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I am still trying to think of ideas to save trunk space, but keep most of my Bump...so Clamshell came to mind.

So basically if someone can answer a few questions about running my 4 subs clamshell from People who knows about shiva (Lud or WR ) or people who just know about clamshell in general (prolly Lud and WR as well ).

I checked the JL tutorials for isobaric applications and they didn't go into to much depth on what the advantages and disadvantages are. Anywayz, here are some of my questions:

1. Would I be able to run 2 sets of Shiva Clamshell in my box of 1.4 chambers each? I have read some articles on Clamshell saying that you only need half the size box...does this mean that it will be like using a box that is 2.8 cubes? Basically will this set-up work if I were to go with it?

2. What would be the advantages and dissadvantages of running Clamshell (I did a search on this and Lud had a few points but I was wondering if there are any others). Will I lose a lot of SPL? Will it sound better or worse IYO? Is it just going to be the same as just running two?

3. For those of you that have worked with Shiva, Do I need to put any type of gasket between the two speakers? Can I just use double sided tape to keep air from coming out? Will the surrounds rub if I don't put a barrier between the two? Will that foamy black ring at the top of the speaker leak air no matter what?

I know it is a lot of questions...I am just excited about maybe trying something new, and the possibility of taking one of the boxes out of my car.

 
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Whoa, check out the numbers that this guy hit with a Clamshell set of Tempest (scroll to the bottom). Imagine with 4 Tempest (which would theoretically be possible to fit easily in the trunk of a civic if it is true that only around half the box space is required)!!!

Also, I am still searching the net for people who have ported clamshells...even though I don't have a saw maybe I could cut a port with a Dremel ( would that be possible to those with a dremel?) if 1.4 cubes is enough for a Shiva clamshell. :devil: :devil:

 
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in an isobaric setup you halve the area of the box. so for a pair of clamshelled shiva youd need .7-.9 cf. you could do all 4 shiva in a single 1.8 cf box.

and it would sound as loud as 2 shiva.

ported you could do a pair in 2-2.5 cf, all 4 in 4 - 5 cf. as of now if i remember correctly youve got about 5.6 cf in there, but youre looking to reduce space. If you wanna say screw space and just care about output, you can cut out the middle wall of your boxes, and port a clamshell set in each one of your two boxes.

 
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just to add, i myself have a clamshell ported design in mind. 6 or 7 cubic feet.

 
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Thanks for the info Ludlam, I have been trying to "map" something out on WinISD all day, and I am getting pretty annoyed figuring it out.

Basically I want to either go with 2 clamshells either sealed or ported in 1.4 cubes each (since that is the size of one of the boxes I have).

1.4 cubes is half of 2.8, so that should be ok sealed I assume?

1.4 cubes for a clam might even be enough for a clam...but I can't figure it out on WinISD without have a 20+ inch port ( I was hoping for something about 12" or less )

what tool do people use to cut ports? Would a dremel work?

 
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ported would require both your boxes do get a decent sound out of it. you could do it with one of your existing boxes if you cram about .4 - .5 or so cubic feet worth of wood in each 1.4 cf chamber. doing it just like it is in the box sealed would make it act like if you had each shiva in 2.8 cf sealed. the funny part is that now your box is too big. who woulda thought a box too big for shiva.

 
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The whole box size thing is kinda funny.

Anywayz, why do you say that I would need to cram extra wood into the boxes in order to port them? I thought maybe I was on the smaller size for one clam in a 1.4 cube box then so big that I have to add wood.

IYO, would 2.8 feet be enough for a normal ported shiva (not ideal, but enough?)?

 
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no, i meant youd need to cram more in to have them sealed. ported that probably wouldnt sound too good at all. not only that, but to tune it to the optimum 23-24 Hz, it'd be a retardedly long port

 
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i also forgot that youd have to factor in port size when designing enclosure size, so the 1.4 cf would be used not only for enclosure size, but as area that the port uses

 
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...which has been exactly my problem so far with trying to figure oue port size.

From what I read online so far, a clamshell configuration is not exactly the equivelent of making the box act twice as large. I dunno, it is VERY confusing... I should just go ahead and set it up and hear for myself

 
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I could swing a 12- 13 inch port per clam if I tune it to 30 hrtz according to WinISD...but I was hoping to get closer to 20hrtz, and just throw on some of the Harrison Labs "subsonic" filters.

 
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factor in port volume, that adds up to almost another .1 cubic foot, minus the .12 cubic foot displacement, youre down do a 1.2 cf per chamber box.

 
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...ok I have a huge headache trying to figure it out...I thought it would be something cool to do, but it seems like more trouble then it is worth

 
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Ok, I found a local lumber yard that will cut the MDF for me. So I placed my order and I have to pick it up later today. I just have to cut the holes out, so I bought a jigsaw I am shooting for a 4.77 cubic foot ported box.

I have bought all of the other materials that I need, but I have one Really important question: I bought 3' PVC for the ports, but how do I get the PVC to hold to the outside of the box when I slide it in? Is there a recommended plug or something to use? Any suggestions?

Thanks

 
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When I build a ported enclosure I install the port before putting the box together. Just make sure the hole you cut is really snug on the pvc and then when you slide it in either silicone or epoxy it from the back side so its not visible.

 
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here is how isobaric enclosures work:

in a nutshell, you have twice the motor pulling on the same amount of air. thus, the apparent airspace to each woofer is double that, as higher pressure meets more motor control and power.

thus, a PAIR of shiva on 600 watts RMS in a 1.4 cubic foot box will perform IDENTICALLY to a SINGLE shiva with 300 rms in a 2.8 cubic foot box.

identicla in every possible way.

which will be sloppy as heck

lud is teh ported shiva guy, not me, but id highly reccommend not using the boxes you got now if you want to run sealed.

like lud said before, the most ideal allignment with 4 isobaric shiva would be 1.8 cubes sealed. and how will it perform coupled with a jbl 1200.1?

it will sound exactly the same as TWO shiva with 600 rms in 3.6 cubes sealed.

so basically you will get all teh sound of 2/3 the size of yrou current setup, at like a third of teh size. definitely a downgrade in volume! (but if you ask me, a huge increase in quality!)

really, the ONLY way to go to save trunkspace while saving or increasing yrou volume and also increasing quality would be to go into the spare tire well.

it requires no fiberglass, just a jigsaw and some creativity, and you could definitely leech out at least half the 5 cubes youd need to port 4 isobaric shiva.

if your interested in it, lemme know, i cna go into construction details, just kinda busy now and the next couple days to be my usual painfully specific self, and i dunno how crazy you are about keeping yrou spare tire and/or moving it to below your car.

 
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4.77 is gonna be fun to build. most likely youll have to build it in the trunk. what are you gonna tune it to?

 
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about 21.77 Hrtz I think...I have to check WinISD again...but I will post how it turns out when I am done...I have had some problems so far, but hopefully I can correct all of them. However, I am not ready for all the tricky ish like bracing...so bare bones stuff for now

 
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pfft, i got 4.5 cubes ported (6 cubes gross) into my trunk with a 3" lift no problem, i dont see why you couldnt do it too.

and i STILL gotta reccommend using yrou spare tire well in a glassless box

 
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Part of the reason I was doing my "project" was to be able to access the spare tire, but it looks like with the outside subs inverted it will end up taking up the same amount of space

...project going ok as of now, but will take a few weeks with M--day and some other stuff going on this week....damn, but I am anxious to hear it. It is 23 by 15 by 31 1/2.



edit: If the box ends up not fitting (but it should), I will have an awesome HT subwoofer set-up to replace my factory Denon HT in a box subwoofer ( I don't really like my upstairs neighbor BTW)

 
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I have to re-ask these questions because I am worried that I am going to completely finish the box and then this may present a problem. Any input will help

 
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i cant say for sure about the surrounds hitting. everything else, you are golden.

arethe foamy black rings in good condiyion? if so, they will sea lup perfect.

might need a spacer tho, thats a good one! test ans see

 
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Yeah, all of the black foamy rings on the Shiva are in good condition. I wish I was skilled enough with a jigsaw to make MDF rings, but I had a hard enough time cutting out the speaker and port holes

I need to pull a pair of my speakers out and test it...I looked at it this morning, and there is a lil bit of space but I got to check if it is enough to keep from rubbing.

thanks

 
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Ok, I finally finished my project and it sounds pretty darn good to me

Here are the pics

thanks to you all for help and advice with isobaric and carpeting

 
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im impressed! must sound SUPER transparrent! id be happy too....

now you gotta drive up and let me hear it

 
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haha, yeah if I ever go that far up north I will be sure to pass through SLO

I think the bass sounds great and I think the new configuration has made a world of a difference. In the past when I had tested box placement and how it affects how my bass sounds I found that a few inches from the back of the trunk was the best (I got the idea from Eddie Runner's sub placement article). Also, I had read that facing the ports in the same direction as the subs is ideal, but I had never tried this before ( I have had boxes with ports on top and ports facing out of the back). When I tested it out I set off my neighbors alarm in the apartment building next door, which I had never done before...so far so good.

I also deadened both of my doors completely with one layer(because I just had the lil Dynamat speaker kits on before and I had half a roll of fatmat in my closet. I wanted to improve my midbass/midrange because I can't really afford new speakers right now because I want to get a new changer)But if it is not one thing it is another because when I was driving to work today I was playing Hail Mary by Tupac (I found the CD in one of my crates and I had only listen to it a few times because I am not the biggest Tupac fan )...anywayz, there is this little high pitched sinthesized horn part that is in the middle of the song and I noticed that it was mainly coming from the right side speakers...and it came out very low on the left side speakers. If anyone knows, is this how that horn was recorded (mainly on the right hand side) or maybe I misadjusted something? I don't know why I am even asking...I should check on my home stereo when I get home. If this isn't the case i need to do some speaker adjustment and then I will be good to go sorry, about the random bumbling, I just want tofigure out why it is doing it.

 
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Great job on the box. From what I can see the carpet came out great and from what I can't see who cares because you can't see it

Now you said the ports were pvc which I assume you either got the thin PVC which is black on the inside or the schudule 40 and just painted the inside black, but what did you use on the fron of the box to make them look flush(the white ring)?

 
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haha, you noticed that...good job! I had to do some tricky ish...I used something like this (if the link doesn't work it is the first link at the top of PVC products and the first item on the top). It is some Thick plastic that holds pvc pretty air tight. I cut off the most of the top thick part so that it would look flush, and then I sanded it down (I oversanded one part just a lil to much which is hard to see because it is white). My girl said I should spray paint them black because it would look better, but I can always do that later. Anyways, it fit loosly in the holes that I cut out before I put in the carpet, but after I put in the carpet they fit snug. I had also sanded around the wood holes at a slight angle because as you can see the cups that i used are angled. I wrapped some 3m double sided foam tape around the top and jammed those suckers in with my hands and a rubber hammer Fits tight as a glove.

BTW, if anyone cares...that Tupac song is recorded like that so it wasn't my radio...I was thinking about what it could be all day at work. I had to listen with head phones on my home stereo to figure it out.