What does Nominal Impedance mean?

Curve steepness and width important too. Possibly of interest: https://audiojudgement.com/speaker-impedance-curve-explained/

hilde45,

Thanks for that information. It's still very confusing.

So, based on the speaker specs that I have stated do you think the Carver Amps will have problem with the Clarisys Minute speakers?

ozzy

I believe speakers (and other devices) do not have a constant impedance. So "nominal impedance" is what it has most of the time (average?).

dweller,

So, do you think the Carvers will drive the Clarisys Minute adequately?

ozzy

ditusa,

I watched the video, and I am still confused.

ozzy

I take it to mean the impedance where most of it lies across the frequency range. Case in point: my speakers are 6 ohm nominal, with a minimum of 4.4 ohm @175Hz. Because of that, they state 4 ohm on the speaker.

Not all speaker makers do that. Some just use the average while others state the lowest point. That may add to the confusion.

All the best,
Nonoise

The Carver should have no problem with the new loudspeakers.  The above 6 ohm impedance in the bass frequencies is good and the 3 ohm readings are at frequencies that demand less current.  You might have to turn the volume setting up to match previous volume levels.  There could be rolled off high frequencies if the Carver has a high output impedance in the 3 ohm range.

With all due respect to people who chimed in, I do miss "almarg" on such topics.

Jim Clark from Carver just replied to my email saying that the Carver amps would have no problem driving the speaker based on the specs in this posting. But I wish he had provided more detail.

Here is his reply,

"The nominal impedance is an average of the impedance curve. Many speakers vary between 2 and 20 ohms at various frequencies. Your 350's should have no problem driving them. Enjoy! Thanks, Jim"

ozzy

+1 @milpai, To say he had a way with words is an understatement. Being a copyright lawyer (among other things) he was concise, succinct and a joy to read.

All the best,
Nonoise

+ another @milpai almarg is the one poster who could immediately answer any question! And I agree with @dweller nominal in this sense means average,

Almarg was awesome. RIP.

You could drive a car with those amps! +300W

There are not many speakers those amps won't drive.

michaellent, randym860,

Well, that’s what I think, but sometimes you just never know how different components interact.

Still, it is so confusing trying to figure out the importance of speaker sensitivity and impedance when it comes to speakers.

Wonder why companies just don’t make speakers that are 8+ ohm and with high sensitivity? But it seems to be just the opposite, that is; many of the big-name speaker manufacturers produce speakers that are 4-ohm and low sensitivity.

Wonder why that is?

ozzy

Nominal means "in name only" and has little to do with the actual impedance of the speaker. That’s why it’s confusing. The speaker impedance is measured across the frequency band and someone at the speaker company looks at it and says hmmm... that looks like about 6 ohmsish on average so we’ll call these 6-ohm speakers.

This is one area where published specs are important. I look at the impedance curve of my speakers and they are a flat 2.5 to 3 ohms from 100hz to 10kHz which tells me I need a hefty solid state amplifier for the low impedance but a tube amp with a 3 ohm output tap would work great also since the impedance is flat.

“Nominal impedance in electrical engineeringand audio engineering refers to the approximate designed impedance of an electrical circuit or device.”

@gs5556     How right you are!

'Nominal impedence' is generally concocted by a speaker manufacturer to hide elements of his speaker's impedence curve that he would rather hide.  It has no basis whatsoever in physics.  Responsible manufacturers show the full curve for impedence vs. frequency and the phase angle at audio frequencies, because bad combinations of impedence and phase angle can often occur making a speaker tougher to drive than could be apprehended from the impedance curve alone.

Incidentally I have never seen a speaker whose impedence measures a flat 2.5-3 ohms over 100-10k Hz.  Have you?

This poor manufacturer behaviour is mirrored by not quoting a dB range when specifying low frequency extension, and by over-stating sensitivity, which occurs very often.

(Proper) measurements matter.

@ozzy, are you getting the Clarisys Audio Minuet Neodymium speakers?

lak,

Yes, I think so. Though it will be a long wait to get them, and I will probably have to rob a bank...

ozzy

@ozzy Wrote:

Wonder why companies just don’t make speakers that are 8+ ohm and with high sensitivity? But it seems to be just the opposite, that is; many of the big-name speaker manufacturers produce speakers that are 4-ohm and low sensitivity.

Wonder why that is?

ozzy

Maybe Hofmann's iron law is one of the reason. Article

Mike

ditusa,

Probably, but many large speaker cabinet types still have low impedance and sensitivity requiring monster amps to drive them.

ozzy

Thank you @dweller!

I know this is a complicated subject & not as simple as this but the primary way to get decent, extended, deep bass that can play relatively loudly from smaller woofers ( less than 8” or so) is to have 2 or more of them usually wired in parallel which lowers the effective impedance ( the reciprocal of the sum of the reciprocals). 
 

The taller, narrow baffle designs popular now for the sake of theoretically better imaging lends itself to smaller woofers if the cabinet cost is to remain reasonable & not “sculpted” in some way. many new speakers today have pretty low impedance & thus their actual effective sensitivity is lower than stated. 

@ozzy it is rare that a large cabinet speaker is also not sensitive. The reason for the large cabinet is to increase its efficiency and thereby sensitivity. Small speakers are typically more difficult to drive and require greater power to overcome their lack of sensitivity and low impedance curves. Ohm’s law explains these electrical properties but I suspect it will be a little over your head unless you intend to do a deep dive into the subject. 

Incidentally I have never seen a speaker whose impedence measures a flat 2.5-3 ohms over 100-10k Hz.  Have you?

I have the Thiel 3.6's. From Stereophile:

 

Impedance is a combination of linear R (resistance) and non-linear X (reactance)

A Reactance is a combination of Inductive and capacitive components. In the world of complex algebra the impedance Z is represented by = R + jX. In case of the DC, X component is null so the Impedance in this case is linear resistance R.

Inductive component impedance is known as wL where w is frequency and L is Inductance. 

Capacitive component impedance is known as 1/wC where C is capacitance

Overall Z = R + j(1/wC + wL) where j is directional vector

Notably, with increase of frequency Inductive component increases while capacitive component decreases. that means that on DC capacitor will have an infinite impedance and Inductor will act like short circuit.

czairvey,

Wow! Interesting. Most of this is over my head. I have a business degree.

ozzy

@ozzy,

I think nominal impedance means the industry standard. Impedance should not fluctuate more then 8 or 9% from the standard. I.E. An 8Ohm speaker should be no less then 6Ohms, a 4Ohm speaker should be no less then 3Ohms, if they follow the standard.

Mike

I vaguely remember that the speaker industry standard rating of impedance as what it is at 1000Hz.  Which is kind of silly because the impedance is usually all over the place unless the speakers use series crossovers.

ditusa,

Your explanation makes sense and seems to concur with what I read. (somewhere).

ozzy

@clearthinker Wrote:

This poor manufacturer behaviour is mirrored by not quoting a dB range when specifying low frequency extension, and by over-stating sensitivity, which occurs very often.

(Proper) measurements matter.

I agree 110%! See the manual below of my speakers, it's the most comprehensive speaker manual of specifications I known of. They even explain how they arrive at their numbers. See last page specifications:

Mike

https://www.lansingheritage.org/html/jbl/specs/pro-speakers/1984-4430-35.htm

@fritzspeaks Wrote:

I vaguely remember that the speaker industry standard rating of impedance as what it is at 1000Hz.

JBL’s impedance graph is from 20Hz to 2KHz conforming to international standard IEC. International Electrotechnical Commission - Wikipedia

Mike

Let me ask another question:

So, does a 4-ohm speaker play louder than an 8-ohm speaker with the same amplifier and volume setting?

ozzy

What Mapman said. he nails it.  

So, does a 4-ohm speaker play louder than an 8-ohm speaker with the same amplifier and volume setting?

no, depends on speaker sensitivity

and more broadly, i believe nominal impedance is basically a useless measure

speaker makers don't use the same standards and pretty much write anything into their marketing literature - always always looks at the whole impedance curve

Agree to @jjss49 

Nominal impedance shows exactly nothing. 

 

@ozzyWrote:

Let me ask another question:

So, does a 4-ohm speaker play louder than an 8-ohm speaker with the same amplifier and volume setting?

As I understand, only in 8 Ohm load does 2.83 volts produce 1 watt. In a 4 Ohm load 2.83 volts produces 2 watts. 😎

Mike

So, does that mean they will play louder or does the amp need to work harder? ozzy

@ozzy Wrote:

So, does that mean they will play louder or does the amp need to work harder? ozzy

Both! Also the lower the impedance the amp operates in, the higher the distortion produced by the amp.

Mike

@ozzy 

What does Nominal Impedance mean?

I’m trying to decide on some new speakers (Clarisys Minute). They are rated at 86-88 sensitivity and a nominal impedance of 3.5 flat. Although graphs show it about 6 ohms from 20hz-500hz and at 2Khz and above about 3 ohms.

Turns out you don't need to know what Nominal Impedance is in this case as your speaker has essentially flat response of 3.5 to 4.2 ohm (based on youtube measurement of it).  Normal speakers have wildly varying impedance with frequency so no one number ever represents its impedance.  Your speaker is then is an easy load for most amplifiers.

Better yet, I have tested your Carver 350 amplifier with 4 ohm load.  Here is its frequency response:

The amplifier has a peaking response with this type of load so may sound a bit bright.

You do have a ton of power available:

And even more for short periods:

So you can crank it up good, assuming the copious amount of distortion is not bothersome to you.  In that regard, you are going to hear more of that distortion than your current, more sensitive speakers.

If you like, I can measure your new speakers.  Start a conversation with me and we can take it from there.  Good luck.

OOps.  Post the 8 ohm power sweep.  Here is 4 ohm:

 

Given that it is 8 ohm speaker….Y

Bent

amir_asr, Thank you for that info. I wonder though if most tube type amps would also show a large amount of distortion? BTW, I like the sound of the Carver amps. Previously I owned Atmasphere, Pass, Krell and a few others. ozzy

I was just reading a review of the Rockport Orion speakers in The Absolute Sound by Robert Harley.

They weigh about 350lbs! Cost over $133,000 and it is still a 4-ohm speaker!

ozzy

Nominal impedance means blah blah blah blah, meh...that said, Almarg was one of the reasons I bought a Pass XA-25. A cool guy who's missed around here. 

So, I guess I understand that now, nominal impedance is just a number. Highly questionable, I guess that is so with sensitivity ratings. Different frequencies produce different amounts of energy, so that could be all over the map in reality.

But if 8 ohms is optimum then why are there so many 4-ohm speakers? I put together a DIY speaker a while back and I was able to use all 8-ohm speakers. So, the drivers are out there.

And companies like Rockport, Wilson, etc. claim to make their own drivers, but they design them with lower ohms. Why?

ozzy

Loosely translated into Layman's language it is the impedance at any given frequency. And of course Impedance is roughly  (improperly) equivalent to resistance. Most speakers , as the sound frequency approaches its resonant frequency, the impedance starts to spike. I have had many people ask why I use what is called a 'ZOBEL' network in my crossovers, and this is the reason. A Zobel network tries to compensate for that spike and lets the speaker operate more uniformly at lower frequencies. And be careful when Ozzy says it is just a number. It is but it is a very important number when designing a crossover.