Hello all.
Been on the FR journey in OB set-up for a while. Started like most of with a okay entry level driver. Still following the news threads and hanging on I like to see if I can find a better driver. What I miss is more extension in the HF and I also want a driver that has a wider dispertion. I use a LF for the lows and I wish not to add a HF driver.
I started to study the history / development of FR drivers and can conclude that field coil drivers still should be the absolut best. History shows this time line: field coil => alnico => ferrit => neodyn………I habve seen drivers with extreme high magnetic fields achieved with permanent magnets. I do understand that you in field coil driver change the T/S by adjusting the supplied voltage. Primary changes is efficency and the QTS. I read that some claim the benefit is the ability to change the QTS but why? If used in a horn then I see a benefit to tune primary the LF output since the change by adjusting the osu supply is how you want the “bump” in the LF. While in OB I dont see an direct benefit. 1) Most FR gets support from LF drivers, they a re connected to a crossover so the QTS trim shouldn’t matter. 2) Efficeincy = can easy be adjusted with a L-Pad. And lowering the effciiency in the FR is what most end up doing. So then my question is - what is the benefit of purchasing a expensive set field coils? If you on top of your contribution I would appreciate if you also have some recomendations. Thanks in advance……..Mike
Been on the FR journey in OB set-up for a while. Started like most of with a okay entry level driver. Still following the news threads and hanging on I like to see if I can find a better driver. What I miss is more extension in the HF and I also want a driver that has a wider dispertion. I use a LF for the lows and I wish not to add a HF driver.
I started to study the history / development of FR drivers and can conclude that field coil drivers still should be the absolut best. History shows this time line: field coil => alnico => ferrit => neodyn………I habve seen drivers with extreme high magnetic fields achieved with permanent magnets. I do understand that you in field coil driver change the T/S by adjusting the supplied voltage. Primary changes is efficency and the QTS. I read that some claim the benefit is the ability to change the QTS but why? If used in a horn then I see a benefit to tune primary the LF output since the change by adjusting the osu supply is how you want the “bump” in the LF. While in OB I dont see an direct benefit. 1) Most FR gets support from LF drivers, they a re connected to a crossover so the QTS trim shouldn’t matter. 2) Efficeincy = can easy be adjusted with a L-Pad. And lowering the effciiency in the FR is what most end up doing. So then my question is - what is the benefit of purchasing a expensive set field coils? If you on top of your contribution I would appreciate if you also have some recomendations. Thanks in advance……..Mike
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basically, why do you want to upgrade your speaker system?
what aspect would you definitely like improving? Bass, mid transparency, treble clarity, imagin?
what aspect would you definitely like improving? Bass, mid transparency, treble clarity, imagin?
@youknowyou Basically I have heard better FR drivers than the one I have tried recently And if you read my post again I list what I search for - okay? So I choose to ignore your seond question.
@youknowyou, Trying to help must be a serious reply. Turning my listed expectations in to a another question is not serious. And If you read the post again then I am most curious to find a valid technical explanation / reason for why I should consider an investment in a expensive set of field coils plus a powers supply. Some would maybe use an analogy like there is only a small numbers of Ferrari’s but a lot of Fiat’s. But what make a field coil or even a Alnico stand out and considered to ne better?
@wchang There is a commercial company producing a FR with a ferrit magnet stronger than most field coils and smaller than them.
Field coil is not in any way gonna get you more HF or wider dispersion, which is what you’re looking for - right?
The answer to that is a dedicated tweeter.
The answer to that is a dedicated tweeter.
Interesting question and worth investigating. Have a look at an older thread:
https://www.diyaudio.com/community/threads/field-coil-driver-for-ob-design-advice-sought.336142/
https://www.diyaudio.com/community/threads/field-coil-driver-for-ob-design-advice-sought.336142/
IME the primary advantage of field coils is lowest 'fixed' distortion since historically the real bugaboo of audio driver/speaker design has been/is thermal power distortion due to increasingly non linear magnet performance with exponentially increasing VC heat rise, which of course the field coil is completely isolated from such problems, ergo best for accurately tracking music/whatever with no audible loss of transient response, etc., in theory/reality, but the pioneers only had tubes to drive them and variable Q tone controls, hence the amp governed the speaker's total (high) 'Q'.
Moving to permanent magnets, this in turn means increasing driver effective Qt (Qts') with increasing heat rise, increasing power demands = fast tracking to driver damage if not somehow protected, so when the 'bean counters' took over design/production the 'compromise' was AlNiCo, which up to a point yields a pleasing distortion with increasing heat rise with worst case is the bass line sounding more 'drawn out' with increasing Qts'.
Driven with a typical amp of the era we get the 'syrupy' SET tube sound many 'full range' speaker aficionados and especially horn lovers ('hornies') prefer.
Later still with the advent of SS amps we switched to hybrid versions coupled to a tube amp's output transformer and finally just pure SS with damping factor increasing along the way to allow ever higher (read cheaper to make) Qt drivers.
FYI/FWIW, etc., a class A/B amp with at least 10 W in 'A' and DF limited to < ~80 has proven a good compromise IME. Peak power requirements are a function of desired dynamic headroom, so depends on the various source's worst case scenario with +30 dB = 10^(30/10) = 1 kW (minus in room speaker efficiency) in my case for a couple of pipe organ symphony CDs.
IOW, generally not a good plan to view amps as having too much power; rather does it have enough to NOT clip 'fast' transients.
Note too that Neo drivers are currently the only permanent magnet ones available that can match the pioneer's FCs 0.1 Qts, so being 'old school' would be my default choice regardless of driver type with my near lifelong AlNiCo still a viable option for any low power app (< ~30 W music program).
As for recommendations, no personal experience with drivers newer than the early '80s, but it's dependent on the performance needs of your app, which in your case appears to 'mirror' mine, i.e. the larger the driver and the wider its BW for 'X' efficiency for best overall polar matching to the LF and keep power low at the desired listening distance is the goal with everything else (if any) falling under the heading of tweaking to 'taste' 😉.
Re will it increase dispersion? No, this is a function of the driver's effective piston area/shape.
Extend HF? Not per se in that the lower Qt can only extend HF cab loading BW by increasing its upper mass corner (Fhm) for a given Fs, but actually extending true HF requires starting with a much higher Fs, i.e. want it to 20 kHz? then assuming a 0.1 Qt is the strongest available setting: Fs = 20,000*2/0.1 = 1 kHz
(Fhm) = 2*Fs/Qts'
(Qts'): (Qts) + any added series resistance (Rs): http://www.mh-audio.nl/Calculators/newqts.html
Moving to permanent magnets, this in turn means increasing driver effective Qt (Qts') with increasing heat rise, increasing power demands = fast tracking to driver damage if not somehow protected, so when the 'bean counters' took over design/production the 'compromise' was AlNiCo, which up to a point yields a pleasing distortion with increasing heat rise with worst case is the bass line sounding more 'drawn out' with increasing Qts'.
Driven with a typical amp of the era we get the 'syrupy' SET tube sound many 'full range' speaker aficionados and especially horn lovers ('hornies') prefer.
Later still with the advent of SS amps we switched to hybrid versions coupled to a tube amp's output transformer and finally just pure SS with damping factor increasing along the way to allow ever higher (read cheaper to make) Qt drivers.
FYI/FWIW, etc., a class A/B amp with at least 10 W in 'A' and DF limited to < ~80 has proven a good compromise IME. Peak power requirements are a function of desired dynamic headroom, so depends on the various source's worst case scenario with +30 dB = 10^(30/10) = 1 kW (minus in room speaker efficiency) in my case for a couple of pipe organ symphony CDs.
IOW, generally not a good plan to view amps as having too much power; rather does it have enough to NOT clip 'fast' transients.
Note too that Neo drivers are currently the only permanent magnet ones available that can match the pioneer's FCs 0.1 Qts, so being 'old school' would be my default choice regardless of driver type with my near lifelong AlNiCo still a viable option for any low power app (< ~30 W music program).
As for recommendations, no personal experience with drivers newer than the early '80s, but it's dependent on the performance needs of your app, which in your case appears to 'mirror' mine, i.e. the larger the driver and the wider its BW for 'X' efficiency for best overall polar matching to the LF and keep power low at the desired listening distance is the goal with everything else (if any) falling under the heading of tweaking to 'taste' 😉.
Re will it increase dispersion? No, this is a function of the driver's effective piston area/shape.
Extend HF? Not per se in that the lower Qt can only extend HF cab loading BW by increasing its upper mass corner (Fhm) for a given Fs, but actually extending true HF requires starting with a much higher Fs, i.e. want it to 20 kHz? then assuming a 0.1 Qt is the strongest available setting: Fs = 20,000*2/0.1 = 1 kHz
(Fhm) = 2*Fs/Qts'
(Qts'): (Qts) + any added series resistance (Rs): http://www.mh-audio.nl/Calculators/newqts.html
In this world of low-powered amps and high-efficiency full-range speakers - how much will the VC temperature really increase with music program, and how much can we expect the magnet temperature to rise?
Let's assume that we play music with a crest factor as low as 10 dB. A 10 W amp at full power will not put more than 1W RMS into the speaker. How much heat will that generate? I'm asking, since we have pro drivers out there that can handle hundreds if not thousands of watts without bursting into flames.
Let's assume that we play music with a crest factor as low as 10 dB. A 10 W amp at full power will not put more than 1W RMS into the speaker. How much heat will that generate? I'm asking, since we have pro drivers out there that can handle hundreds if not thousands of watts without bursting into flames.
I've no clue except with pro slot car motor's armatures of various gauge windings, some of which exceeded 600 deg heat rise after just one lap of a 220 ft road racing track, but have many times heard its effects on all manner of drivers that extend down into the bass range with permanent ceramic ('mud' ) motors the worst since they act as an insulator whereas AlNiCo as a heat sinker.
They don't burst into flames due to its insulation and at least in our case, how it was applied, our major 'hurdle' in the early days of pro slot racing that once 'tackled' we rapidly reached the point where we were obsoleting our current motors before a production run made it to the distributors, so our team/products dominated, quickly causing even the major toy manufacturers to leave and why it turned out to be a 'flash in the pan' hobby for all but the most dedicated/wealthy till they completely redid the rules to make it a tightly controlled, limited spec class racing system that NASCAR, IndyCar, etc., were eventually forced to follow.
Regardless, me and pretty much anyone that listens to music/whatever with any significant bass or even just listened at elevated levels has experienced it (particularly males since hear over an octave lower) and many times it's described as not being 'fast' enough or as some form of poor pace, rhythm & timing (PR&T) performance.
They don't burst into flames due to its insulation and at least in our case, how it was applied, our major 'hurdle' in the early days of pro slot racing that once 'tackled' we rapidly reached the point where we were obsoleting our current motors before a production run made it to the distributors, so our team/products dominated, quickly causing even the major toy manufacturers to leave and why it turned out to be a 'flash in the pan' hobby for all but the most dedicated/wealthy till they completely redid the rules to make it a tightly controlled, limited spec class racing system that NASCAR, IndyCar, etc., were eventually forced to follow.
Regardless, me and pretty much anyone that listens to music/whatever with any significant bass or even just listened at elevated levels has experienced it (particularly males since hear over an octave lower) and many times it's described as not being 'fast' enough or as some form of poor pace, rhythm & timing (PR&T) performance.