In article , Dave
xxxx wrote:
Derrick Fawsitt wrote:
I have just acquired Quad 989's Electrostatic Speakers

[snip]

They are designed for the Quad II-forties and QC 24 pre amplifier

I am not sure that was the case. Although the combination might sound fine
I'd note a few points:

1) The II-40 has a nominal power of 40wpc. This nominally translates into
17.8 Vrms and 25 Vpk for an assumed 8 Ohm tap. This is well below the
maximum which the 989 can accept. This means the combination will be
'safe', but not be able to reach the same peak sound levels as a more
powerful amp.

2) The II-40 has an output impedance of 0.4 Ohms. Given that the 989 has an
impedance that drops to just below 4 Ohms at some frequencies this may
cause a change in the response of the order of 1dB in the region around
10kHz and below 30Hz.

3) I don't have a value for the peak currents the II-40 can provide.
However unless it is significantly higher than implied by (1) the actual
levels may be further restricted when the signals have components in the
regions where the impedance of the 989 dips down well below 8 Ohms.

Hence although the combination may sound fine, the above factors can be
expected to have some impact on the results. If you only ever play music at
low levels, the above may not matter.

Slainte,

Jim

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