How to connect a power amplifier to passive loudspeakers

hello everyone and welcome to glb productions in this video i'll be showing you how to connect a power amplifier to a set of passive loudspeakers now in all pa systems there are certain common components all pa systems have inputs for example vocal mics guitars keyboards and drums these inputs are generally connected to a mixer or a mixing console we have an example here this is a yamaha mg series console that you've seen in a number of my videos mixing consoles are then connected to loudspeakers they may be connected through a graphic equalizer or parametric equalizer but in simple pa systems the mixing console will be connected directly to the loudspeakers in today's world you have the choice of two types of loudspeakers you have active loudspeakers and passive loudspeakers active loudspeakers such as the jbl eons and the mackie srm series have the power amplifier built into the back of the loudspeaker and as a result you only have to deal with connecting one unit now in the early days all loudspeakers were passive and required an external power amplifier such as the unit that you see below the mixing console here in the case of passive loudspeakers the mixing console is connected to the power amplifier and the power amplifier is then connected to the loudspeakers and this is the process that we're going to focus on today so let's begin by having a look at the equipment that we're dealing with now now i need to stress that there are many hundreds of brands of power amplifiers and loudspeakers and as a result the advice that i'm going to give you today in this video has to be somewhat general and you need to apply it to your specific situation and the equipment that you are using fortunately just like analog mixing consoles power amplifiers and passive loudspeakers have been around for a long time and generally speaking the controls and signal and indicator lights on each one are by and large the same most power amplifiers today are either one or two rack spaces this refers to the height of the front panel if you're working with an older system you may have some that are three rack spaces high or even some of the very old four rack space high power amplifiers especially some of the pvs they're still around today just because they were so well built on the front panel you will usually see a series of louvers or grills this is to allow airflow through the amplifier it's very important that these not be blocked some of them will have foam air filters others will just be open amplifiers use cooling fans to draw air through the chassis to dissipate heat amplifiers generally will ventilate either from front to back or back to front some crown amplifiers actually ventilate from front and then they expel the hot air out of the sides of the chassis but that is a relatively unusual design it's important that when you are racking amplifiers you not mix the front to back with the back to front types because if you do then generally the hot air will get recirculated in other words some amps will blow hot air out the front panel which will then be drawn in by the amps that draw air in the front and blow it out the back and vice versa if amplifiers overheat they generally will shut down which means the end of your show and generally the end of your job so you have been warned if we zoom in on the front panel of this amplifier you can see that it has two channels almost all power amplifiers nowadays have a minimum of two channels you will occasionally encounter something that is called a mono block amplifier these are more common in home stereo and home theater setups most modern amplifiers have at least two channels you will have amplifiers that have four six and even eight channels in a single chassis uh some of the lap grouping amplifiers uh spring to mind that now have six or eight channels uh you have level controls these may be a physical potentiometer like you see here or they may be some kind of digital encoder then you will have something to tell you that the amplifier is receiving signal something to tell you that you are clipping the input meaning that you have distortion or that the amp has detected distortion and finally some sort of protect or a light that tells you that the amplifier is in trouble and has muted its output you may or may not have status indicators you can see at the bottom here you have an indicator for parallel mode one for crossover active and one for bridge motor mode active i will explain all of these terms in due course on the right side of the front panel you can see there is a power switch on some amplifiers the power switch is on the back on other amplifiers there's no power switch at all and it's just powered on when you connect the power cable you can see that this amplifier has a little amber light there that says standby what that means is is that the power supply is energized but the amplifier has not actually been turned on now when you switch the amplifier on you'll notice that it has a startup sequence the protect lights come on and this in this case it does not indicate a problem it just indicates that the amplifier is starting after a while you can see they've gone out and the amplifier is good to go there's a blue light there and the standby light has gone off power amplifiers are generally fairly simple pieces of equipment and as long as you don't let them overheat they generally will cause a minimum of fuss now let's take a look at the back panel of this amplifier as you can see you have the heat sinks here as well as another set of louvers this particular amplifier uses front to back ventilation so the hot air will be coming out here hence why the heat sinks are located towards the back of the amplifier on the right side of the back of the chassis you have the inputs located there are two sets of inputs because it's a two channel amplifier and as you can see the feature set is fairly comprehensive you have xlr trs as well as rca for a home or commercial use next to the inputs you have three sliding switches which are recessed into the panel so that they can't be adjusted accidentally you have the amplifier sensitivity switch this controls how much gain the amplifier gives you you have crossover on or off this particular amplifier has a built-in analog crossover not all amplifiers have this feature and finally you have the mode switch bridge parallel and stereo these will all be explained subsequently panning across to the right hand side of the amplifier you have the outputs these are what are called binding post outputs basically there's a hole in the side here and you unscrew this you put in bare loudspeaker wire and then you twist these down which clamps the wire against the terminal next to them you have spikon connectors the spikon connector has become the de facto professional loudspeaker standard especially for mobile applications it is safe and it is also very reliable if you are using an older amplifier you may have a connection via a ts or guitar type jack make sure that you do not mix up your amplifier cable with your normal guitar jacks even though the connectors are the same you may have connection via banana plugs or spade lugs or even just a bare wire which is screwed into a terminal strip you'll need to work out what your particular amplifier uses here's the power cable now some amplifiers will have an iec connector on the back panel but most higher power amplifiers will have the cable hard wired into the amp chassis this is to prevent you using a really skinny power cable that may melt under the load that is created it's important to give power amplifiers due respect these generate voltages that can be life-threatening if you connect to them in the wrong way always treat a power amplifier with the same respect as you would treat any live electrical circuit because people have been killed in the past by mis by malpractice and now a look at the back of the loudspeaker that we're going to be dealing with here this happens to be an ekler verso 12 loudspeaker cabinet you can see here it says verso 12 passive loudspeaker cabinet if you're in any doubt as to whether your loudspeakers are passive or active the best way is to look and see if there is an ac input on the back of your loudspeaker similar to that on your mixer or other electronic equipment if you see one then it's active if you see these speakon type connectors the same as the ones on your power amplifier then it is passive now the first step in connecting a power amplifier to a passive speaker is to ensure that your amplifiers and speakers are matched this is something that you only need to do once and if you buy your system as a system from a professional outfitter this process should have been done for you nevertheless it's still good to know what exactly is involved so step one is to determine the power handling capability of your loudspeakers this is sometimes posted on the loudspeaker itself so you can see that it says here impedance 8 ohms power 350 watts rms it's important to understand that this does not mean that you have to use a 350 watt amplifier for this loudspeaker there's always a range of power amplifiers that you can use and the best way is to consult the documentation that comes from the speaker manufacturer so here i've printed out from ecler and you can see it says there verso 12 between 350 and 700 watts now what about if you don't have this information how do you know what sort of power amplifier to use as a general rule you want to use a power amplifier that provides between the rms and double the rms so a power amplifier that provides between 350 and 700 watts rms the next step in our process is to verify the impedance of our loudspeakers as you can see this one says impedance 8 ohms most single woofer designs so 1 by 10 with horn 1 by 12 with horn are 8 ohms some of the larger loudspeaker designs especially the double 15 with horn enclosures that are very often used by djs as well as the big subwoofers can be four ohms so it's really important to check that because that will affect how much power your amplifier is able to deliver to the loudspeaker now that we've determined the power handling as well as impedance of our loudspeakers we need to double check the power delivery of our amplifier into that impedance once again we need to consult the specification sheet that is provided with the power amplifier we know that we are dealing with the xla1600 you can see there's a couple of other models in that series now on this spec sheet it lists power into 4 ohms 8 ohms and 8 ohms bridge we know that our loudspeaker is 8 ohms therefore we want to look at the 8 ohms stereo and for the xla 1600 it is 450 watts rms we know that for the verso 12 we want an amplifier of between 350 and 700 watts into 8 ohms so this amplifier appears to be a great match now so far we've only discussed using one loudspeaker per amplifier channel in larger systems it's common to run more than one loudspeaker off each amplifier channel so for example you may have one amplifier at front of house and you're using channel one to drive two loudspeakers on the left and two loudspeakers on the right in that case how do you work out your power handling the first thing is you need to work out what is the combined impedance of all the loudspeakers that you are loading onto each amp channel the formula for this is the impedance of one loudspeaker divided by the total number of loudspeakers assuming all loudspeakers are the same so two eight ohm loudspeakers gives you four ohms four eight ohm loudspeakers gives you two ohms so on and so forth so let's say that we were driving two of those verso 12s off each channel of the xla 1600 would we still be okay going back to our documentation you can see that we would now have to consult the 4 ohm stereo line because 2 8 ohm loudspeakers result in a combined impedance of 4 ohms the amplifier delivers 760 watts into 4 ohms each loudspeaker would get exactly half of that 760 divided by 2 is 380. we know that our loudspeakers can take anything between 350 and 700 therefore we are still okay now all power amplifiers have a minimum specified impedance below which they will generally have thermal issues on this particular power amplifier it's four ohms so could i run four versus 12s off each channel the answer is no because four eight ohm cabinets gives you a combined impedance of two ohms and the power amplifier would shut down this is especially important when you are matching subwoofers to amplifiers because many subwoofers have two drivers in each cabinet and are often four ohms so you will find that you need to do the math and be aware of the specifications of your system now the next step in our process would be to connect the mixing console to our amplifier and i have the mg124cx here obviously in a real setup the mixer would be located at front of house and the amplifier would be either in a rack nearby or in a rack near the loudspeakers but this is just for demonstration purposes so in order to understand how to connect your mixer to your amplifier a little bit of understanding of amplifier modes is required amplifiers generally operate in three different modes the first is referred to as stereo mode this is the most common mode and in this mode input to channel 1 of the power amplifier goes to the output of channel 1 input to channel two of the amplifier goes to the output of channel two so it operates as two independent channels they can be used for left and right or in some smaller systems you may use channel one for your front of house loudspeakers and channel two for your monitor loudspeakers it's up to you there are two identical independent channels for you to use however you want the second mode is called parallel in parallel mode input to channel 1 goes to the output of both channels and input to channel 2 disappears in other words the the input to channel 2 is not used this is used typically when you are driving a large number of loudspeakers from a single amplifier so in a slightly larger system you might have one power amplifier which is dedicated to front of house right loudspeakers and you're using that amplifier to drive maybe two or four loudspeakers on that side of the stage the third mode is bridge or sometimes called bridge mono now in this mode the two amplifier channels work together to drive a single large speaker enclosure channel one pushes and channel two pulls figuratively speaking now this setup generally requires special cabling and is beyond the scope of this video it's usually used in conjunction with subwoofers so today what we're going to do is we're going to hook up this setup in stereo mode so we confirm that the mode switch on the bottom of our amplifier is in stereo and then we proceed to run an xlr cable from the left output of our mixing console into input number one on our power amplifier and then we do the same for our right from right output of our mixing console to the left the input of channel 2 of our power amplifier now before we move on a word about daisy chaining amplifiers i remember that one of my subscribers asked me say i have my mixing console and i need to connect to four separate amplifiers how would i do that there's two ways to do this the first is to use different outputs from your mixer to connect to each amplifier so for example some mixers have two sets of main outputs one on xlr and one on trs you could use the xlr outputs to connect one amp and the trs to connect to a second amplifier the other way of doing it is to daisy chain the amps themselves you'll notice that this amplifier has xlr inputs as well as trs and rca inputs these are all connected internally so the unused inputs can also be used as outputs to the next amplifier in order to accomplish this you'll need an xlr to trs adapter cable which looks something like this this one has seen better days it's been used for many years and what you would do is you would simply connect the trs to any unused input on that channel and then use the xlr male to connect to the next amplifier and you would just repeat this down the line on the better amplifiers these inputs are buffered so there will be no concerns about impedance now let's have a look at connecting the amplifier to the loudspeakers with all modern amplifiers you will need a set of good speak on loudspeaker cables now a speak-on cable will have one of these on each end of the cable and you can see there it says speakon and l4 fc there are various models but the these are the latest ones the the pins are actually there they're just shrouded and this is one of the things that makes these an extremely safe and reliable connector they're also locking a word about loudspeaker cable it's important to use the heaviest gauge loudspeaker cable that you can afford and also to keep it as short as you possibly can if the run from your loudspeakers to your amplifier is 10 meters don't have a 50 meter loudspeaker cable or something like that you're wasting power and you're generating just excess heat now how do we plug in to one of these it's important to understand that the spikon is a locking connector and it will only go into the amplifier output one way the way that i always tell people is latch at 11 o'clock as you can see there it will only go in with the latch at 11 o'clock any other way it will not once you're in turn to lock once it's locked it won't come undone to release you have to pull back on this latch turn and then the cable comes out so i've pulled the camera back a little bit to give you a better view of how this is you can see we have our mixing console connected to the back of our power amplifier and then we're now going to connect the power amplifier to the inputs of the loudspeakers so output of channel one to the input of the loudspeakers the way of connecting on both ends is exactly the same latch at 10 o'clock turn to lock you can use either of the inputs on the loudspeaker once again they're connected internally in parallel now let's say that you had another loudspeaker that you needed to drive from that channel how would you do it you've only got one output on the amplifier for that particular channel so what you would do is you would simply daisy chain out of the first loudspeaker so you take another speak on cable connect to the output or the link of the loudspeaker and then run this to your second loudspeaker and connect it there if on the other hand you were only connecting one loudspeaker to each amp channel you would take the same cable connect to channel two and then run this into the second loudspeaker and your connection is done uh it's a very good idea to make sure that your equipment especially your power amplifier is off while you are making these connections just as a form of cautionary insurance finally a word about setting amplifier level controls meaning the knobs on the front a lot of people think that the amplifier should be set to maximum and then the overall level of the system adjusted using the main output on your mixer this is not actually correct the reason that you'll see a lot of amplifiers in big systems set to maximum is that that is an easily reproducible level and very often those systems will include a system processor which adjusts the gain for each amplifier electronically in a small system it's important to treat the amplifier level control as effectively the volume knob for your entire system everything before that should be running at optimum signal to noise ratio using the gain procedure that i've mentioned many times in my videos the amplifier control is what determines how loud your system goes so if you play a small venue it may be lower if you play a large venue you may need to turn it up more the other thing that we need to discuss is this control here sensitivity on some amplifiers this may be labeled gain on other amplifiers it may not be present at all it's internal and not user adjustable i think that the best explanation for this comes from the good folk at crown who makes some of the best amps in the world uh this is a printout from the crown amplifier application guide it's a little bit technical but i recommend it for you you can search it on google as you can see here it says amplifier level controls are typically not gain controls they do not control the amount of gain the amplifier produces power amplifiers are designed to produce a set amount of gain gain in this case refers to the increase in voltage that the amplifier provides the function of the level control knob typically is to adjust the signal level coming into the amplifier input stage the non-technical explanation for this is that it controls how depth the amplifier is with the level controls turned down the amplifier can still reach full rated output power it just takes more drive level from your mixer to achieve it so turning the amplifier level controls down does it mean that you're gonna get less wattage from your amplifier it just means that you have to hit the input a little bit harder in order to achieve that so don't think that by turning your amp down you're robbing your system of power you're not all right so how do we set these uh controls again the folks at crown help us first make sure your mixer or console is operated optimum signal to noise without clipping the output then begin at the 26 db position turn up your amps level controls until you achieve the desired level of loudness if it's not loud enough turn the level controls all the way down and then change the sensitivity switch to the next position so as you can see here this particular amp gives us two different levels of gain you have 26 db of gain and 32 db again begin at 26 db if it's not loud enough go to 32 db well that's it for this video i hope the information presented here has been useful to you as i mentioned there are hundreds of different brands and models of loudspeaker and power amplifier so the advice given in this video is quite general by necessity if you have a challenge or an issue that you can't seem to solve do please get in touch with me either through the comments section below this video or on facebook and we'll see if we can work it through together this is bruno luz for glb productions thanks for watching and i'll see you in the next video

Channel: GLB Productions

Views: 1,557,239

Keywords: Audio Power Amplifier, Audio Equipment, sound reinforcement, audio mixer, Ecler XLA 1600, Ecler verso 12, mixing console, speakon, PA system, sound system

Id: NqTqJ4zOJJU

Length: 30min 36sec (1836 seconds)

Published: Thu Apr 09 2015