PDA

View Full Version : 15" Re MX enclosure question



chief_bignut
12-07-2009, 01:22 PM
is 6.5^3 @32hz too big for an re mx 15". it will be going in a 2000 ford exloder. im just wondering if its too much for this beast or will it be enough room for it to breathe

t1990le
12-07-2009, 01:25 PM
is 6.5^3 @32hz too big for an re mx 15". it will be going in a 2000 ford exloder. im just wondering if its too much for this beast or will it be enough room for it to breathe

depends on the port area, how are you porting it? Does the 6.5^3ft incude sub displacement and port area?

x2o
12-07-2009, 01:29 PM
how much port area, and what kind of power will you be feeding it?

If those 6.5 cubes are after port displacement, general consensus will show that box is huge if you're giving it close to RMS power.

chief_bignut
12-07-2009, 01:30 PM
http://i79.photobucket.com/albums/j121/tarponcowboy/mx15.jpg
this is the quick drawing i did on reaudio's website tilt your head to the right its sub up port back all along the bottom of the box.
it will be on a USAMPS xt4000d for now. im getting a kicker zx2500.1 soon

chief_bignut
12-07-2009, 01:32 PM
depends on the port area, how are you porting it? Does the 6.5^3ft incude sub displacement and port area?

according to RE the sub displacement is .22 cubes so if anything ill be up in the 35-37 range if im not mistaken.

t1990le
12-07-2009, 01:34 PM
how much power are you going to feed it? and that box calc doesnt count for sub displacement, but you will still be at least 2 cuft over optimum conditions, the bigger the box you build, the more efficient the sub will become so if you need to build a box that big i wouldnt feed more than 1000-1200watts rms to it. that sub is rated for 1500 rms

S.B.C.
12-07-2009, 01:39 PM
3-3.5cu @ displacement w 12-16sq in of port per cu.

chief_bignut
12-07-2009, 01:39 PM
i believe the amp does 1500 on a good electrical and i think i have a decent electrical. 200 amp alt. 2 kinetik 2400's and 6 runs of 0gauge. i dont have a p[roblem being the box down a bit i just wanted to give it room to breathe. and still sound rediculously loud. what would you reccomend 90??

t1990le
12-07-2009, 01:52 PM
get as close as you can to the optimum specs. Id say go with about 4.5 cu ft if you want LOUD go with about 45-50hz on the port but if you want it to be dangerous and kill the lows go anywhere between 32-35 hz. My alpahs are in a 4.5cu ft box with aeros tuned to 34.5 hz and they move a $h!t ton of air and sound amazing :)

t1990le
12-07-2009, 01:57 PM
3-3.5cu @ displacement w 12-16sq in of port per cu.

THIS as a rule of thumb, you want to try and stay within 12-16 sq in of port for every cu ft worth of box. So 4.5cuft would like 54-72 sq in. :)

chaunb3400
12-07-2009, 02:00 PM
i believe the amp does 1500 on a good electrical and i think i have a decent electrical. 200 amp alt. 2 kinetik 2400's and 6 runs of 0gauge. i dont have a p[roblem being the box down a bit i just wanted to give it room to breathe. and still sound rediculously loud. what would you reccomend 90??

If its the old XT line it may do 800rms on a good electrical, dont be fooled ;)

chaunb3400
12-07-2009, 02:01 PM
how much power are you going to feed it? and that box calc doesnt count for sub displacement, but you will still be at least 2 cuft over optimum conditions, the bigger the box you build, the more efficient the sub will become so if you need to build a box that big i wouldnt feed more than 1000-1200watts rms to it. that sub is rated for 1500 rms

It has a 4in coil, it can take alot more then 1500rms ;)

t1990le
12-07-2009, 02:03 PM
It has a 4in coil, it can take alot more then 1500rms ;)

lol i figured it might but i wouldnt wanna jeperdize someones warranty :)

chaunb3400
12-07-2009, 02:05 PM
lol i figured it might but i wouldnt wanna jeperdize someones warranty :)

If he is willing to pay retail for a MX then who needs a warranty, cuz you got the money to cover it :laugh:

t1990le
12-07-2009, 02:12 PM
If he is willing to pay retail for a MX then who needs a warranty, cuz you got the money to cover it :laugh:
:laugh: i need a third Alpha and another 1750 and some mdf :greedy: christmas is coming up and ill pay shipping if op wants to buy :laugh:

chief_bignut
12-07-2009, 03:28 PM
ok i ended up going 4.75^3 after sub dispacement right around 32hz. will begin cutting and assembly this afternoon. will take pics and post em up if anyone is interested to see how this turns out

chief_bignut
12-07-2009, 03:30 PM
the mx isnt new. its been reconed by team psi i believe. i bought it used from dman_1 on caco. i think hes here too. if it blows ill simply have it reconed again. no biggie

PV Audio
12-07-2009, 03:33 PM
If I can be honest, and I know I'll get shot for this, but that speaker isn't optimized to work ported in the slightest. Richard Small, the guy who you in part owe all speaker parameters to, made a guideline called the EBP which is Fs/Qes. A EBP below 50 means the speaker should be sealed and around or over 100 means it should be ported. This speaker has a EBP of 37. It has that because it's electrical Q, or in a simplified way, how free the cone is to movement due to the electrical parts, is very high. A high Q of anything means that something is very free to resonate or oscillate. For example: if you strike a bell and it rings very briefly will have a very low Q while if it rings for hours, it has a very high Q. This speaker's Qes isn't low enough to warrant a ported box because it could break up easily.

I'm not saying to not port it since 98% of ca.com is hellbent on doing it, I'm just saying that you might want to consider what enclosure the speaker was designed to be in. :)

PV Audio
12-07-2009, 03:38 PM
Also, that speaker is going to have a MONSTROUS spike in group delay around tuning frequency which I don't know if you're a SQ guy or not, is fairly undesirable. Just to make my point, if you do a sealed box at 3.28 cubic feet net with moderate damping inside (fiberglass, polyfill, whatever), you'll have a rolloff point of 34.47 and it will be flat as a 5 year old girl's chest until that point. If you port it at 5 cubes, you'll end up with a rolloff of 26.21hz. You're thinking hey, that sounds great! Yeah, no. The ported box is going to be very peaky and it only rolls off tha tlow because at around 40hz, you'll have about 7-8db gain which will correspond to incredibly muddy sounding bass along with a HUGE amount of group delay. With the sealed, the the group delay and phase are both flat all across while the ported boxes have horrible plots: sharp bends, undamped oscillations, and other bad stuff. The only way you can get a flat response with that speaker is to throw it in a very large ported box tuned low, aka, 8.6+ cubic feet tuned to 17hz. What is happening is that the speaker has such a low resonant frequency that it needs a ported box with a Q to match it. Smaller boxes have a Q that's far too high and they end up being peaky. Just think about it or if you don't understand something I've said, just ask. :)

chief_bignut
12-07-2009, 03:42 PM
im not all that big on sq. dont get me wrong i like it to sound good but i like it to be loud as well and at the same time still be able to pick up the lows. i picked up this 15" as a temp sub. i may find another non working mx and send them both in to team psi and have them make identicle subs and go from there.

PV Audio
12-07-2009, 05:37 PM
Alrighty, just wanted to let you know :)

chief_bignut
12-10-2009, 01:43 AM
ok so im re-doing the design before i cut anything out. my external dimensions are 35*20*19 which gives me an internal volume of 7.69^3 if im not mistaken so then after sub displacement (.22^3 feet) im left with 7.47=7.5 im rounding up. ok so with a slot port 6x20 (120 sq " of port) and a length of 23.25" im right around 32hz. if i did the math right. so the external measurments of the port tell me that the port takes up 2.09^3 which leaves me with an internal volume of 5.41 after port and after sub. is this still too big of a box for the sub?? anyone correct me if im wrong on these measurments plz. any input is helpful

chief_bignut
12-10-2009, 12:35 PM
Anyone? Come on guys