I am a beginner to speaker building, but I have been researching designs for about a year now and am ready to start building.
So, I took a look at the Wild Burrow Betsy speakers. I want to utilize a full range driver, since being familiar with electrical engineering I cant help but feel crossovers are more trouble than they can be worth with a simple project, and just another variable in the design that can go wrong.
I want relatively balanced sound, but I do like my bass. If I use the Betsy in a ported enclosure, it ends up being huge (55" x 34" x21") but that doesn't phase me. I also get (according to design calculators) an F3 of 18 hz, which is plenty low. The only problem is the parameters of the Betsy:
Re 5.9 ohms
Fs 49.630Hz
Sd 22.966
BL 4.166
Qms 4.567
Qes .945
Qts .783
Spl 92.4db
Vas 86.387L
Mms 8.916g
Is it wise using a driver in a ported system with such a high Qts? Is there some factor that I am not considering with my driver choice that could lead to disaster? Im just looking for some guidance here before I commit.
(I also modeled the Betsy K, but I don' like what happened to the bass extension)
So, I took a look at the Wild Burrow Betsy speakers. I want to utilize a full range driver, since being familiar with electrical engineering I cant help but feel crossovers are more trouble than they can be worth with a simple project, and just another variable in the design that can go wrong.
I want relatively balanced sound, but I do like my bass. If I use the Betsy in a ported enclosure, it ends up being huge (55" x 34" x21") but that doesn't phase me. I also get (according to design calculators) an F3 of 18 hz, which is plenty low. The only problem is the parameters of the Betsy:
Re 5.9 ohms
Fs 49.630Hz
Sd 22.966
BL 4.166
Qms 4.567
Qes .945
Qts .783
Spl 92.4db
Vas 86.387L
Mms 8.916g
Is it wise using a driver in a ported system with such a high Qts? Is there some factor that I am not considering with my driver choice that could lead to disaster? Im just looking for some guidance here before I commit.
(I also modeled the Betsy K, but I don' like what happened to the bass extension)
What design calculator did you use?
I can't see using a driver with a Qt over .7 in a vented box. It would take a pretty big sealed box to keep it from booming badly. Betsy is meant for open baffle use. Should be pretty nice on OB, though.
If you want a box speaker you really need to use Betsy-K. The box still winds up being pretty big, but you should be able to get a quality 40 Hz. Search the archives for an MLTL design for Betsy-K, that's probably what I'd build given the choice.
You won't find a lot of full-rangers that will dig below 40 Hz, 18 is a pipe dream IMO. That's sub-woofer territory. A full-range + sub (aka FAST around here) might be a better target design.
Happy hunting!
Bill
I can't see using a driver with a Qt over .7 in a vented box. It would take a pretty big sealed box to keep it from booming badly. Betsy is meant for open baffle use. Should be pretty nice on OB, though.
If you want a box speaker you really need to use Betsy-K. The box still winds up being pretty big, but you should be able to get a quality 40 Hz. Search the archives for an MLTL design for Betsy-K, that's probably what I'd build given the choice.
You won't find a lot of full-rangers that will dig below 40 Hz, 18 is a pipe dream IMO. That's sub-woofer territory. A full-range + sub (aka FAST around here) might be a better target design.
Happy hunting!
Bill
I used the MH audio calculators. mh-audio.nl
So how does one go about the design of a MLTL? Are there any preliminary calculations for the port or do you really just build a TL and stick a port on it and tune? Could i build a mass loaded BIB?
So how does one go about the design of a MLTL? Are there any preliminary calculations for the port or do you really just build a TL and stick a port on it and tune? Could i build a mass loaded BIB?
You should revisit your simulation. You're not going to get F3 @ 18 Hz out of any design with either Betsy. You're not going to get F3 18Hz with any 8 inch driver. A reasonable design for Betsy or BetsyK will be F3 ~45 - 50Hz w/ F10 ~40Hz. The driver doesn't have much excursion so you can't expect extremely low FR.
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Dumbledog: I own both the Betsy and the Betsy K. Both are WELL worth the price of admission. I have the Betsy K in a MLTL with a 4 inch diameter one inch port. This happened to be a cabinet I built two years ago for a different driver, but with a "baffle adapter", it now fits. 
Perhaps the cabinet dimensions are not optimal, but it sounds decent.
I put the regular Betsy in a resonant style, Auditorium 23 Rondo clone style enclosure. I also use one in a very large open baffle. There are threads on both in the Wild Burro section.
My personal opinion is that one can't go wrong with a Betsy in a large open baffle.
![IMGDEAD]](/community/proxy.php?image=http%3A%2F%2F%5BIMGDEAD%5Dhttps%3A%2F%2Fi1098.photobucket.com%2Falbums%2Fg372%2Fsandersonphoto%2FIMG_1841_zps2ce355e9.jpg%5B%2FIMGDEAD%5D&hash=883a6959f4d154fb4648cb2b846e6a9f)
Perhaps the cabinet dimensions are not optimal, but it sounds decent.I put the regular Betsy in a resonant style, Auditorium 23 Rondo clone style enclosure. I also use one in a very large open baffle. There are threads on both in the Wild Burro section.
My personal opinion is that one can't go wrong with a Betsy in a large open baffle.
Hi Dumbledog
This driver would do fine in a quarter wave, like an XL version of my TABAQ. Dont expect very deep bass, however, as already mentioned in this thread.
MJK´s models are very good to predict the result of a given design and also helps you calculating the baffle step circuit. Yes, you still might need some filters even with a full range.
Give me a couple of days to simulate a suggested MLTL design for this driver.
Hi from
Bjorn
This driver would do fine in a quarter wave, like an XL version of my TABAQ. Dont expect very deep bass, however, as already mentioned in this thread.
MJK´s models are very good to predict the result of a given design and also helps you calculating the baffle step circuit. Yes, you still might need some filters even with a full range.
Give me a couple of days to simulate a suggested MLTL design for this driver.
Hi from
Bjorn
Having had them in a cabinet and open baffle, I would encourage you to consider starting with just the Betsy on a very large baffle, if WAF isn't a factor.
Not only will you be surprised by their bass, but you'll be hooked by the lack of box coloration and openness. The trifold, piano hinged baffles, like the one on the burro website are quite nice for experimenting. It allows one to see how much the sonics are affected by baffle width.
Is there any way to determine appropriate baffle size? I know the bigger the better where bass is concerned, and wings help too, but how do the depth/angle/wing width affect bass? Shoul the wings be perpendicular to the baffle? Slanted out? Slanted in towards the center? I know the hinges are used to change the tuning, but how do the wing design affect standing waves between them? So many variables.....
It's not like the hinged OBs are a lot of effort or expense to experiment with. Almost all of the wood is still usable if you don't like the results. Build to Pauls recommendations and then try different arrangments. There's no real way to predict what you will like in your arrangement.
Yes, but one ideally needs a response plot of the room's acoustics to figure out how small a baffle one can get away with, hence the 'BIB' [bigger is better] rule-of-thumb.
Flat baffles have the same eigenmodes structure as a pair of parallel surfaces, ergo angling one changes it to a decaying one same as is done in theater/recording studio, etc. design to minimize 'slap echo'.
Whether slanted forward or backward is mostly dependent on room acoustics around the speaker
In my limited experimenting with hinged 'wings' long ago with only a tone test record, SLM and mine and others ears to guide me, multiple hinged panels are required unless the room is quite small and square to rectangular, but don't recall anyone posting/publishing any results for such designs, so assume you'll be on your own if you want to go to a more refined level of OB/room matching.
GM
You might want to check this thread, looks like a good sim and build for mltl w Betsy has been done.
http://www.diyaudio.com/forums/wild-burro-audio/182745-betsyk-ml-tl-tqwt.html
http://www.diyaudio.com/forums/wild-burro-audio/182745-betsyk-ml-tl-tqwt.html
MLTQWT Betsyk
Wow. Like the smooth response. Thanks for running that sim. I've been trying to figure out how to use MJK's mathcad models but I must be doing something wrong.
I used the calculators on mhaudio to design a ML TQWT for the Betsy k. The dimensions were more than reasonable with the tuning frequency set to 40 hz, which put the f3 at about 30 hz (according to the calc) This seems to be very similar to the plot on the sim. I'll post a sketch-up model shortly. But does that tuning seem reasonable?
Wow. Like the smooth response. Thanks for running that sim. I've been trying to figure out how to use MJK's mathcad models but I must be doing something wrong.
I used the calculators on mhaudio to design a ML TQWT for the Betsy k. The dimensions were more than reasonable with the tuning frequency set to 40 hz, which put the f3 at about 30 hz (according to the calc) This seems to be very similar to the plot on the sim. I'll post a sketch-up model shortly. But does that tuning seem reasonable?
Hi Dumbledog,
tuning to 40 or 35 Hz does not make a big difference. I just tried to see if it worked with my "agressive" tuning. And it did.
I was not able to get any useful sims with the other Betsy - i dont know why.
About MJK´s software: it took me "some" time to learn it, and when i finally got it right (with useful help from Martin) i wrote this paper:
http://www.coolcat.dk/bjoern/QWforDummies.pdf
Hi from
Bjorn
tuning to 40 or 35 Hz does not make a big difference. I just tried to see if it worked with my "agressive" tuning. And it did.
I was not able to get any useful sims with the other Betsy - i dont know why.
About MJK´s software: it took me "some" time to learn it, and when i finally got it right (with useful help from Martin) i wrote this paper:
http://www.coolcat.dk/bjoern/QWforDummies.pdf
Hi from
Bjorn
I have actually read your paper before. Nicely done.
My problem comes with trying to use the mathcad worksheets. Im sure I'm doing this wrong but I have been saving the pdf files off of MJK's site and then opening them in mathcad. I have yet to figure out how to properly open them in mathcad so I can edit the input data and such. Once I have downloaded the pdf, what do you do with it in mathcad?
My problem comes with trying to use the mathcad worksheets. Im sure I'm doing this wrong but I have been saving the pdf files off of MJK's site and then opening them in mathcad. I have yet to figure out how to properly open them in mathcad so I can edit the input data and such. Once I have downloaded the pdf, what do you do with it in mathcad?
You have to buy the mathcad worksheets from mjk, the pdf is not the same. Even if you transcribed everything from pdf over to mathcad manually it won't work as there are hidden formulas. You can download a basic test worksheet from mjk's website to get the feel of it and to work on a horn or transmission line with a default driver, but you cannot change the driver properties. This trial worksheet is very useful for learning how to use the software.
Okay then. That's something I should look into. I didn't realize the difference. But reading the site now I think I was just misunderstanding what was going on.
Bjorn,
On the sim, what's the width of the tl? Depth? What information on the sim would allow me to calculate the other dimensions?
Also, is the driver placed at the side but near the end of the tl? Or the offset ratio recommended by MJK?
Bjorn,
On the sim, what's the width of the tl? Depth? What information on the sim would allow me to calculate the other dimensions?
Also, is the driver placed at the side but near the end of the tl? Or the offset ratio recommended by MJK?
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