Need Help Porting an enclosure

[Student]

This is my first post. I hope I put it in the right location. There seems to be a lot of very knowledgeable and helpful people on this forum that I can learn from. I do not have any speaker building software available to me so I am requesting assistance from the members of the Audio Heritage Forum to help me find the proper port size/dimensions to get the best sound from these cabinets. Your input and advice is welcomed and appreciated.

I am currently building a set of enclosures to be used for sound reinforcement. I am using divers that I already own. Using other drivers would create a cost issue that would kill this project. Each enclosure will house (2) JBL 2225j and a (1) JBL 2445j and will sit on top of an EV 180a loaded sub cabinet. The cross-over duties of this system will be covered by the DSP in the XTi series amps (1 XTi 1000 running stereo for the horns, 1 XTi 1000 running mono per cabinet for the 15's, Xti 4000 running the subs)

The enclosures have an internal volume of approximately 6.2 cubic feet with the drivers loaded. I have enough room for 2 ports up to 4" in diameter and 2 more up to 3" in diameter. I know this should have been included in the design before construction began, but it seems I had a Brain-Fart that day. The end-goal of these speakers are for sound reinforcement, so obviously SPL is very important. But I do not want to sacrifice sound quality to get the volume.
Thank you very much for your time.

[Lee in Montreal]

You probably have Excel on your computer. Use it with this spreadsheet to calculate the cabinet's volume and port tuning depending on what you need. http://www.troelsgravesen.dk/ports_files/ports.zip

[Student]

Unfortunately I do not have excel. (note to self... get excel.) This PC is a 2004 version of XP. But thank you Lee, I'll save that link for when I get it... Soooo, we're back to needing help again...

[Hoerninger]

Presumably the spreadsheet will run with OPEN OFFICE (Free).
___________
Peter

[macaroonie]

Have you used Win ISD ? 2225J is in the database.

http://www.linearteam.dk/default.aspx?pageid=winisdpro

Your XP should support it and its not a data heavy app.

[Lee in Montreal]

The upper range of your 2225s will most likely be around 400Hz, while the lower range of the 2445 will be around 800/1000Hz unless you run a big horn. You'll therefore be mising something in between. As fas as calculating the port for the cabinet, you will need to use a simulator to find the best compromise between sound quality and output level. There's not one universal answer, only one best compromise tat suits your needs. You'll want 2 , 3 ir even 4 ports, but all of the same size. Here's a quick calculator that only gives a very partial answer as it doesn't tell how the drivers will behave in term of response and excursion (it only tunes a port to a certain frequency given a cabinet size) : http://www.psp-inc.com/tools.html

[1audiohack]

Are you thinking 2245? 2225's play easily and well above 800Hz, JBL's highest recommended crossover is 1200Hz.

[4313B]

The upper range of your 2225s will most likely be around 400Hz, while the lower range of the 2445 will be around 800/1000Hz unless you run a big horn.

Why only 400 Hz? What happened to his particular 2225's?

[Student]

Thank you for the links. this seems to be a good starting point.

JBL specs say 1200hz for the 2225 and 500hz for the 2445. I do find it odd that most treads I've read on the 2225 are from people talking about them used below mid-bass frequencies only. But JBL told me they are not good for lower frequencies... That they are not sub-woofers.

[Robh3606]

But JBL told me they are not good for lower frequencies... That they are not sub-woofers.

They won't do the last octave 20-40Hz however they are good to 40Hz and have a slam factor that can peel paint. Run them in a box program one driver in 4 cubic ft the cinema boxes are pairs in 8 cubic ft.

Look for Win ISD http://www.linearteam.dk/default.aspx?pageid=winisd

It has all the JBL drivers preloaded in the program also look here:

http://www.jblpro.com/BackOffice/Pro...ts/enclgde.pdf

Rob

[Student]

They won't do the last octave 20-40Hz however they are good to 40Hz and have a slam factor that can peel paint. Run them in a box program one driver in 4 cubic ft the cinema boxes are pairs in 8 cubic ft.


Rob

That makes sense now. Did JBL also use the 2225 in 2 way cabinets with a compression driver?

[4313B]

The 4670 with dual 2225's instead of dual E145's along with the serpentine lens was always a hoot and a holler...

There were later versions of that configuration too, I just don't remember the model numbers anymore.

The important part is that it was a 4508 box. One can stick whatever they want on top. Even a SAM1HF!

[macaroonie]

That makes sense now. Did JBL also use the 2225 in 2 way cabinets with a compression driver?

Yes : http://www.jblproservice.com/pdf/The...eries/4673.pdf

You really need this link to do your background research :

http://www.jblproservice.com/NAVIGAT..._nav_tech.html

[Student]

Great info. 👍 Thanx. ✌