You can easily obtain around 2T in the gap if you reduce it to 1mm and max height around 6-7mm.
Hello, I scanned all 43 pages of this thread. Very interesting. I am in the process of building a set of converted 6 1/2" Isophone alnico speakers to field coil using the same method shown in this video of a converted Diatone P610. I'm just waiting for my 30mm diameter mild steel bar to replace the magnets with and then ill wind new field coils for them. For estimating wire gauge, and supply voltage, has anyone tried this calculator from Accel Instruments? Some values are just guesses but some are not, and it is a good starting point. I can keep the field coil dimensions the same and vary the wire gauge to see what it does to an arbitrary magnetic field. Arbitrary because we are not calculating a solenoid, but a magnetic circuit in a speaker motor and the permeability factor is just a guess. I repeat the permeability factor is just a guess, and can really be any non-zero number. The results can be used for comparison to one another, but not for definitive answers. Inputting the field coil inner radius, length, and wire gauge will give you a calculated coil height. Excellent when you're dealing with a fixed space. I tried many wire gauges and I think I've settled on 24awg copper and a 9V supply. This results in an estimated 1280 winds, 0.575 Amps, dissipating 5.175 watts. All this is experimental and certainly won't deliver a state-of-the-art product but for the cost, it's an awesome way to get started.
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Hi,
Sorry to disagree. bottlenecks are steel permeability and core dimension first, then magnet power and gap width. Height is not that important for T, but of course for final design.
Depending of what type and size of driver you make, 1mm airgap width could lead to problems.
And you can´t do 2T with "ordinary" low-C steel, you´ll need exotic (and expensive) materials.
In the end, the result must be measured in reality...
Sorry again, no offence intended. But I have made and measured my Pure Iron motors, and my metal guy still complains about the material...
There are a lot of theoretical thoughts which tend to become more and more problematic when transferred into reality (a quick example: of course you can design a voicecoil with a 0,1mm Kapton former and a single layer of 0,2mm wire. Make the clearance 0,1mm to both sides, and you have a 0,5mm airgap with only a small loss of the available magnetic power. Good luck in building...).
Of course, if you have a motor with a 7mm x 1mm airgap with 2T in the middle of the gap, I´d love to learn how you did it!
All the best
Mattes
I would also tend to believe that a 2T field strength is a borderline bragging right than a real goal. A stronger manet is almost always nice to have, but people in this thread have already been able to get a full range response with ample sensitivity.
It's probably better to get something built and tweak the design as far as it can go before worrying about improving the field strength.
It's probably better to get something built and tweak the design as far as it can go before worrying about improving the field strength.
Hi,
Yes, you´re right.
And even if you have made a motor with 2 T in the middle of the airgap, where would that lead to? If the rest of your driver is well designed and is able to actually use the power provided (there are drivers around with gigantic motors and claimed qts of around 0,3, so where is the power? Gone somewhere underway), then you will have a very low qe and resulting qts, so the driver will hardly make any bass and will not have a linear response.
My motors have 1,54 T in the airgap (which was only possible with Pure Iron and a custom-made N52 magnet) and the drivers have a qts of 0,13. This is the borderline of being unusable for any bass, and the rising response makes the drivers hardly useable without correction.
Now I see claims of 2,4 T in the airgap (which is physically not possible without the use of cryo superconductors), where would that lead to???
A good fullrange or widerange driver is the sum of many parts and design choices and compromises, and the motor is only a part of it. Depending on your general concept, a motor providing something between 1 and 1,5 T in the airgap is a fine thing. And many motors of commercially successful drivers have even lower values.
Yes, build and tweak. And also measure what you really have.
All the best
Mattes
Yes, you´re right.
And even if you have made a motor with 2 T in the middle of the airgap, where would that lead to? If the rest of your driver is well designed and is able to actually use the power provided (there are drivers around with gigantic motors and claimed qts of around 0,3, so where is the power? Gone somewhere underway), then you will have a very low qe and resulting qts, so the driver will hardly make any bass and will not have a linear response.
My motors have 1,54 T in the airgap (which was only possible with Pure Iron and a custom-made N52 magnet) and the drivers have a qts of 0,13. This is the borderline of being unusable for any bass, and the rising response makes the drivers hardly useable without correction.
Now I see claims of 2,4 T in the airgap (which is physically not possible without the use of cryo superconductors), where would that lead to???
A good fullrange or widerange driver is the sum of many parts and design choices and compromises, and the motor is only a part of it. Depending on your general concept, a motor providing something between 1 and 1,5 T in the airgap is a fine thing. And many motors of commercially successful drivers have even lower values.
Yes, build and tweak. And also measure what you really have.
All the best
Mattes