Enclosure designs for Burro Speakers

[pjanda1]

All the dimensions work together as a system. So, you've got to use a set of specs that works together rather than mixing and matching or averaging. The specs I used predate GM's formula. Theoretically, those from the formula (which the excel sheet uses) will give more gain in the enclosures bandwidth (the bass). In my room, I suspect that would have meant for too much bass. Bigger rooms might be happier with the bigger dimensions.

The important thing though, is that the CSA (cross sectional area), length and Zdriver (distance between the top of the line and the center of the speaker) must all be matched. You can vary the aspect ratio, though, to get to the depth you want. The width times the depth = the CSA, so if you alter the depth, you must then alter the width too. GM choose and aspect ratio that will yield the most ideal expansion rate, but altering it will make much less of a difference than messing with other parameters. And, don't forget that you must not confuse internal and external dimensions!

Finally, while you need to get the specs right overall, in most ways, a half inch here or there won't make much of a difference. I would work to get the Z-driver as close to dead-on as you can, though.

Paul
Wild Burro Audio Labs - DIY Full Range Speakers

[glt]

Originally Posted by Mush

I've decided on building the regular BIB for my Betsy-k pair. Your BIB is 78"x20"x25". Using the excel sheet from Outdoor Speakers | Rock Garden Speakers | Garden Speakers | Patio Speakers | In Wall Speakers | Ceiling Speakers - ZillaAudio.com, I get 67.5"x21.5"x29.8". This is a big difference. Is this because the BIB design allows for a lot of flexibility? I'd really to make them 24" deep since that's exactly half the width of a 4'x8' sheet of plywood. Are BIB's all that sensitive to exact dimensions?
Thanks again.

I will be following your project with interest. My pair of Betsy K are still in their boxes and also wanted to build the regular BIB.

[derwhalfisch]

Paul, have you seen/performed simulations of the BVR? I'm very, very close to building it but can't figure out how to model it in Hornresp (I may actually have figured it out but the result looks terrible)

[Mush]

Hi glt,

My idea was to cheat a little on the dimensions and rip a 4x8 sheet to around 28" and 20" widths for the sides and baffle/backs. Unfortunately, my BIB boxes will have to wait a bit. 4 sheets of plywood, saws, biscuit cutter, and clamps are not in my budget right now. Ever since the university closed down the woodshop, building things has gotten much more demanding.

[pjanda1]

derwhalfisch,

I haven't. The dimensions are from ScottMoose, the double mouth BVR guru. I don't know how you are doing it, but to my knowledge, you can't sim one with horn response (though you could do a single mouth that didn't rely on quarter wave action). I trust his sims far more than anything I could come up with! (As I sit a little frustrated that my tapped horn sub is tuned a bit differently than my horn response work had told me it would be).

Paul
Wild Burro Audio Labs - DIY Full Range Speakers

[pjanda1]

Mush,

BIBs do take a few bucks of wood. They can be done pretty inexpensively though. You can probably get AB grade or Arauco that is plenty good enough for around $25 a sheet. Pawnshops tend to have decent circular saws for $25. You don't need biscuits. A couple of screws in combination with clamps will get the job done. Enough cabinet clamps would cost a fortune. I use 2x4s and threaded rods (5/8") on big boxes. They are a little slower to set up, but can generate great force and are dirt cheap.

Paul
Wild Burro Audio Labs - DIY Full Range Speakers

[glt]

I like Wild Burro's approach to building cabinets :-)
I was thinking ripping the wood at Home Depot (making sure they measure right) and even some crosscuts (they charge like .50 per cut you just have to watch them). The just glue and wood screws.

Waiting for some free time and for someone to come up with good measurements:-)

[pjanda1]

I had the lumberyard make the big cuts for the aforementioned tapped horns. I don't have a vehicle that can haul 4x8 sheets. I usually pay someone to do it, but decide this would be easier. For two subs, I needed a 4x8 sheet quartered, not precisely, and then two panels crosscut into 10" strips. I told him that I'd rather have them all the same size (precise) than exactly 10" (accurate). He cut nearly all of them, then a co-worker came over and showed him how to set a stop to do them all identically. They ended up about +/- 3/16. Boy would construction have been easier and the final speaker nicer had they been more precise. But it was easy. And the PL adhesive will fill those gaps. No leaking, even in a high compression tapped horn!

Especially for complex cabinets, I love to use a brad nail gun. If you buy something reconditioned or from a pawn shop, you can get a gun and compressor for under $100. I know it isn't furniture grade, but it is a really quick and easy way to build a sturdy box. Don't credit me for this construction method. It all comes from Bill Fitzmaurice. Though I haven't built any of his designs, I did purchase the plans to one to see exactly how he claims to be able to build such complex cabinets with modest tools.

Paul
Wild Burro Audio Labs - DIY Full Range Speakers

[pjanda1]

FWIW, I would have been better off doing those 10" strips with a guide in my circular saw.

Paul
Wild Burro Audio Labs - DIY Full Range Speakers

[derwhalfisch]

lookee what I built

They are as rough as GUTS

First significant build so I made some mistakes... learnt a lot though so no big problem ;P