The WIBAQ: TABAQ Design with Betsy K

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This started on this thread here discussing the validity of a massive ported speaker design utilizing the Wild Burro Audio Betsy speaker. It eventually evolved into exploring different designs, with the final design being chosen as a MLTL similar in design to the TABAQ, first built by Bjohannesen.

Bjohannesen kindly simulated the Betsy K in a TABAQ-like enclosure (albeit much much bigger) with very positive results. Attached are the preliminary Sketchup model of the speaker. Material is 3/4" MDF/plywood, and the dimensions are internal. There is a close-up of the port dimensions. The simulation is also attached.

So, any feedback? These will be built eventually and will serve as my first home-built stereo speaker and will take the place of my White Van Special Acoustic Response 707 speakers (They were free...). Positive critiques are welcome.


EDIT: Please see page 11 for a link to an article that details the entire project and provides much of the information provided in this thread. The article is on Instructables and includes cutting plans, schematics, and links. Please check it out
 

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Founder of XSA-Labs
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Thanks for sharing the design. Wow it is big! I think some of the dimensions can be rounded off, like the depth is 16 and 13/64 which is 16.203, perhaps 16 inches even or 16 and 1/4 inches would probably work fine. The port dimension is more critical so keep that. Looking forward to your build and listening impressions. The Betsy is a pretty popular driver because they are sold out as of now and it won't be another 2 months until in stock again... How is the scale of this speaker doing in the WAF department? :)
 
The WAF is not an issue. Im 18. But my mother is something to be worried about. She even dislikes the surround speakers we have in out family room, saying that a 5 by 4 inch speaker is "too distracting" :confused:

These are going to end up in my room (not a bad room for listening, since it is 12x18 although I share with my brother) or in the basement. My brother is not an audiophile like I am but he still thinks big speakers are cool looking. So all good there!;)
 
Happy Newyear!

I like the name of the construction :)

A small down rounding as suggested by xrk971 should be OK.

I simulated alsi with a volume about 230 cm smaller, but you will get the most out of the driver as suggested where WAF has not been a parameter. I only used T/S parameters :)

The bigger volume the more bass which is controlled by stuffing to avoid / reduce boom bass caused by room contribution.

Hi from
Bjorn
 
That enclosure should work well.

You may find that the top end will be a little bright, if so the addition of a small inductor (say, 1 millihenry) and a resistor, paralleled with each other, and the combination of the two in series with the driver will tame it down. Post back when you get that far, I'm sure you can get some advice on that around here!
 
Founder of XSA-Labs
Joined 2012
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That enclosure should work well.

You may find that the top end will be a little bright, if so the addition of a small inductor (say, 1 millihenry) and a resistor, paralleled with each other, and the combination of the two in series with the driver will tame it down. Post back when you get that far, I'm sure you can get some advice on that around here!

You are describing a BSC circuit which Bjorn normally provides recommendations for from the sim. Hopefully, the Betsy will provide a lot of bass and may not be needed.
 
If I wanted to move the driver closer to the closed end so the center of the driver was closer to seated-ear-level, could I do so without detrimentally affecting the sound? I know the current placement of the driver 1/3 of the way down the line is to remove unwanted resonances, but if the driver were placed 1/5 of the way down the line (9 inches from the closed end) would that be a bad idea? I kinda want to preserve the flatness of the response, though I am willing to sacrifice a little bit of it if the imaging was better with the higher driver.
 
WIBAQ - Driver 9" from the top

Hi Dumbledog

I would say the result is in fact slightly better when the driver is 9" from the top compared to the 15" driver offset.

By the way, it is the same with the TABAQ: Driver can be placed 5 cm higher up, and in the folded version the driver can be placed in the middle of the baffle.

I have enclosed SPL simulations.

Hi from
Bjorn
 

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Thanks for posting those new sims Bjorn. Nice to see the bass be unaffected and the response smooth out even more. Its incredible how smooth that is, and the driver is at a better height to boot. Thanks so much!

Below are the updated Sketchup models of the speaker. The material is still 3/4" thick, and dimensions are internal as they were before. The depth has been rounded off to 16.25" instead of the ridiculous decimal it was before. The driver is now positioned 9" from the closed end, and the image was given a wood grain color and the visible ends of the material black color just for kicks. This is the final design, just need to get ahold of some Betsy K's (out of stock for 6-8 weeks) and other parts and pieces.
 

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A cut plan for Home Depot:

1- Horizontal Rip 46 1/2" (or do 1/2" on one side first and then flip to do the othere side so you have nice edges)
2- 2x vertical rip 17 3/4" (or remove 1/2" first for nice edges)
3- 3x vertical rip 11"

Take the 11" boards to the cross saw

1- Cut first one to 15 3/8 (This is the front)
2- Second 11" board: cut a 16 1/4" piece (top)
3- From same board: cut a 17" piece (bottom)
4- From the same board: cut a 3 1/4" piece (port)

You still have about 25" or material left for braces, etc...

The best thing is to do all the same dimension cuts at the same time, so a little bit of planning is required.

(Am I reading the dimensions correctly?)

(You will need to watch/supervise the person doing the cuts and measurements to make sure they are doing it right. Talk nicely to them and tell them this is for a critical project :))
 
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His dimensions were all internal dimensions since the plywood size is nominal. I will be using 3/4". Here are the dimensions for each piece that I came up with. Do they match up with your cuts glt?

Front: 11" x 43 3/8"
Back: 11" x 46 1/2"
Side: 17 3/4" x 46 1/2"
Top: 11" x 16 1/4"
Bottom: 11" x 17"
Baffle: 11" x 3 1/4"
 
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