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-   -   Isobaric - less then $20 (http://www.diyaudio.com/forums/subwoofers/203345-isobaric-less-then-20-a.html)

ODougbo 29th December 2011 12:18 AM

Isobaric - less then $20
 
2 Attachment(s)
Some may be familiar with the design, although I used cardboard tubes instead of a slot port.

Also ran this in WinISD and Perfect Box; the results were similar so went with a 1cf box and dual ports 16 long [the next box I may go back to a slot port]

The woofers are 6 Factory Buyout, I bought 4 for $8 each.

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=299-114

They modeled okay; it does have a bit of a shark tail contour, 3db increase at 25hz. Ive been adding a little extra at the bottom for such a long time I dont think I would like anything else.

This Isobaric box appears to have some power, a few more easy steps and Ill do a final glue up. I like to clamp and check the tuning before final assembly. I was pleasantly surprised, the tuning and the response was as expected (and some 25hz bass).

Not a bad little woofer, the surround is light rubber; I wish it had more than 4 holes [they say never drill a basket].

The laminate rings are pretty easy, it only took three rings; i.e. the woofers are 2- apart.

*I also added a 10" PR ($18) to the last order, I wouldn't mind trying that with the next build.

NEO Dan 29th December 2011 12:32 AM

Where do you put them all, do you put bows on them and "gift" them away?

ODougbo 29th December 2011 01:18 AM

Sometimes I give them away (no bow) OR for trade. Sounds like you would like to have one NEO.

I'd go for the MCM 8” versions; you'll be doing back flips in the back yard if you hear one of them.

NEO Dan 29th December 2011 01:42 AM

Although I do have the drivers on the shelf I'm not a small sub person. I look at your subs and think about the >$30 sheet of MDF, if I'm buying a sheet of material I might as well get all the box/performance out of it I can.

trumpiper 29th December 2011 02:03 AM

My first post ever on diy. Your isobaric inspires me to get to a project I've had on the shelf for a few years. I have 8 vifa 8" woffers from a speaker that ended up not working. I want to build a double isobaric with 4 per side and mate that up with a 4" vifa mid and a vifa tweeter.Crossover will be simple to start as that is a very weak area for me.This will take time but I"ve been sitting on these drivers for a few years so what's a while longer? Thanks for the kick in the pants.

ODougbo 29th December 2011 02:21 AM

If I was to describe the sound, it’s a slam, bubble and/or chug. I have a MCM 8” Iso in the shop, it reaches out and grabs you.

The two in the HT I moved up on 12” metal stands; should have done that long ago, it was a big improvement (by adding detail in the bass).

I find them remarkable.

8 working Vifa woofers? What’s the model #?

NEO Dan 29th December 2011 02:30 AM

What are you using to power them, plate amps?

ODougbo 29th December 2011 03:38 AM

I don't use plate amps (do have one on the bench) I've been using, Rotel, 120 watt stereo amps, e.g. RB 980BX. I had an Adcom 60watt stereo amp powering one for a long time, it had a very nice sound.

I'll try this 6-1/2” Iso in shop, HT and maybe even the truck cab; that 25hz would sound great in a cab.

Ty_Bower 29th December 2011 03:40 AM

Great photos, it makes me want to build one too. I've think you've got $200 worth of clamps on top of $16 worth of drivers. Hee hee.

ODougbo 29th December 2011 03:48 AM

Clamps are not that bad $$ ~ HD has a nice selection, buy a couple a year, they build up fast.

Hey weights work well too, 25lb – 40lb dumbbells work great for “clamping”.


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