Wild Burro Betsy OB Build

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I'm taking my first crack at an open baffle speaker design build. I've built a couple of speakers in the past, mostly *boring* 2-way ported low-efficency towers and such -- but have been recently bitten by the low-wattage SET amp bug and cross-overless, boxless speaker bug...

I stumbled on the Wild Burro Betsy, and they are intriguing to say the least.

I figured for my first build, I'd stick with Paul's design and experiment from there (hey -- I can always use the OBs for shelves later if I don't like them ;)--).

So for my build I've decided on some stain grade laminated pine panels that I found at Lowe's. Sadly, no access to a wood shop anymore...

The total Lowe's trip was $136 -- the wood was a bit expensive but it will look nice when done, I think.

The main panel with the speaker is 12" x 48". The outside panels are also 12" x 48". The inside panels are 16" x 48".

I did splurge for the 48" piano hinges.

I made some good progress today -- using a rotozip, I cut out the 7 3/8" hole for the driver 26" up on the panels.

For finishing, I am keeping it simple, using clear shellac.

Front panels after cutting out the driver holes:
An externally hosted image should be here but it was not working when we last tested it.


First coat of shellac on the fronts:
An externally hosted image should be here but it was not working when we last tested it.


I'm very excited about this build, and if all that I have read about the Betsy drivers, OB midrange and soundstage detail are true, I have a lot to look forward to for these!

I'll update this post as I complete the build and will take measurements in my listening room.

I still have to decide on a complete audio chain. Right now I am leaning towards the following:

Mac Mini --> USB Halide Design Dac HD --> Bottlehead SET or Decware Super Zen Triode --> DIY Betsy OBs.

Would love your thoughts/suggestions on the build.
 
I think they look fantastic! I have the Burro Betsy and Betsy K.... You're in for a real treat.
Great baffle choice. I've built a pair of piano hinged, winged baffles and it is my favorite of all the different ones I've built over the years. So much flexibility. You'll observe quickly how baffle width impacts bass and changes the imaging.

Your audio chain plans look great. The Bottlehead Stereomour 2A3 would be enough power. The Decware is great too. (I owned one for years)
I'm using a Class D amplifier with mine and the sound is stunning. It's all a matter of different flavors.
Great job and way to jump in!
 
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Hi Mike --

I changed up the baffle size because that is what Lowe's had for wood. Paul said that a few inches here or there won't matter and bigger should be better, right? I'm not sure -- we will have to see.

Dan

Paul is correct. You'll discover quickly that placement in the room and wing positioning will affect the sound WAY more than a few inches in baffle dimension variance.
 
Paul is correct. You'll discover quickly that placement in the room and wing positioning will affect the sound WAY more than a few inches in baffle dimension variance.

Very cool --

That is what I was thinking as well. I may experiment with some absorption materials as well.

I found some rolls of adhesive-backed cork at target this morning, which I will laminate to the back of the baffles.

I may also experiment with some of the adhesive-backed duct liner that is made from recycled cotton:
Recycled Cotton Acoustical Liner ? HVAC ? Multipurpose

Now my Betsys just need to get here!!

Off to put another coat of shellac on the backs and attach the hinges. I'll post some pics later this evening.
 
Made some good progress on the build:

There are a LOT of screws needed on those piano hinges...

An externally hosted image should be here but it was not working when we last tested it.


And set up in their listening location --
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I did find out that there is a slight setback in that Paul had sold out of the regular betsy drivers right as I was paying for them -- so I am going to try with a pair of BestyKs with some series resistance.

I did see this thread --
http://www.diyaudio.com/forums/wild...0-off-take-betsy-where-shes-never-been-8.html

Which suggests a 25-ohm series resistor, but that seems a bit high to me...
 
An externally hosted image should be here but it was not working when we last tested it.


I'm not sure why that other pic is broken. I think the came out nice as well. I don't see why you couldn't use the Pergo floorboards -- or two pieces laminated with the faces out. I think the inside is just chipboard anyways...

And here is my parts list so far:

Drivers: Wild Burro Betsy-k - $110 + $20 shipping

Baffles (All from Lowe's) - $136.00:
3/4x12x48 Stain Grade Pine x4: 47.76
3/4x16x48 Stain Grade Pine x2: 25.94
48" Silver Piano Hinge x 4: 39.92
Qt Clear Shellac Zinsser: 13.78
Old t-shirt to apply Shellac was free
All hardware came with the hinges.

Total coats of Shellac was 3x on the front, 2x on the back, there is still about 25% of the quart left.

Total: $266.00

Still need:
Cat 6e cables -- going to make 12' cables based on @cervelorider's recommendations (thanks for all your help!), and most likely use the HRT streamer II ($147) as my dac:
http://www.amazon.com/HRT-Music-Str...8&qid=1356907566&sr=8-1&keywords=hrt+streamer

I think I have the cat6e around the house so I can just use that for now. May have a bit more expenses if I damp the rears of the baffles with some of the recycled cotton, plus I need hardware for the speakers.
 
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-- so I am going to try with a pair of BestyKs with some series resistance.

Which suggests a 25-ohm series resistor, but that seems a bit high to me...

This is a better choice IME than using a high Q driver unless a low XO point is used since in the driver's mass controlled BW it's better damped.

FWIW, based on published specs, only 5.7 ohms is required to raise Qts to the Betsy's, but I typically use a cheap 25 ohm pot [+ a series resistor if it's not enough] to dial in what's needed, then insert a non-inductive power resistor or RLC [aka BSC] filter.

GM
 
True from a purely technical POV and why my personal builds would fail to meet the rigid standards of today's 'design by computer sim' crowd, but we have no way to know how each person perceives sound since we all hear the same and yet not so much, so no choice but to fall back on any well proven theory when trying to help folks achieve a good starting point for them to find their own "best overall performance" that provides the "most musically satisfying presentation".

GM
 
danvprod: Since you are just at your starting point, well proven theory suggests that a high quality solid state amplifier has much lower distortion and control over a driver. You have "no choice but to fall back on well proven theory to choose a starting point" Pay no attention to all the people that have raved about the Bottleheads or Decware Zens. "we have no way to know how each person perceives sound since we all hear the same and yet not so much."
By all means, choose the lowest distortion, best spec'ed amplifier out there. It will be a good starting point. ;)
 
It may well sound better with the "wing", since baffle step will be reduced acoustically because of that, but the rear radiation will have a small amount of "cavity effect", which will color the reflected sound a bit. It seems that the best way to reduce baffle step is with active EQ, or at least passive electronic EQ. OB's need to be at least 3 ft. away from any walls, to work properly, because of the psycho-acoustic effects of the delays involved. Putting it another way, less than about 6mS delay of the rear radiation doesn't have a good psycho-acoustic effect.
 
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