need help building box today

[Cruzer 10+ year member]

I just got a 15" DC lvl 3 with lvl 4 soft parts.

Im looking to build a ported box today and i need some help on what size and tuning.

DC suggests 3 cubes for lvl 3 and 3.25 cubes for a lvl 4, will that be good?

i listen to heavy metal 90% of the time and 10% rap/hip hop, im really worried about SQ, what should i tune for? is 33hz good? fine?

also just for the record what would be best size for sealed? lvl 3 is 2 cubes, lvl 4 is 2.75, but are those big enough, too big, just right? i have it in a 2.4 cube and its great on like late night tip, but on heavy metal does not sound too good, so bad that i wanna go ported, or try different size sealed.

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[hispls 5,000+ posts]

I'd suggest tuning closer to 40 if you want a bit more punch from bass guitar and drum kicks. The difference between 3.25 and 3 cube feet probably won't be much, but go bigger if you can as it will help efficiency and low extension.

If you're using round port(s) you can tune low and cut 1" at a time off of them to tune higher and test to see if you like the change in sound. Or use some other method to easily change tuning (slot port with inserts or multiple round ports and seal one up for lower tuning, etc.)

 

[Cruzer 10+ year member]

for now im doing slot port as i dont have the other port supplies yet.

i know there is not much difference between 3.25 and 3, but i guess what im worried about is, i want to fit it in this snug spot in my truck, but i can only fit like exactly 3-3.25 cubes. but going bigger would make it sound better huh?

i do listen to heavy metal almost exclusively so if 40 is better, or even 38, im deff open to it.

 

[Cruzer 10+ year member]

here are 2 designs i have came up with, can i get by with this or will the sq not be very good?

(click to see bigger, they are still small, sorry!)

View attachment 26520212View attachment 26520213

should i go bigger and deal with it not fitting, fight to figure out a way to make it look right, but enjoy better sound?

also is there a diff program, or diff way to figure up this info?

 

[Cruzer 10+ year member]

the biggest box is the 3.238 @31.5hz looks like its a winner imo. from what im reading 32 hz is a good tune for overall, plus after displacement ill have an actual 3 cubes as recommended

 

[T3mpest 10+ year member]

what port size does that give you?

 

[Cruzer 10+ year member]

http://a.imageshack.us/img691/6742/subbox.jpg

just click it, then zoom in, should be actual size of picture

hopefully this one is bigger, its got a 2.5" wide port

 

[stangman67 10+ year member]

Port is going to be too small. You want a lot of port area with a 15

 

[Cruzer 10+ year member]

y is it too small? box size is fine, tuning is fine.

what will it do, come out delayed or something?

 

[stangman67 10+ year member]

Port noise. That is less than 30 in of part area.

 

[Cruzer 10+ year member]

what do i need then? is 3 fine? i have a 3" port one designed, 3.126 cubes @35 hz

if i go 3.5 port it will be tuned for 38 which might still work ok

if i go 4 port its tuned for 40 haha

 

[T3mpest 10+ year member]

lots of things. The thing to remember is that the port actually works by creating a mass of air inside the box that the speaker can excite that will resonate at the frequency you want. However, all that pressure has to come out the opening. If the port is small, you have a smaller mass of air moving which ultimately means less SPL. Once the air moves so much through the opening it will begin to get turbulent and no longer act as a proper port. You'll get what is called port compression. Basically the woofer will still move more, but since the port is already moving as much air as it can through an opening that size, your not getting any more SPL at that frequency like you should. So at higher volume levels when the woofer really begins to excite the port, you'll get a different frequency response since the port will stop adding output at the level it should. The second issue with this is that the air getting compressed will make a "wooshing" sound as it tries to leave the port. Since the box is right behind you that will be audible, so that's a no go. General rule is 12-16sq in. of port cubic foot of box room. You are at the bare minimum with no flaring on the port, it'll chuff for sure since your using a nice sub and high power.

Listening to metal what's going on between 50-300hz is more inportant than 40 and down. If you tune high you will increase the top end a bit, but you also have a lot fo group delay in that region. Yeah, the kick drums will be louder (not necessarily realistic), but they will be out of sync with the rest of the sound and it often sounds sloppy and muddled. Imo for rock you want to tune low to get the group delay out of the region that it's audible on rock music. I've done LOTS of boxes for people who like rock and they are usually tuned at 30hz or lower in some cases. It gives you a decently flat response and the group delay is low in magnitude as well as much lower in frequency. Plus when you play rap, you can tell it's ported as it crushes low notes in a way sealed boxes won't lol. Trying to tune at 40 for a rock music box is like trying to boost the 1 band eq that says "treble" on a stock stereo to get cymbals to sound good. Yes, part of the cymbal will be emphasized, but that doesn't make it realistic nor soudn good.

3.15 at 35 is a decent compromise. IMO, I might start thinking about doing an external aero port. It won't look as pretty, but it'll sound alot better and it'll solve your space vs tuning issue. Plus you can keep chopping it down to try different tunings if you dont' like how it sounds.

 

[RAM_Designs 5,000+ posts]

Imo for rock you want to tune low to get the group delay out of the region that it's audible on rock music. I've done LOTS of boxes for people who like rock and they are usually tuned at 30hz or lower in some cases. It gives you a decently flat response and the group delay is low in magnitude as well as much lower in frequency. Plus when you play rap, you can tell it's ported as it crushes low notes in a way sealed boxes won't lol.

I've tried explaining this to people before but they never believe me that lower tuning is better for rock because of the need of the double kick drums being accurately reproduced. Otherwise it just sounds off and gets annoying after a while.

 

[DonH 5,000+ posts]

I've tried explaining this to people before but they never believe me that lower tuning is better for rock because of the need of the double kick drums being accurately reproduced. Otherwise it just sounds off and gets annoying after a while.

x3! but the customer is always right....

also op do NOT use the RE calculator please. i have a few designs which could suit your needs. pm me if you would like a design

 

[Cruzer 10+ year member]

i actually want to go aero port but dont know much about it etiher...

only reason im looking at the slot port is a friend is gonna help me build it, and he has only done slot port as well