4th order blow-through build help, 6 18's

[IndianaBassHead]

anyone?

Box rise is dependent on to many things to calculate it as having a lot of it without actually measuring it. However, yes, with all of those on one amp your amp will see the "box rise" of all the subs instead of dividing it up between lots of smaller amps.

For 15s I would say CVX is being pretty generious on box space. I would go no more than 2 cubes per sub. Especially if its one big chamber. You have to figure in one big chamber that each sub isnt going to divide the space up and say "okay I have 2.5 cubes of this because there is 15 cubes and 6 of us." Generally in a large common chamber as 6 subs would have you can make it a tad smaller. The 18s I would say to put them in roughly 3.5 max each. Then from there make your front chamber accordinly. The higher the ratio you are generally looking at a more peaky box with a smaller bandwidth, The smaller the ratio you are looking at more bandwidth but not as loud and peaky. Remember you can always stuff the rear chamber of the box with polly fil if you need it to have more space for a lower fs in the rear chamber.

Thanks for the info! I think I'm going to stick with the 18's if I can fit them. I would like to do around 3 cu. ft per. Would I be better off with all the woofers in an 18 cu ft box or 6 seperate 3 cu ft boxes? One big box would be much easier but is it as effective?

Single box is fine. Only difference with a single box is like I said its not like each sub sees the exact space that its divided up to be. Also if one blows it will become a passive radiator and possible cause some unloading. But you would notice if one blew. I've been told by a friend that knows OA products pretty well that they like 2.75 cu ft ea and tune the front chamber between 48-54. Somewhere between a 2.5:1 to a 3:1 ratio if you can fit the higher ratio.

Ok, once again, thanks a lot. I will see exactly how much room I have and come up with a rough design. I'll post it up once I'm finished. I just have to learn how to use winisd first lol. But I will definitely brace the box really well. What do you recommend for bracing? Seems like you know fourth orders really well. I have seen so many different types of bracing with 4ths.

[Wildbillpb]

Ok, once again, thanks a lot. I will see exactly how much room I have and come up with a rough design. I'll post it up once I'm finished. I just have to learn how to use winisd first lol. But I will definitely brace the box really well. What do you recommend for bracing? Seems like you know fourth orders really well. I have seen so many different types of bracing with 4ths.

I like to use steel for bracing and connect it to the wood with PL375 (which is a construction adhesive) and lag bolts or a bolt and nut. However you could also use 2x4s with glue and screws. I just dont like 2x4s in the front chamber for looks and steel is stronger. Alot of people like dowel rods but I dont like them. I feel they dont hold so well because a 1" circle of glue on a big baffle isnt a lot. All thread works well also but I dont like it as up and down bracing only front to back and side to side, unless you put the all thread through the bottom of the bed and bolt it down there as well. Just hard to bolt down all thread on the bottom of the box because it would just be sitting on it.

[412 CVX]

Ok, once again, thanks a lot. I will see exactly how much room I have and come up with a rough design. I'll post it up once I'm finished. I just have to learn how to use winisd first lol. But I will definitely brace the box really well. What do you recommend for bracing? Seems like you know fourth orders really well. I have seen so many different types of bracing with 4ths.

I like to use steel for bracing and connect it to the wood with PL375 (which is a construction adhesive) and lag bolts or a bolt and nut. However you could also use 2x4s with glue and screws. I just dont like 2x4s in the front chamber for looks and steel is stronger. Alot of people like dowel rods but I dont like them. I feel they dont hold so well because a 1" circle of glue on a big baffle isnt a lot. All thread works well also but I dont like it as up and down bracing only front to back and side to side, unless you put the all thread through the bottom of the bed and bolt it down there as well. Just hard to bolt down all thread on the bottom of the box because it would just be sitting on it.

Think creatively my friend! if you double layer the whole box (not suggesting anything one way or another) then you can drill in 3/4 of an inch with a hole just big enough to fit a nut and washer, then in the second layer, drill a hole just big enough for the all thread to pass through.

i sketched out the same concept sort of thing for another box.

[Wildbillpb]

Yeah but cvx how would he get under the second layer just enough to put a nut there if its a wall build and its on his floor? Thats why I said drill it through his floor and put the nut there. He could always drill the hole and then mount it to a piece of wood and then make sure the nut lands in the hole with a small peice of wood on top of it like your picture and then glue the peice of wood down but it seems like the time consuming way to do it and not as strong as bolting it to your entire bottom piece instead of the 4x4 block that you glue down.

Unless of course this is going to be a slide in box. Which in that case I would still recommend drilling through the floor and getting a nut on the bottom side of the floor on the all thread so the box doesnt go anywhere.

[412 CVX]

glue and fiberglass down a bigger block. it will be plenty strong, and won't take up all that much room in the enclosure.

[412 CVX]

i do agree though. keeping the box in place will be the challenge here.

[IndianaBassHead]

Yeah but cvx how would he get under the second layer just enough to put a nut there if its a wall build and its on his floor? Thats why I said drill it through his floor and put the nut there. He could always drill the hole and then mount it to a piece of wood and then make sure the nut lands in the hole with a small peice of wood on top of it like your picture and then glue the peice of wood down but it seems like the time consuming way to do it and not as strong as bolting it to your entire bottom piece instead of the 4x4 block that you glue down.

Unless of course this is going to be a slide in box. Which in that case I would still recommend drilling through the floor and getting a nut on the bottom side of the floor on the all thread so the box doesnt go anywhere.

i do agree though. keeping the box in place will be the challenge here.

I was originally thinking about using 1" square steel tubing welded to a steel plate with bolts going to the top of the box and the bottom of the truck bed. Do you think that would suffice? And I don't have a forklift handy so this thing has to be built in the truck. Which I am not looking forward to lol.

[FutureFuzz 26]

i didnt read all the post, but 48hz sounds like a fair tuning frequency. however things seem pretty contradicting to me.

its in a truck (i presume extended cab with rear seats) so the cabin gain is going to be high and peaky; probly 50ish maybe even 55hz. which is good for SPL comps

but you said you want it to drop low.. this is where i see the biggest problem, with the combination of the high cabin gain and high Fb (plus 4th O BP tends to be pretty peaky aroung the tuning frequency) idk how low it will actually go. not to mention, your subsonic should be set 5-7 hz below your enclosure Fb. OTOH im willing to bet you pull some crazy numbers around 50hz

[IndianaBassHead]

i didnt read all the post, but 48hz sounds like a fair tuning frequency. however things seem pretty contradicting to me.

its in a truck (i presume extended cab with rear seats) so the cabin gain is going to be high and peaky; probly 50ish maybe even 55hz. which is good for SPL comps

but you said you want it to drop low.. this is where i see the biggest problem, with the combination of the high cabin gain and high Fb (plus 4th O BP tends to be pretty peaky aroung the tuning frequency) idk how low it will actually go. not to mention, your subsonic should be set 5-7 hz below your enclosure Fb. OTOH im willing to bet you pull some crazy numbers around 50hz

It's actually a crew cab truck. I'm not sure what the cabin gain would be since it's a crew cab. I want it to be able to hit the lows more than anything. Good numbers would be nice but it's not worth it to have an SPL vehicle in the area where I live. The only events we have around here are Slamology and a couple Iasca events a year. It would be cool to compete, but with only 4k watts, I wouldn't stand a chance anyway in my class. So there's no point. But if I lower the tuning to around 42hz, I was hoping I'd be able to hit the lows even with cabin gain. I really don't care to lose 47-50hz output. I only listen to rap music and the majority of it is Decaf.

[Wildbillpb]

Yeah but cvx how would he get under the second layer just enough to put a nut there if its a wall build and its on his floor? Thats why I said drill it through his floor and put the nut there. He could always drill the hole and then mount it to a piece of wood and then make sure the nut lands in the hole with a small peice of wood on top of it like your picture and then glue the peice of wood down but it seems like the time consuming way to do it and not as strong as bolting it to your entire bottom piece instead of the 4x4 block that you glue down.

Unless of course this is going to be a slide in box. Which in that case I would still recommend drilling through the floor and getting a nut on the bottom side of the floor on the all thread so the box doesnt go anywhere.

i do agree though. keeping the box in place will be the challenge here.

I was originally thinking about using 1" square steel tubing welded to a steel plate with bolts going to the top of the box and the bottom of the truck bed. Do you think that would suffice? And I don't have a forklift handy so this thing has to be built in the truck. Which I am not looking forward to lol.

Sounds good as long as there are more than 1-2 of them lol

i didnt read all the post, but 48hz sounds like a fair tuning frequency. however things seem pretty contradicting to me.

its in a truck (i presume extended cab with rear seats) so the cabin gain is going to be high and peaky; probly 50ish maybe even 55hz. which is good for SPL comps

but you said you want it to drop low.. this is where i see the biggest problem, with the combination of the high cabin gain and high Fb (plus 4th O BP tends to be pretty peaky aroung the tuning frequency) idk how low it will actually go. not to mention, your subsonic should be set 5-7 hz below your enclosure Fb. OTOH im willing to bet you pull some crazy numbers around 50hz

If he is as far back as a C pillar and has the cone area of 6 18s, playing low isnt an issue. Being that far back gives the wave time to mature thus allowing him to play lower louder.