Im trying to understand when consider we are using a field coil driver with some flux density being about 1Tesla with Fs of 38Hz and Qt of 0.3 now consider Im quite happy with it as BL product is also high enough but more than that the Qt is as per desired but now in order to reach it with a right voice coil size if its achievable with 1T what is need to going higher flux density in the gap like 1.5T or 1.8T well in that case the Qt will drop below 0.15 or so now isnt that a problem when loaded in the box?
My question is that why do you need higher flux density when you are already reaching the desired target Qt values.
I understand more stiff field but the question is isnt it detrimental to reach very low Qts values especially with woofers or do I need to be happy as Field coils flux doesnt get modulated as its always excited with external DC irrespective of the flux density.
Is there anything that Im missing in here?
My question is that why do you need higher flux density when you are already reaching the desired target Qt values.
I understand more stiff field but the question is isnt it detrimental to reach very low Qts values especially with woofers or do I need to be happy as Field coils flux doesnt get modulated as its always excited with external DC irrespective of the flux density.
Is there anything that Im missing in here?
Ideally the magnetic strength between the gap is 0.8T to 1.3T, I get to find this out after making fullrange cones and field coil motor. When you increase the magnetic gap strength, the midrange starts to peak. Anything above 1.5T things can get undesirable
You need to break down and see Qes and Qms value respectively, magnetic strength increase will decrease the Qes which reflect the magnetic strength.
You need to break down and see Qes and Qms value respectively, magnetic strength increase will decrease the Qes which reflect the magnetic strength.
Yes what I feel is that the Qts values will drop substantially even to use in small sealed boxes the variation of Qts is quiet high. Consider even Fs is increased one will loose bass in the woofer just to get Qts value to get to normal values.
Now I really dont understand the concept of why some field coil driver manufacturers market it as very high flux density is good. What I think is that using a field coil itself is a stiffer flux density so does it really matter to increase it to 2T and above when we get desired Fs and Qts values? I dont think so. Thanking for your input.
I guess what field coil manufacturers would be doing is to have very short low power voice coil which has weaker inductance so in order to get higher BL B needs to be increased. So technically the BL factor being the same but with shorter voice coil the moving mass would get lower and market the high flux density.
If anyone has got more inputs on this please reply.
I got a practical measured values by voxativ on their website there are two sensitivities for the Field coil driver https://voxativ.berlin/products/acx
95db at 60Hz and 101db at 4KHz. Technically making this a midrange driver than a full spectrum driver. So in other words either it needs a strong bottom end driver and or need a forced horn to get the additional bottom end to fill that gap.
95db at 60Hz and 101db at 4KHz. Technically making this a midrange driver than a full spectrum driver. So in other words either it needs a strong bottom end driver and or need a forced horn to get the additional bottom end to fill that gap.
The idea of strong field coil motor is to allow more headroom for you to play with the magnetic strength since they many are designed for low DC Voltage. And make the field coil more attractive to buyers.
Voice coil is a totally different domain, for example Lowther using 1:1 ratio on the voicr coil height vs magnet gap height. Hence 100% of the VC is in the magnetic flux gap, so at any give time of the Frequency response the VC is always within the flux thus higher Bl values unlike overhung design.
Underhung also introduce another set of issue when come to designing the motor. As the magnetic gap height increases, the flux density decreases.
Kinda stumbled upon this thread and am anxious to read more. I am not knowledgeable about this subject yet find it fascinating and want to try and learn more. So far, I can see that everything matters in the design of these drivers. I suppose that you would have a certain target to achieve as well, and that could vary from one intention/use to another.
Have you seen Project Ryu...
https://www.diyaudio.com/community/threads/project-ryu-diy-field-coil-loudspeaker.212953/
https://www.diyaudio.com/community/threads/project-ryu-diy-field-coil-loudspeaker.212953/
No, in fact that would be closer to my liking. I will view just observe since threads can sometimes get derailed by a simple question coming from the 'outside'. better to just see how things flow, at least at first. Thanks for the suggestion.
I have seen this but how much flux density is achieved in it im not sure but at what Qts. By the end of the day consider if we have open baffle which requires Qts of 0.7 so does the flux density still needs to be at 2T? I dont think so
what I feel its truely possible to design low inductance voice coil with high flux in the gap resulting in some Bl consider 9 so the other way is still have relatively higher voice coil inductance and yet be lower flux the BL product is still same for same Qt. Now only doubt that I had is that what is the importance of going with higher flux density. Like some might debate going with higher flux density would be stiffer in field but the voice coil is also generating the field equally for the repulsion.
Now lets consider micro level signals so having a higher voice coil inductance is relatively good enough with lower flux density?
When the motor strength is lower, the whole sensitivity falls so it's OK for small level signals to be lower too, that's just natural so is it really a factor?
I not why you have to keep thinking of flux density vs Qts. Yes the value changes wth lower and higher voltage, but what do you want to achieve in the end result of your final design? What matter most, is what you want to design your enclosure on?
Horn? Bass reflex? Open baffle? Or you are planning on using with just a half watt single ended amplifier?
Horn? Bass reflex? Open baffle? Or you are planning on using with just a half watt single ended amplifier?
The problem is not how much is the measured flux density but also how wobbling it is. So my take is I have seen some vintage FCs with small bobbin size field coils but they sound quiet good so Im guessing the Qts wouldnt be lower in that case as much as open drivers so im guessing Qts would be about 0.6 and above but still the tightness is in there.
True but only doubt I had is how much does in both cases like
low flux density and higher vc inductance
lower vc inductance and higher flux density
both achieving same BL but which one will sound better?
In a permanent magnet the higher flux density would sound better as its field need to be stiffer but in FCs is it the same case is what my concern is all about.
But what are your observations in general? When it comes to shorting rings in FC. Is it really required? I see the raising impedance curves even in FCs.