Speaker Impedence

I have a bit of a novice question I have been thinking about. If you had speakers capable of 4 or 8 ohms and an amplifier with plenty of headroom, would you run 4 ohm? Is there any reason not too and would it improve sound?

I get that lower impedence means the amp is going to be required to use much more power, I am just not sure if it makes any audible difference or if I should mess with it.

I have heard my Canton speakers are "power hungry" but I also have an amp that would have no issues with whatever I throw at it. Currently running 8 ohm but curious

 

Speakers don't really have a single impedance. They have a characteristic impedance curve, with the effective impedance varying by frequency. They speaker designer will usually attempt to state an "average" impedance, or to locate the frequency at which the speaker is most difficult to drive and then state the impedance at that frequency.

If you're using a tube amp, I'd try both the 4-ohm and 8-ohm taps and use whichever you think sounds better. If a solid state amp then there usually aren't multiple taps (or even any output transformers), so you simply want an amp that can handle the speaker's minimum impedance -- at whichever frequency it occurs -- without being overdriven.

 

Well my amp is solid state but also has 4, 6 and 8 ohm connections

 

Is this the Mcintosh MC452 in your profile? I believe some of those do have autoformers to adapt to differing speaker loads, allowing for the minimum distortion.

 

Yep

 

If this helps: the nominal impedance of a loudspeaker is traditionally specified as the lowest impedance in the impedance curve within all frequencies above the resonant frequency.

 

Without going into a lot of technical detail, you should always make connections at the taps for that for which the speaker is "rated".

That way, you will ensure the maximum amount of distortion free power from a McIntosh amplifier.

Connecting an 8 ohm speaker at the 4 ohm tap will significantly reduce the maximum available power of which the amplifier is capable. Connection of an 8 ohm loudspeaker at the 16 ohm tap will - theoretically - double the output power - but it will be much more taxing on the amplifier and run hotter.

Stay with the correct taps and you'll be fine.

Thanks.

 

While I agree with 62caddy, I would also be a bit more willing than he is to play around with a load and not just do things by the book. As has been stated upthread, a speaker's impedance will vary with frequency. It also can be mis-spec'd. I've run into speakers the manufacturer rated at 8 ohms that seemed to me to be closer to 4. They certainly had that affect on my amp, causing it to run hot. By hooking up a speaker to the "wrong" tap, it can cause your system to sound different. It might even sound better.

As long as your amp runs cool, you aren't going to harm it by running your speakers on the other taps. If the amp gets too warm, stop the experiment.

 

I appreciate the feedback guys, but I am still confused. Allow me to elaborate. My speakers say they can be hooked up anywhere from 4 - 8 Ohms. I have always stuck with 8, as it is more conventional and I obviously don't know much about it. So, my question still stands. If the speakers say they handle 4 - 8 ohms, which I take to mean I could user either tap, which one should I use, and would one in theory sound better?

My speakers show 4..8 nominal impedence here http://www.canton.de/en/produkte/gle-490.2

 

Try both and let us know which is best.

 

FWIW, although the article's in German, there's a plot for the impedance curve of the OP's speakers here (if those are the speakers listed in the OPs profile): http://www.audio.de/testbericht/test-standboxen-canton-gle-490-2-1146058.html

Looks like the speakers bottom out close to 3 ohms for two octaves from the lower bass to upper midrange and peaks of 12-15 ohms in the low bass if I'm reading the chart correctly.

I'd try the 4 and try the 8 ohm taps but I'd guess 8 is the best compromise.

 

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I think you are misinterpreting the concept of impedance. Speakers do not "handle" impedance; impedance is what it is and the current and voltage will be dictated by Ohm's Law as a function of wattage - and impedance.

It is the amplifier that either can or cannot "handle" a given level of load - not the speaker. The speaker IS the load.

Loudspeaker impedance can and often does fluctuate across the frequency range. However it is best to choose the taps than come closest to the impedance - most of the time. While sometimes it may fall below the nominal rating, the best tradeoff is to use the rating given by the speaker manufacturer in selecting the impedance taps of a McIntosh amplifier.

I believe McIntosh recommends the 8 ohm taps for speakers as little as 6.5 ohm. Unless the speakers spend a considerable amount of time significantly below that, you should probably use the 8 ohm taps. As I mentioned earlier, connection of 8 ohm load at 4 ohm tap will reduce the maximum available power.

In any case, I would not recommend using the 16 ohm taps with any 8 ohm speaker and I highly doubt McIntosh would either. You probably won't harm the amplifier even if you did - McIntosh is robustly built, but why needlessly take chances for a sonic improvement that in all likelihood that is negligible at best?

 

Check this review, which has an impedance curve.

http://img2.audio.de/Canton-GLE-490-2-f960x960-ffffff-C-ac9a954e-71286854.jpg

Looks like the impedance drops down to 3 ohms at its lowest. That dip is where your amp will have the most difficulty controlling the drivers. I would go with 4 and not look back.

(I'm guessing that green is phase and black is impedance. Any German speakers can help sort this.)

 

So he won't be getting all 450 watts from his MC452, in other words? He might have to slum it with 350 watts?

I've heard stories of people preferring different taps of the vintage Mc amps regardless of their speaker's actual impedance, but I have a feeling that with that vintage of amp its not going to make much of a difference sonically. I've never played with any of the other taps on any of my Mc amps.

 

I had some 6.7 Ohm nominal speakers for years. Always went back to the 4 ohm output on my 30-watt tube amp. Not as punchy, but the detail was much improved.

 

I doubt the question of vintage or modern would have any bearing. The principles of impedance matching to amplifier output should remain the same.

I cannot comment on how much output would be lost by using the 4 ohm taps in the OPs situation - and certainly not without knowing what the exact impedance is - which as we all know is variable.

Personally I would not want sacrifice any more than is absolutely necessary for safe operation.

These are all outlier scenarios in the final analysis: You'd really have to try to have a load related issue in the real world of listening under ordinary listening conditions - when taps are matched to "rated" or "nominal" speaker impedance as given by the vast majority of loudspeaker manufacturers.

 

Two people have posted a link to a chart for this particular speaker.

 

Unfortunately, the curve cannot tell us what particular frequency(ies) are actually present in the material (or output), duration, relative dB level, etc etc etc...

Again, 4 ohm cannot hurt...

 

Out of curiosity, does anyone know what impedance is actually seen by the amplifier by a complex musical signal of many thousands of frequencies from all different portions of the audio spectrum - simultaneously?

 

There is a measurement method that uses broad-spectrum noise vs. a sweep and FFT. The results are reportedly similar in terms of graphing the impedance curve.

 

Well sure, but vintage amps often sound different. I think the bottom line here that I was trying to convey is he'll either like the 4 ohm taps better or he won't, as you say the 4 ohm taps won't hurt anything. I think this is a common thing owners of autoformer amps go through when they discover their speakers might not be 100% 8 ohm at all times, I know I did. I just never followed through .

 

The key phrase from the above reviews is:

Impedanz benötigt stabile Amps

which means that the impedance response (the black line in the plot) demands a stable amplifier (implied into low impedances). The impedance plot is seldom at 8 ohms, and only goes a little bit higher in a few places, so this definitely looks more like a 4-5 ohm nominal speaker.

It is bizarre that they quote the impedance as 4...8 ohms. Maybe they mean 4.8 ohms, which would seem reasonable based on the impedance curve, but it certainly does not look like an 8 ohm speaker.

 

No, but it's recorded music, so you know, with most of it there's not huge amounts of information going on below 30-40 Hz (unless you're listening to music with lots of orchestral bass drum, or lots of pipe organ music, or some modern stuff w/ low synth) -- where those speakers have their big impedance rises -- and above about 5 or 6 kHz you're pretty much talking about high harmonics with decreasing amplitudes. For those speakers, w/ what look like 3 ohm impedance from around A 440Hz to two octaves below it, I guess there's a lot of musical info always going on there at pretty substantial amplitudes, so it may well be that 4 ohms will work out well. But if you're playing something loud with lots of low bass, those peaks might make you want to try it at 8 ohms. I'd just try 'em both ways myself.

 

The green plot shows as high as 20 and above 10 for much of the important midrange portion of the spectrum. It's quite a quandary.

If the black plot is more relevant, I'd have concur that the 4 ohm taps would probably be more appropriate.

Google did not translate the page for me unfortunately.

In any case, the 8 ohm tap would actually yield more power - if the actual load were closer to 4 with these loudspeakers - but it would run hotter. However an MC 452 is an amplifier of superb quality and worst that could happen is the Sentry Monitor would trip should heat get out of hand.

 

Interesting find here guys....damn, I want my speaker upgrade....soon!
http://www.avsforum.com/forum/89-speakers/1481124-canton-speakers-impedance-question.html

I think I may experiment with the 4 Ohm taps