# Down firing - Sealed - any experience?



## dcarwin (Feb 2, 2008)

I was picking the brain of my friend Skip, co-owner of StreetNoyz in SD, and he was suggesting for my first diy sub in my wagon that I try a sealed down-firing enclosure. Does anyone have experience here? I can't seem to find much info via google on car audio down firing applications. It does seem to be the method of choice for home use though. (Take my HSU for example). I am trying to understand what kind of gap (if any) need to be created around the rim. If I understood Skip correctly, he suggested no gap at all, so that the area in front of the speaker is actually somewhat sealed as it sits on the carpet, creating backpressure.

Thanks,
Dan


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## MadMaxSE-L (Oct 19, 2006)

dcarwin said:


> I was picking the brain of my friend Skip, co-owner of StreetNoyz in SD, and he was suggesting for my first diy sub in my wagon that I try a sealed down-firing enclosure. Does anyone have experience here? I can't seem to find much info via google on car audio down firing applications. It does seem to be the method of choice for home use though. (Take my HSU for example). I am trying to understand what kind of gap (if any) need to be created around the rim. If I understood Skip correctly, he suggested no gap at all, so that the area in front of the speaker is actually somewhat sealed as it sits on the carpet, creating backpressure.
> 
> Thanks,
> Dan


While I have no first hand experience with this type of setup, I know for a fact that you need a few inches of clearance away from the speaker cone - you don't want it hitting anything throughout its range of travel...

Also, if the front side of the cone is "kind of sealed", then to me that sounds like a variation of bandpass enclosure - not sealed.

-Matt


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## Aaron'z 2.5RS/WRX (Oct 24, 2007)

Seems a little silly to me to have the subs surround sitting on the floor, from your description... 

Down firing is much the same as corner loading, both can work really well, but, I can't really help you with particulars, like distance between the sub and whatever you load it into... 

I DO know, I used to test out some boxes I used to help build (pre-fab sub boxes) and we had a single 10" ported "truck" style box, I had it in my VW, side fireing into the MDF amprack/walls I had built into the rear and that sub AMAZED me EVERY day.... and it was a "no name" Emenence built 10" generic... it blew my pair of 12's out of the water on all points... so loading has plenty of merrit for you, but, again, i can't give you particulars like others here should...


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## CMR22 (Feb 10, 2007)

dcarwin said:


> If I understood Skip correctly, he suggested no gap at all, so that the area in front of the speaker is actually somewhat sealed as it sits on the carpet, creating backpressure.
> 
> Thanks,
> Dan


I've not heard that before. Quite a few people who own trucks, including myself, downfire their subs in the center consoles. Mine sits about 3" off the carpet.


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## Oliver (Jun 25, 2007)

This might help you , it's a sag calculator [to determine suitability] 
http://www.subwoofer-builder.com/sonosub.htm


excerpt]
A downfiring woofer can be subject to a sagging cone caused by the mass of the cone. Make sure that the manufacturer specifies that mounting the woofer downfiring is okay, (the SV12 and AC12E are both suitable for downfiring). Downfiring offers two potential benefits:

The elimination of a grill often simplifies the building process and can enhance the speakers appearance. 
A downfiring sub will reduce the audibility of harmonic distortion and may help the sub to acoustically "disappear" better. 
If you design a down-firing sub make sure you have enough distance from the floor to the woofer to allow unrestricted air flow.


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## Oliver (Jun 25, 2007)

Formula:

excerpt]
Post #6 
Hi,
Adire's calculations for "sag" seem too simple.

Quoting from the pdf that Weikertball posted.

Mms =1 / [(2*Pi*Fs)^2*Cms]
sag=Cms*Mms*g = g / [2*Pi*Fs]^2

so sag depends of Fs squared, as I said it sounds too simple.

Can anyone confirm the calculation method from another source?

Going a little further,

Xmax > 4970 / Fs^2 
for sag to be less than 5% of Xmax.


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## dcarwin (Feb 2, 2008)

Thanks all,

And Matt - yes the speaker can't hit the floor. That's the "rim" I refer to, which extends beyond the edge of the box for this purpose. Like a cube with one side pushed in to create a lip, and the lip tall enough to prevent the driver from hitting the surface it rests on. I think the idea proposed is to -not- vent this lip. If I do some prototypes with sonotube I may be able to compare different rim designs. (vented/sealed).


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## Hillbilly SQ (Jan 26, 2007)

i think downfiring is an excellent idea to keep on the table no matter what you drive. i know i fooled many people with my old memphis hpo10 sealed and downfired off 250rms. it's all about finding what works best in each individual install. you can make a 10" sound like a pair of 12's and vice versa. if the latter you did something wrong


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## MadMaxSE-L (Oct 19, 2006)

dcarwin said:


> Thanks all,
> 
> And Matt - yes the speaker can't hit the floor. That's the "rim" I refer to, which extends beyond the edge of the box for this purpose. Like a cube with one side pushed in to create a lip, and the lip tall enough to prevent the driver from hitting the surface it rests on. I think the idea proposed is to -not- vent this lip. If I do some prototypes with sonotube I may be able to compare different rim designs. (vented/sealed).


ok, I gotcha . I don't know how having a sealed chamber on each side of the driver cone would work out though; sounds like it would take quite a bit more power to drive a sub in an enviornment like that. But like I said, I've never tried it - sounds interesting...

-Matt


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## bobditts (Jul 19, 2006)

you have to make sure that hte sub is capable of being down fired. Google the "woofer sag calculator"

Down firing is great. Ive always loved the way they sound. HOWEVER, in wagons, Ive always personally prefered side firing woofers flush behind the rear wheel wells.


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## Oliver (Jun 25, 2007)

The 8W3's worked well in a downfiring enclosure,[ under the front seats of a Ford-F350 ].


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## grampi (Jun 29, 2007)

dcarwin said:


> I was picking the brain of my friend Skip, co-owner of StreetNoyz in SD, and he was suggesting for my first diy sub in my wagon that I try a sealed down-firing enclosure. Does anyone have experience here? I can't seem to find much info via google on car audio down firing applications. It does seem to be the method of choice for home use though. (Take my HSU for example). I am trying to understand what kind of gap (if any) need to be created around the rim. If I understood Skip correctly, he suggested no gap at all, so that the area in front of the speaker is actually somewhat sealed as it sits on the carpet, creating backpressure.
> 
> Thanks,
> Dan


A friend of mine once built a down firing sealed enclosure with four 15's running off of an old Lowphonics amp and the thing just hammered! They were just cheap a$$ MTX Road Thunder subs too.


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## bobditts (Jul 19, 2006)

grampi said:


> A friend of mine once built a down firing sealed enclosure with four 15's running off of an old Lowphonics amp and the thing just hammered! They were just cheap a$$ MTX Road Thunder subs too.


the MTX RT series subs are great for budget subs.


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## Abaddon (Aug 28, 2007)

No woofer is capable of being in a Down (or up) firing alignment forever. Eventually the moving mass WILL cause the cone to sag. With certain woofers, you might be able to get away with it for quite some time... but eventually the driver dynamics will change since the voice coil will no longer be centered.


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## tophatjimmy (Dec 16, 2005)

I built a variant of one of the Decware Inverted Wedge Box for my bro-in-law's Toyota Ex-Cab. 2 12" ED something or other's powered by a Blau VA2200. 

All I can say is WOW. very very nice.....

I'm a believer in downfiring.


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## Aaron'z 2.5RS/WRX (Oct 24, 2007)

Abaddon said:


> No woofer is capable of being in a Down (or up) firing alignment forever. Eventually the moving mass WILL cause the cone to sag. With certain woofers, you might be able to get away with it for quite some time... but eventually the driver dynamics will change since the voice coil will no longer be centered.


Wouldn't that also hold true for ANY orentation though?? I know of hundreds of up firing set-up, how would that be any different than down? or back...? 

the suspension/spider is holding the whole moving mech in "suspension" so over time would a rear firing sub end up ripping through the VC because the suspension/spider sagged? 

not likely when you think about it.. 

Just my counterpoint


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## speakerboy (Oct 2, 2007)

I would think loading the front of the cone like that would change the frequency response of the speaker, pushing it higher into "boomy" category. Not saying that's what happens in practice, but in theory, it makes sense.


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## KnightWhoSaysNI (Jul 23, 2007)

speakerboy said:


> I would think loading the front of the cone like that would change the frequency response of the speaker, pushing it higher into "boomy" category. Not saying that's what happens in practice, but in theory, it makes sense.




Maybe with a high cone mass and high QTS... I dont thing that a paper driver would though


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## speakerboy (Oct 2, 2007)

speakerboy said:


> I would think loading the front of the cone like that would change the frequency response of the speaker, pushing it higher into "boomy" category. Not saying that's what happens in practice, but in theory, it makes sense.





KnightWhoSaysNI said:


> Maybe with a high cone mass and high QTS... I dont thing that a paper driver would though



I don't know if it would only apply to certain models. A downfiring configuration is not the same as corner loading. Corner loading helps steer the large wavelengths into the room without letting them go out, hit the wall and come back to destructively interfere with themselves.

When you put a sub into a box, it does not play as low as the same in a IB configuration. It is because the box is acting as air suspension. This keeps you from over excursion, and allows more power handling. I would think that by adding a mass of air to the front of the cone (downfiring), as well as the back, would in affect make the suspension stiffer, because the cone now has to push through air that has very little space to move that way it wants to. Instead of moving in the same direction as the driver, it has to turn 90 degrees and move out.

Like I said, just thinking out loud.


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## Oliver (Jun 25, 2007)

speakerboy,

you're doing well on thinking out loud, when you front load a sub it causes it to move more linearly [ less distorted ].


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## Oliver (Jun 25, 2007)

These subs will be front loaded and rear loaded [ so they will move backwards and forwards in a line or lineary ].

The air will load up on the front of the cones.


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## MadMaxSE-L (Oct 19, 2006)

a$$hole said:


> These subs will be front loaded and rear loaded [ so they will move backwards and forwards in a line or lineary ].
> 
> The air will load up on the front of the cones.


Wow, that's pretty cool . How did that setup sound?


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## Aaron'z 2.5RS/WRX (Oct 24, 2007)

a$$hole said:


> These subs will be front loaded and rear loaded [ so they will move backwards and forwards in a line or lineary ].
> 
> The air will load up on the front of the cones.


Dam man, is that "your" design/pics? that some interesting **** right there..!!


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## Abaddon (Aug 28, 2007)

Aaron'z 2.5RS/WRX said:


> Wouldn't that also hold true for ANY orentation though?? I know of hundreds of up firing set-up, how would that be any different than down? or back...?
> 
> the suspension/spider is holding the whole moving mech in "suspension" so over time would a rear firing sub end up ripping through the VC because the suspension/spider sagged?
> 
> ...


The difference would be, that the traditionally mounted speaker (who's suspension would loosen up over time) would be mounted in a way that the moving mass would not cause "sag" in the suspension causing it to move from it's zero position with relation to the magnetic field when the speaker was not being driven.

Now... How MUCH sag are we talking about? I have no idea, I've never measured one over time... How much does a suspension loosen over time... Well I'm sure Chad has some large woofers from over 40 years ago that still work fine.. so it might not matter all that much.

My basic point.. just so that everyone gives it some thought, is that a vertically mounted speaker has the additional load of gravity to fight, while a traditionally mounted loud speaker does not. Does this end up hurting the transducers operation? Maybe.. Maybe not... (it would have to do with how large the moving mass was in relation to the suspension compliance)... are there other benefits to running a vertically mounted speaker? Probably... I'm just throwing this out there so we always think about the big picture.


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## Oliver (Jun 25, 2007)

MadMaxSE-L ,Aaron'z 2.5RS/WRX , those are pictures from Decwares site.
I'm currently building one in other audio.

Horizon or horizontally mounting a sub works for some drivers, a front facing or vertically mounted sub is the norm.


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## metanium (Feb 2, 2007)

I am running a JL 10W3V3 in a sealed, down-firing box. It sounds great! I have also ran an IDQ-10V2, Dayton RS 10"HO, JL 12W6V2, JL 10W6, and TC Sound OEM 10 in this arrangement.

In every one of these arrangements, the down-firing was the key to improvement. I don't know the physics behind it, but I do know that there is a distinct increase in SPL with the enclosure down-firing vs. forward, rear, or up-firing in my truck. I guess this is the "loading" that's been referred to. It also works when firing my home sub into a corner as opposed to into the room.

Another benefit that I've noticed is less "mechanical noise". By that, I mean you hear less of the noises, buzzes, etc. that are made from the cone moving. Instead, you hear more clean bass notes.


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## dcarwin (Feb 2, 2008)

Metanium, what kind of air gap are you allowing between the floor and the box?


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## Oliver (Jun 25, 2007)

dcarwin said:


> Metanium, what kind of air gap are you allowing between the floor and the box?


It is about 1"-3" more than the xmax of the sub [ 12-13 mm equals 1/2" ].


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## Soundsaround (Apr 22, 2006)

Abaddon said:


> My basic point.. just so that everyone gives it some thought, is that a vertically mounted speaker has the additional load of gravity to fight, while a traditionally mounted loud speaker does not.


Can't escape gravity...
and the suspension is always suspending  ...
so...
Wouldn't the weight on the suspension just be distributed differently depending on orientation? Vertically firing, the load would be distributed evenly around the suspension. Horizontally, wouldn't the load be pulling back on the top of the driver and pushing out on the bottom? We're talking minute amounts here too correct?
*+*
Wow, what a cool box a$$hole!


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## rockondon (Jan 18, 2008)

I once ran two ID 10s...I liked the sound much better. And not sure but they seamed to play lower also.
I was told a min. of 2in from sub. I built the box 12x14x36 and ended up with a 2.5in slot. [3 sides plus floor side were MDF ,leaving a slot]


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## HondAudio (Oct 19, 2006)

grampi said:


> A friend of mine once built a down firing sealed enclosure with four 15's running off of an old Lowphonics amp and the thing just hammered! They were just cheap a$$ MTX Road Thunder subs too.


Lowphonics? More like LOLphonics!


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## 6262ms3 (Feb 27, 2008)

I've done 2 down-firing enclosures, one worked really well and one totally sucked. The good one was in my old ext cab pickup and had a JL 12W6 sealed with only 150 watts going to it. 3 of the 4 sides underneath were open and the sub had room to breath. It was really clean and tight and the low power didn't matter much as the sub was right behind me and didn't need a ton of output. The crappy one was in a boat with an RF 10HX2 sealed with 300 watts or so going to it. The problem with it was that the back and both sides were tight against the interior and it could only push air out through the front. You could actually watch the whole box lift upwards (and it was NOT a light enclosure!) with the bass hits, the air was pressurizing under the box and not radiating into the boat very well. So in my amateur experience down-firing can work great as long as the area under the box isn't too constricted.


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## Oliver (Jun 25, 2007)

Aaron has an Audio Avalanche under his rear seat in a extended cab pick-up.

12" sub, the seat had to be raised


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## Infinity (Jun 28, 2005)

Downfiring has the barrier loading advantage, and it also lower the F3 of teh enclosure (but I forget how much- it may depend upon application). I like to close off three sides around the woofer so that I can also "duct" the pressure where I want it. This works VERY nice behind the seat of a truck when you shoot the soundwaves under the seats.


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## Oliver (Jun 25, 2007)

Infinity said:


> Downfiring has the barrier loading advantage, and it also lower the F3 of teh enclosure (but I forget how much- it may depend upon application). I like to close off three sides around the woofer so that I can also "duct" the pressure where I want it. This works VERY nice behind the seat of a truck when you shoot the soundwaves under the seats.


egg sakkalee  

Then once Aaron reversed polarity to the sub [ I was smilin, then ].


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## bluecavi28 (Feb 19, 2008)

Infinity said:


> Downfiring has the barrier loading advantage, and it also lower the F3 of teh enclosure (but I forget how much- it may depend upon application). I like to close off three sides around the woofer so that I can also "duct" the pressure where I want it. This works VERY nice behind the seat of a truck when you shoot the soundwaves under the seats.


Very interesting. So when I put my JL 8.3 microsub behind my seat in the truck will I want to slightly aim it under the seat and block off the rest of the openings? Or simply aim it straight down?

This is what an 8.3 Microsub is for those who have not seen one: http://www.mmxpress.com/images/83MICSBL.jpg

you can aim the woofers in any direction you want. The box contains three JL 8w6 subs.


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## speakerboy (Oct 2, 2007)

Infinity said:


> Downfiring has the barrier loading advantage, and it also lower the F3 of teh enclosure (but I forget how much- it may depend upon application). I like to close off three sides around the woofer so that I can also "duct" the pressure where I want it. This works VERY nice behind the seat of a truck when you shoot the soundwaves under the seats.


Again, my brain is telling me that the F3 of the enclosure will be *raised*, not lowered. I would think this because you have now added a mass in front of the cone, making the driver work harder to dig as deep as before.


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## Hillbilly SQ (Jan 26, 2007)

keep in mind folks that most of the success stories are from people with trucks. and in my experience reversing the polarity has been a requirement with downfiring. without reversing i've always had insane cancellation issues. the little bit of delay reversing causes really seems to help.


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## zero7404 (Jan 31, 2008)

what about the +'s/-'s of upward firing sealed enclosures. one that is installed below the trunk floor ?


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## Hillbilly SQ (Jan 26, 2007)

zero7404 said:


> what about the +'s/-'s of upward firing sealed enclosures. one that is installed below the trunk floor ?


try it both ways and see what sounds best


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## zero7404 (Jan 31, 2008)

Hillbilly SQ said:


> try it both ways and see what sounds best


i don't want to do downward firing. need to do upward to free up room in the trunk.


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## Oliver (Jun 25, 2007)

bluecavi28 said:


> Very interesting. So when I put my JL 8.3 microsub behind my seat in the truck will I want to slightly aim it under the seat and block off the rest of the openings? Or simply aim it straight down?
> 
> This is what an 8.3 Microsub is for those who have not seen one: http://www.mmxpress.com/images/83MICSBL.jpg
> 
> you can aim the woofers in any direction you want. The box contains three JL 8w6 subs.


Point it the way your ears tell you too


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## Hillbilly SQ (Jan 26, 2007)

zero7404 said:


> i don't want to do downward firing. need to do upward to free up room in the trunk.


i meant try the polarity both ways.


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## Infinity (Jun 28, 2005)

bluecavi28 said:


> Very interesting. So when I put my JL 8.3 microsub behind my seat in the truck will I want to slightly aim it under the seat and block off the rest of the openings? Or simply aim it straight down?
> 
> This is what an 8.3 Microsub is for those who have not seen one: http://www.mmxpress.com/images/83MICSBL.jpg
> 
> you can aim the woofers in any direction you want. The box contains three JL 8w6 subs.


I used one exactly as you speak behind the seats of a '97 F150, then again in a '96 Blazer. Of course the setup was louder in the truck, but worked very well in the SUV



speakerboy said:


> Again, my brain is telling me that the F3 of the enclosure will be *raised*, not lowered. I would think this because you have now added a mass in front of the cone, making the driver work harder to dig as deep as before.


The F3 is lowered due to boundary loading. It is precisely the same as using a loading panel, but less work.
I would downfire woofers in my SportTrac, but the biggest I'd be able to fit would be MAYBE some 6.5's.......unless...(runs out to find a tape measure)


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