It depends on the ribbons... how many Ohms ( or fraction of ohms 
) ar we talking about?
BTW apart from the "la folia proyect" , do you know about a suitable DIY ribbon plans (Not a kit, please)? nowadays this kind of loudspeaker seem to have vanished on the air...
thanks in advance for the info
) ar we talking about?BTW apart from the "la folia proyect" , do you know about a suitable DIY ribbon plans (Not a kit, please)? nowadays this kind of loudspeaker seem to have vanished on the air...
thanks in advance for the info
I haven't done the math to figure out the exact impedance. Just ballparking it, the impedance would be between one and two orders of magnitude lower than a typical driver, ie. 0.6 to 0.06 ohms, with most of that impedance coming from the air load (the good news is I'll be horn loading, which raises the impedance of the air load). I wouldn't need much power, but I simply don't know if there are any suitable transisters that could provide the required current and achieve a low-enough output impedance. I'm used to building amps with tubes and I know for sure there aren't any suitable tubes for this purpose.
John
John
karellen said:It depends on the ribbons... how many Ohms ( or fraction of ohms
BTW apart from the "la folia proyect" , do you know about a suitable DIY ribbon plans (Not a kit, please)? nowadays this kind of loudspeaker seem to have vanished on the air...
thanks in advance for the info
Sorry, I don't know of any plans. I did come across a web site once where some guys (in Sweden, I think) were looking to do a group purchase of some neo magnets from China to do a project. I'll see if I can find that again,
John
So far about all these points have been discussed here:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=36559&perpage=10&pagenumber=1
http://www.diyaudio.com/forums/showthread.php?s=&threadid=36559&perpage=10&pagenumber=1
What about current amplifiers??
For this you should consider current amplifiers. Pass is actually fiddling with that kind of amplifiers. And he has written articles about it. You can find it on the first-watt site.
Driving ribbons must be one of this kind of amps favorite. This because it is almost a pure resistance. And you would be able to skip the transformer.
The problem is to find schematics of such amps...... Dear mister Pass, or anyone else with deep knowledge of the inner workings of a power amp: How would we have to modify lets say the Aleph-X or even more normal amps to achieve this.
I know setting a series resistance is one way, but to set an 8 ohm series resistance with a driver with 0.1 ohm seems like wasting a little too much energy for my taste.
A fairly low powered amp for driving ribbon tweeters or a small compression driver or something as an active source is really appealing to me. And the Aleph-X seems to me to be a perfect candidate for this. The problem is the implementation of currend feedback.
Your idea may be to use it as full range too, but then you need WAY much more power, I know! I have a playing La Folia set that I built 14 years ago! And a 500W beefed up bridged A-40 amp seems to not be enough….. A X-1000 modified for current feedback seems like the thing for that kind of speakers…..
For this you should consider current amplifiers. Pass is actually fiddling with that kind of amplifiers. And he has written articles about it. You can find it on the first-watt site.
Driving ribbons must be one of this kind of amps favorite. This because it is almost a pure resistance. And you would be able to skip the transformer.
The problem is to find schematics of such amps...... Dear mister Pass, or anyone else with deep knowledge of the inner workings of a power amp: How would we have to modify lets say the Aleph-X or even more normal amps to achieve this.
I know setting a series resistance is one way, but to set an 8 ohm series resistance with a driver with 0.1 ohm seems like wasting a little too much energy for my taste.
A fairly low powered amp for driving ribbon tweeters or a small compression driver or something as an active source is really appealing to me. And the Aleph-X seems to me to be a perfect candidate for this. The problem is the implementation of currend feedback.
Your idea may be to use it as full range too, but then you need WAY much more power, I know! I have a playing La Folia set that I built 14 years ago! And a 500W beefed up bridged A-40 amp seems to not be enough….. A X-1000 modified for current feedback seems like the thing for that kind of speakers…..
After finding a link to the First-Watt F1 ( http://www.firstwatt.com/products.htm ) it occured to me that this is what we need.....
Only we have to change the working point to optimize it for the working range (the F1 is obviously made for 8 ohm drivers) of the ribbons (in the 0.8 ohm and below range).
So all we have to do now is to wait for this to be released for DIY
But I would love to rebuild the Aleph-X too...... I'm sure they arn't that diffrent from each other.
Only we have to change the working point to optimize it for the working range (the F1 is obviously made for 8 ohm drivers) of the ribbons (in the 0.8 ohm and below range).
So all we have to do now is to wait for this to be released for DIY
But I would love to rebuild the Aleph-X too...... I'm sure they arn't that diffrent from each other.
Re: What about current amplifiers??
Oh, one other thing...
The advantage of a current amp really comes through when you have a driver with a high inductance. There are several distortion mechanisms associated with that inductance and current drive negates them all.
best regards, John
akb1212 said:
Oh, one other thing...
The advantage of a current amp really comes through when you have a driver with a high inductance. There are several distortion mechanisms associated with that inductance and current drive negates them all.
best regards, John
Does anyone have experience designing or using digital amplifiers to drive very low impedance loads < 1 ohm?
I have constructed several very good sounding Class-A analog amplifiers that use +/- 8 V output power supplies through four bipolar output pairs to direct drive 0.7 ohm ribbons. Much better sounding than either a transformer that shifts phase, or a current amp that cannot control ribbon physical resonance oscillations. Analog crossovers, however, may not be the right solution to get the best sound a normal room.
Digital crossovers offer many advantages for flexibility in steep slope, time alignment, and room equalization. Running a digital signal to each speaker that has its own digital crossover with equalization and digital amplification seems very attractive.
Digital amps are very efficient, and padding a 0.05 ohm tweeter ribbon up to reasonable 0.5 -1 ohms amplifier load with a non-inductive resistor would still dissipate little heat but provide more physical motor control than a traditional high output impedance current amp.
Should we start a new thread in Class-D forum to discuss a digital amplifier to drive 0.5 to 1 ohm loads?
I have constructed several very good sounding Class-A analog amplifiers that use +/- 8 V output power supplies through four bipolar output pairs to direct drive 0.7 ohm ribbons. Much better sounding than either a transformer that shifts phase, or a current amp that cannot control ribbon physical resonance oscillations. Analog crossovers, however, may not be the right solution to get the best sound a normal room.
Digital crossovers offer many advantages for flexibility in steep slope, time alignment, and room equalization. Running a digital signal to each speaker that has its own digital crossover with equalization and digital amplification seems very attractive.
Digital amps are very efficient, and padding a 0.05 ohm tweeter ribbon up to reasonable 0.5 -1 ohms amplifier load with a non-inductive resistor would still dissipate little heat but provide more physical motor control than a traditional high output impedance current amp.
Should we start a new thread in Class-D forum to discuss a digital amplifier to drive 0.5 to 1 ohm loads?
Re: Re: What about current amplifiers??
It floats in the wind anyway, that's part of its charm. A current
source amp or a series ballast resistor is useful because the
impedance of the ribbon itself is so low that other factors, like
cable inductance and connection quality become much larger.
hancock said:
It floats in the wind anyway, that's part of its charm. A current
source amp or a series ballast resistor is useful because the
impedance of the ribbon itself is so low that other factors, like
cable inductance and connection quality become much larger.
My experiences with my own ribbons (mine are two way copies of Apogee) are that the tweeters are flying in the wind, and there is absolutely nothing to stop it from that except mechanically keeping it there! The only important things are that they stay in the magnetic field and are directed correctly. My ribbons are 120 cm long, and do flap a lot in the wind. But that is no problem at all!
And the fact that ONE of the advantages of current amps is its ability to overcome the problems with inductance doesn't mean there's no point in using it.
My reason for suggesting it is that I have seen (normal voltage feedback) amps constructed for this use, and the output stage of these are a pain to make. This because you are trying to get the same damping at magnitudes lower impedances. That is not easily overcome! Using an amp with high output impedance means no extra problems in this regard.
And you would get all the other advantages of current amps.
Just to mention it...... there are some problems concerning current amps to, and there is a reason for it not being used. One problem is that it is not suitable with loudspeaker systems with large fluctuations in impedance. At the peaks of impedance the power put out in the speaker INCREASES, and that is at the resonances meaning the speaker is extra sensitive there. Take the bass-reflex as an example. If the impedance doubles so does the power. And then you have a problem. And to ribbons advantage is that is has a really FLATT impedance curve, and is therefore really suited for current amplification.
One more thing about control of membrane. Current amps leaves the damping of the mechanical systems to the mechanical part of the system. Ribbons are a really good here because they really don't need high electrical damping. If you take a look at this test of the First-Watt F1 amp you can read the following when he is trying to describe the sound of the system: " First and foremost, what the F1 brings to the table is control over the voice coil."
It may SOUND like the amp has control over the voice coil, but compared to almost any other amplifier in the world it really DOESN'T! Well, it does, but not by brute force way a normal amp is telling it where to be at every moment. It is the mechanical damping of the system that keeps the speaker at it's operating point and the amp is telling it how to move relative to that at every moment. There is no back EMF from the voice coil that keeps it in place when it is not behaving as it is believed to do (and in this case it is clear that it DOES, witch would not be true for most other speakers since they aren’t made for current amps).
So, in my opinion current amps are absolutely worth thinking about in combination with ribbons. Hey, even the tweeter in the test speakers in the above mentioned test is a ribbon, and probably because of above mentioned suitability! Isn't that a good hint?
And the fact that ONE of the advantages of current amps is its ability to overcome the problems with inductance doesn't mean there's no point in using it.
My reason for suggesting it is that I have seen (normal voltage feedback) amps constructed for this use, and the output stage of these are a pain to make. This because you are trying to get the same damping at magnitudes lower impedances. That is not easily overcome! Using an amp with high output impedance means no extra problems in this regard.
And you would get all the other advantages of current amps.
Just to mention it...... there are some problems concerning current amps to, and there is a reason for it not being used. One problem is that it is not suitable with loudspeaker systems with large fluctuations in impedance. At the peaks of impedance the power put out in the speaker INCREASES, and that is at the resonances meaning the speaker is extra sensitive there. Take the bass-reflex as an example. If the impedance doubles so does the power. And then you have a problem. And to ribbons advantage is that is has a really FLATT impedance curve, and is therefore really suited for current amplification.
One more thing about control of membrane. Current amps leaves the damping of the mechanical systems to the mechanical part of the system. Ribbons are a really good here because they really don't need high electrical damping. If you take a look at this test of the First-Watt F1 amp you can read the following when he is trying to describe the sound of the system: " First and foremost, what the F1 brings to the table is control over the voice coil."
It may SOUND like the amp has control over the voice coil, but compared to almost any other amplifier in the world it really DOESN'T! Well, it does, but not by brute force way a normal amp is telling it where to be at every moment. It is the mechanical damping of the system that keeps the speaker at it's operating point and the amp is telling it how to move relative to that at every moment. There is no back EMF from the voice coil that keeps it in place when it is not behaving as it is believed to do (and in this case it is clear that it DOES, witch would not be true for most other speakers since they aren’t made for current amps).
So, in my opinion current amps are absolutely worth thinking about in combination with ribbons. Hey, even the tweeter in the test speakers in the above mentioned test is a ribbon, and probably because of above mentioned suitability! Isn't that a good hint?
Brian Donaldson said:
hmmm.... aleph ribbon amp.
maybe I will try that , yikes not another project!
Iam currently machinning plates for a set of ribbon tweeters
similar to the raven r2. and are winding transformers to drive them.
on the other hand i have a 2x6v @ 40 amp transformer
and a 250amp bridge rectifier and and..... hmmm
A direct drive ribbon amp ... COOL!!
Sounds like just what the doctor ordered
An amp with a max output of 1 volt, 20 amps into .050 ohms for 20 watts
I'm not an amp designer but it seems like low voltage railsl, lots of output devices to share the current and reduce the source imp. and ... wha-la Bob's your uncle!
Sounds like just what the doctor ordered
An amp with a max output of 1 volt, 20 amps into .050 ohms for 20 watts
I'm not an amp designer but it seems like low voltage railsl, lots of output devices to share the current and reduce the source imp. and ... wha-la Bob's your uncle!
hancock said:
http://www.hififorum.nu/forum/topic.asp?TOPIC_ID=34799
http://www.hififorum.nu/artiklar/Dahlbergsband/del1/Dahlbergsband.htm
Now you only have to learn swedish
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