Twilightoptics

In my 85 Iroc, I had one JL 10w3.... it was in a sealed box and the box fit just right... so that when I turned the hatchbox upside down, it would fit in the rear well pointing at the gas tank... and the box was about an inch and a half away from the front slanted wall of the well.. in parrallel.

I have an 87 camaro now, and it has a hatch motor so my box wont fit.

I was wondering if it will sound better if I make my new box having the sub pointed up to the hatch... or have it still point towards the tank like that. It sounded damn good that way... but I have nothing for comparison...

Which should I do?

mschwitz78

Your box will sound better and be louder if you point it up towards the glass. The reflection of the bass off the glass in a hatchback will increase db by 6-9db.

Schultzy89GTA

Paul,
Are you going to hang out with us at the gathering in a few weeks? If so you can listen to mine to get a comparison. I am running dual JL 10" that are pointed to the glass.



-Schultzy

FyreLance

Errr....

Twilightoptics

Yeah Schultzy I'll be there... maybe you can unplug one of yours! LOL I do have 2 10" JLs... but I don't have an amp to run both at the same time. I have one amp for my 6x9.. and then two others that would run a JL on it's on... the thing is.. my lights dim REAL bad with just 2 amps... if I put a 3rd on my Ampre usage will go through the roof.

harry's91rs

quote:
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Originally posted by mschwitz78
Your box will sound better and be louder if you point it up towards the glass. The reflection of the bass off the glass in a hatchback will increase db by 6-9db.
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I don't know if you can get that many Dbs. It will definitly be a noticable difference. I think it takes 10 times the power to go up 10 dbs, and like twice the power to go up like 3dbs, if I am correct. If I am wrong somebody correct me.

mschwitz78

Two times the power or speakers, or half the difference will increase db by 6db. 10db=twice as loud. I was also told by an IASCA judge and MECP instructor that reflection off of a hatchbacks glass will create a 6-9db increase.

mschwitz78

half the distance

Jim85IROC

iTrader: (2)

Unfortunately, you don't need to be a genius to be an IASCA judge. 6-9dB is crap. In fact, you'll find better results by facing the sub toward the back of the car, or toward the floor. The reason that you get added output by facing them toward the glass (as compared to forward) is that it provides a horn effect. Because the sound waves are so large, by focusing them all in the same direction, you get reinforcement by the reflected waves.

Now... if you stick the sub down in the well, in effect all you do is lengthen the horn and create a more focused origination point for the sound. Same effect as aiming them at the glass... only more pronounced. It's a "longer" horn with a more narrow originating point.

All in all, the effect is pretty minor. If you gain 3dB, you're doing pretty good.

Twilightoptics

All I know is my 500W 10" JL sounded better pointing at the gas tank... than my friend's 800W 12" Polk Audio DX pointing up.

Jim85IROC

iTrader: (2)

You can't compare that! A different sub will make 100x more difference than how you aim it.

All that proves is that your JL sounds better than his polk.

FyreLance

DISTURBthePEACE

do it like this, i tryed it with my old setup that had a box that fit in both places and towards the well was the the hardest hitting.
https://www.thirdgen.org/techbb2/sho...hreadid=146179

You have to scroll down a few posts to see the completed box. had a few friends with me to listen when I messed with the position of the old box, and we all agreed it hit harder facing the back of the car than it did facing up at the glass.

Eric86TA

I think when you had the box facing into the gas tank you were creating a second chamber in the well which is essentially creating a first order bandpass box in the trunk of you car. This will create a deeper bass but the bass response and clarity will drop. When you fire the subs into the hatchback glass your bass will drop but you should have a tighter harder hitting bass.

88redthunder

I seem to recall that 3dB is the the lowest volume difference that most people can hear. Like if someone asked you to turn up the volume, you'd probably turn it up by at least 3 dBs. Something like that. I don't think you'll get 6-9 dBs from pointing them at the hatch glass. If anything, I would think it would be the way Jim85IROC was explaining it, that pointing them down would be more pronounced.

Jim85IROC

iTrader: (2)

3dB is a very noticable increase in volume that anybody can easily recognize. Most people can identify a 1dB increase in volume, some even less.

In a direct a/b comparison, the ear can distinguish between small fractions of a dB, although the listener may not actually realize it. Play 2 identical systems, except that one's a fraction of a dB louder, switch between them, and the listener will think that the louder one sounds better. He won't be able to tell that it's louder, but he will think that it sounds just a little cleaner. The brain can detect incredibly small differences in SPL... it just doesn't necessarily recognize it as "louder". A human's entire ability to localize sound is based on the brain's ability to compute incredibly minor phase differences and incredibly small differences in SPL from one ear to the other. It's pretty amazing.

DISTURBthePEACE

There ya go, cardomain.com finally let me into my page so I could get the pictures URL's to post them.

AJ_92RS

And doesn't doubling the power (wattage) increase the SPL by three also?

AJ_92RS

DISTURBthePEACE,

That looks good, and I bet it sounds good also. It also looks as though it was relatively easy to do compared to the box that Rezn8r makes. Not dissin' him at all. I'm actually complimenting him. But my philosophy has always been K.I.S.S. Probably because I'm lazy. :sillylol:

Jim85IROC

iTrader: (2)

Approximately. Doubling your cone area (assuming all other conditions are equal) will give you an additional 3dB as well. That's why adding a 2nd sub makes such a big difference. You get 3dB more due to the additional cone area, plus you gain 3dB because halving the impedance of the load on the amp will result in approximately double the power from the amp.

Twilightoptics

Where the hell do you all go to learn this stuff? When do I get to sign up for the class?

Jim85IROC

iTrader: (2)

Experience. I got into this stuff when I was 16 years old, and made every mistake imaginable. Mistakes are the best way to learn.

I was also fortunate to be able to work in car audio sales all through college, and was surrounded by people that were able to answer all of my installation based questions. Couple this with an electrical engineering degree, and you manage to learn an awful lot of valuable information.

Unfortunately, I'm not involved with car audio on a daily basis anymore like I was when I was in college, so I'm starting to get out of touch with all of the new goodies. I'm really hoping to be able to pick up a part time job soon so I can get back into touch with all the new toys.