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Old 11th September 2009, 12:49   #1
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Default Sub woofer Boxes(enclosures)

I have 2 JBL subs in my car (2000 Lancer) Driven through a 600 Watt 4 channel amp. The sub box i have is extreamly leaky(leaks a lot of air) and occupais a lot of space, taking out the spare wheel is a big problem. I reasearched a lot and found out that there is a reverse mounting technique, more than quality this serves utility(correct me if i am wrong). i have seen frank's setup in his previous car and i thought of replicating it. I know it was up for sale but getting something that huge from mumbai will involve a lot of cost and will turn out cheaper to make one here, and not to mention the sheer fun of DIY. Now my questions are,

-->Can all subs be reverse mounted, or its advised that subs above a certain ratings are mounted this way

-->How do you protect the back of the cone which is exposed, i have seen them in Frank's setup again but are the available if yes how much?

-->Does this produce less bas than the normally mounted Subs?

--> How to effectivly channel the bass to the cabin. i have a 5" hole in the rear parcel tray, is that sufficient?

--> Finally can someone help me with the designs/dimentions for a sealed box


Mods: kindly merge/move to appropriate threads.


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Old 11th September 2009, 14:07   #2
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No, baba @pramod, mounting a sub in reverse is for show off only, and will not help in taking out the spare wheel easily. In fact, Franks' current JBL sub would be too heavy to mount outside, and whole assembly will keep toppling over.

One normally doesn't protect the cone rear in such mountings, possibly because one does not anticipate anyone else sitting in the boot dancing & waving a sharp object around to the beat of the music.

The 5" hole is probably not sufficent, but since the rear seats are not acoustically opaque, bass would be entering the cabin by that route too.
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Old 11th September 2009, 14:21   #3
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Thanks a lot deralte, i also though it will keep on toppling. So the idea of sub mounting in reverse mode is out of the window. However the current setup does not give a tight punch.

In my early car(esteem) i had a single pioneer voice cooled sub, mounted in the rear parcel tray. This setup was far more superior than my current setup. i understand (may be wrong) in that case the entire boot acts as a resonance box however now wne they are mounted in a sealed box i dont get a good sound effect. I feel its mainly because of multiple holes drilled to fix the sub and Amp, i als have a 2" Dia hole to tunnel the bass throug each chamber, this design seems hedious after reading numerous posts and seeing numerous setups, Kindly guide me with the correct design for the setup.

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Old 11th September 2009, 14:53   #4
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What JBL subs are these? If you can get the Specs would help in determining what the optimum enclosure can be.
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Old 11th September 2009, 15:02   #5
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* The problem is quite likely the box volume that each sub has
* With the hole, each subwoofer is actually seeing approximately double the volume needed
* Seal that hole connecting the 2 compartments - let each sub play in it's own sealed box
* Forget about the small holes which have screws - that leakage doesn't affect anything substantially. If you are really paranoid about it, seal all possible holes and cracks from the inside of the box with a putty of fevicol and sawdust
* You could also try reducing the volume of the box to see if that improves the bass. Use bricks or scrap blocks of wood temporarily to reduce the volume. Each brick is about 0.03cft, I think
* Also, double check the polarity of the speaker connection. If one of them is anti-phase, it will degrade the bass
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Old 11th September 2009, 15:23   #6
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1. It would not make much difference if one single chamber is used instead of 2 by adding a baffle in a single enclosure. With a single chamber and 2 subs, it would act as one driver in there plus, both the subs get the same amount of power. Yes, it may make bass may be less punchy and may be slight less effective on low volumes.

2. Leaks do change the way the sub behaves in a sealed enclosure. Leaks can be also sealed with using Silicon sealant.

3. What would help is if you could mention what's the current sub enclosure size and the T/s Parameters of the sub or the sub model. IF the enclosure you are using has a higher Qtc which means smaller enclosure than required, it would result in some peaky response over the freq. To have a linear response it's best to keep the Qtc lower.

4. And as DerAlte mentioned check for the polarity which might result in phase shift.

Last edited by Invinsible : 11th September 2009 at 15:29.
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Old 11th September 2009, 15:38   #7
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everything you said just flew over my head . I have those 1000 Watt JBL subs and 600 Watt Silicon 4 channel amp. I am using a office comp which does not allow uploads so i cannot upload pics of my enclosure but i will try to explain how it looks, It is a rectangular box where in the the base is wider than the top. and the subs are mounted on one of the longer sides. the two compartments are sealed seprated inside by a partition. there is a 4" hole on the top of each chamber. The installer used a big file to file the edges of the hole created to mount the sub so the finish is not good. I have 2 round connectors(made up of plastic) insatlled at the back of the box. This is connected after cutting a similar sized hole in the back of the box. The dimention of the box should be 3x1.5 FT. I experimented with the polarity a lot and now it sounds decent but when i took it to a friends shop for changing the cables my friend said its leaking a lot of air thats why it sounds terrible. he then suggested to get rid of one sub and place only one in the parcel tray.


So if i confused you each side enclosure has 3(big) holes, one badly filed 12" hole for the Sub, one 4 " hole for the bass channel and one 4" hole for the connector, there are numerous small holes made by screws

Pramod

Last edited by pramodkumar : 11th September 2009 at 15:45.
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Old 11th September 2009, 15:53   #8
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Quote:
Originally Posted by pramodkumar View Post
there is a 4" hole on the top of each chamber. The installer used a big file to file the edges of the hole created to mount the sub so the finish is not good.
Pramod
Sounds like the installer tried making a ported enclosure without actually using a tuned port tube for the same. I suggest you measure the exact outer dimension of the enclosure i.e height, weight and depth. Also, if you can tell us the Model no of the JBL sub will help. How are you using the 4 channel amp ? How is it wired to the 2 sub ? ALso what size the sub is ?
At times choosing wrong enclosure could also result in poor sound quality from the sub.
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Old 11th September 2009, 17:48   #9
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Quote:
Originally Posted by Invinsible View Post
Sounds like the installer tried making a ported enclosure without actually using a tuned port tube for the same. I suggest you measure the exact outer dimension of the enclosure i.e height, weight and depth. Also, if you can tell us the Model no of the JBL sub will help. How are you using the 4 channel amp ? How is it wired to the 2 sub ? ALso what size the sub is ?
At times choosing wrong enclosure could also result in poor sound quality from the sub.
For the subs i have the one mentioned in the link

http://www.techronics.com/images/products/823.jpg

I will post the exact dimentions of the box, the amp has 2 cannnels bridged for each sub but som how the sound quality and bass was bad so i bridged one side and connected one sub(it sounds great) connected another sub to the other 2 channel in such a way that it gives the maximum thump (but not bridged there is no output when bridged but both the channels are working seprately). I recently changed the wires to improve things, and there is some improvement but to a great extent as most of the people with 2 subs say they have.

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Old 11th September 2009, 18:54   #10
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I tried looking for Specification / T/s Parameter details on it but I don't think it's mentioned on their site. You must have got the owners manual along with, check if they have mentioned anything on T/S parameters if not PM Sam Kapasi, may be that could be of some help. To determine a sealed enclosure one would need to get the details on rated Fs, Qts and Vas.
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Old 12th September 2009, 00:22   #11
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Talking aperiodic enclosure

friend,
check my post, it has some info about some tweaks u can try on your existing sub enclosure
http://www.team-bhp.com/forum/ask-gu...s-mistake.html
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Old 14th September 2009, 11:32   #12
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Quote:
Originally Posted by Invinsible View Post
I tried looking for Specification / T/s Parameter details on it but I don't think it's mentioned on their site. You must have got the owners manual along with, check if they have mentioned anything on T/S parameters if not PM Sam Kapasi, may be that could be of some help. To determine a sealed enclosure one would need to get the details on rated Fs, Qts and Vas.
I forgot to take the manuals, i was more happy with the JBL stickers. I just wanted to know the best way to design a enclosure with minimum space required in the boot, i will post some pics of the enclosure tonite, my home internet is not working as of now.

Quote:
Originally Posted by althaaf View Post
friend,
check my post, it has some info about some tweaks u can try on your existing sub enclosure
http://www.team-bhp.com/forum/ask-gu...s-mistake.html
When i brought these subs, they used to sound pathetic, now they are better after adding those two tunnels but, i feel they can be improved further. it dosent feel like the setup has 2 JBL subs. plugging the hole cannot be the only solution i think a complete redesigh of the enclosure is on the cards, anyways my car is undergoing a complete paint job now, expected to be back by first week of OCT. till then i thought i can sort this out.

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Old 16th September 2009, 21:37   #13
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Pics of my current enclosure.
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Old 16th September 2009, 22:13   #14
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The enclosure looks like little bigger in size. One needs the T/S parameters of the sub to determine what size enclosure will fit the best.
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Old 17th September 2009, 11:48   #15
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Guys, please do not forget an important factor during Sub Boxes is lots of damping inside sub box. Please Google Search for this.

Also if you have a real powerful amplifier. Closed Boxes are prefered as they give tighter bass which is better.
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