Speakers & Amps: The Difference Between 2/4/8/16 Ohms

2 Ohms; minimum load 4Ω; 8-kOhm; 16Ω…when you enter the world of audio amplification, there’s no way around terms like these. They’re often found on the backs of speakers, guitar cabinets and amplifiers, so in this blog, I’ll try to clear up the role of impedance (resistance) and explain what the numbers that go with it actually mean.

What are Ohms?

Electrical resistance is measured in Ohms, which is the basic definition of Ohm’s law. A more comprehensive model might say: ‘the Ohm is the electrical resistance between two points of a homogeneous conductor when, at constant potential difference of 1 Volt, a constant current of 1 ampere is created.’ This results in: resistance = current/current intensity, or R = U/I, where the R stands for resistance, the U stands for current, and the I stands for current intensity in amperes. As you might’ve guessed, Ohms are represented by the Ω symbol.

What does impedance mean when it comes to speakers and amps?

In a nutshell, the lower the number on the amplifier, the more power the amp has to deliver to the speaker. For example, a 350-Watt, 4-Ohm amplifier makes the most of a pair of 4Ω speakers. This means that the headroom increases when the resistance drops, the downside being that the amp will use more energy to perform effectively. Also, be aware that when you daisy-chain, say, multiple passive PA speakers, the impedance is halved, while the load impedance of the amplifier is doubled!

Is there a link between impedance and sound reproduction?

The sound won’t differ much between a 4-Ohm and an 8-Ohm set-up, but if you hook up your 8Ω speakers to a 4Ω amp, you’ll definitely hear a significant difference in loudness. That is, half of what you’d with 4Ω speakers. This makes sense, because if both components run at 4 Ohms, the amplifier is able to perform at maximum capacity while the speakers can make maximum use of that power. That’s why it’s important to properly match up speakers and amplifiers in terms of impedance.

Connecting Speakers in Parallel

So what if you wanted to connect, for instance, a pair of 8Ω speakers in parallel? In that case, you start by calculating the equivalent resistance: 1/Req = 1/R1 + 1/R2 + 1/R₃, etc. As such, a three, 2-Ohm speaker set-up has an equivalent resistance of 0.66 Ohms. Here, you can clearly see that the impedance is lowered, but the amplifier takes on a bigger load. That also means there’s a limit to the amount of speakers that can be hooked up to any given amplifier. While they’re rare, 2Ω speakers for example, often require a second amp to cover the load.

Low-Cost versus High-Cost Amplifiers

Something to keep in mind, is that budget model amps are more likely to run into problems when driving low-impedance speakers (4Ω), which are actually best off with a better, usually more expensive unit. You can rest assured that won’t bump into issues any time soon, and the system is set up to perform at its best. If you are strapped for cash but you still want to build a reliable system, simply go for an 8Ω amplifier and speakers with equal resistance. It’s a commonly used combination that can be shopped across all price ranges.

See Also

» How Many Watts? – The Truth About Speakers and Power Output
» Do I Connect My Microphone To A Speaker?
» The Difference Between Active and Passive Speakers
» Balanced and Unbalanced Connections (Finally) Explained

» Amplifiers
» Speakers
» Speaker Cables
» All Pro Audio Gear

22 responses
  1. Andrew says:

    Hi, I’ve recently purchased a Sony STR-DH190 stereo receiver and I had no idea how complicated selecting speakers to use with it could be. The receiver says 200W 6-16ohms on the back. I want to connect 4 speakers for surround sound but I have no idea what speakers I can use. I’ve read that using the wrong speakers can damage the receiver. Please help me!!!!!!

    • Eelco | Bax Music says:

      Hi Andrew,

      Since the Sony is a HiFi-amplifier and we are Pro Aaudio-specialists, I would recommend contacting a HiFi store and ask for their expertise, they will know for sure what kind of speakers you can connect safely to the Sony.

  2. Terry says:

    I have 4 pa cabinets, I have 1 cabinet with 8ohm speaker and 1 cabinet with 4 ohm speaker each side. How many ohm does each side have, I worked it out to either 6 ohms or 2.7 ohms, can you tell me which is correct

    • Eelco | Bax Music says:

      Hi Terry,

      If you connected these speakers parallel, then 2.7 Ohms on each side is correct.

  3. Paul Andriessen says:

    Hallo ik heb een Denon660 receiver er staat:4 16 ohm ik heb 4 ohm speakers is dit wel goed? of heb ik andere versterker nodig.
    speakers zijn 2ehands dynaudio focus 260 speakers.

    • Eelco | Bax Music says:

      Beste Paul,

      Voor deze apparatuur kun je het beste advies vragen bij een Hifi-specialist.

      Eelco | Bax Music

  4. VR says:

    Thank you for this article, it’s helpful but unfortunately my brain just shuts off and my eyes glaze over upon being bombarded with physics and math. I have a Music Man 210 amp and was wondering what would be best for using with an internal speaker: 4 ohms or 8 ohms?
    Thank you for your help!

    • If I understand correctly, you want to replace the original internal speaker. It’s best to look up to exact model in Google and check the specifications.

      Marnix | Bax Music

  5. Ghiuri says:

    Hello,
    sorry Im new in this, maybe you could give me an advice, please?
    I just bought an Amp /Aiwa 8100 and on the back of the thing says 16ohm.Couldnt find anywhere more info. Lately Ive read anything I could find about amps and speakers. but its still unclear to me what those 16ohms mean and who they refer to – the amp or the required speakers. IF I understand correctly that speakers should have higher impedance than amps. All this stuff is a bit confusing for me. My question/s would be – what speakers should I fit to the amp for a safe match ( I plan to use the setup for music obviously, few hours per day, at a ‘normal’ room level, just simple and clear audition). Second, I do have a pair of wharfedale rated 8 ohm. Would those work ok with the amp? I also have a pair of Yamaha of lower impedance than 8ohm, would be those fine as long volume stays low?. I would very much appreciate if you could givee an answer. Thank you very much.
    Ghiuri

    • Eelco | Bax Music says:

      Hi Ghiuri,

      It looks like the Aiwa 8100 is a HiFi-amplifier, so the technology works a little bit different then the Pro Audio-amplifiers that we usually work with. But as a rule of thumb, the amount of Ohms always pair with an amount of power. For example, 100 Watt @ 8 Ohm impedance. Impedance is the amount of resistance. So if you have 100 Watt @ 8 Ohm amplification, and you connect a 16 Ohm speaker, the resistance is doubled and the amount of power the speaker receives is halved (50 Watt @ 16 Ohm). In your case, if you have an amplifier with a 16 Ohm output and you want to connect an 8 Ohm speaker, the amount of power that the speaker receives is double the amount of power that the amp outputs.

      If possible, I would check the maximum or minimum amount of impedance that your amplifier is capable of handling. Most amplifiers can’t handle impedances below 4 Ohm, for example, or more then 8 or 16 Ohms. Also check the amount of power your amplifier is capable of delivering.

      Then, check the power requirements of the passive speaker you wish to connect. This is usually stated as RMS-rated power, or continuous power. For Pro Audio purposes, we usually recommend that the amplifier can deliver up to 1.5 times the RMS-rated power handling that the speaker requires, or 2 times the power rating if you want to connect a subwoofer. So if you want to connect a Wharfedale speaker that has, for example, an RMS-rating of 100 Watt @ 8 Ohm, we recommend that the amplifier can deliver 150 Watt @ 8 Ohm so that the speaker has enough headroom for higher volumes and cleaner sound.

      Hope this clears it up a little!

  6. Fadi says:

    Hello , I have a Bogen M-600 ( 2 channels 4 ohm / 600W and 8 Ohm / 400W ) 70V/4 ohm MONO / 1200 W. I am using it as a PA system
    question 1: how many 8 ohm / 25W speakers can this take in series ?
    question 2: how many 8 ohm / 50W speakers can this take in serie ?
    question 3 : how many 4W/70V speakers can it take ? can these be combined with any of the two above ?
    Question 4: rule of thumb for question 1 and 2 divide wattage , for example 400W/25W = 16 speakers .
    Thank you so much

    Thank you

    • Eelco | Bax Music says:

      Hi Fadi,

      When connecting in series, anytime you double the impedance, you double the power required. Which means it’s not an effective way to connect many speakers to a single amplifier. You’d be better of using 70V compatible speakers to the 70V output on the amplifier.

      Question 1: You can probably only connect about four 25 W speakers in series to this amplifier.
      Question 2: You can probably only connect about two or three 50 W speakers in series to this amplifier.
      Question 3: In theory, you can connect 300 4 Watt speakers to one 1200 Watt amplifier in 70 Volt. In practise because of the high number of speakers, leaving a little headroom and a little power loss because of all the cables needed, it would be about 270 speakers or less.
      Question 4: The rule of thumb you mentions does work in calculating the amount of speakers you can connect in 100V/70V systems.

      Unfortunately there isn’t a real rule of thumb for 8 Ohm speakers. You just need to calculate the power required. Every speaker you connect in series adds to the impedance and the power required. So let’s say a speaker has 25 Watt @ 8 Ohm power handling. Two speakers will require 50 Watt @ 16 Ohm power.

      If an amplifer delivers 400 Watt @ 8 Ohm impedance, but the impedance rises to 16 Ohm, the amplifier only delivers 200 Watt @ 16 Ohm. And 100 Watt @ 32 Ohm. And so on.

      In other words, if you have 2 8-Ohm speakers connected in series to a 400 Watt @ 8 Ohm amplifer, each speaker receives (400/2)/2=100 Watt. If you have 3 speakers connected, each speaker receives (400/3)/3= 44.4 Watt. And if you connect 4 speakers, each speaker receives (400/4)/4 = 25 Watt.

  7. Vince says:

    hi, I got a pair of speakers at 16 ohms which was used with a McGregor mono double deck, but the McGregor is way to heavy for my son to continue doing mobile DJing, so what size of amp would you suggest to buy for a 16 ohms speakers…..

    • Eelco | Bax Music says:

      Hi Vince,

      Kind of depends on the power that the speakers require. Do you have the RMS power requirements @ 16 Ohm for the speakers on hand? Or at the very least the brand and model of the speakers?

  8. Shem says:

    I have purchased a type D amplifier of 200w with specification 50wx2 + 100w. My question is that can I add with this?
    L/R = 25w x2 4ohm / 25w x2 4ohm

    • Eelco | Bax Music says:

      Hi Shem,

      The x2 and +100 Watt are confusing in this equation. It reads like there are two separate outputs per channel, each with 25 W @ 4 Ohm of power. which isn’t all that much for pro audio purposes.

      If you want to use passive fullrange speakers, we recommend an amplifier that can offer up to 1.5 times the recommended RMS power handling of the speaker, which means that we recommend speakers with a RMS power handling of about 16 Watts @ 4 Ohm. (So 4 speakers total)

      It might however be possible that there is a Bridge modus available on your amplifier, which I can’t check. Which means it might be possible to bridge the outputs so you can connect more powerful speakers. Check the manual of the product to be certain.

  9. Kenny says:

    Many thanks for the speedy reply and advice.

    Do you have anything you would recommend?

    I was hoping to find something in a mini amp version. I’m also confused to where the four sets of speaker wires will go and will it require a switch to play in the two different locations?

    Regards

    kenny

    • Eelco | Bax Music says:

      Hi Kenny,

      I’m afraid we can’t offer any solutions like a mini amp, we mostly deal in full sized PA-amps. I’d recommend going to a HiFi-store if that’s what you are looking for. Usually, these kinds of amplifiers offer a large set of inputs for like TV, radio, CD, DVD, etc. More useful in a home audio setting then a Pro Audio amplifier, to be certain.

      It doesn’t mean we can’t offer any solutions. Amplifiers like the LD Systems DJ 300 2-Channel Amplifier will power your speakers just fine, you just need an external device for playing audio to the amplifier.

      As to how to connect these speakers parallel to an amplifier, take a look at this example. With the before mentioned LD Systems amplifier, you have two red-and-black wire connectors. If we take a look at the rear of your speakers, we see the same red-and-black pairing. On the amplifer, connect the red plug from one channel to the red plug on the first speaker. Then, you connect the black plug on the same first speaker to the red plug on the second speaker. That’s one channel connected.

      You then do the same for the second channel: connect the red plug of channel B of the amplifier to the second red plug on your first speaker. Then, connect the second black plug of that first speaker to the second red plug of the second speaker. That’s both channels connected and all speakers amplified.

      I hope this helps!

  10. Kenny H says:

    Hello, I have purchased a house that has two ceiling speakers, one in the kitchen and one on a small patio. they are Jamo twin tweeter 6.52 DVCA2FG. It says they are 8+8 ohms on the back. My question is, what size amp and specs do I require to use them? No amp was left in the house.
    Many thanks
    Weight (Kg/lb) 1.3 / 2.9
    Tweeter (mm/in) 13 / ½
    Woofer (mm/in) 165 / 6½
    Power Handling (Watts Long/Short Term) 2 x 50 / 2 x 100
    System Type 2-way in-ceiling
    Frequency Response (Hz, +/-3dB) 65-22,000
    Impedance 8+8 Ohm
    Sensitivity (dB, 2.8V/1m) 89

    • Eelco | Bax Music says:

      Hi Kenny,

      Each unit has two speakers of 8 Ohm with a load capacity of 50 Watt’s RMS, so we recommend an amplifier with two outputs with about 75 Watt @ 8 Ohm of power. You can also run the speakers in 4 Ohm and connect them parallel to an amplifier with two outputs of 150 W @ 4 Ohm. This way, you can connect both your ceiling speakers to a single amp.

  11. John P Gudge says:

    I have a pair of 150w RMS speakers at 4 ohms, and a small 6 channel 300w RMS powered mixer at 6 ohms. Would they be compatible?

    • Eelco | Bax Music says:

      Hi John,

      Unfortunately, probably not. If you deliver 300 Watt power @ 6 Ohm to a 4 Ohm speaker, the speaker will receive about 400 Watt, which is way higher then the recommended 225 Watt @ 4 Ohm we would recommend. It could be that the speakers can handle this amount of power no problem, but you’ll need to check the specifications with the manufacturer.

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