# Need help with speaker design HW

Hi all, I have some HW that I am really having some trouble with, since the professor didn't really explain how to do the problem in class, and there is no text book for this class (Loudspeaker and Sound System Design).

This is the homework, and any help and explanation of how I should go about analyzing the circuit would be helpful. Thanks.
http://img364.imageshack.us/img364/8558/ee423homework1xg9.jpg [Broken]

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consider all the components in S domain, i.e. inductors in jomegaL, capacitors in (1 / jomegaC) and resistors in ohms.

series the rightmost resistor and capacitor and make the result in parallel with the other component on the left except the leftmost resistor.from this circuit find the current. use this current to find the voltage across the parallel components. then use voltage divider rule to find Eout

just to compare the work, which university and what year are you in?

I am a junior at USC (SoCal). This is supposed to be a Junior/Senior class, with more seniors in the class.

This stuff is supposed to be review, but I need to get a textbook first and brush up on some circuit analysis, since I haven't had to do much analysis in the frequency domain. Reducing the circuit was not the problem, but the frequency analysis part was.

Also, do you know of any good loudspeaker or sound system design books that I can try to find and read?

berkeman
Mentor
Thread moved to the homework forums. Welcome to the PF, pyro_dragon. Keep in mind that homework problems should be posted in the appropriate homework forum, not in the general forums. If it's a complex upper-division or graduate-level project, it may be allowed to stay in a more specific general forum, up to the discretion of the Mentors.

So were you able to figure this transfer function out? And for your question on resources for reading about speakers and sound systems, I googled speaker design tutorial, and got lots of hits. Here's the hit list:

Thread moved to the homework forums. Welcome to the PF, pyro_dragon. Keep in mind that homework problems should be posted in the appropriate homework forum, not in the general forums. If it's a complex upper-division or graduate-level project, it may be allowed to stay in a more specific general forum, up to the discretion of the Mentors.

So were you able to figure this transfer function out? And for your question on resources for reading about speakers and sound systems, I googled speaker design tutorial, and got lots of hits. Here's the hit list:

Thanks for the welcome, and I will keep that in mind for future homework questions. :)

I asked my TA, and he told me to use get spice and learn how to use it to get the frequency response. I managed to end up with a graph that looked correct when I compared it with some people in my class today, but I think my scale was off, since I haven't figured out how to set the axis to 50 db per decade in spice yet, I relied on the auto-format. I haven't really had to do transfer functions before, so I have some reading to do this week, so I can understand why the results from spice are as they are. I definitely have my work cut out for me in this class.

berkeman
Mentor
I managed to end up with a graph that looked correct when I compared it with some people in my class today, but I think my scale was off, since I haven't figured out how to set the axis to 50 db per decade in spice yet, I relied on the auto-format.
You don't set an axis to 50dB/decade. You set the range of gain on the vertical scale (like with 0dB at the top and -100dB at the bottom or whatever), and you set the limits of the frequency range for the horizontal scale (usually log scale for transfer functions). You might end up with a transfer function that is falling off at 50dB/decade somewhere in the graph. That's probably what you meant?

You don't set an axis to 50dB/decade. You set the range of gain on the vertical scale (like with 0dB at the top and -100dB at the bottom or whatever), and you set the limits of the frequency range for the horizontal scale (usually log scale for transfer functions). You might end up with a transfer function that is falling off at 50dB/decade somewhere in the graph. That's probably what you meant?
No, our professor said apparently the "standard" graph is supposed to be set on a scale of 50dB/decade, so I am assuming that for every decade on the x-axis, there needs to be 50dB on the y-axis. Maybe it is a standard in the speaker design industry or something.