Kicker KX2500.1 audible hiss

Ahh gotcha. No, Bill just let me know he has 13600 that he could provide, That was the extent of that, otherwise its been here publicly in the forum. I went with a NOS 13700.

No it does not vary in frequency. its more like a pink noise. I posted a video in the post above which is the sound it makes. its consistent almost by design maybe?

I dont have any subwoofers handy at the moment, I am using retired floor speakers for testing.
 
If you don't have any protection for the speakers, I'd suggest installing a 400uF bipolar cap or something similar to protect them from DC offset.

Using a speaker that produces high frequencies isn't ideal when testing subwoofers. They aren't designed with high s/n ratios in mind and are often noisy. Do you think this noise would be a problem through a subwoofer (a woofer from a full-range floor speaker may not be a good example).

I don't know your budget or shop floor space but an inexpensive subwoofer in a 1ft^3 box on casters is good to have and can be moved around easily. If it's under the bench, it will produce more bass (like a subwoofer in/out of a trunk does).