Using some very long balanced Subwoofer cables.

Not too long. Shielded balanced cables. Used all the time in studios at that length or longer. Blue Jeans Cable or Mogami from pro audio stores. No problem. 

Wire makes all the difference, except when it comes to subs. Prior to building mine I was dead certain they would need quality wire just as much as the main speakers. First Duke said no, save your money. But then just to be sure, even though it was Duke, I did compare and sure enough, freaking lamp cord is plenty good enough for subs.

But then what about the interconnect? Surely the interconnect will make a difference??? Well so far I have tried several, and some really good ones too, and right now am using the cheapest crappiest interconnect in the house - because it simply does not matter! I can hear no difference! 

So just like Duke told me, save your money for where it will actually make a difference.

Hi Ozzy,

You mentioned recently in the DEQX thread that you are now using an Ayre KX5 Twenty as your preamp. I see that that preamp provides two balanced outputs and one unbalanced output for each channel.

It is very common for designs which provide two XLR output connectors to simply jumper them together inside the rear panel, and provide both with the same signals. And it is very common for designs which provide both XLR and RCA output connectors to provide the RCA connector with the same signal that is provided to one of the two signal pins on the XLR connector. So depending on the design of the preamp it could very well be that the capacitance of the 75 foot cable will have some effect on the signals received by the main power amp, that are reproduced by the main speakers. The result possibly being small but perceptible amounts of rolloff and undesirable phase shift in the upper treble region, as reproduced by your main speakers.

Stereophile measured the output impedances of your preamp as 78 ohms unbalanced and 156 ohms balanced, which **might** be low enough to make that issue inconsequential, depending on the capacitance of the particular 75 foot cable. But I would suggest that you contact Ayre and ask them if the signals provided to the three output connectors (two balanced and one unbalanced) are driven by separate and independent output stages, or if some or all of them are provided with the same signals.

And if it turns out that one or both signals in the balanced pair of signals that is provided to the rear sub for each channel is/are also provided to the main power amp, you would definitely want to choose 75 foot cables having very low capacitance.

Best regards,
-- Al