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Isobaric cab?

spwath

spwath

Sep 5, 2016
157
41
#1
So im building a bass cab, and have 2 JBL 2226h's on hand, and plan on getting a midrange driver.

I want it to be as small as possible, and I was looking, it seems like Isobaric is a good way to do that.
However, acording to winISD it will bring the sensitivity from 97db/w to 94db/w. But, since its 2 8 ohm woofers, does that make it a 4 ohm cab? So then I get twice the power into it?

Also, im not sure quite how isobaric works. Would the drivers be facing each other or not? And in winISD it give a volume of the cab, does that include the space between woofers?
 
#2
Wow, Isobaric! There's a term I haven't heard since 1992 during the car audio boom! I built my fair share of them back in the day, usually with the drivers facing each other but they don't have to be like that. They can be in a loaded chamber, but face to face was always easier. And yes, you do lose sensitivity with isobaric as the two drivers are essentially now one driver with a really heavy cone and double magnets. And yes it would be 4 ohm.

Sounds like a neat experiment, but I have to think there's a reason cabinet makers don't offer isobaric anymore.
 
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#3
mmbongo said:
Wow, Isobaric! There's a term I haven't heard since 1992 during the car audio boom! I built my fair share of them back in the day, usually with the drivers facing each other but they don't have to be like that. They can be in a loaded chamber, but face to face was always easier. And yes, you do lose sensitivity with isobaric as the two drivers are essentially now one driver with a really heavy cone and double magnets. And yes it would be 4 ohm.

Sounds like a neat experiment, but I have to think there's a reason cabinet makers don't offer isobaric anymore.
Click to expand...
I think the main reason is cost, and that modern woofers can perform well without it.
But I already have these two drivers.

I assume with face to face, ill have to reverse wire one?
 
#5
Here's a picture inside of Orange's isobaric SP212, the only isobaric bass cabinet I've ever known to ever have gone to production.
orange_cab.jpg


I tried one at a local music store and was not impressed with the tone at all. Very little definition.
If you have two of those drivers, build two cabinets. Use one for rehearsal and stack two for gigs. Someone here has to have a better cabinet design for those JBLs.
 
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#6
abarson said:
Here's a picture inside of Orange's isobaric SP212, the only isobaric bass cabinet I've ever known to ever have gone to production.
orange_cab.jpg


I tried one at a local music store and was not impressed with the tone at all. Very little definition.
If you have two of those drivers, build two cabinets. Use one for rehearsal and stack two for gigs. Someone here has to have a better cabinet design for those JBLs.
Click to expand...
Looking, I would need a pretty large cabinet to get good bass extension.
And I think the problem with the Orange was the drivers, or tiny volume (liters, not db) of it. Or the amp.
According to winISD i could get a pretty good and compact cab with an isobaric design.
 
#8
spwath said:
So do you think I should go for it?
Would bring the cabinet from 150l to 75l. Have the size.
Click to expand...

Why not? But I'm not building it.

Figure it this way…if you don't like it you're only out some time, plywood, screws and glue. The speakers can always be repurposed.

I like the SP212's sound. But not everybody does. And I also like the sound of a ported 15. So take where I'm coming from into consideration before you listen to any of my opinions about cabs. :laugh:
 
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#9
40Hz said:
Why not? But I'm not building it.

Figure it this way…if you don't like it you're only out some time, plywood, screws and glue. The speakers can always be repurposed.

I like the SP212's sound. But not everybody does. And I also like the sound of a ported 15. So take where I'm coming from into consideration before you listen to any of my opinions about cabs. :laugh:
Click to expand...
Well im new to the whole bass world.
I guess ill try building an isobaric cab. Will be a fun experiment.
 
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#16
Won't have much frequency range, maybe up to 200Hz?
And would loose the punch of front loaded speakers.
If you use other drivers for mids, there will be phasing issues too, same as using folded horn designs.

But then it might work, I too have considered a isobarack cabinet design for PA subs.
I did a DIY bass combo project and used 6.5" quad drivers (125 watts each) front loaded in a smallish cabinet lightweight cab made from FormPly,
a light resin plywood compound, it works very well.

Gumtown's DIY 500 watt quad 6.5" bass combo
 
#17
gumtown said:
Won't have much frequency range, maybe up to 200Hz?
And would loose the punch of front loaded speakers.
If you use other drivers for mids, there will be phasing issues too, same as using folded horn designs.

But then it might work, I too have considered a isobarack cabinet design for PA subs.
I did a DIY bass combo project and used 6.5" quad drivers (125 watts each) front loaded in a smallish cabinet lightweight cab made from FormPly,
a light resin plywood compound, it works very well.

Gumtown's DIY 500 watt quad 6.5" bass combo
Click to expand...
WinISD says it would go up to like 1khrz.

I might just try.

Now I need to find a good 4 ohm mid
 
#19
so yeah, as has been outlined - isobaric loading in a design is a great way to increase bass and extension in any given design. It's drawback is that, like you said - it reduces your sensitivity by 3 db, basically halving the power input into it. Of course, you're also basically doubling your power handling anyways, so if you have the amp to spare what are you really harming?

As far as I know the volume doesn't include the space between the drivers, and if you wire them in parallel they'll be 4 ohms.
you seem to know what you're up to and what you're expecting, and you get the drawbacks involved. You also seem cool with the 4 ohm mid. If you're cool with lugging the thing around, and have a good design, I want to see this thing get finished.

Also, it should be noted, that if you're doing the drivers front to front or back to back, you'd need to wire them in reverse polarity to work together (so that they move inward and outward at the same time and don't damage each other or negate the effects of the design), if they're back to front, wiring them in "proper" polarity is good.
 
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#20
sensitivity is half, power handling is doubled. basically puts you at same place. with a smaller box and double the cost and weight.

a single jbl would do fine in 85liters
and keep the higher sensitivity and be good for power handling
Doing common reflex cabinet at 40hz

likewise 75liters would be a large box
for a single kappalite 3012lf
same sensitivity, less weight more
power handling. definitely needs a mid
 
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