2241 Tuned Enclosure Plans?

[60cyclehumm]

Hey everyone,
For staters I'd like to say hello to everyone here as I'm new to the site. I've always like JBL's products especially using their GTi car audio series drivers back in my car audio days ofthe late 80's - early 90's. I'm thrilled to find the site!

Last may I bought this pair of cabinets off of Craiglsist for $80.




The guy I bought them from said they were EV. He bought them used and could only go by what the guy he bought them from told him. Once I got them home I came to the conclusion they were home made, but very well constructed. I also did some web searches but found nothing like this made from EV, much less by anyone elese. The guy told me they were loaded with EVM 18's, "had a lot of bass and were very loud". Not knowing if the cabinets were specifically built for the EVM's and not being a big of them anyway, I figure I'll be better off just loading them with JBL's. It seems the 2241 packs the biggest bang for buck on the used market and aren't a lot more than what I'm finding EVM's for. By the way, these cabinets have vents on either side of the internal enclosures for the 12" mids. I figure I'll block them off and install ports for the JBL's. I've now searched the interwebs lookig for a good cabinet plan but all I've come up with is JBL's site suggesting a 10cu.ft. cabinet tuned to 40hz. But I have read that they can be tuned to 30hz, which is what I wold prefer, if not lower, but I do know these drivers have their low-end limitations. I haven't calculated the exact volume of these yet but intend to soon. Just doing quick math, I have to guess these to be near 11 cu. ft. wiithout dedudtiong the 12" mid cabinet, which is triangler, or wedged, shaped. My rough guess is they take up at about a cubic foot of the whole cabinet. Being a carpenter/cabinet maker by trade, I can most certainly adjust the internal volume (smaller) if need be. Any suggestions would be most appreciated. A few details of my system is that they won't be used for live sound, just my workshop and a few ocasional outdoor parties. My plan is to tri-amp the system and have a 3-way 24bB slove electronic crossover.

I plan start threads about my mid and HF drivers seperatly from the LF's.

[Mr. Widget]

Welcome to the LHS Forum.

What do you plan to do with these cabinets? Will they be for crazy loud music playback, home Hi-Fi... ?


Widget

[60cyclehumm]

just my workshop and a few ocasional outdoor parties

[Mr. Widget]

just my workshop and a few ocasional outdoor parties

So then would you say the goal is closer to a PA speaker than a Hi-Fi speaker? The reason I ask is that a PA type speaker will probably satisfy your needs and cost far less to achieve.


Widget

[60cyclehumm]

I'm hoping to find someone to tell me to make the volume of the cabinets to be X and install X number of X diameter ports cut to X length to achieve a tune of 30hz. Being a carpenter/cabinet maker by trade, I can reduce the volume to whatever is best.

[60cyclehumm]

I also understand the ports can be rectangular, which is what would probably work best as there's little room for 4" ports on the baffle board.

LOL... wouldn't it be awesome to find these cabinets were actually built for 2241's or similar JBL's!

[Mr. Widget]

I'm not sure when you say "speaker" you mean driver or you mean aborting my stated mission. I guess I don't understand what any of that has to do with tuning the cabinets for 2241's.

I'm hoping to find someone to tell me to make the volume of the cabinets to be X and install X number of X diameter ports cut to X length to achieve a tune of 30hz.

The reason for my questions was that if your goal was to produce a higher performing system I would make suggestions to achieve that goal.

The simple answer to your question is to use the JBL enclosure guide: https://www.jblpro.com/pub/manuals/enclgde.pdf

Look at alignment 13.


Widget

[60cyclehumm]

Yeah, as stated in my posts, I've found that guide but it's a 40hz tune. I read somewhere that these can be tuned to 30hz, unfortantely I didn't bookmark it.

[grumpy]

10ft3 box (effective)
3/4" ply baffle
4" diameter hole (no duct)

Free windows program WinISD lets you try variations out.
2241H pdf is also online (google).

[60cyclehumm]

10ft3 box (effective)
3/4" ply baffle
4" diameter hole (no duct)

Free windows program WinISD lets you try variations out.
2241H pdf is also online (google).

So you're essentially saying a single 4" diam. x 3/4" long port tunes it to 30hz in a 10' cubed box???

I'll look into the WinISD deal. I was just hoping someone on here's already tuned these to 30hz.

[grumpy]

essentially and specifically.

This will vary a bit with stuffing, and you can play with
the port volume parameters (e.g., use two 6"dia ports 12" long),
which is more complex than a hole, but might "whistle" less.

To get closer (if it matters) you'll have to measure somehow
(possible to get close by eye with a tone generator, looking
for minimum cone motion).

Might also want to start rolling it off electronically below
port cutoff (e.g., a +3dB 2nd order bump filter at 35Hz will net
a response down to 30Hz -and- protect the driver from stupid stuff)

[60cyclehumm]

Thanks Grumpy. Pardon my questioning. Iit just seemed odd that it happens to work out as a simple 4" inch hole.

Using a tone generator, frequency am i to look for min. cone travel at my targe tune freqency?


The active cossover i have won't allow me to roll off below the tuned frequency, just the upper end of where i want the driver to play to. Would you suggest doing a passive design for rolling off below the tuned freqency?

I'd like to tell yopu what cossover i have as it's once from an old car audion company called Image Dynamics that label slapped their name on a pro sound unit. They did the same on some 31 band EQ's that I've learned were made by DOD.

Sorry for being such a newb.

essentially and specifically.

This will vary a bit with stuffing, and you can play with
the port volume parameters (e.g., use two 6"dia ports 12" long),
which is more complex than a hole, but might "whistle" less.

To get closer (if it matters) you'll have to measure somehow
(possible to get close by eye with a tone generator, looking
for minimum cone motion).

Might also want to start rolling it off electronically below
port cutoff (e.g., a +3dB 2nd order bump filter at 35Hz will net
a response down to 30Hz -and- protect the driver from stupid stuff)

[macaroonie]

Hi , are you sure the ducts either side of the 12" doghouse are not for the main bass volume ?
Looking at your pic the doghouse seems to be a sealed triangular volume as you describe.
Definitely looks like a sturdy well made box , no point in messing with it other than tailoring for the intended drivers.
If as I suspect the ducts are indeed for the bass driver then if you measure them up Win ISD

( Linearteam.org ) can deal with this in it's options menu. In fact you can sim. the tuning with the 2241 parameters in place and see what it comes up with by way of response.

If you fire up the port dimensions the fellahs in the gallery will run it through for you , see what we all come up with. I wouldn't be at all surprised if there is only a small mod needed if any to suit the drivers you have.

What you got planned for mids and tops ?

Just did a quicky for you. Assuming 1 cu ft = 30ltr ( its 29ish ) and as you should be able to see I've assumed the vents to be 323 mm ( 13" ) x 68mm (2.5"ish )
The programme predicts vent length and you can see the results in the second snapshot , where it suggests a vent length of 200mm ( 8" )

I'll bet your vents are not to far away from that judging from what I can see in your pic.

Tuning is for 35Hz. Looks like the builder took steps to time align the bass and mid drivers .... nice touch.

[grumpy]

Would you suggest doing a passive design for rolling off below the tuned freqency?

Oh hell no

Just be careful with subsonic stuff and big amps... those drivers will take a boatload
of power, but there is no "push back" from the cabinet air below port resonance, so
it's easier to bottom out the driver. If you're EQ has a band below 30Hz then drop
it down a smidge.

... and what mac said about the existing ports. I didn't want to just guess on the dimensions.

[60cyclehumm]

Oh hell no

Yeah I didn't think that was the way to go as I was typing it. My EQ's are packed away but I'll have to get one out to see what the first band is. What are they typically on a 31 band unit?