Hi Danny. Some thoughts on your responses that will hopefully give further clarification to my design process, and entertainment for the readers
"You don't have to defend your choices. This is better quality parts than I typically see at this price point."
I hope I'm not coming across as needing to defend my choices. My intent is to allow people to understand what happens in the process of designing budget speakers, and just how careful you have to be in trading off one choice against another to meet the price objective.
"Keep in mind though that for a lot of these guys it's no big deal to throw a few extra dollars at something like this to see (or hear) what the results are. It's part of the fun of the hobby."
I agree. The balance is between DIY and just spending more money on a better speaker in the first place. For some people the most fun is gained from opening up a speaker and experimenting.
"I can understand the positive effect of using the softer MDF. I attack it a different way though. The No Rez product that I talked about uses a heavy damping layer that sticks to the cabinet wall with a pressure sensitive adhesive. It really knocks out the resonances of the cabinet walls."
Again, my comments are from the point of view of enlightening the readers. I am trying to get the best performance at lowest cost. Adding a product like No Rez to solve cabinet resonances is just not financially viable in production at these price points.
"You are correct. Standing waves is not technically what it is. Those waves are too long to propagate in the box. It is more of a pressure wave. There is a resonance there though that additional damping took away."
All waves propagate in an air space. There is no such thing as not propagating when the acoustic space is too small. Acoustic waves a re pressure changes that move away at the speed of sound. Resonances occur due to standing waves when the dimensions become integrally related to the wavelength. As such there will be a frequency below which no standing waves can occur, and no acoustic resonances will result. For the B6 the lowest standing wave will occur at around 540Hz, Below this there are non. Anything seen in the impedance curve below this frequency will not be due to standing waves. The most likely cause will be due to some mechanically excited resonance. This can be due to the panel modes in the cabinet, but again, 25Hz and 60Hz are much lower than the expected vibration modes of the cabinet. The main cabinet vibration mode that shows up in my impedance measurement is at 190Hz. I suspect what you saw is some mechanical coupling from however the speaker is mounted for testing, but we will not know until you are able to reproduce it.
"I'm not knocking the trim rings. They do look good. But there is a subtle change in the response from them."
"You are correct. The break in the trace is hidden under the zip tie. And I retracted that observation from the original post"
Thanks. You had me worried for a moment that I had let that slip through to production!
I trust that everyone will enjoy this expose of the design process involved.