Mininum enclosure size for 3way with 2225 H-8 Woof

[Squarewave]

Hi all,
Since stumbling in the door here last month, I've had a great time reading, talking and learning. I can also blame the forum for this new itch I have to build some enclosures. It's been a long time. I have not built any enclosures in 25 years, and before that, they were always built for my sound reinforcement company.

The last ones I did build numbered 24 total, front loaded with 2 15's and a horn each. Great 4way mains for up to 10,000 seats outside Of course when your building that many large enclosures and your not rich, you have to use shop plywood.

I have never built any home enclosures, and just building two(or 4) would allow me to use much higher quality material. But what design?....and what to load in them?

I've been fishing through my old gear looking for a good starting place.
I found a nice pair of 2220 B's. I had these reconed some years ago to 2225 H's @8 ohms. I remember these producing very punchy LF response and lot's of it (when it was wanted).
I think I might want to build my new boxes based on these as the woofers.

Thinking 3 way,front loaded, and I will probably have to buy everything else. Also sure I will go with the best birch plywood I can find. Also thought it might be fun and more flexable for the future to build each range in its own cab. This way,if I want to try somthing totally different for mids later, I only have to change the mid enclosure and/or driver. Hmmm just an idea, thinking out loud.

These boxes should be as small as possibile, but at least the minimum to get good returns from these drivers. Can anyone recomend a good place to start learning modern enclosure design?

Thanks
Dan

[Loren42]

Hi all,
Since stumbling in the door here last month, I've had a great time reading, talking and learning. I can also blame the forum for this new itch I have to build some enclosures. It's been a long time. I have not built any enclosures in 25 years, and before that, they were always built for my sound reinforcement company.

The last ones I did build numbered 24 total, front loaded with 2 15's and a horn each. Great 4way mains for up to 10,000 seats outside Of course when your building that many large enclosures and your not rich, you have to use shop plywood.

I have never built any home enclosures, and just building two(or 4) would allow me to use much higher quality material. But what design?....and what to load in them?

I've been fishing through my old gear looking for a good starting place.
I found a nice pair of 2220 B's. I had these reconed some years ago to 2225 H's @8 ohms. I remember these producing very punchy LF response and lot's of it (when it was wanted).
I think I might want to build my new boxes based on these as the woofers.

Thinking 3 way,front loaded, and I will probably have to buy everything else. Also sure I will go with the best birch plywood I can find. Also thought it might be fun and more flexable for the future to build each range in its own cab. This way,if I want to try somthing totally different for mids later, I only have to change the mid enclosure and/or driver. Hmmm just an idea, thinking out loud.

These boxes should be as small as possibile, but at least the minimum to get good returns from these drivers. Can anyone recomend a good place to start learning modern enclosure design?

Thanks
Dan

JBL recommends 5 cubic feet.

http://www.lansingheritage.org/html/jbl/specs/pro-comp/2225.htm

You can go smaller, but it starts to eat up bass response as you go. The question is, how much bass can you live without? The 2225H has a Fs of 40 Hz, which isn't really deep in the HiFi world.

Also, swapping out a mid or whatever will be more than simply exchanging a driver. You will also need to modify or rebuild the crossover to make it all work.

Vance's book covers a lot of ground about the whole process from driver selection, measurement of T/S parameters, box design, box material selection, crossover design, and measurement techniques.

I would highly recommend getting and reading that book before you do anything at all. When you get that done you will have lots of questions and you should turn to help here for those answers, then start the design.

I fully understand where you are coming from as I was doing similar things 25 years ago in the music industry. An unbelievable amount of things have changed since then. Speaker design has grown up out of the black art and repeated experiments to generate a design to a bonafide science where everything is quantifiable. The world of mathematics is now your friend.

A good start is Vance Dickason's The Loudspeaker Design Cookbook.

[jcrobso]

A lot us here have done many things over the years, building boxes and setting up high quality sound systems, many are still in the business.
Please re-post with any questions you have, many here have the software programs need to build boxes, just post a question.
Once you get going post some pictures.:D

[spkrman57]

Use 2.6 cubic ft internal, but rolloff will start around 70hz, gradually decreasing until below 45hz where it drops rapidly.

I like my 2226 drivers in 3 cu ft tuned to 38hz. My tube amps make it sound rather nice!

But it may not be enough LF response for you though!!!

Regards, Ron

After re-reading OP, I noticed he said:
" I found a nice pair of 2220 B's. I had these reconed some years ago to 2225 H's @8 ohms."

That would cause the LF response to rolloff even sooner as the 2220 has a larger magnet and that will affect the T/S parameters!

[speakerdave]

You have frankenwoofers there--a cone kit in the wrong frame. It'll have unpredictable performance; i.e., the T/S of either the 2220 or the 2225 do not apply.

[Ruediger]

You have frankenwoofers there--a cone kit in the wrong frame. It'll have unpredictable performance; i.e., the T/S of either the 2220 or the 2225 do not apply.

But still You can measure the Thiele-/Small-Parameters or ask somebody to do that for You.

Ruediger

[Squarewave]

You have frankenwoofers there--a cone kit in the wrong frame. It'll have unpredictable performance; i.e., the T/S of either the 2220 or the 2225 do not apply.
Speakerdave,

I'll be the first to admit many of my modifictions were unscientific, hit and miss, or "just get the job done" back in my sound co days. I think that was the case for having these 2220's modified, I must have needed more low end in a smaller system somewhere?? Anyway, I'm not dead set on using these modified 2220's, but would like to find a proven design for a JBL 3 way system with 15" woofers.
Thanks
Dan

[speakerdave]

Speakerdave,

I'll be the first to admit many of my modifictions were unscientific, hit and miss, or "just get the job done" back in my sound co days . . . .

I think people are free to do what they want, with a couple of provisos. My point was that because of the modification nobody here could do what you asked.


. . . . would like to find a proven design for a JBL 3 way system with 15" woofers . . .

I would suggest a four-way, and the 4344 would be it. As GT says, the UHF super tweeter doesn't really count.

[A9X]

If you are happy to EQ, and an F3 of near 40Hz (more than enough for most music), then 55L net, ported with 2 x 8.6cm ports gives an un-equalised response like so.

http://i228.photobucket.com/albums/ee287/A9X-308/JBL2225H6noeq.gif

Then add a Q=2 HPF at 42Hz and the response changes to,

http://i228.photobucket.com/albums/ee287/A9X-308/JBL2225HFR6th.gif

with an EQ'd excursion of,

http://i228.photobucket.com/albums/ee287/A9X-308/JBL2225HX6th.gif

and a port air speed of.

http://i228.photobucket.com/albums/ee287/A9X-308/JBL2225HPAS6th.gif

And it can take nearly 600W before hitting Xmax.

http://i228.photobucket.com/albums/ee287/A9X-308/JBL2225HPAS6th600W.gif

[Squarewave]

I stumbeled across a pair of L 45's today
They had no 15's with them, a bit beat up, and were pretty reasonable. Of course I bought them,and before even dusting them off I loaded my 2220-2225 H frankendrivers in.
So far, I love em, and now this little stroke of good fortune will give me plenty of time to play with these before I decide which way to go on the build. Thanks again to all of you for your opinions and experience!:applaud:

Dan