Box help again

[bbeljefe]

OK I finally see why I wasn't understanding this I think I was taking the total internal height of the box and dividing it by 134 it tuned to 38-40 well I want it tinned to hit

so 134/20.5

You are taking what I'm using as my port length not the total internal height.I would like it to be the hardest hitting loudest bass possible so tunning I'm up in the air whatever is best. So when calculating port I take what the first part of the port wall length will be not the internal height

Again, let's back up because we've gotten off on different pages and, as you can see above, I had some bad info and dispensed it so forgive me if you will.

If you're looking for straight up SPL then you want the box tuned high and, you want it small to help the driver handle more power. If this is a daily box, I wouldn't tune so high that it sounds like shit on music but that's for you to decide. I would say 37-8 Hz is a good number for SPL while still allowing the driver to reach down into the low 30s. If you look at the graph above, those are 4 cube 37 Hz boxes. At that volume, you have about 1dB of acoustical gain around tuning but it falls to -3db before you get down to 30 Hz. If that's good, then great... I would use the 85in² port. Tuned at 40 Hz, you'll get about 2dB of gain but your -3dB point will be around 36 Hz... so think that through. Also consider that in the car, those frequencies will drop slightly.

I wouldn't make it much larger for an SPL box and this woofer doesn't seem to like anything smaller.

[robby512]

Ok so first off again thank you for your help. I understand more now and can see also how to use winisd better.

I don't have the expirence you may have and I deffently don't have 10 years of experience in this I maybe have 1 full year so some of this is still like a different language.

And if you have a better suggestion please say so l

I have a hifonics Brutus 1200 watt amp running to it if I didn't state that (not the greatest power but still power) so I was thinking to overcompensate the lack of quality power with a bigger box and maximize efficiency of the sub threw the box. Now I am I'm going to post a picture of a box I did up well 2

Green= 5.5 cubes 37 hz

Yellow= 4 cubes 37 hz

My question is the groups delay seems reall high on the green is it to much where it will cause port noise?

[robby512]

[robby512]

and lets just use green for example

5.5 wide port

15.5 long for first wall going down

then the extension off that needs to be 6.75 long so the vent length will match at 22.23

then total port area will 122.37 so is that good im sorry if i got it wrong and am still missing it i think i got it not to sure if not please just tell me exactly what i should do.

seems like i took a 5 minute thing and made it a half a day event for myself trying to figure it out

[fecupe2001]

oh i get it, you use your little program to plot how the response is going to be, don´t you worry, i also calculate my port area based on xmax and a few other things that i´m not going to tell here, if you want to believe that i don´t know what i´m talking about, that´s fine, all the records, loud cars and few hundreds of trophies i´ve can speak for me, i ain´t going to say my formulas or anything like that, and for the record, that program and also the bass box pro are just funny, they always plot that big ass curve when you use bigger and bigger port.

And for the record, i do have many and many hours of testing, and also golfing, which can surely hit under 70 few times a year, i guess i don´t only know about boxes but also golfing, i don´t quit on anything until i´m good at it i guess, whenever you need help on golf just let me know, cheers...

OP: if that box doesn´t sound like you want which i´m pretty sure is going to be the result, send me a PM, i can help you out a lot with that sub, i was bass racing a 149.9 with a pair of those subs on a 3K peaking at 41 hz, and also, broke the old panamenian street B record with a single sub like yours on a box that played music very nicely with an smaller port than 137 SQ , good luck...

[bbeljefe]

For port noise you're more concerned with the vent mach. Below .16 will be a noise free port, theoretically. Your group delay with that volume isn't much but it is a bit more than the 4 cube box, which is (as far as I can see) the ideal size for that woofer and your goals.

As far as ports are concerned, let's be clear about the two properties we're dealing with. First is port area and second is port volume. Port area is only a measurement of the surface area of the opening of the port. It has nothing at all to do with how long the port is or with tuning frequency, save the fact that port area does affect on length... but forget about that for now. In your original post you stated that the box was 21.5" tall. I will assume that the slot port you plan is going to be running along that height, which means that the actual port dimension will be X by 20". If we've decided that 85 square inches is the best port area for this application, then to find the value of X or, port width... 85 ÷ 20 = 4.25.

As for port volume, that's where tuning and length come into play. For a 4 cube box tuned at 37 Hz with the port area above (85in²), the port needs to be 26.21" long. In order to find out how much volume that port will occupy, we would take the height and width of the port and multiply them by the length. Height is easy... 20". Width is almost as easy, in that it's the port width plus the thickness of the inside port wall, which is .75"... so width is 4.25 + .75 = 5". So now we take those and multiply them... 5 * 20 * 26.21 = 2621inⁿ or, 1.52ftⁿ.

Now you know that for a 4 cube box you need 4 cubes plus 1.52 cubes plus woofer displacement (.15 cubes). So.... 5.67cubes total internal volume.

As for how to measure the port length through an L, again, mark a line through half the port width and measure it at 26.21". Transfer that line to the inside wall of the port and cut accordingly.

Here's a drawing I made on a piece of scrap I have.... the dashed line is the line you would use to find the correct port length or more accurately, the correct length to cut the port inner walls.

[bbeljefe]

oh i get it, you use your little program to plot how the response is going to be, don´t you worry, i also calculate my port area based on xmax and a few other things that i´m not going to tell here, if you want to believe that i don´t know what i´m talking about, that´s fine, all the records, loud cars and few hundreds of trophies i´ve can speak for me, i ain´t going to say my formulas or anything like that, and for the record, that program and also the bass box pro are just funny, they always plot that big ass curve when you use bigger and bigger port.

And for the record, i do have many and many hours of testing, and also golfing, which can surely hit under 70 few times a year, i guess i don´t only know about boxes but also golfing, i don´t quit on anything until i´m good at it i guess, whenever you need help on golf just let me know, cheers...

OP: if that box doesn´t sound like you want which i´m pretty sure is going to be the result, send me a PM, i can help you out a lot with that sub, i was bass racing a 149.9 with a pair of those subs on a 3K peaking at 41 hz, and also, broke the old panamenian street B record with a single sub like yours on a box that played music very nicely with an smaller port than 137 SQ , good luck...

Yeah, well... I'm an astronaut in my spare time and, and, and, oh yeah... you still haven't made an argument supporting your assertions.

Be sure and keep those secrets safe man.

[robby512]

Um one you forgot your flux capacitor that helps your space ship go back in time when you hit 88 mph to the time when because it's dump is a valid reason oh

wait neither of those things count for anything other than a big joke

Next how did you find this 26.21 number

[bbeljefe]

Um one you forgot your flux capacitor that helps your space ship go back in time when you hit 88 mph to the time when because it's dump is a valid reason oh

wait neither of those things count for anything other than a big joke

Next how did you find this 26.21 number

In WinISD I modeled your woofer in a 4 cube box with an 85in² port at 37 Hz. That's the port length needed.

Oh and, my spaceship only goes back in time when I put Keystone Light in it. If you don't believe me, ask Hellbilly.... he knows. :-P

[robby512]

Also in the spaceship I built a 13 cubic foot box for 3 tweeters running a boss audio 4000 watt amp and it hit a 190 db.

Oh ok so my port in this box should be 26.21 long at 4.25 with a total cubic feet of 5.67 including port and all