ported clamshell help/build

[Neo_frog]

Ok... So you're saying you're playing low, but not moving much air..

I'm looking at the design and I like your projected numbers, but not the layout of the box. The thin volume in the clam (between the baffles) and low area in the terminus will yield most of your low tuning goals, but those port walls you added are causing serious restriction and turbulence in the port "area". In my build, the volume of the port matters, but it was experimental, not ideal. Had I opened my port up like yours, I would have been louder, but not as tight. I was attempting to get a grasp on independent resonance. Basically, air compliance in the given "system" (i.e. the enclosure) independent of its environment (i.e. vehicle). It was basically designed to have low end control and little change in response when compliance factors are changed (like doors/windows open/closed, seats removed, etc..). It was successful for the most part. Still need to mess with design a bit. =]

Don't chop anything out just yet. My suggestion is to cut out your port walls inside the box, brace the baffles more, and add a loading wall in front of the clam. Aesthetically, it will be detrimental, but it will help you control your response. While your port walls look symmetrical, the loading environment at the port is not since there is a large common volume with the activated air which is most likely being consumed by turbulence. That would describe your lack of air movement, but low tuning.

So cut out the ports, brace the baffles, and add a loading wall. That's my next step not having exact numbers from you. If you can give me EXACT specs, I can give you a better idea of what's wrong. I didn't have much time to be on or play with numbers, so I'll end it with this. Let me know if you need help or a better explanation.

[Neo_frog]

I also wonder if your ratio of baffle depth to width is a problem...do you have any numbers for me? I'm working with pictures here lol

[irpirate]

i think the independent environment part was successful, dont notice any difference when windows or doors are open besides i can hear rattling and flexing louder lol.

so basically the port extensions i added is bottlenecking the air movement/creating turbulence to the point nothing gets out.

ill try and just type the numbers out. the front opening of the clam is 14 tall x 36 wide. the back is 6 tall x 7 wide. from there it extends about 4 inches deep and then around 5.25 inches up/down. distance from the vertical port extensions to the back wall and from the end of that port to the top and bottom of the box are both 6 inches as well. the angled board holding the subs are around 40.5 inches long.

so are you suggesting i take out only the back vertical port extension, or the back vertical and the horizontal port connecting to the board with the subs? its going to be a major pain in the ass taking out lol. the thing goes in pretty deep and gets pretty damn narrow at the end (6 inches T_T) but ill do my best to get it out. as for the loading wall. how much should i make it go over the edge of the board with the subs? ill email you the google sketchup thing. if you dont use sketchup ill try and figure out how to get the specs listed on the design so i can post a picture.

[irpirate]

emailed you the google sketchup file

*edit - the sketchup is a bit messy some numbers are off a bit, should be 6 inches from port the wall for all sections of the port(s)

heres the sketchup for anyone else who wants to take a look at it

http://www.megaupload.com/?d=XM30IMWF

[Neo_frog]

Yeah, you're longer than you are wide (lol). I'm not much of a fan of that type of baffle setup and I haven't seen much of it.

As far as independence, nobody expected you to design it for that, so don't worry too much about it. Mine was a test based on some trends from a few very knowledgeable members on here and some other sites. Play with resonance when you learn a bit more, but don't make the claim to fame just yet. I'm not trying to be an ass, but try to avoid saying that you got a "concept" down until you actually do, ya know? Just tryin to help man. =]

Pull the back subs out. I would rather suffer through the mounting process again than damage the box. Cut out the port walls, or bust them out. They look like they were only glued in the inside?

As far as the loading wall, I don't have exact angles or specs, so I can't give you numbers. Cut up a few sheets of MDF and try some different lengths on top AND bottom. You either need to make them symmetrical on top and bottom, or you could try a passenger side loading wall. That might cause impedance issues down the road with some of your subs though. Either way, give them a shot. You aren't beating up those subs, so you should be good.

[irpirate]

oh god, i in no way meant to imply that i did that on purpose or that i'm knowledgable in anything car audio, it just happened to turn out like that lol. i can say confidently this stuff still confuses the hell out of me and will most likely continue to do so for a longgggg timeee xD

ill try and get port walls out tomorrow, working at my friends garage and this thing is way too heavy for me to move myself. just for clarification do i take out just the vertical or both the vertical and horizontal (which would leave only the board with the subs)? ill start by taking whichever port things out, see how that does, then do a loading wall, then tweak (assuming i have enough time for all that). ports are glued on the edges and screwed in.

as for tuning i have no idea what it is. no termlab and haven't had time to drive down to des moines and get it checked.

[irpirate]

one question id like to ask. in case the box still sucks after the tweaking and i end up doing a new box, would i be better of doing another clamshell (this time with some thought put into it rather than hope and prayers) or a 4th order? someone mentioned earlier i should do a 4th order which, to me, seems like it would take some of the guesswork out of the design. if people say 4th order i'll start reading and trying to understand the calculations for it (probably fail at it )

[Colin - STAPUFT]

A thought- totally apart from Neo_frog's Ideas and mine aren't based in anything- so take them for what they are lol:

I get the whole "loading wall" part, but why not try to seal off the sides of the box to the vehicle (help eliminate cancellations to the rear of the car), make the "loading wall" and inside of the loading wall, make a port that goes INTO the horn portion of the clam. That will take up space in the mouth, provide loading to the subs, and give you another means to tune the box (a-la 4th order of sorts).

I am still confused about your "port" pieces. Are they in the back? Like constricting the flow you think?

[irpirate]

i havent sealed it to the vehicle yet because i wanted to make sure the box performed like i wanted it to before i did anything semi-permanent. i brought up putting a piece of wood in between the subs earlier if thats what you mean by making a port that goes into the the horn.

*edit - shit the thing screwed up my spacing ill upload a pic

purple is port pieces

[irpirate]

the more i read about 4th orders the more tempted i am to try it...lol. i guess i'm a lot like you neo, pullin out stuff switching around the second its done if it doesn't live up to expectations.