audio help

[Attack Eagle]

i
i've seen this guy with 3 mojo memphis audio subs in his car and didnt shatter .... although his roof did shake. (so much power)

That is because the car is NOT sealed, there are flaps to release pressure in the aft rear quarter. This makes it possible to close the door with the windows up with out slamming it, as well as push air into the interior from the HVAC system

 

[napkinthief]

how can i measure how much space the sub takes up in the box?

is it just an eyeball type of thing or is there a method?

also, wtf is medium density fiberboard, i went to a local home depot and i asked 3 reps there and none of em knew what i was talking about, but i think they knew less than me about wood sooo......a picture of it or something please?

 

[napkinthief]

http://www.cardomain.com/item/SONXMD6000GTX


i just picked that up off ebay for 144$ shipped

300w rms at 4 ohms is just perfect for my sub

and then 600w rms at 2 ohms, so if i get another ill have each sub geting 300w rms

thanks a lot guys, ill get pictures up as soon as i get everything installed.

 

[drivemusicnow]

Medium Density Fiberboard. Otherwise known as MDF... whichever hardware store you went to is filled with idiots.

Anywho, for subwoofer air displacement, the specs SHOULD be listed on a website that contains specs for the subs. However for a subwoofer like this, its really immaterial as far as how much the sub displaces.. its less than .1 cubic foot, and typically manufactures list easier to build numbers rather then "the best exact displacement" for the speaker. Honestly look to build a box with in about .1 cubic feet of 1 cubic foot that works in the trunk of your car and it will sound fine.

 

[Attack Eagle]

how can i measure how much space the sub takes up in the box?

is it just an eyeball type of thing or is there a method?

also, wtf is medium density fiberboard, i went to a local home depot and i asked 3 reps there and none of em knew what i was talking about, but i think they knew less than me about wood sooo......a picture of it or something please?

It will be in the subs specs.

MDF is what it is known by, youve seen the crap wood they use for houses, fiberboard/particle board? IT is a much finer and stronger wood than that, and ultra smooth. It has no grain. Home' de Pot shoudl have it, and I know lowes carries it. It's problem is humidity and it tends to crumble a bit around edges (like the ones that hold the screws and the corners ofthe box) as it ages. Thus it gets a bit leaky after a while or if exposed to weather.

Now it is good but a bit heavy and not as strong/durable as for example appleply.
Apple ply cost about 2x as much but it weighs a good bit less and it is Known to be much stronger than MDF. I'm probably going to use MDF since most of my enclosure will be glass this time instead of a wood one. and it is easier to router and shape mdf than a hard wood

19mm MDF is 49 pounds per cubic foot
19mm BB ply is 32 pounds per cubic foot (baltic birch is the imported equivalent of Appleply (which uses no apple))

WIth either you want to include internal bracing and a NON square design for strength and to prevent standing waves at the cabinets natural resonance. THe interna bracing will make it stiffer and stronger and alo prevent buzzing or flexing, leading to improved acoustics and durability. AN easy way yto do this is to cut 3,4,or 5 "end pieces and router out the inside of the ones that will fit INSIDE the box into triangular shapes. Pre drill and assemble the face of the cabinet with all the "endcaps" in place with construction adhesive and screws, then add each exterior side. Where you can fit additional stringers between the formers/"endpieces" do so.

Let dry for a day and cover etc, it will be heavy, but will serve you for many many years.

example this would be one of the pieces for the inside, wiht out the triangles it would be the one of the outside two.

You must be logged in to view this image or video.

Supposedly there is an HDF but you can never find it and its WAY heavy stuff.

 

[napkinthief]

will any bracing inside the box affect the way the sound moves around the box, or does it just take up space that needs to be accounted for in the external dimensions to get the 1 cu foot that the manufactoror recommends.

also, its recommened i have a sealed box, but i read around that you get much ebtter quality from a ported box. which should i do?

also, is 13.5 x 13.5 x 13.5 external good? or is it bad cuz its a perfect cube? that would leave 12x12x12 inside, which is exactly 1 cu. ft.

 

[Attack Eagle]

with the extremely long waves no it won't affect sound inside the box.

yes it does take up some room but not enough to matter


I wouldn't build a perfect square enclosure, but better to build one that you can build WELL than a leaky trapezoid.

If you can build one non cubed and build it well please do so, for example a circular saw can be angled to give you the beveled cuts you would need for the front piece.

 

[napkinthief]

ok i just made the box with a slanted front, it measures 8 deep on top, 12 deep on bottom, 14 3/4 high and 17 wide with .75 mdf, inner dimensions are 8.5x13 1/4x15 1/2


total in = 1745.6875
cu foot = 1728

difference = 17.6875 this amount should be enough for the speaker i hope.... if not ill put in a small block of wood to take up the extra space to get the exact 1 cu foot thats recommended


now i got another question, about polyfill where do i get it, do i need it, do styrofoam packing peanuts work the same way it does by making the sub think it has a bigger box by slowing the waves?

also do I have to carpet the inside and outside? or can i just paint the outside

 

[Attack Eagle]

since unlike 90% of people you made you box the right size, you don't need polyfill. You don't need to carpet the inside either. JUt run a bead of adhesive around the seams (not silicone) and call it done. YOU can paint or carpet or vinyl the outside as you wish

 

[gsx951]

The necessity of polyfill has been questioned by some but in a nut shell what it does is alter the compliance of the airmass trapped in the box. Most drivers will play lower in a box that is stuffed. Just about every Hi-Fi speaker made uses some type of stuffing.
The hard core speaker building Geeks favor Acousta-Stuf :
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=260-317
You can find dacron polyfill at fabric stores for around $2.00 a yard.

 

[Chuckster]

A small amount of fill is used to absorb the standing waves inside the box. In a subwoofer, in a car, I really doubt you'll notice a difference if it's in there or not.

Please DON'T use packing peanuts! I can just picture them clinging where they shouldn't any causing mechanical damage to the sub.

 

[napkinthief]

i used liquid nails, but i didn;t have a gun to load the cartridge into to bead it out evenly, so i just cut it open with my dremel (haha i love my dremel) and scooped out glops and ran my finger along the edge to make a perfect seal. after about 2 hours, i did it again just to make sure i had everything covered, and for the records i used less than 1/2 a tube for the whole box. i also glued and scrwed all the edges, predrilled all of em, but there was still a few wood splits. I filled the splits with liquid nails to make em solid. ill try to take some pics tommorrow


i have more questions

i just got the amp today its BRAND NEW so im happy with that, but where should i mount it? on the box was my first though, but i read somewhere that violent shaking can make everything go loose

 

[Attack Eagle]

depending on its size, under the floor, or atop it. I really DON'T like stuff screwed to the seatbacks.

 

[napkinthief]

manufacturer says its best to keep the amp right side up for cooling purposes, im thinking of making a small rack out of the MDF i have left, then putting some rubber grommets between the amp and MDF to minimize the vibrations, this should look good...


i keep seeing threads about rubber grommets under the passenger carpet, but there is no rubber grommets under my passenger carpet, maybe because im nt, i dunno, can someone post a pic of where i can pass a wire through???

 

[napkinthief]

ok the rubber piece is really big, about the size 2x3 and simply pushing on it, you should see sunlight pass through the engine bay, just punch it and run the wire through. VERY SIMPLE

and for running the wire to the back, just slide it under the plastic and only a small 2" piece will show where a screw blocks you, but i think it looks cool in my car

 

[napkinthief]

Ok I got my box finally upholstered professionally and got some pics

guy originally wanted 75$ for labor, but I promised to show off his work and tell people I got it done at his shop.


p.s. that ring is just a chalk outline of the sub hole. I am not sure how it fits inside the box, so I just left it uncut until I get the sub and see how it goes.

had to remove the number/name cuz its advertising and thats not allowed...

 

[napkinthief]

i got my 4 gauge kit today finally and i wiried up the amp, the little green light on the amp blinks a few times then goes out, am I doing something wrong or is it because I dont have a sub hooked up?

 

[Chuckster]

What does the operating manual say??

 

[napkinthief]

the manual says use 4 gauge wire and route the blue wire to a non constant source

my first non constant source was my acc from my ignition harness because i had it already stripped from when i did my locks. that put the amp on all the time my car was on so that was no good

i then decided to put it on my +12 to my headunit, because my headunit is never on unless the key is in the ON position. that left me with a few blinks then no solid power.

i looked up the pioneer deh1500 on google and found my headunit harness is missing a few wires so i went down to circuit city and picked up a new harness, and it did have a remote turn on lead, which was blue, hooked it up and now it works fine.

edit: as of right now im starting to make another box for another 12" sub, to get the whole 600 rms thing going...i also put together some spare MDF pieces and made a short of shelf for the amp, but the amp will be mounted inside....only a picture can descibe it so after im done ill get some pics for you guys....all i can say is i have about a 1 1/2' x 2' trunk space left after the 2 sub boxes and the amp mount, but it looks DAMN nice

 

[Attack Eagle]

I like your "loaded" enclosure... excellent idea.

 

[Chuckster]

the little green light on the amp blinks a few times then goes out, am I doing something wrong or is it because I dont have a sub hooked up?

the manual says use 4 gauge wire and route the blue wire to a non constant source

I was asking what the manual said about the blinking light. Glad you fingered it out!

 

[napkinthief]

I was asking what the manual said about the blinking light. Glad you fingered it out!

the manual didn't have anything about a blinking light for three blinsk if that, seemed like it got power for a sec, then diede, but i fixed it, i sure fingered it out.