Impedance questions

I

iwatkins

Guest
I have a receiver that the majority of the speaker outputs are labelled 8-16 ohms. The speakers that I use at the moment are 8 ohms.

However, I'm looking at some new speakers of which the technical spec. says they are 4-8ohms. Now I would have thought they were either 4 or they are 8 ohms.

Anyway, supposing they were actually 4 ohms, what would the effect be off wiring these up to a receiver that is labelled 8-16ohms ?

I've always been told, and the manuals always say the same thing. DON'T DO IT, YOU WILL DAMAGE YOUR EQUIPMENT !!!

However, what is the actual effect ?

And if a speaker maker says 4 - 8 ohms, would you consider that safe to use on a receiver that says 8 - 16 ohms ?

Thanks in advance.

Ian
 

Reiner

Active Member
However, I'm looking at some new speakers of which the technical spec. says they are 4-8ohms. Now I would have thought they were either 4 or they are 8 ohms.

That's correct, there is no such thing as e.g. 4-8 or 8-16 Ohm. It's either 4 Ohm, 6.5 Ohm or whatever Ohm, else you need to specify the correct range based on a measurement.

The DC resistance is a constant (which is the figure usually stated), but the actual impedance varies over the entire frequency band.
E.g. the Dynaudio Contour 1.3MkII speaker is considered a 4 Ohm speaker, but the actual impedance goes from 3.5 - 14.1 Ohm (manufacturer's ratings).

A speaker labelled as 4-8 Ohms will usually be a 4 Ohm speaker, and IMHO there are hardly any true 8 Ohm speakers on the market.

An Amp rated 8-16 Ohm means the manufacturer recommends the use of speakers rated 8 Ohms or higher. But try finding a 16 Ohm speaker though - unless we talk mini-/midi-systems. ;)


Anyhow, in praxis it means a 4 Ohm speaker is harder to drive and represenst a higher load to the amp as the impedance can drop, even below 1 Ohm - depending on the type / modell.
A real 8 Ohm speaker will usually not drop that low and thus is easier to drive.
Note that also the sensitivity of the speaker defines how hard or easy a speaker is to drive, the higher the value (stated in dB) the better.


As to your question if you can connect a 4 Ohm speaker at an amp rated from 8-16 Ohm:
Yes. It's not recommended (manufacturer playing safe) but if you keep the volume withing normal levels I won't see a problem.
Naturally the amp will struggle if you try to have a party or run a disco on the weekend.
 

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