Im sure you remember me from my post "Fiberglass project with pictures". Everything went great, there were no leaks, everything was 100% solid...except for one thing. It sounds bad.


The thing i didnt take into account is the 'subwoofer loading'...haveing it bounce off of the hard surface so u can hear the whole soundwave. I thought it would do this in the corner but i was wrong.

Just to make sure it wasnt the box that made the sub sound bad, i took my box, positioned it so the sub was against the rear seat, pointing to the very rear of the car. Then it sounded great.

Heres my question:

Should i scrap this project or should I try to fix it? The fixing option would require(as i see it) cutting off everything off of the top(where the fleece was pulled over) so i just get to the point where i have just the bare mold piece of the trunk. Then I would make a new speaker ring, make it so it would point towards the trunk lid and then refleece and fiberglass it.

The second option is to scrap this project and make a new box that is at the rear of the car.

Any opinions would help.

This is how the subwoofer is pointing, its hard to see how its pointing in the picture after this


This is it installed, without carpet yet.


This is a diagram of the trunk only. The aarows are pointing to where the speakers are pointed to in the trunk.

 

Stuff the enclosure full of PolyFill and see if that makes a difference before you do anything drastic like cutting it apart...

edit after thinking a bit: Also, did you try to at least approximate the volume in the box to meet the requirements of the sub? Maybe the box is just too big?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by B18C_EJ8 &raquo;</TD></TR><TR><TD CLASS="quote">
edit after thinking a bit: Also, did you try to at least approximate the volume in the box to meet the requirements of the sub? Maybe the box is just too big?</TD></TR></TABLE>

its exactly .75 cubic feet. when i pointed the sub toward the back of the car, it sounded a lot better, so its not the sub enclosure thats the problem, its th way its pointed

I know this may sound odd but this is the most accurate box iv made yet. itsa very solid build and id be 130% happy if it was pointed differently, but im thinkin to do that, im gonna need to make a custom box in the rear of the trunk which shouldnt b too bad if i have to


Modified by silentblackhat at 7:45 AM 1/20/2006

 

Stupid question maybe, but you're testing this with the trunk closed, correct? Might seem silly, but I had to ask.

 

Since bass is omnidirectional, it really shouldn't matter which way it's pointed... Granted, most people say you gain 3db by pointing subs toward the back as opposed to them firing into the back of the back seat, but the angle on the side of the trunk shouldn't matter... The QForm custom enclosures have the sub firing directly across the trunk as in the pic below, so IDK what's causing your problem... When you say it sounds "bad", what does "bad" mean? Muddy/Muffled? Not as loud?

 

I would also add, try changing the phase of the sub, reverse the speaker leads on the amp. 94

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fcm &raquo;</TD></TR><TR><TD CLASS="quote">I would also add, try changing the phase of the sub, reverse the speaker leads on the amp. 94</TD></TR></TABLE>

you beat me to it,lol I heard the q-logic box and it sounded great. yours should do the same thing. You said you made the box .75. Did you factor in the subs displacesment? It would drop the box down to .65. you could use polly fill to trick the sub into thinking it was in to a bigger box.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by B18C_EJ8 &raquo;</TD></TR><TR><TD CLASS="quote">Stupid question maybe, but you're testing this with the trunk closed, correct? Might seem silly, but I had to ask. </TD></TR></TABLE>
lol yeah i am doesnt hurt to ask tho

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by B18C_EJ8 &raquo;</TD></TR><TR><TD CLASS="quote"> The QForm custom enclosures have the sub firing directly across the trunk as in the pic below, so IDK what's causing your problem... When you say it sounds "bad", what does "bad" mean? Muddy/Muffled? Not as loud?

</TD></TR></TABLE>

Well by the picture that i see of the qform, it points toward the sides of the car more. i know it doenst look like it but the angle that i took the pic of my box in my car, the sub in mine is pointing toward the front of the car more, maybe the qform makes it boucne off of the sides of the car more(like bouncing it off of the rear of the trunk).

When i say it doenst sound as great, i dont hear alot of detail in songs. The bass also sounds a little muffled, like it has no 'flavor' to it.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fcm &raquo;</TD></TR><TR><TD CLASS="quote">I would also add, try changing the phase of the sub, reverse the speaker leads on the amp. 94</TD></TR></TABLE>

WHen i do that, would it put the subs out of phase, and each wave cancel each other out? ill try it tho. Do you mean switch one subs leads or switch both leads?
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by wrx-killer &raquo;</TD></TR><TR><TD CLASS="quote">

You said you made the box .75. </TD></TR></TABLE>
Yes
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by wrx-killer &raquo;</TD></TR><TR><TD CLASS="quote">

Did you factor in the subs displacesment? It would drop the box down to .65. </TD></TR></TABLE>
from what I saw on the data sheet, the box needed to be .75 total.



what im wondering is, when i have both subs facing the rear of the car(when they are against the rear seats pointing toward the rear of the car) the subs sound great.

ALso i am wondering if i point the subs toward eachother, will it mess the sound up also? It looks to me like the qform sub points toward the side of the car more than mine. thanks for the replies allready tho


Modified by silentblackhat at 12:49 PM 1/20/2006

 

Polyfill. That's all I can say. Bass is omnidirectional. But when the sub is firing away from your ears , the soundwaves stretch. Which makes it seem louder , but the notes aren't precise. I would also like to mention that if you look at alot of crazy installs , subs are firing in all types of crazy directions. So in the long run the placement should not affect bass all that much. It has alot more to do with the tuning. It's just like a motor. Tune it till it's perfect for you. Switch the phasing. Add polyfill to the box. Try some dynamat inside the box. Check your crossover points. Try some new ones. Did you stop to think that maybe the box is flexing? Try to make it stronger. Make the box itself soundproof. How about some sound deadening behind the box on the bodypanels? There is alot more you need to look at before you go tearing it apart. Good luck! And the box looks great!

 

where can i get polyfill at? and is it expensive?

the whole trunk is dynamatted, even the fenders.

I really doubt the box is felxing, its really think and anout 230wattsrms goin to each sub. Also it is 100% air tight, i filled it with water b4(of course i let it dry out b4 i put the sub in ) and it was water tight. also when i put my sub in, i can feel that no air is esacping when i try to press it in a little. ill try a few things tonight that was suggested. its just darn cold out!

by the way when you say change the phase, do you mean put one out of phase or do u mean switch the + and - on both subs?

 

It's gorgeous here! Well it was.
Polyfill you can get at the arts&crafts section at Wal-mart. It's the stuff they stuff pillows and animals with.

 

well im off to walmart then! ill get some of that stuff. do i use about 1/2 ound for my enclosure? i read somewhere that u use about 1/2 ound for every cubic feet

 

It should be 1 and a 1/2 pounds per square foot.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by silentblackhat &raquo;</TD></TR><TR><TD CLASS="quote">
its exactly .75 cubic feet. when i pointed the sub toward the back of the car, it sounded a lot better, so its not the sub enclosure thats the problem, its th way its pointed
</TD></TR></TABLE>
2 things. How on god's green earth do you know for a fact that it is "exactly .75 cubic feet"?! You've made a fiberglass enclosure which is contoured to the side of the car. And the fleece shrinks when the resen is applied. So there is pretty much no way to be exactly sure of the volume size, especially if you've by chance forgotten to add in the driver volume when making the box. Second thing. The reason your probobally getting bad sound is because the two speakers are cross firing. Meaning that the sound waves are crossing. (Even though bass is omnidirectional, this still happens.) The Q-form boxes are placed in that location, because it's a great spot for a single subwoofer. Not multiple. You will very very rarely never see subwoofers pointing towards (or crossing) eachother. The only time i've seen it is in a bandpass box.
I have a similar problem which involves my loud, deep exhaust. When i'm at a certain rpm the bass sounds like crap, if present at all. The different bass tones can cancell others out.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by zumiez007 &raquo;</TD></TR><TR><TD CLASS="quote">
2 things. How on god's green earth do you know for a fact that it is "exactly .75 cubic feet"?! </TD></TR></TABLE>
the thing that i did was add water in the box to make sure there was no leaks. the bucket i used to fill the water in is a perfect cylinder. i used the cylinder volume formula V = Pi*R^2*Height to figure out how much water i needed to put in the bucket(all i had to find was the height where to fill it up to). i filled it and it was exactly .75ft^3. the tech sheets say that the driver dislacement is included in the .75ft^3

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by zumiez007 &raquo;</TD></TR><TR><TD CLASS="quote">
The Q-form boxes are placed in that location, because it's a great spot for a single subwoofer. Not multiple. You will very very rarely never see subwoofers pointing towards (or crossing) eachother ... The different bass tones can cancell others out.</TD></TR></TABLE>

thats what im thinking. i went out to get the polyfill and im going to put that in in a bit. i just stopped by my work place to get somethin to eat so after dinner im going to take the other sub out and see how it sounds with just one. If it sounds really good with just that ill probably just package up my other subwoofer and store and ill cancel my extended warranties on both of them to save some money. im keeping one packaged up so incase this one im using blows, ill have the other one to install, while saving money on the warranties(both warrantys are almost enought to get another sub at reg price)...i got them buy one get one free on sale so thats y im not takin the extra one back.

What I will also try is pointing the subs more at the backseats and see if that solves the crossfiring.

ANyways thanks for the ideas and comments, they have been helpful so far. Any more ideas are welcomed.
Ill let you all know what goes on after im done testing some things out


Modified by silentblackhat at 4:47 PM 1/20/2006

 

I have a similiar problem. I cant increase my box size so I'm screwed.

I need to find a driver that works in the volume I have. NSX has no room for a fricken sub.

Using water is what I use to measure volume.

 

sound waves stretch - what will I hear next on this damn board.

Here's the issue, the sub box is not loading properly with the car. The two are not coupled to each other. That's why the box sounds better when pointed rearward. flip the box upside down to position it so the sub is in the corner and points to the rear, also try it so that it points to the other side of the trunk - so that it points parallel to the rear axle - assuming it had one

find out where it sounds best, if none of these directions do it for you, then go back to having them firing reward.

It's a phase/coupling issue

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rcurley55 &raquo;</TD></TR><TR><TD CLASS="quote">It's a phase/coupling issue</TD></TR></TABLE>

That would be my guess also

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by silentblackhat &raquo;</TD></TR><TR><TD CLASS="quote">where can i get polyfill at? and is it expensive?</TD></TR></TABLE>

fabric store - cheap

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">by the way when you say change the phase, do you mean put one out of phase or do u mean switch the + and - on both subs?</TD></TR></TABLE>

When you talk about phase, there are two things to remember, electrical phase and acoustical phase. Think back to that sine wave in your trig class. Changes in phase will shift the wave down the x-axis, but the wave form stays the same in amplitude and frequency.

Electrical phase means that all the + and - terminals are hooked up to the + and - terminals of the amplifier correctly. Now here's the key - just because you are in electrical phase, doesn't mean things are in acoustical phase!!

Remember, your speakers are located at different distances from your head, to compensate for the time shift, it's often a good idea to change the phase of individual drivers to get the best sound. This is ESPECIALLY true for your subwoofers. They can sound drastically differnt when the phase is flipped.

So everyone should do themselves the favor of playing with the phase of EVERY driver in their system, trying out EVERY combo before they get set on how the car should be. This is as important as setting gains, x-over points, and x-over slopes. This should all be done before even considering touching an eq

To change the phase, flip the + and - terminals at the amplifers. GENERALLY, aka 9/10 times, you want the subwoofers in phase with eachother, but they don't necessarily have to be in electrical phase with the rest of the system.

Just as an example - in my car, with the subs in phase to the system - I get little bass response, and they are totally localized to the rear of the car, If I flip the phase 180deg, I get more output, and the subs are now located up in front on top of the dash - just a simple switch of phase can make all the difference in the world. If all of you flipped the phase on your midbass in your doors, I'd almost guarentee (without using ta) you'd all get a much stronger center image then you ever could with them in phase (of course at the sacrifice of midbass response)

so experiment a bit and get back to us...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by silentblackhat &raquo;</TD></TR><TR><TD CLASS="quote">where can i get polyfill at? and is it expensive?

the whole trunk is dynamatted, even the fenders.

I really doubt the box is felxing, its really think and anout 230wattsrms goin to each sub. Also it is 100% air tight, i filled it with water b4(of course i let it dry out b4 i put the sub in ) and it was water tight. also when i put my sub in, i can feel that no air is esacping when i try to press it in a little. ill try a few things tonight that was suggested. its just darn cold out!

by the way when you say change the phase, do you mean put one out of phase or do u mean switch the + and - on both subs?</TD></TR></TABLE>


switch it on one speaker. flip the neg and pos

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rcurley55 &raquo;</TD></TR><TR><TD CLASS="quote">
It's a phase/coupling issue</TD></TR></TABLE>
I didnt get to testing things out but, i will tomorrow. I got the polyfill at walmart for $2.50. Even tho it wont help with the phase issue, ill put it in there anyways.
Ill post how everything goes. Thanks for all the help so far!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rcurley55 &raquo;</TD></TR><TR><TD CLASS="quote">sound waves stretch - what will I hear next on this damn board.

</TD></TR></TABLE>
They do stretch over distance. Read a book.

 

what book would this be??

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EBP_SI &raquo;</TD></TR><TR><TD CLASS="quote">what book would this be??</TD></TR></TABLE>
ALL sound waves , light waves , radio waves stretch over distances.

 

Your box size is fine. Problem is your subs cancel each other out, 'cause they cross their soundwaves. That's why it sounds a lot better when you place them against the rear seat facing the back of the trunk. You can even try playing only 1 sub at its designed location and it should sound like it should.

Since your subs handle only 250wrms, I would just get 1 sub that is capable of 500wrms and then I don't have to waste time and money on 2 fiberglass boxes, and also it is much easier in the end, installing 1 sub, comparing to 2 subs. And also 1 sub takes up less trunk space. I see no reason for having 2 subs, other than it looks cooler that way.

If that's too much trouble for you, then I would just redo the ring position and do the wrapping, etc, all over again. But make sure you test it out this time. Angle your current sub boxes as they would be in "version 2" of your project to make sure it doesn't do that again.