I’m curious, too. I just ordered one of these Analysis Plus Sub Oval cables. I’ll report back after a week of burn-in. My preamp has two sets of line level outs, also. One pair of IC’s goes to the amp. The other pair goes to the sub. The x-over point is manually set via the sub’s controls. If your preamp is a HT processor, you can set x-over via the menu for the LFE output.
Someone else with more EE knowledge can answer, but I think you'll have a problem tying the Left & Right preamp outputs together with a Y adapter.
As far as a subwoofer cable is concerned, I see no reason to spend money on something labeled specifically for a sub. Since distance is typically longer to a sub, I suggest balanced cables when possible.
I've used the following in several systems for many years:
As they only need to relay lower frequencies, sub cables don't need to be as highly configured as regular speaker cables.
Even Vandersteen supplies rather ordinary cable with his subs. I use Cable Solutions, as recommended by Almarg.
Without knowing what sub and pre you are using limits what can be recommended.
For me, using a powered subs, I use two runs from the amp-one for speakers, and one for the subs if I don't have a crossover. Since both speakers and sub share the same signal, integration should be easier.
There is a slight difference in running 2 separate cables to the L/R inputs on the subwoofer vs. using a Y adapter at both your preamp and sub. On my system, the 2 separate cables sounded a little better. It's not a big deal and many wouldn't hear any difference at all. I was using a VMPS sub and VMPS ribbon speakers. They have very good definition.
To answer a few different posts and provide some info...
I have a JBL 8400P sub and it has both L/R line level inputs, 50-150hZ variable crossover control, phase switch etc.
AES3-MKII preamp (made by Cary) which has 2 sets of L/R line level outputs.
It is feeding a pair of modded Dynaco MKIV monoblocks. (Must give grannyring some props here. He rebuilt/upgraded these things, and they are beautifully done, as well as sounding incredible. Really nice guy too, as others have said here.)
The JBL manual gives as an option putting a Y inline if your pre-out is only a single RCA jack, so I don't see how it could harm anything to Y the connection on both ends, as stated previously it is mono.
I have a large volume room with hardwood floors, which makes my sound a bit on the bright/thin side with some recordings. I am just wanting to tinker with the sub to see if it makes the bass deeper without being too muddy/booming, and I didn't want to dump a fortune into cables (it's about a 10-12ft. run from my rack to the sub) just to find out that it was not much better.
Thanks for the feedback so far.
The JBL manual gives as an option putting a Y inline if your pre-out is only a single RCA jack, so I don't see how it could harm anything to Y the connection on both ends, as stated previously it is mono.What the JBL manual is describing is "splitting" a single line level signal. That is no problem.
What you are describing is "combining" (reversing the Y adapter at the preamp) the Left and Right output line level signals. The possible harm is that the Left and Right outputs are connected together. Intuitively, it's a bad idea to connect an "output" into another "output."
The output impedance of the preamp (say 300 ohms) will be much lower than the input impedance of the sub (say 10,000 ohms), so the Left and Right outputs will see an effective parallel impedance of 291 ohms. Unless the output of the preamp is robust enough to handle such a low load impedance I think you risk damaging the preamp.
Whether or not the sub is mono is irrelevant.
Do a web search on using a Y adapter to combine signals. Or give Cary a call and ask what happens when you connect the outputs together.
I didn't want to dump a fortune into cables (it's about a 10-12ft. run from my rack to the sub) just to find out that it was not much better.A pair of 12 ft Belden 1505F cables runs $60. There's no reason to spend more.
Update: After only 24 hours of burn-in, the Analysis Plus Sub Oval cables have bettered my full-range IC’s going to my sub. The AP’s are tighter and more tuneful in the netherworld under 30hz. This is fairly surprising since the full-range IC’s have a fast attack in the upper frequencies. Both sets went deep. The difference isn’t huge - but, it is apparent if the sub is properly dialed in. And I was anticipating a refund upon sending them back. ;-(