Kako povećanje impedancije zvučnika utječe na dB glasnoću i izlaznu snagu?

Utječe li promjena impedancije zvučnika na glasnoću (decibeli ili dB ) dobit ćeš? A što je s snagom – kako se to mijenja?

Volio bih pomoći da se sve ovo raščisti! U ovom ću članku obraditi sljedeće:

Što je impedancija?
Kako se dB izlaz (glasnoća) mijenja ako povećate impedanciju zvučnika
Razlike u snazi i glasnoći stereo automobila i kuće povezane s impedancijom zvučnika

...i puno drugih izvrsnih informacija. Čitajte dalje da biste saznali više!

Što je impedancija zvučnika?

Impedancija zvučnika, mjerena u Ohmima, je ukupna glasovna zavojnica otpor protoku električne struje dok radi s glazbenim signalom.

Kad god možete da napon isporuči struju koja teče kroz žicu, potrebna vam je određena količina otpora da ograničite koliko može teći. Isto tako, pojačalo ili stereo treba barem neki otpor zvučnika (opterećenje zvučnika, ako hoćete) kako bi se ograničilo koliko električne struje radio ili pojačalo pokušava isporučiti.

Za razliku od ravne žice koja ide od točke "a" do točke "b" kada priključite napajanje, namot žice glasovne zavojnice tvori petlju koja ima električno svojstvo koje se zove induktivnost. Induktivitet se malo razlikuje od otpora jer ima otpor ovisno o frekvenciji izmjenične struje (AC) koja teče kroz njega.

To se zove induktivna reaktancija.

Impedancija zvučnika mijenja se s frekvencijama glazbe – donekle

Za automobilske zvučnike to znači da se stvarna impedancija (ukupni otpor) zapravo malo mijenja dok svira glazba! Međutim, dobra je vijest da zvučnicima još uvijek možemo dati ocjenu u ohmima (ocjena impedancije zvučnika) jer je ona uvijek unutar određenog raspona kao što su 2 ohma, 4 ohma i tako dalje.

Kada govorimo o impedanciji zvučnika, većinu vremena ljudi misle na kategoriju (opći raspon) zvučnika koji se koristi za usklađivanje kućnih ili automobilskih stereo pojačala.

U svijetu elektrike, Ohmi se ponekad predstavljaju grčkim simbolom Omega, ili "Ω."

Kako radi impedancija zvučnika?

Kao što sam ranije spomenuo, impedancija zvučnika sastoji se od njegovog otpora i induktivne reaktancije zbog zavojnice žice koja čini glasovnu zavojnicu.

Impedancija se ne može u potpunosti izmjeriti ispitnim mjeračem istosmjerne struje (DC). Na primjer:

Ako koristite digitalni multimetar za očitavanje otpora u Ohmima, izmjerit ćete samo istosmjerni otpor žice.
Da ste imali odgovarajuću opremu i mogli primijeniti AC signal, također biste vidjeli dodatnu količinu otpora.

Zbrajanje oba ova zajedno dala bi stvarnu ukupnu "impedanciju". Isto tako, iste se stvari događaju kada glazbeni signal pokreće zvučnik da proizvede zvuk:pojačalo ili stereo će "vidjeti" opterećenje zvučnika koje je zbroj oba.

Objašnjena matematika otpora i induktivne reaktancije

Za razliku od standardnog otpora, ne možete mu jednostavno dodati induktivnu reaktanciju. Da biste izračunali ukupnu impedanciju zvučnika, trebali biste ih zbrojiti pronalaženjem kvadratnog korijena zbroja kvadrata, koji se ponekad naziva "trigonometrijski zbroj".

Napomena: For the sake up general discussion, we don’t need to know the exact speaker impedance when matching speakers, talking about dB output &power, and so on.

I’m offering this as additional info to help your understanding of where it all comes from.

How does increasing speaker impedance affect power?

As you can see from the diagram I’ve provided above, increasing a speaker’s impedance doesn’t just affect volume (which I’ll cover in more detail below) but power, too. In fact, it can make a big difference in how much power you’ve got on tap with your home or car stereo or amplifier.

That’s because of Ohm’s Law and how power works:

Home &car stereos and amps have a certain amount of voltage they can produce to deliver power to speakers.
According to Ohm’s Law, if you change the resistance (speaker impedance, in this case), the power developed changes accordingly.
Amps and radios have an upper limit to how much voltage they can put out, so the maximum output doesn’t change if you increase the speaker impedance. It’s a fixed limit.
Therefore:if you increase a speaker’s impedance, less power will be developed using the same stereo or amp.

In this example graph, you can see how much power a 4 ohm speaker will develop with the same amplifier as an 8 ohm speaker. The 4 ohm will not only develop 2x the power of the 8 ohm speaker, but the 8 ohm one will never get the full power available from the amp.

That’s important in some cases and less important in others. For example, for home stereos where you don’t need a huge amount of power, you can use 16 ohm speakers in place of 8 ohm ones without noticing that much of a difference.

However, it’s a different case when we talk about car audio as they often need a lot more power to produce great sound or volume in a vehicle – especially with subwoofers for heavy bass. In that case, switching from 4 ohm to 8 ohm speakers means you’ll have 1/2 the power available that you used to.

Does speaker impedance affect volume?

Diagram showing an example graph comparing the dB output volume of an 8 ohm speaker at the same amplifier or stereo output level as a 4 ohm speaker. An 8 ohm speaker will produce less power and volume at the same volume output setting. When the amp is at its maximum output (maximum output voltage), the 4 ohm speaker will have a higher dB output than the 8 ohm at the same level.

In the graph above, you can see what happens when we use an 8 ohm speaker in the place of a 4 ohm speaker connected to the same amplifier. To help keep things equal I’ll compare 4 and 8 ohm speakers with the same sensitivity of 89dB at 1W/1M.

It might seem confusing at first, but what the graph is showing is:

The dB output for the 4 ohm speaker at each amplifier/stereo output voltage that supplies it with 1 watt, 2 watts, 4 watts, and so on. An 8 ohm speaker needs a higher amp or stereo output voltage to get the same power level.
The dB output for an 8 ohm speaker at those same amplifier output level when used in place of a 4Ω speaker.

What this helps show is that when you increase the speaker impedance on a stereo or amplifier designed for a lower speaker impedance, the decibel output (dB, volume) will be lower throughout the full power range.

It can also be a lot less than the correct impedance at the maximum output.

You’ll have to increase the output of the radio or amp to get the same dB volume output for the higher impedance speaker.

This means that:

For a higher impedance speaker, the overall volume will be a few dB lower typically, depending on the particulars of that speaker.
You’ll never get the full capacity out of the stereo or amplifier as you would with a lower impedance speaker like it’s designed for.

For car subwoofers, for example, that’s a big deal. For every doubling of power to a speaker, you’ll get 3dB more volume, not double the volume. 4x the power is 6dB, and so on.

Our ears work in a way such that about 10dB is considered a big difference, which takes about 10x the power. When doubling the speaker impedance, as you can see from the graphs above, you’ll “run out of steam” well before reaching the maximum power your amp could put out like it would with the correct (lower) impedance speaker.

For car stereos with lower power output (most car stereos are limited to about 14-15W or so) that’s especially not ideal.

What happens if I use a higher impedance speaker on a crossover?

What is crossover shift?

Speaker crossovers are designed using predetermined values for the capacitors and inductors they use as filters. When a speaker manufacturer design speaker crossovers, it’s always based on the speaker impedance they’re designed to be used with.

Crossovers behave differently when the speaker load (Ohms load they see) changes. Because of this, when you change the speaker impedance you change the crossover frequency and the sound. The crossover frequency will change – typically a lot.

In other words, changing the speaker impedance will shift the crossover frequency. You may notice several problems after doing this:

A “harsh” sound from woofers or midrange speakers. Tweeters may sound distorted and being to “break up” the sound at volume.
A “thin”, weak quality to the music.
Gaps in the sound ranges you should be hearing.

Speaker crossovers should only be used with the speaker impedance they’re designed for or they won’t sound right.

For example, using a 16 ohm speaker with an 8 Ohm home speaker crossover won’t work correctly. It’ll sound poor and won’t work as designed. You can definitely expect to be disappointed with the sound.

Don’t forget that if your speakers aren’t of the same impedance, the higher one won’t be at the same output level as the correct one, meaning they’re not properly matched.

Do I need to match tweeter and woofer impedances for 2-way speakers?

I don’t recommend mixing speaker impedances in 2-way or 3-way speakers because they won’t have the same volume level once you turn up the volume. That means the sound won’t be right and you’ll be left having to deal with some sound frequencies being poor after a certain point.

As you can see from the graphs I provided earlier, as the power increases the higher impedance speaker will always fall short of the also correctly matched speaker.

In 2-way speaker systems, that an even bigger problem because very often tweeters already have a higher volume output than their woofer or midrange counterparts. To make matters worse, most 2-way speakers have at least crossover they depend on.

This means in many cases changing the speaker Ohm load will also change the crossover behavior and affect the sound negatively.

I’ve seen some speakers systems where one speaker (typically the tweeter) has a different Ohms rating than the others, but in that case the designers take that into account.