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Old 18th December 2012, 04:14 PM   #11
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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.....
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Old 19th December 2012, 01:44 PM   #12
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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.


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Originally Posted by Dumbledog View Post
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.....
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Old 19th December 2012, 02:25 PM   #13
GM is offline GM  United States
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Quote:
Originally Posted by Dumbledog View Post
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.....
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[s], hence the need for hinges if not in an acoustically large space for the desired BW.

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
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Old 19th December 2012, 06:43 PM   #14
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You might want to check this thread, looks like a good sim and build for mltl w Betsy has been done.
BetsyK ML-TL and TQWT
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Old 28th December 2012, 11:10 AM   #15
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Default BetsyK in a TABAQ-like enclosure

Hi

I have done some simulation with BetsyK in a design approach like my TABAQ. The design is very simple, and the simulation looks very promising.

I hope this can be used as inspiration

Hi from
Bjorn
Attached Files
File Type: pdf BetsyK simulation TABAQ style.pdf (198.0 KB, 76 views)
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Old 28th December 2012, 11:24 AM   #16
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Default 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?
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Old 28th December 2012, 11:41 AM   #17
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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
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Old 28th December 2012, 11:54 AM   #18
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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?
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Old 28th December 2012, 12:37 PM   #19
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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.
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Old 28th December 2012, 04:21 PM   #20
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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?
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