Math question - Speaker in parallel

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The clipping light is a good indication, but you can also measure. Since your amp is rated at 1200 watts into 4 ohms, that means it should be able to supply 69 volts RMS to your speakers before, or maybe right at, clipping.

If you wanted to limit the amp to 350 watts RMS into 8 ohms, you could dial it back to a maximum of 53 volts RMS when your source (mixing desk) is maxed out with a sine wave. You know the amp will never clip, but you might not have enough volume for your PA. It's a safe place to start, at least. With a volt meter you can st those levels.
 
I'm putting together a medium **PA system**.

4 x 350watts full range, 8 ohms, passive speakers (2 for each channel, in paralell)
Digital Power Amp with a 1200watts per channel at 4 ohms.

As I understand it, each channel will have a load of 4 ohms and add to a maximum of 700 watts.
Not "add to" because they re not producing power, a more accurate word would be : "they stand up to 700W RMS"

That will leave a 500 watts headroom, taking into account the "rule" of "1.5 to 2 times the amp".
That is a much misunderstood and misquoted statement.
It has meaning in a home Hi Fi environment, where you listen to pre recorded Music and typically at about 10% average level relative to maximum.
In that case you start with a lot of headroom, won´t ever clip the amplifier, and extra available power *adds* to headroom.

But you are talking a *live sound* PA system (a DJ would have similar problems), presumably used in a large place (definitely not your own Living Room, even less your Bedroom) and with presumably a sizable amout of people, not Family and a couple friends.

In that scenario you **will** clip your amp and damage speakers.

Unless you are obsessive controlling the peak signal and turning it down all the time, acting as a sort of Human Limiter, the normal solution is to add a limiter between preamp and power amp and set it up so it can not go beyond *average* 700W RMS per channel.
Narrow higher power peaks (cymbal crashes, acoustic guitar strumming, etc.) won´t hurt, of course.
Is my math ok? Thanks for the help.
Maqth is fine, just this idea does not apply to Live Sound, where the opposite is right: speakers at least 50% stronger than what amps can deliver.
PS: sorry if my english isn't so good.
Conmigo zafaste Hermano ;)
Igual está muy bien :cool:
 
The full range speakers are 350 watts RMS at 8ohm.
Ok, that means they most likely can handle 700w program and 1400w peak.

Since I first posted, I have added a fairly powerfull subwoofer, so the full range are now only for mids+highs.
Did you also add a crossover?

Anyway, I'm aware that if the amp is bigger than the speakers I can blow them. I just don't know if there is a way I can limit the power.
Yes.. by adding a limiter.

I asked before if the red light means the speakers are clipping or the amps are insuficient for the speakers
Neither. And speakers don't clip but amplifiers do so when you see the red clipping light flash it is indicating that you have reached the peak limits of the amplifier. It is usually safe for this indicator to flash occasionally too but you don't ever want to see it illuminated constantly, that means you are heavily over driving the amp.
 
Thank you for all the responses!

Let's see if I can reply correctly:

* That my speakers can handle 700 program is something I don't get. The peak value I grasp. Program, not so much.

* I added a "crossover" on my XR18 mains EQ, using Aux to Sub at 100Hz. That is what sounded better in my ears. Found a tutorial for the X32 by Behringer, and duplicated it as closely as I could on my XR18. I managed to make an outdoors test, and it was quite loud and no amp was clipping. I guess by substracting the bass from the main speakers they can boost the mids and highs a bit more, but that is just an assumption. As you can see by my postings, I don't know much.

* I don't know what a limiter is. Is it just bringing down the volume on the amps channels or the amps have to have a limiter? Mine sure don't.

Thank you all for your time!
 
* That my speakers can handle 700 program is something I don't get. The peak value I grasp. Program, not so much.
RMS, Program, and Peak are just terms commonly used to rate speaker power handling. Sometimes you will also see Continuous substituted for RMS. In all cases Program is 3dB above RMS and Peak at 6dB above. The bottom line is a speaker can handle remarkably high power levels for very short periods of time(miliseconds), but only a relatively small amount of steady state power over an extended period of time.. minute or hours. Fortunately most music types are very dynamic with a relatively low continuous energy levels so it works out well.

* I added a "crossover" on my XR18 mains EQ, using Aux to Sub at 100Hz. I guess by substracting the bass from the main speakers they can boost the mids and highs a bit more, but that is just an assumption.
Yes, you effectively transformed your system into a 3-way and in doing so you do get cleaner mids and highs.

* I don't know what a limiter is. Is it just bringing down the volume on the amps channels or the amps have to have a limiter? Mine sure don't.
What amps do you have? As the name suggests a limiter stops a signal from getting any stronger. A DSP processor like the Behringer DCX would give you adjustable limiters, crossovers, and some very good EQ all in one package, this type of thing isn't really optional if you want to be able to use a system like this and not have to worry about accidentally blowing something if a mic or guitar is unplugged or some feedback happens.
 
Well, I didn't post the specs of my amp because it's not a great Amp.
In fact, I don't think you are going to know the brand.

Novik D-Class D2600

Novik Neo : Products / Power Amplifiers / Detail / NOVOD 2600

Technical Specifications
Input connectors XLR
Output connectors Speakon
Input impedance 20kΩ - Balanced , 10kΩ un-Balanced
Output connections type Stereo & Bridge Output
Amplier type Class D
Frequency Response 5Hz - 30kHz ±1dB
S/N Ratio 100dB
THD 0.03% 8ohm/1KHz/half power
Crosstalk >80 dB @ Rated Output/8/1kHz
Damping Factor >1000 @ 8/1kHz
Slew Rate 20 V/uS
Stereo Output Power 8  600 W + 600 W
Stereo Output Power 4  1200 W + 1200 W
Bridge Output Power 8  2400 W
Minimum Impedance load 4Ω
Cooling System Active cooling fan
Protection Soft Start, Short Circuit, Limiter, DC Fault, AC Line Fuse, Thermal Cut
Main Power Supply AC 115/230 V – 60/50 Hz – Power Source Switching
Consumption 2750W

Thanks for all your input! It's been really helpfull!
 
WHERE did you get these figures?
Pretty much anywhere speakers are sold. This is a very complicated subject that everyone tries to distill down to simple numbers but that is difficult at best. The AES spec most common in pro audio these days is based on a noise signal with 6dB crest factor and some manufacturers try to break that up into steps, that is where the 3 power levels come from.
 
Those numbers don't make sense to me. Program is 3dB above RMS? Perhaps meaning that a speaker can take 3dB more power on music than its RMS rating? How would you figure that - from peak values?

RMS is a voltage measurement to start with and directly transferring it to power is just wrong.. but that hasn't stopped the audio industry from doing just that for decades. RMS is also a pretty meaningless spec for music because we don't listen to sinewaves(mostly.. Rap exempted), music is a much more complicated waveform so it's better to refer to the sustained power level as continuous. The most common specs used to test speakers(AES and EIA) use a bandwidth limited noise signal but again it's a bit more complicated than people suspect, here is a link to a 3rd party page that summarizes those specs.. Speaker power handling < Pro-Audio References
Notice the picture of the noise signal in that link.. it is not to scale.. here is a better one.. https://www.jblpro.com/pub/technote/spkpwfaq.pdf
 
Well, I didn't post the specs of my amp because it's not a great Amp. In fact, I don't think you are going to know the brand.

Novik D-Class D2600
Nope never heard of it but that doesn't mean much these days. The specs look fine.. actually the power output specs are a little hard to believe.. we don't usually see a perfect doubling of power going from 8-4 ohms, and the total AC consumption looks high for a true class D amp so maybe it is a hybrid with a class D power supply and a more conventional class AB or H amplifier section.
Whatever the case, if the amp makes the speakers get loud and doesn't overheat or shut down over the course of an event then it's safe to say it's a decent amp.
 
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But that does not limit the output of the amp and offers no protection, all one has to do is raise the input level to the amp the same amount... either deliberately or accidentally, and you're right back to amp clipping again.
Partly correct, partly wrong. I did this for years before pro amps had built in processing. Turning down the amp input volume controls does limit the maximum output, with a given source. As long as the source doesn't change, you know the maximum voltage at the speaker terminals. It's straightforward and it offers as much or more protection than anything else. And you know the amp will never clip.

Yes the level can be raised by accident, but that's an accident. :) Compressors and limiters get opened up all the time "by accident" so that is no more protection than the volume control. You need security screws on the rack grills to keep anyone from changing the settings - seriously.

These days pro amps have digital inputs, DANTE networking and all sorts of built in processing and limiting. Great options for protecting both the amp and the speakers. But with a simple set up like the OP? Just turn it down and lock it there. Then have the self discipline to leave it alone.
 

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RMS, Program, and Peak are just terms commonly used to rate speaker power handling. Sometimes you will also see Continuous substituted for RMS. In all cases Program is 3dB above RMS and Peak at 6dB above. The bottom line is a speaker can handle remarkably high power levels for very short periods of time(miliseconds), but only a relatively small amount of steady state power over an extended period of time.. minute or hours

The 3 and 6 dB values are widely accepted, that's something you can work with. It's not really accurate though, it would be much better, a lot more accurate if it would be specified with program or rms power and a crest factor.

Fortunately most music types are very dynamic with a relatively low continuous energy levels so it works out well.

Unfortunately exactly the opposite is the case. Especally if you play modern pop music, you'll get a very low crest factor and therefore a very high continuous power level because such music is produced with very heavy compression. Look for 'loudness war'.

Generally got live music low rms and high peaks while MP3, stream etc. but also a lot of CDs are often compressed and have therefore low peaks but very high average program levels. That means, even if you stay far above the maximum power, the constant average level is very high and can kill speakers anyway.

For folks who don't know how to recognize strong compression: If the music is loud but as soon as a i.e. bassdrum is played the music gets a lot quieter until the sound of the drum/bass etc. is over it gets louder again.
 
I remember those times, that power was enough, indeed. But times changed... Now it is not loud enough unless blood is dripping from ears.

A lot of venues now have sound level limiters.

I remember a 1976 Status Quo gig where the music was so loud I couldn't hear for 3 days afterwards.
I saw them again in 2006 and the sound level was much less.
 
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