[drivlikustoleit]

I've done a lot of searching on the internet and can't find any concrete answers for my question.

Are there certain shapes, sizes, dimensions, etc. that you absolutley need to know to build yourself a box. I want to put two subs in my trunk, one on each side where it indents. Reason being is I 1) don't want to lose trunk space an 2) want to be able to keep my spare tire and also be able to easily access it. I don't have anyhing against doing it the way I have seen some people do it on here... it actually looks fvckin' sweet, I'm just trying to be a little more "conventional" I guess you could say with my approach to a better sound system.

Or can I just slap together a box that fits perfectly in that space and it will sound good no matter what ( When I say slap together, I don't mean some ghetto p.o.s either, I know if there's gaps and stuff, it will lose a lot of power)

Thanks in advance for everyone's advice.

[jamis33]

Ok the best advice i can give you is to look through the instruction manual that came with your subwoofer. Somewhere in there it will say something along the lines of "reccomended enclosure size" Mine for example was 1.25 cu. ft. (per woofer) Then you measure the dimensions of where you wanted to put it and play with the dimensions so they eventually make the reccomended enclosure size. As long as the volume of the box (lxwxh) is around the reccomended enclosure size it will sound fine. I dont think shape matters too much. I started out 1 cube with 1 12" woofer and moved up to a dual rectangle enclosure and they both sounded great. I hope this is clear this helps you.

[drivlikustoleit]

Well I guess my first problem was that I don't have a sub yet. I wanted to get this figured out before I invested in one.

Thanks for the help, it cleared up a lot for me. Now all I have to do is find subs that put out good sound in the amount of space I am trying to fill up. Oh, and I have to try and figure out what kind of amp, how to hook it up and all that good stuff. That's what I use the people at Best Buy for though, I get all the professional knowledge from them, find out what is the best set up for me, then go in ebay and buy everything for half the price AHAHAHAH!

Thanks again...

Anybody concur or disagree with this info.?

[jamis33]

well thats a good plan. My set up isnt the greatest but it certainly adds a lot of thump to the back of my car. I got that Insignia (BestBuy brand i think) party pack that comes wiht 2 12" and a 300 watt amp. I got it on ebay for $80 cdn shipped. I thought that was a pretty good deal. It all depends on what you wanna do with ur woofers. I really like the rockford fosgate punch 10s. Those sound amazing and fairly common on ebay. I dunno wut other guys on this forum are gonna say about amps but i have found through experience that a more expensive amp isnt always better. My buddy had an mtx amp and it blew after one year and he paid over $300 for it. It was the 500 watt one. I've had my 300 watt amp since july and i run it pretty hard and i havent had a problem yet. The best thing to look for when buying an amp is the power of it. In my opinion its the subs that sound good and the amp doesn't affect sound quality too much.

[drivlikustoleit]

Yeah I hear ya. I just wanna get 2 tens... one for each side. Something just to bring up the quality of the bass. The speakers I got are good for treble, but the bass sounds like shit, so I wanna drown out that shitty bass with some decent thump. I listen to metal music so the bass is more of a back up, rather than rap where it is everything. They're gonna be there to make it sound more full.

I just gotta figure out what the advantage of having multiple channel amps is and what bridging is... I'm very ignorant with this stuff lol. I figured two subs, two channel amp??

[jamis33]

ya u're right. 2 subs, 2 channel amp. The number of channels is just how many things you can hook up. Bridgeable means you can turn 2 channels into one. On mine i can put out 150 watts on 2 channels, or i can put out 360 watts on one channel bridged. I can try and clear that up if u dont get it but thats wut it means.

[drivlikustoleit]

Yeah that makes sense. So when you're hooking everything up, you wire the amp to the subs and the head unit. Do you have to get power from the battery or can you get that from the head unit? I always see people with the thich gauge wires for power. Where do you get your ground from? And how do you know which wire to splice into on the head unit?

[jamis33]

ok well i'm going to assume you're using an aftermarket head unit. If not things are a bit trickier. Depending on what wattage amp you buy will determine which guage wire you want to use for ur amp. Don't hold me to these numbers but the general rule is:
0-250watts------> 10guage
250-550watts----> 8guage
550-800watts----> 4guage
800+-------------> 0guage

Thats what i followed. If you're runnin 2 10" subs it should be safe to use 8 guage unless you're runnin them at a huge amount of power. The best way to install your amp is to head over to the DIY articles section and theres one called "2k1 coupe amp wiring" or something like that. Follow that diy. You'll probably want to buy an amp wiring kit from a any store that sells car audio stuff. Make sure you get the right guage wire for your car. The basic idea is to run your power wire from the battery (make sure u put a fuse on it), thru the firewall, along the passenger side of the car all the way to the trunk where the amp is going to be. Then you can splice either the illum or the remote or even the power from your head unit and again run the remote wire along the passenger's side of the car. I live in canada and tapped the daytime running light fuse so that to get the subwoofer to work the car has to be on 2 clicks insteaed of just one for the radio. For the ground find a nice spot in your trunk sand it off and screw your ground wire to it. Then get the connect the rca's to your head unit and run them on the DRIVER'S side this will prevent any interference from the power. If your head unit has a sub out thats great. If it doesnt i say use the rear channel. Then connect the rca's to the amp. Then connect all the power things. then run regular stereo cable from ur amp to the woofers.

[drivlikustoleit]

Whoa thanks for all the info. Some things are a little fuzzy to me, but I'm not going to ask them on here 'cuz it'll take too much typing and too much time. You've given me a good amount of info to where I can sound like I know what I'm talking about when I go to best buy or wherever. I have to figure out what my speakers can handle, if I have rca outputs, etc. etc. I'm in the beginning phase of heading up this project as you can see.

+1 for you

[speedfoos]

All good points here. But let me add a couple things.

Don't go to Best Buy for either your install or your purchase. Yeah they're easy because you can say,"I want that, that, and that, and I want you guys to install it all on Thursday" plunk down your plastic and walk away with a smile. However, in my experience, much better prices can be found online - hell, most of the stereo stuff I use has been gotten off of Ebay. By all means go to Best Buy to look at the stuff, comparison shop, check prices, listen to the decks and speakers and talk to the techs, but I wouldn't look to them as a one stop shop. Anyway here's some specifics.

Amplifier wiring kit
Head on over to your local Wal-Mart and pick up their 0 gauge (may be call 1500-2000 watt) amp wiring kit. Last time I bought one it was like $35. You can't touch these for under $80 at Best Buy. This isn't overkill in case you ever want to add another amp, and plus the kit has everything you need.

Box building
Check this site out.
CarStereo.com

This is the help section where it has all kinds of formulas to determine the best sounding box size.

It has a little calculator (Sealed Speaker Enclosure Design Calculator) for figuring the optimal size of a box for any specific sub if you have a couple values from the sub manufacturer. Use the Calculator and enter in the Qts Vas, and Fs of your speaker - again get the tech specs from the speaker manufacturer webpage - and then enter the desired Qtc to get the interior volume of the box you want to build. Then take that value (called Vb) and use it in the Box dimensions calculator. Now this is easier than it sounds. Here's an example of my speaker specs.

My sub: Kenwood KFC-XW1202DVC (12 inch dual-voice coil sub)
Qts: 0.33
Vas: 3.23 (cubic feet)
Fs: 23 (Hertz)
Qtc: 0.9
(A value of 0.701 is true recorded sound, 0.9 gives a little more bass. Don't go higher than 1.1 or you will mechanically blow your speaker, think high compression pistons here.)
Hit Calculate.

The formula tells me that the optimal inner box volume for this sub is .516 cubic feet. Take that value and plug it into the Box Dimensions calculator along with two dimensions of your box (say height and depth in your case since you want a smaller footprint in your trunk) and it will calculate the remaining value. Add maybe an inch to one value - to account for how much space your sub takes up inside the box and you're done. For example

So I plug in these values:
14.5" x 14.5"
.516 (volume from the first calculation)
.75" (for my MDF)

and it tells me the last piece should be 6.77 inches. So I add an inch and the final exterior measurements of my box will be 14.5" x 14.5" x 8" to get the sound that I want - just a little heavier bass than it was recorded at.

Amplifier.

Get yourself a decent Mono amp (also called Class D), hook your two 10s up in a parallel wiring setup and enjoy the sound. Class Ds are expensive, so you can get similar results for less money with a decent 2-channel amplifier, again as long as you run the speakers in parallel. This means hooking them up together which decreases the load (Ohms). In otherwords, hooking two 8 ohm speakers up in parallel gives you a 4 ohm resistance, which the amp has an easier time powering.

If you got even one 10" subwoofer with two 4 ohm voice coils (called DVC, very common) you could hook them up in parallel, dropping your resistance to two ohms, and bridge your 2-channel amp to power them. That one 10" sub would pound harder than two SVC 10" subs on the same amp. Check the Speaker/Sub Wiring at the bottom of the site for how this is done. Again its a lot easier than it sounds.

I know its a lot of info, but PM me or post any other questions here if you have them. I'm happy to answer them. I've been doing car stereo installs as a hobby for a while now.

[jamis33]

Hey speedfoos I'm gonna try wiring my woofers in parallel rite now my only question is whether or not it will make my amp run harder and wear it out more?

[speedfoos]

The only issue would be the ohm stability of your amp. Most amps are at least 2 if not 1 ohm stable. So as long as you don't go below that, your amp will be fine. You amp will run stronger, but since the resistance (ohms) of your speakers are lower, the amp has an easier time. What subs did you get, and are they single or dual voice coil, and at what ohm? Most run of the mill subs are 4 ohms... Let me know.

[christmaspie]

Originally Posted by speedfoos

since the resistance (ohms) of your speakers are lower, the amp has an easier time.

Actually the lower resistance draws more current from the amplifier making it work harder and produce more heat. I've only seen maybe one two-channel amplifier that was truly stable into two ohm bridged. A mono amp stable into one ohm will usually set you back quite a bit.

We just opened the first BBY outside of North America and it was in China, not England.

[speedfoos]

Whoops, my bad. Thanks for straightening me out on that. Although I have a question. Is there a difference between say an amp pushing 100 watts RMS at 4 ohms and 100 watts RMS at 2 ohms? I would think the amp would working just as hard, or harder, to get the same output at a higher resistance. Let me know what you think.

Re: the Best Buy bit. That's alright, folks here wouldn't know what to do with a Best Buy - they'd probably add a convenience tax or something else equally ridiculous. I've only got another 1.5 yrs here before I'm stationed back in the States.

Just checked out your CarDomain page. Nice set-up.

[christmaspie]

The first thing of course if the different classes of amplifiers. Two and four-channel amps are almost always type AB. These are about 50% efficient with the other half becoming heat. A mono amp is around 70 - 80% efficient. So comparing the two is apples and oranges in and of itself.

An amp that produces 100 watts into two ohms will make less power in four ohms (ignoring JL audio amplifiers.) The thing that is most important, which you pretty much nailed, is not hooking up a sub load that is less than that which the amplifier can handle.

Mono amps - again usually the lowest you can go is two ohms, more expensive amps will allow you to go lower.

Two-channel amps - All are stable into two ohm but that's only stereo, when you bridge them they don't play well below four ohm (again with one or two exception.)

So, that Insignia two-channel amplifier shouldn't be bridged to the two four ohms SVC subs because the amp will get too hot and prematurely fail.

Hope you're enjoying your stay in England until you get back to the States.