Think of it in terms of turns ratio. The field coil has a huge number of turns compared to the voicecoil, so that 120mV comes down to something inaudible at the voicecoil terminals. This voltage can be seen as in series with the input voltage in the way it affects the sound output. Also, eddy currents in the steel may exclude the switching frequency before it reaches the voicecoil gap.
To measure this effect you would measure the AC spectrum at the voicecoil terminals while the fieldcoil is powered. It wouldn't be hard to make an improved supply.
The ripple will also act as flux modulation which will make no sound during silence but will modulate the voicecoil when there is current flowing through it. This would cause intermodulation with the switching frequency.
To measure this effect you would measure the AC spectrum at the voicecoil terminals while the fieldcoil is powered. It wouldn't be hard to make an improved supply.
The ripple will also act as flux modulation which will make no sound during silence but will modulate the voicecoil when there is current flowing through it. This would cause intermodulation with the switching frequency.
I haven't built a field coil driver, but I've wound transformers and coils and I do most of the work on my speakers by hand. There are sometimes items that are difficult to do yourself but most things can be done at home at little cost if you would rather learn how and put in the effort. On the up side, you get to know that it is being done right. By the way, in some areas some may find a 3d printer useful in prototyping.
Here's a thread about making cones and coils - https://www.diyaudio.com/community/...-drivers-experimentation.353861/#post-6189205
There are some measurements of T/S against field strength in this post - https://www.diyaudio.com/community/...iy-field-coil-loudspeaker.212953/post-3092843
When you change the voltage in the power supply then not just one t/s paramter change. Is there any specific parameter you wish to change?
Hi Andy,
The SMPS were intended for warming up the coils before listening, and as spare should the batteries be down while loading. For serious listening I always switched over for the batteries, but differences were small. Even when I forgot to switch and listened to the SMPS, despite the 120mV of ripple they were dead silent and sounded quite good.
All the best
Mattes
Hi,
As Allen has said, your own FC driver must not be expensive. Make your own metal parts, wind your own coil and slaughter an already existing driver for coil, basket and cone. All this can be relatively cheap, but don´t expect any fieldcoil wonders from cheap reused drivers. The quality of your final driver will be a result of all parts together, get one wrong and no fieldcoil motor will help.
As Zen said, things get a lot more complicated and expensive once you start to really make, or have professionally produced in small series, your own parts. If you make a small series by yourself, count and calculate your working hours, tax and workplace and so on. If you have parts produced for your small series, you´ll soon find that this requires quite some money efforts, too...
In general, producing a driver in small series in Europe makes it necessarily expensive, and sometimes I wonder how Istvan for example can afford to offer his products at quite low prices.
If you want relatively cheap drivers, they´ll need to be made in large numbers, or in China, or both.
All the best
Mattes
Istvan is able to do that "only" because he is in business for decades, knowing where to obtain (relatively) cheap custom made parts, pricing his own stock of custom parts ( paper) not too much and also not taking too much for his own number of man-hours
Far from me being in situation of peeking above Istvan's shoulder, but judging by my own experience of ultra-small business, in this neck of wood
So, as I'm writing for years - if you want newly made driver - having core of your GrandMa's Telefunken Radio Magic, while having details as modern one and being made in modern ways, all that plus really great Bang for the Buck ratio, call Sonido and buy ....... or try to hear any and involve brain and ears ....... whatever
Again, ZM is extra happy customer, no other linkage to Sonido in any way ...... if nothing else, I did learn with years to say when I'm sure that something is overpriced BS, and also to give credit where is due
Last edited:
Hi ZM,
Yes, having access to "old" facilities, logistics and so on will surely have an influence on price, and you´re right, Istvans prices are fine for his products. I have also suggested them here to others, and will do that again if someone looks for nice drivers for attainable prices, including FC drivers.
Other FC drivers for fair prices could be found at EMS and at Supravox.
Where does your "overpriced BS" area starts? My own drivers will probably fall into this area, but once you recalculate material cost in small series and working hours for a hand-made product, things will fall into perspective...
All the best
Mattes
Yes, having access to "old" facilities, logistics and so on will surely have an influence on price, and you´re right, Istvans prices are fine for his products. I have also suggested them here to others, and will do that again if someone looks for nice drivers for attainable prices, including FC drivers.
Other FC drivers for fair prices could be found at EMS and at Supravox.
Where does your "overpriced BS" area starts? My own drivers will probably fall into this area, but once you recalculate material cost in small series and working hours for a hand-made product, things will fall into perspective...
All the best
Mattes