Best $100 I've spent on audio gear

OK, I have been muckin around today. I went to the shop and wrote a program for the baffle. I cut 5 sheets of thin plywood and then glued them together with the hydraulic press. I jacked the speakers from a crappy boxed 3 way that my father in law had in his attic.

Re-wired the speakers and added the melamine. I now have to trim the melamine and hinge it on. Pretty rough but it's something I can start with. Haven't heard a note yet, I'll be back...

http://www.aboutus.org/Special/image/full/DSC02693.JPG

http://www.aboutus.org/Special/image/full/DSC02694.JPG

http://www.aboutus.org/Special/image/thumb/DSC02695.JPG

The OB DIY'ers use the "golden ratio" to determine size of baffle and driver placement based on speaker specs. It's very scientific and way over my head. Just any speaker won't work in OB as it has to be a full range driver.

In order for a speaker to sound decent in OB I do know that it has to have a high Qts ( over .5 is considered good ). My Betsys sound good because their Qts is around .70

I am not knowledgeable enough to design an OB. I can only use someone else's design that has been proven successful.

I don't think you baffles are large enough though.

Way kewl!!

I'm interested to hear what the final product turns out like.

Have you thought about what kind of crossover your going to use?

Hmmmm, more science required. I was looking for a fast and cheap way to hear this damn thing. Nothing good comes THAT easy I suppose. Looks like no crossover Geoff...

Poultry, have you seen any guys suspend their baffles from the ceiling? I was thinking about how cool that would be...

Quote:

---

Originally Posted by poppachubby

Hmmmm, more science required. I was looking for a fast and cheap way to hear this damn thing. Nothing good comes THAT easy I suppose. Looks like no crossover Geoff...

Poultry, have you seen any guys suspend their baffles from the ceiling? I was thinking about how cool that would be...

---

I wouldn't hook up the speaker with the drivers in parallel if you value your amp. In series would be fine, but the total resistance could be quite substantial depending on the ratings of the drivers. In any case I would do some research on a simple crossover. The DIY crowd should have a few ideas for you.

Oh no, sorry Geoff, what I meant was "no crossover" as in, I wasn't going to pursue it any further. I have to go watch a movie but I had a simple crossover from another set. I'll post a pic tommorrow...

My next project may be the Betsy/Boomer combo in the same baffle which would include my two current 8 inch Betsy drivers paired with two 15 inch bass drivers also known as a bass augmenter ( not a sub ). The full range 8 " drivers would be powered by my regular amp and the bass augmenters would get it's power from a small Parts Express amp. This design stands 40 inches and is about 20 inches wide and has no wings. The sides are only a couple of inches deep.

OB's often avoid crossovers as they reduce efficiency and can suck the life out of your sound. When crossovers are used they tend to be very simple. Check out the coax Silver Iris at Hawthorne Audio.

OB's are not new they're older than dirt. Most of the old console radios from the 30's and 40's sounded good because they had full range speakers and open back cabinets. Many of the old juke boxes used huge full rangers with open backs as well. Edison's first phonographs were open baffle horns. It could be argued that speakers were originally designed to be played in "free air" and then sometime later got stuffed into boxes.

If you take a small transistor radio and place it inside an empty speaker cabinet it will sound muffled and not nearly as clear as when you play it in "free air". A great OB will make the music sound "live." Folks love to brag about how their speakers produce pin point imaging. Has anyone ever attended a live concert and heard pin point imaging? It may be nice but it's not like "live" sound.

The great thing about OB's is that the sound from the rear of the speaker is allowed to join the sound from the front. There is where I believe the magic lies and what makes for the huge "live" soundstage. Some folks may prefer the box sound but it's cheap to build an OB and decide if the magic is right for you.

The one problem I'm finding in OB's is that there aren't many choices in drivers. Companies don't make them as the demand is small compared to drivers designed for regular enclosures.

There is a $30,000 amp playing on YouTube known as the GM-70. Guess what speakers it's driving? A pair of OB's in simple flat plywood baffles. To me that says something.

I haven't seen any OB's suspended from the ceiling but I have seen stop sign OB's

I am trying rebuild my Accoustat Spectra2200s. I will need to repair what may be wiring short between transformer and the left panel (suspicious black smuge the lower back of the left panel. WAF approval factor also requests that I find replacement covers (socks) for them to remediate the grunge factor. Any ideas? Mother Hubbard.

The covers can be cleaned.