# Need a Sub Enc IDEAS for a 21FT Formula David vs Goliath!!



## illtww (Feb 24, 2009)

I want my boat to BANG! I don't really care about SQ just SPL'S.
Trying to figure out what to do with what I have or if I need to scrap it and go with something else. (NOTE: The sub(s) will be in 100 deg heat for 5hrs+)

Here is what I am working with:
21FT Formula Cuddy Cabin. (can work with the whole cabbin but also store stuff in there like the 3 BIG Marine batteries that power the system, noodles, coolers etc...)

Equipment List:
All 4 gauge wires
2 MM2124 12" Polk MOMO's
1 x JBL GTO7001 AMP
JBL GTO7001 - Monoblock Car Amplifier, Power Amp - Sonic Electronix

Pioneer Premier deck that can set the crossover freq for the
subs mids highs etc...

Mids and High's: (Have amps for these and sound fine currently)
8 Polk MM651um (4 on tower 4 in boat)
MM651UM Car Audio Speaker from Polk Audio
2 8" Bazooka Tubes with Rockford Fosgate p1's in em.


Space I am working with:
I don't know the EXACT dimensions because the boat is not near me but it is a pretty large space. (I am including pictures) I would ideally like to place the sub-box on one side of the cabin or lay it on the side of the boat to maximize space for some other things but I am open to suggestions!

My buddy that is in the pic is 6ft tall so I am guessing the cabin is around 72 inches from the tip of the boat to the cabin door.

Side note:
People come out on the lake here in NC with FU*CK1N DJ speakers attached to the speaker bars. (full on 15's and 12's and generators etc!) While I am on a very limited budget since I have no job right now I still kinda want to show them what my lil 22ft boat can pound out!) (David vs Goliath mentality)

This is EXACTLY what my boat looked like when i got it. (took us 3 months of working on it!!!)
1980 FORMULA THUNDERBIRD 21FT : eBay Motors (item 250608782492 end time Apr-03-10 04:38:02 PDT)


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## illtww (Feb 24, 2009)

Was possibly thinking a Kicker Solo-Baric L7 12" in a large box....
Matches well with my amp correct?


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## Wheres The Butta (Jun 6, 2009)

illtww said:


> Was possibly thinking a Kicker Solo-Baric L7 12" in a large box....
> Matches well with my amp correct?


what happened to the momo 12"'s ?

If anything, for that low power I would try and get some subs with very high efficiency, and build a horn.


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## illtww (Feb 24, 2009)

Still got the 12's....

But thought 1 big box with an l7 in it would fit nicely with the amp I have and pound!


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## Wheres The Butta (Jun 6, 2009)

illtww said:


> Still got the 12's....
> 
> But thought 1 big box with an l7 in it would fit nicely with the amp I have and pound!


A single L7 isn't a bad choice, but I have my doubts about it standing up to a marine environment... Personally, I would browse marine speakers.


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## illtww (Feb 24, 2009)

Polk Momo are already "marine" speakers.

The subs will be under the cabin away from water and out of the sun...


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## illtww (Feb 24, 2009)

another option is a T-TQWT box....

I like this guys setup..
Need a very loud sub box design for wakeboard boat - Page 7 - diyAudio


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## Lanson (Jan 9, 2007)

If you want to get loud on a budget, then the answer is cone area. The more you have, the more efficient and loud you'll be able to get on a given amount of amplifier power. So, let's work with that. Can you build a manifold of, say, 12 12's?


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## illtww (Feb 24, 2009)

foruthmetal..

how is 12 12's on a budget?


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## Lanson (Jan 9, 2007)

Well I recently picked up closeout Lanzar's for $15 each, so it can be done! I mean, JBL GT5's run less than $130 for a pair, so I don't think that's unreasonable do you?


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## Lanson (Jan 9, 2007)

Or while I'm thinking about it, consider a bunch of these in a manifold:
AE Speakers Online Store
That's one of the best sounding, lowest inductance, least expensive quality IB subs there is I think.

Hell those things could play upper midbass, no problem at all. Maybe even midrange, but of course that might cause interference patterns!


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## illtww (Feb 24, 2009)

i can't really afford that right now...

want to utilize my polk momo 12's...

Or buy a loud @ss sub and box combo..


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## Lanson (Jan 9, 2007)

That's fine, just won't do what you want.

A set of 4 of those Lanzars in a 12cu ft box w/ a 6" round hole in it (on 3/4" Birch wood for a box) WILL do it though.


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## Wheres The Butta (Jun 6, 2009)

fourthmeal, remember this is a marine environment. the temperatures are going to wildly fluctuate, and there's going to be moisture. 

I agree though, cone area = efficiency.... I still think a horn is a good idea though, maximize the output.


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## illtww (Feb 24, 2009)

bd5034...

I am guessing my polk audio 2124 wont work well for the horn design? Would like something fairly simple to construct. (a tapered horn looks easy!)


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## Lanson (Jan 9, 2007)

bd5034 said:


> fourthmeal, remember this is a marine environment. the temperatures are going to wildly fluctuate, and there's going to be moisture.
> 
> I agree though, cone area = efficiency.... I still think a horn is a good idea though, maximize the output.



I know, marine evironment etc... but if they aren't getting direct water contact then you should be OK. Besides, even if they last only a year or two before rotting, he's still running dirt-cheap and getting the SPL he wants.


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## my6x9s (Apr 15, 2009)

i agree with bd5034
a nice big horn will do the job
my lil nissan did 135.5 with one 12 and 125wrms 
double checked by the judges and got a honorable mention trophy 
a rough calc would be about 20' of folding horn
it would do 30hz range perhaps shorter if you want higher hz
so yes if you put in the time you can do it bigger and better 
with less. you may be able to use the cabin as part of the horn design for a lil extra gain


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## illtww (Feb 24, 2009)

120+db is fine with me....

so 20' (feet) of folded horn correct? looks like the stock boxes get you around 105 db...

120+ would be jammin!


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## my6x9s (Apr 15, 2009)

i think 20' +or - horn would be ideal for a 12" but bare in mind this was a rough calc. lot of other things to consider but i did my calc with a start of 3/4wide"and 15" tall gap/port in the start and it ended with a rough mouth of 15" by 15" to keep the tapper but you can do what ever you wish this was just a quick sketch and you can always model a few before you cut wood
try this program to play around Telstra BigBlog - i find it helpful for the angle and taper and length but im not a mathematics guru


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