Vent size for 2245H

[Niklas Nord]

I´m building two boxes, each 380 - 400 liters for
one 2245H 18".

I´m thinking of the size of the went.
For two kind of boxes, one 380L and one 400L

TUNED TO 20hz


What size and length would you choose.

One design that i calculated was 6" and 97cm long

hmmm

[Ralf]

Hi Nicklas,

I have the same Project:

2245 vented Box (http://audioheritage.csdco.com/vbulletin/showthread.php?s=&threadid=1126&perpage=15&pagenumber=3)

Greetings Ralf

[Niklas Nord]

do you use two drivers?

[Ralf]

Originally posted by Niklas Nord
do you use two drivers?

No. This box is for one Driver only.

Greetings
Ralf

[4313B]

Originally posted by Niklas Nord
I´m building two boxes, each 380 - 400 liters for
one 2245H 18".

I´m thinking of the size of the went.
For two kind of boxes, one 380L and one 400L

TUNED TO 20hz

What size and length would you choose.
If you want to use a single vent then a 6" diameter port x 8.25" duct should do for 380 liters and a 7.5" duct should do for 400 liters. (According to BB6P)

[mikebake]

Here are some builders notes from when I put my 2245s in cabs as singles, just for some food for thought, since you mentioned the 20hz box tuning.

" Well, I got the initial tuning done.

Two 6" diameter ports each having a 13.25" duct for an Fb of 30.15 Hz with no fiberglass fill.

Gross physical enclosure volume not including the bracing, 2245H, or ducts, is 8.99 cubic feet.
Physical enclosure volume subtracting bracing, 2245H, and ducts is 7.42 cubic feet.
Net effective volume, again without any fiberglass fill, is 8.63 cubic feet according to D.B. Keele's formula.
Net effective volume, again without any fiberglass fill, is 8.89 cubic feet according to Bass Box Pro 6's formula.
Net effective volume, again without any fiberglass fill, is 9.37 cubic feet according to WinISD's formula.
Principle internal standing waves are at 218, 271, and 339 Hz due to the enclosure being so large. They would have been even lower if the enclosure wasn't squat, so that's a good thing.


Now for the listening tests, last night and this morning. This thing goes seriously deep. It sounds SO much better tuned to 30 Hz than it did at 24, 26, and 28 Hz. The math doesn't lie! I don't have any fiberglass fill in the enclosure and I would recommend an 18 dB/octave filter and not use any fiberglass fill at all. The 80-90-100 Hz, 12 dB/octave filter in my H/K AVR 7000 blows. Anyway, I'm extremely please with the sound. Very effortless and well defined even at 0.002 watts output. It's nice to listen at such low levels and still "Get it All". "What she really wants" by Russ Freeman is playing right now, the 0.002 watt light is lit and man does it crank out the bass! Nothing bumpy or overpowering at all, just deep, tight, and well matched to the 4430's. I'll play a few DVD's tonight when I get home and see how that THX stuff sounds :-) I'm going to finish up the bracing in the second enclosure this afternoon.
We measured the T/S parameters a few times. The Fs is definitely 15 Hz after break in. I will need to take both to another building with higher ceilings to measure. The 18 inch drivers have to be measured far away from all surfaces because their huge cone area picks up everything. I was the usual 3 feet away from all surfaces and that isn't nearly enough for the 18. I had never measured a 15 Hz Fs on a 2245H. I used two different measurement rigs with different electronics for each. A friend was also surprised about the aquaplas but said that the mass was probably integrated into the cone material at some point. The only JBL still using white aquaplas is the 2213. The aquaplas was changed to black on some drivers, such as the 128H-1. It's mass was integrated into the cones of other drivers. This cone looks like it could be using the black aquaplas but it is hard to tell."


Final tuning ended up something like 28.6hz

MBB

[pangea]

Originally posted by Niklas Nord
I´m building two boxes, each 380 - 400 liters for
one 2245H 18".

I´m thinking of the size of the went.
For two kind of boxes, one 380L and one 400L

TUNED TO 20hz


What size and length would you choose.

One design that i calculated was 6" and 97cm long

hmmm

Hej Niklas!

Try this link, there you will find all your answers.

http://www.ljudia.se/se/teknik/isd/vented.html

BR
Roland

[4313B]

Originally posted by pangea
Hej Niklas!

Try this link, there you will find all your answers.

http://www.ljudia.se/se/teknik/isd/vented.html

BR
Roland Yeah! I agree! Go there and get all your answers. :p

Pick a few up for me too!

I need to know why blondes have more fun and who collected the data? Is the fun general or specific?

Is anything more than a handful really wasted? If so, what should be done with the wasted parts?

If I can get those answered then, as far as I know, I'm pretty much "all knowing" from that point forward. :p

[GordonW]

Was that a handful or a mouthful? I'm always getting all mixed up about that. :D :D :D :D :D :D

Regards,
Gordon.

[pangea]

Originally posted by Giskard
Yeah! I agree! Go there and get all your answers. :p

Pick a few up for me too!

I need to know why blondes have more fun and who collected the data? Is the fun general or specific?

Is anything more than a handful really wasted? If so, what should be done with the wasted parts?

If I can get those answered then, as far as I know, I'm pretty much "all knowing" from that point forward. :p

1. Naah! Coming from extensive empirical research. It depends on your personal preferences.

2. Nothing should be wasted IMO. You recycle of course, what do ya think.

3. Yes you are, welcome to join the club. ;) :D :smthsail:

BR
Roland

[Hofmannhp]

Originally posted by Niklas Nord
I´m building two boxes, each 380 - 400 liters for
one 2245H 18".

I´m thinking of the size of the went.
For two kind of boxes, one 380L and one 400L

TUNED TO 20hz


What size and length would you choose.

One design that i calculated was 6" and 97cm long

hmmm

Hi Niklas,

I tried your box in my software with:
380liters
2245H
2% fill (you need minimum for internal damping)

important: dont let the port be to small, you should let the port about 1/3 the area of the speaker cone area to reduce air flow sonics in the resonance .

for 380liter box I found out:
2 ports of 6" diameter, lenght 25cm, 10". Then you will get -3dB with 25.75Hz, thats ok and means 20Hz with about - 7dB.

for 400liter box: 2 ports of 6" diameter, lenght 22cm or 8.6". With this you get -3dB with 25.17 Hz, that will give 20Hz at -6dB.

HP

[4313B]

Here's some additional results:

JBL -

380 liters (13.42 cu ft) tuned to 20 Hz using two 15.24 cm (6") diameter ports will require duct lengths of 56.52 cm (22.25")

400 liters (14.13 cu ft) tuned to 20 Hz using two 15.24 cm (6") diameter ports will require duct lengths of 52.71 cm (20.75")


BB6P -

380 liters (13.42 cu ft) tuned to 20 Hz using two 15.24 cm (6") diameter ports will require duct lengths of 54.1 cm (21.3")

400 liters (14.13 cu ft) tuned to 20 Hz using two 15.24 cm (6") diameter ports will require duct lengths of 50.49 cm (19.88")

If you use the JBL formula then you are pretty much assured enough duct length available so some can be removed during fine tuning with measurement equipment. I've personally never had any problem with the BB6P formula either.