Isobaric - less then $20

[NEO Dan]

You willing to try something different for the new year?

[ODougbo]

NEO, that’s looks intriguing, and yes I would like to build something like that but just to stay on the isobaric topic; just a couple of thoughts and maybe a new build.

DH,

Had not thought about series vs. parallel (a question on the older modeling program) and that the outer driver will hit its excursion limits well before the inner driver.

Putting two driver’s clamshell in a tunnel, I will do that next!

The next build that I’m considering is clamshell (using the smaller woofers) in a keystone shape box, with the 10” PR mounted on the back.

I ran the idea in WinISD, and got a few ideas. I’m not sure what the max grams is for the PR. but a 1.5cf box with a 10” PR with 50 grams looks pretty level.

Q. what’s the max grams for a inexpensive PR?

Dayton Audio SD270-PR 10" Passive Radiator 295-494

[NEO Dan]

Ok well here you go then, it's 1/2" material.

[NEO Dan]

Almost forgot...

[ODougbo]

But Dan....where's the bow?
Thanks Dan, I have no idea where you all come up with this stuff.
I will send you a 6 layer tunnel if you ever want to try the MCM Iso box, then all you’ll need is 2 pieces 17" x 19" (sides) and about 84” of 10" rips.

Thank you again for the design, this is for the 6 ½”, 299-114 woofer?

[This Iso box is not too bad, as long as it is not played too loud]

[NEO Dan]

Your welcome Doug,
I figured I'd give you a taste of something different instead of whining. Although the 299-114 is not a strong driver this should be an interesting contrast in an A/B comparison. I would rate this as a ~30Hz box and it should be a good deal more efficient, no shark tale on this one though.

[ODougbo]

1. Build Neo's box, 1/2" MDF?

2. Fix the other box, modify it to clamshell, cut/put the 10" PR on the side (plug the port holes).

I did a little reading on PRs, looks like 50grams is not that bad.

[ODougbo]

I went with #2 since the supply stores are closed today and I couldn't buy material.

It is about 2x as powerful (maybe more), hard to believe these are $8 woofers.

The crossover issue is gone, i.e. no more ringing.

This is not much of a box at this point, but there are no rattles. As far as weights I guess at 50grams (a USA quarter is 5.6grams) so I used 10 fender washers.

Okay, it won’t break glass, but somewhat amazing for what it is.

box size 8-7/8" (rips) x 17-1/2" x 12-7/8".

[trumpiper]

@ODougbo, sorry for the delay in responce. Te vifa woofers are PO21W-20-8. I might have mied up a letter or two but youget the drift,also I have 4 jbl ME120HE 12" woffers I got at a surplus store very cheap. Three in the box one not. I think these were used in the S5500. I was thinking of playing aroun with a version of that speaker using a pair of altec 511 horns and drivers I have sitting around. We'll see. Interesting boxes here.

[revboden]

good to see ya trying something new.

btw, it's "less than 20$" not "less then".

or you could be using Middle english... are you in the 1300s, are rouges chasing you through a brush while you type?



later,
revb.