November 20th, 2017, 7:45 pm
chris1973 wrote:Roscoe Primrose wrote:Cogito wrote:Thanks Tom and Walt.
The box calculations based on T/s parameters seem to be an approximation under some "assumed" conditions. By that I mean, there doesn't seem to be any allowance for
1. Input power
Bassbox says you can put 100 watts in there and not exceed Xmax. I don't know if you know what 100 watts is, but 100 watts is a lot of power!
November 20th, 2017, 7:47 pm
chris1973 wrote:So, I'm not sure about what the engineers say about this:
My information defines fc as the box resonance, and f3 as the low end rolloff.
From this I would assume that if fc is above f3, it is a competing signal with the bandwidth of information the driver is supposed to be faithfully reproducing in a flat manner, hence detrimental to the performance of the system.
However, if fc is belowb f3, the resonance is producing gain in a place where you are losing gain from the natural rolloff of the system, and therefore might be beneficial in extending the low end response of the system altogether.
Chris
November 23rd, 2017, 6:40 pm
Roscoe Primrose wrote:Cogito wrote:Thanks Tom and Walt.
The box calculations based on T/s parameters seem to be an approximation under some "assumed" conditions. By that I mean, there doesn't seem to be any allowance for
1. Input power
Not relevant. Performance should be independent of power until you run out of linear excursion or the voice coil gets hot enough to create power compression.
Roscoe
The Thiele-Small (T-S) parameters now provided on every driver datasheet do not provide insight into how drivers perform when the music is pumping and the drivers are required to produce a lot of output. Loudspeaker drivers are messy devices, producing more distortion than the rest of the audio signal chain combined. The T-S parameters do not capture any of that messy behavior or provide insights into whether one driver will have cleaner performance than another.
...
...
One key limitation of the T-S parameters is that they are “small signal” parameters, which means that they accurately capture the performance of the loudspeaker at low output volume. Further, the parameters have fixed values. They do not change for the driver based on different input levels. This is not indicative of the mechanical reality of drivers, where the electromechanical parameters of loudspeakers change during a gig.
For example, loudspeakers are bad at turning electricity into sound and the remaining electrical energy is dissipated as heat. This heat raises the temperature of the driver voice coil and magnet structure. As the voice coil temperature rises, physics dictates that the voice coil wire does not conduct as effectively, and this causes the driver voice coil resistance to increase. The thermal change in the driver results in a shift to multiple T-S parameters. This shift is not quantified by the numbers on the datasheet, which were probably measured at room temperature.
November 23rd, 2017, 7:56 pm
tomp wrote:chris1973 wrote:So, I'm not sure about what the engineers say about this:
My information defines fc as the box resonance, and f3 as the low end rolloff.
From this I would assume that if fc is above f3, it is a competing signal with the bandwidth of information the driver is supposed to be faithfully reproducing in a flat manner, hence detrimental to the performance of the system.
However, if fc is belowb f3, the resonance is producing gain in a place where you are losing gain from the natural rolloff of the system, and therefore might be beneficial in extending the low end response of the system altogether.
Chris
CHris:
What is Fc? I have never seen that in a list of TS parameters. Thanks.
November 23rd, 2017, 8:06 pm
November 23rd, 2017, 8:21 pm
November 24th, 2017, 10:01 am
Cogito wrote:Roscoe Primrose wrote:Cogito wrote:Thanks Tom and Walt.
The box calculations based on T/s parameters seem to be an approximation under some "assumed" conditions. By that I mean, there doesn't seem to be any allowance for
1. Input power
Not relevant. Performance should be independent of power until you run out of linear excursion or the voice coil gets hot enough to create power compression.
Roscoe
Roscoe,
Right on, but this article also says, performance can vary when played loud, within in the limits of the speakers T/s parameters.
http://www.fohonline.com/ci/31-tech-feature/12614-klippel-plots-going-beyond-the-thiele-small-parameters.htmlThe Thiele-Small (T-S) parameters now provided on every driver datasheet do not provide insight into how drivers perform when the music is pumping and the drivers are required to produce a lot of output. Loudspeaker drivers are messy devices, producing more distortion than the rest of the audio signal chain combined. The T-S parameters do not capture any of that messy behavior or provide insights into whether one driver will have cleaner performance than another.
...
...
One key limitation of the T-S parameters is that they are “small signal” parameters, which means that they accurately capture the performance of the loudspeaker at low output volume. Further, the parameters have fixed values. They do not change for the driver based on different input levels. This is not indicative of the mechanical reality of drivers, where the electromechanical parameters of loudspeakers change during a gig.
For example, loudspeakers are bad at turning electricity into sound and the remaining electrical energy is dissipated as heat. This heat raises the temperature of the driver voice coil and magnet structure. As the voice coil temperature rises, physics dictates that the voice coil wire does not conduct as effectively, and this causes the driver voice coil resistance to increase. The thermal change in the driver results in a shift to multiple T-S parameters. This shift is not quantified by the numbers on the datasheet, which were probably measured at room temperature.
November 24th, 2017, 10:36 am
chris1973 wrote:tomp wrote:chris1973 wrote:So, I'm not sure about what the engineers say about this:
My information defines fc as the box resonance, and f3 as the low end rolloff.
From this I would assume that if fc is above f3, it is a competing signal with the bandwidth of information the driver is supposed to be faithfully reproducing in a flat manner, hence detrimental to the performance of the system.
However, if fc is belowb f3, the resonance is producing gain in a place where you are losing gain from the natural rolloff of the system, and therefore might be beneficial in extending the low end response of the system altogether.
Chris
CHris:
What is Fc? I have never seen that in a list of TS parameters. Thanks.
Fc is box resonance as defined by Vance Dickason in the LDC. it's Qtc x fs over Qts
November 24th, 2017, 10:49 am
chris1973 wrote:This all brings up another issue I didn't understand until I had an amplifier with meters on it.I would hope somebody else chimes in on the issue:
We buy speakers that have 100-200 watt capability, and a lot of us buy amplifiers that can exceed 100-200 watts, but depending on your speakers, your actual listening level probably starts hurting before you reach 50-60 watt peaks. Despite this we still seem to think those 200watt specifications, and 110+db simulations we get from them, are of any practical importance.
November 28th, 2017, 6:55 pm