Yes, phasiness is the real "gotcha" of multi-driver omni, or "bipole" systems. (Bipole annoys me because this is a marketing term - there's no such thing as a "bipole" microphone, after all.)
The really significant difference between Walsh/MBL radial drivers is single-point radiation versus the chaotic arrivals of multi-driver omni speakers. The multi-driver systems are phasey and diffuse regardless of listening angle, while the single-point systems are crisp, sharp, and even more spacious-sounding, with a much more natural presentation.
With rear tweeter, impulse measurements are a necessity, to insure the front impulse is not getting all messed up with diffracted and delayed waves from the rear tweeter. As you mentioned, it takes a fair amount of rear-tweeter attenuation and frequency-shaping to avoid degrading the front arrival.
The really significant difference between Walsh/MBL radial drivers is single-point radiation versus the chaotic arrivals of multi-driver omni speakers. The multi-driver systems are phasey and diffuse regardless of listening angle, while the single-point systems are crisp, sharp, and even more spacious-sounding, with a much more natural presentation.
With rear tweeter, impulse measurements are a necessity, to insure the front impulse is not getting all messed up with diffracted and delayed waves from the rear tweeter. As you mentioned, it takes a fair amount of rear-tweeter attenuation and frequency-shaping to avoid degrading the front arrival.
Thanks for taking the time to explain and expand on this. I have all the divers I need for an OB, inspired by this thread and MJK's recent article. The cotton waste and pillow cases are inexpensive and I have some F13 felt, mdf and ply. Maybe it's time to push my mate out of his workshop for an afternoon and make some sawdust.Lynn Olson said:
FWIW, my the real system I ever heard was stacked Quad 57's, but the ultimate dymanics and bass left me wanting more. But what they did well, they did very well.
''The really significant difference between Walsh/MBL radial drivers is single-point radiation versus the chaotic arrivals of multi-driver omni speakers. The multi-driver systems are phasey and diffuse regardless of listening angle, while the single-point systems are crisp, sharp, and even more spacious-sounding, with a much more natural presentation.''
My mini omnis are 3.5inch full rangers and don't sound phasey at all. Only larger than their stature, with a very mild loss in focus, but with a very welcome rendition of envelope tail. Multi driver omnis suck.
My mini omnis are 3.5inch full rangers and don't sound phasey at all. Only larger than their stature, with a very mild loss in focus, but with a very welcome rendition of envelope tail. Multi driver omnis suck.
New Gradient Helsinki
Now here's something completely different:
http://www.6moons.com/news/news.html
scroll down just a little...
Now here's something completely different:
http://www.6moons.com/news/news.html
scroll down just a little...
Hello Mr. Olson,
are you still considering the tonetubby alnico for the low section? I'm asking because I've seen some 15' alnico guitar drivers made by Weber here. Unfourtunately no specs, he makes them by ear, however they are quite aclaimed in some comparisons I've read against celestion and others. So I asume the region up to 1Khz it's nice and clean, while the break-up point is controled by various design aspects. He even makes them custom, to the tone you want of course
.
And what are the crossover points for the woofer(s)? As I understand there will be a low pass at the point the midbass rolls-off because of the OB and then another low pass at around 1Khz for the midbass and the woofers?
edit: a friend of mine, memeber on this forum auditioned some 15' webers and he could make a comparison to his own eminences 15' in open baffle. He was quite impressed. In fact very impressed. I know he prefers warm bass though, so I have a slighty reticence because I didn't listened to a guitar driver (rich armonics and so on) with usual music content.
are you still considering the tonetubby alnico for the low section? I'm asking because I've seen some 15' alnico guitar drivers made by Weber here. Unfourtunately no specs, he makes them by ear, however they are quite aclaimed in some comparisons I've read against celestion and others. So I asume the region up to 1Khz it's nice and clean, while the break-up point is controled by various design aspects. He even makes them custom, to the tone you want of course
.And what are the crossover points for the woofer(s)? As I understand there will be a low pass at the point the midbass rolls-off because of the OB and then another low pass at around 1Khz for the midbass and the woofers?
edit: a friend of mine, memeber on this forum auditioned some 15' webers and he could make a comparison to his own eminences 15' in open baffle. He was quite impressed. In fact very impressed. I know he prefers warm bass though, so I have a slighty reticence because I didn't listened to a guitar driver (rich armonics and so on) with usual music content.
Re: Re: Re: There is one thing to be said for the subjective
This statement has some real problems inherent in it. I think we can agree that no system is perfect and therefore it follows that all are inaccurate. The only category left is "it isn't". Attempting to rank or rate within this latter category is exactly in the middle ground.
Unless perfect, measurements will require some interpretation or at least some assignment of relative importance. As soon as this occurs you're in that subjective middle ground, like it or not.
gedlee said:
This statement has some real problems inherent in it. I think we can agree that no system is perfect and therefore it follows that all are inaccurate. The only category left is "it isn't". Attempting to rank or rate within this latter category is exactly in the middle ground.
Unless perfect, measurements will require some interpretation or at least some assignment of relative importance. As soon as this occurs you're in that subjective middle ground, like it or not.
Re: Re: Re: There is one thing to be said for the subjective
The speaker system is either accurate to an electrical signal or not. A speaker that is accurate to a signal is not necessary reproducing the original event as close to the original as possible if the original source had some form of highpass or other purposeful limitation used that rolled off the low end to account for limitations of the then-current playback systems or because the engineer preferred to slightly emphasize the midband, not unheard of. But this does move into perception and preferences, on that I'm sure that we agree. This is just one example. Then, of course, there are the various mics and tecniques employed that further complicate any attempts for accurate playback of the original event.
But in the end, what is a playback system for other than enjoyment of a less-than-perfect reproduction of the original? I did away with electronics that have any form of tone control years ago, but when I've used an active subwoofer with an Fc of 45Hz in my system, I frequently change the gain setting ever so slightly from recording to recording due to my perception of the low end in my room. Maybe my room just has too much influence in this area and I am compensating for that deficiency. Maybe I'm over- or under-emphasizing this area, I don't know and will never know, because I cannot prove what the original event had for the low end. I believe that no one can, in fact. A system that has limited low end extension is by default, for most recordings, never reproducing even what's on the recording, mush less the original event. So most (dare I say all?) systems are compromises from the start.
Dave
gedlee said:
The speaker system is either accurate to an electrical signal or not. A speaker that is accurate to a signal is not necessary reproducing the original event as close to the original as possible if the original source had some form of highpass or other purposeful limitation used that rolled off the low end to account for limitations of the then-current playback systems or because the engineer preferred to slightly emphasize the midband, not unheard of. But this does move into perception and preferences, on that I'm sure that we agree. This is just one example. Then, of course, there are the various mics and tecniques employed that further complicate any attempts for accurate playback of the original event.
But in the end, what is a playback system for other than enjoyment of a less-than-perfect reproduction of the original? I did away with electronics that have any form of tone control years ago, but when I've used an active subwoofer with an Fc of 45Hz in my system, I frequently change the gain setting ever so slightly from recording to recording due to my perception of the low end in my room. Maybe my room just has too much influence in this area and I am compensating for that deficiency. Maybe I'm over- or under-emphasizing this area, I don't know and will never know, because I cannot prove what the original event had for the low end. I believe that no one can, in fact. A system that has limited low end extension is by default, for most recordings, never reproducing even what's on the recording, mush less the original event. So most (dare I say all?) systems are compromises from the start.
Dave
In earlier texts, there has been suggestion for a 'cascade' of LF filters.
It has been my experience that where say a supertweeter is taken off after the main tweeter crossover, or low bass is taken off after the main full bass crossover, that dynamic current flow variation in the reactive crossover/driver circuit of the lower frequency partner of the drivers always distorts the current waveform flowing in the higher frequency circuit.
Thus it is better for every driver to have its own individually tailored frequency determining network with bi, tri, quad etc. wiring as necessary, or a separate bass plate amplifier where the amplitude response and phase compensation can be easily pre-set.
Cheers ......... Graham.
It has been my experience that where say a supertweeter is taken off after the main tweeter crossover, or low bass is taken off after the main full bass crossover, that dynamic current flow variation in the reactive crossover/driver circuit of the lower frequency partner of the drivers always distorts the current waveform flowing in the higher frequency circuit.
Thus it is better for every driver to have its own individually tailored frequency determining network with bi, tri, quad etc. wiring as necessary, or a separate bass plate amplifier where the amplitude response and phase compensation can be easily pre-set.
Cheers ......... Graham.
Russell and Frank
Its nice to see people who have agrasp on what I am talking about.
Russell you clearly understand the marked distinction between the art and the reproduction - alas this is lost on so many. You do the art, I do the reproduction. When we understand each other and work together we can achieve the best possible situation. You are absolutely correct to aim at the perfectly transparent accurate loudspeaker, because to do otherwise is foley - even if such an ideal does not exist (although I would also agree with you that we are geting much closer.)
Unfortunately I think that your statement "as long as speaker manufacturers (in particular) have accuracy ... as the target which I believe they do" is optimistic on the whole. I am continually disappointed with the vast belief that "accuracy" is not the goal - that it is some personal nervana that should be sought.
Jeff - "As soon as this occurs you're in that subjective middle ground, like it or not." Yes, of course what you say is true in absolute terms. But my point is that it is unacceptable to argue that "a little" manipulation for personal taste is OK and to knowingly change the playback system and still call it "accurate". The fact that the absolute cannot be obtained is not a justfication to give up the goal.
Its nice to see people who have agrasp on what I am talking about.
Russell you clearly understand the marked distinction between the art and the reproduction - alas this is lost on so many. You do the art, I do the reproduction. When we understand each other and work together we can achieve the best possible situation. You are absolutely correct to aim at the perfectly transparent accurate loudspeaker, because to do otherwise is foley - even if such an ideal does not exist (although I would also agree with you that we are geting much closer.)
Unfortunately I think that your statement "as long as speaker manufacturers (in particular) have accuracy ... as the target which I believe they do" is optimistic on the whole. I am continually disappointed with the vast belief that "accuracy" is not the goal - that it is some personal nervana that should be sought.
Jeff - "As soon as this occurs you're in that subjective middle ground, like it or not." Yes, of course what you say is true in absolute terms. But my point is that it is unacceptable to argue that "a little" manipulation for personal taste is OK and to knowingly change the playback system and still call it "accurate". The fact that the absolute cannot be obtained is not a justfication to give up the goal.
No builds???
Ahh.. but it's sooo refreshing to see the time honored "subjective vs. objective" {discussion} in all its myriad forms re-emerge...
Being in the OB camp myself, it would be interesting to see someone else's build progress... maybe I could pick up a pointer or two ..
John L. (auplater)
Andy Graddon said:
Ahh.. but it's sooo refreshing to see the time honored "subjective vs. objective" {discussion} in all its myriad forms re-emerge...
Being in the OB camp myself, it would be interesting to see someone else's build progress... maybe I could pick up a pointer or two ..
John L. (auplater)
Accuracy
Just a quick note as it's much too late and I can hardly keep my eyes open so this might be just garbage when I read it tomorrow, later today or whenever.
The absolute best we can accomplish with this or any other speaker system is to reproduce what is on the cd, record, tape, etc., good bad or indifferent. The guy making the decisions for you could be a doper with a lop sided mixer board and old Altec monitors.
We all know this but continue to think that we have tastes and should temper the system to accomplish a better sound. The tube guys with their "warm" (read distorted) sound have been doing that for years. Not a slam against tube guys I love them, too. Accuracy is in solid state like it or not. Personal taste is in the music not how it is reproduced. There is no adjective that should ever enter the equation. To get, "I want to hear it as if it's live" is meaningless, also. It's either re-producing correctly or it isn't.
Of course that is the problem as we only have prejudiced ears to approach that goal.
Zene
Just a quick note as it's much too late and I can hardly keep my eyes open so this might be just garbage when I read it tomorrow, later today or whenever.
The absolute best we can accomplish with this or any other speaker system is to reproduce what is on the cd, record, tape, etc., good bad or indifferent. The guy making the decisions for you could be a doper with a lop sided mixer board and old Altec monitors.
We all know this but continue to think that we have tastes and should temper the system to accomplish a better sound. The tube guys with their "warm" (read distorted) sound have been doing that for years. Not a slam against tube guys I love them, too. Accuracy is in solid state like it or not. Personal taste is in the music not how it is reproduced. There is no adjective that should ever enter the equation. To get, "I want to hear it as if it's live" is meaningless, also. It's either re-producing correctly or it isn't.
Of course that is the problem as we only have prejudiced ears to approach that goal.
Zene
Re: Accuracy
I agree almost completely - certainly as far as the subjective ideas are concerned. I really like "there is no adjective ..."
But, it is not assurded that solid state are more accurate than tubes. Sure they have lower THD - much lower in many cases, but the distortions that they tend to have are of the most audible variety. The measurements here (standard ones that is) simply do not tell the whole story. Crossover distortion is the most insidious form of distortion and is not even marginally masked by the loudspeakers distortion. Tube amps "tend" to have much lower values of this kind of distortion than SS and yet tubes do have high levels of low order distortion, but loudspeakers also have this in abundance. Neither of these low order distortion mechanisms are highly audible.
There are strong cases to be made for tubes, but the stronger case is to simply make the SS amp correctly. It can certainly be done.
Zene Gillette said:
I agree almost completely - certainly as far as the subjective ideas are concerned. I really like "there is no adjective ..."
But, it is not assurded that solid state are more accurate than tubes. Sure they have lower THD - much lower in many cases, but the distortions that they tend to have are of the most audible variety. The measurements here (standard ones that is) simply do not tell the whole story. Crossover distortion is the most insidious form of distortion and is not even marginally masked by the loudspeakers distortion. Tube amps "tend" to have much lower values of this kind of distortion than SS and yet tubes do have high levels of low order distortion, but loudspeakers also have this in abundance. Neither of these low order distortion mechanisms are highly audible.
There are strong cases to be made for tubes, but the stronger case is to simply make the SS amp correctly. It can certainly be done.
Re: No builds???
I have 2 other projects to finish first, but then I'm into a full OB experiment, with 15" PA bass.
I'm going to actually build it and use my ears ........ see what happens............. lots of lovely theory and opinion here, but ...... !!
auplater said:
Ahh.. but it's sooo refreshing to see the time honored "subjective vs. objective" {discussion} in all its myriad forms re-emerge...
Being in the OB camp myself, it would be interesting to see someone else's build progress... maybe I could pick up a pointer or two ..
John L. (auplater)
I have 2 other projects to finish first, but then I'm into a full OB experiment, with 15" PA bass.
I'm going to actually build it and use my ears ........ see what happens............. lots of lovely theory and opinion here, but ...... !!
Earl,
do you have a special technique to assess crossover distortion? Is there a way measuring it using standard soundcard techniques / software?
Also, you mentioned developing amp distortion measurement techniques that go 20 dB below the usual THD based measurements, I found that very interesting (and no one commented on it). How do you do this?
do you have a special technique to assess crossover distortion? Is there a way measuring it using standard soundcard techniques / software?
Also, you mentioned developing amp distortion measurement techniques that go 20 dB below the usual THD based measurements, I found that very interesting (and no one commented on it). How do you do this?