Air core coils typically have a little more DCR which doesn't make too much difference in parallel / hpf filters but in series / lpf there may be some loss of sensitivity.
Here's an old thread on the subject, info still applies.
http://www.diyaudio.com/forums/multi-way/9199-air-core-vs-iron-core.html
Here's an old thread on the subject, info still applies.
http://www.diyaudio.com/forums/multi-way/9199-air-core-vs-iron-core.html
Thanks bbggg and DrDyna, I will check that thread. Observe I meant a non-ferrite core, in that thread DrDyna they discuss ferrite core vs air core. Before chosing my 2.5mH coil I ead it was a good alternative to the air core coil since it is cheaper but still good. I know it sounds good in my speakers but I wonder what it really is, "non-ferrite core coil". It got some kind of core material, is it steel pulver or something like that ?
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I haven't personally used them, but there are some respectable speaker designs that do, such as these:
Jenzen CA
It's all rather straightforward to comprehend, if explained well. 
An armature in a coil gets magnetized by the magnetic field created by current flow in the coil. What then happens is that gazillions of magnetic crystals in the armature get into alignment with the external field, whereas their alignment was haphazard before. The generating current is alternating and, after peaking, it dies down again. This allows the crystals to return to their haphazard status quo ante. Ideally they are back to where they were before current ever flowed. Except they are not, there is always a small percentage of crystals that do not snap back into their previous random orientation. They stay roughly aligned to the field that existed a while ago. As current reverses, they start to align with the new field (which is the opposite of the old field) and in a short while about half of them are out of order, their field cancelling the field of the other half. The field in the armature is then zero, but the current in the coil is not.
This whole charade is repeated with every current cycle. Ideally, if one were to graph armature magnetisation versus field intensity, they should get a straight line passing through zero. In reality the phenomenon roughly described above warps this straight line into two S-shaped curves, one going up, one going down, and they are offset from each other as well.
This is called magnetic hysteresis. It means that, when subjected to a changing external magnetic field, armatures respond lazily and they also need some persuasion to do so. This hysteretic curve not being straight, means that there is distortion in the waveform as it is "reflected" on the curve. The offset between the up and down parts of the curve means that there is asymmetry in the resultant output. Asymmetry means even order distortion by definition. In practice the bulk of this even order distortion is proved to be 2nd harmonic.
2nd HD can be very nice. Has anyone noticed how composers use it? They double violins with flutes and flutes with piccolos. As long as they all play unison, it works. Strings thrum and sparkle at the same time. It's magic. The magic of unison, i.e. the magic of even order harmonic distortion. Hint: it's false.
Armatures can support much higher magnetic intensities than air or wood, for example, but there is only so much they can do before they saturate. This happens when all their crystals are in total alignment with the field. From that point upwards, there is no more magnetism to be had from the armature. It "clips" so to speak. This is odd order harmonic distortion by definition, and it's predominantly 3rd harmonic.
3rd HD can be very exciting. It adds whack. Drummers play more forcefully, as though they are on speed, ehm, as though they were on speed, cue statute of limitations blah, blah, blah, and since drummers on drugs is a whole other issue, I'll leave it at that. Anyhow it can be very exciting to listen to. Hint: it's false.
To minimize these phenomena, the two S curves need to be as flat as possible, or at least to have a reasonably straight part, and to be offset from each other in the least amount possible. The closer an armature approaches this ideal behavior, the smaller the distortion it can generate.
An armature in a coil gets magnetized by the magnetic field created by current flow in the coil. What then happens is that gazillions of magnetic crystals in the armature get into alignment with the external field, whereas their alignment was haphazard before. The generating current is alternating and, after peaking, it dies down again. This allows the crystals to return to their haphazard status quo ante. Ideally they are back to where they were before current ever flowed. Except they are not, there is always a small percentage of crystals that do not snap back into their previous random orientation. They stay roughly aligned to the field that existed a while ago. As current reverses, they start to align with the new field (which is the opposite of the old field) and in a short while about half of them are out of order, their field cancelling the field of the other half. The field in the armature is then zero, but the current in the coil is not.
This whole charade is repeated with every current cycle. Ideally, if one were to graph armature magnetisation versus field intensity, they should get a straight line passing through zero. In reality the phenomenon roughly described above warps this straight line into two S-shaped curves, one going up, one going down, and they are offset from each other as well.
This is called magnetic hysteresis. It means that, when subjected to a changing external magnetic field, armatures respond lazily and they also need some persuasion to do so. This hysteretic curve not being straight, means that there is distortion in the waveform as it is "reflected" on the curve. The offset between the up and down parts of the curve means that there is asymmetry in the resultant output. Asymmetry means even order distortion by definition. In practice the bulk of this even order distortion is proved to be 2nd harmonic.
2nd HD can be very nice. Has anyone noticed how composers use it? They double violins with flutes and flutes with piccolos. As long as they all play unison, it works. Strings thrum and sparkle at the same time. It's magic. The magic of unison, i.e. the magic of even order harmonic distortion. Hint: it's false.
Armatures can support much higher magnetic intensities than air or wood, for example, but there is only so much they can do before they saturate. This happens when all their crystals are in total alignment with the field. From that point upwards, there is no more magnetism to be had from the armature. It "clips" so to speak. This is odd order harmonic distortion by definition, and it's predominantly 3rd harmonic.
3rd HD can be very exciting. It adds whack. Drummers play more forcefully, as though they are on speed, ehm, as though they were on speed, cue statute of limitations blah, blah, blah, and since drummers on drugs is a whole other issue, I'll leave it at that.
Anyhow it can be very exciting to listen to. Hint: it's false.To minimize these phenomena, the two S curves need to be as flat as possible, or at least to have a reasonably straight part, and to be offset from each other in the least amount possible. The closer an armature approaches this ideal behavior, the smaller the distortion it can generate.
Hi Salas . Yes I think it is very good in many respects, I have not compared directly but my memory after living with my Revel M20 for 8 years (so I think I have a rather good knowledge of how they sound ) is this: You can with my electronics play louder without it sounding distorted, but I know the M20 can play very loud also but it needs a bigger amp than mine to do that. I think it sounds a little purer in the middle range, it is easier to hear the lyrics of a song, but the M20 has a more forward middle range (can be nice). The tweeter is better, more refined than the M20, it is less dry and more "air". The bass is more powerful but a littler leaner as I have said before, maybe maybe I want it to be more prominent and as you said it can be that with a bigger coil, for example 2,6 or 2.7mH (I have not tried this). But since it still needs to play to settle in we will se about that, there is good hope I will keep the 2.5mH since it never becomes "loudness sounding" so to speak. There are a few parameters I am not sure about but I can compare later, such as depth and hight in soudstage (good soundstage with M20). The bass from the M20 is more chiselled but I am not sure it is correct. I think that will do for now, I will give all info when I can.
And when I remember it: I asked about if it is a bad idea to leave any of the side areas without damping, I tried that and it sounded very open I think, but maybe some damping is not affecting that too much.
. Yes I think it is very good in many respects, I have not compared directly but my memory after living with my Revel M20 for 8 years (so I think I have a rather good knowledge of how they sound ) is this: You can with my electronics play louder without it sounding distorted, but I know the M20 can play very loud also but it needs a bigger amp than mine to do that. I think it sounds a little purer in the middle range, it is easier to hear the lyrics of a song, but the M20 has a more forward middle range (can be nice). The tweeter is better, more refined than the M20, it is less dry and more "air". The bass is more powerful but a littler leaner as I have said before, maybe maybe I want it to be more prominent and as you said it can be that with a bigger coil, for example 2,6 or 2.7mH (I have not tried this). But since it still needs to play to settle in we will se about that, there is good hope I will keep the 2.5mH since it never becomes "loudness sounding" so to speak. There are a few parameters I am not sure about but I can compare later, such as depth and hight in soudstage (good soundstage with M20). The bass from the M20 is more chiselled but I am not sure it is correct. I think that will do for now, I will give all info when I can.And when I remember it: I asked about if it is a bad idea to leave any of the side areas without damping, I tried that and it sounded very open I think, but maybe some damping is not affecting that too much.
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Thanks for the detailed reply. You can never really know if a result is balanced enough without a reference. Revel M20 is almost immaculately engineered (possibly by Floyd E.Toole himself?) so its a tough act to follow on basics.
Revel Performa M20 loudspeaker Measurements | Stereophile.com
Revel Performa M20 loudspeaker Measurements | Stereophile.com
Revel Performa M20 loudspeaker Measurements | Stereophile.com
Revel Performa M20 loudspeaker Measurements | Stereophile.com
This is the man behind Revel M20 I believe (with Floyd E.Toole I guess):
Kevin Voecks: Loudspeakers, Crossovers, & Rooms | Stereophile.com
I am playing the "Tired2way" all day when at work at modest level, and at higher levels when I get home, so I think they will be settled in soon.
Edit: the speakers Salon2 in that link are very very good speakers, and the best speakers I have heard are the TAD Reference One:
http://www.pioneer.eu/se/products/42/99/161/TAD-R1/index.html
Kevin Voecks: Loudspeakers, Crossovers, & Rooms | Stereophile.com
I am playing the "Tired2way" all day when at work at modest level, and at higher levels when I get home, so I think they will be settled in soon.
Edit: the speakers Salon2 in that link are very very good speakers, and the best speakers I have heard are the TAD Reference One:
http://www.pioneer.eu/se/products/42/99/161/TAD-R1/index.html
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Salas, one question I have lurking somewhere in my head is this:
If you use a bigger coil, making the bass more prominent, will that in turn mean that the middle range will sink in a little at the same time, or does it just affect the bass? I think that as the filter is now the middle range should not be more withdrawn than it is, I could even have it a bit more forward to be honest. So, if a bigger coil will do that it is out of the question for my taste, it is better left as it is.
Also I should mention I am happy with the speakers, no doubt about that. It makes me thinking of trying to make a construction all by myself next time, since I am rather sure I will build a new pair some day.
If you use a bigger coil, making the bass more prominent, will that in turn mean that the middle range will sink in a little at the same time, or does it just affect the bass? I think that as the filter is now the middle range should not be more withdrawn than it is, I could even have it a bit more forward to be honest. So, if a bigger coil will do that it is out of the question for my taste, it is better left as it is.
Also I should mention I am happy with the speakers, no doubt about that. It makes me thinking of trying to make a construction all by myself next time, since I am rather sure I will build a new pair some day.
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