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Crashpc View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Crashpc Quote  Post ReplyReply Direct Link To This Post Posted: 29 March 2019 at 7:18am
My eye caught this claim:
 
"As i have said, the highest BL drivers are the worst. 180lit box is really too small to justify using a strong 21 inch in it."
 
When we revealed otherwise, it is not fair that it is 21" now hehe....
Just joking. The trend is obvious. All else being equal, higher Bl is a good thing.
If we put a single wire near the magnet, and Bl will be closer to 0, no doubt it will not play loud.
 
//EDIT
 
It might be, that at some point, resonant nature of weaker driver with loose suspension might win for part of the frequency range. That is good argument. Yet overall efficiency is more than that. And we don´t have an idea how these speakers behave with large signals, where things get very different.
Now, I prepared few sims and graphs, lets analyze 180l box, 32Hz tuning for all...
 
Dark blue:  21DS115
Light blue / cyan: 18DS115
Green: 18TLW3000
Red: 18SW100
 
 
Seems that 21DS115 is inferior and 18DS115 is in big trouble, right?
Now lets see strict 1W comparison:
 
Same colors. 21DS115 mostly leads the pack, 18SW100 and 18TLW3000 good, 18DS115 only good in 30-40Hz and 90-100Hz region, bad in 50-80Hz range. Why is that? Bl? Nope.
I would like to point out the 50Hz point. In first sim, it looks like 18DS115 struggles at 50Hz, yet in the second graph, it is on par with 18SW100 at 50Hz.
 
18TLW3000 has loose suspension with Qms of 13, While B&C is just over 4. That means less dampening, less backwards and restoring force, more sensitivity for TLW. Nothing to do with magnet. To prove that, I added Yellow - 18DS115 with still tighter than 18TLW suspension, but looser than original one. And again, stronger motor wins then. If I set the stiffness the same way, not to mention cone weight, it would trash 18TLW badly.
Yet it is only desired speaker, not existing one. 18TLW might be better choice for bassreflex box.
If box width is not issue, 21DS equipped with the same motor structure as 18DS still makes the cut...
For some reason, B&C does stiffer cones. That´s the one thing I do not understand.
There must be some reason for that....
 
You might spot, that there are differences between original graph in previous posts and this one. Yes. Different rounding of numbers, a lot of data - some small mistake here and there can be. Yet I believe there is no consistent mistake, that would influence all points in the frequency range...
 
Hope it was valuable response...
 
 
 
 
 


Edited by Crashpc - 29 March 2019 at 4:18pm
Nikon and Canon people should not be married to each other. Why did you let this happen?
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smitske96 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote smitske96 Quote  Post ReplyReply Direct Link To This Post Posted: 02 April 2019 at 11:56am
Great effort for showing the graphs Clap
For my personal project I went with the 18", the grills are just to cheap for not doing it.
I'll keep you updated!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Keen Quote  Post ReplyReply Direct Link To This Post Posted: 08 April 2019 at 10:55am
"Q is a measure of energy stored divided by energy dissipated, meaning that higher Q means more energy storage Wink "Dissipated energy" is loss"
Joachim Gerhard of Audio Physik
 
So high QMS is stiffer supspension.

21DS115 and 18DS115 are horn drivers, thick heavy cones, big motors, low damping (because the bass horn does the damping)

the others are more suited to reflex.

hth
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Keen Quote  Post ReplyReply Direct Link To This Post Posted: 08 April 2019 at 10:59am
It's a bit tricky getting your head around Q, I haven't yet, and I remeber lots of seemingly contradicting statements that only make sense once you learn more. 


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Crashpc Quote  Post ReplyReply Direct Link To This Post Posted: 08 April 2019 at 9:50pm
Eerr Low Q means high damping, not low....
It is also obvious from low voltage sensitivity 18DS115 has.
It is not a good idea to chase low Qs with no other reason in mind. Low Qs really can get to a point of being enemies, if rest of the setup isn't offseting it somehow. I take low Q drivers for better for very different reasons.


Edited by Crashpc - 08 April 2019 at 9:50pm
Nikon and Canon people should not be married to each other. Why did you let this happen?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote odc04r Quote  Post ReplyReply Direct Link To This Post Posted: 08 April 2019 at 10:11pm
Originally posted by Keen Keen wrote:

"Q is a measure of energy stored divided by energy dissipated, meaning that higher Q means more energy storage Wink "Dissipated energy" is loss"
Joachim Gerhard of Audio Physik
 
So high QMS is stiffer supspension.

21DS115 and 18DS115 are horn drivers, thick heavy cones, big motors, low damping (because the bass horn does the damping)

the others are more suited to reflex.

hth


Slightly the other way around I think unless my mind is wandering again. Q ~ (stored energy)/(energy lost per cycle) so comparing different systems with the same stored energy the one with the highest Q is losing the least energy per cycle. In case of suspension that would be a loose driver which has the least resistance to movement. You can also think of Q as proportional to the number of oscillating cycles it takes a system to lose its stored energy.

A stiff suspension driver that offered higher resistance to movement would have a comparatively lower Q value as it would dissipate the same stored energy in less cycles, because each one is performing more work.

Think of it is your large voice coil strong motor drivers are all low Q(es) because the strong motor makes them highly electrically damped. Same works for the mechanical damping which is often also seen in lower Cms and higher cone mass for lower Q(ms) drivers. And then all of this features into with Fs also.

Q is quite a mathematical abstract thing, but it directly relates to the linear coefficient term of 2nd order differential equations which are also the same reason people talk about alignments such as Butterworth etc.  All loudspeaker equivalent circuits can be simplified to a series of 2nd order equations working in parallel with each other.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote smitske96 Quote  Post ReplyReply Direct Link To This Post Posted: 08 April 2019 at 10:16pm
I've shortened the list to these two drivers:
18SW100
LF18N405

At the moment the 18TLW3000 is not worth the extra 400,- for four drivers.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Crashpc Quote  Post ReplyReply Direct Link To This Post Posted: 09 April 2019 at 5:16am
What drives this choice? I would be thinking between LF18N405 vs 18SW115 at that point  
Nikon and Canon people should not be married to each other. Why did you let this happen?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Keen Quote  Post ReplyReply Direct Link To This Post Posted: 09 April 2019 at 9:31am
Originally posted by odc04r odc04r wrote:

Originally posted by Keen Keen wrote:

"Q is a measure of energy stored divided by energy dissipated, meaning that higher Q means more energy storage Wink "Dissipated energy" is loss"
Joachim Gerhard of Audio Physik
 
So high QMS is stiffer supspension.

21DS115 and 18DS115 are horn drivers, thick heavy cones, big motors, low damping (because the bass horn does the damping)

the others are more suited to reflex.

hth


Slightly the other way around I think unless my mind is wandering again. Q ~ (stored energy)/(energy lost per cycle) so comparing different systems with the same stored energy the one with the highest Q is losing the least energy per cycle. In case of suspension that would be a loose driver which has the least resistance to movement. You can also think of Q as proportional to the number of oscillating cycles it takes a system to lose its stored energy.

A stiff suspension driver that offered higher resistance to movement would have a comparatively lower Q value as it would dissipate the same stored energy in less cycles, because each one is performing more work.

Think of it is your large voice coil strong motor drivers are all low Q(es) because the strong motor makes them highly electrically damped. Same works for the mechanical damping which is often also seen in lower Cms and higher cone mass for lower Q(ms) drivers. And then all of this features into with Fs also.

Q is quite a mathematical abstract thing, but it directly relates to the linear coefficient term of 2nd order differential equations which are also the same reason people talk about alignments such as Butterworth etc.  All loudspeaker equivalent circuits can be simplified to a series of 2nd order equations working in parallel with each other.


Hi odc04r, can you have a look at page 11 here:
https://www.klippel.de/fileadmin/klippel/Files/Know_How/Literature/Papers/Dynamical%20Measurement%20of%20Loudspeaker%20Suspension_Klippel.pdf

I'm reading it as: if losses of suspension parts are low, Qms is high. So if the suspension is losing nothing the QMS is infinite. Is it logical to then think a stiffer suspension is losing less, to its opposing force???

Many thanks
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Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 09 April 2019 at 9:32am
Just to throw a curveball, I may have some 21SW115 that I can do a pretty good price on...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote odc04r Quote  Post ReplyReply Direct Link To This Post Posted: 09 April 2019 at 5:17pm
Originally posted by Keen Keen wrote:


Hi odc04r, can you have a look at page 11 here:
https://www.klippel.de/fileadmin/klippel/Files/Know_How/Literature/Papers/Dynamical%20Measurement%20of%20Loudspeaker%20Suspension_Klippel.pdf

I'm reading it as: if losses of suspension parts are low, Qms is high. So if the suspension is losing nothing the QMS is infinite. Is it logical to then think a stiffer suspension is losing less, to its opposing force???

Many thanks
[/QUOTE]

The first part is right, if you have zero loss then QMS is infinite and if you were to excite the speaker then after you tool the signal away it would continue to move forever assuming no electrical losses. Think of a bell that rings for a long time when struck, that is a low loss high Q system.

When you model a speaker's mechanical side there is an inductor, resistor, and capacitor in parallel.  The inductor represents accelerating the speakers mass, the resistor represents the losses in the movement, and the capacitor represents the Cms of the driver which is the 'stiffness' as it defines how for the suspension wil move given an applied force. Because dispacing the suspension from its rest position stores energy (restoring force wants to go back to the centre) it behaves like a capacitor. So in the T/S modelling the stiffness of the suspension is considered seperate from the mechanical losses.

However in real common sense terms, you would consider that if a driver had high stiffness (low compliance) then your mechanical losses might also generally be higher. But not necessarily so...


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Keen Quote  Post ReplyReply Direct Link To This Post Posted: 10 April 2019 at 12:19am
thanks
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