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Open Baffle Epiphany!

cubdog said:
So many questions. I'm definitely going to try some OBs but will move slowly. I'm very ignorant when it comes to DIY and speaker design in general.

Assuming I use an Eminence 15in Alpha, can someone explain the basic difference between a folding baffle like the Betsy design, a plain flat baffle, or an H frame. I would prefer a flat baffle design from an aesthetic point of view but I don't understand what limitations there are to this approach. I do understand ever design decision is a compromise to some extent.

Thanks for the help.

cubdog
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The baffle size dictates where the rolloff of the low end response starts to drop off. The larger the baffle, the lower the frequency will be where the rolloff begins. The use of H frames and folded designs are to create large apparent baffles to the woofer, without visually large baffles like a 4x8 sheet of plywood sitting your living room. :)
 
There was a method to the madness. For the rest of my life, any audio project I take on will seem relatively reasonable. 15 cu ft towers with dual 15" lambdas flanking unity horns? Yes, perfectly reasonable.
 
rogerfederer said:
folding wings are used when you are trying to maximize your baffle area and (i think) prevent the back wave from cancelling the front. ie, it is a strategy to maximize your LF; not needed when you use a bass assist like the eminence alpha

poultry and others can weigh in re H-frame vs. flat baffle for the woofer
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My flat baffle double Alphas are 19" wide X 49" high. My calculations for this size were based on the pieces of MDF I had left over in the garage. :D But if you get too much wider aesthetics can go down hill fast. Most wives can deal with tall better than wide.

Home Depot sells a two pack of 3/4 MDF 2 ft X 4 ft ( measures 49" high ) for $17. Now that would yield two ready made flat baffles but 24" is getting pretty wide. HD will rip them down free and the height still looks good. Personally I don't feel I gain any more usable bass with wider baffles when augmenting with pro woofers.

I like the Alpha H-frames vs single Alpha's on a flat baffle but the difference is not huge. The H-frames are said to extend a little lower but I was happy with either. You could easily build the Alpha's in flat baffle first and then later build the H-frames around them without having to cut a new baffle.

But the double Alphas on flat baffles are about as much fun as I've had lately with my pants on. Each Alpha wired together gives 4 ohms which extracts every bit of what the plate amp has to offer and gives room enveloping bass.

Believe it or not 2 Alphas mounted on the same baffle will increase the baffle's rigidity. I have never heard any resonance or noise from baffles. I think if you listen at insane levels you'll get resonance. 90% of what I listen to is jazz and Dire Straits is as raunchy as it gets for me.

In my case OB's are all about low level extraction of detail ( I want to hear the spit in Mile's trumpet which SET amps deliver with FR drivers ), too die for imaging, articulate natural bass ( redefines conventional bass ) and that intoxicating ambient sound ( aka "alive-ness") that you can't get from box speakers due to enclosure coloration.
 
When I'm ready to get started I'll start my own thread but here is where I'm at now. If I say anything stupid call me out. I'm in way over my head.

I'm leaning towards the double Alpha approach. Full range driver to be determined. Tweeter? :scratch2:

I have Bel Canto mono blocks to drive the Alphas. Lot's of options up top.

I have a bunch of rough cut oak planks that I plan to have planed. I think they would make great looking baffles. They measure 59 x 5.5 x 1 inches and I have a lot of these. I'll want, and need, help with a design before I have someone fabricate the baffles. I'm compiling ideas for the future build.

My biggest concern is the crossover or lack there of. I'm going to have to rely on a lot of you guys for guidance. I'm not anywhere ready to get started however. I need to sell of some things to raise money and free up some work space. I did sell some speakers this past weekend so I've officially started the process.

cubdog
 
re crossovers, i'm very curious about the miniDSP approach. hoping to hear more about how to use them, cost, flexibililty, etc.
 
Vintage analog electronic crossovers like this 3 way Pioneer SF-850 and some of the Sony's are highly regarded and feature a gentle 12 db slope. They can be found on ebay but they aren't cheap.



Pioneer_SF-850_4.jpg
 
Here is my thread in the DIY forum about my OB's and MiniDSP.

http://www.audiokarma.org/forums/showthread.php?t=569977

In a nutshell. The MiniDSP can make your speakers do whatever you want. Almost too easy to get a flat response or to boost the top or low end to your liking.

The sound quality is quite good. I am sold while using a digital source. When playing vinyl I may be noticing the analogue aura "someone breathing on the back of your neck" feel may disappear. I haven't had enough experience using it yet to positively identify this.

build the OB's, get a MiniDSP, and if you want you can later build passive XO's or analogue active. But the MiniDSP is an invaluable tool in getting them set up correctly.
 
Here is an example of a fairly decent, but economical driver for OB use.

http://www.parts-express.com/goldwood-gw-8003-8-8-full-range-driver-w-whizzer--290-379

This Goldwood, as a single driver is...umm...modest in quality and you'd have to watch excursion. Stacked, it actually gets decent. Two drivers a side, better but 3 or 4 starts to really cook. On about a 20" size, it packs a really decent punch on the bottom end. Out of a quite a few 8" drivers I've played with, it probably does the best on the bottom end out of them all. Good enough I'd suggest many wouldn't want for more. But if you do, it does good enough to skip a 12 or 15" and go right to a separate boxed sub you may already have around.

It only goes high enough to do just ok, despite how they rate it. I'd suggest a rear firing augmenting tweeter if you want much above about 14K. Some little horn or something. Look at efficiency and keep it high enough to meet or exceed the mains, and you've got a pretty fair 1.5 way setup.

For the money and trouble to make it, you'd be hard pressed to not feel pretty good about it!

EV3
 
Two more questions. How does one determine the best size full range drivers to pair with the Eminence or other bass drivers?
Also how much difference in bass output would there be using 12 in. rather than 15 in bass drivers? Thanks.

cubdog
 
cubdog said:
So am I. From the little I've read they've piqued my interest.

cubdog
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I did a ton of research into best options for a crossover for my project: bass augmentation for my Aiko horns.
The MiniDSP seemed to be the best option based on the fact that it's inexpensive and has so much flexibility.
My plan is to use it as a low pass filter to the bucket subs I'm building and let the Aikos run full range.
However, I like the fact that I can use it as a high-pass on the Aikos too, to see which way sounds best.
For the money, it sure lets you answer a lot of questions about what will work best quickly and easily...or so I read. I just got it yesterday and haven't been able to play around yet.
 
Where did you get your DSP from Wes? I really know nothing about these. Do I need one for each speakers or just one for both?

cubdog
 
wes,
can you link to the model you bought and, as time allows, explain how the programming works?
very curious about this option
 
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