WMcD Posted June 19, 2016 Share Posted June 19, 2016 (edited) In high school our physics teacher showed us one of these machines and explained what is shown in the more elementary part of the video. The video is more expansive and very educational. It can be applied to questions about standing waves in rooms. You just have to imagine that one wall is the source of the wave (actually originated by the speaker) and the opposite wall is doing the reflection. Our ears are the detector someplace in between. this assume we only have to worry about two walls, of course. It shows that the reflected waves can interact to form nodes (no sound pressure just there) and anti-nodes (higher sound pressure there). An important issue is that as frequency (wavelengths) change, so do the locations of these nodes and anti-nodes. It also shows the effect of a tapered matching section like the conical horn megaphone (which is a cousin of an exponential horn). I'll add one thing. What is not explained is how the motorized source of movement, the wiggle maker, affects things. To put maximum power into the transmission line, it must have the same impedance as the transmission line. We use Don Keele's equation to pick a driver (wiggle maker) which is correct for a throat size (impedance of the transmission line -- horn throat). This is based on an equation in the Symposium paper in the Klipsch papers. Please note that in the video, a dashpot is used to form a termination at the right side of the line to reduce or eliminate reflections (echo) because it has the same impedance as the transmission line. But we're now talking about the left-most end. Can there a dashpot equivalent there in the driver? It would be good to have that because otherwise the reflected wave would bounce off it and go back, travelling right-wards. Not good. The reflections would go on and on in the horn, like a hall of mirrors. You may have seen this coming. If we pick the correct driver, it has an impedance matched to the transmission line (horn throat) we get max power transfer into the horn, as described above. But this also means it presents a load which is matched to the transmission line and (BIG THOUGHT) it absorbs the reflected, left-moving wave which gets back to the throat. When the driver is properly selected, it puts max power into the line / horn, and ALSO acts as a perfect absorber of reflections coming into it. Therefore it is important for this second reason. This explains some comments in the Symposium paper and in Klipsch patents. We can use a sub-optimal, small, mouth which causes a reflection back left-wards if we have an optimized driver which will absorb the left -moving reflections. I'm sort of belaboring the point because it may be otherwise puzzling how the correct driver at the left end (throat) lets us get away with poor conditions (small mouth) at the right end. WMcD Edited June 19, 2016 by WMcD Quote Link to comment Share on other sites More sharing options...
Chris A Posted June 20, 2016 Share Posted June 20, 2016 See https://community.klipsch.com/index.php?/topic/154757-similarities-of-wave-behavior-by-bell-labs/ Quote Link to comment Share on other sites More sharing options...
WMcD Posted June 21, 2016 Author Share Posted June 21, 2016 Chris, My hat is off to you for finding the video first. I'm a bit sheepish over not having seen it. WMcD Quote Link to comment Share on other sites More sharing options...
Chris A Posted June 21, 2016 Share Posted June 21, 2016 No worries - I was just trying to connect up the two threads--nothing more. There really wasn't much discussion on the other thread. Your discussion is more apropos to the video's content, IMO. Chris Quote Link to comment Share on other sites More sharing options...
wvu80 Posted June 21, 2016 Share Posted June 21, 2016 Kudos to both of you for finding the video. I watched the entire thing and found it fascinating. I'm not sure what I have to add to a conversation about a video on physics except to say I know now, why I was a psych major. Quote Link to comment Share on other sites More sharing options...
ClaudeJ1 Posted June 22, 2016 Share Posted June 22, 2016 Great demos. Quote Link to comment Share on other sites More sharing options...
JohnA Posted June 22, 2016 Share Posted June 22, 2016 And surprisingly applicable to things in everyday life. Adjusting your radio antennas for optimum reception or transmission (SWR). Selecting shocks to match your springs to improve the ride quality of your car/motorcycle. Selecting a Helmholtz resonator for your car exhaust to kill a boom. Adding soft furnishings to your listening room or Dynamat to your metal horns. P-traps and crossover networks that absorb some frequencies and pass others due to resonance. Adding rubber washers to a bathroom fan to absorb vibration and make it quieter. Output transformers in a tube amp. Waay cool! Quote Link to comment Share on other sites More sharing options...
wvu80 Posted June 22, 2016 Share Posted June 22, 2016 (edited) Oops, wrong thread. Edited June 22, 2016 by wvu80 Quote Link to comment Share on other sites More sharing options...
JJkizak Posted June 22, 2016 Share Posted June 22, 2016 I watched the whole thing to make sure he was correct. He was perfect. ( a bit of humor here you know) JJK Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.