This all sounds pretty cool to me, I also like to experiment with modifying woofers (e.g. adding extra magnets to lower the qts and to get higher SPL, or removing the dustcap and placing a Aluminium phase plug to cool the voicecoil to increase powerhandling)
The grease thing sounds worth trying, but there is only one thing that concerns me. The Qms is related to the Rms (mechanical resistance), the higher the Qms the lower the Rms. The thing is, loudspeakers that produce a clear and precise bass all have a LOW Rms. So in this (the grease) case I see a dramatic lowering of the Qms so a higher Rms is the result. This will give you a "muddier" bassresponse.
The grease thing sounds worth trying, but there is only one thing that concerns me. The Qms is related to the Rms (mechanical resistance), the higher the Qms the lower the Rms. The thing is, loudspeakers that produce a clear and precise bass all have a LOW Rms. So in this (the grease) case I see a dramatic lowering of the Qms so a higher Rms is the result. This will give you a "muddier" bassresponse.
Posted by bombardon73:
... So in this (the grease) case I see a dramatic lowering of the Qms so a higher Rms is the result. This will give you a "muddier" bassresponse.
Rms - "This parameter represents the mechanical resistance of a driver’s suspension losses. It is a measurement of the absorption qualities of the speaker suspension and is stated in N*sec/m."
http://www.the12volt.com/caraudio/theile.asp
No offence meant, from my EE days, for a parallel-type circuit (RLC), of which the spider is approximately a mechanical equivalent (the bell curve impedance at Fs exhibits a parallel type of resonant circuit), lowered Q, with L and C constant, means lowered R.
i.e, for the spider, it is absorbing more kinetic energy and converting it to heat due to lowered resistance (V^2/R, remember?). This is called damping, albeit mechanical type of damping, as a result of lower Rms.
So, for the case where grease is applied to the spider, Rms really decreased. When Rms is lowered, since it forms part of a parallel resonant system, the resulting Q(ms) decreases. Also from the data I gave, R1 which is a composite of all the R's in the system (execpt Re), decreased after applying grease.
So, muddier? no. Maybe less boomy. It's in the comparative FR plot in the first few posts.
...
What do you think guys... I am not going to patent this thing since this is only a discovery and this may have already been used in the past.
But the data is there. Optimum vented box volume, which is dependent on Qts (which in turn depends to some degree on Qms (Qts = Qes||Qms) raised to the power of 2.87, decreases when grease is applied to the spider.
Now I come to the harder part - the woodworking...
... So in this (the grease) case I see a dramatic lowering of the Qms so a higher Rms is the result. This will give you a "muddier" bassresponse.
Rms - "This parameter represents the mechanical resistance of a driver’s suspension losses. It is a measurement of the absorption qualities of the speaker suspension and is stated in N*sec/m."
http://www.the12volt.com/caraudio/theile.asp
No offence meant, from my EE days, for a parallel-type circuit (RLC), of which the spider is approximately a mechanical equivalent (the bell curve impedance at Fs exhibits a parallel type of resonant circuit), lowered Q, with L and C constant, means lowered R.
i.e, for the spider, it is absorbing more kinetic energy and converting it to heat due to lowered resistance (V^2/R, remember?). This is called damping, albeit mechanical type of damping, as a result of lower Rms.
So, for the case where grease is applied to the spider, Rms really decreased. When Rms is lowered, since it forms part of a parallel resonant system, the resulting Q(ms) decreases. Also from the data I gave, R1 which is a composite of all the R's in the system (execpt Re), decreased after applying grease.
So, muddier? no. Maybe less boomy. It's in the comparative FR plot in the first few posts.
...
What do you think guys... I am not going to patent this thing since this is only a discovery and this may have already been used in the past.
But the data is there. Optimum vented box volume, which is dependent on Qts (which in turn depends to some degree on Qms (Qts = Qes||Qms) raised to the power of 2.87, decreases when grease is applied to the spider.
Now I come to the harder part - the woodworking...
posted by Depth charge:
I 've been thinking a bit about mechanical dampening since I read the fantastic thread called "Current Driven Loudspeakers and Tranconductance Amplifiers". I thought it might be a good idea to put a more viscous version of ferro fluid in the magnetic gap (perhaps someone could come up with a ferro grease?), which is what I thought you might be referring to in the title of this thread. Obviously not, but do you think it would help reduce the Qms much?
I think this is done on tweeters - ferro fluid, and on magnetic gap only. The ferro increases the Bl in the gap, and only in the gap because a tweeter has no spider. But still it is damping, both electromagnetic and mechanical. It is a nasty habit of tweeters, its ringing at Fs, and any form of damping is beneficial.
For any speaker, damping is helpful, and your more viscuous ferro-fluid will do the job too. In fact, i think that the ideal speaker is a zero Qms, high Qes speaker, i.e, VC and magnet encounters more frictional resistance than springy resistance, to their motion. The springiness should only be there to restore the cone to zero-x during no-signal condition, and the frictional losses sufficiently overcome by VC + magnet (Qes). Then it will not be muddy (more frictional resistance) and also not boomy (more springy resistance). So maybe this is what planars/ribbons naturally do?
I 've been thinking a bit about mechanical dampening since I read the fantastic thread called "Current Driven Loudspeakers and Tranconductance Amplifiers". I thought it might be a good idea to put a more viscous version of ferro fluid in the magnetic gap (perhaps someone could come up with a ferro grease?), which is what I thought you might be referring to in the title of this thread. Obviously not, but do you think it would help reduce the Qms much?
I think this is done on tweeters - ferro fluid, and on magnetic gap only. The ferro increases the Bl in the gap, and only in the gap because a tweeter has no spider. But still it is damping, both electromagnetic and mechanical. It is a nasty habit of tweeters, its ringing at Fs, and any form of damping is beneficial.
For any speaker, damping is helpful, and your more viscuous ferro-fluid will do the job too. In fact, i think that the ideal speaker is a zero Qms, high Qes speaker, i.e, VC and magnet encounters more frictional resistance than springy resistance, to their motion. The springiness should only be there to restore the cone to zero-x during no-signal condition, and the frictional losses sufficiently overcome by VC + magnet (Qes). Then it will not be muddy (more frictional resistance) and also not boomy (more springy resistance). So maybe this is what planars/ribbons naturally do?
... signing off guys, be away for the weekend.
will read your replies / thoughts on Monday.
P.S I plan to damp the large s-curve between 1 kHz and 2 kHz on the nearfield FR plot this weekend. Initial suspect is the basket resonance (helmholtz dip?). Any ideas about the dip, and what I can do to remove it? Many thanks in advance!
will read your replies / thoughts on Monday.
P.S I plan to damp the large s-curve between 1 kHz and 2 kHz on the nearfield FR plot this weekend. Initial suspect is the basket resonance (helmholtz dip?). Any ideas about the dip, and what I can do to remove it? Many thanks in advance!
If the basket is questionable, you may try some sound-absorbing material in the space between spider & cone back.
I've tried some long fiber wool in my 7" Focal midrange & got a slightly cleaner upper-mid to lower-hi.
If the "spokes" of the basket are wide, you may also try some higher density felt on them, in the inner side.
Since your spider is greased, I supposed the latter would be better, less messy.
I've tried some long fiber wool in my 7" Focal midrange & got a slightly cleaner upper-mid to lower-hi.
If the "spokes" of the basket are wide, you may also try some higher density felt on them, in the inner side.
Since your spider is greased, I supposed the latter would be better, less messy.
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