Noob question (capacitor and sub box)

**greatkiller** · 11-08-2006, 11:34 PM

Hi

I figured I needed some help or tips on the following. Im not too good in audio and just started experimenting in my ranger. So far *knock on wood* there hasnt been a firework in my truck. Anywho first question is about a capacitor I just bought. Its a 1.2 farad tsunami. I bought it used so I didnt get resistor. Now if I wanted to charge it what kind of resistor do I buy and can someone show me a pic and the specs? I look on radioshack.com and I saw a bunch and didnt know which would be for my capacitor.

Now for the sub box. I was going to run an audiobahn click here to see it. Now I want to build a box for my truck that is ported and here is my little 2 min work.

questions:

1. How many Cu. feet would this be if I built it on 3/4 MDF?

2. How big should the port be and is the port supposed to be some pipe going into box?

3. Where would the port be better off top or bottom?

4. How big would the port be at this size box?

5. Will the box be good for the audiobahn lol?

Much MUCH appreciate it for those that help

Here is a pic. The dimensions are 27 X 16 X 12 (W X H X D). By the way the port would be on the LEFT side of the box not near the sub

**GoHybrid** · 11-09-2006, 12:18 AM

Well first of all, let's address the cap. What you'll want for a resistor is a 50-ohm 5 watt resistor. They look like this: http://www.maplin.co.uk/images/full/2179i0.jpg

All capacitors will self discharge. The idea is to slowly charge the capacitor and connect it before it discharges to the point that you risk creating big sparks. Long story short: make sure you have the final connection to the cap and the tools ready to secure it as soon as the cap displays that it has reached battery voltage.

As far as the box goes, you need to do a little more research into the driver you want to use. There are many equations free and available on

that will ask for certain Thiele-Small parameters (T/S) which you may be able to obtain on audiobahn's web site. You can then take these parameters and plug them into an equation along with the frequency you want to tune the enclosure to and then you will get the port size and length you're asking about.

If math and numbers aren't your thing, then you can download a free program called WinISD which will give you considerable help in designing an appropriate enclosure.

again, google is your friend, and i must stress, excercise caution and planning with your capacitor. fried fingers are no fun.

**greatkiller** · 11-09-2006, 12:27 AM

Thanks for reply.....now as far as capacitor. If i begin to charge it and I see the LED tell me 14V do I remove resistor and right then and there with battery connected screw in the positive? Also should the amp also be connected?

By the way I got this chart on audiobahn website but I have No clue what is means:

http://www.audiobahn.com/Audiobahn06..._sub_specs.pdf

the one I want is the AW121T which is in the middle

**GoHybrid** · 11-09-2006, 02:13 AM

Well... in retrospect i figure a safer way to connect the cap yet would be to leave the resistor connected, and then connect the positive wire from the battery to it BEFORE removing the resistor. That way it never really has a chance to discharge. Also, yes, the amp should be connected already.

As far as the box goes, download WinISD and follow the instructions to add your own driver to the database. Most of the things it asks for when creating a new driver are on that spec page you found. Just transfer them over. Then follow the directions for creating an enclosure.

What you will get is the answer to your question regarding size, shape, and length of the port, as well as internal volume dimensions. You will also see an ideal-world plot of your enclosures frequency response illustrating peaks and dips based on the resonance of your enclosure and your driver parameters. You can edit the variables to get the response curve you're after.

The best part is, when you're done, the program comes with a tone generator that you can pipe through your amp and test your design at specific frequencies so you can fine tune it to your liking in the end.

Don't be afraid to experiment with this a little. The better you understand it, the more addictive the whole process becomes.

Good luck!

**LaxPlaya8513** · 11-09-2006, 10:43 AM

if you have one of the newer Tsunami caps, they have a built in resistor. It's the little lightbulb in the corner of the cap.... or so i believe? possibly. Just go with the safeside and do the resistor

i just thought i had seen it there previously

**Megalomaniac** · 11-09-2006, 04:35 PM

you dont need a cap :fyi:

what tuning are you looking for on the box? I see you drew a circle for a port, ar eplanning on aero ports or percision ports? It be cheaper to do a slot port out of mdf.

to find ur cubic ft, use the equation L x W x H / 1728 or Volume/1728, (make sure you plug in the internal dimensions not the outer dimensions, otherwise it will be off by .75 in each direction) dont forget to subtract the displacement of the sub to get ur true cubic ft of the box.

-Mir

**GoHybrid** · 11-09-2006, 05:54 PM

i'm going to go ahead and qualify megalorese15"'s statement by saying that you don't NEED a cap, but it IS beneficial to have one IF your alternator can keep up with your amp. IF your alternator can handle the overhead for charging the cap AND supplying your amp, then you will be rewarded with a higher, cleaner voltage at your amp which means your amp isn't working as hard nor drawing as much current to make music.

IF your alternator can NOT supply ample current for your amp, then a capacitor will do you NO good.

Nothing against anybody personally but it just ****es me straight off to hell when people just roundly reject an idea with absolutely zero support or qualification for their own ideas.

**Megalomaniac** · 11-09-2006, 05:57 PM

Originally Posted by GoHybrid

i'm going to go ahead and qualify megalorese15"'s statement by saying that you don't NEED a cap, but it IS beneficial to have one IF your alternator can keep up with your amp. IF your alternator can handle the overhead for charging the cap AND supplying your amp, then you will be rewarded with a higher, cleaner voltage at your amp which means your amp isn't working as hard nor drawing as much current to make music.

IF your alternator can NOT supply ample current for your amp, then a capacitor will do you NO good.

Nothing against anybody personally but it just ****es me straight off to hell when people just roundly reject an idea with absolutely zero support or qualification for their own ideas.

x2
its like people think a CAP makes its own power