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What are the benefits of 4 ohm speakers?

Discussion in 'Audio Hardware' started by Henry J, Apr 27, 2021.

  1. SandAndGlass

    SandAndGlass Twilight Forum Resident

    I don't think that I am quite understand the points you are making?

    Well yes... I was merely pointing out the factors that are being influenced by a speakers impedance and sensitivity.

    You would of course, need to match an amp with at least its mininum electrical requirements.

    I don't believe that I made any statements to the contrary? How much speaker and power you will need will certainly be determined at a minimum by the size and construction of the room.

    Although the sensitivity of the speaker and the type of music being played will certainly play a significant part.

    OK... Back in 2012, I bought a high current 250-Watt stereo amp for my front mains. I bought their (Emotiva) stereo amp that had more power than the speakers I was driving at the time. It that particular model had the largest power supply of any of their amps, with the exception of their monoblocks.

    It could deliver 400-WPC in 4-Ohms. I bought it because it had enough power to drive any speakers I might buy in the future. This power amp has performed flawlessly all of these years and has driven power hungry speakers like the Polk RTiA9's and the Polk LSiM707's, in both stereo mode and for HT. This amp can flat out crank.
     
    Khorn likes this.
  2. Sorry @SandAndGlass I’m speaking in generalities none directed directly at you. It’s obvious to anyone that’s even been here a short time that you certainly are deeply knowledgeable on the subject and know what you’re talking about.
     
    SandAndGlass and trd like this.
  3. SandAndGlass

    SandAndGlass Twilight Forum Resident

    Impedance is the sum of all reactances in an AC RCL circuit. A reactance is the characteristic of a component to oppose changes in an AC electric circuit. This is a figure which changes in value, according to the frequency of an AC circuit.

    XC denotes Capacitance Reactance. It is greatest at low frequencies. This is why a capacitor is used to pass an AC signal at high frequencies, like to a tweeter in a crossover network. A capacitor stores voltage and opposes changes in voltage.

    XL denotes Inductance Reactance, an inductor is at its simplest, a coil of wire. When you pass an AC current through a coil of wire, it creates a magnetic field which expands and contracts across the other coils of wire in the same coil. This magnetic field allows the coil to store and release electric energy. An inductor acts mainly to resist changes in current and this opposition is strongest at high frequencies. This is why inductors are used to pass low frequencies in crossover networks.

    Cone style speakers rely on a voice coil and a magnet to generate mechanical motion of the cone, when an AC current is passed through the voice coil. Because of this, the primary reactance in a speaker is Inductance, which is why a speaker has Inductance Reactance.

    It is because the value of this Inductance Reactance changes with frequency, that the impedance curve of a speaker changes according to frequency. Think of impedance as sort of the resistance in an AC circuit.

    When we refer to a speaker as an 8-Ohm speaker, what were are really saying is that although this value will change with frequency, the average value is around 8-Ohms.

    As we can see in my post about amplifier power output at four and eight Ohms, we see that an amplifier, in theory, will deliver twice as much power with a 4-Ohm load as with an 8-Ohm load.

    Now, since a speaker represents an inductive load to an amplifier, the amplifiers power output changes with frequency. As the amplifiers power output increases or decreases across the range of audio frequencies, this changes the volume level of sound across these frequencies.

    This is why a speakers response curve is not flat. And why no conventional speaker can or will yield an accurate reproduction of music. These are one reason that speaker's will measure and sound different from each other.
     
    rischa and Khorn like this.
  4. SandAndGlass

    SandAndGlass Twilight Forum Resident

    No, no offense taken at all. Since you had quoted me in specific, I was just not understanding the questions you had or the points that you were trying to get across to me. :wave:

    I was simply attempting to provide a better explanation.
     
    trd and Khorn like this.
  5. Ontheone

    Ontheone Poorly Understood Member

    Location:
    Indianapolis
    Spoken like a guy who only deals with speakers, not amps. You can't ignore the amp when considering a speaker - there's always an amp.
     
  6. SandAndGlass

    SandAndGlass Twilight Forum Resident

    The owner of Tekton has some unusual views on things...
     
    Ontheone likes this.
  7. avanti1960

    avanti1960 Forum Resident

    Location:
    Chicago metro, USA
    with a good amplifier the output will be doubled vs. an 8 ohm nominal speaker- allowing the use of more power and current. harder to drive but potentially rewarding.
     
  8. Henry J

    Henry J Forum Resident Thread Starter

    Location:
    Asbury Park, NJ
    And that was my my whole point in asking this question.
    "Possibly" better was my thought and seems to be the consensus.
    "Possibly" over work an amp also!!

    I have greater understanding of the how 4 ohm speakers works now, but still no real reason why someone would seek out a 4 ohm speaker.
     
  9. Ontheone

    Ontheone Poorly Understood Member

    Location:
    Indianapolis
    I don't think that's a defining criteria of a "good amplifier", at least not in the world of tube amps. Tube amps generally have an impedance matching output transformer because tubes are inherently a high voltage, high impedance, low current device, and speakers need low voltage, low impedance, high current supplies. Therefore they simply employ a a transformer. With a transformer, you have the advantage of being able to take multiple outputs at different winding ratios to get the output voltage that you need. It's common to see amps with 4, 8, and 16 ohm options (like my Line Magnetic 805ia). Each corresponds to a different transformer tap, and all are capable of the same nominal output power.

    If you use something other than the rated load impedance, a tube amp will deliver less output power, exhibit more distortion, or both. It's not because it's a "bad amplifier".
     
    SandAndGlass likes this.
  10. SandAndGlass

    SandAndGlass Twilight Forum Resident

    I don't think there would be a reason to seek out a 4-Ohm speaker in specific.

    Being a 4-Ohm speaker does not grant it any super powers, nor, contrary to Reverend Tekton, does it mean that the industry wide standard 8-Ohm speaker is in any way obsolete.
     
    The Pinhead likes this.
  11. Ripblade

    Ripblade Forum Resident

    Location:
    The Six
    Such an amp will need to double it's 4ohm power into 2ohms. Not easy or cheap...or easy to carry around. The 4ohm coil could produce a smoother impedance curve owing to lower inductance, but as any Maggie owner will tell you, smooth or not, 4ohms needs power....lots of it. Of course one way around that it to use lots of higher efficiency drivers to improve sensitivity and reduce power needs, as Tekton does. For a lot of other speakers it will come down to how well the amp doubles its power into 2ohms.
     
  12. head_unit

    head_unit Forum Resident

    Location:
    Los Angeles CA USA
    Speaker impedance is way more complex than that, however from an engineering point of view having a lower impedance makes it easier to achieve more performance in a given box size. For instance, the ohms are in the bottom of the equation governing efficiency. That doesn't mean 4 ohm speakers are automatically twice as efficient as 8 ohm due to other factors but it helps. That's why you rarely see designs like the Devore Orangutan O/96. Rated 10 ohms, confirmed by Stereophile, pretty big box is a price you pay for that.
     
    The FRiNgE and Henry J like this.
  13. Henry J

    Henry J Forum Resident Thread Starter

    Location:
    Asbury Park, NJ
    That makes sense.
    A benefit for the manufacturer, not necessarily the end user.
     
  14. Helom

    Helom Forum member

    Location:
    U.S.
    There is no good reason to seek out a 4 ohm speaker unless you simply want a driver that can take more power, and potentially (key word) play louder. The Tekton video proves just that, though I think his intention was to insinuate that 4 ohm drivers sound better. They don’t. They would possibly be more dynamic if considered in a vacuum, but they have air and amplifier coupling that come into play. It might be worth seeking out a 4 ohm subwoofer, but the spec often isn’t included by sub manufacturers since the amplifier is built-in.

    I have a pattern of gravitating toward speakers with 8 ohm and higher impedances. But I’ve heard good 4-ohm nominal designs also. It’s mostly a meaningless spec unless one is wanting to use low-power tube amps. It’s not as though a 4ohm driver results in greater detail or resolution.

    Folks should pick a speaker based on how it sounds to them, with their chosen ancillaries. That’s it. No need to overthink these things.
     
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  15. tumbleweed

    tumbleweed El brujo del audio

    Location:
    Colorado foothills
    Hm, don't think that's what I was taught. The tech guys in the dealer/manufacturer info classes I've been to would say that with a proper amp/power supply/what have you, there would be less variation from 8 to 4 ohms*. Somebody tech-y correct me if I'm misremembering.

    *Perhaps not true for tube equipment.
     
    The FRiNgE likes this.
  16. The FRiNgE

    The FRiNgE Forum Resident

    From a speaker builder/ hobbyist, a 4 ohm speaker has lower inductance vs an 8 ohm, and lower back EMF. The back EMF is an oft ignored effect on sound reproduction... the less of it we have, the more pure the signal delivered to the transducer. (the driver) Lower inductance (lower reactance) becomes more important in tweeter response and phase angle.

    There is a lot of science to this, the benefit of a 4 ohm voice coil vs 8 ohm, better electrical damping, comparably tighter bass control, how fast a driver stops without ringing effects, more controlled reactance, etc. Speaker are highly reactive animals. An 8 ohm speaker for example can swing as high as 20 ohms or more at resonance to less than 4 ohms at 20kHz.... but rated at 8 ohms!
     
    Last edited: May 5, 2021
  17. motorstereo

    motorstereo Forum Resident

    Location:
    Ct.
    Another thing to keep in mind with a 4ohm speakers is don't try bridging them with amps that aren't capable of running a 2 ohm load as bridging an amp causes it see only half the impedance. 2ohms aren't an issue for the big autoformer Mcintosh amps but could be a problem with amps that aren't up to the task. In my case it was a pair of 4ohm Boston Acoustic ba400's paired with bridged Hafler dh220s that filled my room with smoke many years ago.
     
    SandAndGlass likes this.
  18. SandAndGlass

    SandAndGlass Twilight Forum Resident

    From a previous quote from myself:

    Any time you go from an 8-Ohm load on an amp to a 4-Ohm load, the load on the amp will cause twice as much current to flow, in theory. The words "in theory" are used because that is how Ohms Law describes the properties of electricity.

    This will, in theory, double the output power of the amp, making the amp work twice as hard.

    This is because, electrical theory and real world amp design are two different things.

    If a manufacture builds an amp that is designed to drive an 8-Ohm speaker at 100-Watts, the amp must contain a power supply which will be capable of delivering a minimum of 100-Watts.

    That does not mean that the physical power supply itself will, by some magical means, suddenly be able to produce 200-Watts just because you connect a 4-Ohm speaker up to the amp.

    Which is why a SS amp will state the amount of power it can actually deliver at both 4 and 8 Ohms, in the specifications (if the amp is rated at 4-Ohms at all).

    As previously mentioned by Onetheone, with regard to a tube amp. A tube amp converts voltage from the tube(s) to current for the speakers through the use of an output transformer. The transformer uses taps on its secondary windings to provide the same amount of power to either a 4 or 8 Ohm load.

     
    Ontheone likes this.
  19. rischa

    rischa Where'd Dizzy go?

    Location:
    Madison, WI
    I've read that some 4 Ohm taps are little more than protection circuits to keep your low-impedance speakers from blowing, or maybe to keep your amp from over-heating (can't remember which). Is there any truth to this?
     
    Last edited: May 5, 2021
  20. SandAndGlass

    SandAndGlass Twilight Forum Resident

    This is a very important point that I wanted to bring up. While many class A/B amps are capable of running in 4-Ohms, practically none can operate into 2-Ohms.

    For example, my generation one Emotiva power amp is a 250-Watt amp into 8-Ohms. It can deliver an impressive 400-Watts into 4-Ohms. But that is no where near the 1,000-Watts that it would be required to deliver into a 2-Ohm load. This would be 4x its rated 8-Ohm power!

    When you bridge an amp, each half of the amp is only seeing half of the sine wave. If you attempt to run a 4-Ohm load. Each half of the amp is seeing half of the 4-Ohms, which is two ohms.
     
    motorstereo likes this.
  21. Helom

    Helom Forum member

    Location:
    U.S.
    It’s to protect the amp from going up in smoke at the expense of frying the drivers instead. An amp manufacturer cares more about its product’s failure rate than they do your speakers.
     
  22. SandAndGlass

    SandAndGlass Twilight Forum Resident

    I wouldn't know about "some" amps...

    But, because a tube amplifier uses an output transformer, it has taps in the secondary windings. This will specifically match the corresponding impedance and deliver the amps full rated power at that level of impedance.

    The difference between 4 and 8 Ohms is only a difference in where the transformer tap is made. The amp doesn't care that you are using a lower impedance speaker.
     
  23. I was under the impression that most SS amps with good power supplies provide double the rated output when halving the impedance. The one I’m getting is rated at 200w 400w and 800w into 8 4 and 2 ohms respectively. Seems to me these are fairly common specs.
     
  24. SandAndGlass

    SandAndGlass Twilight Forum Resident

    No, they are not common specs at all. Which I was assuming why you were choosing that amp in particular to begin with.

    Your amp is a deliberately overbuilt amp that was designed to be able to deliver the power and the high current levels that you describe.

    Most AV receivers in the $800 and under price range are rated somewhere around the 100-Watt range and are designed to operate with standard 8-Ohm speakers only. They are not even rated to use 4-Ohm speakers.

    Over building the power supply and other features of an amp increases the cost of the amp. That is the reason that companies supply specifications for their products. This way, the consumer can select the amp that has the specifications that meet a particular consumers needs.

    The largest portion of the home speaker market today is focused on tower speakers that will have a primary use in home theater. As such these speakers will typically be 8-Ohm speakers. Because, that is what most of the AV receivers are designed to drive.
     
  25. I guess except for McIntosh, most of the amps I was considering had 2, 4, 8 and even rarely 1 ohm power ratings that doubled. It’s just good “insurance” to have.
     

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