Yes, that's exactly what I said before, energy storage is resonance, they are not separate things. I think that the poster was trying to say that one could have "energy persistence" when there wasn't a resonance. That's not possible.
OK gentlemen;
I am not a fighter, I never come looking for a argument, I come to learn, please give me the benefit of that doubt if there is any.
In that light will you take a walk with me so that I may see where our understanding diverges?
Allow me to start with a familiar scenario in which I believe the term “energy persistence” correctly applies.
Consider a large acoustical space for wide range music as defined by Schroder of equal or greater than 250,000 cubic feet with an installed proper fullrange sound system.
When the sound system is driven with a wide range signal, a homogenous reverberant sound energy field develops in the space.
When the sound system is cut off, and the reverberant field is left to decay, what do we consider this reverberant tail as measured in an Energy Time Curve?
Sound persistence?
Energy persistence?
Stored energy?
As long as the sound system is delivering equal energy across the audio spectrum, can preconditioning the sound system signal, in any way that does not unbalance the equal energy output of the sound system, have any effect on the reverberant energy tail when the sound system is cut off?
Thank you.
Barry.
I am not a fighter, I never come looking for a argument, I come to learn, please give me the benefit of that doubt if there is any.
In that light will you take a walk with me so that I may see where our understanding diverges?
Allow me to start with a familiar scenario in which I believe the term “energy persistence” correctly applies.
Consider a large acoustical space for wide range music as defined by Schroder of equal or greater than 250,000 cubic feet with an installed proper fullrange sound system.
When the sound system is driven with a wide range signal, a homogenous reverberant sound energy field develops in the space.
When the sound system is cut off, and the reverberant field is left to decay, what do we consider this reverberant tail as measured in an Energy Time Curve?
Sound persistence?
Energy persistence?
Stored energy?
As long as the sound system is delivering equal energy across the audio spectrum, can preconditioning the sound system signal, in any way that does not unbalance the equal energy output of the sound system, have any effect on the reverberant energy tail when the sound system is cut off?
Thank you.
Barry.
I would call it reverberation, because that is what it is. All these other terms are just bad synonyms. But still, the energy is stored in resonances, its just that in your example there are thousands of them. We have been talking about a system with widely distributed and basically singular resonances. Your room acoustic example happens because there are so many resonances that individual ones are no longer evident, but rest assured that if there were no resonances, such as in a free field there would be no energy storage.
This question is not clear, or it hypothesizes an impossible scenario.
Reverberation is of course the proper name for the scenario I described. But if you should search for the definition of reverberation, the definition will not use that word to define it.
How about the afterglow of phosphors as used in fluorescent light? Energy persistance? Certainly not reverb.
I am attempting to find where my understanding fails me. Once the discussion moves beyond an acoustically reverberant space and the ETC measurment thereof, I will need the proper terms to use in the questions following.
The last question sould be simple enough to answer with one word.
Are you interested in helping me?
Thank you again.
Barry.
How about the afterglow of phosphors as used in fluorescent light? Energy persistance? Certainly not reverb.
I am attempting to find where my understanding fails me. Once the discussion moves beyond an acoustically reverberant space and the ETC measurment thereof, I will need the proper terms to use in the questions following.
The last question sould be simple enough to answer with one word.
Are you interested in helping me?
Thank you again.
Barry.
Eh? You've lost me there, what word?
The discussion has been about EQing the speaker. EQing the room is an entirely different matter, and can only be done to a degree by signal manipulation. Perhaps this will help
Why Can't I Fix All my Acoustic Problems with EQ?
So it is clear the intuitive empiricists still have misgivings about the idealistic model DBMandrake endorses. But what about DBMandrake's tests?
I love playing with REW as much as anybody who has ever spent endless hours with an AC-VTVM and graph paper. But some of the REW tests used by DBMandrake deserve closer scrutiny.
The fast-fourier world of such tools "buy into" the same idealistic model, chewing up impulses (or sweeps) and spitting out the various group delays, etc. that DBMandrake displays. Therefore, it may be more like twice-digested data rather than measurement of a physical reality, as he wishes to claim.
All I know is that when I knock on a cabinet (or a guitar), it talks back to me, whatever the EQ might be.*
B.
*OK, maybe I could EQ my knuckles
I love playing with REW as much as anybody who has ever spent endless hours with an AC-VTVM and graph paper. But some of the REW tests used by DBMandrake deserve closer scrutiny.
The fast-fourier world of such tools "buy into" the same idealistic model, chewing up impulses (or sweeps) and spitting out the various group delays, etc. that DBMandrake displays. Therefore, it may be more like twice-digested data rather than measurement of a physical reality, as he wishes to claim.
All I know is that when I knock on a cabinet (or a guitar), it talks back to me, whatever the EQ might be.*
B.
*OK, maybe I could EQ my knuckles
Last edited:
"As long as the sound system is delivering equal energy across the audio spectrum, can preconditioning the sound system signal, in any way that does not unbalance the equal energy output of the sound system, have any effect on the reverberant energy tail when the sound system is cut off?"
I believe the answer to that is simply NO
I believe the answer to that is simply NO
Thank you.
On that point we must agree to move further.
As to definitions, no dictionary uses the word you look up to define the word you looked up.
Also I understand the current conversation is about what can and cannot be corrected with EQ. The large space is a stepping stone for me. I am not sure where I get crossed up in the conversation so I am trying to get the definitions straight.
Barry.
Don't take my word for it, take some measurements of your own.
Measure any random conventional single cone driver you have sitting around (woofer, mid, full range, doesn't matter) that has known cone breakup resonances, even severe ones.
Have a look at the excess phase and excess group delay, and compare them to phase and group delay. What do you see ?
I've done this on many drivers, and I haven't found one yet where the resonances aren't completely minimum phase. Yes even on a whizzer cone full range driver, surprisingly.
On a single cone driver what I invariably find is that within a small margin of error there is no excess phase and the excess group delay response is a flat line which only curves up a bit at the bottom end due to limited gate time of the measurement causing errors in the low frequency phase estimation.
If you look at group delay you see the group delay variations at cone resonances that result from the rapid phase shifts but excess group delay is a near flat line with no trace of any of the resonances.
On a dual cone whizzer cone driver what you do see is some excess group delay and phase - but not at the cone resonances - just a very smooth, broad shift that looks not surprisingly like the excess group delay of a two way speaker with a 12dB/oct crossover.
Here is an example for you, and I've actually taken the more challenging example of a large dual cone full range driver to show that even in this situation the cone resonances are still minimum phase despite the extremely high modal density that must be present on the cone at high frequencies for an 8" driver... First the amplitude and (measured) phase response.
Plenty of peaks and dips there - must be resonances right ?
Here is the group delay (yellow) overlaid on top of the excess group delay: (blue)
I think this is very cool - in the group delay you can clearly see the group delay reflecting the resonances shown in the amplitude and phase response - the surround dip at 1Khz is especially obvious, but in the excess group delay (which is just group delay of excess phase) there is absolutely zero trace of any of these resonances at all. I think that's quite profound and it certainly shocked me when I first discovered this years ago.
All you see is a gradual hump at around 6Khz which is a result of the fact that the two cones have an mechanical/acoustic crossover at about 6Khz, so like any other crossover you see a peak in the excess group delay near the crossover frequency.
(This excess group delay measurement is in fact how I know what the crossover frequency between the two cones is, and this could be used to measure the acoustic/mechanical crossover frequency of any whizzer cone driver...and incidently, its interesting to note that the excess group delay minimum at 10Khz exactly matches the excess group delay minimum near 1Khz - which shows that the two cones are properly time aligned - which is not the case on some dual cone drivers I have measured)
If I were to repeat this same measurement on a single cone driver (which I have) you'd find the excess group delay is basically flat through the majority of the drivers bandwidth, with it just curving up at both ends due to measurement error. I used the dual cone driver as an example as otherwise I'd just have a boring, flat line...
So at least in this measurement there is proof that all the cone resonances are minimum phase as they don't show up even slightly in the excess group delay response. Which also means that even though the driver as a whole is not minimum phase, because the resonances are they can still be corrected by standard individual minimum phase PEQ or RLC notches, as I'm doing in my crossover.
Of course - I'm not suggesting that all drivers are minimum phase - clearly there are some that are not - like the one I just posted above. And you should always measure it to find out if it is the case or not.
But I'd say in the majority cases, the resonances of all cone drivers are minimum phase. I'm yet to find an exception to that rule, and on the face of it that does seem surprising, but the measurements are hard to dispute.
I can see why people consider drivers minimum phase, simply because acoustics summation part in the measurements are considered part of the DUT. If we consider only up to the point of cone movement, then we actually see a single input multiple output system. This is why I would rather not consider trying to categorize normal measurements, but rather look at the result and see how to make the cone move in a more uniform manner. I think it would be interesting to use the Klippel scanner to visualize how the cone is flexing when using FIR filter to linearize phase and reduce CSD decay time.
Perhaps it's instructive to know WHY reverberation can't be cancelled with EQ, and can't be cancelled in general. It's easy to see why EQ won't work, as reverberation has an integral time delay component that EQ does not address.
A single reflection can certainly be cancelled, as there is DSP code to cancel floor bounce from speakers. The problem (one of the problems) with cancelling reverb this way is the practicality of cancelling the many reflections (and the timing and amplitude of each one imprecisely known), even in a small room.
A single reflection can certainly be cancelled, as there is DSP code to cancel floor bounce from speakers. The problem (one of the problems) with cancelling reverb this way is the practicality of cancelling the many reflections (and the timing and amplitude of each one imprecisely known), even in a small room.
So if the CSD is the same as the FR and a flat response has a tight looking csd, then why do people talk about ribbons and things having an effortless sound. Is this all in their head or is there other measurements that show this?
Found this "In a loudspeaker driver that is behaving linearly, the transient response is inextricably linked to the frequency response. The ribbon tweeter may have a somewhat more extended high-frequency response, hence it has a better transient response. Ribbon tweeters do seem to have more peaks and dips in their frequency response curve, though, and so these will colour the sound quality compared to the more flat behaviour of a dome tweeter.
In a typical application, a ribbon tweeter is also usually taller in size than it is wide, in a ratio in the range 2:1 to 3:1. As a result, its vertical dispersion will be characterised by a strong frontal lobe and then a number of side lobes on either side. This can be beneficial in a recording studio near-field listening environment, as the intensity of the sound reflection from the table or mixing console upon which the loudspeaker sits will be reduced."
source: Ribbon tweeters: Pros and Cons - Harbeth: For 40 years - the world's most natural sounding loudspeakers
Found this "In a loudspeaker driver that is behaving linearly, the transient response is inextricably linked to the frequency response. The ribbon tweeter may have a somewhat more extended high-frequency response, hence it has a better transient response. Ribbon tweeters do seem to have more peaks and dips in their frequency response curve, though, and so these will colour the sound quality compared to the more flat behaviour of a dome tweeter.
In a typical application, a ribbon tweeter is also usually taller in size than it is wide, in a ratio in the range 2:1 to 3:1. As a result, its vertical dispersion will be characterised by a strong frontal lobe and then a number of side lobes on either side. This can be beneficial in a recording studio near-field listening environment, as the intensity of the sound reflection from the table or mixing console upon which the loudspeaker sits will be reduced."
source: Ribbon tweeters: Pros and Cons - Harbeth: For 40 years - the world's most natural sounding loudspeakers
Last edited:
My experience is that it is all in their head. They hear what they want to hear. Almost any system will be described as you suggest by somebody. Unless there is a way to blind test such claims then they are just opinion and likely highly biased.
Hello benb;
You went all the way in one shot to where I wanted to go.
It is the compexity of the signal and the doubtful ability to predict the resonances that get exited and the ones that don’t with a complex signal that makes me very skeptical that with music as a (complex) signal source that breakup mode resonances of a driver could be eliminated via signal conditioning.
Floor bounce? How on earth can a speaker cancel something it already let out? Manipulating it with crossover frequency and delay I get but to cancel it? How?
Barry.
To the above was my floor bounce question directed. How?
I have apparently failed to communicate, anything.
So here it is in a nut shell, I don’t believe that a device like a JBL 2451 with it’s ribbed titanium dome and diamond surround that rings like mad above 12kHz can be made to behave like a JBL 476Be, with any number of eq points.
All my best to anyone who actually read what I typed and spent any effort to see what I was trying to get at.
Barry.