Subwoofer/ Amp question
 

I got a pair of 12" woofers and an amp from my brother a few weeks ago.
speakers - http://www.soundcity.com/products/15166.html?tr=froogle
they are 200watt rms/ 400 peak @ 4 ohms punch XLC RFP2412
http://webpages.charter.net/dheyvis/speakers.jpg

amp - rockford fosgate punch 250a2
http://webpages.charter.net/dheyvis/amp%20specs.jpg
http://webpages.charter.net/dheyvis/amp%20ohms.jpg

I am running them from a JVC cd player with preamp outputs.
this one -- http://www.jr.com/JRProductPage.process?Product=4048728

I have it all wired with monster cable and monster oxygen free speaker wire and very large monster power and ground wires with the power lead up to the battery. (I didn't shell out for the monster cable, my brother gave me his :p )
It is in a box in the trunk right now facing up

I have it wired in stereo - one speaker per channel and it just doesn't hit very hard. I am sure the speakers are in phase.
This is how I hooked it up
http://webpages.charter.net/dheyvis/wiring%20stereo.jpg

I tried wiring it bridged in mono and the amp would heat up and shut off. It hit pretty hard though.
I had it hooked up like this (only with 2 leads on each so I could run both speakers)
http://webpages.charter.net/dheyvis/mono%20wiring.jpg


Am I doing something wrong or is this amp just too small for the speakers?
Also I am not too smart on the 2 ohm 4 ohm thing. If I have it wired in stereo that makes it 2 ohms, right? So is that bad for my 4 ohm speakers?
It sounds better and feels better if I leave the back seat folded down but I don't want to ride around like that all the time.

There are settings for gain and crossover range on the amp and I've played with them along with the equalizer on the stereo but I can't get it to hit very hard without distorting.

Thanks in advance for any ideas. I am an amp and subwoofer n00b.

250 watt peak amp is weak in the first place and those subs can't handle much more. Also the box they are in can make a huge difference. For refference I used a 17 inch 3/4" Triangle box in my old integra with 200 watt amp it hit as hard as my 500 watt amp comined with the newer Qlogic boxes. Don't for get that your also trying to go through the trunkn and all of its stuffing.

i would keep it in mono and lower the gain. wire the speakers in a parrallel not series, and get a beter box. also, face the speakers to the rear of the car not up.

The box is 6"x14"x30" about 3/4" thick fiberboard. I guess that makes it about half the volume I need for these speakers.
http://webpages.charter.net/dheyvis/enclosure.jpg

Why point them to the back? Don't I want them pointed towards the front?

I also just figured out I had the +/- mixed up from speakers to amp. Both were the same, but - on amp to + on speaker. Wires weren't labeled so I unscrewed the speakers to check inside the box.
It seems to be better already after fixing it but I don't understand why - I thought it didn't matter as long as the 2 speakers were in phase.

This is what mono in parallel would look like, right?

http://webpages.charter.net/dheyvis/mono%20wiring2.jpg

yeah, thats mono parrallel.

point the box to the back cause the sound to reverb off the trunk. low freq require air space to be herd/felt, pointing them to the back increases the amount of air the waves pass through before hiting your ears. trust me, turn them around and their will be a thump.

With two 4ohm speakers, you can only run these combinations:

Two channels at 4ohms each
Mono at 8ohms (speakers in series)
Mono at 2ohms (speakers in parallel)

Mono in parallel (as you've drawn out) will give you the most thump, but it'll also load your amp pretty heavily and might let the magic smoke out. I don't think your amp is rated for that. If you had two 8ohm speakers, you could run in mono at 4ohms in series. That would be best. Unfortunately your best bet is stereo at 4ohms each, which only gives you 100 watts per speaker. That's 200 watts total - not very much. If you ran one speaker bridged, you'd be running at 320 watts - still not very much.

Usually, two speakers at 100 watts each will outperform one speaker at 200 watts. Sometimes they won't, and sometimes two 75 watt speakers will outperform one 250 watt speaker. It varies. I'd suggest trying the one speaker, 320 watt option, just to see what difference it makes.

I'm pretty sure I got the math right on all that. Double check your equipment's specifications against reality.
Good thinkin' including the spec sheets. It helps when we know what you're talking about.

Ok, box was too tall to stand up anywhere but right at the rear of the trunk so I put it there and pointed it forwards to get more open space in front of the speakers. The sound difference is incredible. You were right - now it thumps. Thanks! :D Fear Factory never sounded so good.

I'll try the mono wiring and also only one speaker next to see if it gets even better.

That reminded me of the time I pulled one out and stuffed my sleeping bag in the other half of the box. That was still kickin even thought the box was comming apart then (beating so hard 24/7 like....and a high school project)

Does anyone have a good wood box design for 2 - 12's facing rear? Been searching lockers and posts and it looks like it would be pretty hard to do without gutting the trunk out or having the speakers angled upwards. Got almost exactly 12" height in there.

In theory will it sound like crap if I have the speakers facing rear about 2" from the trunk?

Here is what my haggard system looks like now

http://www.subaru-svx.net/photos/fil...suby/29093.jpg

http://www.subaru-svx.net/photos/fil...suby/29094.jpg

I used to have Punches. ):

You could always fold the rear seat down and set them there. Plenty of space to travel and no insulation to hamper the reverb. ;D

edit: your speakers are upside-down. :D

immortal - UberRoo is correct, wiring the two woofers in parallel will let the smoke out sooner or later - think of it like an "almost" short. The current will try to flow at a rate the output can't handle.

If you can't, or don't want to switch any components, the easiest way to get louder sound would be to make ported boxes - each ported enclosure will produce almost the sound level of two sealed boxes - but now you've used up the trunk - sorry no such thing as a free lunch.

I would suggest you cruise through the following web page to fill in some answers: http://www.bcae1.com/

Many subs especially the lower power ones are designed to be in a sealed box.

Sealed boxes are popular because they're usually smaller. That doesn't mean they're always better and a design that gives nearly equal sealed-type performance is not always smaller. Ported boxes are often used because you can really make them wail, but not in every application. I have a ported enclosure that barely hits at all, but it easily produces sub-sonics - very low frequencies. There's just too many variables.

Broad statements about what enclosures work best are kinda iffy. The design of the speaker, the size of the amplifier, and of course the design of any type of enclosure can turn everything on it's head. Generally, the documentation that comes with the speakers will specify the optimal enclosure. Certain ported or sealed enclosure will give your subs a sweet spot. There are calculators that can tell you what enclosures will give you a particular type of performance. They’re tricky to manipulate, but some time spent researching it can really pay off. I think a ported enclosure would probably be the best in your case, but I wouldn't know for sure without running the numbers. It's easier to just ask the manufacturer.

One thought: Make sure your box is tightly sealed. Any air leaks, even small ones, can really kill performance. I threw a box away because I couldn't find all the screw holes in it. I replaced it with another identical box (without leaks) that performed fantastically. It was an SPL box. I fed it an obscene amount of power and drove around with ear plugs in. :) It was a lot of fun for about a week, but I quickly cannibalized all the parts for other applications.

:D :D yeah, the wires come out on that end and were a little too short to reach the amp if I had the box right side up. :p :)