isobaric bass cabinet

[Super Turbo Deluxe Custom]

Anybody ever made one, owned one, played one, seen one?  The Orange Bass cabinets got me thinking about it.

At the moment I have time, a 2x10 cabinet, no 10" speakers, (2) 12" speakers that won't fit in it side by side but will fit front to back.  I'm doing limited research, learning the ins and outs of frequency response and it's relationship to plenum space.  I'm gonna do them both front facing (that's what she said) so they'll both be in-phase.  The one in front will be sealed and the 2nd one will be ported. 

 

[jimh]

Interesting....I've seen isobarik hifi speakers, but never bass or guitar cabs. I'll be interested to see how this one pans out.

 

[MUYFUE]

please explain the concept...Isobaric?

 

[AndyG]

Isobaric Isobaric (most commonly “push-pull”)

An enclosure that uses two woofers mounted face to face, one wired reverse polarity.  This alignment effectively cuts the vas in half.  The general rule of thumb for an isobaric enclosure is twice the woofers, twice the power, and half the box size3.

Pros: Very small enclosures, increased power handling, driver non-linearities canceled out (lower distortion).

Cons: Very low efficiency, due to the small size of the recommended enclosures for our woofers an isobaric alignment is not practical.

 

[MUYFUE]

I get it now. So...where is the 'front'? Is the edge facing toward the Mic/audience?

 

[Super Turbo Deluxe Custom]

Isobaric Isobaric (most commonly “push-pull”)

An enclosure that uses two woofers mounted face to face, one wired reverse polarity.  

There's several ways, they don't have to be face to face.  They can be front to back, even back to back.  If it's worth a darn, it will be 1 of 2 cabs being used, so the cons shouldn't be there as the other cab will pick up the slack.

I'm going to do it similar to this one.  This one is ported, and it appears to be a shelf port.  I'll probably do the front port with circular ports.  As you can see, the plenum between the two speakers is sealed, this is where the push/pull action occurs.

 

[AndyG]

Isobaric Isobaric (most commonly “push-pull”)

An enclosure that uses two woofers mounted face to face, one wired reverse polarity.  

There's several ways, they don't have to be face to face.  They can be front to back, even back to back.  If it's worth a darn, it will be 1 of 2 cabs being used, so the cons shouldn't be there as the other cab will pick up the slack.

I'm going to do it similar to this one.  This one is ported, and it appears to be a shelf port.  I'll probably do the front port with circular ports.  As you can see, the plenum between the two speakers is sealed, this is where the push/pull action occurs.

I should have added that the "pro" and "con" were not my words ... it was a copy and paste from a subwoofer design page.

I've never personally used an isobaric cab ... so I'd be curious to hear the results as well!

 

[Super Turbo Deluxe Custom]

I should have added that the "pro" and "con" were not my words ... it was a copy and paste from a subwoofer design page.

Oh I know.  I read that somewhere too. There has to be a con, otherwise everyone would be using them.

 

[mayfly]

I think that the biggest con would be lack of efficiency.  It's gotta be loud to be rock and roll donchaknow.

 

[Super Turbo Deluxe Custom]

I think that the biggest con would be lack of efficiency.  It's gotta be loud to be rock and roll donchaknow.

Like I said, I'll be using 2 cabs.

 

[ocguy106]

Not sure what the freq response is for a Bass but I would guess having the woofers in a ported enclosure like that you would be most effective under 80hz

Edit: Unless of course that front speaker is not sealed off (bandpass)

 

[Super Turbo Deluxe Custom]

I'm modeling mine after the Orange cabinets I've seen.  One speaker is ported, the other is sealed.  Sealed I use loosely.  Although the space between the two speakers is sealed, they both move the same direction.  The phase relationship is dependent on which way the speakers are in relation to each other.  So even though it's sealed, there is no pressure change in the plenum.  As one pushes, the other pulls.  Inefficient, yes.  But, this will be (2) 8 ohm speakers, making the cabinet a total 4 ohm.  It will be paired with my ported 4x10, which is also 4 ohm.  My head runs at 2 ohms.

Honestly, I doubt anything built in my garage could do a better job than something a guy in a white lab coat with a 6 figure salary designed.  But, a fun little project.  If it works well, yeah!  If not, I'll mark it off my list of things not to try again.

 

[MUYFUE]

Amen! only way to know is to go for it.
:rock-on:

 

[Super Turbo Deluxe Custom]

Well, here's a little progress report.  I haven't begun the inside portion yet where the isobaric magic takes place, but here is some of what you will see.


The 210 cab w/out speakers.

The disassembling of the 210 cab.

Removal of some bracing, insulation, and sealed portion of the cab.

The (unpainted) face of the cab.  The speaker hole is offset to leave room for porting holes to the right.

Unfinished face with speaker grill.

 

[bpmorton777]

that looks like a fun project!!! I hope it sounds they way you want it when it's done :headbang:

Brian

 

[Super Turbo Deluxe Custom]

All of the "pieces" are done.  Now comes the details.  I have to get some foam from the fabric store and a trip to Lowe's or Home Depot is in order for some rubber cement and spray paint.

Here's the guts.  The space between the front of this speaker and the back of the visible one will be sealed.  The back of this speaker is ported and it exits to the right.  The round ports will be mounted on the face along with the other speaker.  The ports set me back $0.29 each.  I got three but think I'll only use two.

 

[mayfly]

very cool!

you know,  it always seems that its the bass players that are the most open to new ideas

 

[Super Turbo Deluxe Custom]

very cool!

you know,  it always seems that its the bass players that are the most open to new ideas

I don't know what you heard, but I don't swing that way.  lol

 

[Super Turbo Deluxe Custom]

Okay, it's finished.

My goals were to get a small cab with a high wattage and low ohm value, that could either be a small stand alone cab or a nice extension cab.  Also, I wanted to spend little or no money.  Check, check, and check.  What I ended up with is a 2x12, 4 ohm, 800w cab.  Other than some flat black spray paint, rubber cement, foam, and 3 plastic ports, I didn't have to buy anything.  It was all stuff I had laying around.  I think I could have spent a little more effort making the face look nicer.  Either with MDF and carpet, or attempting a grain fill on the plywood or using spray-on bedliner.  

What does it sound like?  Very thumpy.  Think P-Bass instead of J-Bass.  I spent an hour rediscovering what all of the knobs on my amp do.  I was able to get a great Pink Floyd "Money" sound out of it.  I'm gonna gig with it tomorrow as an extension cab.

Oh, and this thing moves some air.

 

[MUYFUE]

Very cool! Congrats on the build!
One last touch would be like a custom badge or something...
"STD Custom Cabs" HAHA! eeew.  :headbang1: