Explain Speaker Impedance to me

[davewantsmoore]

On 02/04/2021 at 11:24 AM, JkSpinner said:

I have a Denon 3312 that has includes two impedance specs in the specifications 8ohm, and 6 Ohm does this mean the amp will not power 4ohm speakers?

 

The short answer is yes.

 

The long answer is it will probably work (for not high SPLs) but the amplifier may misbehave, which could include distortion, over heating and/or shutting down.

 

If you want to drive speakers < 6ohms to any serious SPL (or at all) you should change the amp to one which is designed to drive a <6ohm speaker.

[davewantsmoore]

21 hours ago, Ittaku said:

That's just how you see it and wish for it to happen. Unfortunately no matter how much you wish for it, I'm quite sure that apart from perhaps some exceptional examples, won't be happening any time soon, if ever.

 

 

Why do you say that?

 

There is a lot (!!!!) of current (pardon the pun) work in this area including everything from giant subwoofers, right through to the speakers you would find inside a mobile phone.

 

[davewantsmoore]

19 hours ago, stereo coffee said:

There is very little marketing in a well written 342 page book

 

I'm not sure I agree the book is "well written"   

It's a tough read..... but it's heart is certainly in the right place.

 

I think it misses it's mark for it's "taregt market" though (those under the 'delusion' of 'pure voltage drive').

 

Anyways.... it's a complex discussion (huurrrr... I did it again)

[davewantsmoore]

13 hours ago, JkSpinner said:

I get it, there’s watts, then there are watts, then there are watts

 

No.... This misleads people (especially a "novice").

 

What you need to do is find an amplifier which is rated to drive the minimum imedance of your speaker, with enough power to drive the speaker to the SPL you want.

 

Just follow the above and foget things like "does the impedance double with a halving of impedance", etc, etc.... and "is this a high current amp"?

 

 

You might need help figuring out the above things.... like whats the minimum impedance of my speaker?.... or how much power do I need to reach my desired SPL? .... or what is my desired SPL?

 

.... but that's what you should focus on...... ask.... or ask your speaker and/or amp manufacturer(s).

[davewantsmoore]

1 hour ago, stereo coffee said:

Trouble is they don't usually meet to discuss each others requirements.

 

This is very true and a very big problem.

 

You know the funny thing though.   "HiFi" is basically the ONLY place where this problem exists.

 

In professional audio.... or embedded audio (like a phone, or TV, or portable speaker), etc. etc.....  the people making the transducers, enclosures, and amplifiers, are highly intertwined, if not one and the same people.

[betty boop]

On 02/04/2021 at 11:24 AM, JkSpinner said:

Hi all

can someone explain speaker impedance to me please, especially how it relates to an amp.

I have a Denon 3312 that has includes two impedance specs in the specifications

8ohm, and 6 Ohm

does this mean the amp will not power 4ohm speakers?

it will JK we have a older 3series denon powering old 4 and 6 ohm Richter’s abs has done for years .. keeping in mind limits to what will achieve and denon rearranged their line up in 2011 so really they moved the range up a notch to include lower rung 1 series. So really current 3 series is more like 2 series level from  2008 and back ...

 

On 02/04/2021 at 11:24 AM, JkSpinner said:

i am considering a Rotel 1555 5 x 120w amp anyway, but trying to get an understanding of what all this means, as I am looking to make several upgrades

do without hesitation this amp is a refresh of the old rotel 1075 (look similar under hood) that was good honest engineering using decent components and will be a very decent upgrade over the 3312 internal amps. Many folk have combined the denons over the years for their processing and rotels as power amps ... work great. Think said in other thread you had a michi 2ch amp ? In which case this would be a great match !

 

Avrs in power amp stage do get better as go up the range but then they still heavily compromised in the greater amount of channels and processing trying to squish in leaving little room for essential things like heat sinks and such

 

you certainly couldn’t squish the power amp like like rotel  1555 or even older 1075 ! So makes sense to add on ...for the benefit

[Ittaku]

21 minutes ago, davewantsmoore said:

 

 

Why do you say that?

 

There is a lot (!!!!) of current (pardon the pun) work in this area including everything from giant subwoofers, right through to the speakers you would find inside a mobile phone.

 

Because I see effectively nothing happening in the general purpose amplification for home hifi which is what we're ultimately discussing here?

[davewantsmoore]

2 hours ago, Ittaku said:

Because I see effectively nothing happening in the general purpose amplification for home hifi which is what we're ultimately discussing here?

 

Yeah, I think it's unlikely to be "general purpose".... but I see it coming.   The world of speaker and amplifier manufacturers being different people (or not heavily intertwined) it very very last century.

[sir sanders zingmore]

20 minutes ago, davewantsmoore said:

 

Yeah, I think it's unlikely to be "general purpose".... but I see it coming.   The world of speaker and amplifier manufacturers being different people (or not heavily intertwined) it very very last century.

It may be changing with the likes of  D&D, SGR, Kii etc but there are still big obstacles which make it hard (and which are usually completely unrelated to sound quality). 
 

EDIT: apart from SGR I’m not sure which of the “all in one” manufacturers are using current-drive in their devices. 

Edited April 5, 2021 by sir sanders zingmore

[almikel]

@JkSpinner did your original question get answered? the thread seemed to go in multiple directions...

 

On 02/04/2021 at 10:24 AM, JkSpinner said:

I have a Denon 3312 that has includes two impedance specs in the specifications

8ohm, and 6 Ohm

does this mean the amp will not power 4ohm speakers?

possibly not - especially at high volumes

Most of the below has been said above in one way or another, but I'll summarise:

• Speaker Impedance is the load presented to your amp - the amplifier you have (Denon 3312) will attempt to deliver a constant voltage to the speaker load for a constant input. The lower the load/impedance, the higher the current your amp needs to deliver based on Ohms law V=IxR (Voltage = current x resistance).
• Speakers/drivers aren't purely resistive, they also typically have inductive (eg cone drivers) or capacitive (eg electrostatic speakers) characteristics, and the inductive or capacitive part of the load is called "reactive" - so your amp has to drive both the resistive load and the reactive load
• Ohms law still applies, ie V=I x R, except R becomes a combination of resistance and reactance, and is termed "impedance"

Getting a bit more technical

• once you have reactance in the load, the voltage and current get out of phase with each other (called phase angle)
• inductive loads (eg normal cone drivers), have a positive phase angle and generally don't prove to be a difficult load for solid state amplifiers like your Denon as long as the impedance/resistance doesn't drop too low for the amp to provide the current - in your case the amp is designed for 8 and 6 ohm loads.
  At low volumes your amp will likely be fine with a 4 ohm load, but at high volumes your amp may not be able to maintain the voltage (V=IxR) to deliver the current into the 4ohm load
• capacitive loads (eg electrostatic speakers like ESL57s), have a negative phase angle - some solid state amps don't like capacitive loads, as it will send the amp into oscillation.
  Some amps more than others - Naim amps seem to have a reputation for disliking capacitive loads.
  Good design of the amplifier removes this limitation.
  There are plenty of great solid state amps that will happily drive a capacitive load - but generally these are amps that are able to deliver high current into a low impedance
• If you have cone speakers, the only thing you need to worry about is whether your amp can provide the volume you want without distortion

cheers

Mike

 

 

[andyr]

Great summary, @almikel!  

 

Andy

 

[davewantsmoore]

On 05/04/2021 at 1:20 PM, sir sanders zingmore said:

EDIT: apart from SGR I’m not sure which of the “all in one” manufacturers are using current-drive in their devices. 

Kii do

[davewantsmoore]

On 05/04/2021 at 10:07 PM, almikel said:

• If you have cone speakers, the only thing you need to worry about is whether your amp can provide the volume you want without distortion

 

This.

 

... or shutting down and/or overheating, which can be an issue in AVRs and similar.    That being said, it's super unlikely to break anything (eg. driving 40hm speaker from 6 ohm rated AVR) .... it just might not sound as good.

[sir sanders zingmore]

22 minutes ago, davewantsmoore said:

Kii do

 

Thanks 

 

I see this in their website

Unique to the implementation used in the Kii THREE is a combined voltage/current control loop that goes beyond merely a better amp – it actively improves the distortion performance of the drive units which contributes significantly to the extreme resolution of the speaker.

 

So presumably they aren't using the same nCore modules that you can buy off the shelf?

[davewantsmoore]

20 minutes ago, sir sanders zingmore said:

So presumably they aren't using the same nCore modules that you can buy off the shelf?

Correct.

 

 

Sorry OP - Most people will consider this off topic  (it's very related to impedance.... but a bit far out from the question which was being asked)   

 

My loose interpretation of it is, simply an extension of what Bruno has said loudly for a long time.   Feedback isn't bad..... unless it is used poorly (it's a powerful tool, with great responsibility, etc).    The whole simple argument of "current drive" is the question of what is it that we are trying to control.    The voltage?  No (it's borderline irrelevant) .....  the current is what is relevant.

 

Well designed voltage feedback... is great and all (better than badly designed)..... but trying to control the wrong thing is quite daft.

 

Voltage controlled amplifier exist for nothing more than convenience.... it is not what any smart person would go to if beginning with a blank sheet of paper.

Edited April 8, 2021 by davewantsmoore

[Steffen]

14 minutes ago, davewantsmoore said:

Voltage controlled amplifier exist for nothing more than convenience.... it is not what any smart person would go to if beginning with a blank sheet of paper.

 

Unless the person was designing an amplifier meant to work with any off-the-shelf passive loudspeaker. Or designing an active loudspeaker costing less than $20k

 

 

 

Edited April 8, 2021 by Steffen

[andyr]

44 minutes ago, davewantsmoore said:

 

Voltage controlled amplifier exist for nothing more than convenience.... it is not what any smart person would go to if beginning with a blank sheet of paper.

 

 

Here's a comment on 'current amplifiers' from an amp designer:

 

Just about all loudspeakers which are designed for SS are set up for voltage drive, that is, a voltage source as the amp.  This accommodates the back emf which is produced by the moving magnet coil.  Pass has done some current amps, sometimes described as current source amps, but they are only suitable with specialist drivers, like Lowthers, which is pretty the same as a tube amp.  The benefit of SS amps is damping factor - so control over bass, with prodigious power.

 

You can design a SS amp to measure current for fb and such an amp is designed for balalaika amp guitars.  It is done to simulate a tube amp, particularly with a very high impedance tube like a pentode.  Such amps give a very tubey sound, delicate, but no sense of real power.  In truth, most people would not like perfect current feedback because it is 'wimpy' and the balalaika guitar amp uses a combination of current and conventional voltage fb.  Current amps need to use a very stiff, low compliance voice coil/cone to sound good, to maintain mechanical control over the excursion because the amp does not have a low impedance, that is, it does not have a high DF.

 

I bolded what sprung out at me as the vital issues.  

 

Andy

 

[Ittaku]

Basically you need a matched pair of current amp with the speakers it was designed for in mind. Excepting the case of active speakers, why would any manufacturer make an amp that only suits one speaker and vice versa? Voltage drive is here to stay.

Edited April 8, 2021 by Ittaku

[sir sanders zingmore]

1 hour ago, davewantsmoore said:

Correct.

 

 

Sorry OP - Most people will consider this off topic  (it's very related to impedance.... but a bit far out from the question which was being asked)   

 

My loose interpretation of it is, simply an extension of what Bruno has said loudly for a long time.   Feedback isn't bad..... unless it is used poorly (it's a powerful tool, with great responsibility, etc).    The whole simple argument of "current drive" is the question of what is it that we are trying to control.    The voltage?  No (it's borderline irrelevant) .....  the current is what is relevant.

 

Well designed voltage feedback... is great and all (better than badly designed)..... but trying to control the wrong thing is quite daft.

 

Voltage controlled amplifier exist for nothing more than convenience.... it is not what any smart person would go to if beginning with a blank sheet of paper.

So if I was (hypothetically) designing a DIY active speaker with off the shelf components, where would I get a current drive amp and how would I ensure it worked well with the speakers?

 

 

[davewantsmoore]

22 hours ago, Steffen said:

Unless the person was designing an amplifier meant to work with any off-the-shelf passive loudspeaker.

That's precisely what I mean by "convenience".    So amplifier designers and speaker designers can be different people.   Daft.

 

22 hours ago, Steffen said:

Or designing an active loudspeaker costing less than $20k

Cost has nothing to do with it.     The $1 speaker in your mobile phone is just as applicable.

[davewantsmoore]

21 hours ago, sir sanders zingmore said:

So if I was (hypothetically) designing a DIY active speaker with off the shelf components, where would I get a current drive amp and how would I ensure it worked well with the speakers?

 

There are few I know of "off the shelf"....  having it "work well" with the speakers is not different to "normal".  In that you EQ drivers to your target responses (regardless of whether using filters before or after the amplifier).

[Steffen]

22 minutes ago, davewantsmoore said:

That's precisely what I mean by "convenience".    So amplifier designers and speaker designers can be different people.   Daft.

 

They can be the same people if they want, it doesn’t really matter. Customers want to mix and match components, so there have to be (more or less) standardised interfaces between them. Those interfaces happen to be defined in terms of voltage, and response to voltage signals. You can get proprietary all-in-one solutions that don’t care about these interface conventions, or even mention speaker and amplifier specifications. BlueTooth speakers, or Apple Homepods, for example. But see below. They don’t play in the same ballpark. 

 

24 minutes ago, davewantsmoore said:

Cost has nothing to do with it.     The $1 speaker in your mobile phone is just as applicable.

 

Are we still talking about home stereo? Because in a home stereo setting, a $1 mobile phone speaker will sound like $1, at best.

 

The idea of all-in-one lock-in doesn’t seem to be palatable to most people investing in a home stereo setup, unless the gamble is worth it by promising huge advances in sound quality. Hence the Kii-style $20k+ price tags.

 

[aussievintage]

22 hours ago, andyr said:

  It is done to simulate a tube amp, particularly with a very high impedance tube like a pentode.  Such amps give a very tubey sound,

 

Off topic, but these days I believe the way to go is modelling with a good DSP.    The best sounding replacement for a Fender Twin Reverb tube amp  is done this way in my Mustang GT.   Bonus, I can switch in a Showman's JBL speakers, or a Vibraverb amp circuit  and much more, at will.  I can also adjust the bias on the fly, and even tweak the power supply sag.

[Cloth Ears]

41 minutes ago, davewantsmoore said:

 

There are few I know of "off the shelf"....  having it "work well" with the speakers is not different to "normal".  In that you EQ drivers to your target responses (regardless of whether using filters before or after the amplifier).

I find it difficult to understand where you can say "few I know of" and "normal" in the same sentence WRT this.

 

22 hours ago, sir sanders zingmore said:

So if I was (hypothetically) designing a DIY active speaker with off the shelf components, where would I get a current drive amp and how would I ensure it worked well with the speakers?

Either you can easily buy off-the-shelf current amps for a project like this, or you can't. As far as I'm aware, you can't - so at this point, off-the-shelf voltage drive is the only option.

[davewantsmoore]

18 minutes ago, Cloth Ears said:

"normal"

Normal with respect to how you would normally design a speaker (the question was how would I get my DIY speaker to work well with a "current source" amplifier).   You measure the driver responses, and correct them to your target.

 

18 minutes ago, Cloth Ears said:

Either you can easily buy off-the-shelf current amps for a project like this, or you can't. As far as I'm aware, you can't - so at this point, off-the-shelf voltage drive is the only option.

Yes, that's right.