2 different sub sizes in vehicles?

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mullberry

Member - Posts: 5

Joined: May 22, 2003

Location: United States

Posted: May 24, 2003 at 2:31 PM / IP Logged

i am building a box that houses 2 8" and 1 12" (in bandpass) and the speakers are all the same brand. well the problem is that the guys in my shop think that you can get bass cancellation due to different speaker sizes and even if that were so wouldn't reversing the phase correct the problem. I have been installing for about 10 yrs and it doesn't make sense to me because even factory vehicles have different speaker sizes in them and they (sometimes) sound decent. And also in home theater's they use different speaker sizes in front, rear, center, and LFE so i guess i just dont see how this is possible. I have been going through this forum and you guys seem to know what the hell is going on so i figured i would ask. any ideas? thanks

auex

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Joined: December 23, 2002

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Posted: May 24, 2003 at 3:29 PM / IP Logged

The problem lies that they are all going to be going into the same box. It is fine to mix subs only when they have seperate boxes, crossover points, and in most cases amps, otherwise they will cause cancellation of sound waves. If the box you are building is not chambered then it will sound horrible.

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mullberry

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Joined: May 22, 2003

Location: United States

Posted: May 25, 2003 at 6:05 PM / IP Logged

actually they are 3 different boxes 2 sealed @ .5 cubic feet for the eights and the other for the 12 is a 4th order bandpass ported on the high side at 70 hz 1 cubic foot on the low side and .5 cubic feeet on the high side. i can see why they might because of the response time might be different for the 8's and 12 because the 12 might be slower to react but still the difference would be completly negligable. would any of this still cause bass cancellation?

bdl666

Silver - Posts: 330

Joined: December 31, 2002

Location: United States

Posted: May 26, 2003 at 2:17 PM / IP Logged

Building boxes is as much science as it is luck(when it comes to radical designs). So just go for it you never know how it's going to sound. I have a made a lot of boxes that were not supposed to sound good at all, and they sound sweet.

So go ahead and build the box . But don't use plexiglass or cover the box . Just make it out of mdf and see how it sounds. If you are happy with the results then go ahead and finish it .

mullberry

Member - Posts: 5

Joined: May 22, 2003

Location: United States

Posted: May 27, 2003 at 10:33 AM / IP Logged

yeah i will and by the way have you seen alpine's demo vehicle? 15's 12's & 10's so i don't think it will be a problem...i think my guys are just being jerks.

D148l0

Copper - Posts: 57

Joined: May 13, 2003

Location: United States

Posted: May 27, 2003 at 11:40 AM / IP Logged

Mulberry, more important than the size of the subs is the kind of box used... if you have enclosures of different kind (in your case sealed+bandpass) almost sure you are gonna get wave cancellation, even if they are separate enclosures... (in some instances that is the way extreme noise is reduced in enviroments like factories ). Setting your crossover points to totally different frecs may reduce the problem, and maybe the cancellation couldn't even be noticed... please anybody, correct me if I'm wrong...

d148l0

mullberry

Member - Posts: 5

Joined: May 22, 2003

Location: United States

Posted: May 27, 2003 at 3:20 PM / IP Logged

well that makes sense but the 4th order is still a sealed bandpass. it would make complete sense if i used sealed along with a ported along with a 5th order and maybe even an aperiodic or infinite baffle that it would cancel out the standing waves with all of that going on...but i guess i am still just confused...i live in wyoming so we don't get a lot of call for this sort of system...kinda like no-mans land out here. but if anyone can still help out it would be greatly appreciated...in the meantime i am just going to put it together and try it out. But it would still be great to find out more information in this matter. thanks

D148l0

Copper - Posts: 57

Joined: May 13, 2003

Location: United States

Posted: May 27, 2003 at 3:40 PM / IP Logged

A bandpass is not a sealed enclosure since it is ported... (quote) Mulberry: " the other for the 12 is a 4th order bandpass ported on the high side at 70 hz 1 cubic foot on the low side and .5 cubic feeet on the high side". The fact that the sub is inside a chamber does not mean it is a sealed enclosure, so you have 2 different kinds of enclosures in your installation...

Check the woofer enclosures link in this page, it's very useful.

d148l0

mullberry

Member - Posts: 5

Joined: May 22, 2003

Location: United States

Posted: May 27, 2003 at 4:51 PM / IP Logged

i do understand that, that is why i am asking questions. I alyways am trying to learn more. all i am trying to figure out is if it will cause bass cancellation and how bad will it be? or will the box implode?

D148l0

Copper - Posts: 57

Joined: May 13, 2003

Location: United States

Posted: May 27, 2003 at 5:22 PM / IP Logged

we all are eager to learn more... I'm sorry if I didn't sound as polite as I would like to, but english is not my first language so I try to make myself as clear as possible... 2 different sub sizes in vehicles? -- posted image. . Almost sure you will have bass cancellation that meaning that you will not hear all the frecuencies you could... how bad? very difficult to tell in advance, but the more similar the frecs given to the subs in different enclosures, the more cancellation obtained... that's what auex and I meant when we referred to crossover points... and even so, it's hard to tell... Of course, it can be calculated, but I'm not a tech... don't worry, there are guys with lots of knowledge in this site that will give you better advice...

d148l0

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2 different sub sizes in vehicles?

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