Zakaj je slabo, če je impedanca zvočnika prenizka? Odgovor na vaše vprašanje

Lahko je zmedeno, ko govorimo o impedanci, ohmih in vsem tem v zvezi z avtomobilskimi ali domačimi zvočniki. Ja, večina ljudi pozna zvočnike, ohmske vrednosti in še več ... toda kaj to v resnici pomeni?

Točno zakaj ali je slabo, če je impedanca zvočnika prenizka? Na to bom odgovoril tukaj in enkrat za vselej razčistil.

V tem članku bom opisal vse, kar morate vedeti:

Kaj točno je impedanca zvočnika?
Dva velika razloga, zakaj je lahko nizka impedanca zvočnika slaba ... in zakaj je pomembna
Zakaj lahko uporabite zvočnike z višjo impedanco, vendar ne nižje (in kaj pričakovati)

Veliko je za pokriti, zato skočimo takoj!

Kaj pomeni impedanca za zvočnike? Govornik Ohms je pojasnil

Ilustriran pogled na dele, ki sestavljajo zvočnik, vključno z zvočno tuljavo. Glasovna tuljava je tesno navita dolga žica, ki ima določen upor uporabljenega električnega prevodnika. Ustvarja magnetna polja, ki poganjajo stožec zvočnika naprej in nazaj ter ustvarjajo zvok, ko premika zrak.

V svetu elektrike in elektronike potrebujemo nekaj stvari za koristno delo:

Vir energije z napetostjo za premikanje električnega toka skozi upor, motor itd., da naredi nekaj koristnega. To omogoča domači ali avtomobilski ojačevalnik ali radio.
Električni prevodniki (žica zvočnikov), ki ustvarijo pot za pretok tega toka
Neka stopnja odpornosti da omejite, koliko toka lahko teče (preveč toka povzroči, da stvari izgorejo, se segrejejo itd.)

Po istem principu, tako kot druge električne naprave, so zvočniki kot majhni motorčki, ki uporabljajo pretok električne energije, da spremenijo gibanje (stožec) v zvok, ki ga lahko tukaj – to so pravzaprav vsi zvočniki!

Kaj pomeni impedanca zvočnika?

Upor zvočnika, merjen v enotah upora, imenovanih omi, je skupna upora, ki ga ima zvočnik proti pretoku električne energije.

Impedanca zvočnika izvira iz dveh stvari:

Odpornost dolgega navitja žice, ki sestavlja zvočno tuljavo
Posebna lastnost, ustvarjena, ko je žica navita v tuljavo, imenovana induktivnost

Tako kot ne morete imeti kratkega stika v bateriji, ojačevalnik ali stereo potrebuje nekaj upora zvočnika, da omejite količino električnega toka, ki ga radio ali ojačevalnik skuša zagotoviti.

Glasovne tuljave zvočnikov uporabljajo zelo dolgo žico, ki je tesno navita v zvočno tuljavo, kar je potrebno za ustvarjanje magnetnih polj za ustvarjanje gibanja stožca. Zaradi te dolžine vedno obstaja določena količina upora, ki je del impedance zvočnika.

Upor določenega zvočnika je skoraj vedno nekaj enot upora, merjeno v ohmih.

Kaj pomeni induktivnost? Zakaj je to pomembno pri zvočnikih

Induktorji so zelo uporabni električni deli, ki izkoriščajo induktivnost. Induktivnost je lastnost elektronov, ki tečejo skozi žično zanko, in magnetnih polj, ki nastanejo zaradi tega. Podobno imajo zvočniki induktivnost zaradi glasovnih tuljav, čeprav majhno.

Zvitki žice imajo zanimiv stranski učinek, ki se zgodi v nasprotju z ravnimi odseki žice. Žično navitje zvočne tuljave tvori zanko, ki ima električno lastnost, imenovano induktivnost. Ko se na tuljavo z induktivnostjo uporabi izmenična frekvenca, kot je glasbeni signal, pride do nasprotovanja toku električnega toka zaradi prisotnih magnetnih polj.

This is called inductive reactance and it’s different from resistance as it changes as the frequency changes; resistance stays the same.

For speakers, this matters because it means that the total resistance is made up of the two things I mentioned:wire resistance and inductive reactance. The name used to describe this total is impedance.

For speakers, this means that impedance (the total resistance) changes slightly as music plays because of the changing sound frequencies. However, the good news is that we can still categorize speakers according to an Ohms rating since it’s always pretty close.

When we talk about the impedance of a speaker, most of the time people are referring to the range of the speaker assigned to categories like 2 ohms, 4 ohms, 8 ohms, and so on. This is how we match speakers to a car or home amplifier, radio, and so on.

In the electrical world, resistance units measured in Ohms can be written as the Greek symbol Omega, or “Ω.”

How does speaker impedance work?

When a musical signal (made up of alternating current) is applied to a speaker it generates magnetic fields as current flows through the tightly wound wire coil. Interestingly enough, a coil of wire develops magnetic fields that resist the flow of the current (resistance, also called reactance in this case).

Similarly, many other electrical components like motors deal with the same electrical resistance as alternating current (AC) is applied.

How the math works (yeah, it’s a little complicated!)

Because of how inductance works and the physics involved, the speaker “impedance” (total resistance) isn’t the sum of the resistance and the inductive reactance. Instead it’s the “algebraic” sum, meaning it’s the square root of the sum of the squares. You may remember this kind of math from trigonometry class.

Speaker impedance isn’t as simple as just adding the measured DC resistance of the coil wire and the inductive reactance for a given frequency.

Instead, speaker impedance is found from the algebraic sum of the coil’s wire resistance and inductive reactance. You can find this by squaring each and then taking the square root of the two numbers added together.

Inductive reactance is commonly written as “Xl”, pronounced “X sub L” and is measured in units of Ohms just like resistance. Inductance is measured using a unit called the “Henrie” and commonly noted with an “H”:“uH” for microHenries, “mH” for milliHendries, and so on.

There’s also a corresponding value for capacitors called capacitive reactance (Xc) but that doesn’t usually apply for speaker voice coils. It’s very important for speaker crossovers, however.

Why is it bad if speaker impedance is too low?

Just like any other device connected to an electrical power source, the speaker impedance will determine how much or how little current a home or car receiver, amplifier, etc will produce. The speaker impedance also affects how some speaker components such as speaker crossovers behave too.

What happens if speaker impedance is too low?

You can connect a higher speaker impedance in most cases without any problems (at least not major ones). A radio, home or car amplifier, etc will still produce sound and run at normal or low temperatures. That’s because a speaker with a higher impedance than expected will reduce how much electrical current the audio source tries to produce.

As a side effect, you’ll get sound but with much lower power output than you would with the correct speaker load. Car stereos or amps, for example, have to work with lower voltages than home stereos so they need a lower impedance 4 ohm speaker typically to produce more power.

Home stereos, on the other hand, have higher voltage available and can use a higher speaker impedance (8 ohms, typically).

Internal view of an amplifier. When connected to a speaker impedance load that’s too low, the amp will begin to get very hot and this can burn out the output transistors as they can’t handle the heat caused by trying to supply excessive current to a lower speaker load.

However, using a lower speaker impedance is bad because it causes the radio or amp to attempt to put out twice as much (or more!) current than it’s designed for. Your home or car stereo will get very hot quickly and if you’re lucky will go into a self-protect mode and shut itself off.

However, in my experience, it’s pretty common for the output stage electronics to burn out when connected to a lower speaker load than they should be. The high-power transistors in a home or car amplifier or stereo are only rated for a certain amount of heat &electrical current.

When they’re forced to try and handle an amount outside that range they become super hot and start to break down permanently. It doesn’t take long before the damage is permanent and they no longer produce sound.

Caution! Never wire speakers in a way that gives a total speaker load lower than the radio or amp is rated for. Also, don’t guess about the correct speaker impedance – check first.

I’ve seen cases where someone’s “friend who’s smart” has as a way to “get more power” but caused a stereo or amp to try to and put out more power than it was designed for. The end result was a burned-out amplifier.

Why does speaker impedance matter for crossovers?

Speaker crossovers work to separate the sound sent to certain speakers for improved sound, reducing distortion, and to give you more control over how they’re used. For example, they block bass that tweeters can’t produce and highs that a woofer can’t produce well. However, they’re designed for a specific speaker impedance. Changing the speaker impedance affects the sound.

Speaker crossovers are amazingly helpful for getting better sound with speakers. Even the cheapest, most basic capacitor connected inline with a tweeter working as a high-pass filter makes a big difference in the sound.

The result is cleaner sound and avoiding possibly damaging it when bass sounds are played.

The catch is that because of how crossover components (capacitors and inductors) behave, they’re designed for specific speaker loads and can’t be used with other Ohm loads without affecting the sound output.

Crossover shift when using different impedance speakers

When you change the speaker impedance connected to a speaker crossover it can significantly shift the crossover’s cutoff frequency. As a general rule:

Halving the speaker impedance (ex.:8ohms to 4 ohms) doubles the frequency
Doubling the speaker impedance (ex:8 ohms to 16 ohms) halves the frequency

That’s bad because it allows the speakers to be sent a sound range they’re not suited for. In the case of tweeters, bass &midrange are bad because they can’t produce it properly. Similarly, many woofers can’t produce high frequency sounds well.

The end result in either case is poor sound that’s a lot worse sounding that it should be. If you change the speaker Ohms load you’ll have to replace the speaker crossover as you’ll need different parts values for it to work the same.

Is 8 or 4 ohm better? Is higher or lower impedance better for speakers?

8, 4, and 2 ohm speakers aren’t necessarily “better” than one another. The correct answer is that it depends on the application and what stereo or amplifier is being used. The best impedance is the one that matches an amplifier or stereo’s impedance spec correctly.

By industry tradition, 8 ohms are used for home and some theater speakers. 4 ohm speakers are generally used for car and marine audio, with some 2 ohm models also (usually subwoofers).

For example:

8 ohm speakers are used in home stereo systems and require 1/2 the current of a 4 ohm speaker. That means they can use smaller speaker wire as they can take advantage of home electrical systems that have a high voltage supply for driving speaker amplifiers.
4 ohm speakers are used because car stereos and amplifiers (particularly car head units) can’t make large amounts of power in speakers as they have a very low 12V power supply. Reducing the speaker impedance from 8 to 4 means we can double the power for the same output voltage.

As a matter of fact, car stereos can only put out about a small 15-18 watts RMS per channel, despite the exaggerated peak power ratings you may see in advertisements. That’s because they only have about 12 volts to work with and have to divide that in half in order to produce AC waves that drive a speaker.

Car amplifiers are able to deliver huge amounts of power to 4 and 2 ohm speakers. They use an internal “inverter” power supply that steps up the +12V supply to higher voltages. This way they’re able to supply much more power to 2 or 4 ohm speakers than would be possible otherwise.