Nut Hair Trick
10-11-2011, 03:46 AM
I'm coming up with ideas for my build and more than likely I'm putting more into this than I should. I probably ought to just build a basic ported box with port and sub firing backwards but I wanted some opinions on one design. This design would have both firing forward into the ski-hole with the ski-hole opening measuring 6x10" which could be made bigger if need be. Of course, I would seal off the trunk in some fashion, but with that in mind, I have 3 questions.
1) would this go from a regular ported enclosure to a 6th order, with the enclosure sealed off to the angled back seat?
2) The area in front of the sub, would some of it actually serve as part of the port, thus making the port longer and tuning lower?
3) Any phase/cancellation issues that you see with this particular design?
10-11-2011, 09:37 AM
It looks like a great design! Without actually figuring for the response, one cannot comment on it's performance though. BUT, knowing a lot about loading factors, this end of the port area, much like a tapped area, will not add much to the response due to the sudden expansion from the constant port area. if anything, that part will increase the output only at higher frequencies, likely out of the efficient range of the drivers response. BUT the great thing is, it will likely not hurt the response either. So, this is one of the few types of ideas that will work for appearance and formal physicality as well, so it does not appear so "basic" in appearance.
As far as it becoming a 6th, technically everything loaded into a vehicle with windows will become a straight or quasi BP acoustically. So, technically yes. And as far as phase cancellation.......again, not something visible. It would have to be calculated. But a lot of times with phasing issues, you can point out some physical qualities that reoccur. In this design, so much is going on it would be tough to tell, and anyone that says there is/isn't cancellation would be lucky to guess right or wrong. You have a compression area, a constant port, and end expansion, and a tapp going on all at the same time. Could become very efficient, but again, since you have it modeled, you might as well calculate it as see what it can do. :)
10-11-2011, 09:41 AM
Also, since you mentioned the skipass, if it is reasonably smaller than the designs port area, this will also have an effect on the response and accuracy of what you calculate. So, making the skipass as large as possible is recommended. I did a design recently for a 6th order that didn't have enough skipass port area for it to operate properly. We had to change the design idea even though the anechoic response gave a wonderful response curve without accounting for it yet. These things have to be accounted for as well because they can change everything. Likely, by expanding the end of the port and then contracting it again to the 6x10 area, you are creating another compression area that could possibly cause some cancellation.....possibly. just a thought.