Chops first official box design?

[slim2fattycake 85]

wow.. lol

[iputon326 9]

will be making a attempt to grab the mdf tomorrow,

if I do then the box should be able to get under way shortly there after.

we wana see pics chop.

i wana see what this port looks like.

[porkchop 304]

this just took a big ol" shit, i will explain later...

two to three weeks out now...

INDIANA = FTL

[shizzzon 461]

so r u commin or not?

[porkchop 304]

i will confirm our intentions by tomorrow afternoon.

if we do come, it will be without my truck and as spectaters only.

my account was up for an extension, instead they chose to open a new claim, resulting in a waiting period, wich does not pay, so without any warning, we loose this weeks pay.

i thought it was going to be tight but really wanted to attend badly, so we was going to just make it all work, but now, we have no money coming in at all for this week.

we sat there for over three hours today, with nothing to gain. they goofed up and we paid for it.

sorry about the ranting , it just super sucks....

if mikey can cop for most of the gas and we nix the whole hotel thing, just do it all in one day.....

pack some drinks, snacks, & sammiches.....

we could still pull it off.... the box will have to be put on hold as well as all aspects of the truck for a couple of weeks while i play catch-up.....

just being able to be there in your corner and getting the hell away from Indy is enough motivation for me....

it is really going to fall on mikey and rattlebox if we are going to pull this off, i am screwed...

i will have to just pay for Carl Casper.

i will have it all put together by tomorrow....

been out all night trying to create opportunities...

chop

[rattlebox317 1]

Chop we need to get this done. we need to get on that asap

THANKS IAK

[porkchop 304]

no road trip, sorry.

too many obstacles to overcome for us as a group.

will instead begin box build and finish electrical.

sorry shizzzon, we will be down in feb. at Carl Casper.

good luck and look forward to seeing the results...

chop

IAK

[rattlebox317 1]

yea kind of sux .............. wanted to go to but u know how sh*T goes down ......... never the way we want it to ...................

[porkchop 304]

so, I finally got my crap together enough to take a closer look at begining this box.

I have a couple of questions perhaps to help better my understanding of the concepts applied.

first off, port area.....12" to 16" sq inches of port area is suggested per cubic foot.......i went with 62 sqaure inches (4" X 15.5" = 62" ) ........puts me at 15.5" X 4 cuft.

I am powering the sub at rms. I want it to be loud, but not just farts, daily music loud.

I was under the impression that I should go with a larger port area....to get louder....is this correct?

I am asking because when shizzzon redesigned the port, he also changed port area......smaller.

second problem I am coming across is port length......I cannot find a consistent formula to design the port length.....it is cool to find answers on your own....you know?!

so, I have read that there is no two port length calculators the same..... okay....well I am confused about what the hell one is right?

I mean I floated a design around in a few places and found no consistency, I mean a couple of inches differance in either direction.....?

I don't want to question any ones methods....I just want to find a method that is consistent.... consistently correct perhaps even.

It is very important to me that I learn this and learn it correctly. If I need to back all the way up yo learn it correctly, then thats fine.

any input our links to info would be great..... I am planning on rereading the info I have located so far... attempting to apply it to these designs, hoping to find a consistent bases in wich I can count on and apply to build designs.

again.... any and all info would be great, input is fine....draw it out, step by step, help get ol' chop right....100%.

thanks alot for the help,

chop

[porkchop 304]

[porkchop 304]

[bigrank916 72]

The last two boxes Ive built, I have been using this calc. Its probably not exact either! lol. It does the tuning for you while you change the specs. I t takes a little a number flopping to get exactly what you want though. It might help to fool around with.

http://www.reaudio.com/speaker_box/LPort_Box_Calc.html

[shizzzon 461]

the reason i slightly lowered port area is to achieve a shorter port length.

It's still within recommendations so no issues.

When i design boxes, i don't want the port entrance to be close to the sub obviously so without seeing such pics while designing, that is why you may question the reason why i did it.

Also, when designing a port that shares parts of the box's walls, that's a slot port.

In a slot port, let's say the box is 10" tall internally.

You get a port that is 10" tall and 4" wide and 20" deep. The depth 20" is your physical length, but you also have acoustical length as well.

So, in a slot port, you take half of the width which is 2" here and subtract it from the required physical length.

So.. let's say this port was attached to a single 3\4" mdf wall that needed to be 20" long..

The port wall depth itself would only need to be 17.25" deep, then add 2" for acoustical length - 19.25" then add 0.75" for wall thickness - 20"

The reason why generic calculators may be off is because you also must know what type of surface the port begins and ends on\with.

If the port is flared on one end, both ends, or just flush with the outer box, or not flush at all on either end... these all effect port length.

[bigrank916 72]

Try putting 5 in the square port width and 12 in the square port length 2. You get about 35hz even. Hope it helps.

[porkchop 304]

okay......... i think i understand some of what yo are saying, i will re-check my math....mainly because i think i aleady did this....

am i confused still or is there a typo or mistake in these two sentences..........

sentence # 1

" So, in a slot port, you take half of the width which is 2" here and subtract it from the required physical length." ......... so this is saying "SUBTRACT"....

sentence # 2

"The port wall depth itself would only need to be 17.25" deep, then add 2" for acoustical length - 19.25" then add 0.75" for wall thickness - 20" " ........... and this says " ADD " .............

what is going on here? if both calculations stand true...subtract 2" and then add 2" , ... i end up the same place.....0 - 2 = -2 + 2 = 0 !!!

i use these........

http://mobile.jlaudio.com/support_pages.php?page_id=165

http://i162.photobucket.com/albums/t246/Kickerlivenloud/PortLengthsolved--Thisoneisright.jpg

thanks for the help so far... get me the rest of the way now, lol

chop

[porkchop 304]

somewhere in that post i was to ask if these are good ones to use....

[porkchop 304]

also was wondering why we do not have this info in our "how to" section or a link to it at least.....

i mean like a pinned post that can be referanced easily enough?

chop

[shizzzon 461]

ok, let's see if i can rephrase this.

Port length calculators give you physical length.

What the sub reacts to is the acoustical length. You sometimes may accidentally install a design in a car too close to the port exit and may extend the acoustical length causing the port to be tuned lower according to how the port reacts to the surroundings...

So... in that previous example- port calculator wants a port to be 20" long. Well, passing over a single sheet of wood of 3\4" thick, the port wall you glue on is actually 19.25" long....

Ok, so now u know the port wall would typically need to be 19.25" long.. glued to back of wall = 20"

Well, since now u know where i get the 19.25" from, now u will understand this next part-

Port calculators.. unless specifically designed to accept slot port info properly will know when u are using a slot port.... sometimes you must modify the port length answer yourself depending on the port...

In this case, you would be using a slot port so you would need to subtract 2" from the physical length requirement... and ADD it to the acoustical length...

You might not know the actual acoustical length of a port unless you do some math but u will know that when using a slot port that half it's width is added acoustical length!

So when using such port, you must subtract the length the acoustical length will add from the physical length calculated so the port calculator's answer remains accurate.

I think i worded that right, hehe.

So.. again, 4" wide slot port.. half it's width is 2" Port calls for 20" long... 19.25" port wall attached to back wall internally...

If it wasn't a slot, the port wall would be 19.25" long.

However, if we keep it 19.25" long using slot port, the sub will react to it being 21.25" long due to the 2" of additional acoustical length added from the use of a 4" wide slot port...

Reduce 2" from physical length- 17.25" which will make the sub see the port as being 19.25" physical and the rest acoustically will still fall into play.

[porkchop 304]

i will take my numbers and run them through the formulas again..... keeping in mind what you have said.

i am determined to walk away from this with a complete understanding of what to do and how it's done....

did you take a look at the two i have....port length calculation formulas........

do they appear to be correct?

thanks chop

[porkchop 304]

http://i162.photobuc...soneisright.jpg

i used this one and came up with 29.58" using that math.......that seems alot longer than what you had suggested @ 25.5"

this is with a additional 2" added to the answer, if i were to subtract the 2", then i would of been at 25.58" ...........

so am i really that close to getting it right, subtract instead of add the 2" with this formula ?????

chop

[slim2fattycake 85]

Use the formula and then subtract 2.

You would get a shorter REAL length but ACOUSTICALLY, your sub will see a longer port. In this case longer by 2.

[porkchop 304]

right on.... trying to get Alex to sleep, then i am going to tackle the next one

[porkchop 304]

http://i162.photobuc...soneisright.jpg

sooooooooo, we like this one with the amendment of ;

dividing the H in half and subtracting that from the port length, as opposed to adding ......??????

thanks chop

[rattlebox317 1]

chop i think your math is right ............. lets go with it !!!!!!!!!!!!!!!!

[porkchop 304]

here is the box u want to build-

You sure u want to do that?

I dont like boxes where the sub fires directly toward the port exit...

That's one main reason why long, single shot ran ports are hard to cope with the box due to this.

The port in the pick is 24.75" long internally displaced, 25.5" long total.

Remaining space- 0.13cubes to equal your 4cubes NET. So, you got plenty of room left for bracing and 45s in the corners.

going with this on first build ........ will attempt to experiment with different style enclosure perhaps Janurary

starting build tomorrow... it will be under the build log section!!!

thanks,

chop