starting to calc my box plans for upcoming rebuild.

[fbi90909 0]

so in a month or 2 i will be starting on my rebuild to run 2 old style XXX15's, 2 sundown saz-1500d's and other goodies i haven't decided yet(sound deading, comps and such). well, what my plan is on running these is to seal my trunk off from the cabin. for the box i want to forward fire it along with the port. from where i see it the baffle will sit 2-3 inches from the rear seat opening. the trunk space i have available is 40" wide, 17" tall, and about 29" deep. though for the size enclosure I'm going for about 6cu before displacement. i believe i have about 8-9cu before displacement total.

here is a quick sketch i drew up on a graph paper. each cube length stands for 1"

the red line is the opening space from the back seat. so just imagine the box sitting 3 inches behind it.

well, for the port i want it sitting in between the subs. inch by inch if i place everything right i could get a 6"x15" up to 6"x15.5"(counting 3/4mdf)

where i need help with is how long should i set my port or a recommended box volume? what I'm going for is tuning around 33-34hz. anyone have any idea what would be better or what size the port should be?

i've been searching for a very long time to see what other people run 2 XXX's 15's at but can not find anything. plus, "XXX" isn't search friendly.

[fbi90909 0]

bump anyone?

[///M5 2,833]

Not quite sure you have asked a question. You say you need help with port tuning and what frequency but haven't described your needs or desires. Choosing 33-34hz at the moment seems to be arbitrary from your post which is not the way to do it.

What are your needs and goals and why aren't you excited about RE's recommendations?

[fbi90909 0]

well i suppose my main question is would it be possible to create a box for 2 15's in a space of 38Wx17Hx28L, with a 6x15.5 center port opening?

iirc i read somewhere that when 2 speakers share the same chamber it is ok to cut down on some of the air space which is why i was looking at 6cu after displacement. i could bump up to 7-9cu using the spare tire areawhich is no biggie.

also what i need to know is a port opening of 6x15.5 enough for the 2 speakers?

i have already run my 15 in a 4cu@30hz mdf box and my 5.5cu@29-31hz fg enclosure and well the sub gets damn low. yet it's lacking some on the upper frequencies which is why i'd like to tune it a little higher.

[///M5 2,833]

?? lacking on upper frequencies. It is a sub and shouldn't play above 50hz anyways.

As for your question on limiting the box size with 2 subs, well its wrong they still need as much as they did alone.

If you want to keep the lows you had before, you have to keep the box volume where it was at as well.

Your port size is a little light but you will probably be okay.

--however, all of these need to be addressed before the whole box/port big enough can be

[fbi90909 0]

well i wasn't looking for frequencies in the upper 50's as my freq cut off from the head is set to 50hz, though where i feel it is lacking is in the 40 to 50 range. i find a lot of songs that have low beats in the 42+hz range are bare unlike the low beats in like the 33hz range.

i'm going to keep measuring around to see how much more air space i could gain from the spare tire area to gain the 8cu.

thanks for the input!

Edited December 21, 2007 by fbi90909

[creatormass 1]

?? lacking on upper frequencies. It is a sub and shouldn't play above 50hz anyways.

Where did you hear this? I've never heard of any enclosure with a cut off at 50Hz. Maybe an 80Hz cut off, but I've never heard of something that low.

[Acidburn 10]

?? lacking on upper frequencies. It is a sub and shouldn't play above 50hz anyways.

Where did you hear this? I've never heard of any enclosure with a cut off at 50Hz. Maybe an 80Hz cut off, but I've never heard of something that low.

It's common for people who don't want a localize-able sub to cross as low as 50Hz. I believe mine are at 40Hz right now.

[creatormass 1]

You'd have to have a good front stage to make up for the 40Hz-80Hz loss. I have my mid bass cutoff at 70Hz and the subs start at 80Hz with a cut off at 25Hz

[aznboi3644 2]

also depends on your crossover slopes

12db/oct - 18db/oct - 24db/oct

Edited January 8, 2008 by aznboi3644

[///M5 2,833]

?? lacking on upper frequencies. It is a sub and shouldn't play above 50hz anyways.

Where did you hear this? I've never heard of any enclosure with a cut off at 50Hz. Maybe an 80Hz cut off, but I've never heard of something that low.

Hear this??? Hell I know this, I wish my subs only had to play 30hz on down but regrettably my front stage isn't that good