Thread: What's the point of Low Impedance speakers?

Originally Posted by thomasward00

I've heard both 4ohm and 8ohm speakers that sound great, what is the entire point of Low Impedance speakers since it requires better gear and also works that gear harder than an 8ohm speaker.

Is there any sonic advantage?

There is no sonic advantage for low impedance speakers vice high impedance speakers. Speakers rated at a nominal 4 ohm impedance are often low sensitivity speakers as well which demands amplifiers that meet certain requirements which includes high power and the ability to double their output power as the impedance is cut in half.

More weapons grade mis-leading information MEP ..

Originally Posted by a.wayne

More weapons grade mis-leading information MEP ..

Oh, I suppose you went through a conversion and now low impedance/low sensitivity speakers don’t need high power amps that are capable of doubling their output power as the impedance halves. This from the guy that thinks 114 dB sensitive speakers need 1,000 watt amps so they don’t clip.

More weapons grade Ignorance , hilarious how proud you are with it..!



Low impedance affects efficiency not sensitivity, you can have high sensitivity with low impedance, the design criteria determines where your going with impedance , if you are running multiple drivers you are gonna have low impedance, doubling of the cone area half's thd over a single driver and increases sensitivity by 3db, so there are many advantages to those type of large multiple driver designs , its not 1923 we are way beyond 3 watt amplifiers and extra wide highly refractive and resonant blue baffles ...!


Regards

PS: Herve at Dartzeel uses more than 1000 watts /ch to drive his 112db Klipsch horns , those in the know do , even Ralph at Atmasphere prefers his high powered mono blocks on his Horns. High impedance uses more power than ( same sensitivity) low Z , as low- Z loudspeakers run on current , most will get along nicely on 10 amps.

Originally Posted by mep

There is no sonic advantage for low impedance speakers vice high impedance speakers. Speakers rated at a nominal 4 ohm impedance are often low sensitivity speakers as well which demands amplifiers that meet certain requirements which includes high power and the ability to double their output power as the impedance is cut in half.

Errr ....

High efficiency or high sensitivity or both ...??

Wow - a thread with personal attacks, misleading videos, and plenty of misinformation.
At least now I know why Tekton speakers are some of the worst I’ve ever heard.
The designer is an idiot.

You left out Irony , or you would have covered your post perfectly ...!



Anything technical to add ... ?

I get the impression many either misunderstand sensitivity or take it for granted. What I mean by that, as example, my 4367's are 94dB, some think they could be driven by a low powered tube amp, you might get sound that way but the 4367 won't even wake up. Many JBL are like that, I had 100 watts of CJ power and barely ran 1400's, not close to their potential though. Legacy are the same, high sensitivity, mostly multi driver, large driver, but they need a good amount of power.

It seems to me there is a trade off between true sensitive speakers, those that can be driven by low watts, and, bass response. The higher the sensitivity the higher the bass begins to roll off. That could be also due to most of those using high crossover points for the bass driver to keep from using multiple drivers.

So if multiple drivers drive down impedance, couldn't we say low impedance speakers generally can play lower?

Originally Posted by Mr Peabody

I get the impression many either misunderstand sensitivity or take it for granted. What I mean by that, as example, my 4367's are 94dB, some think they could be driven by a low powered tube amp, you might get sound that way but the 4367 won't even wake up. Many JBL are like that, I had 100 watts of CJ power and barely ran 1400's, not close to their potential though. Legacy are the same, high sensitivity, mostly multi driver, large driver, but they need a good amount of power.

It seems to me there is a trade off between true sensitive speakers, those that can be driven by low watts, and, bass response. The higher the sensitivity the higher the bass begins to roll off. That could be also due to most of those using high crossover points for the bass driver to keep from using multiple drivers.

So if multiple drivers drive down impedance, couldn't we say low impedance speakers generally can play lower?

You have touched on a big sore spot for me with super high sensitivity speakers and their lack of balance , for good spectral balance you will give up some sensitivity for bandwidth , its one reason why such speakers with good balance will have multiple large bass drivers..

As to power necessary on large JBL speakers has a lot to do with bass driver mass and consumed power to excite for good bass, also sensitivity is usually measure at midband which is 1K , but dont underestimate how many audiophiles listen to clipping as part of their audio experience, its been my observation most amps are chosen based on their clipping characteristics as much as drive.

Herve at Dartzeel do see 200-300 watt peaks on his 112db klipsch corner horns when playing music with high crest factors, very few amps sold today have accurate power meters as Darts do , i have been told this is so as not to have the appearance of using up the full amplifier, so many output meters read lower than actual output Being used ..


Regards

Originally Posted by TheOctopus

In reality, only a DC signal would produce a constant load of certain resistance number from a loudspeaker. We don't listen to DC and the speaker impedance is never a constant...

Impedance is the "effective resistance of an electric circuit or component to alternating current, arising from the combined effects of ohmic resistance and reactance".

Magico M2 impedance just as an example.



From Stereophile review/measurements section on the Magico M2 (just as an example)


Although Magico specifies the M2's sensitivity as 88dB/W/m, my estimate was slightly lower, at 86dB(B)/2.83V/m. The M2's impedance is specified as 4 ohms. My measurements indicated that the impedance magnitude (fig.1, solid trace) was close to 4 ohms in the midrange but drops to 2.3 ohms between 74Hz and 88Hz. The electrical phase angle (dashed trace) reaches –71° at 50Hz. Although the magnitude at this frequency is 6.5 ohms, this phase angle significantly increases the current needed from the amplifier. This, and the combination of 3.2 ohms and –54.5° at 60Hz, means the M2 will be a demanding load. The single impedance peak at 40Hz indicates that this is the tuning frequency of the M2's woofers. The reduction in impedance above the audioband, in combination with an increasingly negative phase angle, is unusual. Loudspeakers typically have a rising magnitude in this region coupled with an increasingly positive phase angle, these both due to the tweeter's voice-coil inductance.

Its why these Magico’s really need power to come alive not to mention amps which can drive current into low Z loads and not fold ..


Regards

Originally Posted by a.wayne

You left out Irony , or you would have covered your post perfectly ...!



Anything technical to add ... ?

Sure. Most speakers are electrodynamic meaning they have a diaphragm or cone that moves air. The diaphragm is connected to a coil operating in a strong magnetic field.

The driving force (F ) that sets the diaphragm in motion is proportional to the current (I ) flowing through the voice coil according to the formula F = BlI where the product Bl is called force factor (B = magnetic flux density; l = wire length in the magnetic field). B is the flux density or strength of the magnetic field.

This force, then, determines the acceleration (A ) of the diaphragm, which is determined from the basic Newtonian law F = mA . The radiated pressure, in turn, follows the instantaneous acceleration.

The speaker driver in the end obeys only current. Almost all of our amplifiers are voltage sources that try and maintain a specific voltage across their terminals irrespective of the current flowing through them.


So what does all this mean wrt 4 ohm or 8 ohm speakers? Simply that it takes twice the voltage at the amplifier output for an 8 ohm speaker to create the same current and this the same spl as a 4 ohm speaker, all else being equal. That’s it.

All else is never equal and I’ve simplified the situation by removing a lot of secondary effects like back emf.

Suffice it to say, it just doesn’t matter what the speaker’s impedance is as long as the amplifier connected to it is operating in its linear region and can drive it properly.

Well maybe you simplified too much ,

Back EMF is there regardless if 8 or 4 ohm , as to impedance not mattering, it depends on how you got there , a multi driver system will have a low z over a single driver setup , not to mention xover phase angles which is the real devil in the work required by the amplifier , this of course affects toobs differently than SS amps.

With SS amps the lower Z load not only requires more current but affects things like Beta Droop , SOA , Feedback and bandwidth, reduction in class A bias and of course increased THD . These can be compensated for by having a much lower thd and dynamics from the loudspeaker system, this is very important than just have a lower Z , the low Z load has to be compensated for in THIS manner , SO YES THE LOUDSPEAKER IMPEDANCE IS VERY IMPORTANT, as it depends on how you got there !


We can take a look at your SF loudspeakers for eg, mated to a transformer coupled Toob amplifier , how are you compensating for the transformer mis match , are you using the 2 ohm tap or 4 ohm tap ..?
An output transformer coupled amplifier represent a different set of metrics to over come for loudspeaker impedance .

So no it does make a difference if 8 ohm or 4 ohm ...!

In the case of the MC 2301, the 4 ohm tap has the lowest output impedance, so that’s the one I use. It also sounds best to me on that tap, for whatever reason.

I'm suspecting the higher voltages drive , many moons ago i had a pr of MC3500’s and they were there best at 4 ohms also unless load was 2 ohms solid ...



Regards

Could be, not sure. Pretty subtle differences when you compensate for the different gain of the taps. Thanks for posting the Futura’s impedance curve. Not an ‘easy’ load.

To the OP’s original question, there are a lot of other factors that come into play besides the rated impedance of the speaker.

Late to the party but Andrew Jones talked about low impedance speakers and he said it is hard to design a small box speaker to have low midbass at 8ohms and high sensitivity. Hence, 4-6 ohm low sensitivity small box speakers. I am pretty sure if he was talking about the Elac debuts and unifi's but I have heard other designers say the same thing.

Originally Posted by W9TR

Wow - a thread with personal attacks, misleading videos, and plenty of misinformation.
At least now I know why Tekton speakers are some of the worst I’ve ever heard.
The designer is an idiot.

Not to mention a video from Paul McGowan... I have meet and spent time with him... never have a meet a person who thought he walked on a cloud more... and I personally know some people who he screwed over who would say I am being far too kind.

One of the best systems I have heard were the Blumenhofer Gran Gioia speakers (100dB) with the Octave Jubilee series (400w 4Ohm) amplifiers. Sounded much better then the flea powered amps.