2x18" with JBL 2243. Need design advise

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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?:eek:

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
 
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
 

Attachments

  • JBL 2243H, VB = 85.0 L, FB = 50 Hz, 95.5 dB2.83Vm. F3=54Hz, F6=47Hz (-3dB in room), F12=38Hz, F2.jpg
    JBL 2243H, VB = 85.0 L, FB = 50 Hz, 95.5 dB2.83Vm. F3=54Hz, F6=47Hz (-3dB in room), F12=38Hz, F2.jpg
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  • JBL 2243Hx2, VB = 170.0 L, FB = 51.2 Hz, le 0 dB correspond à 101.9 dB2.83Vm. F3=56Hz, F6=48Hz (.jpg
    JBL 2243Hx2, VB = 170.0 L, FB = 51.2 Hz, le 0 dB correspond à 101.9 dB2.83Vm. F3=56Hz, F6=48Hz (.jpg
    81.6 KB · Views: 355
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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.
 
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.
 
...and I want the boxes to be as small as possible without constraining the drivers too much.

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
 
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?
 
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.
 
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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))
 
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.

These are they, on fig.1 a 2242 driver in a small box: JBL 2242H, VB = 97.4 L, FB = 37.6 Hz
(F3=57Hz, F6=44Hz, F12=32Hz, F24=20Hz)

On fig.2 the 18" 2243 in a small box: JBL 2243H, VB = 45.7 L, FB = 45.8 Hz
(F3=75Hz, F6=58Hz, F12=42Hz, F24=25Hz)

Note: they are just example simulations always having in mind that functions/alignments objectives for both passive filtering and active amplification/DSP (in this case) are rather different.
 

Attachments

  • Fig.1 JBL 2242H, VB = 97.4 L, FB = 37.6 Hz, 95.4 dB2.83Vm. freq.output.jpg
    Fig.1 JBL 2242H, VB = 97.4 L, FB = 37.6 Hz, 95.4 dB2.83Vm. freq.output.jpg
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  • Fig.2 JBL 2243H, VB = 45.7 L, FB = 45.8 Hz, 95.5 dB2.83Vm. freq.output.jpg
    Fig.2 JBL 2243H, VB = 45.7 L, FB = 45.8 Hz, 95.5 dB2.83Vm. freq.output.jpg
    130.2 KB · Views: 128
In a similarly designed box (170 L), notice that this his only a comparison and not an optimized enclosure/alignment for the designated driver, we have for the same two drivers JBL 2242 vs. JBL 2243,
(drivers are similar in SPL calculated at 95.4(1)/95.5(2) dB/2.83V/m)

Fig.3 JBL 2242H, VB = 170.0 L, FB = 39.5 Hz freq. output
Fig.4 JBL 2243H, VB = 170.0 L, FB = 32.0 Hz freq. output

Also notice the high attenuation >5dB of the low frequencies, with alignments close to 30Hz tunning, in the second case.
 

Attachments

  • Fig.3 JBL 2242H, VB = 170.0 L, FB = 39.5 Hz, 95.4 dB2.83Vm. freq.output (2).jpg
    Fig.3 JBL 2242H, VB = 170.0 L, FB = 39.5 Hz, 95.4 dB2.83Vm. freq.output (2).jpg
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  • Fig.4 JBL 2243H, VB = 170.0 L, FB = 32.0 Hz, 95.5 dB2.83Vm. freq.output (2).jpg
    Fig.4 JBL 2243H, VB = 170.0 L, FB = 32.0 Hz, 95.5 dB2.83Vm. freq.output (2).jpg
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JBL 2242 vs. JBL 2243

(JBL 2243 and...) JBL 2242 share the same motor but have a lighter cone, raising the Fs to 35Hz and increasing the sensitivity.
That is the case, increased sensitivity. If you look at the graphs the 2243 is 5dB's down at lower frequencies.
But if you look closely (fig.3) for the 2242 at 30Hz you have attenuat. 11dB's and for (fig.4) the 2243@30Hz (same frequency) you have -8dB's. I don't know if that is what you are expressing in your comment?!
Fig.5, fig.6 for the cone displacement or excursion, showing the maximum excursion in the ~30's for the 2242 and in the -20's for the 2243, this one having lower excursion (at 30Hz 11.5mm for 2242 and 5.0mm< for 2243) for a similar volume designed (170L) box and considering different FB as above.

Fig.5 JBL 2242H, VB = 170.0 L, FB = 39.5 Hz excursion
Fig.6 JBL 2243H, VB = 170.0 L, FB = 32.0 Hz excursion
 

Attachments

  • Fig.5 JBL 2242H, VB = 170.0 L, FB = 39.5 Hz, le 0 dB correspond à 95.4 dB2.83Vm. cone displaceme.jpg
    Fig.5 JBL 2242H, VB = 170.0 L, FB = 39.5 Hz, le 0 dB correspond à 95.4 dB2.83Vm. cone displaceme.jpg
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  • Fig.6 JBL 2243H, VB = 170.0 L, FB = 32.0 Hz, le 0 dB correspond à 95.5 dB2.83Vm. displacement (2.jpg
    Fig.6 JBL 2243H, VB = 170.0 L, FB = 32.0 Hz, le 0 dB correspond à 95.5 dB2.83Vm. displacement (2.jpg
    104.3 KB · Views: 64
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What trade-off do you get with large boxes? My Win ISD simulations show that the Group Delay times increases with larger boxes. How important is group delay, do I need to take it into consideration? I want fast, dry bass...

I'll need 2 or 3 bass ports per box. Anyone has a source with nice looking ones?

And I'll need to recess the drivers and put some grill cloth in front of them. I'll hopefully be a daddy soon, and I'd hate to get curious childrens fingers putting holes in the dust cap :eek:

I must scan the internet to try and find some pictures. Still haven't got a clue what the boxes should look like...

Thanks for the router tip. Time to go shopping :)
 
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