The Natural Philosopher wrote:
wrote:
Dave Liquorice wrote:


IMHO anything with less than 2.5mm^2 CSA is to small.

20W into 4 ohms is over 2A... but it's not just the abilty to carry
the required current. The extra resistance reduces the damping on the
loudspeaker affecting the LF response.


Lets see.

Typical 8 ohm speaker, voice coil R typically 6 ohms.
5 meters of 2 core 1.29mm dia cu wire, tot 10m, 0.0128 ohm/metre, total
R 0.128 ohms.

Cable's R increase as a percentage of total speaker R: 2%.
Ie a non issue.


Cable R as a percentage of amplifier output impedance (say .05ohms)

250%

this is immaterial. The voice coil R of around 6 ohms limits the amp's
ability to apply damping. It limits it by making the R of the damping
circuit 6 ohms in fact.

Picture the voice coil as an ideal driver with 6 ohms in series.


A little knowledge is a dengerous thing.

sometimes. Not in this case, not unless youre playing with 1930s kit
anyway. A 2kohm speaker connected direct to B+ can be.


Normal ampplifiers would have a damping factor (ratio of loudspeaker to
effective amplifier impedance) of 50:1 or better.

But this is meaningless. Its a tech spec used for marketing, not
something that cna actually be applied to the speaker IRL.

Secondly speakers are not normally designed to be fully damped,
resonance is deliberately used to extend the bass freq response a
little lower.


NT