Thanks Eric - By calling the cap a filter I am over-simplifying. In practice that’s what it appears to our ears to do. Thanks for the detailed explanation.
I have (If I can find them) extra 1" car tweeters that may even have filters included.
Jon Radder said:
Thanks Eric - By calling the cap a filter I am over-simplifying. In practice that’s what it appears to our ears to do. Thanks for the detailed explanation.
No problem. By day, I’m a professor of acoustics and audio at Berklee College of Music and consult in acoustics and noise control. Usually, my work only overlaps with real trains, but every once in a while, I can apply it to the little ones!
While technically the simple capacitor used a s 1 pole high pass filter to the tweeter is not a crossover, the natural falloff of the “bass” speaker, and the fact that you have even further “killed” the high frequencies by using the backside, having them hit the frame and finally be absorbed by the ballast gives you a “poor mans” crossover.
Also, the small amount of high frequencies that escape from underneath really won’t “harm” the “tweeter” facing up.
For Don’s edification, bass is more omnidirectional, so normally bass from either side of the speaker is the same. Since the enclosure is sealed, he’s going to get approximately the same base no matter which way the speaker is facing.
Also, if you grind the flange off that FRS7, it will fit right into the speaker “recess” and give you more clearance, see these pictures of an F3:
https://elmassian.com/index.php?option=com_content&view=article&id=573&Itemid=694
Jon Radder said:
Not disputing your math Eric, but isn’t a simple capacitor a High Pass filter?
Jon, I understand your comment now. I had accidentally typed LPF instead of HPF. You are correct, of course.
OK - It’s been over 30 years since I ran a sound reinforcement business. I had no formal education in the field, but did a lot of reading to help in my designs. While digging through a file cabinet yesterday I found some old school design slide-rules for speaker systems 
I was pretty sure the cap was high pass, but your technical explanation made it sound like it maybe wasn’t. Glad to know my memory isn’t quite as fried as I thought it might be (https://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-surprised.gif)
No, you’re right. I thought you were commenting that the cap itself was the filter, and my explanation was intended to explain the importance of the resistive load in the equation. I was answering a question you weren’t asking. I corrected my post.
Well, I did think that until you explained it I now know more than I ever wanted to about how crossovers and filters work (https://www.largescalecentral.com/externals/tinymce/plugins/emoticons/img/smiley-cool.gif)
