1243d with bandpass help!

[iggiafrica 10+ year member]

Hello! Im new to the forum...kinda. ive been living off of everyone heres help for a while now, and decided it was probably time to make an account instead of just sniping the forums haha.

Anyways, before everyone starts flaming me saying "just do sealed/ported, bp ***** etc" i know the differences, i know what i want and i want a 4th order...i had one for a single 12 oldschool fosgate that put out 300 watts and sounded like 600 with an excellent frequency range!

So now ive bought 2 alpine 12s, 2 mrp m500 amps and have unlimited mdf to work with, i just cant seem to get my measurements to produce what i want.

Id made a box last week but the ports were 4.25" wide x 22" long and it had little efficiency below 50hz, but destroyed everything above that!

Id just like help building one that will have a nice rumble around 31hz with good range. Ive tried winISD and i guess im too illiterate to understand it fully... Ive got 15"h x 32" w x 29" L to work with...i know its doable, im just having a hard time understanding port widths and stuff... I guess it has the same effect if it was short and wide as if it were thin and long? Im not really understanding it... If someone could explain it to me i would be so greatful!!

Thanks in advance!

-iggi

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[DoesDad 10+ year member]

Can't help. Don't like bandpass.//content.invisioncic.com/y282845/emoticons/imo.gif.3a57bcc70a4835dc53e86ffae1a0b041.gif

 

[iggiafrica 10+ year member]

Ive seen alot of people say that lol!

Well could you explain port sizes and difference to me for just an average ported box?

 

[DoesDad 10+ year member]

The box builders on here are usually pretty helpful. You know you can get a design for really cheap. Maybe 15-25 bucks (don't quote me on that). That would be the way to go for you cause it sounds like you've got some construction skills. Pro-rabbit, mobile enclosures, Donh, buck, etc....

 

[iggiafrica 10+ year member]

I may end up doing that, but id still like to know what makes things do what they do...i always love learning the reasons behind how things work haha. If i did have someone design it for me theyd probably have to explain why the port would have to be the size it is and what that would cause (lengths in soundwaves and so on) im just that kinda guy haha

 

[DoesDad 10+ year member]

There's actually a couple acoustic guys on here (can't remember names). Actually think one or two might be schooled in it. They'll probably chime in too. I can't help you my man. I just order boxes. Lol! Tell the guy how much room I have, what I want it to do and place my order. Bada bing.

 

[wenn_du_weinst 10+ year member]

I'm confused on why your stuck on bandpass?

 

[CAT MAN 5,000+ posts]

bandpass isnt that bad. you just need to know what you're doing

 

[iggiafrica 10+ year member]

Exactly! Im just stuck on bandpass cuz i know the potential of it... I want to be able to understand it. I slapped a sealed box in my rig for the time being but i miss the rumble... Sq is great but im an spl guy and 4th orders intregue me..i want to know it all haha

 

[iggiafrica 10+ year member]

So i drew up a design for a box.. sealed (if i remember right) is 1.23^ft3 per sub, the ported section before the ports is 3.29^ft3, and the ports (2) are 30.75 long, 13.5 tall and 2" wide...what kind of tuning am i looking at? And how do i figure it out from these parameters? (I prefer doing the math by hand rather than using programs lol) so...what do i have?

 

[KyleBechtold 5,000+ posts]

its all realitive.. the sealed to the ported section is realitive along with the tuning.. I just built one for two t3s I did 2cubes ported 2.5 sealed 18" long port 40" of port..

 

[TaylorFade 10+ year member]

If you have unlimited MDF to play with, just start building until you get it right. Lol.

30.75" long? What are you tuning to? 30hz? BP's don't work like regular ported. MOST tunes are ~ 50hz. Not all, but most.

If you don't want to pay someone, I'd start here... 1cf each sealed, 2cf each ported tuned to 50hz. This is a pretty standard ratio. Bigger ratio will get you a bigger peak around tuning. Smaller ratio will flatten the response out. Generally speaking.

Here's a port calculator for you. I don't know anyone that can do the tuning by hand.

Subwoofer Enclosure Calculators, Fraction to Decimal, Parallel, Series, Port Length and Volume Calculators

 

[CAT MAN 5,000+ posts]

If you have unlimited MDF to play with, just start building until you get it right. Lol.
30.75" long? What are you tuning to? 30hz? BP's don't work like regular ported. MOST tunes are ~ 50hz. Not all, but most.

If you don't want to pay someone, I'd start here... 1cf each sealed, 2cf each ported tuned to 50hz. This is a pretty standard ratio. Bigger ratio will get you a bigger peak around tuning. Smaller ratio will flatten the response out. Generally speaking.

Here's a port calculator for you. I don't know anyone that can do the tuning by hand.

Subwoofer Enclosure Calculators, Fraction to Decimal, Parallel, Series, Port Length and Volume Calculators

or 1.3 and 3 at 46.....because big 4ths are loud 4ths

 

[TaylorFade 10+ year member]

or 1.3 and 3 at 46.....because big 4ths are loud 4ths

Big 4ths are peaky 4ths. He's only got like 8 cubes anyway.

 

[CAT MAN 5,000+ posts]

Big 4ths are peaky 4ths. He's only got like 8 cubes anyway.

hence why they get loud .... only 8 cubes he could do 1-1:5 ratio if he wants a more controlled response.