[AndrewJ]

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."

Agreed....Subtle....

"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.
Andrew

[Hank]

Welcome, Andrew!  It's great to see your talented self here.  I really enjoyed your AVS Forum interview re your Pioneer speakers.

Danny, you're response to random out-of-the-blue jabs on here has certainly matured over the years - kudos! (that's not in reference to you, Andrew  )

[Danny Richie]

I'm sure you know as it's science that has been used for many years.  I've used a form of it in tape for literally 15 years.

Oh I know. My point is that you accept that it works, but you can't explain how it works. And in audio often times you don't need to know exactly why something works if the results are known and repeatable.

[jtwrace]

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."

Agreed....Subtle....

"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.
Andrew

I can't wait to see what you do with the ELAC Flagship speakers!  Those very well could be my next pair of speakers!

[Odal3]

I trust that everyone will enjoy this expose of the design process involved.

Most definitely!!!  Andrew and Danny - what an interesting read and thank you for sharing the thought process for designing and/or tweaking it. It's great to be able to listen in to a constructive and positive conversation. 

Andrew - please come back and share the design processes for future speaker designs as well!

[werd]

Oh I know. My point is that you accept that it works, but you can't explain how it works. And in audio often times you don't need to know exactly why something works if the results are known and repeatable.

It helps if they know what field of science their claims fall under.

[RDavidson]

Nope.  It's ALL science.

Right, just like how musical instrument design and construction is 100% science based.

Because science can inform how a speaker (an instrument) performs the way it does, doesn't negate the fact that art didn't have anything to do with making it so.

[jtwrace]

Typical GR thread. 

[Danny Richie]

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.

Yeah, yeah, I am with you on that stuff. I think the terminology we used used caused some confusion. Like when you said, "For the B6 the lowest standing wave will occur at around 540Hz" But then you said, "There is no such thing as not propagating when the acoustic space is too small." When I said the space is too small to propagate a waveform I was talking about wavelengths below that 540Hz point. Yes, pressure changes occur below that, but that wavelength will not create a full wave. I think we are on the same page with that.

Now, aside from that, there are pressure changes in the box that have to do with the flow of air in the box and this does not move at the speed of sound. Air doesn't compress and move that fast by a long shot. And that may have more to do with the resonances being excited down low.

I just measured the other speaker that I have that is still in stock form and the two resonances are there in it as well. I changed what it was sitting on and got no change. It is internally created. Next I will add just a little fiberglass insulation (not much) and measure the effect again. I'll post the results shortly.

[Danny Richie]

Typical GR thread.

Yeah really. What's wrong with these people? If you can't measure a difference then there's no difference right? All these subjective camp listeners must just drive you crazy.

[Danny Richie]

Hey Andrew,

I took an impedance measurement of the stock speaker. Here it is.



I then added a small square of insulation behind the woofer that is not packed in and fills just the back half of the box. And I moved the small piece of poly fill that was on the crossover to the floor of the cabinet. I did not add anything to the top of the box. It is still a bare wall.



And here is the result on the impedance curve:



The two resonances are now gone.

[AndrewJ]

"Yeah, yeah, I am with you on that stuff. I think the terminology we used used caused some confusion. Like when you said, "For the B6 the lowest standing wave will occur at around 540Hz" But then you said, "There is no such thing as not propagating when the acoustic space is too small." When I said the space is too small to propagate a waveform I was talking about wavelengths below that 540Hz point. Yes, pressure changes occur below that, but that wavelength will not create a full wave. I think we are on the same page with that. "

I think we are still on different pages. Your terminology is technically confusing. Sound is a compression wave that propagates at the speed of sound. A standing wave occurs when the wave is reflected back and interferes with the original wave. When the delay is integrally related to the wavelength, a standing wave results. Below a certain frequency this standing wave cannot occur, but there is still a wavefront being propagated, there is still a reflected wave, and there is still energy being delivered by the progressive wave. I don't quite know what you mean by not creating a full wave. I think you are maybe trying to convey a concept that is fully discussed in all acoustic textbooks, but using different language to describe it, but in the process causing extra confusion.

"Now, aside from that, there are pressure changes in the box that have to do with the flow of air in the box and this does not move at the speed of sound. Air doesn't compress and move that fast by a long shot. And that may have more to do with the resonances being excited down low."
 
Air compresses fast enough for sound to travel at the speed of sound, 433m/s. It also compresses fast enough to allow frequencies of at least 1MHz to propagate, though with large transmission loss. Now I know that there is no bulk flow of the transmission medium, the air, but that isn't required in order to propagate the sound wave.
Now if you are thinking more about the velocity of air flow in a vent in a reflex tuned system for example, then this is entirely different.


"I just measured the other speaker that I have that is still in stock form and the two resonances are there in it as well. I changed what it was sitting on and got no change. It is internally created. Next I will add just a little fiberglass insulation (not much) and measure the effect again. I'll post the results shortly."

As of now, until we do more more investigation, the only thing that occurs to me other than mechanical resonances is a small leak acting as a Helmoltz resonator. This has the potential to mess with the impedance curve. Let me know what you find with the other speaker.

[Danny Richie]

Andrew,

Highlight the text that you want to quote by right clicking the mouse and dragging through it. Then hit the quote button. The quote tags will appear before and after the text. Then respond after that.

You can edit your past posts that way too if you want.

[Danny Richie]

Let me know what you find with the other speaker.

Both speakers have the two resonance peaks in the bottom end and in the same places.

And in both cases additional insulation killed the two peaks.

[AndrewJ]

Hi Danny. Thanks for the quote tip

[rollo]

    The measurements taken and shown are what to me appears spot on. The resonance is gone. Really all WTF do you want different measurements.
    Danny does not guess or "figure" he measures and the results are obvious for all to see. STOP bashing and maybe learn a thing or two. Geez.



charles

[AndrewJ]

Charles. Please don't blow a gasket

[AndrewJ]

Hi Charles. Oops, I lost the rest of my commentary when I posted. I wasn't intending to sound rude with a short post!! Forgive me.
What I was intending to continue to say was that I believe Dany and I are having an open discussion about the difference in results between his experiments and my own.
This is the process of scientific experimentation. Do an experiment, publish the results, allow others to verify or not with their repeat of the measurements, then discuss the results.
That is where we are now. I have measured several paid from our production run. I don't see the same effect. So, it's either because of measurement process, or because I'd some difference in the speakers that I do not yet understand. On top of that, is the assumption that it is acoustic resonances the true cause. I'm fascinated to find out what is happening. That how how I work and advance.
Regards
Andrew

[RDavidson]

Charles. Please don't blow a gasket

Rollo, the conversation has been pretty great. There are a few detractors with nothing to offer, but the meat of the thread and dialog between Danny and Andrew has been very interesting and informative. Asking questions is all part of good critical discussion.

[Danny Richie]

Hey Charles, It's okay. We're all good.