The peaks are produced by resonant frequencies and back EMF, while the troughs happen when the reactance portion of the speaker impedance drops to zero. This means that any change in voltage has an immediate effect on the charge in current through the speaker driver. A speaker driver is designed with a conductive voice coil attached to a moveable diaphragm. The voice coil is suspended inside a gap in a magnetic structure.
As electrical audio signals are passed through the coil, a changing magnetic field is induced, and the coil and diaphragm oscillate. Ideally, the diaphragm will move in the exact same waveform as the audio signal to produce sound that is completely representative of the audio signal without distortion. To learn more about speaker drivers, check out my article What Are Speaker Drivers? How All Driver Types Work.
The key point here is that speakers have conductive voice coils and these coils naturally have electrical impedance. There is a constant DC resistive element to the voice coil and speaker driver as a whole. This electrical resistance is the same across all frequencies and is often at or just below the minimum impedance value of the speaker driver.
The more interesting part of the frequency-dependent impedance of the speaker driver is the back EMF and the reactance of the driver. The speaker driver has a fundamental resonance frequency Fs. This is the frequency at which the speaker driver naturally wants to vibrate.
It is easy to make the driver vibrate at its resonant frequency and more difficult to make it vibrate at other frequencies. Simply tapping the speaker diaphragm will cause the driver to vibrate at its resonant frequency.
Subjecting a speaker driver to a sound wave at its resonance frequency will also cause it to vibrate at this frequency, similar to a tuning fork. At this resonance frequency, there is a spike in impedance. This may seem counterintuitive. The driver moves with the least amount of physical resistance at its Fs, yet it portrays a sharp increase in its impedance of electrical current.
As mentioned, applying a voltage across the voice coil will induce a magnetic field in the coil, which causes it to move.
This is how speakers ultimately work as transducers. The opposite is also true. Moving the voice coil within a magnetic field will induce a voltage across the coil. This voltage is in opposition to the voltage that would cause the coil to move. This is called back electromotive force.
At the resonant frequency, the speaker driver will want to vibrate freely, which causes an increase in back EMF and, therefore, an increase in impedance. This may cause several spikes in the overall impedance of the speaker. Oftentimes these peaks are damped or tuned in the speaker design to help achieve a smoother impedance graph.
Inductive reactance is a property of an AC circuit like a voice coil in a speaker driver that opposes the change in current.
Reactance is similar to resistance in the fact that it is measured in ohms. Notice the difference in the definitions: reactance opposes the change in the electrical current while resistance opposes the current itself.
Both reactance and resistance are factors that make up the overall impedance of a speaker driver. The hertz values represent cycles per second. We know that the current of higher frequency signals changes direction more times per second than lower frequency signals. The reactance of a voice coil, therefore, opposes higher frequencies more than it opposes lower frequencies.
Now imagine having multiple drivers within a single speaker unit. Most loudspeakers are designed with at least 2 drivers a woofer and tweeter , and many are designed with more. As we can imagine, each driver will have its own effect on the overall impedance of the speaker unit.
This can cause several peaks in the overall impedance that coincide with the resonance frequency of each driver. Note that crossovers are used to send specific frequency bands to the drivers that will best reproduce them. Therefore, the increase in high-frequency impedance due to inductive reactance will likely only be a result of the tweeter as no high-frequencies will be sent to the midrange speakers or woofers.
Note that each driver may also have a different nominal impedance, which may dramatically alter the overall impedance graph. A speaker enclosure improves the performance of a speaker by effectively blocking off the rearward out-of-phase sound waves from the speaker driver. In an earlier article we looked at the issues involved in connecting multiple speakers to one amplifier. In this article we look at some I am often asked "How do I connect multiple speakers to my amplifier?
You may still have many video tapes that you like to play but find it hard to connect a VCR to your new flat The recent passing of Eugene Polley, the man known for inventing the remote control, has given me cause to reflect on the development of It works similarly to a VCR, but This is the summary of the previous five articles looking at the different video signals and connectors commonly used in Home AV.
Previously we Connecting your TV is not as hard as it looks. All the sockets on the back and up the side of a flat screen This is the In this article, we look at component video signal: what it is, where it is used, and what cables are used for component video In this article we look at RGB video signal: what it is, where it is used, what cables to use and the problems with In this article we look at S-video signal: what it is, what cables to use, where S-video is used and the problems with it.
Do phone chargers and Ipod chargers draw power when not connected to their device? The answer is: it depends on the type of charger. In the popular press there have been a number of reports along the lines of "households wasting hundred of dollars on standby power". Being an inquisitive In this article, we look at composite video signal: what it is, what cables to use, where composite video is used and the problems Calculators Speakers in Series Calculator. Jump Straight to Calculator The calculator below is useful in determining the total impedance of speakers in series.
This calculator for amplifier power, voltage and current has little significance but is rather interesting. In the specifications for an amplifier, it might say This distributed speaker system SPL calculator takes the guess work out of which speaker tap to use.
It will tell you the correct power Jump Straight to Calculator This calculator will help you determine the cable losses in distributed speaker systems also known as volt or volt speaker systems Calculators Decibel Calculator for Audio voltage.
If you don't like formulas then you definitely won't like the formula for calculating voltage ratios expressed in decibels. So, use the following calculators to Here is a simple calculator for power, current, voltage and resistance actually there are 6 different calculators, use the one relevant to the values Calculators Power Usage Calculator.
Knowing the cost of running an electrical appliance is useful, and easy with this power usage calculator. You need to know three things: 1.
Cost of These calculators will find how loud an amplifier and speaker combination will be, or what size amplifier you need to make a speaker a Calculators Lighting Costs Comparision Calculator. Energy efficient LED lamps for lighting are very popular. They certainly cost less to run than conventional lamps. But how much do you really Calculators Speaker Dispersion Calculator. If you look at the specifications of speaker boxes, you should see something like Dispersion H x V : 90 x This is stating How much do you need to increase the gain of an amplifier to make it sound twice as loud: 3dB, 6db or 10 dB?
Most countries have a stated maximum continuous noise level over a continuous 8 hour period a working day. This is normally agreed to being Fundamentals Using a Multimeter. This article introduces the basic concepts of multimeters and explains how to use them for basic measurements. Multimeters are one of the most useful Fundamentals AC and DC. This article looks at some basic concepts and misconceptions of AC and DC electrical circuits.
I want to increase the resistance on my 5 surround sound speakers and my subwoofer by 2 ohms from 6 to 8. I was thinking about inline resistors. My question is do I use 2 ohm resistors to take 6 to 8 and do I put them on both the positive and negative speaker lead or just one of them. If both would I put 1 ohm on each lead to get 2 ohms total? Since you are increasing resistance in a series circuit the amplifier won't know or care where in the circuit the resistance is.
The problem is that your speaker isn't just a resistor. It is largely an inductive load and since it has mechanical resonance favourite frequencies to vibrate at the situation becomes more complex.
A good amplifier will have a strong drive to force the speaker to the correct position at any instant and overcome the inductance. Low resistance speaker cables are part of this equation.
Try it and see if you notice. The resistors will need to be rated to handle the power. Make sure to get appropriate resistors, they will dissipate one fourth of the maximum power your amplifier can output, per channel. If you have 50W per channel your resistors can dissipate up to Using series resistors is not something I would recommend though. The best option would be to change the speakers, but this of course come at a price, the new speakers' price.
But you can just keep your volume low enough. Keep in mind that adding resistors will let you rise the volume up to the maximum, but you will not hear a difference in actual volume since the excess power is dissipated on the resistors, which usually do not emit sounds. I am guessing you are using the system with a TV set that includes some 5. The resistor option is the safest anyway, since an unaware person can and will stop by, rise the volume and blow the protections.
An impedance matching transformer is better than a resistor in series with your speakers. It sounds the opposite of how resistance works. A zero ohm resistor would be a direct short. The same as connecting the amps outputs together with a piece of wire, or shorting them together with a screwdriver. So, maybe this lower number sounds better, could be a reason for wanting to do this?
That's just a guess on my part. A lot of speaker designers try to get the impedance number higher. The multiple drivers used in a 4 way speaker does lower the impedance, and this results in a harder load for the amp to drive. In some cases, they use resistors in series with the drivers to help raise the impedance. Yes that raises the impedance ohm number, and typically should make it easier for the amp to drive. Sometimes in a multi-driver system, they'll use higher impedance individual drivers, to get a higher impedance final number, in their design.
With all things being equal specs, size, design etc. An 8 ohm speaker is typically twice as hard to drive, when compared to a 16 ohm speaker.
Here is a resistor calculator that may help. If you add an 8 ohm load to a 4 ohm load, you'll actually end up with 2.
This also helps show you it helps to know some basic electronics, if your going to experiment this way. A lot of us look for speakers with a higher impedance ohms number, so it will be easier on the amp. I have some 4 ohm speakers that some of my amps can't drive very good.
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