ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: 1 ... 6 7 [8]   Go Down

Author Topic: Behringer NX6000  (Read 2796 times)

Art Welter

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1700
Re: Behringer NX6000
« Reply #70 on: May 28, 2020, 03:36:37 pm »

I've been an amateur sound guy for about 20 years but i've never set up limiters before funnily enough. I know what they are and what all the controls do but I never thought to myself "I must learn about proper limiting" as club sound systems i've set up before have had amplifiers matching the speakers continuous average power so it was easy.
Jack,

That approach works fine with music with relatively high crest factor as used to be common.
A peak limiter as built into most amplifiers will offer little protection for music with a low crest factor.
A 6000 watt peak amp only averages 120 watts playing music with a 20dB crest factor.
Drop the crest factor to 3dB, and most amps will current limit, as you are aware- the NU/NX6000 can still deliver around 1800 watts of sine wave, enough to cook voice coils rated at 1600 watts without a clip/limit light going off.

Safe "club sound system limiting" for your "1600 watt continuous" subs should probably be around 800 watt RMS, using a slow attack of around one second, 1000ms or so. Music with a crest factor of 10 dB or more would be unaffected, while the sine/square wave squashed stuff will be reduced to a "cool" level, only reducing the peak level of it by 3dB. Without the RMS limiter, voice coil heating/impedance rising could reduce level by that much (or more) so not likely to be noticed.

Art
Logged

Jack Hawkins

  • Newbie
  • *
  • Offline Offline
  • Posts: 41
Re: Behringer NX6000
« Reply #71 on: May 28, 2020, 03:49:19 pm »

Power compression is one reason I advised clubs to stick with amplifiers that are rated to output continuous average power of the speakers or subs. I made them aware that if they used amplifiers that could deliver twice the speaker or sub's continuous power handling a dj could easily blow the rig by pushing levels up and that power compression could eat up as much as 5db anyway so they weren't really gaining anything with regards to spl output. Do you say 800 watts RMS because apart from JBL's 100 hour torture test of their drivers most or even all other drivers are rated in AES which is a 2 hour rating? Or is it because the ACTUAL continuous sinewave power handling of a driver is MUCH lower than it's AES rating? I know i've had JBL subs before and my god they could take a bashing, I always found JBL to be able to take some serious power and the older systems could take easily more power than they were rated at and the power compression artifacts were not audible as far as I could tell. I say atifacts I mean the lowering of sound level.

I had some Peavey UL215H cabs years ago too and they suffered the worst power compression i'd ever heard. You could actually hear the sound level going down very slowly and very soon after first powering them up full at my dance music parties. They were loud as hell (and that bloody 22XT compression driver harsh on your ears too I might add) but only for a while then they lost serious sound level and after about an hour the sound level was MUCH lower. I've never known a driver to suffer so badly from power compression as the old Black Widow drivers from about 15 years ago.

But yeah I think you're saying what I already know that a driver's AES rating doesn't indicate how much power it can handle if given a sinewave and the NX6000 can output 1,700 and something continuously into 4 ohms with a sinewave.
« Last Edit: May 28, 2020, 03:56:45 pm by Jack Hawkins »
Logged

Luke Geis

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2064
    • Owner of Endever Music Production's
Re: Behringer NX6000
« Reply #72 on: May 29, 2020, 03:38:02 pm »

No, he is referring to the actual dissipated wattage. With dynamic music, the RMS or CF is rather low ( as in further away from 0db ), so the peak level of the signal will flicker the peak light, but the actual beef of the energy is considerably below that peak. You are only dissipating a fraction of the capable power. As your CF goes down ( as in closer to 0db ) you are dissipating more and more energy over time ( higher RMS ), so dissipated wattage is obviously higher as well.

This is why it is generally best to measure the actual voltage produced by the amplifier. I believe they even make RMS voltage meters/DMM's that can give you good data points. With the amps output voltage known, you can convert to wattage and know with pretty good certainly what actual power you are producing.

Dbu, dbFS and db are different ways of measuring energy. There is not exactly a direct correlation between some of the different standards, but you can generally extrapolate the data points by the info on the box. A mixer, for instance, may have metering that shows db and goes up to +16db. The output of that mixer is typically rated in dbu though and can range from between +12dbu all the way up to +26dbu depending on the quality of the equipment. Using the standards available to us, we know that +4dbu is = to 1.228 volts, whereas a standard reference voltage for 0db is .7746 volts ( most just say .775 ). dbFS does not exactly have a reference voltage because dbFS is related to digital zero. So you have to refer to the input and output specs of the device. If the unit says it has an input capability of +21dbu and an output of +24dbu, you effectively have a device capable of a +21db input signal or a voltage of 8.69 volts RMS or 24.58 volts peak to peak to achieve input clipping.

Understanding how an amplifier works is the most important part. There are a few different topologies for gain factor. Fixed gain and fixed voltage are the two most common. A fixed voltage is pretty self-explanatory. X voltage in will = full output ( usually 1.4v ). Fixed gain requires a little more math. The basics of fixed gain is that it requires Xdb less than the rated output to reach full gain. This is usually a 26db setting. If you take the amps rated wattage at X ohm's and reduce that by 26db you will come to the required input voltage needed to achieve that wattage. For example: If an amp delivers 500 watts per channel into 8 ohms. The full output voltage is then around 63Volts (P=V*V/R). with a 26db input sensitivity, it takes 26dB less than full output, or 3.2V, to drive to full power.

Fixed gain amps require math to come to the conclusion of the input voltage required for full output.

The amps knob is an attenuator, it DOES NOT change the sensitivity of the amp, it simply reduces the incoming signal so that you can do gain staging. The standard excepted use of the attenuator knob is to turn it all the way up and then remove it so it can never be changed. With modern DSP, all the fun gain staging and control settings are done either 100% prior to, or 100% in the amp. There is typically little need to touch a knob that if it gets moved, can really make or break things. This is where the DSP comes in. If you set your mixer to clip and then get the input of your DSP to clip and the set the output of the DSP to just make the amp clip, then you have gain staged and there is no need to move the knob on the amp.

Circling back to limiting, again it is all about data points. You either have to know all the math, or you have to do it by ear.

My prescription is to know what you need vs what you have before you get to the gig. If you know you will need 140db of chest-thumping bass for 24 hours straight, you better have a PA capable of 150db+ if you want it to survive. That extra 10db is just for headroom and keeping the potential dissipation of heat to nearer the speaker's continuous rating. If you only have something just capable of 140db, it won't last even an hour no matter how much limiting you have.

Logged
I don't understand how you can't hear yourself

Art Welter

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1700
Re: Behringer NX6000
« Reply #73 on: May 29, 2020, 04:02:19 pm »

Do you say 800 watts RMS because apart from JBL's 100 hour torture test of their drivers most or even all other drivers are rated in AES which is a 2 hour rating? Or is it because the ACTUAL continuous sinewave power handling of a driver is MUCH lower than it's AES rating?
Jack,

The AES2-1984 (r2003) power rating has the LF driver mounted in free air.
Power is determined as the square of applied rms voltage, divided by Zmin. The driver is driven with pink noise extending one decade upward from the manufacturer’s stated LF limit of the device. The noise is bandpass filtered at 12dB per octave and the peak-to-rms voltage ratio of the noise signal is 2:1 (6 dB).

The problem with the rating is Zmin (the minimum impedance) is generally much lower than the average impedance over that range, so the power generated by the voltage may only be a fraction of the rated “power”.
As an example, in free air, an  “8 ohm” speaker may be over 80 ohms at Fs (30 Hz), dropping to 6.5 ohms at 150 Hz, then rising to around 9 ohms at 300 Hz.
The AES nominal power rating of “1700 watts” would use around 105 volts (105 x105=11,025/6.5=1696), while the impedance average by an “eyeball” guess is nearly double that, so actual power absorbed is only around 850 watts.

In a cabinet, the impedance curve is different- at Fb (box tuning) the impedance is now the lowest. When a droning bass line concentrates it’s power in a range of low impedance, the power absorbed can easily be double what the AES rating would indicate to be safe. To make matters worse, at Fb, the cone/voice coil excursion (movement) is at minimum, so heat is not pumped out as effectively as in free air, where the opposite occurs- maximum excursion at maximum impedance.

Art
Logged

Art Welter

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1700
Re: Behringer NX6000
« Reply #74 on: May 29, 2020, 04:10:48 pm »

This is why it is generally best to measure the actual voltage produced by the amplifier. I believe they even make RMS voltage meters/DMM's that can give you good data points. With the amps output voltage known, you can convert to wattage and know with pretty good certainly what actual power you are producing.
One can only be certain of the actual power absorbed at a given frequency if the impedance at that frequency is known.
Logged

Jack Hawkins

  • Newbie
  • *
  • Offline Offline
  • Posts: 41
Re: Behringer NX6000
« Reply #75 on: May 29, 2020, 04:17:28 pm »

Thanks guys you've been a great help, it's all confusing but it's fun to learn more. I did buy the Sound Reinforcement Handbook a few years ago but when I moved it got put into storage, I need to get it out of storage and read it more to learn because it's a hugely complex book. How did you both come to know so much? Did you do an electrician degree course or something, i've been told before that understanding electricity and voltage of audio equipment is essential to get a good grasp of how to properly understand the more complex aspects of sound engineering. I never got into that side I started out in 1994 helping to do the sound for a Chippendales concert, that got me into speakers and subs etc...It was Martin Audio F2 and instantly I fell in love. From 1993-2001 I was a raver going to many raves and always went to the amps and speaker cabs to see what they were, I was always amazed at the amp racks full of Crown MA5002VZ amps and Crest CA18 with Drawmer DL441 compressors to help keep levels under control. It was only in about 2002 I really picked up my love of speakers and stuff and started to buy my first p.a system and learn as much as I could.

But I never got any help no-one helped me or taught me so I had to learn myself, i've always been what i'd call an amateur although by 2006 i'd learned quite a bit about compression, eq, using real time analyzers to tune sound systems, but then learned a couple of years later that the sound will sound good at the point where the measurement microphone is but won't reduce reflections. I learned from my days of having a recording studio how to use automation on equipment and learned about using soft furnings to dampen flutter echos and try to get the room's reverb time down.

But anyway my knowledge has mainly been eq'ing, compression, setting up sound systems, gain structure, I learned about power compression and things like that but i've always been a bit intimidated by things like dbu, db, using an oscilloscope and the more complex side of electricity and voltage within audio systems.
« Last Edit: May 29, 2020, 04:28:48 pm by Jack Hawkins »
Logged

Dan Mortensen

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 785
Re: Behringer NX6000
« Reply #76 on: May 29, 2020, 04:26:55 pm »

There's an astonishingly good amount of information in this thread, and it's been fun to read it even though my comprehension doesn't keep up with my reading.

I think it would be great if you guys wanted to share some of this in person at one or more of my Section's presentations for sharing audio info in 5 minute increments (maybe we change that for one so you guys can get into it?). There's another thread about that which is probably just below this one. /derail.
Logged

Jack Hawkins

  • Newbie
  • *
  • Offline Offline
  • Posts: 41
Re: Behringer NX6000
« Reply #77 on: May 29, 2020, 04:30:17 pm »

There's an astonishingly good amount of information in this thread, and it's been fun to read it even though my comprehension doesn't keep up with my reading.

I think it would be great if you guys wanted to share some of this in person at one or more of my Section's presentations for sharing audio info in 5 minute increments (maybe we change that for one so you guys can get into it?). There's another thread about that which is probably just below this one. /derail.

I edited my reply to give you guys an idea about what i've learned and that it's mainly the electrical side that intimidates and overwhelmes me.
Logged

Luke Geis

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 2064
    • Owner of Endever Music Production's
Re: Behringer NX6000
« Reply #78 on: May 30, 2020, 03:33:22 pm »

It is more physics than electrical. An EE degree wouldn't hurt though. I wouldn't run off to get a physics degree either. I don't have a degree, but having done this for 20 years, I feel I have a pretty good grasp of it. My skill set is more in electronics. I build and design guitar amplifiers in my spare time. My big thing is keeping it fun and less uber technical. After a while, you rely less on the math and your experience just pays off.

Art, you are correct that what frequency X wattage is being created at is a little different than just knowing the voltage seen at the amp's outputs, but again keeping this in line with the Fischer Price nature of this thread, that is something Jack is likely not able to extrapolate. If he can get the voltage, he has the nominal impedance of the speaker, which means he can at least guestimate what wattage he is dissipating. It ballparks him.

Circling around to my major points. If he has limited the bandwidth with HP and LP filters as suggested, minds his P's & Q's for not clipping the amp, and does gigs that are easily within his gears capability, then any basic form of limiting that manages peak media and perhaps even mild RMS management, he should have little to worry about.

Jack, electrical stuff is rather easy once you remember the conversions. Watts, amps, voltage, resistance/impedance/ohm's et all seem daunting until you learn how to exchange data with it. The Ohm's law table helps tremendously with that. Now here is the big gotcha, the P,I,V,R table doesn't have frequency. That is another level of understanding. Another factor is time. Again something that is another level of understanding. When you factor power over time and at what frequencies, you can do some very calculated and mathematical decisions for how to do all the questions you ask. The problem is acquiring the data, knowing how to correlate it, and finally knowing what you can do with it. Much of which I was trying to keep out of this thread. I have contributed a lot of words that focus on the general principle of it, avoiding the deep knowledge path it can easily lead to.

You can't learn all this stuff overnight and much of what Art and a few others are telling you is Tier 1, top-level stuff that means little to you right now. And even if you did know it, you probably don't have the tools to acquire the needed data points. So again, moot or at least challenging information. Not to downplay where you are at, you are doing it and that is what matters, but many here forget that others are playing in the shallow end of the pond, and they don't always simplify the information to layman's terms. They are 100% correct and the information is extremely valuable, and their purpose for saying it is to correct or clarify generalizations ( many of which I make ) for a better and more correct understanding. It just flies over some heads and means nothing when the #s and information don't directly answer the questions and give you little insight as to why the formula is good and how to implement your tools with it.

For now, read all you can and try new things. but also remember the K.I.S.S theory. Keep It Simple Stupid. Dumbing it down a little is a good way to get your feet wet and then slowly introduce more advanced and deep techniques or ideas. Avoid sensory overload and just learn 1 new thing per day. Most all of the things you do with sound-related stuff is only executable in the field or a nice warehouse where you can make as much noise as you want. Remember that all the math presented doesn't have a sound, it is just practical application and like any blueprint, there are always revisions and as built prints made in the end.
Logged
I don't understand how you can't hear yourself

Jack Hawkins

  • Newbie
  • *
  • Offline Offline
  • Posts: 41
Re: Behringer NX6000
« Reply #79 on: May 31, 2020, 04:45:36 am »

Thanks, i'll get my Sound Reinforcement Handbook out read as much as I can the amount of information in there is unbelievable.
Logged

ProSoundWeb Community

Re: Behringer NX6000
« Reply #79 on: May 31, 2020, 04:45:36 am »


Pages: 1 ... 6 7 [8]   Go Up
 



Page created in 0.063 seconds with 24 queries.