Re: Re: Power compression
Peter, I was considering that already, but wouldn't like to give up dampening by the amp.
Maybe someone should invent - and file for patent
- a VC temp sensing amp.
Shouldn't be that difficult to measure permanantly and to compensate for.
Though this aproach would work for active systems only - no problem for me.
By the way, this same ugly powercomression story applies to audio-transformers just as well - more mass and surface but thats it - basically the same come and go of added resistance.
Earl do you have plots that show the temp dependant resistance of your material? In transformers you wouldn't have the problems of unstable equilibrium.
Greetings
Michael
Peter M. said:
Peter, I was considering that already, but wouldn't like to give up dampening by the amp.
Maybe someone should invent - and file for patent
- a VC temp sensing amp.Shouldn't be that difficult to measure permanantly and to compensate for.
Though this aproach would work for active systems only - no problem for me.
By the way, this same ugly powercomression story applies to audio-transformers just as well - more mass and surface but thats it - basically the same come and go of added resistance.
Earl do you have plots that show the temp dependant resistance of your material? In transformers you wouldn't have the problems of unstable equilibrium.
Greetings
Michael
I posted this at HTGuide....
because I don't have a PM for Nick McKinney.
question for Nick McKinney....
How far out (in months or years) is your Altec/Western Electric mid? I have been trying to figure out how to do a (large format) two way without using a compression driver and one of the alternatives I can up with was the Beyma TPL-150 on the TD-TPL horn....but your midrange/fullrange driver sounds awfully tempting.
Thank you,
chris_mercurio@hotmail.com
p.s. Thank you for the update on posting measurements and the like at the AE site. I understand about having a lot of irons in the fire.
because I don't have a PM for Nick McKinney.
question for Nick McKinney....
How far out (in months or years) is your Altec/Western Electric mid? I have been trying to figure out how to do a (large format) two way without using a compression driver and one of the alternatives I can up with was the Beyma TPL-150 on the TD-TPL horn....but your midrange/fullrange driver sounds awfully tempting.
Thank you,
chris_mercurio@hotmail.com
p.s. Thank you for the update on posting measurements and the like at the AE site. I understand about having a lot of irons in the fire.
Re: Re: Re: Power compression
Maybe it should sense and compensate for resistance instead of temp? But I am no expert, maybe its not worth it or even practical.
BTW, some types of stainless steels are said to be non magnetic, and yet is full of iron. Has anybody measured the magnetic properties of Earl Geddes`Cu/Ni?
(no, i`m not suggesting stainless steel VC wire)
Regards,
Peter
(not an expert on metalurgy or magnetics either)
mige0 said:
Peter, I was considering that already, but wouldn't like to give up dampening by the amp.
Maybe someone should invent - and file for patent
Shouldn't be that difficult to measure permanantly and to compensate for.
Though this aproach would work for active systems only - no problem for me.
By the way, this same ugly powercomression story applies to audio-transformers just as well - more mass and surface but thats it - basically the same come and go of added resistance.
Earl do you have plots that show the temp dependant resistance of your material? In transformers you wouldn't have the problems of unstable equilibrium.
Greetings
Michael
Maybe it should sense and compensate for resistance instead of temp? But I am no expert, maybe its not worth it or even practical.
BTW, some types of stainless steels are said to be non magnetic, and yet is full of iron. Has anybody measured the magnetic properties of Earl Geddes`Cu/Ni?
(no, i`m not suggesting stainless steel VC wire)
Regards,
Peter
(not an expert on metalurgy or magnetics either)
Re: Re: Re: Re: Power compression
Regarding the first concept, it's really a never ending battle. Like trying to empty water from a sinking ship with a spoon while there is a 4ft hole in the side. As the resistance goes up, the power delivered goes down. You could sense for this resistance rise and deliver more power, but that would only further heat the coil and resistance would rise more and more. The most practical method, and one that is possible right now is to simply remove as much heat as possible. This is what the Lambda TD motor does, that very few others do. This keeps the resistance as low as possible. Obviously a material that would have less change in resistance with temperature would create further benefit, but it just isn't practical right now.
As far as the Cu/Ni wire goes that Earl Geddes suggests, I don't believe it currently exists. I may be wrong. If it doesn't exist, it would be quite a large investment to have a minimum amount of custom wire made. As I have stated, people from the likes of JBL, EV, have looked into it and found it not practical. It's a lot of money to experiment with to run thousands of lbs of a custom wire to evaluate whether or not it can even be used when the theory alone suggests it wont' work well due to the nickel magnetic permeability.
A response I just got from Ceramawire mentions that the copper will oxidize and deteriorate with temperatures above 500F. In the 1950's Sylvania developed the nickel clad copper wire they use. The nickel does not have issues with deteriorating or oxidizing wat the higher temperatures. They are also experimenting with Tantalum wire. The drawback is that it only has about 20% of the conductivity of copper wire, or 50% of the conductivity of aluminum wire even. It's non-magnetic, but expensive, not very conductive, etc.
John
Peter M. said:
Maybe it should sense and compensate for resistance instead of temp? But I am no expert, maybe its not worth it or even practical.
BTW, some types of stainless steels are said to be non magnetic, and yet is full of iron. Has anybody measured the magnetic properties of Earl Geddes`Cu/Ni?
(no, i`m not suggesting stainless steel VC wire)
Regards,
Peter
(not an expert on metalurgy or magnetics either)
Regarding the first concept, it's really a never ending battle. Like trying to empty water from a sinking ship with a spoon while there is a 4ft hole in the side. As the resistance goes up, the power delivered goes down. You could sense for this resistance rise and deliver more power, but that would only further heat the coil and resistance would rise more and more. The most practical method, and one that is possible right now is to simply remove as much heat as possible. This is what the Lambda TD motor does, that very few others do. This keeps the resistance as low as possible. Obviously a material that would have less change in resistance with temperature would create further benefit, but it just isn't practical right now.
As far as the Cu/Ni wire goes that Earl Geddes suggests, I don't believe it currently exists. I may be wrong. If it doesn't exist, it would be quite a large investment to have a minimum amount of custom wire made. As I have stated, people from the likes of JBL, EV, have looked into it and found it not practical. It's a lot of money to experiment with to run thousands of lbs of a custom wire to evaluate whether or not it can even be used when the theory alone suggests it wont' work well due to the nickel magnetic permeability.
A response I just got from Ceramawire mentions that the copper will oxidize and deteriorate with temperatures above 500F. In the 1950's Sylvania developed the nickel clad copper wire they use. The nickel does not have issues with deteriorating or oxidizing wat the higher temperatures. They are also experimenting with Tantalum wire. The drawback is that it only has about 20% of the conductivity of copper wire, or 50% of the conductivity of aluminum wire even. It's non-magnetic, but expensive, not very conductive, etc.
John
Re: Different VC wire
For those who don't know, here is the information.
http://www.lowtherloudspeakers.co.uk/homeindex.html
John
badman said:
For those who don't know, here is the information.
http://www.lowtherloudspeakers.co.uk/homeindex.html
John
Re: Re: Re: Re: Re: Power compression
JohnE_J, no not exactly – its NOT that any working compensation circuit for VC temperature (=resistance) – variations would lead to a never ending VC heat up.
The energy you deliver for a certain piece of music is a fix amount calculated from SPL and speaker sensitivity. The variations of speaker sensitivity due to heat up at fortissimo would only translate to a slightly reduced average speaker sensitivity over that piece of music.
There always could be stable equilibrium ( ) acheaved for any given SPL with power compression compensation (same as with a current amp).
Sensing temperature varations by calculating the resistance over a RMS measurement of voltage and current shouldn't be a problem nowadays - incorporating a suitable temp sensor close to the VC neither
John_E_Janowitz said:
JohnE_J, no not exactly – its NOT that any working compensation circuit for VC temperature (=resistance) – variations would lead to a never ending VC heat up.
The energy you deliver for a certain piece of music is a fix amount calculated from SPL and speaker sensitivity. The variations of speaker sensitivity due to heat up at fortissimo would only translate to a slightly reduced average speaker sensitivity over that piece of music.
There always could be stable equilibrium (
) acheaved for any given SPL with power compression compensation (same as with a current amp). Sensing temperature varations by calculating the resistance over a RMS measurement of voltage and current shouldn't be a problem nowadays - incorporating a suitable temp sensor close to the VC neither
Re: Re: Re: Re: Re: Power compression
JohnE_J, no not exactly – its NOT that any working compensation circuit for VC temperature (=resistance) – variations would lead to a never ending VC heat up.
The energy you deliver for a certain piece of music is a fix amount calculated from SPL and speaker sensitivity. The variations of speaker sensitivity due to heat up at fortissimo would only translate to a slightly reduced average speaker sensitivity over that piece of music.
There always could be stable equilibrium ( ) acheaved for any given SPL with power compression compensation (same as with a current amp).
Sensing temperature varations by calculating the resistance over a RMS measurement of voltage and current shouldn't be a problem nowadays - incorporating a suitable temp sensor close to the VC neither.
Maybe it could even easier be done with suffcient effect.
Greetings
Michael
John_E_Janowitz said:
JohnE_J, no not exactly – its NOT that any working compensation circuit for VC temperature (=resistance) – variations would lead to a never ending VC heat up.
The energy you deliver for a certain piece of music is a fix amount calculated from SPL and speaker sensitivity. The variations of speaker sensitivity due to heat up at fortissimo would only translate to a slightly reduced average speaker sensitivity over that piece of music.
There always could be stable equilibrium (
) acheaved for any given SPL with power compression compensation (same as with a current amp). Sensing temperature varations by calculating the resistance over a RMS measurement of voltage and current shouldn't be a problem nowadays - incorporating a suitable temp sensor close to the VC neither.
Maybe it could even easier be done with suffcient effect.
Greetings
Michael
pdan said:
gedlee said:
The XT1464's are cheap enough that experiments with heavily textured paint, or even sand or bead-blasting, might be interesting. I've also wondered about "mouse fur" materials like microfiber fabric being glued to the interior of the horn - and I've seen thin layers of cork glued to the interior of the horn.
Time-domain measurements should reveal pretty quickly what works and what doesn't. The measurements of the most interest should be the "fringe" behavior at the edge of the polar pattern, where the horn is at its most ragged in time, frequency, and polar response domains. As Dr. Geddes mentions, though, the gains might be rather small.
P.S. Quick question for John & Nick - any FR or impulse measurements of the 15 vs 12-inch drivers? Curious minds want to know.
Re: I posted this at HTGuide....
As fast as the supplier can drop cones in my grubby paws. Could be 3 months if they are fast, could be more, its really out of my hands at the moment (which it has always been but now at least its within reach) Right now an original early 1950's cone is on the way to being analyzed for what it was made of to see if it can be duplicated down to the pulp mixture. The motor systems are easy and pretty much done (we will have a few options)
chrismercurio said:
As fast as the supplier can drop cones in my grubby paws. Could be 3 months if they are fast, could be more, its really out of my hands at the moment (which it has always been but now at least its within reach) Right now an original early 1950's cone is on the way to being analyzed for what it was made of to see if it can be duplicated down to the pulp mixture. The motor systems are easy and pretty much done (we will have a few options)
Lynn Olson said:
I don't have any here (a side note - I have been away from speaker building for about 4 years now and still unpacking stuff I placed in storage in 2004 when Lambda shut down) I am still trying to figure out where my mic went.........
I can say that the 15" sounds better in the midrange to my ears, its a common issue with pro style curvilinear coned drivers as these drivers are not the only ones to do this. Let me see what we can get done quickly. Would we want to see a M model or the higher excursion models like the X or H? I imagine a M accordion style if we are trying to mate to a horn.
Re: Re: Re: Re: Re: Re: Power compression
I remeber when I auditioned the Beolab 5 speakers some years ago. The b&o sales person told me that this kind of feature was incorporated in the speaker to keep it linear regardless of temperature. I dont know if its correct (after all he was a sales person). Anyone who has dissected a pair?
mige0 said:
I remeber when I auditioned the Beolab 5 speakers some years ago. The b&o sales person told me that this kind of feature was incorporated in the speaker to keep it linear regardless of temperature. I dont know if its correct (after all he was a sales person). Anyone who has dissected a pair?
Re: Re: Re: Re: Re: Re: Power compression
I have a friend who does that for his car audio sub/amp combos he hand builds to keep the woofer coils from burning in SPL events. Really its just a limiter as if the coil is hot there is nothing you can do with the input signal other than to lower it. IMHO its better to just wick the heat away as fast as possible.
mige0 said:
I have a friend who does that for his car audio sub/amp combos he hand builds to keep the woofer coils from burning in SPL events. Really its just a limiter as if the coil is hot there is nothing you can do with the input signal other than to lower it. IMHO its better to just wick the heat away as fast as possible.
Member
Joined 2003
Lynn,
Here are some shots of a BMS 4552ND on a 12" MSC waveguide from about a year ago.
First is a stock WG except that the back side (outside) is covered with a heavy layer of sand and polyester resin.
Next is the same driver & WG but with a sand texture created by spraying the inside of the WG with enamel and sprinkling dry sand into the wet paint. Virtually no difference, at least in the CSD.
Request for you... If/when you obtain the 18 Sound ND1460A, would you post a few photos of the phase plug? I've tentatively selected those drivers for a project about 3 months out, but hate to buy them without knowing what the phase plug actually looks like.
Thanks,
Paul