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-   -   2x18" with JBL 2243. Need design advise (http://www.diyaudio.com/forums/subwoofers/228195-2x18-jbl-2243-need-design-advise.html)

Joppepoppo 19th January 2013 06:03 PM

2x18" with JBL 2243. Need design advise
 
Hi all,

I've been down the diy road for some time now and I'm close to the finishline. I use a total of 4 18" subs in test boxes (170l) for my combined music and HT setup. I've tried them in different locations but regardless of how they measure, I always like the sound best when they are configured as 2x18" with the mains stacked on top of them (JBL 15"+JBL 1,5" with 15" WG).

Thats why I've decided to build the final boxes as two 2x18 (I also have 2 18" Ciare's if I find a need to place woofers on multple locations).

As I'm using JBL 2243, getting the right numbers for WinISD is not easy. I've used the ones I found over at audioheritage and using them 140l per box with a cutoff at 28Hz seems fine.

My questions are:

I really need design proposals. Is there any site with lot of pictures on 2x18" boxes for home use? I guess these things is'nt quite normal eh?:o

Is there any disadvantages having the woofer drivers placed very close to each other? I don't want a too wide box for appearance reasons.

Is there any other design besides 2x18" BR I should take a look at?

The bass ports need to be at the front since I want to put the boxes close to the back wall. Any advice on a nice design?

Would it be wiser to have larger boxes than 140l? I have several means for EQ (SMS-1, BSS366 f.ex.) and I want the boxes to be as small as possible without constraining the drivers too much.

I haven't done any carpenting the last 15 years so I would also really appreciate if someone could guide me to a step-by-step site showing the different steps of putting a speaker box together. Yes, I have googled but I still would like to know what site you'd recommend ;),

A lot of questions, I know, and I'm sure I forgot some...

Thank you for any input on this.

I will start a new thread when I start the build later this spring/summer.

Kind regards,

Jakob

Inductor 20th January 2013 02:25 AM

2 Attachment(s)
Quote:

Originally Posted by Joppepoppo (Post 3333256)
Is there any other design besides 2x18" BR I should take a look at?

This woofer is good as a BR or Horn.
This are simulated proposals and I don't see it being a good sub as you imply (F3 being superior to 50Hz i.e. 55Hz).
You say ""4 18" subs in test boxes (170l) "", I guess you have 2x18" in a 170L box 85L for each driver. ;)
Again, one JBL 2243H, VB = 85.0 L, FB = 50 Hz, 95.5 dB/2.83V/m each,
F3=54Hz, F6=47Hz (-3dB in room), F12=38Hz, F24=26Hz.
With 2x parallel JBL 2243H, VB = 170.0 L, FB = 51 Hz, 101.9 dB/2.83V/m.
F3=56Hz, F6=48Hz (-3dB in room), F12=39Hz, F24=27Hz and this is pushing the envelope.

I would go with the horns (as a concept). It's this what you were expecting?
(Note, I don't have experience with active manipulation and DSP, and I don't know what to expect...)
JBL 2243H
link2
link3

Kindhornman 20th January 2013 02:57 AM

Joppepoppo,
That driver should be able to get down to its resonant frequency in the right box, but that box will be large. If I was you I would build the optimum box for a single 18", one per side and keep the box size down. Unless you are in a huge room two 18" should be more than enough to get you all the bass that you need. Go bass reflex, that will be the most practical. I actually have double 18" bass horns but I wouldn't think of putting them in a normal room, it takes multiple horns to get the basic mouth size of a horn to get anywhere near to where the bass reflex will go in a much smaller package. A 30hz mouth size horn is awful large.

dangus 20th January 2013 03:34 AM

A reasonable starting point would be to copy, or at least model, the cabinets that JBL used with these woofers. This thread mentions some, like the P798.
jbl 2243

You should make sure the drivers haven't been reconed as something different, if you don't know their history. It's not hard to measure Fs, which should give some idea of which specs apply.

As for construction, the crucial power tool for me was a router. It allowed me to cut panels oversize and trim flush, round over edges and corners, and cut perfect holes for drivers and ports. That, and a "screwdigger" bit to drill and countersink screw holes.

Inductor 20th January 2013 04:09 AM

Quote:

Originally Posted by Joppepoppo (Post 3333256)
...and I want the boxes to be as small as possible without constraining the drivers too much.

Quote:

Originally Posted by Kindhornman (Post 3333918)
Joppepoppo,
That driver should be able to get down to its resonant frequency in the right box, but that box will be large.

Not practical, the box would need 300L or more... and 30Hz@F10/F12.

Inductor 20th January 2013 04:32 AM

Quote:

Originally Posted by Joppepoppo (Post 3333256)
...and I want the boxes to be as small as possible without constraining the drivers too much.

Quote:

Originally Posted by dangus (Post 3333939)
A reasonable starting point would be to copy, or at least model, the cabinets that JBL used with these woofers. This thread mentions some, like the P798.
...

As I said before and for the same reason, not practical, the box would need 300L or more... and 30Hz@F10/F12 and in this case they are. Unless OP changes it's mind. :cool:
link2>>JBL P749= 366.09 liters for two drivers
link3>>JBL P798= 532.06 liters for two drivers

Joppepoppo 20th January 2013 11:19 AM

Thank you for your replies. A lot of wisdom here :)

Just to clearify. My testboxes are about 170-200l and contain one driver each.

I've seen other recommendations for this driver to be used in JBL S1S-EX boxes that originally used JBL 2242. The JBL 2242 share the same motor but have a lighter cone, raising the Fs to 35Hz and increasing the sensitivity.

If I've done the calculations right, that box is about 260l. Is that the minimum size I could expect? Simulations in WinISD seem nice with 240l tuned to around 30Hz.

Since the presented T/S numbers for the 2243 are known to maybe not be accurate it's hard to know where to start.

When playing movies or music on "normal" levels I feel 2 subs are enough. The reason I'd like to use all 4 drivers is to get headroom. When playing loud organmusic or trance with a lot of sub 30Hz content, I can easily hear the difference between 2 or 4 subs. 4 subs sound tighter and I guess they should since the drivers need to move much less.
Am I missing something here?

Is there much to be gained soundwise to build two large boxes and only use one driver per box?

Inductor 20th January 2013 04:07 PM

Quote:

Originally Posted by Joppepoppo (Post 3334235)
Just to clearify. My testboxes are about 170-200l and contain one driver each.

You should have said that BEFORE!
That would have saved a lot of work and... (friendly discussing and lost time). :D

weltersys 20th January 2013 04:48 PM

Quote:

Originally Posted by Joppepoppo (Post 3334235)
Just to clearify. My testboxes are about 170-200l and contain one driver each.

If I've done the calculations right, that box is about 260l. Is that the minimum size I could expect? Simulations in WinISD seem nice with 240l tuned to around 30Hz.

The reason I'd like to use all 4 drivers is to get headroom. When playing loud organmusic or trance with a lot of sub 30Hz content, I can easily hear the difference between 2 or 4 subs. 4 subs sound tighter and I guess they should since the drivers need to move much less.
Am I missing something here?

Is there much to be gained soundwise to build two large boxes and only use one driver per box?

Four subs can do the same output as two with only 1/4 the power per driver.
Since you have the drivers and boxes, why not just tune low and go?
LF droop will be on a continuum from around 300L and down, you just need to decide how much space and lumber you can afford to use, and how low you will tune the boxes.
Trance and organ music has content down to the 16 Hz region, you may want to tune down in the 25-30 Hz range and not have the speakers flap down low.

Inductor 20th January 2013 04:54 PM

Quote:

Originally Posted by Joppepoppo (Post 3334235)
When playing movies or music on "normal" levels I feel 2 subs are enough. The reason I'd like to use all 4 drivers is to get headroom. When playing loud organmusic or trance with a lot of sub 30Hz content, I can easily hear the difference between 2 or 4 subs. 4 subs sound tighter and I guess they should since the drivers need to move much less.
Am I missing something here?

Anyway, if you parallel two woofers in a different box similar to the JBL P749= 366.09 liters or JBL P798= 532.06 liters you can expect your sound to increase about 6dB (~95.5 dB/2.83V/m (1x)/~101.9 dB/2.83V/m (dual))


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