Does impedance matter?


In all my post readings, the #1 question category is the 'Does It Match' question. This is usually addressed as a speaker / amp question.
Most responders start with impedance.
Of all the things to look for in a speaker impedance is down the list. I have looked at at many speakers measured by reputable testers. 8ohm 'nominal'? These guys are all over the place from 3ohm in mid frequencies to 20 ohms+ at resonance. Some are 4 or 5 ohms from 200hz to 1khz...prime musical turf.
Is it easy to drive? Well, it's an 8 ohm speaker, so it should be. Not so fast, there. This is only part of the story.
Please check out this link::http://www.hometheaterhifi.com/technical-articles/228-a-secrets-technical-article.html?start=1

The Smith Chart is a fine way to visualize the quality of load a speaker may actually represent.

When looking at a speaker then, it is important in evaluating the load it represents by not only the impedance, but the inductance and capacitance as well. As voltage leads or lags current, the strain goes back to the amp.
Please see this link for an explanation / details.
http://sound.westhost.com/patd.htm

Just watching Diana Krall in Paris on the TIVO.

magfan
yes it does...i have two pair of current hungry speakers that rotate in and out of my system (both are nominal 4 ohm loads)

- martin logan clsii
- audio physic libra's (amazing when set up correctly)

it takes some serious current capability amps to get theses speakers to sound their best.
If you want her leaving with a smile it does....?
Magfan,

Excellent point. It begs the question why most speakers and amplifiers are not built as a matched set - what I mean is specifically engineered amplifiers for each driver/load. It also begs the question why designers put capacitance and inductance in the high level signal path right at the last stage - in the speaker crossover. In fact, one might ask if there is any logic to the way most amplifiers and most speakers are made independently.
Shadorne, Nothing wrong with what you suggest but what if someone doesn't like the 'sound' of SS amps, normally used by manufacturers in thier powered speakers?

And, who sez that anything about this hobby, other than marketing and product pricing, has anything to do with the exercise of 'logic'. :-)
Shadorne, Nothing wrong with what you suggest but
what if someone doesn't like the 'sound' of SS amps, normally used by
manufacturers in thier powered speakers?

Then they are in luck because the majority of speakers are passive.

And, who sez that anything about this hobby, other than
marketing and product pricing, has anything to do with the exercise of 'logic'.

Exactly my point. Logic has NOTHING to do with it! Many people claim they want
"High Fidelity" but what they really want (and will part with large
amounts of disposable income for) is most often something else.

So does impedance matter? I would say not for the majority of people who
would ignore an impedance plot but might spend hours picking the right
veneer.
Shadorne, while it is true that powered speakers have many advantages, they do not sell for one simple reason, most audiophiles want the capability of altering the sound of their system. This may be good or bad, but it is the simple truth. I was an Audio Pro dealer in the 80s, they made a powered speaker, the 4-14 I think, that was far ahead of it's time. I think I sold 2 pairs. When I sold Meridian I didn't even try to sell the speakers. In fact, many, if not most audiophiles select the amp before the speaker. I will agree with you that this is totally bass akward but unfortunately true. I must also admit that I use passive myself although I choose my amp to compliment the speakers I am using not vice versa. Our systems are chosen to reproduce music the way we ourselves hear it and active speakers limit that to a significant degree. The full development of unobtrusive digital tone controls may be the best path to active; Meridian is working along these lines but I am not really currant with their work.
Stanwal,

You make excellent points and I am in complete agreement.

most audiophiles want the capability of altering the sound of their system. This may be good or bad, but it is the simple truth

This statement just about sums it up. However it presents another illogical paradox when confronted with the concept of EQ or tone control. Most purists shun these tools yet good or bad, they also seek the capability of altering the sound of their system. Go Figure. (And they used to say that you can never understand a woman....but hang on, most audiophiles are men!!!)
There is nothing confusing about audiophiles rejecting the use of equalizers or other tone benders. Are we not he leading example of, and may actually define, what being a masochist really means? :-)

Anyone want to buy my demo hair shirt?

Anyone want to buy my demo hair shirt?
Newbee (System | Reviews | Threads | Answers)

Only if it is a Tube Top. (sorry, couldn't resist) ;)
You said it Magfan! Speaker impedance should be studied/viewed uisng *both* the impedance & phase curves. The phase angle lets the user know what sort of real-time strain will be put on the amp.

If users do not like passive x-overs, they are free to try active x-overs. There are many examples in the market + many more from various speaker manuf.
If you choose to stick with passive x-overs, then, large L & C values are needed. Just the physics of the matter!
Boothroyd-Stuart Meridian's method for active speakers using digital technology is supposed to be the best-in-class tho' I have not heard any of their speakers.
ATC's method of active speakers is your other choice. Many people like their sound (implying they like their design & the sound of their in-built amps). Maybe you will like them too?
Thanks, Bomb, you da' bomb!
Yeah, speaker impedance is an over-rated spec...and not all that useful.
As you can see from my Moniker, I am a Magfan...now for over 25 years. The ONLY plan I have is to upgrade my X-overs using all standard, but hi-end components.

Next question....'the myth of hi-current'.........
Has anyone looked at the link to the Smith Chart....
It is a VERY interesting way to view the impedance curve of a speaker VS phase angles, which is really a much better way to evaluate 'is it a good or bad load?'

happy listening.....
Magfan, impedance actually is pretty important. I've read the whole thread here and not seen any of the important issues addressed- here they are.

1) The lower the impedance, the more power you will get from a transistor amp, within the limits of that amp's individual abilities. This is not to say that it will sound better- low impedance is only an advantage if you want sound pressure. The effects that low impedance loads have on any transistor amp are otherwise bad for sound **quality**.

2) Tubes prefer higher impedances as well but for different reasons. Reducing the impedance of the load will cause a tube amp to loose bandwidth, power and increase distortion, even if there are taps on the output transformer for the load. Many tube amplifiers will actually run cooler on higher impedances- the output transformer or output section if there is no transformer will be more efficient.

3) Higher impedances thus sound better on both transistors and tubes, all other things being equal, a 16 ohm speaker will thus sound better than a 4 ohm speaker. 'All other things' seem like they are never equal, but going to 16 ohms is an easy way to make a speaker seem more transparent and relaxed, regardless of the amplifier.

4) Lower impedances demand far more out of the speaker cable, for best results it has to be kept short and with larger conductors. Higher impedances are far more forgiving of speaker cables- you can use longer lengths and lesser materials and not loose resolution.

In general, higher impedances are preferred if sound **quality** is your goal, low impedances are preferred if sound **pressure** is your goal, but only with transistor amps. Tube amps will not loose power with higher impedances but transistors usually will.

BTW, the difference between sensitivity and efficiency is worth discussion here. Sensitivity is 2.83 Volts at 1 meter, Efficiency is 1 watt at 1 meter. Let's say you have a system that uses 2 8-ohm drivers in it. Furthermore, the drivers are 90 db 1 watt/1 meter. If the 2 drivers are in parallel (4 ohms), the sensitivity will be 93 db, but the efficiency will still be 90 db. If the speakers are wired in series (16 ohms), the sensitivity will fall to 87 db, but the efficiency will again be 90. IOW, the sensitivity of the speaker can be affected by the impedance, but does not affect the actual efficiency.

Depending on the amp, this can have a big effect on how it will behave on that speaker! Going from 4 ohms to 16 ohms will cut the power of most transistor amps by 75% (although it will sound better). Let it not be said that impedance is unimportant :)
A speaker with a higher impedance might theoreticaly sound better, and even then within some limits, but in practice that isn't always the case. I have yet to hear speakers with a "high" impedance load that I would care to own.
Has anyone looked at the link to the Smith Chart....
It is a VERY interesting way to view the impedance curve of a speaker VS phase angles, which is really a much better way to evaluate 'is it a good or bad load?'

I read the article, and it is indeed somewhat interesting, and I don't see anything wrong in it technically. The article does a good job of emphasizing that the magnitude and the phase angle of the speaker impedance, as functions of frequency, must both be taken into account in assessing how difficult a load it represents.

I see two basic problems, though. First, it is difficult to interpret due to the lack of frequency information on the plot. The author himself acknowledges this:

The main drawback compared to the normal, two-plot method is that we lose the frequency dependence of the impedance.

The second problem is general lack of availability of this kind of plot across a wide range of speakers. I think that being able to meaningfully utilize this kind of plot for a specific speaker would require prior familiarity with what the plots look like for a large number of other speakers, of various types.

Thanks for the interesting read!

Regards,
-- Al
Agreed on both points....But, nobody ever said it was supposed to be easy. Also, once you are accostumed to this presentation of phase/impedance it is fairly easily seen.
Frequency data would be Very helpful.
Hi Ralph,
all your points on impedance are well taken.

IMHO Magfan's original post did not imply that impedance was not a useful number; in reality it is! I quote from Magfan's thread-starting post:
When looking at a speaker then, it is important in evaluating the load it represents by not only the impedance, but the inductance and capacitance as well. As voltage leads or lags current, the strain goes back to the amp.
I believe that point that he wanted to highlight was that we need to look @ impedance using BOTH the impedance & phase plots as a duo. All what you wrote in your post applies.
Most people just blow off the phase plot because they do not understand how to use it & they think that the impedance plot is it. Wrong!
I think that you understand this (& I'm sure, besides Magfan, Almarg & a few others out there do as well).