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pjanda1 3rd December 2009 07:57 PM

Enclosure designs for Burro Speakers
I've got about twelve more minutes (before I need to head to a big band gig), so I'll make this quick. However, I have bunch of enclosure designs for my drivers that should be on my site. Here is a quick overview. I'll try to fill in pics and specs later on.

Betsy: The OB options are fairly straight forward, by herself or with a woofer. You can use her in a sealed box, but I'm not sure why you'd choose to do so. One unique option that came up in discussion is a small aperiodic box. It might be the smallest way to get a Burro speaker into your room, and with it, more sensitivity, dynamics and image size than you normally get in a bookshelf.

BetsyK: Sealed and vented options abound, but here are some more interesting things:

GM posted a 10:1 TQWT that looks great. If you can tolerate a wide cabinet with a decent sized footprint, it promises great performance and a very simple build. Specs to come.

Skinny quasi TQWT/TL: I designed a box for my brother in law after seeing the Zu Essence and liking the size. Mine is about 12x13x44". It is a very easy build with some advantages over a regular BR. I'm listening to a pair right now. I think this cabinet should be very, very popular. My in-laws are thrilled.

MooseBVR: ScottMoose was kind enough to simulate one of his double mouth BVR's for the BetsyK. I'll send you the dims if you want. I plan to build a pair. I meant to this fall, but the Skinny TQWT project got in the way.

BIB: My cabinets stayed in MN when I moved west. However, I can give you the specs I used (skinnier than the calculator produces). They are great fun.

I do plan to do a better, and more complete list than this thread. But, I wanted to get something fun up before folks get home from work!

Wild Burro Audio Labs - DIY Full Range Speakers

pjanda1 4th December 2009 02:45 PM

Here is 'Zilla's Betsy + Boomer kit for Betsy. The BetsyK can also be used in helper woofer applications for a little more sensitivity, but a little less flexibility.

Here is a link to GM's TQWT for the BetsyK.

I followed the top set of specs here for the BIB's I had the BetsyK's in. Maybe not ideal, but they worked well for me!

Wild Burro Audio Labs - DIY Full Range Speakers

Godzilla 4th December 2009 09:19 PM

Hi Paul, I spent three hours listening to music thru the Betsy/Boomers last night. Thought i'd watch some tv around 11pm before bed but when i came upstairs i saw it was 12:58am!!!

Open Baffle Speaker - Betsy and Boomer Open Baffle Speaker Kit

I put up some new pictures if anyone is interested in the Boomer idea to enhance their Betsy's.

The Betsy also sounds very good in a sealed or aperiodic cabinet sitting atop a pair of H-frames.

If anyone is interested in the Betsy/Boomer speaker kit let me know.


rjbond3rd 5th December 2009 02:28 AM

Congrats on the vendor forum! It's great to have things gathered in one place.

Just out of curiosity, were the Betsy BiB's skinnier because of an MJK sim, or for some other reason? I'm interested because I'm comparing the BiB calc to MJK's BiB worksheet, and I'm just finishing up a set of BiB's this very weekend (for a listening party next weekend).

Regarding the (very excellent) Betsy OB design, as you know I built it with my wife, but what's new is that I swapped out my two little tube amps for an SS (Cambridge Audio Azur 340A, $350) and the bass is so much tighter.

So that design only gets better with SS (at least that's my experience!)

pjanda1 5th December 2009 03:04 AM

Godzilla: maybe a Betsy +Boomer thread is in order? I have the power to split threads here, but feel free to start one with a pretty pic!

RJbond: I built my BIB's cabs early on for another pair of drivers. ScottMoose spec'd those before GM came up with the formula from which all the "modern" BIB designs (and the calculator/spreadsheet) are derived. It may have been in the first hundred posts of the BIB thread! It was designed to be a smaller than ideal, so lower tuning (notice how long it is) helps avoid a hump in the midbass. The thing I liked least about those cabinets was the driver height. I frequently contemplated turning them upside down. Since I had gain to spare, I also thought about a K-slot, which would have made them the largest iBIBK (I think). But alas, I never got it done.

My wife is very tolerant, but one pair of giant BIB's was enough. The BetsyK specs pretty close to the drivers the cabs were originally built for. I tossed the BetsyK's in, and that pair lives in those cabinets to this day.

In retrospect, I may have had them overdamped for many peoples taste. I really did enjoy the LF extension. These TL's go deeper than I thought they would, but it is tough to compete with 12 cu. ft. When I built the BIB's, I was really looking for a pair of cabinets this size (for the drivers I had at the time). But, I didn't have the ability to simulate them, and I didn't want to build a basic bass reflex. The BIB thread exploded, and I didn't look back until we moved West.

I'm really enjoying these cabinets. I think nearly anyone could incorporate them into their room. As I mentioned I delivered a pair to my brother and sister in law. She is a picky decorator, and is tolerating them well despite my sub-par woodworking skills. I (nor they) are running any BSC, and with the boxes close to the boundaries, I'm pretty happy. They are probably a little shelved down in the bass, but I like a slightly forward midrange. Brings the girls closer. If folks drag them out into the room, a few DB of BSC wouldn't hurt, but keep in mind that they do have a couple db more bass gain than a comparably sized bass reflex or ML-TL.

I do have visions of giant cabinets. The MooseBVR was a big reason I parted with the BIB's. The design for the BetsyK's is only about 2/3 the volume of the BIB's I had. I knew I probably wouldn't build a pair as long as the BIB's were in the house. But, I'm also contemplating a OB/helper woofer setup. 'Zilla's kit looks great, but I already have too many amps. I'll be curious to see the Pass B4 PCB's. . .

Wild Burro Audio Labs - DIY Full Range Speakers

pjanda1 5th December 2009 04:54 AM

RJ bond, I got distracted thinking about the BIB's. Does your tube amp have 4 ohm taps? If you find the SS amp tighter with the OB's, you probably prefer a little more damping. I sure don't find my tube amp sloppy down low, but then neither my tube amp or my SS are typical! My tube amp has tighter bass than the chip amp, unless I switch the small amount of feedback off. I do suspect that these OPT's are more substantial than is typical of "little" Chinese amps.

As regards info consolidation on this forum: it certainly can be a plus. On the other hand, I hope that you folks don't restrict discussion of my speakers to my little area! There will always be fewer potential customers lurking in these parts than on the main fullrange board.

Wild Burro Audio Labs - DIY Full Range Speakers

pjanda1 5th December 2009 05:20 PM

I received an email asking me to turn GM's TQWT specs into actual dimensions. Basically, the box needs to be (internally) 248 sq. inches at the top, and 24.8 sq. inches at the bottom and 44" high. The top is closed, the bottom is open, the driver is as close to the top as you can stand. GM recommends 30" wide (external, at the top), so assuming .75" material, that means the cabinet would be 10.25" deep (again, external). And of course, that means the cabinet will be 3" wide at the bottom. When you add the top in, the cabinet becomes 44.75" high externally, and you'd want some sort of stand to get the terminus off the ground. Stuff to .25 lb/ft per cubic foot: i.e. tease about 12 oz out to fill the cabinet.

That is a very wide an shallow interpretation. You could, of course, work those dimensions out any way you like. But, as you get narrower and deeper you may find you want a little BSC. And if that taper is a little too strange or creates too large a footprint for you, keep bugging me to draw out my TQWT.

Wild Burro Audio Labs - DIY Full Range Speakers

rjbond3rd 5th December 2009 05:46 PM

Pardon my ignorance, but this tapers in two dimensions like a Metronome? Or am I mis-reading? Would this look like an inverted pyramid with the "tip" cut off?

Perhaps it could be folded like Bob Brines? FTA-2000

Might help to lower the driver height. Wow, 30" wide sounds big even by GM's standards :) But it's the sound that matters. Big speakers are fine by me if the bass is crystal clear.

pjanda1 5th December 2009 06:17 PM

It only tapers in one dimension, the depth stays constant. It is a basic TL, or in GM's terms, (which I like) a TQWT. So, an inverted triangle with the tip cut off, if you look at it in two dimensions.

It isn't really practical to fold a 10:1. If you did, it would be very short. You could make a very unusual bookshelf though!

A more traditional 1.4:1 works much better. The lesser taper makes for a longer length and a smaller footprint. This is the whole idea behind my little TL/TQWT! I need to get some specs up.

30" is wide, probably too wide for many people. But it will obviate the need for BSC. I'd be tempted to to a little narrower (24" wide?), toss it against a wall and take my chances.

Wild Burro Audio Labs - DIY Full Range Speakers

Poultrygeist 21st January 2010 01:12 AM

I'm thinking a Betsy would work great in the new Zen Open Baffle design.....Great bass with no sub or bass speakers needed... driven by a flea amp... and it looks much smaller than the folding wing design.

I don't have the link but it's on the Decware site. How bout a DIY Wild Burro clone kit with precut flats for us poor folks with no woodworking skills?

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