:) Check my first Bass Reflex 6 ports, 2 driver standard configuration design :)

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Well here i have my first design, could you check it? And tell me if i'm completely wrong? nearly nearly? or good enough to do a test-speaker? :)

I got one drivers T/S parameters (i know that when i buy the driver Fane Colossus 18XB, i'll calculate T/S parameters instead using the spec from manufacturer :) ) Cause i want to drivers 2*Vab and 2*Sd right? I'm not sure how to predict, or mesure how Fs will change once they are together (electrically in paralel) any ideas please??

Now i can calculate the Vab,Fb,Fl,Lv, Sv, etc.. for a C4 Alignment for a QL = 3, that gives me a volume Vb(L) =442,14539 . Wich i can verify that my suposition of QL was correct because Vb>80L (atleast this is how my book says to verify your QL)
Important parameter is Lv=0,10997 or 0,112368 or 0,0755 (with constant=23500 proposed by Small) ..... I think i'll get try the first one and start trimming while tunning :) as they've told me at this forum :)

Then i divide the Sv by 6 (Sv/6=Sv') because i want to make 6 cilindrical ports. That gives me Sv' and Dv'=0,103m I'll keep the Lv the same right? Or i divide it by 6 too? :S

Well, with a volume of Vb(L)= 442,1453 L and using the golden ratios of 0,62x1x1,62 i get a box dimensions of W=1,23m , H=0,47 and D=0,76 , wich are really bad dimensions, because my driver has a diameter of 0,48m and i kind of draw it in paper and the 2 drivers with the 6 ports don't really fit in 1,23 of width. :) So i changed a bit the dimensions, keeping the same volume W=1,29m , H=0,54 and D=0,63 .

I think its really really big, and before i start building it, and spent money with the woods, i would like to know some opinions, because this is my first design/construcion of a speaker. And maybe i'm just going completely wrong :)
here i leave a table i copied from my excel calculations:

T/S param
1 driver Colossus 18XB
2 drivers Colossus 18XB
Fs
33 Hz
33 Hz
Qts
0,337
0,337
Vas
236
472
Xmax
7,5e-3
7,5e-3
a(m)
0,2056605
0,26833131
d (2a ) (m)
0,41151
0,53666266
Sd (m^2)
0,1131
0,2262


C4 alignment
α
1,2616
h
1,1034
q
1,2798
Vab (L)
374,128091
Fb (Hz)
36,4122
Fl (Hz)
42,2334
Vs (L)
34,00864933
Vb (L)
442,14539
Vdmax (m^3)
1,70E-03
dv (m)
0,194066525è0,25
Sv(m^2)
((0,25/2)^2)*Pi=0,05
Lv (op1)
0,10997276
Lv (op 2)
0,11233682
















Design with 6 ports

Sv’ (6ports)=Sv/6èDv’ (m)
0,103m


Dimensions

W
1,29m
H
0,54m
D
0,63m


Pd: any advice for construction? wich cheap wood is good enough for my test-speaker and won't influence that is cheap on the results?? Wich material should i use for the ports?? Rigid PVC right? any thickness better than other?

And another dumbie question i just though, to trim the ports while tunning to the Fb, do i glue them all time and test? Or how do i stick them, test, and cut ?? Any good method??

Sorry for this long long post and if there are too many questions, and if there are not really smart :) I'm new, and my english either makes me look dumber :)

Thanks to all and for all. Really apreaciate your help and this cool forum :)
You are all invited to our parties if the speakers project succeed :) :)

pd: don't be cruel with me :) jaja i'm a newbie
cheerz from Spain
 
First thing's first - I strongly suggest that you don't use 6 separate vents. You're going to REALLY regret doing that once it's time to trim those vents to achieve the target Fb :). Instead, I suggest going with a simple shelf vent below the driver - it will be much easier to adjust the length of the "shelf" by designing it to be a simple screw down panel that you can remove and trim if necessary.

Second thing - don't put the two drivers in one chamber. Use separate chambers, one for each driver.

Your end result, if you follow my suggestions, will be two chambers, two shelf vents, and a pretty sturdy box (the shelf vents will act as additional bracing to the panels).

Thirdly, don't worry about the "golden dimensions" when it comes to subwoofers. They will make little difference to the subwoofer's performance. For 18" driver, you may want to consider making the baffle 2ft x (2ft + shelf vent height), then derive the cabinet depth from the net required volume - this approach may result in a cabinet that's deep enough to hold the shelf vent without having to resort to folding it.
 
+1 Brian

If you put the two drivers in one box they will interfere with each other since no two drivers are exactly the same.

I just modeled that driver in a 221L box with Fb 36.4hz and one .304m (12") diameter port, .522m (20.55") length.

it's a monster :eek:
 
First thing's first - I strongly suggest that you don't use 6 separate vents. You're going to REALLY regret doing that once it's time to trim those vents to achieve the target Fb :). Instead, I suggest going with a simple shelf vent below the driver - it will be much easier to adjust the length of the "shelf" by designing it to be a simple screw down panel that you can remove and trim if necessary.
you convinced me certainly :)
When you mean a shelf, its a kind of rectangular port under the driver? Or do you have any link to a picture so i can figure what it is? my english is not too god :S
because i google speakers shelf vent, and they only picture me wood furniture :)

Second thing - don't put the two drivers in one chamber. Use separate chambers, one for each driver.

Your end result, if you follow my suggestions, will be two chambers, two shelf vents, and a pretty sturdy box (the shelf vents will act as additional bracing to the panels).
I will :) So do the same design for both and then just like "stick" them together, but with a separation wall so they don't interfere on each other right?


Then i was completely wrong with my night of calculations jeje :)

i thought that two drivers could go in a box, because i saw the design, G-sub
Speakerplans.com and figured, that if they go in phase... But i trust you more than my little(no) experience :)

I'll do the calculations again, and see. My 2 drivers Colossus 18XB are on their way :)
And when i finish this, i want to do 2 Mid-High speakers. (but before lets finish this)

really thankfull to all! Nice to have this free and enjoyfull education :)
big up free education for all!
 
+1 Brian

If you put the two drivers in one box they will interfere with each other since no two drivers are exactly the same.

I just modeled that driver in a 221L box with Fb 36.4hz and one .304m (12") diameter port, .522m (20.55") length.

it's a monster :eek:

With a circular port? I just done some calculations, and i got this,
1driver 18XB C4 alignment α 1,2616 h 1,1034 q 1,2798 Vab (L) 187,064046 Fb (Hz) 36,4122 Fl (Hz) 42,2334 Vs (L) 11,75724126 Vb (L) 198,821287 Vdmax (m^3) 9,98E-04 dv (m)
0,194066525 è 0,25
Sv(m^2)
((0,25/2)^2)*Pi=0,05
Lv (op1) 0,20359849 Lv (op 2) 0,23139113

But you said you did a .522m of Lv?? My calculations are wrong?Or did you overdimensioned and then trim it for to tune it?

Another question, if i make a little bigger the Vb, does it have a bad effect on the response? What effect does it make??

thx again for all :)
 
When you mean a shelf, its a kind of rectangular port under the driver? Or do you have any link to a picture so i can figure what it is? my english is not too god :S

Imagine a rectangular vent. Now imagine a rectangular vent where three sides of the vent's cross-section are formed from the walls of the enclosure. There's your shelf vent.


So do the same design for both and then just like "stick" them together, but with a separation wall so they don't interfere on each other right?

That's correct.


i thought that two drivers could go in a box, because i saw the design, G-sub
Speakerplans.com and figured, that if they go in phase... But i trust you more than my little(no) experience :)

The G-Sub looks like a good design. I'd go further and extend the "A" brace to be a full internal panel, splitting the box into two, and adjust the height or depth of the box to hit the target Vb.

Note: that's going to be one heavy and likely difficult to move enclosure. You may want to consider just building separate enclosures for each 18, and then stacking them. They will be a lot easier to move around :).
 
With a circular port? I just done some calculations, and i got this,
1driver 18XB C4 alignment α 1,2616 h 1,1034 q 1,2798 Vab (L) 187,064046 Fb (Hz) 36,4122 Fl (Hz) 42,2334 Vs (L) 11,75724126 Vb (L) 198,821287 Vdmax (m^3) 9,98E-04 dv (m)
0,194066525 è 0,25
Sv(m^2)
((0,25/2)^2)*Pi=0,05
Lv (op1) 0,20359849 Lv (op 2) 0,23139113

But you said you did a .522m of Lv?? My calculations are wrong?Or did you overdimensioned and then trim it for to tune it?

Another question, if i make a little bigger the Vb, does it have a bad effect on the response? What effect does it make??

thx again for all :)

I was just playing with the numbers.

Your Math is good.

I came up with 221L Vb ( Vb = 442.14539L/2 ) + .522m legnth port with .304m diameter port to = Fb (Hz)36.4122. It is the same simulation as your design with one big port, not 3 per driver.

You should try WinISD Pro, free design software. LinearTeam
It will show you what happens when you increase Vb.
it has a very good help menu.
 
For a Vb=195,56L i choosed a Dv=0.25 => Sv=0,05 => Lv=0,41

Then i dimensioned W=0,609(2ft) x H=0,609+0,081(Height of shelf vent)=0,69 => D=0,4723m

Isn't it too long the port lenght? if my deepth is 0,4723 and the Lv = 0,41?? There is only left like 0.06 for air to flow...
Or you think i did some wrong calculations??
I know i'll have to trim it to tune it to Fb=36Hz but so much? :)

thx again for all :)
 
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Another newbie question, the Qts i use, is the one from the manufacturer spec, i don't calculate the Qts' that will be due to the amplifier resistange Rg. Does it make a big difference?
I've seen that there is this formula
Qes'=Qes(1+Rg/Re) ==> And then calculate Qts'=Qes'||Qms
It does make a difference when you look at the alignments tables for the value of Qts, but will it make a big difference?
And the problem is, I still haven't got the amplifier, how can i estimate the Rg from it? Rg=1 Ohm? Or maybe new amplifiers are nearly zero their Rg??

Thx again :) :) :) :) :) :)
 
Another newbie question, the Qts i use, is the one from the manufacturer spec, i don't calculate the Qts' that will be due to the amplifier resistange Rg. Does it make a big difference?
I've seen that there is this formula
Qes'=Qes(1+Rg/Re) ==> And then calculate Qts'=Qes'||Qms
It does make a difference when you look at the alignments tables for the value of Qts, but will it make a big difference?
And the problem is, I still haven't got the amplifier, how can i estimate the Rg from it? Rg=1 Ohm? Or maybe new amplifiers are nearly zero their Rg??

Thx again :) :) :) :) :) :)

I wouldn't worry about it. The effect is likely going to be unnoticeable.
 
For a Vb=195,56L i choosed a Dv=0.25 => Sv=0,05 => Lv=0,41

Then i dimensioned W=0,609(2ft) x H=0,609+0,081(Height of shelf vent)=0,69 => D=0,4723m

Isn't it too long the port lenght? if my deepth is 0,4723 and the Lv = 0,41?? There is only left like 0.06 for air to flow...
Or you think i did some wrong calculations??
I know i'll have to trim it to tune it to Fb=36Hz but so much? :)

thx again for all :)

I wouldn't worry about it. The effect is likely going to be unnoticeable.

:) good to know thx :)

For a Vb=195,56L i choosed a Dv=0.25 => Sv=0,05 => Lv=0,41

Then i dimensioned W=0,609(2ft) x H=0,609+0,081(Height of shelf vent)=0,69 => D=0,4723m

Isn't it too long the port lenght? if my deepth is 0,4723 and the Lv = 0,41?? There is only left like 0.06 for air to flow...
thx again for all :)

Do i have to worry about the length of the port then? :)

thx for your help :)
 
It looks so. The vent needs to be at least one vent diameter away from the opposite wall. E.g. if you're using a 6" diameter vent, the internal end of the vent must at least 6" away from the opposite wall.

It might help if you post up a diagram showing your current design.

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here you go :) hope you can see what's wrong
but now i think all seems pretty coherent

I don't have to worry about that box seems really cubic right? the standing waves effect doesn't matter with LF right?

thx again :)
 
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here you go :) hope you can see what's wrong
but now i think all seems pretty coherent

I don't have to worry about that box seems really cubic right? the standing waves effect doesn't matter with LF right?

thx again :)

You need to do a side cross-section, showing where the vent's shelf ends.

The shape of the box won't matter.
 
6-ports for 2 woofers... a few papers say it can be a good idea.


ProAudio woofers are designed for high efficiency and wide bandwidth. This often requires light paper cones, and modest durability edge surrounds and spiders. Pushing all air from a two woofer common volume design to just one port can cause slightly different Qts responses at each woofer, and "rock" or "skew" the cone+suspension such that the voice coil runs at an angle that rubs againt the pole piece. Multiple ports cleverly placed around the baffle can even out this air pressure for the best sound and highest durability. Old school experts have favorable comments on multiple ports.

True subwoofers often use durable rubber surrounds and double spiders that minimize cone rock. They can move so much air that very large diameter ports are required, which can limit the number of ports possible and necessary on the cabinet.
 

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6-ports for 2 woofers... a few papers say it can be a good idea.


ProAudio woofers are designed for high efficiency and wide bandwidth. This often requires light paper cones, and modest durability edge surrounds and spiders. Pushing all air from a two woofer common volume design to just one port can cause slightly different Qts responses at each woofer, and "rock" or "skew" the cone+suspension such that the voice coil runs at an angle that rubs againt the pole piece. Multiple ports cleverly placed around the baffle can even out this air pressure for the best sound and highest durability. Old school experts have favorable comments on multiple ports.

True subwoofers often use durable rubber surrounds and double spiders that minimize cone rock. They can move so much air that very large diameter ports are required, which can limit the number of ports possible and necessary on the cabinet.


that was my "newbie dream" , but then they made me realise, that if its my first speaker, formulas and real life is not the same, so if i have to tune 6 ports.... so finally one port , one driver will be enough to start having fun :) :)


But, by the way, How do they desing thoose BIG BIG SUBS???
How do they do the calculations? After, they spend a lot of time testing and tunnning the ports right??? See m pretty nice BIG double speakers :)
 
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