Sub connection to CARY SLP-05 preamp

25K is sufficiently higher than 3.4K to be good enough. The worst case rolloff, which would occur at 20Hz, would be less than 1db, probably significantly less than 1db.

The reason I mentioned the issue is that a lot of subs have line-level input impedances in the range of 5K to 20K or so, which would be low enough to cause significant rolloff in the bottom octave if driven by the SLP-05.

do I need to biwire it back to from sub to poweramp according to some threads?

You may be thinking of the configuration in which the preamp is connected only to the sub, and the sub's high pass outputs are connected to the inputs of the main power amp. That would prevent deep bass frequencies from reaching the main power amp and the main speakers, which is sometimes done, although it puts the sub's circuitry into the main signal path. Given the high quality of your system, as well as the uncertainty about the sub's input impedance, that approach is most likely not preferable.

If you connect the main power amp's outputs to the sub's speaker-level inputs, as I suggested, you would continue using the existing cables and connections between the power amp and the main speakers, but you would add a second set of wires between the power amp and the sub's speaker-level inputs. Those wires could be narrow gauge inexpensive wire.

Regards,
-- Al

SLP-05 is running XLR to AMP.

Almarg,

Sorry I am a bit confused with the ohm thing.

You said
1. SLP-05 3.4k ohm at 20Hz, if sub input impedance < 30k ohm = bass possibly roll off. (10 times rule)

2. When Titan amp input impedance 25k < 30k ohm, you then compare to 25kohm to 3.4k directly saying its high enough (direct 1:1 compare?)

Did I miss anything? Or amp vs sub is different story when matching the impedance 10times rule?

I hope I made myself clear with these questions, otherwise, please feel free to ask me to elaborate again. Thanks very much for your help.

I will try your Sub connection method when I get back a pair of speaker cable loan to a friend.

The 30K figure I originally cited was a conservative rough approximation, cited as an example (the term "e.g." which I used means "for example").

Prior to submitting my subsequent response, in which I indicated that 25K would also be ok, I did some calculations which confirmed that.

The same principles apply whether the preamp is driving a sub or a power amp, except that in general it will be a more critical issue when a sub is involved, since main speakers will typically be greatly rolled off anyway at frequencies approaching 20Hz, where the preamp output impedance is highest.

The 10x rule incorporates conservative margins, IMO, provided that it is applied at the worst case frequency, where the preamp's output impedance is highest. Falling a little short of satisfying that rule at 20Hz, as a result of a rise in preamp output impedance caused by a coupling capacitor (as in this case) can be shown by analysis to be insignificant.

Regards,
-- Al

So say if an amp with 100k input impedance, is it always better to produce the bass response than one with only 25k? Or it is just a matter of enough, excess is useless?