Bandpass help needed for a Blowthrough!!!

[SPLluminator 10+ year member]

Im trying to design my first bandpass box for my ford ranger. The equipment used will be 4 12" type r's and 2 IA 20.1's. I am fairly certain im am doing this right but I would like someone to give me some pointers if they are willing. Here's the specs for the sub:

Qts-.47

Vas-1.5ft

Fs-28hz

Heres the specs on the box I came up with:

Vf-2.6 cft

Vr-3.91 cft

Fb-44.5 hz

Qbp-.75

Passband-28hz-70hz

Gain- +1.85db

If this all looks ok then my next question would be about the port size/tuning. I used this calculator to figure out recommended minimum port space and it tells me I need 381.83 in^2. This would mean my port would have to be 166.27 inches long which is not possible with the space allotted in my bed. Can I go with a smaller port or is this going to cause port noise? I guess im just kind of confused with their recommendation of more than 380sq inches of port... Any help would be much appreciated!!!

Click to read more...

 

[galacticmonkey 5,000+ posts]

Send me a PM. I can get this thing real loud.

 

[groundpound4200 5,000+ posts]

Looks like the rear chamber is a little large.

 

[galacticmonkey 5,000+ posts]

Yeah, the numbers you posted up arent even remotely close. All of those graphing programs dont do it for bandpass boxes. You need to go by experience, and Ive designed/built a ton.

Usually I charge for designs when I do them (havent done many lately, except for one for a customer the other day on here), but this one Ill do for free just because I like bandpass blowthroughs and want to see you be impressed with what those little subs can do.

 

[SPLluminator 10+ year member]

Im more interested in learning as I enjoy doing designs and enjoy building my boxes. But if you could come up with a design or walk me through even the front chamber/rear chamber volumes and tuning thats would be awesome. The reason I would like to do as much myself as possible is because Id like to be in the lanes next year for bassrace 149.9 and I like having pride in doing work myself. I will gladly accept all advice and I appreciate your help!

 

[galacticmonkey 5,000+ posts]

Ok, well first off what are tour expectations of this system? Just very day driver with an ability to play every note? Daily that you want to drop super low? Something that more meter oriented? Once we figure this out, we can go from there.

 

[SPLluminator 10+ year member]

Ok, well first off what are tour expectations of this system? Just very day driver with an ability to play every note? Daily that you want to drop super low? Something that more meter oriented? Once we figure this out, we can go from there.

Somwhere in the middle, Id like as flat of a response as possible, but it doesnt need to have a huge passband. My Ideal goal is to bassrace a 149.9 below 40 hz if its possible, but then again if I go too low ill just end up breaking **** lol.

 

[galacticmonkey 5,000+ posts]

Either way, thats a bunch of power for Type Rs. Id be careful with them thermally.

I could help you get a design thats super efficient, but it will have a pretty steep drop off at your low end. Will play as high as you want it do, and still get decently low, but once you hit the bottom end, it will fall off like a rock. Or you could have something where you give up a little efficiency and gain a much smoother roll off on the bottom end. Which would you prefer? Also, what are your max dimensions, and how big is the hole the port needs to go into?

Keep in mind the goal of bassracing a 149.9 with 4 $100 12s is going to be a tough one. Youre going to need more power than the woofers can hold reliably to do it.

 

[brodeisel 10+ year member]

i would try to find some other used subs on the forum unless you have those subs already.

 

[SPLluminator 10+ year member]

Well originally I wanted to run 6 but I didnt think I had the space. I certainly have the power though. The max dimensions are 16" H, 40" W, and its a 6' bed. However, I need some extra room in the bed for amps and batts. I could easily get by with 5'. My main goal is just to bassrace 149.9, I honestly dont even care if I run type r's as I dont have them yet but I would like subs that will get low. Where would the sharp cutoff be on the low end? if its at/around 28-30hz I would be fine with it, but I like my lows. My cutlass had 4 15" Sonances tuned at 27hz and I enjoyed it a lot. Only reason im rebuilding in a new car is because my cutlass is now totaled..

 

[brodeisel 10+ year member]

i know this is a forum boner but some sundown audios 12s will be good or skar 12s. Sundown get louder Skar get lower. if i remeber the sundown require less room also.

 

[galacticmonkey 5,000+ posts]

Something like a pair of 15s would be good. Like I said, the 149.9 is going to be real tough. You could get away with the 15s if you went with a slanted baffle. Id do the baffle all the way in the back, with the subs in a smaller sealed chamber and a big ported chamber up front (the majority of the bed), with a big port. I could sketch something up to give you an idea of something that will work. Is this an S10? Ranger?

 

[SPLluminator 10+ year member]

Its in a Ranger, Thats the main reason why I wanted to go with 12's is because that way I wouldnt have a slanted baffle. If I have the room for 6 12" type r's I would certainly go with that route even tho money is sort of an issue lately. The absolute max height is 16.5" and with 3" of wood(1.5" on the top/bottom) that really only gives me 13.5" of height. Hence going with 12's.

 

[galacticmonkey 5,000+ posts]

The Type Rs would be awesome for music and demoing, but if youre looking for something that is going to still play music but be much more efficient and meter, you want less subs. 2 15s with a slanted baffle really would be the way to go here. Something like a pair of BTLs with some power on them and you would be doing great.

This is a sketch I threw together real quick. In doing blowthroughs, this is the sort of design that usually gives the best number. Ive had 2 boxes like this and they were super efficient.

Like I said, just a rough sketch, its around 1.3 sealed per sub with a 12.5 cube ported chamber. Big port. I have an Avalanche, and Ive done 2 setups like this in it. First was 2 BTL 18s and second was 2 Ascendant Chaos 18s. The BTL 18s has 400w per sub (MB Quart DSC2000.1 at 2ohm with the gain turned down) and did a 146.x sealed up playing music at 41hz. This was box like 4 sealed, 18.5 ported with 425in^ of port tuned around 48hz. With this big port and higher tuning, the efficiency really showed. On a DSC2150 (150x2) it did a 144.x sealed up. You could put your hand on the subs playing it full tilt, they werent moving even 1/8", but on the dash it was still in the mid 40s.

I built the second box mostly the same. It was like 4.5 sealed, 19 ported. 400in^ of port @ 41hz. This box, with 2 Chaos 18s and an Audiopipe 3k did a 150 @ 37hz legal. Both boxes played to around 27-28hz and then fell off like a rock.

Just recently I had 4 PSI 12s in a box like you would need if you went with 4 12s. It had 4k on it, and sounded awesome (was my favorite for demoing). It was 4 cubes sealed, 7 ported, 95in^ of port tuned somewhere in the mid-upper 30s. It would play down to about 20hz rock solid, and peaked at 146 @ 30hz. It would do a hairtrick with both doors open. Down low, it sounded much more impressive than the other 2 setups, but playing regular music and on the meter the boxes built for efficiency whooped it.

If youre looking for numbers, Id really suggest going with the 2 15s. Just get a nice pair of 15s and run a pair of amps at .5 each for now, then down the road buy another pair of 20.1s and strap at 1ohm each. This is what Id do if I was shooting for numbers in that truck.

 

[galacticmonkey 5,000+ posts]

Found a pic of the second blowthrough, for the 2 Chaos 18s. Here is the box. Its 49.75" wide, 21.5" tall, and 63.5" deep. Was a huge box.