# Cons, if any, of downward facing sub???



## vwjmkv (Apr 23, 2011)

are there any? I'm thinking of building a box with subs firing downward. 

was going to put them where spare goes, but had a blow out over the week end that made me rethink the layout of the trunk.


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## BlackHHR (May 12, 2013)

Does not matter if it is mounted with the basket out. A lot of installers do it when depth is limited.
Mine is mounted inverted and are very happy with the outcome.


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## Tripn88 (Jun 28, 2015)

I have two 12s down firing in my truck and they sound good. Only down side is making sure you don't rub during excursion. Also it might sound different in your car vs my truck.


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## Weigel21 (Sep 8, 2014)

You are speaking of a downward firing sub setup and not merely an inverted mounted sub, correct? 

Along with the possible issue of a lack of clearance for full excursion, I have come to find that a downward firing enclosure seems to make a car rattle more so than subs loading off the rear of the trunk. 

So a more dire need to sound deaden could be a possible negative. LOL

Then there's the whole argument over cone sag.


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## ImK'ed (Aug 12, 2013)

Ive heard of spider sag dont know how true that is though.


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## LaserSVT (Feb 1, 2009)

Running downfire. I love it.


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## Weigel21 (Sep 8, 2014)

ImK'ed said:


> Ive heard of spider sag dont know how true that is though.


I "think" it was more of an issue with old school subs, back when cones were much heavier.


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## BlackHHR (May 12, 2013)

We have two examples of this type of install currently at the shop. Both applications work very well. The 3 - 15" are in IB configuration and the below picture is a single 12" in a sealed cabinet . 

The 5 series BMW, my wife's little HHR and the last is a project by Justin Marks. It also has the baskets out.


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## vwjmkv (Apr 23, 2011)

thanks guys, i am considering building the box to where the sub is face down, not just an inverted config. the basket will still be in the enclosure. I've seen a few home subs built this way and i wondered why i couldn't do that in my car. if i do build said box, i will give the bottom about an in or 2 of clearance to that i won't be having them rub on the floor upon full excursion. and i also have the JL screens so I'm confident they in how much room to give.

I've also read about the possible "cone sag" but i couldn't find any info on sag regarding the JLs i have. after having the subs from a couple years now and taking them out of the box they were in previously i noticed how they are a lot softer from when they were new. any other input will be greatly appreciated


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## Weigel21 (Sep 8, 2014)

Well most any sub when brand new will have a stiffer spider, some manufacturers even coat their spider with more resin to lower the FS of the driver, which naturally the spider would become more flexible AKA softer after a period of use as the resin gains more micro breaks.


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## vwjmkv (Apr 23, 2011)

thats pretty much what i figured. i expected the suspension to be softer. i was just surprised at how much softer it was. 



Weigel21 said:


> Well most any sub when brand new will have a stiffer spider, some manufacturers even coat their spider with more resin to lower the FS of the driver, which naturally the spider would become more flexible AKA softer after a period of use as the resin gains more micro breaks.


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## SkizeR (Apr 19, 2011)

Weigel21 said:


> Well most any sub when brand new will have a stiffer spider, some manufacturers even coat their spider with more resin to lower the FS of the driver, which naturally the spider would become more flexible AKA softer after a period of use as the resin gains more micro breaks.


im almost positive stiffer suspension = higher fs


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## Weigel21 (Sep 8, 2014)

Sorry, you may well be correct on that SkizeR, I just recall that some add resin to the spider to change the FS, and to me, lowering it makes more sense than raising it, but...


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## squeak9798 (Apr 20, 2005)

Weigel21 said:


> I "think" it was more of an issue with old school subs, back when cones were much heavier.


Moving mass is generally higher now than the old school subs. Longer coils, more "heavy duty" cone materials, thicker and larger surrounds and spiders, etc. 

Do a search for Adire's Suspension Sag white paper on Google. Believe Stereo Integrity is hosting most of them now. Has a very simple formula for calculating the risk of cone sag based on the moving mass and suspension stiffness.


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## sirbOOm (Jan 24, 2013)

I just went into my present-state build in my garage which has a dual 10" Hybrid Clarus setup getting 600 watts total in a SUV downfire box (temporary setup until I build boxes, testing if I like downfire sound). I do notice a difference with downfire being a teeny bit more muffled (and the downfire box makes a sort of slot port/vent thing when downfiring) but I'm getting lower Hz bass more easily. Rear firing I get more chest punch/feel and just seems "more right" to me. This is a hatchback vehicle - specifically a Chevy Volt with an Arc 1200.6.

BTW, I noticed I liked upfiring in my past pickup trucks better than downfire... again, muffled sounding. Maybe, though, I was hearing distortion w/the upfire that I liked hahaha... ug.

We do downfire all the time in vehicles where the owner doesn't want to destroy their sub and convertables/Wranglers. Also seems to prevent some trunk door vibration in some cars apparently.


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## amalmer71 (Feb 29, 2012)

I did it in my wife's old 2006 Pontiac SV6 (Montana) for the simple fact that she still wanted to be able to stack stuff on top of it. 

I put a 10" Alpine Type E in a 1 cu/ft sealed enclosure and had an old Alpine 3527V running the two front coaxials I replaced and the other two channels bridged to the sub, giving it a very underrated 70 watts RMS. That van pounded and sounded fantastic.

I also noticed it muffled the sound of the sub a little, removing some of that "kick" of the kick drum, but it still sounded great. It was very smooth and worked extremely well when playing movies for the kids. That was not too long after the first Transformer movie came out and the kids loved it! Added a lot of realism to the movie and a smile on their faces.


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## SHAGGS (Apr 24, 2011)

Addressing cone sag, via the Parts Express website;

You can calculate the sag of a driver from:

Percentage of Sag = 24,849 / ( Xmax * Fs²)

where

- 24,849 is a constant value based on the relationship of acceleration due to gravity and Pi.
- Xmax is the maximum linear excursion of a loudspeaker voice coil while remaining within the magnetic flux field (mm).
- Fs is the free-air resonant frequency of the woofer (Hz).

The following is the same formula, including the relationship of acceleration and Pi in this case:

Percentage of Sag = 981,000 / (Xmax * (2 * Pi * Fs)²)

where

- 981,000 is acceleration due to gravity (mm/S²) * 100 (for the percentage).
- Xmax is the maximum linear excursion of a loudspeaker voice coil while remaining within the magnetic flux field (mm). - Fs is the free-air resonant frequency of the woofer (Hz)
- Pi is the ratio of a circle's circumference and diameter, usually rounded to 3.14.

As a general rule of thumb, any time the sag exceeds 5% of the driver's Xmax, it's not recommended for a down-firing subwoofer application.


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## vwjmkv (Apr 23, 2011)

this is some good info, i kind of had the idea/ concern that sound might be affected some by down firing the subs. since the floor will be so close to the subs' cone. i had thought about porting the enclosure, and having said port face upward or toward to the front to help, not sure how or if that would help. i wonder what PWK would think about these setups in mind




sirbOOm said:


> I just went into my present-state build in my garage which has a dual 10" Hybrid Clarus setup getting 600 watts total in a SUV downfire box (temporary setup until I build boxes, testing if I like downfire sound). I do notice a difference with downfire being a teeny bit more muffled (and the downfire box makes a sort of slot port/vent thing when downfiring) but I'm getting lower Hz bass more easily. Rear firing I get more chest punch/feel and just seems "more right" to me. This is a hatchback vehicle - specifically a Chevy Volt with an Arc 1200.6.
> 
> BTW, I noticed I liked upfiring in my past pickup trucks better than downfire... again, muffled sounding. Maybe, though, I was hearing distortion w/the upfire that I liked hahaha... ug.
> 
> We do downfire all the time in vehicles where the owner doesn't want to destroy their sub and convertables/Wranglers. Also seems to prevent some trunk door vibration in some cars apparently.


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## Weigel21 (Sep 8, 2014)

So how many have done down fire enclosures in which the openings totaled at least that of the Sd of the woofer being used?

I ask as I figured that a downward firing enclosure that didn't have enough area of the opening would result in the sub more/less unloading into itself. I mean if the sub has 130 square inches of surface to push with, but the openings for this air to be pushed out of is only 80 square inches, could it be that this is the reason the setup seems to produce more of a muffled output with less gusto. 

My last setup was a Polk MM1540 in a 1.5cuft sealed down fire enclosure that had 3.25" legs down the entire depth of the enclosure leaving the only openings to be the ends facing the front and rear of the car. These openings were both 3.25" x 21", which comes to 136.5 sq. in., while the sub's Sd is 128.5sq in. 

Just some food for thought and I welcome any input on the mater.


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