Joe, really - you need to get out more. Measurements are not just for frequency response any more.
There's phase, harmonic levels vs freq., IMD, distortion vs power, Waterfall, CSD, impulse, etc. So many ways to look at the thing. They don't tell you "how it sounds" unless you are very familiar with these measurements, but they do show meaningful differences, if they exist.And Art has a clever and simple recording technique that would allow you to hear and judge the before and afters. Maybe not as good as being there, but certainly a very handy tool. What's not to like?
Well, I just went out...and at my front door was my new Audio Precision APx525!!
Seriously....just got it.
That's GIP 18"s and an Audio Pre in two days!
I should do this more often!
I'm not going to use the AP to find out how things sound. Got ears for that.
Same with CLIO. trying to get Room EQ Wizard set up too.
This box is to check for production problems and produce accurate specs for a line of pro audio gear jc morrison and I are putting together.
I agree that some meaningful correlations can be made between measurements and sonics, but not if you haven't heard the speaker and only have the graphs.
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If there are difference in the sound (real differences) I guarantee you we will see them in the graphs.
Congrats on the AP, that's quite a piece of kit!
There seems to be a reluctance on the part of the ones doing the "testing" to do much if anything in the way of measurements which I find puzzling since they were the ones talking about the "scientific method" a few posts back. If all they are going to do is "listen" then it's a lost cause. I guess they aren't interested in discovering the WHY of how it works, that is if it does. Go figure. I'll check back in a few more days/weeks to see if they change their mind. Perhaps like you stated earlier "don't hold your breath"
100% Guaranteed.
Especially if "real differences" is defined as differences that will show up in measurements.
Tautology much?
Pano, you really need to break out of the hermeneutic circle more...
Yeah, that's why I have a $13k piece of test gear.
I guess I'll just use it as a bong stand...WTF?
If I am trying to sell a product as a company for big loot, I feel obligated to check it out.
However, I doubt DavidL will be on my customer lists. Surely he will go after well-measured items that did well against high dollar stuff in DBT tests even though it only costs $19.
Hey DavidL...I just posted two measurements a few posts back. Are you finished with those already? Did you like the speaker?
For myself, I do measurements to make sure things are basically working as intended and sometimes also in a conversation with the design process but since I am working to please myself, I am not in the measurement race.
When I was building every day and had the space, I had a small lab set up for audio.
I found the links between what I was hearing and seeing on the scope very vague.
Had an HP 334A... cool machine but it was entirely useless for determining how things sounded, particularly after I started building SE amplifiers.
Now with complex distortion spectra measurement and so on at my fingertips, measurements might be a bit more useful as an accompanying data set to flesh out listening impressions.
jc morrison, our designer, is heavy into measuring because he istotally in the measurement race, especially pushing the limits of tube and hybrid low noise front ends. He also loves getting crazy gain out of a single stage with low distortion and engineered harmonic spectra. It is part of the sport and art for him.
I got to admit that jc absolutely seems to know what he is doing so I just stand back and let him do his thing. Same with his partner Dr. Bae,our Korean engineer, who has a PhD in solid state physics. I can't keep up with these guys if I tried.
In the end, it comes down to subjective part swaps and ear joy...but the kind of things these guys build, you can't simply wing it.
Image Hi Fi said jc's C-100 preamp design was the lowest noise tube preamp they ever measured. That is something that can't be achieved by ear.
It is also something that can't be achieved by generalized top-down thinking. jc's biggest asset is his creative imagination and intuition not his test gear or his SPICE rig.
He was a philosophy major, as well as a design engineer, hence he knows all about the subtleties of "scientific process."
So the role of measurements, I think, is related to the goals and intentions of the people doing the work.
I figure as long as you don't have to answer to anybody else, do whatever you want.
I have built some excellent sounding simple gear with nothing but a Fluke 8060A to check DC voltages but I wouldn't make any claims for such aside from "I like it."
Well since you put it THAT way......why yes
If it beats out the pricey stuff then I'd be a fool not to.I honestly don't get the hostility Mr Roberts. I never claimed the field coil was worse/equal to/better than a regular magnet speaker.You and others were the ones making subjective claims and all myself and a few others wanted was some data to back up the claims.
I'm sure Floyd Toole would be interested in that way of looking at it.
Fair enough, I guess what you are saying is, you can make subjective claims all day long and you don't care about showing some real data to back it up
Now you're just being silly. Of course I meant real differences that you can actually hear (not imagine). As to what you might prefer, that's harder to predict.
Anyone who's been in this for any period of time knows measuring differences is easy, interpreting them much harder. I was watching a recent interview with an audio designer and was very surprised to hear him back away from and downplay the importance of distortion, for example, claiming they pay little attention to it. That designer was Sean Olive.
If switching over to the notion of expert listeners didn't already do it, that might just banish him from the circle of 'real' experts.
If switching over to the notion of expert listeners didn't already do it, that might just banish him from the circle of 'real' experts.
There's no reason to do favours for people who only know how to badger and hector, and anyone who knows who Sean Olive is would never ask about DBT. A little independent research might expand your horizons.
Uff da. Well THAT was a boring read. I just finished piling through this entire thread, and found not one useful piece of information on the actual nuts and bolts approach to shoehorning a field coil into an existing design. Having said that, here's my 2 cents: The one thing that field coils have going for them that a permanent magnet motor system will NEVER have is the ability to change the strength and "quality" of the static magnetic field by simply changing the supplied voltage. This in itself represents a significant advantage.
I have listened to relatively few field coils because modern designs are rare. Those I have heard were quite good sounding. Are they better than the possible permanent magnet counterparts? Can't say I know for sure- there were none on offer. I will say I find the concept intriguing, because I have more than a couple dead compression drivers lying about waiting to have their Alnico magnets recharged. Permanent magnets aren't so permanent, it seems…
Having played with both "permanent" and electrically polarized magnets quite a bit in my lifetime, I would sum up the differences between the different systems is as follows:
In a "permanent" magnet motor system, there are huge differences in the way that the various materials used have on the conditions present in the magnetic gap, both static and dynamic. The distinct advantage an electromagnet has compared to a permanent magnet, is the field can be adjusted to suit after the driver has been put into service. Electromagnets also exhibit less field gradient- they have a more uniform magnetic field than a high energy permanent magnet. This makes maintaining a linear field in the gap a simpler proposition. A more linear field will equate to lower distortion, all else being equal- but there are additional complications to consider as well.
Any permanent magnet exposed to an AC field will react to that field. It wants to resist the attempts of the outside field to change the magnetic domains in its structure. It is this resistance that creates the relative motion that propels the collection of parts that produce the sound we wish to reproduce! Anything that changes the relationship of these two opposing fields will have an effect on the output. Permanent magnets all vary in their success to opposing this magnetic influence. The net result is that some magnetic materials will produce a more linear reaction to an applied signal than others. It follows that this will result in a difference in behavior between motors utilizing different magnetic materials.
In an electromagnet, to a large degree these factors are at the whim of the power supply creating the magnetic field! Anything that impresses itself upon the field emanating from the electromagnet will also impress itself upon the field coil supply. The loudspeaker can now be viewed as a simple transformer with the primary represented by the voice coil, and the secondary represented by the magnetic circuit, and in the case of a field coil, the coil itself. The physics of this relationship are both elementary and universally well documented.
The advantage to this approach is the fact that it is a simple matter to change the dynamic behavior of a power supply… Not so with a permanent magnet.
I have listened to relatively few field coils because modern designs are rare. Those I have heard were quite good sounding. Are they better than the possible permanent magnet counterparts? Can't say I know for sure- there were none on offer. I will say I find the concept intriguing, because I have more than a couple dead compression drivers lying about waiting to have their Alnico magnets recharged. Permanent magnets aren't so permanent, it seems…
Having played with both "permanent" and electrically polarized magnets quite a bit in my lifetime, I would sum up the differences between the different systems is as follows:
In a "permanent" magnet motor system, there are huge differences in the way that the various materials used have on the conditions present in the magnetic gap, both static and dynamic. The distinct advantage an electromagnet has compared to a permanent magnet, is the field can be adjusted to suit after the driver has been put into service. Electromagnets also exhibit less field gradient- they have a more uniform magnetic field than a high energy permanent magnet. This makes maintaining a linear field in the gap a simpler proposition. A more linear field will equate to lower distortion, all else being equal- but there are additional complications to consider as well.
Any permanent magnet exposed to an AC field will react to that field. It wants to resist the attempts of the outside field to change the magnetic domains in its structure. It is this resistance that creates the relative motion that propels the collection of parts that produce the sound we wish to reproduce! Anything that changes the relationship of these two opposing fields will have an effect on the output. Permanent magnets all vary in their success to opposing this magnetic influence. The net result is that some magnetic materials will produce a more linear reaction to an applied signal than others. It follows that this will result in a difference in behavior between motors utilizing different magnetic materials.
In an electromagnet, to a large degree these factors are at the whim of the power supply creating the magnetic field! Anything that impresses itself upon the field emanating from the electromagnet will also impress itself upon the field coil supply. The loudspeaker can now be viewed as a simple transformer with the primary represented by the voice coil, and the secondary represented by the magnetic circuit, and in the case of a field coil, the coil itself. The physics of this relationship are both elementary and universally well documented.
The advantage to this approach is the fact that it is a simple matter to change the dynamic behavior of a power supply… Not so with a permanent magnet.
I have an AP too. What have you in your lab? Which "secrets" did you discover about WHYs? Do you want to share with us?
Not that easy, otherwise we had ONE amplifier, ONE loudspeaker, ONE...
True Scientific method seems to be hostile to you. It seems that for you it's easier to comment other's results-opinions. I see no positive attitude here.
But it is so easy... No mumbo jumbo. You have a theory, I suppose. I do.
So the next step is to try. From the results we must check the difference between what's expected and the results. We change the theory if needed and we try again. Everything must be done in a repeatable way.
Ops, the result is subjective... It's a matter of taste...
Maybe this is the reason you don't need to try...
So enjoy your favourite Music first. Be relaxed.
I do it right now... A great SACD from Divox (Vivaldi).
I agree, those are the main aspects for me too.
Joe has an AP more precise than mine, he can try to test distorsion better than me. For example with the 802 he is going to convert.
But he must be sure the gauss in the gap are the same (first).
And this must be true for any good PSU. A super PSU should offer a better behaviour in the sense you wrote about.
I am not that convinced...
I'm sure an AP525 can see something. But not that convinced what it shows is what we hear..
If one wants to see differences in the measured results using a field coil, they need only dial back the current to the coil. That is what makes the entire argument so ridiculous. Changing the measured parameters of the driver and its motor behaviors is simply a foregone conclusion when electromagnets are involved. We are replacing a countering force whose properties are determined by a series of relatively fixed interplays at the atomic level with one that has a far simpler and malleable dynamic behavior. To a much larger degree, an electromagnet has compromises that are external to the loudspeaker system, and are thus easily countered or manipulated to our benefit. Not so with a permanent magnet.
Every parameter that can be affected by variances in the field strength is available to the end user. The only thing that DOESNT change are the aspects determined by the mechanical constants in the moving parts of the system. Everything else is up for grabs, to varying degrees.
Every parameter that can be affected by variances in the field strength is available to the end user. The only thing that DOESNT change are the aspects determined by the mechanical constants in the moving parts of the system. Everything else is up for grabs, to varying degrees.
I can see a variable supply to a field coil being a useful tool at the develpment phase. Lets see how we like the curve at 8,000, 10,000, and 12,000 Gauss. Once decided, I don't see any great advantage to having a variable supply. Clearly the vast majority of field coils ever sold were made with fixed supplies set to an "optimum" setting.
The question was not whether variability was an advantage but whether field coils had some manner of better performance than a permanent magnet circuit. In other words, once set to the same flux and giving the same sensitivity and Q, are there any identifiable differences and will the field coil have an audible superiority? No one here has given any plausible evidence of that being the case. We see no distortion curves (in my mind the only plausible area of differences) of one versus the other.
"Compromises external to the system" doesn't sound like an advantage. Neither should we assume that an external power supply offers some advantage. The current demands of the field coil will be very constant and a power supply stiffness will not make a difference, considering the high impedance of the coil itself.
The only interesting differences between magnet materials are their reaction to AC. Both the magnetic material and the iron circuit will allow some impression of the AC signal on the static field. In and off itself, this is not an issue, as it may result in only a slight loss of sensitivity. It is only when the operating point softness is connected with major nonlinearity that we have anything to talk about. This was the case with simple ferrite structures and can be fixed with shorting rings as JBL and McIntosh do. These fixes drop magnetic circuit distortion to the point where it is well below the typical cone distortions. (Note that 90+% of the units on the market do not have these fixes.)
Without like vs. like measurements, especially of distortion, we have no basis to claim that field coil units have any performance advantage.
David
The question was not whether variability was an advantage but whether field coils had some manner of better performance than a permanent magnet circuit. In other words, once set to the same flux and giving the same sensitivity and Q, are there any identifiable differences and will the field coil have an audible superiority? No one here has given any plausible evidence of that being the case. We see no distortion curves (in my mind the only plausible area of differences) of one versus the other.
"Compromises external to the system" doesn't sound like an advantage. Neither should we assume that an external power supply offers some advantage. The current demands of the field coil will be very constant and a power supply stiffness will not make a difference, considering the high impedance of the coil itself.
The only interesting differences between magnet materials are their reaction to AC. Both the magnetic material and the iron circuit will allow some impression of the AC signal on the static field. In and off itself, this is not an issue, as it may result in only a slight loss of sensitivity. It is only when the operating point softness is connected with major nonlinearity that we have anything to talk about. This was the case with simple ferrite structures and can be fixed with shorting rings as JBL and McIntosh do. These fixes drop magnetic circuit distortion to the point where it is well below the typical cone distortions. (Note that 90+% of the units on the market do not have these fixes.)
Without like vs. like measurements, especially of distortion, we have no basis to claim that field coil units have any performance advantage.
David
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