Explain Ohms to me.

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  • 02-26-2004, 07:00 AM
    kexodusc
    Explain Ohms to me.
    I've been around audio equipment for almost 10 years now, I've never had someone adequately explain to me the impact that resistance has on output.
    I think most of my audio equipment has only ever run at 8 ohms, I've never changed that setting... What is the advantage or disadvantage to running at 6 ohms, 4 ohms, etc? Any sound quality issues? Do you consume more electricity as the ohms decrease?
    The power effectively doubles, right? Does this just give you more volume?
    What gives?
    Please help...maybe Terrence or Wooch with their great 500 word explanations?
  • 02-26-2004, 12:18 PM
    kelsci
    Quote:

    Originally Posted by kexodusc
    I've been around audio equipment for almost 10 years now, I've never had someone adequately explain to me the impact that resistance has on output.
    I think most of my audio equipment has only ever run at 8 ohms, I've never changed that setting... What is the advantage or disadvantage to running at 6 ohms, 4 ohms, etc? Any sound quality issues? Do you consume more electricity as the ohms decrease?
    The power effectively doubles, right? Does this just give you more volume?
    What gives?
    Please help...maybe Terrence or Wooch with their great 500 word explanations?

    Kexodusc: I pulled this off Encarta but left the definition simple.
    Resistance (electricity), property of any object or substance to resist or oppose the flow of an electrical current. Ohms involve more than the output of an receiver. There are resistance devices called RESISTORS that are used in just about any electronic device on the chassis in the formation of the performance of various circuits.

    There are some receivers that are capable of handling speaker loads in ohms as low as 2ohms. Others say only to use 6 or 8 ohm speakers or higher. I have read in the testing of speakers that a speaker could be rated 8 ohms and yet be variable enough while playing to dip into lower ohms or rise to higher ohms depending on the frequencies that are playing in the speakers from the receiver and its source material. I look at this differently. I take a VTVM, set it to ohms, and stick the testing wires of that meter into the positve and negative connectors that you would normally put your speaker wire cable in. I have had speakers that claimed there NOMINAL impedance was 8 ohms, but I would get readings as low as 4 ohms or perhaps as high as 7.2. If you have ever took a speaker apart meaning ripping out the paper cone, you will see wire wrapped around the bottom of the paper cone. If you measure the two ends of that wire, you will get nearly or exactly the same readings as what I described above. This reading is called the D.C. resistance. This is the reading I am concerned with. If I did not take these DC resistance readings into consideration, the 5 channel passive Dynaquad system I possess would not work properly. As far as power goes, some receivers,amps, etc. can be very flaky on what they deliver at 4, 6, or 8 ohms. Theortically, the lower the ohms, the higher the power the receiver etc should deliver to the speaker. Some units that can power 4 ohms may in fact deliver less power. Some are not recommended to push any 4 ohm speakers which could short out the amp. The lower the ohms go, you are offering less resistance. If the resistance was 0, you would have a short. As for sound quality, I have found 4 ohm speakers to be more bassy and their sound not as clean as higher ohm speakers. Years ago when I read test reports on two channel equipment, distortion was higher from the receiver-amp at the lower ohms delivery level. My general rule of thumb; the higher the ohms, the cleaner and tighter the bass response gets and the higher frequencies are also cleaner. If you have a satellite system, the center and 4 or 5 satellites used IMO should be measureing nearly the same DC resistance on each one. That is part of what I call the CONSISTENCY of those speakers to deliver a more cohesive sound field.
  • 02-26-2004, 09:05 PM
    spacedeckman
    Where theory falls short in realityville
    According to the strict laws of physics, when a speaker's impedance is halved (eg: 8 to 4 ohms), the current demand doubles, making the amplifier work harder, but doubling the output power (eg: 50 to 100 watts). Before you get all excited....this is actually impossible due to resistances in the circuit itself, and the only amplifiers that come close tend to be a bit on the pricy side of things. In reality, the amplifier WANTS to double it's output, but due to the circuit impedance and lack of available current from the power supply, falls far short of that goal. Many will actually overheat and shut down at very modest power demands into a 4 ohm load. So, trying to buy the best quality amplifier is a much better decision than buying the most watts per dollar for your given budget.

    On the speaker front, an 8 ohm speaker is only an 8 ohm speaker on paper. It's impedance will change depending on input. Some speakers change more than others, and some manufacturers "fudge" the ratings more than others. There is an "official" standard that is recommended, but many manufacturers merely give it a nod and just kind of give the speaker in question an "eyeball average" looking at how low the impedance goes, for how long, and at what frequencies. It isn't uncommon for an 8 ohm speaker to be at 4 ohms at certain frequencies, some will even present a 64 ohm load at some other point in the frequency spectrum. Many of the modern speakers sold to mass market and entry level "mid-fi" customers have had the speaker loads "dummied down" so they present a very mild challenge to an amplifier. This is done because many modern receivers are incapable of dealing with any difficult loads without shutting down. If done improperly, this can negatively affect the sound of a speaker. If done properly, it should have little effect at all.

    So, is a 4 ohm speaker better than an 8 ohm speaker? No. Just be aware that some of the older 4 ohm speakers, and some of the higher end 4 ohm speakers can present a fairly complex load to an amplifier. You are expected to buy an amplifier that is capable of driving them should they be your choice. In the old days, most amplifiers were capable of doing that, today, it is left to the chosen few...but there are still quite a few.

    A 6 ohm speaker is one that a manufacturer doesn't really feel comfortable rating as an 8 ohm speaker, but feels is not demanding enough to be labeled a 4 ohm speaker.

    Hope this helps. Just remember quality over quantity and you will do fine.
  • 02-26-2004, 10:32 PM
    92135011
    Well, I found the easiest way was to think about it like this: a river

    As you know, current is the flow of electrons. Let's picture the electrons as water. What makes the water go forward? Well in a river, its just the gravity the pulls the water toward the ocean. If the river had rocks, then water would have an easier time flowing, whereas if it were clear, it might have more trouble. Same with resistance.

    Water = current
    gravity = voltage
    rocks = resistance

    This is usually a classical way of describing voltage, current and resistance in a concrete way.

    Now, lets picture a turbine at the end of the river. What drives the turbine? the water right? Ultimately, the rocks take away some of the energy of the water flowing down by slowing it down. So if it travels slower, then your turbine would turn slower and hence produce less electricity in the same amount of time as if there was turning fast. Same thing works for your speakers and amp. However, the extra thing is that electrons rub against the metal wire when they travel through. The effect is quite much like rubbing your hands together. You get heat.

    Some side effects of heat are that your transformer, which most times has wax in them (forgot what it does). Waxes are pretty good against heat since they have a long saturated fatty acid chains, but they do melt.

    Also, the capacitors are used with the transformer to convert your inconsistant voltage from your power socket to pretty constant flat-line DC current. However, as your current rises, the capacitors must discharge more current at a time. They too do heat up and will blow up if too much is applied (I've seen this happen numerous times and its quite entertaining).

    Finally, your ICs. IC's are very sensitive to changes in changes in power. Due to their small nature, they do not dissipate heat very well, burning them arent that hard. Also, ICs are very sensitive to voltage changes. Anything above 5v will burn them out. So the advice here is to NEVER touch them. Your body acts as a large capacitor due to its large surface area and you can actually generate more than 10000 volts, and will burn them out in an instant.

    At this point im rambling -.- sorry
    bye
  • 02-27-2004, 04:59 AM
    kexodusc
    That helped alot.
    You folks are very kind to take time to attempt to explain this to me.
    Thanks guys.
  • 02-27-2004, 08:47 AM
    Monstrous Mike
    Quote:

    Originally Posted by kexodusc
    That helped alot.
    You folks are very kind to take time to attempt to explain this to me.
    Thanks guys.

    This site might help you a bit: http://www.rocketroberts.com/techart/spkr.htm