I really don’t understand why one tries to investigate the impedance curve for this by the way. Literally any microphone (and usable interface) enables you to check the acoustics at work and to judge whether a certain amount of damping will do. The burst decay analysis clearly shows what is there and should not. The level plot shows if bass tunings overshoot or not. Using the impedance for this is, well, so electrical.
Hi,
coffee time, pardon the daily philosophy 😀
some reasons come to my mind like isolating what anomalies are from the driver and what from the box interacting with it. Also room acoustics is somewhat isolated from the impedance graph. Perhaps compare impedance plot to frequency response for final assessment. How would you measure with mic, outside? close up? Impedance measurement seems more robust and faster method, more practical for some work like tuning the stuffing.
For total system damping, in the end like you say, all we care is the total system Q right? Correct me if I'm wrong, but as I've understood it Qts consists of Qms and Qes of the driver and they both reflect to the impedance graph. Besides of Qes of the driver any series impedance in the circuit like from cabling would add to it and the box would make into the Qms, into the impedance graph. Lets consider the electronic circuit and driver properties constant between measurements so while tuning damping inside the box so what one observes from impedance plots is the effect of the damping material to mechanical damping of the system. So I think impedance plot is one valid method to gauge whats happening when stuffing is changed as it shows change in mechanical damping directly.
The stuff can also be reasoned / derived without any measurements, at least to some extent. Expect various box simulators to give close enough estimates for system Q otherwise they would be useless. Expect to add at least some stuffing/damping material to any box which would affect the system Q, perhaps simulator took this into account. Besides tuning system Q with stuffing expect to have some panel resonances, expect cone resonances, expect standing wave, pipe resonance if ports and so on. These can be anticipated with tape measure and simple math and some of which can be addressed with the damping material while some cannot. If listening test says there is no problem then its probably fine enough for the listener, for the given application. Some kind of measurements would need to be there to be able to isolate and tune the details though, to really improve performance.
Most importantly, what ever means one uses to assess the performance and then makes some tuning / prototyping, its almost guaranteed way to better results than it would have been for first try. In this sense it doesn't matter what means one uses as long as one is capable of improving performance, what ever that is.
coffee time, pardon the daily philosophy 😀
some reasons come to my mind like isolating what anomalies are from the driver and what from the box interacting with it. Also room acoustics is somewhat isolated from the impedance graph. Perhaps compare impedance plot to frequency response for final assessment. How would you measure with mic, outside? close up? Impedance measurement seems more robust and faster method, more practical for some work like tuning the stuffing.
For total system damping, in the end like you say, all we care is the total system Q right? Correct me if I'm wrong, but as I've understood it Qts consists of Qms and Qes of the driver and they both reflect to the impedance graph. Besides of Qes of the driver any series impedance in the circuit like from cabling would add to it and the box would make into the Qms, into the impedance graph. Lets consider the electronic circuit and driver properties constant between measurements so while tuning damping inside the box so what one observes from impedance plots is the effect of the damping material to mechanical damping of the system. So I think impedance plot is one valid method to gauge whats happening when stuffing is changed as it shows change in mechanical damping directly.
The stuff can also be reasoned / derived without any measurements, at least to some extent. Expect various box simulators to give close enough estimates for system Q otherwise they would be useless. Expect to add at least some stuffing/damping material to any box which would affect the system Q, perhaps simulator took this into account. Besides tuning system Q with stuffing expect to have some panel resonances, expect cone resonances, expect standing wave, pipe resonance if ports and so on. These can be anticipated with tape measure and simple math and some of which can be addressed with the damping material while some cannot. If listening test says there is no problem then its probably fine enough for the listener, for the given application. Some kind of measurements would need to be there to be able to isolate and tune the details though, to really improve performance.
Most importantly, what ever means one uses to assess the performance and then makes some tuning / prototyping, its almost guaranteed way to better results than it would have been for first try. In this sense it doesn't matter what means one uses as long as one is capable of improving performance, what ever that is.
Last edited:
And then when the carefully adjusted Q, knee of the bass response, is within 0.5db from the simulation one brings the box into a room and the responses is off by 10db or more 😀 So I see stuffing being more important on dealing with any issues with the box other than system damping. The Q is almost meaningless as long as its in the ballpark, because of the room.
Oh, I think impedance plots do say something. Interpreting the acoustic (and that is relevant) consequences is another ballgame. And the room, well, it is relevant too, eh?
Plus, we do have an issue with Q. TSP are a small signal world. Not 100 or even 90dB at 30Hz and cone excursions of several mm. Not that it is irrelevant. But it's only a part of the truth we are hearing.
Finished my coffee, gonna get some more 😊
Plus, we do have an issue with Q. TSP are a small signal world. Not 100 or even 90dB at 30Hz and cone excursions of several mm. Not that it is irrelevant. But it's only a part of the truth we are hearing.
Finished my coffee, gonna get some more 😊
Oh yeah 🙂 and what to read from the impedance graph? And what to do about it? how to connect the stuff into perceived sound? What would over stuffing sound like for example? or a pipe resonance on a reflex port? mode inside the box? How the Q changes with the 100db output? and so on
Simplest reasoning without much knowledge on anything is to make sure there is no unwanted resonances in the system, blips in the impedance graph, and adjust the stuffing so that these get reduced. Blips that aren't affected by stuffing are from the driver most likely, some parts of moving assembly decoupling from the voice coil one way or the other, right? If the blips are on the pass band and cause some audible issue perhaps then swap the driver to something else. If the box needs to be filled full before blips get changed perhaps the box needs to be rethinked, dimensions adjusted. Perhaps port needs to be tuned and so on. Port needs to be measured with a mic I think, midrange issues leaking through aren't visible in the impedance plot I think.
extra cup out 😀
Simplest reasoning without much knowledge on anything is to make sure there is no unwanted resonances in the system, blips in the impedance graph, and adjust the stuffing so that these get reduced. Blips that aren't affected by stuffing are from the driver most likely, some parts of moving assembly decoupling from the voice coil one way or the other, right? If the blips are on the pass band and cause some audible issue perhaps then swap the driver to something else. If the box needs to be filled full before blips get changed perhaps the box needs to be rethinked, dimensions adjusted. Perhaps port needs to be tuned and so on. Port needs to be measured with a mic I think, midrange issues leaking through aren't visible in the impedance plot I think.
extra cup out 😀