hey i have 4 12" T1 rockford power subs being powered by a t2000.1bd RF amp. . . i made a box with the interior dimensions of 14.75 x 36.2 x 29.5
and a slot box of 10 x 8 by 13 deep tuned to 35 hz with the subs facing upwards and the port backward in a 2002 blazer.

now my problem is that the box hits good on low notes but juss doesnt sound right on higher notes. so im juss wondering if the box sizes are right?

 

it could be the box, but it could also be the tuning of the amplifier ro crossovers in your system. but the int volume of the box may be a lttile small @ 9 cubes.

 

I am a little confused here. Which box are you asking about? You give dimensions for a box you made and a slot port box. Are the dimensions for the slot port box correct? I don't see how you will get even one 12" in it at 10x8x13 and you say you have 4 ???. Are all 4 subs in the same box? Do you have 2 different boxes with subs installed at the same time? If you can be a little more specific we will be able to help more.
Nick

 

Im going to guess that you have a bump in the response around the tuning frequency of the system (35hz), and corresponding impedance peak. At frequencies above this tuning frequency, the box begins to act like a sealed enclosure, and the impedance drops, as does the efficiency of the system, so you basically wind up taking way more power to get similar response as you did at the tuning frequency. This isnt necessarily a bad thing if you are going for spl, but if you want a smoothe response, a large vented box tuned low is not the answer. I hate those kind of boxes btw. The only vented boxes I like are ABC boxes and small ported boxes that add maybe 3db to a longer range of frequencies. Anyways, just some thoughts.

 

sry i meant to say the port size is 10x8x13

 

well i played around in winisd and this is the graph i got with the box i have right now, i havent used the program all to much but does it seem right?