vasyachkin said:
Hi,
Remember, Qts specifies driver total Q without box. Qtc specifies total Q with driver in closed box.
Yes, we need to look at it in a system perspective. That's why we have defined driver spec to use in our system calculations, alright low level ones. One has to take into account that "low level" parameters changes with power both in a short and long time time perspective .
Our discussion started when I questioned your sentence:
And I wanted to replace your "Large SD" with "low Cms".
You mentioned Qts, and that implies no box.
If I got it right:
Driver Qts = Qes || Qms
Where Qes = Re*Sqrt(Mms)/(BL^2*Sqrt(Cms))
And Qms = Sqrt(Mms)/(Rms*Sqrt(Cms))
As known, Qes is the dominant factor and will largely determine Qts.
If you have some other formula where SD is part of the Qts equation I am all ears.
4fun said:
you're right, instead of
"high Qts is merely a consequence of Large SD, high MMS and low BL^2/RE"
i should have said
Large SD, high MMS and low BL^2/Re in an average sized box will produce a response with a high Q
i did not expect it to be taken literally. i expected "high Qts" to be interpreted as "driver that will produce a high Q alignment" which is technically incorrect but i didn't think you would nitpick it like that
vasyachkin said:
because i didnt see MMS spec and why should i bother looking for it when QTS and VAS do not contradict my assumption
Mms can be calculated.
IMO (and probably others) these are the important T/S specs: Fs, Qes, Qms, Vas, Sd and Re. All of these can be measured or are readily available from the manufacturer. Knowing these, you can calculate everything else, including Mms, Cms, Bl, Qts and efficiency.
When you look at one number and assume the rest you end up with a poorly designed box.
4fun said:
this formula looks legit. it can be broken up into three parts.
1 - 1/(BL^2/Re)
2 - 1/Sqrt(Cms*Mms)
3 - Mms
the first one is a measure of motor strength (inverse of the square of it normalized by impedance)
second one is a measure of resonance frequency
third one is mass
--------
now above resonance frequency output is proportional to motor strength and inversely proportional to mass
at the exact resonance frequency the output is proportional to the resonance frequency and inversely proportional to motor strength
and Q is just ratio of output at resonance frequency to output above resonance frequency
therefore Q is proportional to (resonance frequency * mass / (motor strength^2))
--------
i just realized that the proper measure of motor force is BL/Sqrt(Re) ... i previously thought that its BL^2/Re but thats really the square of it ...
MJL21193 said:
which parameters are "important" is a moot point. most can be calculated from other ones and vice versa so it really doesn't matter.
the question is which parameters provide information in the form that that can be most readily used to judge the driver ?
to me those are SD, Bl^2/Re and Mms
because SD and Mms will determine resonance frequency of the box and as i outlined in the post above Q depends on BL^2/Re, Mms and resonance frequency ...
but its just a matter of preference - how you like to think. i happen to think that Mms is more fundamental than lets say Vas because mass is a concept widely used in physics and "equivalent volume of compliance" is not ...
i like to think in terms of physics of what is going on. i don't like to think in terms of formulas somebody else wrote using parameters they invented. i like to think in terms of parameters like mass and surface area because these are universal concepts in physics, not just limited to TS theory. TS theory i think should be used to help understand the physics behind driver operation, not as a crutch to avoid understanding them.
ok let me take a final stab at explaining why i like Sd, Mms and BL^2/Re
because not only can they predict the response of the driver in the box ... but i can predict them by just looking at the driver !
for example i think nobody should have any problem determining Sd of a driver by looking at it.
Mms can be inferred from things like cone material and thickness and size of voice coil
Bl^2/Re can be inferred from motor geometry and size
so basically you can just hold the driver in your hands and know what box it should be placed into.
now you may think this is not so useful but you can also do the opposite. instead of looking at the driver to see how it would perform in a box you can think of the performance you need and visualize ( in your mind's eye ) the driver that will deliver it. then you just pick a driver that looks like it and buy it (double check by modeling in software). the time savings could be dramatic ... instead of plugging 50 different drivers into unibox to see which one works you just go for the right one straight away.
this way of thinking could also be useful in designing drivers but unfortunately im not sure how to get into that business ...
because not only can they predict the response of the driver in the box ... but i can predict them by just looking at the driver !
for example i think nobody should have any problem determining Sd of a driver by looking at it.
Mms can be inferred from things like cone material and thickness and size of voice coil
Bl^2/Re can be inferred from motor geometry and size
so basically you can just hold the driver in your hands and know what box it should be placed into.
now you may think this is not so useful but you can also do the opposite. instead of looking at the driver to see how it would perform in a box you can think of the performance you need and visualize ( in your mind's eye ) the driver that will deliver it. then you just pick a driver that looks like it and buy it (double check by modeling in software). the time savings could be dramatic ... instead of plugging 50 different drivers into unibox to see which one works you just go for the right one straight away.
this way of thinking could also be useful in designing drivers
but unfortunately im not sure how to get into that business ...Chicho said:
i did not model your driver so i cant comment on the tuning ...
i will say though that you should allow enough room behind the vent for air to move. general recommendation i believe is to allow 1.5 times the port diameter in clearance. so for a 4" port that would be 6 inches clearance and your overall box would need to have a dimension of at least 17 + 6 = 23 inches ... which means the box could not be a cube but would have to be some other kind of shape ...
vasyachkin said:
because i didnt see MMS spec and why should i bother looking for it when QTS and VAS do not contradict my assumption
vasyachkin said:
You like it so much, you didn't bother to calculate it earlier. That's odd.
You don't like to use standard T/S specs. That's fine for you.
I like to do things the easy way if that's possible, and put more effort into things that are within my power to control, such as quality box construction after it has been properly designed.
No you can't, you just say arbitrarily that it needs to be smaller or bigger than speaker X, You cannot determine box requirements based on the parameters you keep saying are important.
No it can't! You should realize you are wrong by the fact that you are "inferring" based on appearances. You have no idea how thick and dense all of the parts are and what portion of the spider and surround contribute to the moving mass.
NO it can't, again you are inferring based on nothing, you have no idea about flux density or uniformity, you are just speculating.
Absolutely not, this is the most absurd comment yet!
Keyword... "Assumption"
Restore the output... Maybe if you tried learning the importance of T/S parameters you would understand the point of this. These parameter have been in use for decades because they work, all you do is arbitrarily compare a woofer to a "good woofer" whose box volume requirements were determined by T/S Parameters!
Are you one of those kids who just come on to forums trying to cause problems by being argumentative and denying the basics?
What is your goal here? I have yet to here any accurate statements from you.
nunayafb said:
He might not completely know what he's talking about, but he knows how to argue.
Arguing is good, because to do it effectively you need to either rely on what you know or take the time to "refresh" your memory by reseaching. This is good for all concerned.
He's making things marginally interesting.
MJL21193 said:
you and your calculations ...
if you wanted to know how fast a car is - would you calculate horsepower to weight ratio or press the gas pedal ?
there is a good joke about you.
Q - how can you tell if you have already put salt into the soup ?
A - if it conducts electrical current ...
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