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Vented box for bass guitar design - HELP!
Vented box for bass guitar design - HELP!
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Old 3rd November 2017, 01:15 AM   #51
JMFahey is offline JMFahey  Argentina
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I guess itīs too late for that
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Design/make/service musical stuff in Buenos Aires, Argentina, since 1969.
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Old 6th November 2017, 06:40 PM   #52
ChurritoTierno is offline ChurritoTierno  Paraguay
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Quote:
Originally Posted by chris661 View Post
Now that we've managed to scare OP away, shall we get back on with designing a vented box for a bass guitar speaker?

Chris
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Old 7th November 2017, 08:34 PM   #53
PB2 is offline PB2  United States
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To the OP, have you tried putting the driver into a free simulator such as Unibox?
I would consider tuning to the low 40s since that is the lowest note on a 4 string bass, or
do you play a 5 or 6 string? You can adjust the amplitude response at Fb by adjusting
the size of the box to avoid boom.

You could use an adjustable port to try different tunings.

I'd probably build it as two 2X10 boxes that you could stack for portability.
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Old 8th November 2017, 03:30 AM   #54
freddi is offline freddi  United States
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Vented box for bass guitar design - HELP!
sim has bump - in real life may not look the same - 110 liters for two 10 seems "big"

https://i.imgur.com/1Xx3lx8.jpg
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Old 8th November 2017, 05:55 AM   #55
freddi is offline freddi  United States
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Vented box for bass guitar design - HELP!
also - for one driver per cabinet (using MMJ's approximation of a particular K-coupler with his constricted transflex model)

Click the image to open in full size.
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Old 9th November 2017, 10:15 PM   #56
Gnobuddy is offline Gnobuddy  Canada
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Quote:
Originally Posted by Ron E View Post
Please take your silly urinating contest somewhere offline.
I understand the sentiment, but please read back through the thread to see which side of the table all the urine came from. It may take two to tango, but it only one to urinate!

Quote:
Originally Posted by Ron E View Post
insisting on calling it 'total mechanical damping' confuses it with Qms for most people who know something about T/S
I left the thread to avoid urine splatter, before I had a chance to continue to talk about why it actually helps the understanding to see the problem for what it is: a single damped mechanical system. Seeing it this way may be new to some, but it is almost certainly the way Thiele/Small themselves saw it, and I find it actually helps one to understand the various results that Thiele/Small calculated from their mathematical model. Give me a minute, and I'll give some examples.

Quick recap: a speaker is a mass on a spring, with damping from the mechanical floppy bits. A mechanical damped harmonic oscillator.

Connect the voice coil to an amp with zero (or a reasonably low) output impedance, and you get additional mechanical damping from the current induced in the voice coil. In turn, the total mechanical Q drops, from the value Qms, towards the value Qts.

Now forget the T/S equations and think of the mass-on-a-spring with damping. What happens if you increase damping? Yup, lower Q. Exactly the same result you get from the Thiele/Small model. Perfect agreement between the damped mechanical oscillator approach, and the Thiele/Small electrical filter math.

(Incidentally, adding more damping also causes the resonant frequency to drop a hair, usually too little to matter. This also happens in both T/S and the purely mechanical models.)

There's more: mount the speaker in a sealed box. Thiele/Small says that the resonance frequency rises, and so does the total mechanical Q.

And that's exactly the same conclusion you get when you look at the damped harmonic oscillator approach, too: the sealed air in the box makes the spring stiffer, which produces two effects: a raised resonant frequency, and a raised mechanical Q. Look at the equations for Q and Fo of a damped harmonic oscillator, you'll see what I mean. Once again, perfect agreement between the purely mechanical mass/spring/damping model, and the T/S electrical filter model.

There's still more: mount the speaker in a ported box. The Thiele/Small analysis gets complex enough to require lots of calculator time, or a computer and some suitable software to solve, but it tells you that (a) you now have two resonant frequencies, not just one, (b) one of the resonant frequencies comes from the mass of air in the port "bouncing" on the compliance of air in the box, (c) the outputs from the port and speaker cone add, with phase shifts and amplitudes that vary with frequency, in such a way that the combination acts like a 4th-order high pass filter at low frequencies.

If you notice, that "mass of air in the port, bouncing on springy air in the box" explanation, which usually goes along with most introductory discussions of the Thiele/Small paper, is in fact entirely a mechanical one! And it aligns exactly with what you get when you solve the mathematics for two coupled damped harmonic oscillators; one, the speaker, and two, the mass of air in the port bouncing on the "springiness" of the air in the box.

To me, it's entirely clear that Thiele/Small actually saw the problem for what it actually was in the real world (a mechanical one), and then converted it into a fictitious electrical problem, purely because it allowed them to use the mathematics of AC electrical filter theory, which in turn let them solve the original mechanical problem. It was a masterstroke, a very clever way to solve a difficult, and until then, poorly understood problem, using the mathematical tools that were available and practical to use back then, decades ago.

Today, we have easy access to computers, and software that models mechanical models just as easily as electrical filter networks. So we have the luxury of using either Thiele/Small's approach, or simply putting the mechanical system equations into Matlab, or Gnu Octave, or your mathematical software package of choice.

Quote:
Originally Posted by Ron E View Post
At some point , with rising resistance, Qms begins to dominate Qts rather than Qes
...that sounds like almost exactly what I said in my post #21. I don't think you and I have opposing viewpoints here at all, you know.

And, for the record, I have no reverence in terminology for terminology's sake, however, we all have to use words to get our message across. One person's "words" might be seen as another persons "terminology".

In other words, I don't care what it's called, I just want to understand how it works, but that's usually easier to do if I call a spade a spade, rather than a Furflefligger-maxxtrup.

-Gnobuddy
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Old 14th November 2017, 04:12 PM   #57
ChurritoTierno is offline ChurritoTierno  Paraguay
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Quote:
Originally Posted by PB2 View Post
To the OP, have you tried putting the driver into a free simulator such as Unibox?
I would consider tuning to the low 40s since that is the lowest note on a 4 string bass, or
do you play a 5 or 6 string? You can adjust the amplitude response at Fb by adjusting
the size of the box to avoid boom.

You could use an adjustable port to try different tunings.

I'd probably build it as two 2X10 boxes that you could stack for portability.
I don't want to mess with new software right now.. (is enough with the software that I learned at work (Im civilian engineer))

So,... yes, I have a four string bass,... 41 Hz the lowest note.. maybe even lower than this in drop D tuning..

And yes.. I was thinking to do two boxes 2x10"... For this is that I pretend to calculate a 2x10" box..

So, guys. At this time I'm totally stuning with yours info...
Maybe I should change the perspective of this thread. Maybe I should asking to you to directly design a 2x10" box with the drivers that I post earlier. So,.. if you were in my shoes,.. what would you do?
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Old 14th November 2017, 10:46 PM   #58
freddi is offline freddi  United States
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Vented box for bass guitar design - HELP!
here's some sizes of commercial 2x10 boxes Updated 2x10 Shootout! | TalkBass.com
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Old 14th November 2017, 11:52 PM   #59
GM is offline GM  United States
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Quote:
Originally Posted by ChurritoTierno View Post
Maybe I should asking to you to directly design a 2x10" box with the drivers that I post earlier. So,.. if you were in my shoes,.. what would you do?
~64.6 L tuned to ~42 Hz with a ~10.16 cm [4" dia.] x 13.10 cm [5.16"] long vent.

GM
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Old 16th November 2017, 10:29 PM   #60
freddi is offline freddi  United States
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Vented box for bass guitar design - HELP!
hey GM, one thing I noticed ~25yr ago with a 0.8X K15 was the timbre on my fretless G string was thickened and more even sounding than direct radiator. I guess only a certain range of parameters give that result.
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