New guy, question about excursion calculation

[TommyRocker]

I want to use a HiVi M8A (or N?) in a ported box, as a subwoofer. I know it isn't ideal for super high SPLs but I live in a small apartment anyways. I've read good things about these woofers, and I have some M5a's in some MTM's I built that I really like. I also have to be honest and admit this will be motivated in part by appearance as well. I fully realize there are true subwoofers out there for the money, but I want this setup to look and sound good at the same time. I have WinISD, Which helps for box design and so on, but I need to know if I will exceed Xmax. If I'm in a 1.75 Cu.ft. box tuned to 29 Hz, and I'm giving it 80 watts RMS, how do I calculate if I will exceed Xmax? Also, the amp has a subsonic filter, which I assume should help but, as I said, I'm a novice. I would appreciate any help on this. Software to use, formulas, whatever. I prefer freeware because this is just a small hobby, I don't do enough to justify expensive software. Thanks again!

Oh, and I tried searching, but I couldn't find any help.

[brent_s]

WinISD Pro Alpha has an excursion graph. Enter your 80 watts on the 'signal' tab and then choose 'driver-cone excursion' from the graph drop down.

Do you know the order and cutoff of the subsonic filter? It's possible to include that in the WinISD model. Something like P-E's SA240 or BASH300 would be entered using the EQ/Filter tab...highpass/S.O.S. user specified/cutoff=18Hz, Q=1...but, this only works for 2nd order Sallen-Key type filters.

-Brent

[TommyRocker]

Thank you Brent, I will have to check what version I have and see if I can figure out how to do what you are talking about. From what I can gather its 2nd order in the mid 20s. Time to sit down and start studying... Thanks for the help, I had no idea WinISD had that ability.

[collo]

Some WinISD tips