34hz ported sub?

Hi.  I'm having trouble understanding my system and what's been built for me.  I have a 1999 for expedition.  I took out the original console, and had one custom made with a 10 inch DD 9510 subwoofer (looks great but not the problem).  Its a ported box with a tuning of 34HZ is what the guy says (he says he did a sweep using something to help determine the tuning of box and port).  What has me baffled is that my deck has settings of 50-80 hz for subwoofer, and so does my amp.  (I have a pioneer f90 and an old rockford punch mono 1000bd), but why then is the box tuned to 34 HZ if my deck filters from 50 Hz minimum?  Should the port be shortened to match the deck's filtering?  Is the sound or performance afftected in any way?  Should the box be tuned to 50 Hz then?  any suggestions?

The crossover allows 50Hz and below to get through the amp.  Or 80 and below.  A ported box does not like to play any frequency below the tuned frequency.  If you tune it any higher than it is now, you will not be happy.

So does that mean I should re-tune the port or shorten the port so the box is tuned at 50 hz instead of 34 since my decks crossover is adjusted from 50 hz?

No it does not. I think "i am" was pretty clear. Your deck is crossed at 50Hz. So the deck is sending 50Hz- 20Hz to the sub. Nothing higher than 50hz is going to the sub. If you rasied tune to 50Hz. Everything lower than 50HZ would be muted and roll off to nothing because of the enclosure tune. Everything higher than 50Hz would be cut off by the crossover. What are your box dimensions and port dimension? Is there a problem with what you are hearing?

No. I only wanted clarifying to why the box is tuned to 34 hz and and my amp is crossed at only 50 hz. That's what I set it as.

stevdart wrote: napew2008, you're looking for a relationship of those frequencies that does not exist.  They are not relative to each other.  The 50Hz is a crossover frequency that acts to separate the musical content from the midrange speakers to the subwoofer.  The 34Hz is the tuning frequency of the enclosure that holds the subwoofer, so that, centered at that frequency, the box adds additional tone to the subsonic music. If it were a sealed box you would not have a tuning frequency to be confused about.

Well put.

I do not know what kind of drivers you have for mid bass, but chances are you are missing a lot of usefull information by having your subs crossed at 50Hz.  80 would probably be a much better choice. 

Thank you for responding. I have a separate amp to power my fronts. Its a jl 300/4;good amp.

Mid bass driver = speakers.  Unless you have some 8 inch woofers connected to the 300/4 you have to be missing the info from 50 to at least 150Hz.  I would at least listen to it crossed over at 80 or maybe even 120 Hz.