Introduction To The Matching Amplifier To Speakers Guide
Table of Contents
Basically, amplifiers (often also called amps) amplify an audio signal so that the desired level is emitted from the loudspeakers.
We have to start explaining what are Ohms and Watts. Once this is understood, the rest of the matching amplifier to speakers guide becomes very simple.
Ohms And Watts
Before we begin with this matching amplifier to speakers guide, you need to know about ohms and Watts.
Now, ohms are all about resistance to electricity. Everything has ohms including you. If something has a lot of ohms it means that electricity has trouble getting through. If instead, it has fewer ohms, that means electricity runs through it really easily.
A thick piece of rubber, for example, has a lot more ohms than a metal pole.
Also for our purposes today, resistance and impedance mean the same thing: They are both measured in ohms. Impedance is thoroughly described in a separate paragraph inside this matching amplifier to speakers guide, but well below in the article. If you just want to match an amplifier with a set of speakers, just keep reading our step by step approach.
Watts is all about power. More power equals more watts.
Step By Step Matching Amplifier and Speaker
The main part of this matching amplifier to speakers guide is this part. I explain to you here what to look in the specifications of the amplifier and in the specification of the speaker.
I recently got a pair of JBL jrx 125 s. They each have a horn and two 15-inch speakers and I think they sound really good. But they are unpowered or passive. Therefore, I had to find an amplifier before I could get any sound out of them.
Thus, the first thing to do was to find the specifications of the speakers. With all the specs pulled up, I was only interested in a couple of numbers of this specifications sheet: the “Nominal impedance” (for example 4 Ohms), and the “Power capacity” (for example 500 Watts). With that information, I was ready to choose an amplifier.
You should never turn on the amplifier without a speaker connected.
Now there are two main rules of thumb when choosing an amplifier for this matching amplifier to speakers guide.
The first rule of thumb: get an amplifier that is 50% more powerful than your speakers when your amplifier sends watts to your speakers, it is making them work. Their job is to pump out the sound.
Thus, the more watts they get, the more work they have to do. Your speaker can only do so much work over a long period of time.
Remember our specification sheet example. There are two numbers: one was the Power capacity which was 500 watts. Other specification sheets may call it “Continuous Power Capacity” RMS Power handling or Program Watts, but they all mean the same thing.
You should be ignoring, for now, the attribute “Peak power capacity”. if I tried to play 2,000 watts out of my JBL’s (declared by the manufacturer as the “Peak Power Capacity”) I would probably blow them to smithereens. It is way too much work for them to do but 500 watts is fine. They can play 500 watts 24/7 no problem.
Now your amplifier needs to be 50 percent more powerful than your speakers. For this same reason. This is because your amplifier is also doing work for you. The job of the amplifier is to pump watts to your speakers.
Think of it this way. If you are on foot, you can walk a lot further than you can run before you are completely exhausted and have to stop. Therefore, if my amplifier is rated at 800 watts pushing a 500 watts speaker, it will be equivalent to an easy paced walk. But if instead it is rated at 500 watts pushing a 500-watt speaker would be more like the equivalent of a strenuous run. You would be pushing it to its limits and it would wear out pretty quickly.
Thus, whatever you do do, do not under power your speakers unless you want to ruin your amplifier.
The bottom line of this reasoning. Since my pair of JBL jrx 125 each had a power capacity of 500 watts in a 4-ohm load I was looking for an amplifier that could push at least 750 watts per channel in a 4-ohm load.
Now we are getting back into Ohms, a concept explained above. So that brings me to the second rule of thumb.
The second rule of thumb of this matching amplifier to speakers guide: Match your speaker’s ohms to the ohms that your amplifier can handle.
Now, amplifiers are generally designed to work with 4, 8, and 16-ohms speakers. But it is very important to know exactly what your amplifier can handle. If your speaker’s ohms are too low for your amplifier you run the risk of blowing out your speakers and frying your amplifier completely. Please do not make that mistake.
Now if your speaker’s ohms are too high for your amplifiers, you will not obtain much sound out of your speakers. It is not as bad but it is still not good.
So since I’ve got two speakers with a nominal impedance of four ohms, I need an amplifier capable of handling 4 ohms. But remember the first rule of thumb. Thus, I also need 750 watts to power my speaker so I need 750 watts in a 4-ohm load.
That is why I decided to go with an XTI 2002 from Crown to power my JBL speakers. Here, as I could observe on the specification sheet, it is capable of pushing 800 watts in a 4-ohm load per channel. This means per speaker left and right (one speaker is a channel for this setup, so we have two channels, for left and right).
I could not ask for a more perfect match. I have even got 50 extra watts of power per speaker and now as it appears on the specification sheet, it is even capable of handling an impedance of 2 ohms.
Real Case: Another Example For This Matching Amplifier With Speakers Guide
This is another example to complete our matching amplifier with speakers guide. We are doing the same evaluation as in the paragraph above. With this information, the next one, you can do it yourself.
Example: Find a set of amplifier speakers that go well together.
Imagine you want to pair a Bowers & Wilkins 707 S2 with the integrated Rotel A12 amplifier. We looked at the Bowers & Wilkins specifications:
Impedance: 4 to 8 ohms.
Sensitivity: 84 dB.
Recommended power: Between 30 and 100W continuous at 8 ohms.
Then the Rotel:
Impedance: Minimum 4 ohms.
Power per channel: 60 W at 8 ohms.
Let’s look at the impedances. The speakers work from 4 to 8 ohms and the amplifier needs speakers with a minimum of 4 ohms. OK. We classify the boxes by their sensitivity: 84 dB. They are not very sensitive.
We see what power they recommend to move the speakers: between 30 and 100 W. As the boxes are not very sensitive, we need an amplifier that is close to the maximum of the recommended power. The Rotel outputs 60 W, and 60 is slightly less than half the range 30 – 100. It would not be a recommended amplifier. We would need an amplifier between 80 to 100 W continuous, for example, the Rotel A14.
Adding More Speakers: Matching The Amplifier With More Speakers
This topic is handy, why? well, so far in this matching amplifier to speakers guide, I have only discussed a 2 speaker setup scenario: one per each channel. A very common landscape. But what if I wanted to add more speakers? Well before I do that I need to make sure that it has the same impedance rating as the speakers I have already got.
Since my JBL’s have an impedance rating of 4 ohms, any speakers I add must also have an 4 ohm impedance rating let’s say.
I would add one extra speaker to each channel in parallel giving me a total of two speakers per channel (up to now I have only one speaker per channel).
To calculate the new impedance load of your speakers it is really easy: you just divide your speaker’s impedance rating which is 4 ohms in our case, by the number of speakers you have.
Therefore, the new load per channel comes to 2 ohms (4 ohms divided by 2 speakers) and that is a low number of ohms. But it is cool because I have checked this sheet of my amplifier and I know that I’m in the clear and I know that it can handle an ohm load that small.
Practical Example: Connecting a 4-Speaker Display
Now let’s see how the speakers of 4-speaker displays are usually connected to each other. I’m going to assume the 4 speakers are 8 Ohms.
Two speakers will be connected to each other in parallel. The total impedance of these two loudspeakers will be 8 / 2 = 4 Ohms.
The other two loudspeakers will be connected to each other, also in parallel. The total impedance of these two speakers will also be 8 / 2 = 4 Ohms
We then have two sets of two speakers, in which the speakers of each set are connected to each other in parallel. Well, now what you do is connect those two sets to each other in series. The result will then be 4 + 4 = 8 Ohm
Using this connection, all four speakers will have the same total impedance as a single speaker, so the amplifier does not find it out. Anyway, do not worry. This is an internal connection within the display, and it is common to have switches and connectors on the outside of the display to choose between different display configurations.
Bridged Mono And Stereo Setups
Furthermore, a lot of amplifiers also have an option for bridged mono.
What is bridge mono? Well, rather than taking two inputs and sending amplification to the left and right channels like you would in stereo mode, you are getting one input and combining the power of the left and the right channels into one super-powerful channel
Stereo Operation As The Standard Mode
Stereo operation mode is the normal, default mode of an amplifier. This means that the amplifier provides power to two independent channels.
Think of it as two amplifiers in one. Many recent amps can even run two different power/resistance ratings on the two channels at the same time. Usually we run two outputs (left and right) from a mixer, into the two amp channels (left and right), and then into two speakers set up in front of an audience, one on the left, one on the right. This enables an audience to enjoy the stereo effects of music.
The Setup In Stereo Mode
In regards to amplifier setups in stereo mode, I have a typical architecture of my mixer board back of my amplifier my two speakers.
In stereo mode, I have two inputs coming from the mixer and I have two outputs as well. Each output has a red and black post wherein red is for positive and black is for negative.
Both the left and right channels should be at the same volume and this is my personal preference. In the comments, you will see that some of our readers instead, would set them at different volume levels.
What Is Bridge Mono?
Bridge mono mode combines two amplifier channels into one mono, a much more powerful amplifier channel. This is most often used for subwoofers. Amplifiers have separate stereo and bridged mono power handling specifications.
For instance, the Alto MACRO 1400 amplifier is rated at 310 W at 8 ohms STEREO, and 900 W at 8 ohms BRIDGE MONO. The advantage of bridge mono is that you have a much higher power rating; the disadvantage is that you have only one amplifier channel.
Connecting speakers to an amplifier in bridged mono mode is different from the stereo mode. Usually, you connect a banana plug to the middle two banana outputs. You must also flip the amp into bridge mono mode, using dip switches on the back of your amp. Consult your amplifier manual for specific directions on your particular model.
The Setup In Bridge Mono
The bridged mono setup looks a little different.
The first thing you have to do in your device is to flip the switch from Stereo to Bridge Mono which is very important.
I still have my mixer but this time I am running through a crossover (see in the next paragraph what is a crossover and how does it work). Why through a crossover? You do not usually want to run your high-frequency speakers in bridge mono unless you got a really big setup.
So what is a crossover? well, it is basically a device that lets you separate different frequencies. In this case, it is singling out the bass completely and cutting out the mids and the highs.
There is only one input from my crossover to my amplifier. There is no second input because we are going to mono, which means “one channel”. “Mono” in Latin refers to something that is only one unit.
As we mentioned before above, we are also bridging channels 1 & 2 into a powerful channel as we said. So the outputs are going to be different as well. Now the positive post on output 2 becomes the negative post for your powerful output and the positive post on output 1 comes the positive post for the powerful mono bridged channel.
Now the volume control on channel 1 comes the volume control for the entire thing and I have got that cranked all the way up since I am not using the volume knob for channel 2. I just turn that all the way down so there you have it.
How Audio Signal Works
The audio signal usually comes from a mixing console in which it has been pre-processed or from an input device such as a CD player or computer.
An amplifier converts power into an audio signal. The audio signal used for control should only be larger but not changed otherwise.
The reason for this is the complexity of the loudspeaker. A loudspeaker (similar to a dynamic microphone) consists of a magnet, voice coil, and a membrane. The voice coil is mounted in the magnetic field and is deflected when the current of the amplifier flows through it.
The diaphragm, which is firmly connected to the voice coil, then moves the air and generates the sound pressure. Due to the weights of diaphragm and coil and the electrical resistance of the voice coil, a lot of power is needed to generate high sound pressures. In addition, the mass inertia and interactions of the loudspeaker with the air ensure that the impedance (= frequency-dependent resistance) of the loudspeaker is not constant over the frequency range.
The nominal impedance of a loudspeaker is typically 4 or 8 ohms. At 8 ohm impedance (R), an amplifier must generate a voltage (U) of 8 volts for a current (I) to flow from one ampere (U=R*I), which corresponds to a power (P) of 8 watts (P=U*I).
Due to the above-mentioned effects, the impedance is unfortunately not constant, it can range between 4 – 20 Ohm with an 8 Ohm loudspeaker. Amplifiers must, therefore, be equipped with ample reserves to cope with these fluctuations.
The Output Power Of An Amplifier
The output power of the amplifier determines, among other things, the achievable volume. The sensitivity of the loudspeaker used, expressed in dB/watt at a distance of 1 meter, also plays an important role.
An amplifier with 200 W at an 8 Ohm loudspeaker sends 40 Volt voltage to the loudspeaker, resulting in an output current of 5 Ampere (I = U/R). Conversely, 40 volts multiplied by 5 amps produce the output power of 200 watts (P = U*I).
If we now want to double the deflection of the diaphragm, we also have to double the current, i.e. from 5 to 10 amps. Since the impedance of the loudspeaker is still 8 ohms, we have to apply double the voltage, i.e. 80 volts. If we now calculate the output power of the amplifier, we come to 80 V * 10 A = 800 W, a quadruplication! It is therefore not surprising that large public address systems require amplifiers, some of which have an output of several kW.
Power Limits Of An Amplifier
The power that an amplifier can deliver is limited. For example, the voltage that an amplifier can deliver can be as high as the voltage that the power supply can deliver. If an attempt is made to exceed this power, the signal is cut off (where amplifiers nowadays have protection circuits that prevent it from being exceeded). This so-called “clipping” leads to the typically distorted sound of an overdriven power amplifier.
Power supplies with higher voltages and powers are technically no problem, but increase the costs and weight of the power amplifiers.
At some point, the maximum power, which can e.g. be delivered by a socket (230V/16A), comes into play.
The minimum permissible impedance is another important parameter of the amplifier. It should be less than or equal to the impedance of the connected speakers. The lower the impedance of the connected loudspeakers, the higher the current and therefore the power that has to be supplied by the amplifier.
You should, therefore, pay special attention when connecting several loudspeakers to one amplifier channel. If the loudspeakers are connected in parallel, the impedance is considerably reduced.
Two 8 Ohm loudspeakers in parallel correspond to 4 Ohm impedance, 4x 8 Ohm in parallel correspond to 2 Ohm total impedance, which is often the limit that an amplifier can achieve. As we already know, the impedance of an 8 Ohm loudspeaker can vary between 4 and 20 Ohm depending on the frequency, 4x 4 Ohm in parallel then correspond to 1 Ohm total impedance! If the total impedance is too low, too much current flows in the output and the amplifier overheats and (hopefully) switches off.
Power, Watts, And Volume
It is common to think that the more you power, the more volume. Watt (W) refers more to what a loudspeaker can withstand and how much power an amplifier is able to deliver. Power is usually indicated in amplifier specifications as continuous output power or RMS and dynamic power (or peak power).
The most important thing to keep in mind is what is called “continuous” power. This one tells us how powerful an amplifier is. For example, “50 W in continuous power at 8 ohms” means that the amp gives 50 W to an 8 ohms loudspeaker.
The dynamic power or peak power measures the maximum power that the amplifier can take out in some circumstances (which usually last milliseconds) when a song requires it.
You will find that some loudspeaker manufacturers simply indicate the recommended power within a range and specify neither continuous nor dynamic. In these cases see that the continuous power of the amplifier falls within the recommended power range of the box.
Sensitivity Of The Loudspeaker In dB
This parameter is only found in the specifications of one loudspeaker. It means what volume level you hear one meter away (2.28 ft. Meters are the unit of measurement here) from the loudspeaker when you amplify it with 1 W of power.
For example, a loudspeaker with a sensitivity of 88 dB will give a volume just at that level if you are one meter away from the loudspeaker and amplify it with 1W. To give you an idea of what decibels measure (dB), a normal conversation is usually between 30 and 50 dB, a vacuum cleaner about 65 dB, a street with a lot of traffic can reach 75 dB, a police siren, 90 dB, and within a nightclub, we can reach 110 dB.
This does not really tell you anything, but it is a way of indicating how loud a speaker sounds. At the same distance and at the same amplification power, a loudspeaker with low sensitivity (e.g. 85 dB) will sound lower than a more sensitive loudspeaker (e.g. 88 dB) in the same room and configuration.
What you have to keep in mind is that a loudspeaker, the more sensitive it is, the less amplification power you need to make it sound like the volume you like. For practical purposes, we can divide the sensitivity of a loudspeaker into three ranges:
Low Sensitivity: Less than 85 dB.
Normal sensitivity: 85 dB to 88 dB.
Very sensitive: More than 88 dB.
When you have a loudspeaker that is not very sensitive, the power of the amplifier should be close to the maximum recommended power of the loudspeaker. If you put an amplifier whose power does not exceed much of the recommended minimum, you will always have to have the amplifier at a very high volume to sound.
On the other hand, if you have a very sensitive speaker, you can connect it to an amplifier whose continuous power is close to the recommended minimum. It does not matter if you put in more amplification as long as it’s within the recommended range, but you will always have to work with the amplifier at a low volume or you will not be able to withstand as much sound pressure.
Another thing you might want to know about sensitivity: You have to double the amplification power to increase the sound pressure level (SPL) of a loudspeaker. For example, a loudspeaker with 88dB sensitivity needs 1 W to give that dB at 1-meter distance. Well, 2 W would give 91 dB and 4W, 94 dB.
And the volume drops 6 dB every time you double the listening distance to the speaker.
What Is Impedance? Why It is Useful To Analyze Impedance?
There is a very important parameter when connecting loudspeakers to an amplifier, which is called “impedance“, and which is measured in Ohms.
It could be said in this matching amplifier to speakers guide, that impedance is the resistance provided by an electrical audio signal when passing to a particular device (speaker) from an audio source. We must always choose the minimum impedance values supported by our audio source (amplifier), as this way the signal would arrive with more force.
There must always be a match between the impedance of the amplifier and the impedance of the speakers. The higher the ohms, the lower the output power of the speakers. If the impedance of the speakers you put in the example is from 4Ω, 6Ω and 8Ω and the amplifier only send from 6Ω, that (6Ω) should be the correct impedance.
The basic idea is that the loudspeakers that we connect to the amplifier must be within the Ohms range that the amplifier supports. If what we connect “has less Ohms”, we can charge our amplifier, especially if it is a tube amplifier.
Generally, amplifiers need to have connected speakers that have an impedance of at least 4 Ohm (this is a reference value, which depends on each amp). The range of impedances allowed is usually indicated on the back, where the cables connecting the amplifier and loudspeaker are located.
Several outputs may appear for 4, 8 or 16 Ohm (these are the most common values), or a single output indicating the allowed impedances. The value indicated on the back of the amplifier is the total impedance of what we connect. This means that we can connect more than one loudspeaker, as long as we respect the indicated values. When more than one speaker is connected, the total impedance depends on the impedance of each speaker, but also on how the speakers are connected together.
It is not the same to connect the speakers in parallel or in series. It is common to connect the same speakers, all of which have the same impedance.
Let’s see some examples of what happens when you connect several speakers: – Two 8 Ohm speakers in series. In a series connection, the total impedance is calculated simply by adding the impedance values of each of the loudspeakers. So the total impedance will be 8 + 8 = 16 Ohm – Two 8 Ohm speakers in parallel. In a parallel connection, things change. We have to use the following formula, in which Zt is the total impedance, and Z1 and Z2 the impedances of each of the speakers: (1/Zt) = (1/Z1) + (1/Z2).
In practice, if the speakers have the same impedance, the calculation is greatly simplified: the total impedance will be half the impedance of one of the speakers. That is, for two 8 Ohm loudspeakers in parallel the total impedance will be 8 / 2 = 4 Ohm
You will see the impedance in both the amplifier and speaker specifications. It measures the electrical resistance of your components and is measured in ohms (Ω) and is an important part of determining the synergy between your speakers and your amplifier.
The loudspeakers are normally between 4 and 8 ohms and the amplifiers normally give a range of between 4 and 16 ohms. If the impedance of your speakers falls within the amplifier’s range, we are doing fine.
Please note, however, that the specifications of the amplifiers indicate the output power according to impedance. For example, an amplifier can give 80 W per channel in 8 ohms and 4 ohms, but power peaks of 80 W in 8 ohms and 150 W in 4 ohms.
Higher impedance speakers can usually be connected to an amplifier but not the other way around. For example, do not connect 4-ohm speakers to an 8-ohm amplifier. Anyway, the most common thing nowadays is to find amplifiers and loudspeakers with a wide range of impedances, so what we have just told you does not usually need to be looked at very much. If one of your components is quite old, you might have to look at it.
An amplifier can be forced to send more power than it supports if we connect a few speakers 2Ω and the amp works from 4Ω, for example. There are amplifiers that have switches (or software control) to choose different output impedances that change the way energy is managed by limiting the current output. This avoids problems in demands that cannot be assumed by the amplifier source (audible distortion, clipping…).
The amplifiers of a certain power or high range do not usually have these systems because they do not require that level of self-protection and are able to deliver enough current without risk.
Normally amplifiers are assigned an impedance X, which usually corresponds to the minimum allowed. If you connect speakers from 8Ω to an amp from 4Ω it should support that power demand without problems.
The problem for the amp would be to connect speakers from 4Ω to this one, being the minimum impedance supported from 8Ω. A loudspeaker working at 100W to 8Ω will work at 200W to 4Ω and at 50W to 16Ω (always respecting your limits).
It is always necessary to use the same impedance in the transmitter as in the receiver. This way you get the most out of the signal and therefore the background noise will be less. The lower the impedance, the greater the sensitivity.
This is especially important if we pull long distances of the cable where background noise can arise. For a ‘home’ use this point does not affect so much. The lower the impedance the lower the consumption! This is a point to keep in mind The important thing is that the amp doesn’t work more ohm than the speakers (you could burn the amp). Otherwise, there wouldn’t be much of a problem.
Connecting Amplifiers And Speakers With Guitar Cables
The cables that connect amplifiers and speakers are not guitar cables even if they look like them. Do not use guitar cables.
A much higher current (amps) circulates through the speaker cable than through the guitar cable, and for that reason, it has to have a larger section. In other words, the copper wire that goes through the inside of a speaker cable is considerably thicker than in a guitar cable.
If we use a guitar cable to connect amplifier and speaker, it is very likely that we will load the cable first and consequently the amplifier. Well, you always have to be aware that when we talk about impedance we are talking about energy sending sensitivities.
Conclusions Of This Matching Amplifier To Speakers Guide
There is no perfect synergy between amplifiers and speakers. It is true that, over the years, and by listening, one can point out ideal couples.
If you are looking for an amplifier for your speakers, speakers for your amplifier, or both, do not worry too much. The important thing, as in everything, is to choose a good product that fits the impedances and powers as we explained above.
Not always you need to follow this matching amplifier to speakers guide because sometimes you just use the set of speakers coming with the equipment. For example, the Pioneer Kuro we review here, has speakers that can be detached from the TV and positioned away from the device.
If so, the equipment will sound good. Another thing is that you like one sound more than another… but it will always be subjective. One recommendation we can give you is to choose amplifiers and speakers from the same brand or group of companies. They are usually very well studied and sometimes you can even buy them in packs.
But there will always be other factors that will affect the final sound: the size of your room, the size of the speakers, their placement, and so on.