Hi again Jason....sounds like a wheel bearing from that description, maybe you could copy and paste here for some more accurate opinions, you haven't stated where abouts in the Spider that the sound is emitting from or if there are any actual vibrations. Belts also let off a whine when they are worn, loose....maybe have someone rev the engine whilst you stand, bonnet (hood) up, look and listen, just don't touch.... A bit more visual / audible evidence may ring a bell for someone here...Best of Luck and Cheers
I've studied this a bit more. The vibration sound seems to be coming from behind the dash and, strangely, only seems to happen when I am between 2700-2900 rpm. To clarify, I am not feeling the vibration, I am hearing it and it is a very annoying buzzing. I have replaced the door bushings and removed the engine cover. I thought it might be vibrating since replacing the coils with the Alpha Romeo 4C coils. No difference.
I would to make sure the brace over the engine is tight if you have one. If you have anything on your dash remove it and see if that works. Sounds like you might have some vibration in that rpm just not enough to feel and could be suspension related. Check tire pressure and check to see if you may have thrown a wheel weight. If you have a gopro you could place it under in the engine bay close to the cab and take it for a short spin to seen if it is coming from the outside or inside under the dash itself. You could jack the car up and check for wobble in the wheels but from what you are saying I don't think it's a bearing. Without seeing it thats about all I can think of. If something else pops into my head I'll be sure to bring it up.