JBL 2245 port location on a 10 cubic foot enclosure.

[David Ketley]

Is there an exact location from the 2245 for the ports on the design for an enclosure of 10 cubic feet? I know that the port length is crucial to the tuning.

Dave

[Allanvh5150]

Feel free to put the ports anywhere you like. The back of the cabinet looks the best as long as they can breathe.

Allan.

[ratitifb]

according to the wavelength at the tuning frequency :hmm: i think that should not be so critical ...

[Odd]

Placement of the port is not critical. You can place it wherever you want. You should probably have more than one.
Download http://www.linearteam.dk/ so you can find the correct port size.
It is not easy to find the correct internal volume of the enclosure, you must have measure equipment to tune the enclosure properly.

[David Ketley]

Port size seems to be 9" or 2 x 6" I will make the length adjustable so I can get the best response.

I guess it easy to reduce volume by adding some mass but not good to get it too small.

Dave

[Lee in Montreal]

A pair of 6" ducts is a good idea. Sonotube works fine.
Three 4" will work too. I love ABS plumbing tubing :D

Or Onken style cabinet/porting makes for a more rigid cabinet.

Lee

[Champster]

David,
While you're developing your build, have you considered using one of the designs in this article (http://www.lansingheritage.org/html/jbl/reference/technical/1983-subs.htm) to optimize the use of a 2245?
Paul

[David Ketley]

Yes I have been trawling through all the threads on a build for the 2245 my biggest problem is finding some reasonably matched units with some JBL cones. There is an add on Ebay for a pair but he has used non JBL cones I guess its important that the units are genuine JBL?

Whats the best crossover frequency from the 2245 to the JBL 2123H? Im crossing at 160Hz but can get modules to go lower if required.

[more10]

I guess its important that the units are genuine JBL?
Yes

Regarding the port placement, if you place the port close to the floor, the tuning will be somewhat lower.

Have a look at Onken designs.

[Champster]

David,

My take on the port placement is that, at these frequencies, it doesn't matter where you put it, but, for it to breath properly, you'll need a full diameter of the port clearance from any object either inside or outside the cabinet.

On the 2123H. I looked at that for the system I'm building, but I decided to try the 2206h (12") driver instead because it goes lower (handling more power) thus allowing for a crossover over below 100hz. This approach provides for a crossover free zone between ~80 & ~1000. Although I've never heard the 4345, I don't think I'd like it very much. The 2245 crosses over at 290 at only 12db/oct. I wouldn't like having the 18" driver going that high. So, I agree with your approach of crossing over the 2123 as low as possible. The 2123 has the ability to cross over to a 1" CD at a higher point, but will require about 5db of boost if you want to cross it over at ~160hz. You'll be able to have the high pass for the CD much higher than me. The only "cost" of crossing over the 2123 at 160hz will be lower total acoustic output just because the 2123 will run out of steam faster than the 2445 would at those frequencies. I would be willing to give that up to get the crossover point lower but I haven't calculated the max spl at 160hz that the 2123 will produce. I imagine, the output is pretty low but could be wrong.

I opted to take Lee's advice and get a few frames and have them reconed. They are beautiful and although it was more money, I'm glad I did it this way. Even going this way, these are still relatively inexpensive drivers as it isn't hard to spend $1000 on a 15" subwoofer today from Focal, etc.

I am also building something like a 4345 but with the 12" as mentioned above and a 2" compression driver. Both choices were based on the ability to have one crossover point in the 200 - 5000 range. My cabinet however is going to be significantly different than the 4345 and look a lot more like a K2 S9900. Are you using DSP?

I wish we lived closer so we could compare the two approaches. Make sure your design includes mounting the 10" and the CD as close together physically as possible to get them to blend better and reduce the horn sound as much as possible.
Paul

[David Ketley]

The 2245 was crossed at 290Hz I believe and looks OK on the 2123 maybe that should be my crossover point? As soon as you start adding boost I find its detrimental to what you hear. The whole idea of multiple drivers is to match there frequency responses without adding in more complexity?
I'm using a Marchand Active crossover and like its neutrality.

Dave

[Ian Mackenzie]

Keep the port(s) at leat one diameter clear of any side walls and at least one diameter clear of any rear walls.

Keep insulation away from the port exists and smooth off the cut ends.

There is a parameter call Q L where losses from resistive port flow impact on the tuning in large signal testing (not small signal) .

I was watching the Aliens movie last night and when the LT426 blew up I could feel the air movement from the 2245 and vents across the room.

[svollmer]

I was watching the Aliens movie last night and when the LT426 blew up I could feel the air movement from the 2245 and vents across the room.

Awesome!!!!

[Fort Knox]

David,
While you're developing your build, have you considered using one of the designs in this article (http://www.lansingheritage.org/html/jbl/reference/technical/1983-subs.htm) to optimize the use of a 2245?
Paul
I 'd be more interested in sp. placement rather then the port..