lieven said:
I confess that I don't understand what your trying to get across in this post.
I use Clio Lite for measuring drivers and speakers. It allows the use of stepped sine waves and MLS for measuring frequency response. When using MLS you can set the start and stop time window to gate out as much or as little as you want. The stepped sine method has a sort of gating (delay) that can be used also.
I'm not sure what you mean by replacing the first impulse with noise. The impulse is generated with the MLS in Clio and most other systems I'm familiar with.
Russ
Russbryant,
The point here is to use two independent impulses for each different sequential measurement, one to get the room in 'reverbation mode', and the second (the one we measure) to get the freq diagrams of the speaker in that room with dying-out reverbations after different delays (accumulated shifting).
This will not give you the same result as a normal MLS diagram because you're measuring an activated source in a dying-out-reverbation-enviroment, and not in a permanently exited room as with a single MLS measurement, or/and as with a single impuls where source and reverb are both dying out at the same time.
The point here is to use two independent impulses for each different sequential measurement, one to get the room in 'reverbation mode', and the second (the one we measure) to get the freq diagrams of the speaker in that room with dying-out reverbations after different delays (accumulated shifting).
This will not give you the same result as a normal MLS diagram because you're measuring an activated source in a dying-out-reverbation-enviroment, and not in a permanently exited room as with a single MLS measurement, or/and as with a single impuls where source and reverb are both dying out at the same time.
Konnichiwa,
It is there, as can be observed, but it's action appears "delayed" (look again carefully at the impulse response) such as IF it is well decoupled for fast movements and coupled for slower ones.
I repeat, unless the added mass can be coupled rigidly to the voice coil (I did my own measurements a good while ago that way BTW, no dustcap and leadstrip coild around and directly epoxied to the exposed voice coil former, pulse generator, Mike & 'scope) I cannot accept the measurements as sufficient proof.
Sayonara
PS, if you follow the math in Dan's paper really closely and his further reasoning you find a slight slip of logic, where he completely discounts M as factor, even as one with only a "scaling" influence....
russbryant said:
It is there, as can be observed, but it's action appears "delayed" (look again carefully at the impulse response) such as IF it is well decoupled for fast movements and coupled for slower ones.
I repeat, unless the added mass can be coupled rigidly to the voice coil (I did my own measurements a good while ago that way BTW, no dustcap and leadstrip coild around and directly epoxied to the exposed voice coil former, pulse generator, Mike & 'scope) I cannot accept the measurements as sufficient proof.
Sayonara
PS, if you follow the math in Dan's paper really closely and his further reasoning you find a slight slip of logic, where he completely discounts M as factor, even as one with only a "scaling" influence....
454Casull said:
The room gain and wavelength thing is usually misunderstood.
One will need a speaker reproducing down to 20 Hz
to reproduce 20 Hz in a small room, no matter the room size
or shape.
jewilson said:454Casull
You have to have a room that is long enough to reproduce a 20 Hz wave lengthor it does not happen.
You are wrong. There is no requirements for the size of the
room. For example we have a rather small home theater
that is smaller to every direction than the wavelengths used
in it. Bass works fine down to 18 Hz or something and it is
both feelable and heardable. We have 18 inch subwoofer
though with 1.2 kW of amplification...
If you have any problems getting your speakers reproduce
down, you should consider acoustic treatment to the room
which involves bass resonators which decreases the room
gain of unwanted frequency peaks.
Luke (Uof Iowa) said:
In cars the acoustic gain is just stronger than in rooms at home.
Bass is very well reproduced down to 20 Hz in cars. In fact
the smaller the room is, the more output one will get on
the low frequencies because the room gain increases. Of course, the smaller the room is, the closer the dips and peaks in the frequency response will be, and the more problems you will have acoustically with the placement of your speakers and your head.
Best Wishes,
Karoliina
Karoliina,
I was trying to point out that a sinewave canot be reproduced in a small room, a complete waveform or a complete 20Hz period. This does not mean that you can not hear part of that waveform.
So I use this example, for all frequencies below 200 Hz or so all of the "dominant "sound waves in a room exist as standing waves, room modes, or resonances (all three mean exactly the same thing). The lowest mode is when 1/2 wavelength fits in the room, not 1 wavelength or sinewave. At lower frequencies, or any frequencies away from a resonance, the "sound still exists"; it is just a lot lower in amplitude. Essentially, there is still a wave bouncing back and forth, but the reflections do not reinforce each other as they do for a resonance. Whether the human ear can "hear" the sound is another question, but the sound is there as far as physics is concerned.
Cheers
😀
I was trying to point out that a sinewave canot be reproduced in a small room, a complete waveform or a complete 20Hz period. This does not mean that you can not hear part of that waveform.
So I use this example, for all frequencies below 200 Hz or so all of the "dominant "sound waves in a room exist as standing waves, room modes, or resonances (all three mean exactly the same thing). The lowest mode is when 1/2 wavelength fits in the room, not 1 wavelength or sinewave. At lower frequencies, or any frequencies away from a resonance, the "sound still exists"; it is just a lot lower in amplitude. Essentially, there is still a wave bouncing back and forth, but the reflections do not reinforce each other as they do for a resonance. Whether the human ear can "hear" the sound is another question, but the sound is there as far as physics is concerned.
Cheers
😀
jewilson said:
Personally, I prefer listening to transient events, like music, rather than sinewaves 😉
if i take a small room and bump up the pressure from 1bar to 1,1 bar in 1 hour in sinwavefrom, and let ist go down to 1,0bar again 1hour, and repeat this - what is this else but a very deep bass?
someone here should start thinking, there is no 20meters wave in your ear, there is a pressure change.
someone here should start thinking, there is no 20meters wave in your ear, there is a pressure change.
till
till; you seem to good at stating the obvious, how do we her anything at all.
Oh I do like the horns you have built, there are cool. We should discuss them sometime instead of beating this dead hore any more.
-------------------------
pinkmouse,
It not possible to explain acoustics are speaker fundamentals by making that kind a of statement. Well I like to listen to music to…
😀
till; you seem to good at stating the obvious, how do we her anything at all.
Oh I do like the horns you have built, there are cool. We should discuss them sometime instead of beating this dead hore any more.
-------------------------
pinkmouse,
It not possible to explain acoustics are speaker fundamentals by making that kind a of statement. Well I like to listen to music to…
😀
Fair comment.
I suspect that the problem is that most of us are taught that sound waves are all made up of sine waves at school, and it sticks in our heads forever. This is greatly oversimplified!!!
It is just a good approximation for the majority of people who never need to know any more, and explains some basic stuff well. Like Rutherford's "plum pudding" model of an atom. Good for the average bloke on the street, but for an astrophysicist it isn't useful at all.
Sound waves are areas of compression and rarefaction propagating through a medium. Yes, you can use sine waves to mathematically describe this, but you can also use sine waves to describe the motion of a jelly, but that doesn't tell you anything about the fact that it is orange flavour. 😀
I suspect that the problem is that most of us are taught that sound waves are all made up of sine waves at school, and it sticks in our heads forever. This is greatly oversimplified!!!
It is just a good approximation for the majority of people who never need to know any more, and explains some basic stuff well. Like Rutherford's "plum pudding" model of an atom. Good for the average bloke on the street, but for an astrophysicist it isn't useful at all.
Sound waves are areas of compression and rarefaction propagating through a medium. Yes, you can use sine waves to mathematically describe this, but you can also use sine waves to describe the motion of a jelly, but that doesn't tell you anything about the fact that it is orange flavour. 😀
As I recall, it was not Rutherford but Thomson who proposed the "plum pudding" modelpinkmouse said:
454Casull said:
Quite correct, well spotted!🙂
Rutherford disproved the model...
JJ Thompson, Dalton and Crookes all seemed to have come up with the idea at around the same time, so correct attribution is tricky.
Hi all,
It's really been beaten to death on multiple forums, by multiple people, and the conclusion has been consistent - rise time/bandwidth is NOT affected by mass. Period. From a high end extension (and, via the Fourier Transform transient response) mass is simply a scalar of the output level; it does not limit how high in frequency you go.
The key is to remember that, for a point source (a driver is close enough, when you're in the far field), acceleration is NOT the bandwidth, but SPL. Rate of change of acceleration is bandwidth. As such, changes to the driver that are time-invariant do not affect bandwidth, but SPL.
The data posted shows this to be the case; the rise time (extension) of the driver was not affected by the mass, but clearly the inductor rolled off the high end. It's really an easy test to do as well - place mass on the driver (we use Silly Putty - it adheres quite well to most cones, does not leave an oily residue, and is quite well internally damped so as not to add more resonances to the cone) and measure the bandwidth. Then add an inductor in series and measure the bandwidth. You'll see right away what happens.
I've had a few people question this, and after making their own measurements (one individual in Denmark, another in Australia), they both reached the same conclusion. Mass affects efficiency, not bandwidth.
Dan Wiggins
Adire Audio
It's really been beaten to death on multiple forums, by multiple people, and the conclusion has been consistent - rise time/bandwidth is NOT affected by mass. Period. From a high end extension (and, via the Fourier Transform transient response) mass is simply a scalar of the output level; it does not limit how high in frequency you go.
The key is to remember that, for a point source (a driver is close enough, when you're in the far field), acceleration is NOT the bandwidth, but SPL. Rate of change of acceleration is bandwidth. As such, changes to the driver that are time-invariant do not affect bandwidth, but SPL.
The data posted shows this to be the case; the rise time (extension) of the driver was not affected by the mass, but clearly the inductor rolled off the high end. It's really an easy test to do as well - place mass on the driver (we use Silly Putty - it adheres quite well to most cones, does not leave an oily residue, and is quite well internally damped so as not to add more resonances to the cone) and measure the bandwidth. Then add an inductor in series and measure the bandwidth. You'll see right away what happens.
I've had a few people question this, and after making their own measurements (one individual in Denmark, another in Australia), they both reached the same conclusion. Mass affects efficiency, not bandwidth.
Dan Wiggins
Adire Audio
Konnichiwa
Aka "Blue Tack". A substance recommended to adhere speakers to stand in the british hifi press, specifically BECAUSE of it's decoupling effect. As expected.
Bandwidth is not the issue (BTW, reducing the "B" does reduce the HF output with fieldcoil drivers, past the efficiency considerations). Moreover, the aceleration does in my experience differ (yes, so does the how far the "step" rises aka efficiency) simply because I observe (in measurements where the mass was rigidly coupled to the voice coil former) also a less steep initial slope. This to me indicates less ACELERATION.
Sayonara
DanWiggins said:
Aka "Blue Tack". A substance recommended to adhere speakers to stand in the british hifi press, specifically BECAUSE of it's decoupling effect. As expected.
DanWiggins said:
Bandwidth is not the issue (BTW, reducing the "B" does reduce the HF output with fieldcoil drivers, past the efficiency considerations). Moreover, the aceleration does in my experience differ (yes, so does the how far the "step" rises aka efficiency) simply because I observe (in measurements where the mass was rigidly coupled to the voice coil former) also a less steep initial slope. This to me indicates less ACELERATION.
Sayonara
I allready stated my similar point of view in this matter in post 30 of this same thread.
Think Dan rephrased it with (I hope) a bit more authority.
Think Dan rephrased it with (I hope) a bit more authority.
Kuei,
Blue Tack is radically different than Silly Putty (SP). SP is a classic non-Newtonian fluid, in that slow pressure changes aren't resisted, but high velocity changes are. If you put a wad of SP on a desk, it will flow out flat after half an hour or so. Drop it on the floor and it bounces like a superball. Because of this behavior, it's a great mass load material - it will not deform or decouple with higher velocities experienced on cones.
Note, too, that you may in fact observe a change in the acceleration; but that is NOT what we want! A change in acceleration correlates to a change in SPL (SPL is acceleration); the rate of change of acceleration is bandwidth, and THAT is what is constant.
Dan Wiggins
Adire Audio
Blue Tack is radically different than Silly Putty (SP). SP is a classic non-Newtonian fluid, in that slow pressure changes aren't resisted, but high velocity changes are. If you put a wad of SP on a desk, it will flow out flat after half an hour or so. Drop it on the floor and it bounces like a superball. Because of this behavior, it's a great mass load material - it will not deform or decouple with higher velocities experienced on cones.
Note, too, that you may in fact observe a change in the acceleration; but that is NOT what we want! A change in acceleration correlates to a change in SPL (SPL is acceleration); the rate of change of acceleration is bandwidth, and THAT is what is constant.
Dan Wiggins
Adire Audio
Why do so many people think that 1/2 of a wavelength is required for a resonance to occur? Only 1/4 of a wavelength is required for resonance, and many musical instruments are proof of this. In the case of a standing 1/4-wave in a room, there will be 2 distinct regions of air:jewilson said:
Nodes - where the SPL is high because the air has nowhere to go, eg: up against an opposite wall.
Antinodes - where the air velocity is high, nearer the speaker.
At a frequency where a resonance like this can occur, the mechanical load on the speaker is reduced, even though the SPL can be consistent in various parts of the room.
CM
Konnichiwa,
Oh, okay. Sorry then, my bad.
Hmmm. The original spat started with me saying "the aceleration changes if increase mass" and someone resisting this point and saying "no it does not and cannot", pointing to your article and measurements. I find it fuynny that after thei we both agree - a change in acelleration can take place (let's leave the purported acoustic effects out of this, that is another book entierly).
Fine with that in principle given the usual "non-ideal reality vs. ideal model" caveats.
Sayonara
DanWiggins said:
Oh, okay. Sorry then, my bad.
DanWiggins said:
Hmmm. The original spat started with me saying "the aceleration changes if increase mass" and someone resisting this point and saying "no it does not and cannot", pointing to your article and measurements. I find it fuynny that after thei we both agree - a change in acelleration can take place (let's leave the purported acoustic effects out of this, that is another book entierly).
DanWiggins said:
Fine with that in principle given the usual "non-ideal reality vs. ideal model" caveats.
Sayonara
Kuei Yang Wang said:
Acceleration does in fact change, but that is SPL; the rate of change of acceleration is constant when you tweak the moving mass or BL, and that means the transient response is constant. Subtle but critical distinctions.
Dan Wiggins
Adire Audio
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