thanks, i think the penny dropped here😀. so we all agree the natural frequency is unaffected by damping. this is where we have the impedance peak. this peak get lower in magnitude and wider as we apply more damping.
the omega_d is the frequency of the oscillation of the impulse response h(t)=exp(p•t) where p is the complex pole. omega_d is the imaginary part of p whilst the real part is the decay rate. the modulus |p| is the natural frequency. The formula you showed is simply Pythagora’s applied to find omega_d from the natural frequency and damping. I was raised to think of poles and eigen values 😀
But yes, I never thought about that theactual damped oscillation frequency drops compared to the natural when we have damping😀
If you're in the luxury to be able to determine the natural oscillation frequency directly.
With quite some mechanical systems you don't have that luxury and you can only measure the underdamped response.
And although a few percent doesn't sound all that much, it can completely screw up your mechanical feedback system.
The issue with speaker drivers is that de stiffness is so damn non-linear, so we can't rely on those methods.
Which is also a good thing, otherwise you run to risk of sending almost any overhung system to its death very quickly.
Agree.
I have a passion for methods for pole identification. A very non trivial problem - especially when it comes to speakers and acoustics. I do that on electrical impedance curves and identify motional/mechanical resoances.
By finding the decay rate and the damped oscillation frequency we directly get the natural frequency
I have a passion for methods for pole identification. A very non trivial problem - especially when it comes to speakers and acoustics. I do that on electrical impedance curves and identify motional/mechanical resoances.
By finding the decay rate and the damped oscillation frequency we directly get the natural frequency
you can add a so-called conjugate network right at the input side of the xover filter and flatten the impedance. This will not ruin the disotriton reduction effect from having higher filter output impedance into the tweeter. This makes life easier for the amplifier (the ET amps dont care much about reactive loads though)
I've seen burst tests to capture thermal compression.... and you are right it seems to happen in a few milliseconds. Not sure how we could tell this from a tweeter's specs. For instance, if a tweeter is rated to 100W.... does that mean it won't compress at 10W?
For my needs, for instance, 20W in the tweeter would be very loud... but given how tweeters are measured I may not be able to ensure that in my listening range (1/2W - 10W) there won't be compression. A dilemma for sure. I can absolutely understand why the high efficiency, horn tweeter crowd crows about how much less compression they hear. When loud is 2W in a massive ventilated motor structure you may never ever hear any compression at all, horn artifacts be damned. 😊
For my needs, for instance, 20W in the tweeter would be very loud... but given how tweeters are measured I may not be able to ensure that in my listening range (1/2W - 10W) there won't be compression. A dilemma for sure. I can absolutely understand why the high efficiency, horn tweeter crowd crows about how much less compression they hear. When loud is 2W in a massive ventilated motor structure you may never ever hear any compression at all, horn artifacts be damned. 😊
I second your comment about the impressive specs and clean crossover!
My most important spec after FR (phase included), is also dynamic range/uncompressed SPL.
I've tested this a bit, and the only way I've found I have confidence in, is to use short term bursts, comparing scope captures of the line-level stimulus signal va a microphone's acoustic capture.
When they quit moving in lockstep as signal as raised, it's time to find out why. First is to make sure amp has stayed linear, by scoping it vs stimulus.
If amp is linear, I know the driver is either limiting mechanically or thermally. I don't really know how to separate one from the other, but I think pragmatically it doesn't really matter....linearity has been lost and I know at what voltage level.
I've kinda learned I only need to run bursts on the bottom end of a drivers passband, where excursion is greatest...that always seems to be what limits first.
As for as longer-term thermal, I haven't used it yet due to the noise it would make, but freeware from Eclipse Audio runs the AES75 test for maximum linear SPL. Uses AES Music-Noise as the stimulus.
https://eclipseaudio.com/downloads/SpeakerMeasure with AES75 Quick Start Guide.pdf
I truly believe the ability to reach higher SPL, that is uncompressed & unclipped, including headroom for transients.......
......throughout the entire spectrum........especially for the very bottom and top ends where it's hardest to achieve....
.....is what separates speakers more than anything else, once FR is decent.
I think it's also a great goal for the purpose of keeping distortion low.
That may be true, but in the publicly available dynamic range tests I'm thinking of I seem to remember compression also occuring in the top octaves as well, which then would lead to reviewers in other mags talking about it sounding like the compressed Fr as opposed to the 2.83V FR.
I believe b-force is also Dutch ;-)
What i ment, why does the res-frequncy drop because of damping? What mechanism causes that?
Do you know if they checked to see if the amp was staying linear?
Oh, and were the tests of an actively driven driver alone, or thru a passive xover?
In all my test cases, I've known there was no amp limitation. And I have so much SPL headroom with the compression drivers I use, I quit burst testing at the very high end (plus I can't hear that high anyway!
But certainly, anyone interested in this should check the entire range.
Is there still the plan for versions without visible screws to become available for DIY (i.e. via rearmount)?
Here's an example. The publication I was thinking of was StoundStage! Hi-Fi
https://www.soundstagenetwork.com/i...&catid=77:loudspeaker-measurements&Itemid=153
I searched the internet ,waded through AI generated moors, only to find out that i always get as first the math. Then only some notion that friction slows the movement, thus the frequency.
In my envisioning of damping is that the counteracting force a damper creates is velocity dependent.
If this is true it just reduces the amplitude.
Friction on the other hand is what f.i. a brake does, and ultimately will reduce the frequency to 0 (zero).
Where am i missing something?
(It is off, but i just needed to get it out of my brain ;-))
Jan: yes. I have used a pilot tone either at a very low frequency or very high to trak the DC resitnace change and calculate the temperatur. From this, we can identify a thermal model.
Yes your math background helps! I used pink noise and white noise in LIMP(Imp meas app of Arta) and let it run while measuring time and noting impedance increase (Re ) .
A 10% increase of Re (3.1 to 3.4) was very quick , i recall 2 seconds, the DUT being a sb26adc. That was unfiltered.
On my checklist to put together a better and reproducable approach including filtered condition .
A 10% increase of Re (3.1 to 3.4) was very quick , i recall 2 seconds, the DUT being a sb26adc. That was unfiltered.
On my checklist to put together a better and reproducable approach including filtered condition .