"It would also be really tough to properly compare UNLESS you had identical drivers (excepting the magnets). (..the voltage would have to result in identical T/S param.s as well.)"
That was done @ RMAF last year.
Lowthers played the first day, factory magnets removed; replaced w/ field coil magnets for the next days.
I was too involved with the project, probably shouldn't be making comments, but a few hundred heard it, and I kept hearing comments, e.g. very noticable difference, much smoother, lowther shout gone...
I thought they sounded even (much) better after the show in FLHs.
I don't know if/when Jon is going to market that design, hopefully the Alpair budget version will be out soon.
hmm that sounds like a doable and worthwhile experiment, a pair of already converted drivers (new motors only) and a pair of originals, with colliberated TS Params, in similar enclosures. Any takers?
That was done @ RMAF last year.
Lowthers played the first day, factory magnets removed; replaced w/ field coil magnets for the next days.
I was too involved with the project, probably shouldn't be making comments, but a few hundred heard it, and I kept hearing comments, e.g. very noticable difference, much smoother, lowther shout gone...
I thought they sounded even (much) better after the show in FLHs.
I don't know if/when Jon is going to market that design, hopefully the Alpair budget version will be out soon.
Depends on the use and the voltage.
Plus they both vent to the front of the driver, so even it's use has less impact.Rommy (..and website) has *soooo* many things wrong.. (..and yet also a great many things correct.) If the heat isn't reaching the VC nor is effecting the force.. Then maybe.. BUT THAT's A LOT TO ASSUME **OVER TIME**. (..and note that there were no measurements provided to show that there were not any effects to the force of the magnet or the heating of the VC.. at least from the post I read.) If however if it *is* effecting either..
Heat build-up reaching the Voice Coil will alter the VC's resistence and result in thermal compression.. assuming the VC heats up enough.
Thermal compression can have any number of negative effects. Eff. goes down. Qe goes up. Depending on the loading freq. response will change. Eff. will be "blunted" with transients (..classical thermal compression), actually leading to transients that aren't as loud as they should be relative to the average. etc..
Now that isn't to say that someone might not *like* these effects.. THAT is a different topic. But it will be a "moving target" (or variable), and that most certainly *is* a disadvantage.
Basically if you want more resistance then get a high ohm VC.
When you use less current in the electro-magnet force drops and Qe and usually even Qm will rise (resulting in a higher Qts). The plate and pole are just continuations of the magnetic "circuit". How much flux they can handle is just another limiting factor in the electromagnet, the presence of carbon in either *lowers* the maximum amount of flux and it *might* also effect how the force lines react in the motor's gap. How much or how little the change is largely due to how much effect the field has on the coil (++). (++ referring to the total weight of the moving assembly and all the other resistances to motion the coil has.)
Now what is "optimal" is a matter of opinion. So many variables to the driver will undergo changes that even if we could agree on what sounds "optimal" it would still be dependent on the design. Freq. linearity near primary resonance is usually the goal.. with "critical damping" (..in a closed enclosure this is represented with Qtc, and a "critical" value typically around .7). If you want an Open Baffle ("free air") design then I believe Martin King suggests a driver's Qts value to be around 1.3-1.4. Of course while an increased Qe (..and therefor and increased Qts) may make for a more linear response, it doesn't mean that it will be more linear with respect to distortion (..either linear "decay" or non-linear distortion effects). In fact the opposite is almost always true - that distortion INCREASES with decreased damping (..and not just at, and nearing, the driver's primary resonance).
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OK, thanks for explaining that!
The Woofer gets the warmest. It is rear vented, and probably gets to 40 degC
The Supravox is front vented, but is also open baffle. At 12V DC, the motor does get warm, probably around 45 degC. However at the 5.4V I am currently running them at, they do not get above the ambient temperature!
Cheers
David
Depends on the use and the voltage.
The woofer is rear vented with a sealed dust cap.
Hope this isn't a double post, I don't know what happened to the first.
Field Coil speakers boast "No Blurring", because the fixed magnet produces a less defined reference for the coil magnetics, the small dynamics and short time constants become blurred. The field a coil produces has greater focus.
"Woody" sound is what the guitar player/amp fixers called it [after repairs and testing]. This Jensen came out of a Jantsen by Jensen organ, woody is as good a term to tag it with as any. And the note dynamics are indeed different and noticably clearly defined on the softer passages.
It may not be the highest performance by modern standards, and doesn't sound 'hot rodded' to even the smallest degree, but it is pure joy to play through and listen to, gold foil pickup on semi-hollow helps too.
FC explains some things such as 'old tone' guitar sounds, why that darn Jukebox had such an amazing clear sound, and how they helped theaters get known for amazing sound.
The filtercaps on the 1940's Mfr. I replaced, other than the JJ's it's old blackplates.
Peavey Scorpion has a bolt-off magnet, and would be a good candidate [maybe] for a FC, getting the magnet off is 3 bolts, I had one in the garage, I think it is still there.
Anyone familiar with the voltages on the FC, IIUC the field coil is a choke for the amplifier, and DC HV runs through it ? {I know that doesn't make sense for a coil generally but that's what I remember reading].
This Amplifier for the FC has one big transformer, apparently the speaker is the transformer and the transducer.
Questions:
What is the coil turns ratio between the voice and field coil
Is it theoretically possible to test the FC and VC with SS [LM3886's, LM3875] amplifiers? I have tube amps.
Yupp, would like to un-ceramic a little speaker and see if a FC can replace it.
Field Coil speakers boast "No Blurring", because the fixed magnet produces a less defined reference for the coil magnetics, the small dynamics and short time constants become blurred. The field a coil produces has greater focus.
"Woody" sound is what the guitar player/amp fixers called it [after repairs and testing]. This Jensen came out of a Jantsen by Jensen organ, woody is as good a term to tag it with as any. And the note dynamics are indeed different and noticably clearly defined on the softer passages.
It may not be the highest performance by modern standards, and doesn't sound 'hot rodded' to even the smallest degree, but it is pure joy to play through and listen to, gold foil pickup on semi-hollow helps too.
FC explains some things such as 'old tone' guitar sounds, why that darn Jukebox had such an amazing clear sound, and how they helped theaters get known for amazing sound.
The filtercaps on the 1940's Mfr. I replaced, other than the JJ's it's old blackplates.
Peavey Scorpion has a bolt-off magnet, and would be a good candidate [maybe] for a FC, getting the magnet off is 3 bolts, I had one in the garage, I think it is still there.
Anyone familiar with the voltages on the FC, IIUC the field coil is a choke for the amplifier, and DC HV runs through it ? {I know that doesn't make sense for a coil generally but that's what I remember reading].
This Amplifier for the FC has one big transformer, apparently the speaker is the transformer and the transducer.
Questions:
What is the coil turns ratio between the voice and field coil
Is it theoretically possible to test the FC and VC with SS [LM3886's, LM3875] amplifiers? I have tube amps.
Yupp, would like to un-ceramic a little speaker and see if a FC can replace it.
It it correct, but there is a whole lot more into it…
The problem is that the are NOT just simple continuations of the magnetic circuit, because the are magnetically nonlinear and they react differently when the field in the gap is stressed because of changing magnetic field from the voice coil. So back to my question – do you know how the metal parts around the gap behaves when they are not saturated (this is the condition when less magnet force is created when somebody use low voltage than optimal)?
Do you really think there is no difference between point (1) and point (2) in the graphic below??
http://www.postimage.org/image.php?v=PqzbOfr
And it is also a limiting factor with permanent magnets…
hii
I cried over the tube amps I built.. Now things are better and im getting back into hifi currently with some cheap but surprisingly good full range speakers, and a low end pioneer receiver from a yard sale. I WILL get another pair of alnico full ranges if it kills me.. maybe even neodymium..
Sealed Lead Acid
I cried over the tube amps I built.. Now things are better and im getting back into hifi currently with some cheap but surprisingly good full range speakers, and a low end pioneer receiver from a yard sale. I WILL get another pair of alnico full ranges if it kills me.. maybe even neodymium..
Sealed Lead Acid
O.k. so lets move some theory to practice. I have a chunk of 1.5" dia and a chunk of 4" dia gray iron on hand to turn the core and pole pieces with.
I have a vintage chart of Philco replacement field coils. Have spools of magnet wire.
How hard could it be?
Just need a basket, my preference would be a 8" .Cones, surrounds and voice coils can be had for cheap from matelectronics, so I think I will order some to see if they are suitable for a fullrange.
I have a vintage chart of Philco replacement field coils. Have spools of magnet wire.
How hard could it be?
Just need a basket, my preference would be a 8" .Cones, surrounds and voice coils can be had for cheap from matelectronics, so I think I will order some to see if they are suitable for a fullrange.
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Harlanov - please don't be "coy". If you have something to share, by all means share it.
I never said that the plate and pole were "simple" continuations of the magnetic circuit.
Nor is this:
"..do you know how the metal parts around the gap behaves when they are not saturated (this is the condition when less magnet force is created when somebody use low voltage than optimal)?"
-a question you have asked before. You previously asked:
"..could you explain what happens when you use less than optimal current to get higher Qes? Do you know how your pole pieces behave under that particular condition??"
This isn't Roman's forum.
If you have first hand knowledge, or even a theory - feel free to share it and I *might* respond (..and others might as well). But leading questions are wastes of time.
It was meant for post #6 the original thread poster asked a second set of questions which was receiving no answers in the thread.I think it was meant for another thread.
Scott, I asked you those questions because using field coil driver at low voltage (to get higher Qes) leads to specific distortion caused by nonlinear behavior of the steel in the magnetic contour (you can see it in graphic I already posted). So one cannot just regulate driver’s Qts with lowering the voltage. There is ONLY one optimal working voltage for each driver.
И да хапваш повечко козунак за Великден, гевреций
И да хапваш повечко козунак за Великден, гевреций
This is a good point. As you run the material up to saturation,
the ac permeability is reduced dramatically and the field becomes
more "stiff" and has less distortion.
So with that in mind would it be best to try keep the mass in the pole pieces and core down to insure that the coil can provide enough of a field to reach saturation? My first inclination was to go for maximum mass but I really don't want to use enough copper to reach to the moon and back.
There is likely to be an optimum relationship between the two.
There is likely to be an optimum relationship between the two.
This is a good point. As you run the material up to saturation,
the ac permeability is reduced dramatically and the field becomes
more "stiff" and has less distortion.
It is a good point.. but I don't think there is a set "optimal" voltage - at least for the purposes of loudspeaker driver operation.. At some point the variation is minor (..and perhaps insignificant). The manufacturer shouldn't be advising a voltage range that significantly deviates from this.
Carbon content in the pole or plates will reduce magnetic saturation (..even over time - i.e. slow "warm up"), but for the most part "working" ranges will push very close to the saturation point.
Still, the total amount of flux the pole and plates can "carry" is the primary consideration. The higher the flux, the higher the force in the gap, the less distortion. (..and likely, the larger the working/linear range near saturation.)
What gets me is that no one seems to be trying out amorphous materials (..except for higher powered MRI's of course.) Capable of high flux, quick to saturate, and quick to loose permanence. Ok.. so they would be fragile.
Not difficult to *manufacture*.
It's all layer-based design (stacked lamination) to keep costs low. (..Metglass is one of the largest.) Water-jet cut to spec, assemble and place in a mold (with releasing agent), add appropriate resin and let cure. Do it with pole and plates as well.
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