Any circuit that can generate harmonics? (I am a new fish)

[keffen611]

Hi everyone
I am a undergraduate of electronic engineering in HK.
I am currently undergoing a final year project that focuses on "Missing Fundamental"
which means that enhance the bass (e.g. below 150Hz) by adding the harmonics of that particular frequency.
I do this because I want to compensate the "bad low end response" of the speaker.
Any device that I can follow?
Is it the "Karate Shop" that suits my project?
Thank you very much!

[midwayfair]

Hrm, sorta.

-You can generate an octave down (-8va) with analog circuitry pretty easily. Madbean's Lowrider is a good example, and you can dial out the actual fundamental or boost different octaves at different rates. Perhaps not exactly what you're asking about.

-Distortion will generally enhance harmomics already in the signal. Unfortunately, most of the harmonics generated are multiples UP, not down. I guess you could design a circuit that blends (in parallel with the dry) a big signal with a steep frequency cutoff of 150Hz.

-You can, of course, use an EQ pedal or band pass filter to boost certain frequencies. Certainly boosting the low mids would make the fundamental more noticeable than the harmonics ... to a point.

But the problem with any sort stomp box approach is that you're sticking the stompbox in front of a guitar amp, which is in front of the speaker. The cabinet is involved. The amp creates its own harmonics, and if you shove a bandpass into the amp, it's going to see that, amplify the signal accordingly, and generate upper harmonics when the signal clips, and then send it to a speaker and cabinet that are designed to have a frequency rolloff generally around 72Hz.

Heck, most fender blackface style amps ALREADY have a bump in the typical midrange frequencies of a guitar, so you can easily end up making the amp sound boxy rather than enhancing the bass.

Also, note that I'm being a little vague about some things. We don't know what speaker you're trying to compensate for, what "bad" is (sometimes "bad" bass response in guitar cabinets means too much, like in the Fender Hot Rod Deluxe, and it can also be volume or gain specific), what instrument you're looking to run through the effect, what amp is involved, what kind of headroom you have, what your final desired overall sonic outcome is, or myriad other considerations. More clearly defining your goals and giving specifics of the equipment and maybe there's something else to consider.

[keffen611]

 Thank you.
I have purchased a plasma speaker (experimental purpose) to investigate its performance(frequency response).
And I want to enhance the bass by adding the harmonics(e.g. if I want to boost 50Hz, then I need to create 100Hz, 150Hz, 200Hz ...). And say if I want to boost all low frequencies which are <150Hz, then any circuit diagram I can adopt to fulfil the requirement?
Thank you again!!!

[midwayfair]

And say if I want to boost all low frequencies which are <150Hz, then any circuit diagram I can adopt to fulfil the requirement?

Any active EQ circuit should work. It should be a textbook circuit ... you might consider a multipole filter, though, if you are really interested in really limiting it to 150Hz.

As far as CREATING harmonics, especially downward, that's much more difficult. The octave circuit idea I mentioned is one way to do that, but it's not the cleanest thing in the world. Even digital has a hard time creating clean octaves.

[keffen611]

I have found a journal for "Missing Fundamental"
Actually, I need to implement the diagram of Fig.2
and I need to find a "non linear device" that matches with the characteristics of Fig.1
Any idea?
Thank you very much!!!

[keffen611]

sorry for not including the link.

http://www.adamjhill.com/Hill%20+%20Hawksford%20-%20CEEC%202010.pdf
please check it

[raulduke]

sorry for not including the link.

http://www.adamjhill.com/Hill%20+%20Hawksford%20-%20CEEC%202010.pdf
please check it

Does your lecturer know your trying to get Jon to do your homework for you  ?

[keffen611]

who is Jon?