2. amps-preamps
  3. 124210-79517

More resistance is less load??

Hi, can someone explain, in "ohms for dummies" language, why a 4 ohm speaker, which has half the resistance of an 8 ohm speaker, is said to be more demanding on the amp? And the other way, why a 16 ohm speaker, with twice the resistance, is less demanding?
128x128jimspov
jimspov's avatar
jimspov OP
60 posts
 
Almarg, thank you for your elegant, articulate and patient responses!
unsound
7,329 posts
 

There are reasons that a speaker manufacturer might choose to design a loudspeaker with lower numerical impedances. Measurements at the amplifier, are just that measurements at the amplifier. Yes, it's true that those measurements might effect the sound downstream; but downstream, such as at the listening position, there might be measurements that suggest that there were other benefits that made foregoing better measurements at the amplifier worth it.

atmasphere's avatar
atmasphere
11,761 posts
 
there might be measurements that suggest that there were other benefits that made foregoing better measurements at the amplifier worth it.
That measurement is power, which equates to sound pressure. Otherwise there is no real advantage to a low impedance load.

One thing I forgot to mention is how much more important the speaker cable becomes when driving a lower impedance. Into 4 ohms the speaker cable is critical and differences are easily heard between them as a result. Conversely, at 16 ohms the speaker cable is far less important and longer runs can be made with less deleterious effects.

Into 4 ohms, the speaker cable can easily degrade the damping performance of the amplifier. So if your speaker requires a higher damping factor (+20:1) then it will be important to keep the cable as short as possible to minimize its effects. I've seen this have dramatic effects on the resulting bass impact!
unsound
7,329 posts
 

It's easier for a speaker manufacturer to get a steady impedance (which amongst other things increases the potential for frequency linearity) with lower impedances than higher numerical impedances.

Most of speakers that can provide wave form fidelity (time and phase accuracy) have lower impedances.


kijanki's avatar
kijanki
4,427 posts
 
AFAIK long time ago all speakers had higher impedance, mostly 16 ohm but some even 32 ohm.  

Linearity would be much better with underhung motors (coil within a gap) instead of commonly used overhang motor design (gap within a coil). Only few manufacturers use more expensive underhung (larger magnet) design.  One of them is Acoustic Zen.
More to discover