Impedance and frequency.

[SHDK]

Hallo all.

I'm really new to this, but I am trying to learn by reading a lot in this forum.

I understand that a speakers impedance changes with frequencies. My own focals has a minimum impedance of 2.9 between 150 and 500 hz.

This makes me wonder. Let's say a speaker plays more frequencies at one. Will a higher middle tone then even out a low frequency tone. And in that way keep the speaker from dropping to it's minimum impedance?

Thanks

Søren

 

[terryforsythe]

No. Even if there was an impact due to high frequency movement of the voice coil, the impact would be extremely small.

 

[solderdude]

Middle frequencies simply will draw less current (at the same amplitude ... say... using white noise)
The load impedance determines what current is drawn at which frequency.
This is a bit simplistic view though as in reality the load is rarely ever pure resistive and can be inductive or capacitive at different frequencies causing a current draw that is different than when the load would be purely resistive.

So ... when a speaker is 2.9ohm minimum you simply need an amp that can provide power in a 2ohm load (when driving it to clipping levels) but when playing at 'normal' levels and not clipping the amp a 4ohm minimal rating will also do.

 

[SHDK]

Middle frequencies simply will draw less current (at the same amplitude ... say... using white noise)
The load impedance determines what current is drawn at which frequency.
This is a bit simplistic view though as in reality the load is rarely ever pure resistive and can be inductive or capacitive at different frequencies causing a current draw that is different than when the load would be purely resistive.

So ... when a speaker is 2.9ohm minimum you simply need an amp that can provide power in a 2ohm load (when driving it to clipping levels) but when playing at 'normal' levels and not clipping the amp a 4ohm minimal rating will also do.

So because the minimum impedance is 2.9 in a test setting. It doesn't mean it will get down there playing music ?

Or do I get it wrong ?

 

[staticV3]

So because the minimum impedance is 2.9 in a test setting. It doesn't mean it will get down there playing music ?

Or do I get it wrong ?

A 2Ω dip at 20Hz is inconsequential if your music/movie/etc has no content at 20Hz.

Your Amp will never "see" that dip then.

 

[sergeauckland]

So because the minimum impedance is 2.9 in a test setting. It doesn't mean it will get down there playing music ?

Or do I get it wrong ?

Yes, it will get down there playing music, but only when playing frequencies at which the impedance gets down there. Whether it matters, depends on how loud you play and what frequencies the music you play contains. In general terms, as long as your amplifier can cope with 4 ohms, you will be fine.

S

 

[SHDK]

Yes, it will get down there playing music, but only when playing frequencies at which the impedance gets down there. Whether it matters, depends on how loud you play and what frequencies the music you play contains. In general terms, as long as your amplifier can cope with 4 ohms, you will be fine.

Thanks for explaining.

I've just bin through that exact discussion picking speakers.

When considering buying the Focals. A lot of people was busy telling me that my amp (Marantz M1) would die from too low impedance. My speakers would die from clipping and it would never work.

But.. so far all seems good.

It also seemed pretty difficult to find amps in that price range rated under 4 ohm.

 

[staticV3]

It also seemed pretty difficult to find amps in that price range rated under 4 ohm.

The WiiM Amp and Amp Pro are rated down to 2.67Ω

The Amp Ultra is rated down to 2Ω.

 

[SHDK]

The WiiM Amp and Amp Pro are rated down to 2.67Ω

The Amp Ultra is rated down to 2Ω.

I have read that. But not how many watt it is rated for at 2 ohm?

 

[staticV3]

I have read that. But not how many watt it is rated for at 2 ohm?

Erin measured 256W per channel: https://www.erinsaudiocorner.com/electronics/wiim_amp_ultra/

We'll know more once Amir hooks one up to his power cube.

 

[SHDK]

That's impressive.

 

[staticV3]

Compared to the M1, yeah.


Source

 

[SHDK]

Indeed. The numbers don't lie.

But I can't say I ever felt the M1 as underpowered in any way. I think it drives my focals pretty well. At least to my ears.