Need some help

[NickCR 10+ year member]

I got these box plans designed by a member on here and i've been trying to contact him but he seems to be away or something. Eitherway here is my questions:

The width of the box is to large, i need to cut it back to 37". The loss of space can be added to the height or the depth.

If I remove 3" from the side, which side should I take it from the air space or the port and second where do I add that space and how much do I add?

If I flipped the box around so the port was on the right but close to the face and mounted the subs on the opposite face so that the port would exit near the same face as the subs would that change anything?

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[Trixter 10+ year member]

I got these box plans designed by a member on here and i've been trying to contact him but he seems to be away or something. Eitherway here is my questions:
The width of the box is to large, i need to cut it back to 37". The loss of space can be added to the height or the depth.

If I remove 3" from the side, which side should I take it from the air space or the port and second where do I add that space and how much do I add?

what ever volume you take away, just add it to another side. 3" would be about .5cu'. so play with the numbers and add .5cu' somewhere else.

If I flipped the box around so the port was on the right but close to the face and mounted the subs on the opposite face so that the port would exit near the same face as the subs would that change anything?

no, it will sound the same.

 

[James Bang 5,000+ posts]

what's the specs of that box? tuning? cubic feet?

 

[hofulstrof 10+ year member]

a simple L shaped port would work alot better for your sitation. there is alot less room for error in the build....

 

[NickCR 10+ year member]

The actual exact specs of the box i'm not too familiar with because i'm really stupid when it comes to the calulation of this stuff.

The port was designed like that because it produced the best response for my sub, don't ask me why but anyway the guy who built it on here has made lots of boxes and seems to have a pretty good idea what he's doing.

Great to know that fliping the port around won't affect the performance.

Just need to know more about the spec changes. Obiously changing the height or depth of the box, that will change the specs of the port space and obiously may change the response of the sub. So I guess I was hoping someone could give me a an idiot proof response on this

 

[hofulstrof 10+ year member]

im sure he is a great guy. and i think bending the port like that saves a bit of space.....but less bends the the port makes the air flow through smoother...

but basicly the box needs to be totally redesigned..there is no simple way to fix it

 

[NickCR 10+ year member]

You know your image just gave me a thought tell me what you think.

If I was to increase the height and then add in those corner pieces in the port (for smoother flow) wouldn't that decrease my port volume compensating for the height volume that i've gained?

Or am I just a dumb noob... that has no idea what he is talking about and completely needs to be re-done.

I did have my installer look at the plans when we did the final check to see if it would work and he said he had seen that design in home stereo speakers and they sounded really good.

I am an idiot that doesn't know anything but anyway maybe the guy who made it will drop in and explain why he did it that way. Either way comments welcome.

 

[hofulstrof 10+ year member]

we were all noobs at one time in our lives....

increasing the box hight ( while keeping the port width and tuneing the same) will increase port area making a longer port

the reason i pu the 45 degree angles in was to make the air flow smoother through the port. that way i can get away with a bit less port area. and not have port noise. or i can use more power and not have noise..

the onlything we need to know port volume for it to find out how much volume it it displaceing in the box...

im not saying that design wont work. infact it will probly work great. im just saying i would have done it a bit differently

 

[NickCR 10+ year member]

Yup exactly what I mean by the 45 degree angles, it would reduce the port volume which is what I would want to do if I was "increasing" it. IT would sorta counter each other.

I'll try to find out that info and get back to you .

 

[hofulstrof 10+ year member]

i think your getting the words volume are area mixed up here.

 

[Trixter 10+ year member]

yes, he is.

the tuning is base solely on the port's length/area ratio. the area, opening size (W x H), determines the air flow; too little will result in port noise and too much could result in bottoming out your subs. determining the port area and pluging it into the formula, along with the box size (minus all displacements) and desired freq., equals the port length.

the volume does not matter...only when figuring out how much space it takes up inside the box, or it's displacement. when figuring this, you need to count the wood that makes up the port walls as well. as i said above, you need to know the box size after all displacement for the formula. how is this done with out know the port length? you do the formula twice. once to get an estimated length and another to get a more exact length. you can go crazy doing the formula back and forth, but only twice is necessary.

if you were to make the box smaller on one side and compensate by making it larger on another side, it would throw off the the lengths (or heigths) of all the port walls that are listed in the pic. if you post the tuning, volume (can figure that out by looking at the pic i guess) and port area, myself or someone else can re-design the box for you. also post the over all external dimensions you want.

 

[NickCR 10+ year member]

The orignal designer just got back to me and will have things re-designed for me so when he's done i'll throw it all together and let you all know how it sounds!

 

[hofulstrof 10+ year member]

good stuff