To help determine which driver will work is the reason that Dan Wiggins (Adire) published the math to aid in the selection of the appropriate driver.
Best Regards,
TerryO
If, through being overdriven, dropped (shock) or just exposed to heat the alnico loses it magnetism, the role of the magnet can be substancially altered and allow for more sag. It may not be be enough to require replacement, but the problem can be present.
Best Regards,
TerryO
we appear to be misunderstanding.
Sendler asks will it just keep on sagging with time.
You say it will not sag (presumably with time) except when it's Alnico.
Your "explanation" does not explain why non Alnico will not sag but Alnico will sag.
It has little if anything to do with abuse. The formula does not have a factor to take account of abuse !
"To help determine which driver will work is the reason that Dan Wiggins (Adire) published the math to aid in the selection of the appropriate driver."
The formula does not consider time, or deterioration of the spider (stretching, getting softer, etc).
I made 24 of these in 1988. The cones are very light, and the spiders are very stiff. Ask me if sag is a problem.
http://i56.photobucket.com/albums/g196/dkleitsch/COE08-3.jpg
The formula does not consider time, or deterioration of the spider (stretching, getting softer, etc).
I made 24 of these in 1988. The cones are very light, and the spiders are very stiff. Ask me if sag is a problem.
http://i56.photobucket.com/albums/g196/dkleitsch/COE08-3.jpg
The formula relies on fairly fixed parameters, which in the case of Alnico can't be assumed to remain constant over time. I'm not sure why anyone would bother using an alnico based driver in an up or downfiring configuration in the first place.
The formula Dan posted, was to aid those who had asked if a driver they already had was suitable for a downfiring orientation, it certainly wasn't to calculate the remaining life expectancy in marginal cases, like Alnico motors that need to be remagnetized.
However, use whatever you like...
Best Regards,
TerryO
Up firing
I guess up firing might be a bit safer than down firing as any brief over excursion would tend to be stopped by the back plate rather than over stretching the spider outward. Not as conveient or safe for the cone to have it where things can fall right onto it but worth consideration.
I guess up firing might be a bit safer than down firing as any brief over excursion would tend to be stopped by the back plate rather than over stretching the spider outward. Not as conveient or safe for the cone to have it where things can fall right onto it but worth consideration.
"?"which in the case of Alnico can't be assumed to remain constant over time."
Makes no sense at all as the sag occurs under no signal conditions. The only things that enter into the equation are mass and the suspension stiffness. What source the magnetism comes from doesn't enter into it at all.
" I guess up firing might be a bit safer than down firing as any brief over excursion would tend to be stopped by the back plate rather than over stretching the spider outward. Not as conveient or safe for the cone to have it where things can fall right onto it but worth consideration."
I think not.
The spider will still take a set and oilcan.
It does take an extended amount of time, so keep an eye on it and flip it as needed.
Makes no sense at all as the sag occurs under no signal conditions. The only things that enter into the equation are mass and the suspension stiffness. What source the magnetism comes from doesn't enter into it at all.
" I guess up firing might be a bit safer than down firing as any brief over excursion would tend to be stopped by the back plate rather than over stretching the spider outward. Not as conveient or safe for the cone to have it where things can fall right onto it but worth consideration."
I think not.
The spider will still take a set and oilcan.
It does take an extended amount of time, so keep an eye on it and flip it as needed.
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I know what you're saying about the spider and that's certainly a factor over time. Dan's formula was intended to help decide if a driver was a good (or bad) candidate for a down firing configuration.
The use of Alnico was just a subject discussed by Dan and I over lunch a few years back and is really a non-issue in the context of this discussion.
Best Regards,
TerryO
Bumped back plate
Do the Dayton RSS subs have any type of mech limit on the outward motion such as the back plate does for the the inward stroke? If not, having the driver firing upward so that the sag would always cause the motion to be limited by a bumped back plate that is made to be hit would actually be much better than firing downward where any over excursion would continually stretch the spider more and more.
Do the Dayton RSS subs have any type of mech limit on the outward motion such as the back plate does for the the inward stroke? If not, having the driver firing upward so that the sag would always cause the motion to be limited by a bumped back plate that is made to be hit would actually be much better than firing downward where any over excursion would continually stretch the spider more and more.
Maybe, unless the driver was intentionally designed so that it could be used in a downfiring configuration.
Best Regards,
TerryO
Not recommended
Parts Express says the RSS subs are not really recommended for down firing but I am going to try it anyway. If I ruin the driver I will buy another one and do something else. The packaging of an upfiring sonotube is a much more effective use of footprint in my already crowded room and it will get even tighter if I end up with 15" H frames for the bass. The RSS315HF models best into 4.3cuft ported at 21Hz and tubes are so much more elegant looking and easier to build than a refrigerator sized box. And cheaper. The RSS390 models even better but needs at least 7ft and can tune to 15Hz with realy minimal group delay but I wonder about the 380mms being quick enough to keep up with music. The 12" sub is only 180gr mms.
Parts Express says the RSS subs are not really recommended for down firing but I am going to try it anyway. If I ruin the driver I will buy another one and do something else. The packaging of an upfiring sonotube is a much more effective use of footprint in my already crowded room and it will get even tighter if I end up with 15" H frames for the bass. The RSS315HF models best into 4.3cuft ported at 21Hz and tubes are so much more elegant looking and easier to build than a refrigerator sized box. And cheaper. The RSS390 models even better but needs at least 7ft and can tune to 15Hz with realy minimal group delay but I wonder about the 380mms being quick enough to keep up with music. The 12" sub is only 180gr mms.
Did you understand what I meant by oil-canning?
The spider sags and takes a set in the sagged position. When a signal comes in it causes the cone to move, but it can't move smoothly because of the set in the position. It ends up suddenly shooting through the set position and making a big uncontrolled motion rather than a small controlled motion. Running the signal up and down smoothly causes lots of jerky motions, rather than a smooth increase and decrease or cone motion. At some drive levels the cone can dive into the chassis, or a few volts higher jump out of the chassis, all while moving back-and-forth a fraction of an inch.
The spider sags and takes a set in the sagged position. When a signal comes in it causes the cone to move, but it can't move smoothly because of the set in the position. It ends up suddenly shooting through the set position and making a big uncontrolled motion rather than a small controlled motion. Running the signal up and down smoothly causes lots of jerky motions, rather than a smooth increase and decrease or cone motion. At some drive levels the cone can dive into the chassis, or a few volts higher jump out of the chassis, all while moving back-and-forth a fraction of an inch.
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