Hi, thank you for your speedy replies.
I am building a home cinema at the moment with projector and 90" screen, so in actual fact should have a subwoofer that compliments this set up for movies. Although I am an avid music audiophile and in the process of building a pair of Fostex full range speakers. I am not a bass junkie, so maybe an inbetween to compliment both music and movies would make me happy.
DIY building is not a problem for me, I feel my main problem is calculating appropriate sizes, placement and tuning.
After reading that web site you gave, I have come to think that a sealed box would be the most easiest to build. A passive radiatir set up would give me ease of tuning compared to a ported sub, but a transmission line sub woofer is very tempting (as this is similar to what I am building for my fostex speakers) but not sure the dimension I have given would fit a transmission line set up.
The speakers I have been looking at are the
Peerless XXLS-308ALU 12" ttp://www.europe-audio.com/Product
Dayton High Fidelity Subwoofer 15"
With the following plate amp
Money wise my max spend should be no more than £500 (approx $700-800 USD). But for this money I am wanting to create a much better subwoofer than the one in the link below, the link below is a subwoofer that seems to be highly rated in the UK for less that £500.
Again, ideas and advice are very welcome on what you think I should do.