Tenson said:
The 5th page of the pdf provides an exploded view of the driver - just looking at this I'd say that its unlikely - and even if you could the steel case would still be there (..and its needed to increase field strength for the magnets). (i.e. the transformer is "tucked" into the magnet assembly - so there would be no dimensional "savings".)
Hmm, a pity. Just so people know, I am pretty sure the transformer can be taken off the back of the Fountek NeoPro5i. You are left with the metal enclosure which is a lot slimmer.
Well I think I will still go with the RAAL if it is that much better (and a bit cheaper!). - It looks sexy
😉
Well I think I will still go with the RAAL if it is that much better (and a bit cheaper!). - It looks sexy
😉
Tenson said:
If you do go ahead an purchase them, please be sure to report back your opinion 😉 - I wouldn't put it here, make a new thread if there isn't one already on that particular model.
(..Oh..and of course make sure you use an appropriate crossover for the desired bandwidth.. Additionally remember what I said about impeadance and amplifiers, AND IF you need to "pad" down the driver make your own copper resistors (not store bought)- this can make a world of difference. I believe there is a thread on making your own some where in diyaudio.)
I will be using digital crossovers so all I need to worry about is the amp. How can I tell what sort of damping factor an amp has? Also what did you think would work best for these?
I will let you know what I think if I do get them, but it will be a while before I do.
I will let you know what I think if I do get them, but it will be a while before I do.
Tenson said:
You may need to worry about dc from the output of the amp (and how much the transformer can reject it). Otherwise you might need a blocking capacitor. (that information you likely will NOT find for the amp - i.e. if you are concerned you'll need to measure it yourself.)
http://www.diyaudio.com/forums/showthread.php?s=&threadid=22107&highlight=
What you need then is the output impeadence of the amp for the calculation. (..most amps provide this information.)
I'd look for a amp with an output impeadance at or above 8 ohms. A lot of tube amps have this. In fact this is a good idea for the midrange as well IF it is similarly efficient (..see Nelson Pass's article on the First Watt website).
If you are adventuresome you could DIY a version of Nelson Pass's First Watt F1 amplifier. That would certainly be less expensive (not including case work). (..heck, with such a design you could even chuck the ribbon's transformer - but I wouldn't recomend it.)
Also note that with such amplifers the low impeadance shift of the ribbon transformer will help attenuate (reduce) the low freq. response below 1kHz. A good "voltage" amplifier (one with a low output impeadence) would do the opposite.
Long Ribbon Distortion
TAS on Dali Ribbon Linesources
http://www.theabsolutesound.com/newsletter/146/dali_ms4.html
"The Dali Megalines really do get distortion effects -and intermodulation effects in particular- down to unprecedentedly low levels, down, one feels, virtually to the threshold levels of preception."
The MegaLine use a dipole ribbon linesource.
With monopole ribbons, absorbing the rear wave is critical for low distortion.
TAS on Dali Ribbon Linesources
http://www.theabsolutesound.com/newsletter/146/dali_ms4.html
"The Dali Megalines really do get distortion effects -and intermodulation effects in particular- down to unprecedentedly low levels, down, one feels, virtually to the threshold levels of preception."
The MegaLine use a dipole ribbon linesource.
With monopole ribbons, absorbing the rear wave is critical for low distortion.
why is absorbing the rear wave critical for
low distortion.
seems that changing the impedance from front to back would cause distortion.
what am i missing ?
thanks.
low distortion.
seems that changing the impedance from front to back would cause distortion.
what am i missing ?
thanks.
Scott,
I have read most of that thread and while I found most of it pretty hard going for a non-electronics engineer like myself, I think I understand some of it. Got lost on the finer details of voltage vs. current drive though!
Anyway I'm still not sure WHY you say an amp with a lower DF is better for use with a low mass driver?
I was thinking I might use a UCD Hypex amp, which I understand has a Z-load independent frequency response. Would this avoid any issues with the damping factor?
Or would I be better going for a standard voltage or current drive amp with low damping factor?
Or a high damping factor but no negative feedback?
lol
Thanks,
Simon
I have read most of that thread and while I found most of it pretty hard going for a non-electronics engineer like myself, I think I understand some of it. Got lost on the finer details of voltage vs. current drive though!
Anyway I'm still not sure WHY you say an amp with a lower DF is better for use with a low mass driver?
I was thinking I might use a UCD Hypex amp, which I understand has a Z-load independent frequency response. Would this avoid any issues with the damping factor?
Or would I be better going for a standard voltage or current drive amp with low damping factor?
Or a high damping factor but no negative feedback?
lol
Thanks,
Simon
Hi snkby,
Many monopole ribbons use a closed back magnetic circuit to increase the gap flux. Dampening material in these cavities is very important for low distortion.
Dipole ribbons can have a very open back, but it is still worth experimenting with diffraction control on both front and back pole pieces, as well as trying thin cloth tape on large areas of rear exposed magnets or iron.
Many monopole ribbons use a closed back magnetic circuit to increase the gap flux. Dampening material in these cavities is very important for low distortion.
Dipole ribbons can have a very open back, but it is still worth experimenting with diffraction control on both front and back pole pieces, as well as trying thin cloth tape on large areas of rear exposed magnets or iron.
Attachments
Hi Tenson,
A step-down transformer driving a very low impedance ribbon will generate a reverse voltage(EMF) from the coupled inductance and high ribbon current. An amplifier with a high dampening factor can better dampen this noise current without distortion.
Direct drive of a very low impedance ribbon can be done with a very low output impedance, high dampening factor "voltage source amp" that can supply high currents, plus a modest value series resistance (1-2 ohms) to pad up the < 0.1 ohm ribbon. There will be power loss in the resistor.
Direct drive of a low impedance ribbon can also be done with a high output impedance "current source amp" that can safely supply adequate current into a dead short because of its normal high output impedance, and hence low dampening factor output stage that absorbs the power loss.
A step-down transformer driving a very low impedance ribbon will generate a reverse voltage(EMF) from the coupled inductance and high ribbon current. An amplifier with a high dampening factor can better dampen this noise current without distortion.
Direct drive of a very low impedance ribbon can be done with a very low output impedance, high dampening factor "voltage source amp" that can supply high currents, plus a modest value series resistance (1-2 ohms) to pad up the < 0.1 ohm ribbon. There will be power loss in the resistor.
Direct drive of a low impedance ribbon can also be done with a high output impedance "current source amp" that can safely supply adequate current into a dead short because of its normal high output impedance, and hence low dampening factor output stage that absorbs the power loss.
LineSource said:
Back EMF generated from a ribbon (even with the inductance of the transformer - which is extremely low for a ribbon transformer because of it's size) is almost negligible.. Then there is back EMF from other drivers and its effect with transformer inductance (..provided the drivers are coupled - though here in an active design they are not). Again though the transformer is small with low inductance and low self resonance - so even in a "coupled" configuration its a moot point. (Note however that the transformer can block back emf to a degree as well - which is one of the reasons I alluded to a transformer coupled driver as having additional benefits).
Additionally (in general) most of the time low impeadance is achieved with feedback in the amplifier. With a real signal and a real load, feedback (global) actually causes more problems than it solves - dramatically increasing distortion (despite its original intent). I think there was a website that actually tried to confirm this in measurements.. if you are interested you might want to do some searching to see if it still exists.
OK then "why" the high output impeadance and low dampening factor? A ribbon (with the exception of its resonance) is already effectivly well "dampened" directly from the signal magnetically. Increasing this over-dampens the driver's output and tends to give a lifeless one-dimensional character. The same is typically true for high eff. drivers in general - but more so with ribbons.
(btw, the provided link was only there for Steve Eddy's reply that gave the relationship between amplifier impeadance and speaker/load impeadance to calculate dampening factor.)
Edit: This was written a few seconds before Scott replied above me!
Thanks Linesource,
But that seems to go against what Scott said:
Scott is saying a low damping factor is better then. I don't think Scott was talking about direct drive there either.
So okay, those are the options, but the million dollar question; which is better?
I would have thought either a transformer with a voltage drive amp and high damping factor (at least from what you say). Or a current drive amp with high output impedance and you just suffer the low damping factor.
How much effect would the low damping factor have on a ribbon? I would think as it has no mechanical damping it would need lots of electrical damping... What would happen at its resonance?
I would stay away from voltage drive with a series resistor as from tests with passive pre-amps a transformer seems to be much preferred to a resistor.
The nice thing is that as I am doing an active three way design I can use whatever type of amp I want with each driver. I also have access to EQ.
Thanks Linesource,
But that seems to go against what Scott said:
Scott is saying a low damping factor is better then. I don't think Scott was talking about direct drive there either.
So okay, those are the options, but the million dollar question; which is better?
I would have thought either a transformer with a voltage drive amp and high damping factor (at least from what you say). Or a current drive amp with high output impedance and you just suffer the low damping factor.
How much effect would the low damping factor have on a ribbon? I would think as it has no mechanical damping it would need lots of electrical damping... What would happen at its resonance?
I would stay away from voltage drive with a series resistor as from tests with passive pre-amps a transformer seems to be much preferred to a resistor.
The nice thing is that as I am doing an active three way design I can use whatever type of amp I want with each driver. I also have access to EQ.
Ahh okay Scott just replied lol!
Hmm with an over damped driver, isn't the only thing that would happen, is the resonance would be diminished and so LF response would roll-off sooner?
I can't see any obvious resonance on the RAAL, but I guess that’s because the transformer is smoothing the impedance.
Any ideas of how it would react with a UCD digital amp? The other amp I currently have is a class A zero feedback Monarchy Audio SM70 amp. Anybody know what damping factor / Zout this amp has?
Any thoughts on using the driver IN the feedback loop? I have not heard of this being done with a tweeter.
I just worked out that the UCD amp would have a damping factor of 400 at 8Ohms. Its Zout at 1KHz is <20mΩ. The reason I am interested in this amp particularly is because as I said before, its frequency response is supposed to be independent of the load, but I suppose this does not take in to account variations from damping?
Sorry for lots of questions I am very new to the electronics side of audio.
Hmm with an over damped driver, isn't the only thing that would happen, is the resonance would be diminished and so LF response would roll-off sooner?
I can't see any obvious resonance on the RAAL, but I guess that’s because the transformer is smoothing the impedance.
Any ideas of how it would react with a UCD digital amp? The other amp I currently have is a class A zero feedback Monarchy Audio SM70 amp. Anybody know what damping factor / Zout this amp has?
Any thoughts on using the driver IN the feedback loop? I have not heard of this being done with a tweeter.
I just worked out that the UCD amp would have a damping factor of 400 at 8Ohms. Its Zout at 1KHz is <20mΩ. The reason I am interested in this amp particularly is because as I said before, its frequency response is supposed to be independent of the load, but I suppose this does not take in to account variations from damping?
Sorry for lots of questions I am very new to the electronics side of audio.
Tenson said:
I *think* that if the driver is "in" the feedback loop that it becomes a current mode amp. (i.e. impeadance goes WAY up.) I'm almost positive that you can't do this with the UCD, but you can do this (properly even) with the monarchy. Rod Elliot has more information on voltage mode vs. current mode and some specifics. (i.e. search).
As line source suggested you could also change impeadance dampening factor with a resistor, with a coresponding power loss. Or you could use an autoformer.
Still if it were me and you wanted to do this relativly cheaply I'd be copying Mr. Pass's F1. He has graciously provided the schem. and the circuit boad trace (via the manual) to the public for non-comercial use. Its a "no-brainer". (..and it still leaves some possible "tweaking" for the DIY'er - especially in the power supply.)
So put simply you recommend a current source amp as it will have a high output impedance and thus low damping factor, but not necessarily for the other supposed advantages a current amp holds.
I don't have any experience of current source amps... can someone list a few more? The Pass F1 is not really powerful enough. Do they normally come so low powered? I would rather have 100watts or so.
I don't have any experience of current source amps... can someone list a few more? The Pass F1 is not really powerful enough. Do they normally come so low powered? I would rather have 100watts or so.
Getting back to ribbon tweeter distortion, so the lack of mechanical damping contributes to most of the distortion if i'm correct? Since it is in an even magnetic field. However what if one tried to mechanically damp a ribbon. As crazy as it souncds what if the edge of the ribbon was spidered to the magnets? LIke a very thin layer of rubber on the edge of the ribbon to the magnets?
Wow, thank you everyone for the replies. It has been very insightful.
Wow, thank you everyone for the replies. It has been very insightful.
If you look at the CSD data within the first 0.5ms or so, you can proabably find a good trade-off between damping and resolution. Adding rubber will add mass, and thus you get less effeciency or reduced resolution or reduced bandwidth. For ribbon tweeters, I think the best way to tweak the motor to see what gives best performance.
Tenson said:
The biggest advantage is virtually a complete absence of back emf and what it will do to the amplifier (and on up the "chain").
Trust me.. in an active configuration the F1 will be more than powerful enough - with 2 watts you will have almost the same output as a radial saw at 1 meter for this driver. (i.e. damn loud and at the threashold of pain.)