# [DIY Project] car sub for home use



## benniebeeker (Mar 26, 2012)

all,

i'm getting started in my first DIY subwoofer... i'm trying to build a very compact sub for use with my computer... currently i own these monitor speakers but i need a little punch to go behind them... i was looking at pre-fab subs but i can't find what im looking for... so i decided to build my own... 

i'm looking for something in 6.5-8" woofer range... anything bigger than that and i'm going to have a tough time finding a place to put it... plus i don't want to drown out my left/right... my little home office is only 8x13' with 7 foot ceilings... seems like anything bigger than an 8 would be overkill for my needs.... initially i was looking at this woofer with this amp... then i noticed the box requirements for the driver was .416cu (roughly 10.5x10x10)!!! seems like a lot for a 6.5 sub... so i figured i would give car subs a shot... i found a jl audio that i can pack into an 8.5x8.5x6.5 box (only requires 1.5cy)!!! i could even go with an 8" in a 10x10x9.5" box....

can anyone give me any input on going the car sub rorute for home use??? perhaps guide me to a smaller home sub that will give me good sound in a small package???? seems like i can get big sound in a tight box with the right sub/amp/box combo...

also a few more n00b issues i'm facing...

do i need to put acoustic foam inside of the speaker box or is that not necessary for subs???

i noticed that requirements for sealed boxes are a lot smaller than ported boxes from manufacturers spec pages... would you guys recommend ported over sealed??? my interests are 50% music 30% news radio and 20% movies... 

if you guys suggest ported, would it be beneficial for me to add passive radiators to the box instead of using port holes??? could i possibly use radiators on sealed box dimensions??? 

any recommendations or insight would be greatly appreciated...


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## benniebeeker (Mar 26, 2012)

also, if i run 2 8ohm subs in parallel in the same box, does that mean that they will run 4ohms???


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## ChirstineTan (Mar 26, 2012)

Any ideas how to diy?


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## benniebeeker (Mar 26, 2012)

i can build a box, i just need help with design... i'm shocked that no one has any input on this...

also, i found this database created by mike p... it is very inspirational, but unfortunately i couldn't find anything that is the same "small scale" that i'm looking for...


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## looneybomber (Sep 20, 2006)

Small size, low freq output, efficient. Pick two.

Basically, if you want a small enclosure you either limit output down low, or you need a bigger amp to get the low freq output. Another way to put it, if you have an amp already picked out, but want more low end output, the box will have to grow. This is true for both ported and sealed.

Ported requires a larger box but in return, you get more output at and within 1 octave of the tuning frequency.

Passive radiators act just like ports and can be used in place of ports. This is beneficial when your enclosure is too small for a properly sized port. The trade off is they're way more expensive than a port.


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## tshifrin (Nov 24, 2011)

Have you noticed the "mini-me" build thread under Ported Sub Projects?


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## benniebeeker (Mar 26, 2012)

looneybomber said:


> Small size, low freq output, efficient. Pick two.
> 
> Basically, if you want a small enclosure you either limit output down low, or you need a bigger amp to get the low freq output. Another way to put it, if you have an amp already picked out, but want more low end output, the box will have to grow. This is true for both ported and sealed.
> 
> ...


excellent info... thank you for the reply... sounds like my best option is to go small box with a PR... i think im going to go with the JL 8w3v3-4 road with 2 PR's... im going to build a box that is slight larger than sealed factory spec to allow the radiators to fit. I plan on going with a 200 watt plate amp built into the rear of the box... 

after reading the reviews, the sub itself is extremely efficient in tight spaces... after all, that is what it was degined for... it only requires .3 cubuc feet for a sealed box... 

i read that filling the box with poly fill makes the woofer think that the enclosre is larger... is this accurate information???



tshifrin said:


> Have you noticed the "mini-me" build thread under Ported Sub Projects?


no i did not, but thank you for pointing that out!!!

::EDIT::

I checked out the thread... he did a killer job, but im looking to go more compact than that...


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## looneybomber (Sep 20, 2006)

A passive radiator is a Helmholtz resonator, just like a port is a Helmholtz resonator. They're used interchangeably. Because of that, when using a passive radiator, you have to follow the same rules and guidelines as you would a ported box. There's no cheating physics.

Now, if small size I'd the ultimate constraint, maybe look at isobarically loaded enclosures. You lose 3db of efficiency, but you cut the required box size in half. 

Side note, if you cut the power in half, you lose 3db. See the relation.


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## benniebeeker (Mar 26, 2012)

a buddy of mine at work pointed a few pre-fabs out to me that will meet my needs... these are all 8x8x8 in size and have pretty beefy amps... the low end cuts out around 40hz but as i mentioned home theater won't be my main interest.... im using this for mostly music on a 2.0 set of stereo speakers... i think i'm just going to bite the bullet on the energy m6-800... it is only 219 from a seller on amazon and would be cheaper than my build plans... 

http://www.amazon.com/Mirage-MM-6-m...e-Subwoofer/dp/B001HRFINY/ref=cm_cr_pr_sims_t

http://www.amazon.com/Energy-ESW-M6-800-Watt-Mini-Subwoofer/dp/B004TA8YM8/ref=dp_ob_title_ce

http://www.amazon.com/Jamo-800W-Active-Subwoofer-Black/dp/B00460TJZC


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## looneybomber (Sep 20, 2006)

Well if going the retail route, take a look at Craigslist or eBay for used sunfire subs. If you don't find any, no biggie, but it's worth a check. I always like to find the good deals. That said, of the three subs linked, pick the cheapest one. They're essentially all the same, so why pay more if you don't have to?


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## benniebeeker (Mar 26, 2012)

looneybomber said:


> That said, of the three subs linked, pick the cheapest one. They're essentially all the same, so why pay more if you don't have to?


i 100% agree... thanks again for your input...


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