In this course students learn the basic concepts of acoustics and electronics and how they can applied to understand musical sound and make music with electronic instruments. Topics include: sound waves, musical sound, basic electronics, and applications of these basic principles in amplifiers and speaker design.
Design Tools and Conclusions
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來自 University of Rochester 的課程
音频和音乐工程基础：第 1 部分，音乐声电子
277 個評分
從本節課中
Week 5 - Closed Box Loudspeaker Design RC & Ported Loudspeaker Design
Designing speaker enclosures, basic principles, interaction of speaker driver with the cabinet, why a cabinet at all? Speaker designs for home stereo, crossover networks, guitar amplifier (open) speaker enclosures, bass amplifier (closed and vented) speaker enclosures.
與講師見面
Robert ClarkProvost and Senior Vice President for Research and Professor
Mechanical Engineering
Mark BockoDistinguished Professor and Chair
Electrical and Computer Engineering
You know, you just finished an exercise in where we picked a queue, a fairly high
queue that's outside of the recommended range, and you see the box size got quite
small. And that's the basic rule is, is that
these smaller box sizes are going to lead to these this kind of a peaky response if
you will, because you're really changing the stiffness.
It's also going to change the the low-end frequency, the resonant frequency for
the, for the design as well. there are a number of really good design
tools that can be obtained online for free.
the example that the webpage indicated here, AJDesigner.com is worth taking a
look at. So let's let's pull that up.
alright. And there are a number of design tools as
well as advertisements but we can go to the audio subwoofer design area here.
And so you can see, you know, there are options for box design, vented design.
It goes through a number of the design. But there is a subwoofer box comparison
calculator and and I've used that. I think that would be a fun exercise for
you. I would encourage you to play with this a
little bit. let's just go over to the look at design
tool for a minute. You see the things that you input here.
so this is our subwoofer box design and you'll notice all of these parameters
that you see here on the page. If you scroll down he's defined them
here. So again volume of the air equal to the
speakers spring characteristics in liters.
total Q of the speaker, free air resonance, total Q of the speaker, free
resonance total Q of the speaker and the box.
here is a port diameter, if you're designing a ported speaker.
We'll come back to that later. it's the counter to define a little bit
around the alignment and the ripple associated with the response.
and he's given you some indication of whether you know, these would lead to
larger enclosures or smaller enclosures. And what the response would be in terms
of alignments. but if we look, you get an estimate of
what the frequency response would look like for given parameters.
So you know, we could we could go in and put the parameters associated with our
previous example. So we have 283 liters for the volume.
We have 0.5 for QTS. We had the frequency 30 hertz.
You can see these things changing at the bottom as we alter the design in a QTC.
The total Q we chose as 1. All right?
And if you do that we can see the estimated frequency response of this
close box design and you can drag along here and see what the response is.
The orange curve is the sealed, the green is the ported and the blue is the band
pass. What you can aslo see here is the box
volume. So, for the sealed box we get 94 leaders.
Now if you remember what we went through the exercise that's what we computed by
hand. Okay?
so you get parameters associated with the box.
you get your three DB points. again for the sealed box 3 DB points.
Again, for the sealed box, 3 DB is going to be about 47 hertz.
We'll talk about the ported later. you see the the change in the resonance
frequency of the box in the box it's 30, it's 60 hertz for the sealed enclosure,
course it doesn't have a port. Anyway this is a nice little design tool
when it allows you to get some picture of what your frequency response might look
like so, There's no cost for using this, this is
just on online tool. I would have a look at when you have a
chance. And you can repeat the exercise that we
had earlier, using the design tool. So, and answer your questions on the 3DB
frequency and such from your exercise. So next lecture, we're going to deal with
a ported design but I want to make a few final statements, relative to the, closed
box design, and that is, is you know if the box is too large the bass is going to
be weak or kind of sloppy. basically the box won't have any impact
on the, Driver's residence, you can't use the box
to stiffen it if it's too large. If the box is too small the bassist is
going to become boomy and that's going to give it a limited range.
You really, you know it will tighten it up, you will get peaky and you will,
uh... You know, basically the stiffness, the
equivalent stiffness will be so high that you'll move the resonant frequency up and
it will just end up being a, a much a much reduce frequency response.
So, the bottom line is, is there's a lot of trade offs in the design of speakers
and cabinets and fine tuning's Always necessary to create a real quality sound.
But you've got to pay attention to details even if you're building a simple
closed-box speaker, you really need to take care in, in building the closure
itself. Make sure it's nicely sealed.
Make sure that the the drivers are tightly attached and, and, and placed in
the enclosure itself paying attention to the, to the design and choice of the
volume and the drivers that you choose. You know, all of these are are just a
critical part of the design process, and actually what makes it makes it enjoyable
as well. So I look forward to talking to you on
the next lesson about ported design.
