Sub connection to CARY SLP-05 preamp

The input impedance of the DD-12's line-level rca inputs doesn't appear to be specified anywhere. The SLP-05's output impedance rises substantially at deep bass frequencies, to 3400 ohms at 20Hz, as indicated in Stereophile's review.

The concern that raises is that if the sub's input impedance is not high (e.g. 30K or more), the sub's deep bass response will be perceptibly rolled off.

The best approach, which would eliminate that concern, would be to connect your power amplifier outputs to the sub's speaker-level inputs. You don't need heavy gauge high quality speaker cables to do that, since what you would be driving is the input to the sub's amplifier, which undoubtedly draws a negligible amount of current compared to a speaker.

Regards,
-- Al

Almarg,

Just being notice of this!

My Sim audio Titan (5ch) power amp has an input impedance of 25K, according to what you said, is that causing my speaker rolling off the bass significantly? If yes, does it mean a high input impedance good quality amp will have a great improvement? Any suggestion?

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

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.