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Accidental MLTL Technique
Accidental MLTL Technique
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Old 14th March 2013, 10:37 PM   #31
xrk971 is online now xrk971  United States
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Accidental MLTL Technique
You can do almost anything in Mcad explorer that the full version does except save your work. Things like password protection sections, making self-contained worksheets for people who do not have Mcad installed are not available in the free "Explorer" version.
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Old 14th March 2013, 10:51 PM   #32
Bjohannesen is offline Bjohannesen  Denmark
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Default MJK for Dummies

Hi

MJK´s models will educate you in how different T/S, shapes, volume, damping and driver offset influence the output.

First time i looked at the models, I gave up and made my first "Hide Away sub" from what i had read was good practise. However, the result was better than expected with a deep and clean bass. I then used several evenings to get hold of MJK´s software and found out that the tuning frequency of my sub cabinet was lower than I had expected. This was a result of the shape of the cabinet.

I then made another Hide Away sub, and finally changed the driver. Please look at the file attached.

Well, when i had got the hang of it, i wrote this articel as a MJK for dummies:

http://www.coolcat.dk/bjoern/QWforDummies.pdf

MJK´s models will predict any shape of box, I always use "sections corner".

Damping is a very important parameter, which is modelled by MJK. By having a gentle decrease of the bass response, you can avoid boomy bass caused by room gain.

Finally: The fee you pay to Martin J. King is a very small amount.

Have fun !
Attached Files
File Type: pdf HideAway Sub SCANSPEAK.pdf (810.4 KB, 255 views)
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Old 14th March 2013, 11:00 PM   #33
xrk971 is online now xrk971  United States
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Accidental MLTL Technique
Thanks for making the tutorial Bjorn. I forgot that I had used that at one point to understand how to play with the MJK worksheets. Excellent resource that was very helpful to me.
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Old 14th March 2013, 11:02 PM   #34
Scottmoose is offline Scottmoose  United Kingdom
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Amen. $25 is not a vast sum, nor are the sheets especially difficult to work with if you spend a while familiarising yourself with Martin's nomenclature and the basic layout. The critical points to remember are:

1/ Martin has done the mathematics so essentially you only need very basic (as in the ability to count) to use them as far as this side of things is concerned.

2/ They don't design a box for you. They model the behaviour of a driver / cabinet enclosure that you put into them.
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Old 14th March 2013, 11:09 PM   #35
rjbond3rd is offline rjbond3rd
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The dummy a.k.a. brute force method worked for me:

0. Get licensed and join the Yahoo group, but don't post yet.

1. Read all MJK's papers, and forum posts. Now freak out, because it's all over your head. But you press on because you have developed an unhealthy obsession.

2. Open the MLTL worksheet. Do. Not. Change. The. Values. Leave them as-is.

3. Scroll down -- this is what forces the graphs to re-calculate.

4. Focus on a single value, e.g. Fs, Qts, Vas, whatever, and increase / decrease it. Scroll down and observe the changes it makes in the upper-most frequency response graph (forget about the other graphs -- you're not ready).

5. Repeat for other values. You're not over-thinking, you're just screwing around with variables, la la la la la.

6. Keep playing for a month (or a year). Slowly, you get a feel for the values, just by shaping the upper-most frequency response curve.

7. Eventually you zero in on an ideal geometry, volume and tuning. Now scroll further down and see why your beautiful frequency response is now horrible, what?!

8. Play with boundaries, BSC, etc. and get a good in-room response.

9. Re-read the papers and voila, you are connecting the dots, if only very slowly. Not that it's even necessary, because MJK mastered the math and you just have to master a simple worksheet, c'mon!

P.S. It may go easier if you master WinISD (or similar box design program) before attempting MJK.
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Old 14th March 2013, 11:34 PM   #36
Bob Brines is offline Bob Brines  United States
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There are two ways to do things; the right way and any other way. If you absolutely refuse to pay for someone else's work, then use HornResp. Yes, it is free. Yes it will give you the right answer. Yes you have to do some visual extrapolating because HornResp does not include stuffing.

Yes, I always model a new driver in a BR box program. That provides a starting point for entry into the MJK worksheets. The final result may well be quite different because of the Q and Vas of any given driver. Your method will produce and OK answer in most cases and a correct answer by pure accident. Your choice of pipe length is extremely important to getting the right answer, and there is no ROT for that.

Bob
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Old 15th March 2013, 12:03 AM   #37
xrk971 is online now xrk971  United States
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Accidental MLTL Technique
Bob Brines,
I think you are absolutely right on all points. Luck so far has played an important part. But what I agree with you most about is that it will produce an OK design. The pipe length is critical and perhaps sim in HR will let one narrow down on that. For folks who don't use HR yet, but are comfortable with a BR program like WinISD this is one way for them to imagine the possibilities of what the cabinet looks like as a MLTL. One way to cheat is to use a length similar to a known MLTL for a known driver size.
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Old 15th March 2013, 12:29 AM   #38
Bob Brines is offline Bob Brines  United States
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OK, yea, that will work sometime, most of the time if using the same driver. Several years ago, I gave a talk on quarter-wave generators at the Lone Star Audio Fest. I stressed the fact that once you get outside a golden ration BR, standing waves becomes a problem. One of the attendees was a builder of medium range ($3000-5000) boutique speakers. For him, the light came of as to why he had unexplained wiggles in his FR plots. Now he does all of his modeling with quarter-wave software.

Now, you can stuff the bejesus out of any speaker you can make the standing waves go away. What you end up with is an infinite baffle, which is exactly what a traditional TL is when stuffed to remove the second impedance peak.

Bob
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Old 15th March 2013, 01:42 AM   #39
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Accidental MLTL Technique
Stuffing the bejeezus also kills all the efficiency you may have had to get the bass augmentation. There is also the nautilus spiral like B&W did without stuffing to get infinite baffle. I guess one could make the Cornu spiral start out large and taper down to get an infinite TL wall mount speaker with no stuffing.
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Old 15th March 2013, 01:49 AM   #40
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Quote:
Originally Posted by Bjohannesen View Post
Hi

MJK´s models will educate you in how different T/S, shapes, volume, damping and driver offset influence the output.

First time i looked at the models, I gave up and made my first "Hide Away sub" from what i had read was good practise. However, the result was better than expected with a deep and clean bass. I then used several evenings to get hold of MJK´s software and found out that the tuning frequency of my sub cabinet was lower than I had expected. This was a result of the shape of the cabinet.

I then made another Hide Away sub, and finally changed the driver. Please look at the file attached.

Well, when i had got the hang of it, i wrote this articel as a MJK for dummies:

http://www.coolcat.dk/bjoern/QWforDummies.pdf

MJK´s models will predict any shape of box, I always use "sections corner".

Damping is a very important parameter, which is modelled by MJK. By having a gentle decrease of the bass response, you can avoid boomy bass caused by room gain.

Finally: The fee you pay to Martin J. King is a very small amount.

Have fun !
I like the stealth sub woofer. Nice design that gets you down into 20 hz territory. Very cool.
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