figure on a stereo eq too. One ch for main, 1 for mon.

[Gregory East]

It has 4 detent clicks to get from 44hz to 60Hz. I figure on sending it 45 Hz and seeing what comes out on the 2nd click. Hopefully not much.

So long as I'm not going to create a groundloop from hell I'm good to go.

What's the worst that can happen to accidentally overload the system? Dropped microphone or someone unplugging a gat while live is all I can think of. Is such a spike lethal to Bp102?

Reading about the feeding back mic into wedgehorn I'm not too concerned about the tweeters getting screached once in a blue moon. My mics stay on stands.

[Gregory East]

Lots being witten about limiting lately. How does one accidentally overdrive a live band PA with no peak limiter in place?

[Ron K]

Lots being witten about limiting lately. How does one accidentally overdrive a live band PA with no peak limiter in place?

By turning it up too loud!

All sarcasm aside just use your ears.

If you happen to be wireless on stage simply wonder out front and listen to the mix.If not get a long ass cord!If you're a drummer then have someone whos ears you trust do it but be prepared for their subjective opinion. It's either gonna be ok or it isnt.

Too many times and with too many people both live and DJ think it's always about volume.

Yes we all like chest thumpin lows and crispy highs and vocals that cut through the mix.But no one likes things unintelligible and garbled mess! If the rig isn't up to the task you will most likely get an unintelligible garbled mess no matter how hard you try to get something useful. All to often the band is just too freekin loud on stage and all bets are off! Just playing a CD through the system isn't going to tell you much as far as how the bands going to sound.

Mix it, blend it to taste, keep the levels out of distortion and all should go well and your drivers should live to see another job. At any point in the chain you begin to push things out of whack then expect to reap some negative results. Depending on what point in the system you mess things up will largely determine whether or not you will replace a driver, amp or board!

It sounds sort of simple and if you really take the time to set all biases aside and listen intently to what you are doing then you should have no problems.

All the crap about limiters or not can be argued till the cows come home! Some protection is better then none. All can be overridden and produce disastrous results. There is no substitute for knowing what the hell you are doing!

I'm not going to get into the limiter argument. Only you know which protection scheme will work best for you. If you have little to no experience then I'd just use the recommended methods and ignore some of the alternate suggestions until you have a very firm grasp of what you are doing less thee be willing to part with some hard earned booty!

Good luck and just keep things out of the red!

Ohhh regarding the E Drums for live use. Do beware that they generally have tons of HF information on a lot of samples to produce the stick strike sounds and can actually be pretty hard on compression drivers if you are using them.Be prepared to listen carefully before crank them up. Live situation HF can get pretty dam loud and actually hurt your hearing!

[Greg Plouvier]

"By turning it up too loud!"
Haha - yeah I agree Ron. But would that really be an accident? Hmmm
What style of music are you putting thru this pa ? Something else that can "accidently" overdrive a pa is trying to eq in too much low end - say in the kick drum - or over eq anything really. This goes along with what Ron said about the rig being up to the task. Keep it within its capabilities.

[Gregory East]

I'm with stupid but I'm not stupid myself, ok. I know how to set a mix that doesn't clip the mixer.

So the only threat is stupid going apeshit on toms and kick for a couple of minutes to give an average signal that's more powerful than the 80Hz sin test, yet stays out of clipping?

[Ron K]

I'm with stupid but I'm not stupid myself, ok. I know how to set a mix that doesn't clip the mixer.

So the only threat is stupid going apeshit on toms and kick for a couple of minutes to give an average signal that's more powerful than the 80Hz sin test, yet stays out of clipping?

If the drummer has problems with controlling his dynamics, then with open mics the best approach is to not close mic if you can get away with it and maybe just use an overhead and a kick mic. I've done the OH/Kick mic and have had pretty good results with it.If you'd like I can send you a tune or two recorded live off the board in exactly this fashion.It works quite well. Again key is keeping the mix clean and if the drummer has dynamics control problems short of strapping a comp on the drum mix I'd experiment with different micing techniques.

[Gregory East]

Electric drums.

Someone correct me if I'm wrong please. What I gather is the recommended limiter system is based on assuming your program material is very bassy. By giving the mixer a bass freq sinewave big enough to max its output you simulate the maximum feasible input to the amp. Then setting a limiter on the amp so that its output voltage is less than the recommended voltage for the cabs that are to be connected.

Being that my amp is not rated for any more than the T39 so long as I keep the mixer out of the red all will be well, yeah?

[BrentEvans]

at my amp is not rated for any more than the T39 so long as I keep the mixer out of the red all will be well, yeah?

Not necessarily. Amps are capable of short bursts of voltage much higher than their rating. Those short bursts can toast a voice coil nearly instantly, and are what peak limiters are excellent at filtering.

[bgavin]

The last outdoor gig I did was well under 20v at the T39s. Well under.

[Gregory East]

at my amp is not rated for any more than the T39 so long as I keep the mixer out of the red all will be well, yeah?

Not necessarily. Amps are capable of short bursts of voltage much higher than their rating. Those short bursts can toast a voice coil nearly instantly, and are what peak limiters are excellent at filtering.

Exactly, so where do these "short bursts" originate? What is a short burst?

The last outdoor gig I did was well under 20v at the T39s. Well under.

50W apiece, I'm not sure what I'm supposed to make of that. I know you like to run things cool. What's the rest of the story? Top to sub ratio low as well I presume? Or the nastiest thing in the subs was a bohdran?

[Bill Fitzmaurice]

Exactly, so where do these "short bursts" originate? What is a short burst?

Dynamics. Live sources have a very wide dynamic range, on the order of plus/minus 10dB being not at all unusual. That means that while your system may be coasting along at 100 watts average output it will routinely drop to as little as 10 watts and jump to as much as 1,000. Compression in the area of 2:1 to 4:1, depending on the source, will reduce that swing to perhaps plus/minus 5dB, but that still leaves a lot of swing. You could compress at a higher ratio, but then the sound will be too sterile. The purpose of a limiter is to allow you to run moderate compression levels for a natural sound while preventing the most dynamic passages from pushing the speakers beyond their limits.
With recorded media compression isn't necessary, they already did that in the studio. But there's still enough dynamic range to make limiting necessary.

[Gregory East]

Thanks Bill. So I get the drummer to give me his worst and flang the bass at the same time and so long as that doesn't overload on the PFL we're safe, if less noisy than we could be with limiting.

[Bill Fitzmaurice]

so long as that doesn't overload on the PFL we're safe

Maybe. You're assuming that if you do so the amp won't put out more than the maximum voltage that the speakers can handle. There's only one way to know if that's the case, and that's to constantly monitor the amp output voltage. Then if it does exceed the voltage rating, and you can react to that and turn the amps down within a millisecond or two, you'll be safe. Personally I'd rather use the right tool for the job, especially when said tool costs less than one replacement driver.