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billy98sport
09-04-2003, 12:20 PM
ive built plenty of boxes b4 but i usually had a plan, i dont know how to tune ports, the RE site says for a .5 cubicft tuned to 32hz.... the dont give any instruction so i dont know how to go about making the measurements right or getting the right size port so that it will be tuned at 32 hz...... is there a site that explains that stuff or can sumone hook me up with sum plans??

thanx
billy

Primetime
09-06-2003, 02:49 AM
External Dimensions ...

Height = 10"
Width = 18.75"
Depth = 12"
Thickness = 0.75" MDF
Gross Volume = 0.891 ft^3

Approximate Driver Displacement = 0.05 ft^3

Port Height = 8.5"
Port Width = 1"
Port Area = 8.5 square inches
Port Length = 42"
Port Displacement = 0.34 ft^3
(Three 3/4" MDF boards, 8.5" tall, 9.5" long ... One 3/4 MDF board, 8.5" tall, 7.5" long)

Net Internal Volume = 0.501 ft^3

Fb = Sqrt(23562.5*8.356^2/0.501/28.319/(0.614*8.356+2.54*42)
Fb = 32.204 Hz


should it be tuned a little bit higher for pure SPL?

Dave

Woodmister
09-06-2003, 04:49 PM
Hey Jmac do you know if this caculator works correctly? http://www.linearteam.dk/default.aspx?pageid=ventcalculator

Also, do I want to keep it below .16 vent mach like it says? The ones Im comming up with are around .80

Woodmister
09-06-2003, 05:41 PM
Cool, guess I'll have to keep working on it...

billy98sport
09-08-2003, 02:21 PM
jmac, where can i find a decent port calculator, your plans seem good, one problem, the speaker's displacement is .9 ft^3, but it that wont make much of a difference or, tune it a little high, like 33 or 34hz then thats good enough

thanx for the help

billy98sport
09-08-2003, 02:47 PM
correction: displacement = .09ft^3 sorry

Matador
09-08-2003, 04:56 PM
hey jmac, what program do u use to find the port sizes?

i would like to learn to use some program to design ports as i will be making couple of ported boxes in the next couple of months

billy98sport
09-09-2003, 09:59 PM
jmac, if i reduced the depth of the box to 10" instead of 12, how would that effect the tuning, would it make it higher or lower? if it makes it higher that would be better, i am using this sub for a midbass,(mainly sq) application

billy98sport
09-12-2003, 12:06 PM
dont worry about it, i got your formula from another thread u posted on, i figured it out. im playin around with it right now, i got it be H=10 W=14 D=14 (im trying to make it fit on my other box), with a 39"port, tuned to 37.1hz, with a net volume of i think.469, im trying to add a little sq to the 8, so i lowered a few things. only, with a width of 14. im going to have EXACTLY enough width for the sub cutout, and i dont like playing around with exactness when cutting the hole, so fixing the width to give me at least an inch and quarte like the hight, then probably ill have to increase the port length keep it tuned around 37-40hz..... i never knew how much time went into these formulas, i have a newfound respect for people that figued all this out :)

thanks again though
billy

billy98sport
09-12-2003, 12:44 PM
one thing though, im confused on how u got the vd in the plans you give me, im putting in the info you have into the formula that you posted and its not coming out right

billy98sport
09-13-2003, 01:32 PM
i got you, so the vd is different for each different style of port you have? because the reason i was getting confused was because of your post on another thread in which u said

"If using wall as one side of the port ...

(Hv+T)*(Wv)*(Lv-T)/1728 = Vd

If using no walls for sides of ports ...

(Hv+2T)*(Wv)*(Lv-T)/1728 = Vd"

billy98sport
09-13-2003, 06:03 PM
scroll down on this thread, at the very bottom they the simialr thread things "ported box formula" is the one u posted on, im not sure if u said directly that that was for straight ports only, that info helps though, i need to change a few measurements and things now though :(

billy98sport
09-13-2003, 08:29 PM
so, for a port like on my box, "curved", the formula (using variables) is.....

billy98sport
09-14-2003, 12:57 AM
thats straight dude, not everyone can be car audio nerds and keep a decent relationship going...

billy98sport
09-15-2003, 08:04 PM
thats cool, hey, any particualrs on a box for 2 subs that share a port, like, ive seen boxes with a 2 subs and one port in the between them, its really tight lookin, is there any thing i need to add to the formulas to figure that, or just make the part of the port that they share twice as big? also a friend of mine wants a box for 4 15s, would it suffice to have 4 different ports or 2 or just one, how does that figure in?

billy98sport
09-17-2003, 11:46 PM
hey man, whats a good way to determine how much to port a speaker, like 30...35...40 hz, and... doesnt the net volume also play a factor in what kind of sound u get, like, if had the same port tuning of two different boxes but 2 different net volumes.... meaning u would have to increase or decrease port length acordingly but... ok lets say of example... a .5cuft ported at 40hz and a.75 cuft ported at 40hz..... same drivers.. same amps.... the only difference is net volume.... what would the difference in the sound b?

Pl8er
10-08-2003, 05:23 PM
Ok now I need help and it seems Jmac is the man on this topic so I thought I would just reply here.


I have (2) re8's and I want to build a box this evening. I want it to be a single box. I'm very new to building boxes but it seems with the measurements you have been giving I could do it. How would I go about something like this with 2 of them sharing a port? I see how you did it in the post above me but are they going to share the port distance? Or would you put double the port length inside (half for each sub)
Thanks alot for any help!

Justin

Woodmister
10-08-2003, 06:55 PM
Hey Jmac, I was wondering if you could check somthing for me since you probally have all the RE8 stuff on WINISD. I have two new RE8's (with the 12mm of XMAX). And I just wanted to make sure everything was ok. The box is going to include the following...

Box Volume: .50cuft
Port Hz: 30Hz

1 Vent (per sub)
1" port diameter
4.018 long
Vent Mach: .11

Im going to be using this port:
http://www.partsexpress.com/pe/showdetl.cfm?&User_ID=13719888&St=5163&St2=80119534&St3=-43420988&DS_ID=3&Product_ID=5689&DID=7

Pl8er
10-09-2003, 04:38 PM
Jmac thanks for the info. I built the single sub box last night! It worked out much easier then I expected. Thanks for all the info!


Justin