Here's the short answer.

NEVER DAISY CHAIN YOUR SPEAKERS.

Your amp is designed to power speakers at a certain resistance. By running either serial or parallel, you change that resistance and thus the load on the amp. The amp itself is probably part of the problem as B*** amps are known for having horribly off the wall specs.

Basically, if you're not using 70V transformers though, you should never hook up more than one speaker to a channel of an amp.

Cheers-
J

Cucco wrote: By running either serial or parallel, you change that resistance and thus the load on the amp. The amp itself is probably part of the problem as B*** amps are known for having horribly off the wall specs.

Resistors in series follow the pattern Rtotal = R1 + R2 + R3... so don't two 4-ohm speakers in series = 1 8 ohm speaker? The amp is rated at several different impedences, according to the manual.

How do you suggest I align the two main speakers? 1 per channel?

In a perfect world, yes, the resistance of one in a series added to the other will simply equal the sum. The problems are:

1 - the load on the amplifier itself isn't a constant. Speaers present differing loads at differing frequencies and phases.
2 - If you have a speaker with an 8 ohm rating, that means that the minimum average resistances is roughly 8 ohms. I've seen some speakers that run up to nearly 10 times that at certain frequencies at odd phase angles. Compound that by doubling it (or worse, adding two differing types of loads at two differing phase angles) and you're looking for trouble.

Your best bet is to get 2 separate stereo amps (ditch the B*** line and go with the more capable Crowns. They have an inexpensive series that blows the doors off of B*** amps) and run a split our separate outputs from your mixer. (Floor wedges are often fed by aux sends).

There is information on this site by a poster by the name of "Anxious" regarding under and over powering speakers. Anxious is a VERY knowledgable speaker designer and builder and has his name on several very high-end speakers. His name is Ken Kantor and he is one of the pair of brains behind NHT speakers as well as a few newer lines as well. Do a search on this poster and you'll find your answer regarding under/overpowering your speakers.

Here's another short answer -
Distortion blows speakers (sligtly over simplified). If you're pushing your amp too loudly and it's over powering your speakers, you will indeed blow them.

If your amp is reaching its clipping point and distorting, it can damage your speakers.

The common way to blow up speakers is to operate them (or the amp) beyond the capabilities at which they're designed. Your best bet is to invest in a quality pair of speakers and a quality amp that have similar power specifications and resistance specifications and use them together.

Personally, when I see B**** amp and "daisy-chained" in the same sentence with "blown" I don't have to look for any more of a reason.

Cheers and best of luck.

J.

A few more points to add to the excellent advice in this thread:

You say you are 'daisy-chaining' your boxes together... I assume that means you plug the link out on one box into the input of the next as they were designed, rather than some custom wiring job of your own? If you are using them as intended, then 'daisy chaining' boxes means you are running them in parallel. So, your total impedance for your mains = 1 / ( 1/4 + 1/4 ) = 2 ohms.

I would personally be reluctant to run any amp at 2 ohms, as they run hotter with more distortion, and are much more likely to fail. This applies even to professional makes such as Crown; I shudder to think how a Behringer would react.

And this is without considering the unspecified number of monitors of an unknown impedance... lets assume these are 8 ohm boxes and you have 3 of them: total impedance = 1 / ( 1/8 + 1/8 + 1/8 ) = 2.66 ohms

It is not generally considered good practise to load channels differently on the same amp (I assume a dual mono-block design is too much to hope for in a Behringer?)

Another observation: you say you were running the amp with the volumes turned down quite a bit... as Cucco rightly points out "Distortion blows speakers". However, the distortion doesn't have to come from the amplifier to cause damage: a DJ can kill a speaker by redlining his mixer all night, even if the amps have plenty of headroom.

So I would suggest that you turn the amplifiers back up, and lower the input gains on your mixer instead. This should ensure adequte headroom throughout the signal chain.

And I would second Cucco's suggestion to buy a Crown amp, and would recommend one of [[url=http://[/URL]="http://www.crownaud…"]these[/]="http://www.crownaud…"]these[/]. These are excellent amplifiers which have the added bonus of built-in DSP so you could set a limiter to help protect your drivers, and could potentially go active in future without needing to buy a cross-over.

You might get away with running just the monitors from the Behringer for now, if you don't have a budget for two amps...

oh my god!!

open the amp and let it run at full power! just turn down the mixer. the amp should NEVER be used as a "volume control"! amps should almost always be run wide open.

although, the funniest thing was this:

My speakers are damaged, and I want to know why. Here's the situation:

-Berhigner

figured out a solution with just the first word!

You have been given A+ advice so far.

There are some things I think you need to crystal clear on. If by "daisy-chaining" you mean plugging the speaker cable coming from the amp into jack A of speaker #1, and then another cable from jack B of speaker #1 to jack A of speaker #2 (and so on, into an undetermind number of cabinets of undetermined impedance) - you need to be clear that this is not putting the resistances in series. As IIRs explained, that would be parallel impedances and the formula he put in his post is all you need to calculate how your impedance might be just a fraction away from a dead short (zero ohms). Your two Harbingers cabinets at 4-ohms each would result in a 2-ohm load. It's also worthing noting that the impedance listed on your speaker is the "nominal" impedance. In reality the actual impedance might be significantly lower. Which can be a problem when you start hooking them up in parallel. We keep getting closer and closer to zero ohms.

When the speaker impedance gets dangerously low the amp will usually overheat and go into thermal protection mode and shutdown. So in this scenario, the only mystery in my mind is how the cheap amp held together - without going up in flames - long enough to kill the speakers.

I'm a firm believer that everyone who takes live sound seriously should own a multi-meter and know how to use it. If you have speakers of unknown impedance, test them. If you're unsure how to calculate ohm's law, the meter will help. If you've got a bad cable the continuity checker will help you find it and fix it. String the chain of speakers together as you normally do and test the total impedance load at the amp end. It's true there are known issues in metering impedance accurately, but at least you'll be in the ballpark.

Also as a precaution I'd test the amp before I plugged any more speakers into it. If you have a meter or know someone who does, you might also want to use the volt-meter function and check the amp to make sure it's outputs haven't gone into a DC state. High levels of DC will destroy speakers as fast as you can plug them in. That will get expensive FAST. DC pushes the voicecoil out (sometimes across the room) and never lets it vibrate normally. Sometimes when an amp meltsdown it takes the speakers with it, so a quick test of the amplifier's outputs might prevent the untimely death of more speakers. Most modern designs have safeguards against it, but again with a bargain-basement amp who knows?

Check the crossover too. The Achilles heel of a cheap speaker might be the cheap built-in passive crossover. An ohm meter will be able to confirm if the speakers are fried or if the crossover has crossed-over (to the afterlife).

As far as the under-powering over-powering issue - It is always going to be better to be at or above the speakers' rated wattage. (this means real watts, not some BS 2-ohm hocus pocus) Getting double the watts out of an amp by cutting the impedance in half to 2-ohms is 100% smoke and mirrors - not real useable watts. Good speakers will often have three power ratings Continuous / Program / Peak, I would try to have the amp be at least in the neighborhood of the Continuous rating of the speaker.

If given a choice between A) running a 200-watt amp into a 100-watt speaker OR B) running a 100-watt amp into a 200-watt speaker - I'll take option A everytime.

And while we're on the subject - there are a lot of places manufacturers can fudge the wattage specs of an amp. There is a world of difference between how the top-notch amp companies [Crown, Crest, QSC, Carver to name a few of the best] rate their amps and the methods used by the cheap amp manufacturers [ a much longer list, including the one you have-sorry]. The same is true of speaker manufacturers, peak watts on paper is easy. Real world useable continuous power is what counts.

Good luck!

rockstardave wrote: ....open the amp and let it run at full power! just turn down the mixer. the amp should NEVER be used as a "volume control"! amps should almost always be run wide open....

This is very common advice, but I don't agree with it. I admit that if a system is correctly sized for a venue this is what you end up doing, but if you have an overpowered system you should turn the power amps down. If you fail to do this, you defeat the entire point of creating a good gain structure. Turing the power amp to full volume ignores the fact that the audience's ears are part of the signal chain. If the amp is full out the noise floor is at maximum possible volume and you are getting the minimum signal to noise ratio that the system can deliver rather than the maximum. Ideally, the amp should be set so that you are getting the maximum necessary SPL at the maximum comfort setting on the mix. I practice most people leave some extra volume in case they want to make everyone's ears bleed just a little. As I say, if the system is correctly sized that means the amps are turned up all the way. (In fact, that's probably a definition of "correctly sized.")

"I'm a firm believer that everyone who takes live sound seriously should own a multi-meter and know how to use it."

My apologies, dvdhawk. I might know how to use one but hell if I own one. Or a SPL meter. I dunno how to solder.
Hell, I could just be a bad example to everyone and scare them into buying quality amps instead of (point 2...)

"If given a choice between A) running a 200-watt amp into a 100-watt speaker OR B) running a 100-watt amp into a 200-watt speaker"

What about 90W amps into 300W (peak)/150W (continuous) speakers? :P
(I already changed that amp to our older powered mixer which spits out about 300).

[quote=IIRs]Another observation: you say you were running the amp with the volumes turned down quite a bit... as Cucco rightly points out "Distortion blows speakers". However, the distortion doesn't have to come from the amplifier to cause damage: a DJ can kill a speaker by redlining his mixer all night, even if the amps have plenty of headroom.

So I would suggest that you turn the amplifiers back up, and lower the input gains on your mixer instead. This should ensure adequte headroom throughout the signal chain.
quote]

This is the problem!!!! at least one of them. We definately were leaving the amps at too low a volume level and redlining the mixer. I don;t knwo why I didn't figure this out earlier - it's the same reason several channels on the mixer would be maxed out and still be no where near loud enough...duh I need to turn the amp way the hell up and turn all the channel gains/volume faders way the hell down.

When we daisy-chain the mains, yes, we conect the factory-installed 'output' of one speaker to the input of the next. I was not aware that this meant I was running them in parallel. How would this compare to putting each speaker on its own channel (screw the monitors for now) and running the amp in 'parallel mode'? 'Stereo mode'?

My biggest question now is how should I run the speakers, assuming I do not buy another amp? Crappy as my amp's company may be, I cannot aimagine that there is not a way to run two 600-watt speakers from a supposedly 2400-watt amp without damaging them.

Thanks for all your input everyone - keep it coming.

Don't be stubborn. Forget about 2400 watts. Even if you wish to believe the published specs are accurate it isn't really a 2400 watt amp. 4 ohms in bridged mono mode is how you would get there with a single speaker and that isn't your application. That means one (1) line gozinta the amp input and one (1) single 4 ohm speaker gozouta. Do not try to run at 2 ohms. Really.

If you run in parallel mode at the amp itself-1 channel to FOH and 1 channel to MON-you have about 650-750 watts per channel at 4 ohms. That means either one 4 ohm speaker per channel or two 8 ohm speakers daisy chained (parallel again remember) per channel. Three 8 ohm monitors on one channel is too many. Three 4 ohm speakers is ludicrous without a k.

Even if you can't or won't dump the Behringer gear, you really need one amp for FOH and one for your MON. You still need to test your current amp and speakers with the multi meter like advised so you know what is still good and what isn't.

Alternately you could invest in some in ear monitors and do away with the monitor speakers all together.

Codemonkey wrote: "I'm a firm believer that everyone who takes live sound seriously should own a multi-meter and know how to use it."

My apologies, dvdhawk. I might know how to use one but hell if I own one. Or a SPL meter. I dunno how to solder.

To each his own. Frankly I'm surprised, you seem like a guy who likes to take things apart and see what makes them tick.

You are free to do as you please, all I can tell you is this - over 30+ years I have saved thousands and thousands of dollars in cable and equipment repairs that I would have had to pay someone else to do. Think of the new gear you can buy with the money you save over the long haul.

Bless you for volunteering your time to run sound at church.

If you ever get to where it's your investment, your profession, or serious hobby you would do well to reconsider.

Wise words from some slacker in another post:

Codemonkey wrote: "I've been meaning to learn to solder for long enough, I really should. Being a student, I don't have £20 to spare on some wire and solder etc. although I do have a soldering iron".

Over the course of a long and interesting career in this business that relatively small £20 investment will save you hundreds or thousands. A multi-meter of your own wouldn't cost much more and the ability to troubleshoot and solve a problem in 2 minutes vs, 4 hours is priceless. I keep a meter at church, I keep a meter in my truck, and 2 more meters in my toolbox.

But then again the qualifier was, "everyone who takes live sound seriously" - if you're content being the best soundman at your particular Congregational Church of Scotland, go ahead and put your feet up, you have arrived. You seem to have a great grasp of things in your comfortable environment. Problems are inevitable even in a fixed installation. And if you leave the nest and start doing field work, expect the unexpected. Good luck finding a new cable at 11pm on a Saturday night. If you strive to be better prepared and better equipped, these are tools you will have to master to get from point A to point B. Anyone trying to navigate to point B without some skill with these two simple tools had better have deep pockets.

TheJackAttack wrote: Don't be stubborn. Forget about 2400 watts. Even if you wish to believe the published specs are accurate it isn't really a 2400 watt amp. 4 ohms in bridged mono mode is how you would get there with a single speaker and that isn't your application. That means one (1) line gozinta the amp input and one (1) single 4 ohm speaker gozouta. Do not try to run at 2 ohms. Really.

If you run in parallel mode at the amp itself-1 channel to FOH and 1 channel to MON-you have about 650-750 watts per channel at 4 ohms. That means either one 4 ohm speaker per channel or two 8 ohm speakers daisy chained (parallel again remember) per channel. Three 8 ohm monitors on one channel is too many. Three 4 ohm speakers is ludicrous without a k.

Even if you can't or won't dump the Behringer gear, you really need one amp for FOH and one for your MON. You still need to test your current amp and speakers with the multi meter like advised so you know what is still good and what isn't.

Therefore, it sounds like if I do away with the monitors altogether (I have a solution monitor-wise I know will work anyway that has nothing to do with any of this), then I can put the amp in parallel mode and put one 4-ohm 600-watt Harbinger out of eahc channel, and eahc speaker should be getting about 650-750 watts. That would seem to be enough power since I've never had to drive the speakers to anywhere near their capacity in any of our applications - so I won't have the problem of clipping the amp.

But, despite the previous sentence, I will still make sure to turn each channel of the amp up to almost its full volume and leave the individual input gains/volume faders on the mixer nice and low. That way I won't get any clipping, the speakers will get adequate power, the amp will be pushing an adequate resistance...everything should be hunkey-dorey right? Any foreseeable problems?

Of course, if I find an extra $1000 on the street I'll buy one of those Crown amps and use the B. amp for monitors.

One mroe question - can someone explain if I should really use stereo mode or parallel mode here? The only difference that i know of is that the manual claims stereo mode = each output channel has its own corresponding input, while parallel mode routes one input signal to the two different output channels. But, I don't know how this works out electronically, and with regards to impedence, power, etc. therefore I don't know which mode is more appropriate here.

By the way:

Do not try to run at 2 ohms. Really.

The amp is supposedly rated for quote: "2x1200 Watts @ 2 ohms" which sounds to me like you could put two 600 watt speakers at 4 ohms each, daisy-chained in parallel, on one channel, and end up with the correct power (1200 watts for 2 ohms). But, then again, I really don't know shit and if there's one thing I;ve learned here its that manufacturers' ratings really aren't that trustworthy. Why, I don't know - it doesn't seem to their advantage to advise people to use their gear in a way that is bound to cause damage...whatever...

Thanks all. More advice is still appreciated because even though I think I know what to do, I'm still just a hair fuzzy on why I need to do it...

2 ohms makes things go boom.

I'm a Marine. I know all about making things go boom. When it absolutely positively has to be destroyed overnight....

I'll keep that in mind...

8-)

"Any" 2 Ohm rating is based on a 2 Ohm test load at a particular frequency - not a real speaker playing real music. In the real world its best to stay away from 2 ohm speaker loads.

As far as the stereo/parallel - are you running your mixer in mono or stereo? If mono you have one output from the mixer so use parallel. (This feeds the same signal to the two separate channels.) If stereo...you can figure the rest.

tr3eman9 wrote: if there's one thing I;ve learned here its that manufacturers' ratings really aren't that trustworthy. Why, I don't know - it doesn't seem to their advantage to advise people to use their gear in a way that is bound to cause damage...whatever...

Different manufacturers will have different business models.

Companies like Crown or QSC trade on a reputation for quality and reliability, so it pays them to be conservative (or at least accurate) with their specs. And their customers will be professionals that are harder to BS.

Behringer simply aims to be the cheapest, so inflating the specs makes them look like more of a bargain to unsuspecting amateurs.

BobRogers wrote: "Any" 2 Ohm rating is based on a 2 Ohm test load at a particular frequency - not a real speaker playing real music. In the real world its best to stay away from 2 ohm speaker loads.

As far as the stereo/parallel - are you running your mixer in mono or stereo? If mono you have one output from the mixer so use parallel. (This feeds the same signal to the two separate channels.) If stereo...you can figure the rest.

I think, usually, we have it in stereo mode, but the left and right signals are exactly the same (we don't pan any instruments), so I could do parallel just as easily.

I just want to know if there's any other, more technical, electronic difference between the two modes, and if there is, which mode would help my situation more.

Also (not to derail this thread but I'm just curious) why would you pan things in a live mix? It seems to me all this would accomplish is different parts of the audience hearing differenct mixes...and this doesn't seem like a good idea...

Yes. Thanks to my QSC manual for clearly wording what I started out to write and subsequently scrapped as confusing.

STEREO MODE
This is the "normal" way of using an amplifier, in which each channel is fully independent. Separate signals connect at the inputs, the gain knobs control their respective channels, and separate speakers connect to each output.
Examples:
• Two-channel (stereo) playback.
• Two independent mono signals, such as main and monitor mixes.
• Bi-amped operation, with the low frequencies in Channel 1 and the highs in Channel 2.

PARALLEL INPUT MODE
This mode is just like Stereo mode, except that the inputs for Channel 1 and Channel 2 are internally connected together. A signal into any input jack will therefore drive both channels directly. Each channel's gain control still functions as usual, and each channel feeds its own speaker load. You can patch the input signal on to additional amplifiers by using any of the remaining input jacks.
Example:
• One mono signal driving both channels, with independent gain control for each speaker system.

BRIDGE MONO MODE
This mode combines the full power capabilities of both channels into a single speaker system. The amplifier internally re-configures so that both channels operate as a unit. This delivers double the output voltage, resulting in four times the peak power and three times the sustained power into a single 8- or 4-ohm speaker load. The Bridge Mono mode section on page 11 describes the special speaker connection used.
Examples:
• Driving a single 8-ohm speaker with the combined 4-ohm power of both channels.
• Driving a single 4-ohm speaker with the combined 2-ohm power of both channels.

Precautions:
• Bridge Mono mode makes it possible to drive thousands of watts into a single speaker. AC current consumption will usually be higher. Avoid excessive signal level, and make sure the wiring and speaker can handle the power.
• If the load is 4 ohms or less and prolonged overloads occur, the amplifier will probably mute for several seconds during peaks, and the circuit breaker may trip.
• Do not use 2-ohm loads.

TheJackAttack wrote: I'm a Marine. I know all about making things go boom. When it absolutely positively has to be destroyed overnight....

....wire it to a Behringer amp!

With instrument cable :twisted:

The use of stereo panning in live sound is worth its own thread. I don't remember us ever having one. I think I'll start one.

Ok so here's a hypothetical question:

If you had two 4-ohm main speakers (lets say 600 watts each), and amp (much bigger than mine) that was way more powerful than them. Like twice the wattage (1,200 W/Ch. @ 4 ohms, in other words).

And suddenly you started playing much bigger venues and you wanted to use that extra power. You would need to get more speakers. For example, lets say you decided you needed 400 MORE watts per channel. But how would you add more speakers to the circuit without reducing the impedence to dangerously low levels?

For example, you might think getting a pair of 400-watt, 4-ohm speakers would work, as this would bring your total wattage per channel for the speakers up to 1000 W rather than 600, thus taking more advantage of your powerful amp. BUT daisy-chaining two 4-ohm speakers together would result in a total 2-ohm impedence, which, as we already disscussed, is too low.

The only way I can think of to solve this problem would be to sell your current speakers and just buy a pair of 1000-watt, 4-ohm speakers. Either that, or there needs to be a way to connect multiple speakers to a channel without doing the conventional daisy-chaining and the resulting impedence halving.

Can someone solve this puzzle?

Again this is purely out of curiosity. I have neither the desire nor the money to put this into practice. Also my amp isn't that big so if I wanted more power I'd have to get another amp anyway.

You can't run speakers in series.

Interestingly, I'm looking at a speaker of ours right now and I finally understand why it's in series.

I'm guessing there's an electrical reason why no-one TRIES to run speakers in series.

When you wire in series the load is multiplied by the number of speaker you have connected and divided by that number when you wire in parallel. You don't want to mix impedance.

Ah so 2 4ohm loads would make it 16ohm.
Wait, don't they add? Not done physics for a while so I'm probably wrong though.
I thought Rt = R1 + R2 + ...

Codemonkey wrote: Ah so 2 4ohm loads would make it 16ohm.
Wait, don't they add? Not done physics for a while so I'm probably wrong though.
I thought Rt = R1 + R2 + ...

Right and two times four is? Not sixteen.

Argh, misread that. Thought for some reason you were implying that you multiply the impedances.

Its not that uncommon for a multi-speaker cabinet to be wired in series/parallel. Most old Marshall cabinets are. 4X16ohm speakers in series/parallel to make 16 ohms total. The newer cabs with two jacks to make two 8ohm loads or one 16 ohm load and , even though I havent seen one, I'm told they have a switch on some that makes em a 4ohm load.

But.....You dont often see professional sound gear making series/parallel a connection of the day.

Lets get a couple of things straightened out. First. Your choice of power amp is not a 'good' thing. I know that the seemingly endless power and the ratings given make it seem like a bargain but now you have blown drivers and you're searching for the reason.

Next, you keep referring to the power rating of the cabinets as some magical number that will allow them to put out that many watts of program. ERRR....No, this is a manufacturing rating which allows them to deny any repairs under warranty should you decide to operate these speakers with an amp that is rated higher than the approximation of the handling power stats they post on the cabs. adding a 400 watt rated cabinet to a 600 watt rated cabinet doesnt get you 1000 watts of program.

Theres a lot more factors involved than these simple numbers.

And, as you have already heard from some serious professional sound geeks, you want a bunch more watts in your pwer than these numbers indicate....but again, it depends on a lot of things.

As has been said.....2 ohms is a place you cannot afford to go. Thats really close to DC and this is definately something your speakers are gonna have a bit of a problem with should they experience it.

Ohhh, the horror.... :!:

So lets get our syntax correct. A parallel connection will be the 'daisy-chaining' that has been mentioned...ie:output of the amp into one speaker and then the parallel jack on that speaker to the next and so forth.

This is NOT a series connection. And thus the impedance of the loads in parallel is halved with each equal addition of load. 8ohm +8ohm =4ohm.

Again these are only numbers.

Get a book and learn about these things. The Yamaha live sound book will work.

And if that B*&$%^^&#!ger power amp can put out 2400 watts of anything for over a millisecond I'll apologize for every mean word I've ever said about them.

Okay.....not really.

tr3eman9 wrote:

The only way I can think of to solve this problem would be to sell your current speakers and just buy a pair of 1000-watt, 4-ohm speakers. Either that, or there needs to be a way to connect multiple speakers to a channel without doing the conventional daisy-chaining and the resulting impedence halving.

Can someone solve this puzzle?

Again this is purely out of curiosity. I have neither the desire nor the money to put this into practice. Also my amp isn't that big so if I wanted more power I'd have to get another amp anyway.

Next pair of speakers you buy try 8-ohm speakers, they sound better.

I can solve this puzzle, but would rather not put the method out there. It can be done, but it is a very Very VERY bad idea to run separate cabinets in series.

One stereo amp per pair of speakers is by far the best solution.

There are a number of ways to solve your problem. Buy matched equipment, use higher impedance speakers when choosing equipment for parallel use, rewire your cabinets
http://www.usspeaker.com/speaker%20wiring-1.htm

PLease note SAME WATTAGE, SAME IMPEDANCE and same type, (coned speaker, horn) and these diagrams are not for passive crossover systems.

Handy diagrams. The principles are the same, but wiring two separate cabinets in series is a bit more complicated than the diagram. It would require a degree of know-how at the amp rack that Tr3 is not ready for - even if it wasn't a terrible idea.

There has been a bunch of good info. The only thing that I would like to add is that Behringer is a POS company. If you look at the power ratings for this POS amplifier, they do not list how the amplifier was tested. The info that is given is generalized, incomplete and misleading.

They give a 20-20k power rating for 4 and 8 ohms, NOT 2 OHMS.
They give a 1k rating at 2 ohms only. This is for marketing because most people do not know what that really means. The amp in question IS NOT RATED TO RUN AT 2 OHMS (SEE BACK OF AMP) NOR WAS IT TESTED AND APPRIOVED BY UL TO DO SO. THERE is your damage. The amp is unstable, cannot run full range, has a crappy damping factor and thus cannot maintain control of your speakers, which means that you have damage. The speaker didn't know if it was coming or going.

DON'T BUY BEHRINGER, EVER!

You speaker power capacity is suspect as well. That is an ambiguous rating. Was it rated using Continuous, RMS (a spec used to hide behind) AES, etc? You have to know how much voltage the speaker will handle long term, then match that with the proper amp. You need a calculator and ohms law, no multimeter.

Underpowering speakers does NOT blow speakers. Underpowering speakers with a failing amplifier, passing DC, etc does. Underpowering alone...no. Distortion alone does not destroy speakers. Guitar amps do not blow up. Mic's guitar cabs do not destroy your mains and monitors. It is a combination of things.