Nice speakers Mattes. Have you tried mass on the mid/tweeter hanging there above the woofer?
I have complained to Picotech about the plots their software creates but they never answer any requests or suggestions. Great pc scopes but really poor service.
I have complained to Picotech about the plots their software creates but they never answer any requests or suggestions. Great pc scopes but really poor service.
Thanks! It use to be all over the net from various postings and now Google just gives me totally unrelated search items. 🙁
Understood, just wanted to get it back into circulation for box apps since relevant to the subject. 😉
Right, which is the whole point of what he's doing, i.e. 'critically' damping [crushing] the frame/baffle to give the motor, piston a stable work platform, same as what this DIYer did to [dis]prove my ~outlandish claims re the massive amounts needed to vertically mass load speakers: Audio Asylum Thread Printer
All this assumes a sufficiently rigid/massive foundation, so short of a concrete foundation it must be somehow isolated.
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After seeing the pressure screw described, I would say whatever basket/magnet structure vibration happening in "both directions" would ride on the DC bias of the pressure established by the screw.
Still no idea of what a realistic pressure to apply is, recognizing it's set by feel in GM's description. Like, if you put a load cell in the mechanical circuit, what would it read? I'm pretty sure if I stood on my 18" Goldwood 1858s, the basket would take all 185 lbs no problem; maybe not so for my 3" CHN-50s.
There's probably a way to calculate it, such that the push-pull of the vibration never exceeds the bias force - and perhaps a huge amount of force (what the basket could mechanically support w/o deformation) is ridiculous and unnecessary. Maybe it's only 10-20 lbs for a big driver, a couple / few for a small? Dunno -
Yes, if you know the structural properties of everything and how to calculate the vibration forces being applied.
Maybe adapt the added mass calcs for PR loading? https://www.diyaudio.com/forums/subwoofers/296305-wf-subwoofer.html#post4822582
Is it possible to use the shift in fs as an indication of how much mass or how tightly it is applied?
I do not think I am crushing Betsy's basket. The wool piece between the fram and basket is not that dense.
How much mass makes a difference? The point is to provide a rigid motor. The speaker cone and air has a known mass. The movement due to a dynamic input, say a kick drum, moves the cone/air mass at some acceleration. So we know the force that the motor is pushing. Well I dont but some physics major can calculate it easily.
Then we take the stock driver. It gives some rigidity due to its weight.
Then we take some mass, in my case about 3x the lone driver, and we should get an idea of the improvment in rigidity.
At some point the 'Mass Rigidity vs Cone Force Rigidity Improvment Factor' flattens out. Lets call this MRCFRIF for short.
I do not think I am crushing Betsy's basket. The wool piece between the fram and basket is not that dense.
How much mass makes a difference? The point is to provide a rigid motor. The speaker cone and air has a known mass. The movement due to a dynamic input, say a kick drum, moves the cone/air mass at some acceleration. So we know the force that the motor is pushing. Well I dont but some physics major can calculate it easily.
Then we take the stock driver. It gives some rigidity due to its weight.
Then we take some mass, in my case about 3x the lone driver, and we should get an idea of the improvment in rigidity.
At some point the 'Mass Rigidity vs Cone Force Rigidity Improvment Factor' flattens out. Lets call this MRCFRIF for short.
Why so complicated? How about just Cone Force Rigidity Improvement Factor or 'CoFoRIFa'?
Interesting, the way I see it is the "DC" push from the presumed grounded rear panel invests in shearing the front baffle and compressing the 'spring' which is the basket. These are both reactive forces and so if the magnet were to react with a certain frequency at least it could separate from the block at the back.
Of course but you have created a complicated system, can you separate these elements to work it out or must you rely on testing?
You answer a lot here...
Mass cannot be rigid no matter how much you use. It can only act in a superficially similar way to being rigid.
Your system is a little different to Scott's. Your driver stays with the baffle as it resonates, like many do, and the mass alters this resonance.
Everything is relative. The mass of cone+air is what? 15grams...?
The motor in stock form maybe 1000grams (I havent measured but will).
Even if speaker is hung free in space, no baffle to hold it, the mass motor to cone+air ratio is such that the cone +air is what moves.
Adding 3000grams just makes the motor / cone+air ratio even bigger so now the thing that really-really moves is the cone. Well I guess minutely if we are tiny cells we could see movement of the motor as well, but with the bigger mass it will be less.
Perhaps I misunderstand... are some of you saying the addition of mass is not a good idea? (This is not my idea that popped into being while taking a shower, I have seen it elsewhere, I think in some Japanese diy circles so I take no credit)
I'm not saying it's bad, just different.. and that's a good thing when you have control of it as you are doing.
Though the speaker frame moves less, it still invests against the baffle. The baffle resonance is always activated. Some of the energy is divested away to the baffle frequency. The mass is a part of the baffle, so lower frequency, and harder to get moving, but harder to stop moving as well. Damping is good.
Though the speaker frame moves less, it still invests against the baffle. The baffle resonance is always activated. Some of the energy is divested away to the baffle frequency. The mass is a part of the baffle, so lower frequency, and harder to get moving, but harder to stop moving as well. Damping is good.
Hi,
Thanks. The swinging mid-tweeter has a fieldcoil motor, and the ratio of moving weight (cone, coil, half of suspension and spider, plus air load) against total (mostly motor) mass is very good. The bass unit was more problematic, especially as the TSP provided by AE were foul, and Mms of the AE18 was much bigger than claimed. Here the extra weight was helpful and cleaned up the bass.
An impedance measurement system of decent quality would be quite helpful to determine at least a few of the effects you´re building into your arrangement of stiffening/extra weight/blocking vents, as resonances are normally easy to see in an impedance plot.
Good luck and all the best
Mattes