Help w/ properly hooking up my ML grotto sub....

Sorry, but there comes a point where if you confuse enough stuff its impossible to help. Your amp has a sub out. Are you using it or not? Because use it and that's pretty much the end of it. Either that or you got me just as confused as you are.

Hello matt00,

     I’m not sure what you mean when you stated:" I am bypassing the P5 2.1 input, how should the reset of the hook up go? I am using Vandersteen Model 2 speakers." You will only be utilizing the 2.1 outputs, not the inputs, on the P5: the left and right main outputs to your amp and one of the two sub outputs to your Grotto.
You don’t want to bypass the P5, it’s one of the few available preamps that have outputs for 2 subs, with built in high and low pass adjustable crossover controls/filters on the back that let you choose the frequencies sent to your sub or subs and which to send to your main speakers.
     Some perceive a benefit of restricting the low freguencies sent to the main speakers, having only frequencies at or above a set frequency sent to the main speakers (high pass filter) and having all frequencies at or below a set frequency sent to the sub or subs (low pass filter). Your P5 manual is linked below and will explain exactly how to connect your sub and how to set the low and high pass controls/filters which begins on page 11.

https://parasound.com/pdfs/P5Manual.pdf

     I’m certain that hooking up two subs will perform and sound about twice as good as just using a single ML Grotto. After you get your sub hooked up and listen with it in your system for a few weeks, I highly recommend at least auditioning how your system improves with the addition of a 2nd sub. The 2nd sub does not have to be an identical ML Grotto, it can be any good quality sub that’s larger or smaller, with greater or less rated bass extension, than your Grotto.

Best wishes,
Tim

matt00

Good advice above.  Enjoy the Grotto- one of the best subwoofer ever produced.

Happy Listening!

Thanks Noble, what I meant about bypassing the P5 was it’s crossover. I thought I would be better off to use the crossover from my sub and not from the preamp. 
For now I’m only going to use one sub. I didn’t think it would be this difficult to add a sub!!

Hello matt00,

     I'd suggest you first utilize the P5's crossover and level controls and follow the manual's instructions closely for best results.  Only if you find the results totally lacking which I seriously doubt you will, would I suggest bypassing the P5 and using the sub's controls instead. 
     Yes, it may seem simpler and more convenient now to just use the sub's controls but you're just bypassing a unique capability the P5 was specifically designed to perform well, I'm not even certain bypassing would function properly and I don't think there's any benefit in doing so even if bypassing does function smoothly.  You'd also be eliminating the benefit of simply and conveniently adding a 2nd very beneficial sub in the future. 
    I strongly recommend that you read your P5 manual on the proper connections of your sub and the proper settings of both its low and high filter controls as well as its level control.  It may also be beneficial to read or watch reviews on the P5 that explore and evaluate how well this unique feature actually works in practice.

Best wishes,
    Tim