# Downside to REVERSE mounting subwoofer?



## Lumadar (Sep 28, 2007)

Hi guys. I am going to be building a fiberglass enclosure with a common chamber for 2 DIYMA 12 inch subs for my ZX3 HATCHBACK Focus and I had some questions about possibly reverse mounting the subs. Will loading the subs in the enclosure backwards remove some of the gain to be had from aiming woofers at the rear hatch in hopes of picking up a few db's? Anything else to be aware of? 

I just thought it might look nice and also allow for a smaller overall enclosure by mounting them this way.

thanks for the help in advance


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## npdang (Jul 29, 2005)

Bad diffraction in the upper frequencies, but nothing to worry about under several hundred hz.


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## t3sn4f2 (Jan 3, 2007)

npdang said:


> Bad diffraction in the upper frequencies, but nothing to worry about under several hundred hz.


Npdang, any benefit heat dissipation wise in mounting them that way, or not enough to warrant the extra space it would take up.


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## Lumadar (Sep 28, 2007)

npdang said:


> Bad diffraction in the upper frequencies, but nothing to worry about under several hundred hz.


So would I expect the same gains typically associated with rear firing subs in a hatchback with the subs mounted in an inverse manner?


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## KAPendley (Nov 19, 2007)

Less Cone Area = Less Bass


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## Thumper26 (Sep 23, 2005)

CCSS said:


> Less Cone Area = Less Bass


how do you figure?


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## KAPendley (Nov 19, 2007)

Some cases its not an audible difference, but its a fact. 
The magnet, basket, etc take away from surface are of the sub. Less surface area, less cone, less bass. No different than an engine........"No replacement for displacement." 

You will VERY rarely see an SPL competitor with inverted subs.

This may not be applicable to Lumadars situation, but its really the only disadvantage. In a hatchback, it will be loud anyway. 

I would try it both ways, and see what HE likes the most. But if he wants to show off the sub, theres nothing wrong with doing that way.......but he will lose db's.


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## Thumper26 (Sep 23, 2005)

interesting. i've never heard that.

i can see where the spider, magnet, etc would either absorb some of the sound or interfere with the waves developing correctly. it makes sense when you think about it.


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## t3sn4f2 (Jan 3, 2007)

Lumadar said:


> So would I expect the same gains typically associated with rear firing subs in a hatchback with the subs mounted in an inverse manner?


Like Npdang said, yes unless you play above the several hundred Hz range.


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## MadMaxSE-L (Oct 19, 2006)

CCSS said:


> Some cases its not an audible difference, but its a fact.
> The magnet, basket, etc take away from surface are of the sub. Less surface area, less cone, less bass. No different than an engine........"No replacement for displacement."
> 
> You will VERY rarely see an SPL competitor with inverted subs.
> ...


Only issue I can see with "trying it both ways" is the change in internal box volume with the backside of the sub outside the box - when you invert the sub, the box effectively becomes larger, and vice versa.

it may be only marginal difference, but it will be there I would think...


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## t3sn4f2 (Jan 3, 2007)

Thumper26 said:


> interesting. i've never heard that.
> 
> i can see where the spider, magnet, etc would either absorb some of the sound or interfere with the waves developing correctly. it makes sense when you think about it.


It doesn't inhibit things in that way when it comes to sub bass. It's happen by less cone displacement since the inner coil circumference is not expose to the air the way it is on the opposite side. It fires into the pole piece. So you loose the small amount of radiating surface.


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## MadMaxSE-L (Oct 19, 2006)

Aren't you supposed to flip the phase of the sub if you invert?

Maybe not, I just hought I read that somewhere; figured it might help the OP...


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## Thumper26 (Sep 23, 2005)

yeah, if you invert, to keep it in original phase, you have to flip it.

then again, having the sub out of phase might just make things sound better for you...


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## khail19 (Oct 27, 2006)

MadMaxSE-L said:


> Aren't you supposed to flip the phase of the sub if you invert?


Yes.


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## Boostedrex (Apr 4, 2007)

CCSS said:


> Some cases its not an audible difference, but its a fact.
> The magnet, basket, etc take away from surface are of the sub. Less surface area, less cone, less bass. No different than an engine........"No replacement for displacement."
> 
> You will VERY rarely see an SPL competitor with inverted subs.
> ...



Sorry to be anal, but one part of your statement is simply incorrect. "There's no replacement for displacement" is the incorrect part I'm talking about. That's only an old ******* saying. There is actually 1 replacement for displacement and 1 only. It's called a rotary engine. 

But aside from the engine analogy, you are correct about the rest. 

Zach


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## MadMaxSE-L (Oct 19, 2006)

Boostedrex said:


> Sorry to be anal, but one part of your statement is simply incorrect. "There's no replacement for displacement" is the incorrect part I'm talking about. That's only an old ******* saying. There is actually 1 replacement for displacement and 1 only. It's called a rotary engine. Zach


You are absolutely incorrect. There is no replacement for displacement - there are bandaids(boost/Nitrous), but no replacement. 

And  on the rotary. They sound like outboard boat motors...


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## Boostedrex (Apr 4, 2007)

MadMaxSE-L said:


> You are absolutely incorrect. There is no replacement for displacement - there are bandaids(boost/Nitrous), but no replacement.
> 
> And  on the rotary. They sound like outboard boat motors...


You are incorrect too. The rotary is the only replacement. Honda 4 bangers don't do it so don't think I'm talking about that. But when I can take 2.6L of N/A motor and turn out 600hp to the ground on 93 octane, I'd love to see a piston motor with that displacement that's NA and not on the bottle make those numbers reliably. It works for Mazda, hence the Le Mans win with the 787B.(Granted that wasn't on 93 octane fuel.)

And they don't sound like boat motors!! They sound like a chainsaw on crack. LOL!!!!!!!!!


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## KAPendley (Nov 19, 2007)

MadMaxSE-L said:


> Only issue I can see with "trying it both ways" is the change in internal box volume with the backside of the sub outside the box - when you invert the sub, the box effectively becomes larger, and vice versa.
> 
> it may be only marginal difference, but it will be there I would think...


Very true, but again, that depends on the T/S parameters of the sub. The vd (volume displacement of the sub) is usually measured in cubic inches. So it really wouldn't be enough to make a significant change in the airspace one way or the other. There are enough tolerances in enclosure design that as long as the airspace is marginal, the sub will not suffer.


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## KAPendley (Nov 19, 2007)

Boostedrex said:


> Sorry to be anal, but one part of your statement is simply incorrect. "There's no replacement for displacement" is the incorrect part I'm talking about. That's only an old ******* saying. There is actually 1 replacement for displacement and 1 only. It's called a rotary engine.
> 
> But aside from the engine analogy, you are correct about the rest.
> 
> Zach


LMAO..........true..........but its a good analogy with subs. I do know how dangerous a rotary engine is, and how underrated they are. Not a pro on the subject, but when you can get 300+ hp out of a 1.3 liter engine with little modifications, its pretty damn impressive.


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## Boostedrex (Apr 4, 2007)

I was always curious about just how much of a difference the inverted shape of the cone would add to the volume of the box. I didn't think that it would be enough to really change how the sub would sound. 

Now how much do you need to worry about how "noisy" the motor of a sub is when mounting it in a hatch like a ZX3? 

Nguyen, could you comment on if the DIYMA has a relatively "noisy" motor or not? My DIYMA 12 is mounted normally and I LOVE the sound of it.

Zach


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## MadMaxSE-L (Oct 19, 2006)

Boostedrex said:


> You are incorrect too. The rotary is the only replacement. Honda 4 bangers don't do it so don't think I'm talking about that. But when I can take 2.6L of N/A motor and turn out 600hp to the ground on 93 octane, I'd love to see a piston motor with that displacement that's NA and not on the bottle make those numbers reliably. It works for Mazda, hence the Le Mans win with the 787B.(Granted that wasn't on 93 octane fuel.)
> 
> And they don't sound like boat motors!! They sound like a chainsaw on crack. LOL!!!!!!!!!


Um, am I wrong or isn't the rotary boosted? And it definately is at 600hp( while it makes ~200 lb. ft of torque) 



CCSS said:


> Very true, but again, that depends on the T/S parameters of the sub. The vd (volume displacement of the sub) is usually measured in cubic inches. So it really wouldn't be enough to make a significant change in the airspace one way or the other. There are enough tolerances in enclosure design that as long as the airspace is marginal, the sub will not suffer.


Even a ported enclosure? I know they are a little less forgiving with regards to size...


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## Boostedrex (Apr 4, 2007)

MadMaxSE-L said:


> Um, am I wrong or isn't the rotary boosted? And it definately is at 600hp( while it makes ~200 lb. ft of torque)
> 
> 
> 
> Even a ported enclosure? I know they are a little less forgiving with regards to size...


Not all rotaries are boosted. And the 600hp with ~590 pound feet of torque was N/A!! The rotary only has torque issues in the 1.3L configuration. The 2.0 and 2.6L engines are usually close to, if not exactly, equal on hp and tq. 

Sorry for the thread jack Lumador, but Rotorheads are typically extremists and argue their point any time they get a chance.


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## KAPendley (Nov 19, 2007)

Thumper26 said:


> yeah, if you invert, to keep it in original phase, you have to flip it.
> 
> then again, having the sub out of phase might just make things sound better for you...


If it is one sub, it cannot be wired out of phase, only reverse polarity. Common misconception.

Out of phase is when you have 2 speakers, or subs, with one wired with the correct polarity, and the other reverse polarity. Then it DOES suffer, tremendously. You can immediately tell if this is how someone has it wired up. There is little too no bass, and it sounds "muffled". 

If the sub is inverted, it will have to be reverse polarity, so the piston is pushing in the same direction as it would have been mounted normally.

BTW, not knocking on you bro...........just trying to help. 
I had to learn all of these same things...ya know? And I'm still learning everyday. Thats the adventure of 12 volt.


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## t3sn4f2 (Jan 3, 2007)

A thing of beauty....... 

View attachment 3391


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## KAPendley (Nov 19, 2007)

MadMaxSE-L said:


> Um, am I wrong or isn't the rotary boosted? And it definately is at 600hp( while it makes ~200 lb. ft of torque)
> 
> 
> 
> Even a ported enclosure? I know they are a little less forgiving with regards to size...


Still have plenty of room for some "fudging of the numbers" lol. As long as the airspace is marginal. If you mess with the port, then yes, it can change, but only for the tuning frequency, which is going to be different anyway, depending on the vehicle it goes in. 

Now Im not talking about being way off in the design....but like I said, the subwoofer isnt going to be enough to make the enclosure design off.......normally. A sub will only take up about .5 cubic inches. I dont think you would have to worry about that changing airspace much.


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## monkeyboy (Jun 12, 2007)

t3sn4f2 said:


> A thing of beauty.......
> 
> View attachment 3391


As long as you aren't the one who has to clean it.  

My polishing days are coming to a close.


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## npdang (Jul 29, 2005)

Oh forgot to mention... you're correct as well about the cooling benefits. I think it would be something "maybe" noticeable to your ear depending on how well your driver sheds heat.


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## MadMaxSE-L (Oct 19, 2006)

CCSS said:


> If it is one sub, it cannot be wired out of phase, only reverse polarity. Common misconception.
> 
> Out of phase is when you have 2 speakers, or subs, with one wired with the correct polarity, and the other reverse polarity. Then it DOES suffer, tremendously. You can immediately tell if this is how someone has it wired up. There is little too no bass, and it sounds "muffled".
> 
> ...


Thank you for the correction; my mistake. But you answered my question, thanks.

oh, and sorry about the hi-jack as well - I am a big block guy at heart and always have liked to argue.

Speaking of, Boostedrex, if you don't mind, I am gonna pm you with some questions I have regarding the rotary. not to argue, I am seriously curious.


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## Kahooli (Oct 17, 2007)

CCSS said:


> A sub will only take up about .5 cubic inches. I dont think you would have to worry about that changing airspace much.


my sub is much greater than .5 cubic inch.... you running a 1" woofer?


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## KAPendley (Nov 19, 2007)

Kahooli said:


> my sub is much greater than .5 cubic inch.... you running a 1" woofer?


OOPS.........Im retarded. 

Here is a better example, with a larger sub.

Arc FL12D2 Displacement .12 Cubic Foot. In cubic inches, that would be 
around 207


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## KAPendley (Nov 19, 2007)

WTH was I thinking? Sorry, its been a long day.


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