[Eeyore]

maxhifi wrote:

"Eeyore" wrote
Ace Rimmer wrote:

I read somewhere (wish i could find it now) that it improved dampening.

You mean damping and yes it will increase the damping factor. Proponents
of the SET however prefer the 'improvement' of low damping factor, which
tends to rather sloppily 'enhance' the bass registers.

Graham

It can make a big difference, and can be useful for system tuning. I have 6
ohm speakers, and in a small room (my old apartment), they need the 4 ohm
tap, with its better control over the speakers, which tended to sound boomy
on the 8 ohm tap in that environment. In a large room, the 8 ohm tap gives a
slight bass boost at resonance, which is just what the speakers need to
sound their best, as room enhancement is nowhere near what it is in a small
room. It's not a gross difference, but it's definitely the difference
between good and amazing sound.

Yes, I can see the science behind all of the above effects.

You can of course get a very similar effect by using traditional EQ instead of
the amplifier tap / impedance to determine the bass respnse.


It increases the damping factor, because the output impedance (Thevenin
series resistance) of the output tube is being stepped down to half the
value on the 4 ohm tap than the 8 ohm tap.

Exactly so. This will give better 'control' of the cone at LF. Going the high
source-Z route results in less control of the bass and more of a 'farty' sound
since speaker resonance is allowed to continue longer.

Grahamm