car audio help

zilla · 07-29-04, 07:43

Hi all,

i made a new speaker box ( http://forums.vwvortex.com/zerothread?id=1514481 ) to replace my pre-fab box.
the box has been glued and screwed and silicone applied on the inside and outside of the seams. I put some weatherstripping around the speaker opening and screwed the speaker down (JL 10W6, wired in parallel).

i wired everything up and..... was disappointed. using the same gain and bass boost settings on the amp (JBL 300.1) and head unit, the sub was barely audible compared to when it was in the prefab box.

I thought i had reversed the polarity of the speaker terminals, so i swapped that and tried it again, a bit better, i think, but still very quiet. when i used these settings int he pre-fab box, it would be *LOUD*

Would there be that much of a difference in loudness between a cube-type prefab and my box or does my box have a leak or some other wiring problem in it?

or do i just turn up the gain and bass boost on the amp and enjoy

thoughts?

Tim

BDawg · 07-29-04, 07:52

There's so many things that can affect the SPL of a speaker.

Do the boxes have the same volume? Are the materials equally resonant? How much porting is present on each? Is one a sealed box?

BTW, you did an excellent job on the look.

317indy · 07-29-04, 08:20

Maybe your sub just doesnt have enough space to push. Take the subwoofer out and put it in a bigger box and then leave everything the same way, If thats the problem then just cut out a bigger hole.

Edit: Actually you should have just fiberglassed the box encloser in the spare tire well if thats where you did it. Line it with masking tape, or a big sheet and then lay the material down, lay the resin down let it dry, take it out and make it thicker with the material and resin then attach it to the false floor and make a seal with caulk and line the rear with dynomat.

zilla · 07-29-04, 09:38

i wanted to stay away from fiberglassing because I had no experience with it at all.

I made sure that when i designed it that the internal box enclosure was within spec for the speaker. I also took into account the driver displacement and the displacement of the internal braces.

I'm *pretty* sure that the box does not have any leaks in it. Like i said, i siliconed all of the seams, inside and out.

I guess my main question is can there be that much of a difference in loudness from a pre-fab box to a custom box?

edit: i don't know the internal volume of the pre-fab. i just by looking at it i'd say that it was about the same and it had some of that white pillow stuffing-like filler in it.

both boxes are sealed. i didn't put any of that filler stuff into my new box.

dcswd · 07-29-04, 11:18

did you have your old box in nearly the same position? or is this a new spot?

When I was messing around with my system, I tried out a lot of different positions for the box. I found that it was significantly louder if I had the sub firing towards the back of the car with the box up against the seats.... and it wasnt so loud when the opposite was done.

Other than that, im not really sure. The spot you put your sub seems to be a popular location.

zilla · 07-29-04, 11:23

yah, the prefab box was firing towards the rear of the car. The new box has the sub firing up towards the roof.

I don't think it's an issue of resonance in the car, tho, because i'm not seeing the cone move as much.

will a leaking sealed enclosure affect the movement of the speaker cone?

IndigoGTI · 07-29-04, 11:56

How close was the original enclosure to the rear of the car? if it was close to the back of the car, the sound would have been reinforced because it was reflecting off of a solid object. If your speaker is firing straight up into the trunk, you don't get this same effect. I'd suggest looking into adding a port through your rear deck into the trunk to allow more sound to pass through to the cabin. A side benefit to this is better sound quality as the bass isn't being muffled by the back seat and whatever is covering the rear deck.

To answer your last question, yes, a woofer mounted in a leaking enclosure will move more than one in a perfectly sealed enclosure.

Try adding some polyfill to your box, your sub will sound like it is in a slightly larger enclosure.

Double check your amp gains, crossovers, and connections, you may have bumped something in the installation process.

zilla · 07-29-04, 11:59

indigo: I'm doing the install in a mk4 golf. i went with a sealed enclosure over a ported one for the sake of space.

the prefab used to be up against the back seats firing towards the hatch at a slight upward angle.

When I get home tonight i'll pull the speaker again just to be 100% sure that I do have the positive and negative terminals wired correctly and then i'll play with the gain and bass boost.

Thanks for the help.

edit: speeling

IndigoGTI · 07-29-04, 02:40

That's strange you are having a problem, definitely check the phase of the speaker, and make sure you aren't shorting the voice coils together.

I can't look at Vortex here at work, I'll check out your work when I get home.

zilla · 07-30-04, 12:46

OK, I fiddled with it last night and it seemed to be a combination of a loose wire connecting the two voice coils, lack of polyfill, and lack of amplifier tuning

On the plus side, the sound is great. I think I just need to play with the settings in the HU to tighten up the sound a bit.

Next step is to figure out if I should install any air circulation fans and if so how to mount them flush with the surface.

IndigoGTI · 07-30-04, 02:09

Glad you figured it out. I assume the fans are for the amplifier? Look on ebay for a squirrel cage fan that will blow across the heat sink of the amplifier, they are very quiet, and put out a lot of air for their size. I think Stinger makes one.

zilla · 07-30-04, 02:34

it's to keep the amplifier cool, but not so much to mount on the amp as to mount on the top of the false floor to blow the hot air from underneath out into the hatch area.