Impeadance question

[fudgemik]

most amps give a 8 and 4 ohm stereo rating... 4 ohm being almost double in some cases but always more power....with that being said i am curious of distortion, i have been told that the higher the impeadance the less distortion.... so a pair of 8 ohm speakers will be less distortion than a pair of 4 ohm,,,,/?? is it audible or is it a number on paper?

[MikeyBC]

A pair of 8 ohm speakers will be an easier load for most amps by drawing less current from the amp. On a lesser amp, a low impedance speaker may try to draw levels of current that the amp is not capable of doing comfortably and therefore may cause an increase in distortion. On a competently designed amp with a decent power supply it wont really matter what impedance your speakers are.

[SpankingVanillaice]

Now I found out that its for both headphones and speakers so thats cool.

[SpankingVanillaice]

I always thought that the higher the ohms the more clear it will be too but I thought that was for headphones only.

[kexodusc]

Impedance (ohms) is not a measure of how clear or how much distortion the sound has. Some of the best speakers ever made were 4 ohms or lower. Sound quality and impedance aren't related as such.

[Florian]

There are high sensitivity speakers which usually share a easy impedance like 8ohms 12ohms or higher. There are others which go as low as 1ohm. Good amps generallly can handle 4 or lower. All my amps here can run with 2ohm and 1 can run 1ohm with no problems. The amps have to be stable and be able to deliver the current when it counts.

-Flo

[speakeroligist_38]

Fudge look at it this way. An amp rated say 100 watts rms from 20-20k at .08 distortion will have a higher rate of distortion at lower impedences. In other words, an amp will produce more power at lower impedances but the downside is that the amp will also create more distortion generally due to heat. For example, above I said an amp rated at 100 watts rms into an 8ohm load with .08% distortion will have a spec like 175 watts rms into a 4ohm load with .16% distortion or 225 watts rms into a 2ohm load with .46% distortion. You see ach time impedence is lowered power increases but so does the distortion level which can create real problems for some speakers(voice coils) and receivers/amps. Basically, lower impedences generally require more current and more current translates to more heat which is what causes most not all distortion problems. Some high efficiency amps such as the class D amps are able to handle extremely low impedence loads but generally are mono block type or 2channel amps that have been bridged to low impedences. This has a lot to do with wiring speakers in series or series parrellel, and etc. Anyways, hope this helps.
Phil

[Florian]

Or you can buy some real amps build for only one purpose. Drive all loads with power and finesse. Like the Krell KSA-250's, KRS, 200's and 400's etc..Also the big Sphinxes do this with no problem.

I agree with the above poster but there are amps that laugh at 1ohm loads and have lower distortion than many amps with 4 or higher ohms driveability.

Anyways, choose a amp that matches your speakers and pocket book.

[kexodusc]

Hey Phil...how did you arrive at the conclusion that distortion numbers increase as impedance decreases? There really shouldn't be any introduction of distortion to the signal within the amplifier's design limits, regardless of impedance.
For all intents and purposes, distortion figures below 1% are effectively inaudible and not substantial anyway. Of all the specs given, this one is usually the least useful in determining what the performance of a unit might be. In fact, some data suggests that figure is much higher, as high as 2 to 5%. A lot of great, legendary tube amps have higher distortion figures.

[fudgemik]

i learn something in here every day, thanks................

[speakeroligist_38]

Very true there Kex but with respect to certain frequencies higher distortion levels can produce some noise that is audible. Not much of a concern as far as the lower octaves but more in the mid and high frequencies. Sure, a good quality component amp when designed to drive loads with lower impedences this is not much of a concern. Of course, assuming you have a good power supply w/o any major fluctuations in voltage. For example, if voltage drops significantly an amp (especially one driving a 2 or 1 ohm load) will over compensate (react) to the voltage drop by trying to pull more current. This creates two problems, more current=more heat(distortion) and as a result can really heat up a speakers voice coil. If not addressed, sooner or later but let me emphasize the sooner part something gives. In most cases the speaker(s) voice coil will burn up and some components in the signal path (amp circuit board) can also burn up. Clipping is another way this can happen but see no need to discuss it here. Anyways, Kex you know I am no expert but do know a little about what I am saying here.
Phil

[kexodusc]

Anyways, Kex you know I am no expert but do know a little about what I am saying here.
Phil

I'm not expert either, discussing these things is how we learn.

For example, if voltage drops significantly an amp (especially one driving a 2 or 1 ohm load) will over compensate (react) to the voltage drop by trying to pull more current. This creates two problems, more current=more heat(distortion) and as a result can really heat up a speakers voice coil.

I see what you're saying here, the theory is fine. The practical application though is that most amps will handle 4 ohm loads quite well without distortion of anything significant, provied they remain within the design capacities (ie: not over driven), the distortion from an amp should be the same regardless of 8 or 4 ohm loads. Lower impedance speakers are usually designed to accept more current and compensate for any thermal dissipation problems. Even in a 4 ohm load, you'd need to deliver a lot of power to fry most speakers. Even cheap sony amps can power 4 ohm loads to a point. And play quite clean and loud. I'd rather an efficient 4 ohm nominal speaker than an inefficient 8 ohm speaker. It's all relative. But yeah, as you increase the current you put more stress on the amplifier, you'll overdrive it sooner with lower impedance.