Flexible wall cabinets will certainly have an effect on impedance sweeps of speaker. Resonance peaks of the Hypercube will show up. If I had a working impedance sweep capability I would expect a peak near 2.2kHz in my example. Sadly I burned out the line in on my PC soundcard from over excitation.
I have seen ripples and extra peaks appear before bracing and went away with bracing added. I have even seen peaks appear due to a flexing Karlsonator wing.
I have seen ripples and extra peaks appear before bracing and went away with bracing added. I have even seen peaks appear due to a flexing Karlsonator wing.
"The amount of damping a finger tip has on a violin string is minimal" and "The placement, pressure and movement of the finger tips on a violin or guitar is to ... increase / decrease the decay": Is this not a contradiction?
But more seriously, bypassing the comments on phase... "Treating sound waves as sine waves is fundamentally flawed": Are you sure? Interestingly in the quoted publication, John Watkins references Michael Gerzon: For anybody still stuck on linear system theory, sine waves and how they can be used to analyse what we hear and subsequently perceive, I strongly recommend Michael Gerzon's AES paper "Super Resolving Short-Term Spectral Analyzers".
In this far-too-often glossed over paper, Gerzon presents a model of the hearing process that includes both super-resolving (time-domain biased) and sub-resolving (frequency-domain biased) and the gradual transformation between the two. In this all-encompassing linear model (at least as far as first order spectra go - he also had higher orders covered too!), sine waves are ever present in the analysis and the analysis is no less correct for being so.
But more seriously, bypassing the comments on phase... "Treating sound waves as sine waves is fundamentally flawed": Are you sure? Interestingly in the quoted publication, John Watkins references Michael Gerzon: For anybody still stuck on linear system theory, sine waves and how they can be used to analyse what we hear and subsequently perceive, I strongly recommend Michael Gerzon's AES paper "Super Resolving Short-Term Spectral Analyzers".
In this far-too-often glossed over paper, Gerzon presents a model of the hearing process that includes both super-resolving (time-domain biased) and sub-resolving (frequency-domain biased) and the gradual transformation between the two. In this all-encompassing linear model (at least as far as first order spectra go - he also had higher orders covered too!), sine waves are ever present in the analysis and the analysis is no less correct for being so.
Selective editing is a wonderful thing!
😉
Yes....The way you have edited my post!
My unedited post is accurate as it explains that the fingers move up and down to change the effective length (different notes) of the string.
However, my point is the amount of "dampening" is minimal.
For example if a soloist wears different finger protectors (cotton, silk, rubber etc) the tone is subtly altered....Not completely changed or muted altogether.
Michael Gerzon has written a lot of interesting material, and like John Watkinson some very controversial material!
Broadly, they agree on the greater importance of time domain over frequency domain when looking at loudspeaker design.
Where they tend to differ is in the importance of analysing sine waves when correlating sound quality with objective measurements.
I tend to agree with John on most issues and disagree with a lot of Michaels thinking.....Horses for courses....But I will put my loudspeakers up against Michaels loudspeakers anywhere, any time, any place....Then we will see who is right!
Cheers
Derek.
😉
Yes....The way you have edited my post!
My unedited post is accurate as it explains that the fingers move up and down to change the effective length (different notes) of the string.
However, my point is the amount of "dampening" is minimal.
For example if a soloist wears different finger protectors (cotton, silk, rubber etc) the tone is subtly altered....Not completely changed or muted altogether.
Michael Gerzon has written a lot of interesting material, and like John Watkinson some very controversial material!
Broadly, they agree on the greater importance of time domain over frequency domain when looking at loudspeaker design.
Where they tend to differ is in the importance of analysing sine waves when correlating sound quality with objective measurements.
I tend to agree with John on most issues and disagree with a lot of Michaels thinking.....Horses for courses....But I will put my loudspeakers up against Michaels loudspeakers anywhere, any time, any place....Then we will see who is right!
Cheers
Derek.
I was at a stringed musical instrument store and the owner challenged me to make a foam core cello after hearing about my speakers. Someone should make a thin tone wood (spruce?) Hypercube.
Gentlemen:
These are excellent suggestions. I can tell you that back in the late 70s I made some from door skin, which was quite thin (1/8 inch), with 4 inch fullranges for car speakers. They were *very* good subjectively without any equalization or filtering. I would love to see someone make and test thin Hypercubes.
These are excellent suggestions. I can tell you that back in the late 70s I made some from door skin, which was quite thin (1/8 inch), with 4 inch fullranges for car speakers. They were *very* good subjectively without any equalization or filtering. I would love to see someone make and test thin Hypercubes.
Tesserax,
Didn't you say you've made sheet metal versions? If re-radiation is the goal then I would think that would be pretty good. However, if thin and stiff is what you want (I think you said that was your thought the beginning of all this), why not make one out of single ply carbon fiber? It would be very thin, light weight (is that desirable too? For your purposes it seems like it would be, since more panel movement would occur due to lower momentum of the panel), and stiff (for the given thickness).
Didn't you say you've made sheet metal versions? If re-radiation is the goal then I would think that would be pretty good. However, if thin and stiff is what you want (I think you said that was your thought the beginning of all this), why not make one out of single ply carbon fiber? It would be very thin, light weight (is that desirable too? For your purposes it seems like it would be, since more panel movement would occur due to lower momentum of the panel), and stiff (for the given thickness).
However, I'm still not so sure so much sound radiating from the enclosure would be a good thing (I kinda feel like that's what we're trying to show here, maybe it's just what I care about the most. I still want to build these, I just want to know the limitations to properly design it). xrk971 is right that the sound from directly in front of the speaker is very low in distortion (thank you for pointing that out) and has a great transient response (which I'm convinced is a great property to have in a speaker), but the sound coming from directly behind is full of distortion (I'm pretty sure this is a property of sound radiated from an enclosure panel) and I'm still not convinced that the sound measured from the sides isn't just a property of the small enclosure baffle and speaker beaming. I think that if these speaker enclosures radiated a lot, that is a lot more than we've already seen, it would not sound great in the long term due to increased distortion. I have not seen evidence to the contrary here. If anyone else has, please point me to it.
To get back to my point about diffraction and/or driver beaming, it occurred to me to look at the driver datasheet and compare it to xrk971's off axis measurements in post #190. At 30° (the only angle common to both), it looks to me like the roll off of the high end starts at about the same place, and the roll off is about twice the rate in xrk971's measurements. If the manufacture's measurements were taken on an "infinite" baffle, it would be operating in half space, while xrk971's measurements were most likely in full space. Full vs. half space would explain the rate difference. Therefor, I see no deviation from standard theory and no indication that the enclosure is adding to the radiated sound, except where there is a resonance in the back four panels which shows up as a peak in the 0° response.
I hope this doesn't come across as overly kurt, I have a hard time telling tone in my own text. My intent is to state what I can see in the data and why and discuss it with others.
To get back to my point about diffraction and/or driver beaming, it occurred to me to look at the driver datasheet and compare it to xrk971's off axis measurements in post #190. At 30° (the only angle common to both), it looks to me like the roll off of the high end starts at about the same place, and the roll off is about twice the rate in xrk971's measurements. If the manufacture's measurements were taken on an "infinite" baffle, it would be operating in half space, while xrk971's measurements were most likely in full space. Full vs. half space would explain the rate difference. Therefor, I see no deviation from standard theory and no indication that the enclosure is adding to the radiated sound, except where there is a resonance in the back four panels which shows up as a peak in the 0° response.
I hope this doesn't come across as overly kurt, I have a hard time telling tone in my own text. My intent is to state what I can see in the data and why and discuss it with others.
Muddjester,
Your comments are fair and I certainly would not want anyone to refrain from posting potential problems. In fact, since you bring up carbon fiber perhaps it would be right at this point for me to relate the story of the ONE time this enclosure failed me, or, more to the point, was misapplied by my own inexperience, due to my own over-optimism. This has nothing to do with the Hardees speaker story of too much microphonic sensitivity, which as xrk pointed out was not exactly a bad sign, merely inconvenient in their particular application. This is a cautionary tale about the limits of the design.
In the 1990's I, too, thought it might be a good idea to use carbon fiber enclosures for their combination of stiffness and lightness. We entered into communication with persons at the FERRO corporation (Ferro Home), a firm that works, among other products, with high performance materials including graphite composite used for jet fighter wings.
This material is like long-fiber carbon cloth tape impregnated with a thermosetting epoxy. Since we were unfamiliar with gluing this material, the good folks at FERRO agreed to cut the pieces and form the subassemblies and then attach them to make complete enclosures for us. It was a non-trivial commitment of time and money and far more than we as relative unknowns deserved, really.
At the time I was trying to interest Maryland Sound Industries (Maryland Sound Production & Event Production Company | Audio Production) in using our design for the touring concert sound systems they transport and set up for major performing artists. One of their most popular units in these setups was a combination of a box with 4 JBL pro sound woofers and a box on top of this with a large hornloaded tweeter. Knowing that they stored and used large numbers of this unit we really wanted to show them an alternative using the same drivers.
The resulting square-truncated rhombic dodecahedra were huge. Imagine a square baffle plate large enough to hold four ten or twelve inch woofers in a square array. This was back in the days when I foolishly thought that "size doesn't matter" so I did not realize the problem I was building into this incarnation of the design.
The enclosures, fully formed with precut baffle openings, were shipped to us and we transported them to the MSI headquarters, where their technicians inserted the woofers and electronic crossovers to run a simple test.
When they were finally energized it was, to put it mildly, a debacle. There was SO much air behind the woofers that they had no air spring at all to provide proper restoring force. They were too loose and actually buzzed loudly, humiliating us in front of the MSI personnel. Needless to say, no deal was forthcoming after that. It was a bitter lesson in the practical side of speaker design that I will never forget, and a badly-needed reminder that ALL designs have their practical limitations. The Hypercube is no exception.
Feel free to laugh; I make no excuses for this failure. It drove home to me the fact that the volume inside a loudspeaker enclosure is not a meaningless constant. The nature of the shape is such that it is hard to have too little volume....but it is always possible to have way too much. Fortunately, fitting the baffle approximately to the woofer in single-woofer designs usually avoids such problems.
Your comments are fair and I certainly would not want anyone to refrain from posting potential problems. In fact, since you bring up carbon fiber perhaps it would be right at this point for me to relate the story of the ONE time this enclosure failed me, or, more to the point, was misapplied by my own inexperience, due to my own over-optimism. This has nothing to do with the Hardees speaker story of too much microphonic sensitivity, which as xrk pointed out was not exactly a bad sign, merely inconvenient in their particular application. This is a cautionary tale about the limits of the design.
In the 1990's I, too, thought it might be a good idea to use carbon fiber enclosures for their combination of stiffness and lightness. We entered into communication with persons at the FERRO corporation (Ferro Home), a firm that works, among other products, with high performance materials including graphite composite used for jet fighter wings.
This material is like long-fiber carbon cloth tape impregnated with a thermosetting epoxy. Since we were unfamiliar with gluing this material, the good folks at FERRO agreed to cut the pieces and form the subassemblies and then attach them to make complete enclosures for us. It was a non-trivial commitment of time and money and far more than we as relative unknowns deserved, really.
At the time I was trying to interest Maryland Sound Industries (Maryland Sound Production & Event Production Company | Audio Production) in using our design for the touring concert sound systems they transport and set up for major performing artists. One of their most popular units in these setups was a combination of a box with 4 JBL pro sound woofers and a box on top of this with a large hornloaded tweeter. Knowing that they stored and used large numbers of this unit we really wanted to show them an alternative using the same drivers.
The resulting square-truncated rhombic dodecahedra were huge. Imagine a square baffle plate large enough to hold four ten or twelve inch woofers in a square array. This was back in the days when I foolishly thought that "size doesn't matter" so I did not realize the problem I was building into this incarnation of the design.
The enclosures, fully formed with precut baffle openings, were shipped to us and we transported them to the MSI headquarters, where their technicians inserted the woofers and electronic crossovers to run a simple test.
When they were finally energized it was, to put it mildly, a debacle. There was SO much air behind the woofers that they had no air spring at all to provide proper restoring force. They were too loose and actually buzzed loudly, humiliating us in front of the MSI personnel. Needless to say, no deal was forthcoming after that. It was a bitter lesson in the practical side of speaker design that I will never forget, and a badly-needed reminder that ALL designs have their practical limitations. The Hypercube is no exception.
Feel free to laugh; I make no excuses for this failure. It drove home to me the fact that the volume inside a loudspeaker enclosure is not a meaningless constant. The nature of the shape is such that it is hard to have too little volume....but it is always possible to have way too much. Fortunately, fitting the baffle approximately to the woofer in single-woofer designs usually avoids such problems.
Hi,
The idea that fretless instument strings are not damped by
fingers compared to instruments that have frets is utterly
ludicrous. But if you generally talk BS, its just more hot
air about things you generally remotely don't understand,
a habit once undertaken that is extremely hard to break.
rgds, sreten.
The idea that fretless instument strings are not damped by
fingers compared to instruments that have frets is utterly
ludicrous. But if you generally talk BS, its just more hot
air about things you generally remotely don't understand,
a habit once undertaken that is extremely hard to break.
rgds, sreten.
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I don't feel to laugh Tesserax thanks being honest posting interesting real world story from your working life and dreams, this is indeed interesting thread. Think i agree member Muddjester concerns but instrument or resonance interacting box for those wanting that also interesting reading.
Thanks BYRTT. I know I can sound like a know-it-all sometimes so I want people to know that while I may have stumbled upon a useful geometry, I am well aware that there are many people around the world who know a great deal more than me about audio design.
Hi,
If the story is true, then MSI had no real engineers and
probably just copied the done thing at the time. If so
they might have believed your claims, rather than
simply telling you it was practically ridiculous.
Why you didn't know its utterly impractical for PA
design is beyond me. No real engineers I suspect.
rgds, sreten.
If the story is true, then MSI had no real engineers and
probably just copied the done thing at the time. If so
they might have believed your claims, rather than
simply telling you it was practically ridiculous.
Why you didn't know its utterly impractical for PA
design is beyond me. No real engineers I suspect.
rgds, sreten.
Agreed, not laughing. I had no idea about this stuff until I read my first loudspeaker design book. But it sounds like.the failure was less about the enclosure material, and more about the enclosure size. I still think you could get some pre-cured carbon fiber sheets and construct an enclosure pretty easily.
Yes, I agree, Muddjester. I still believe it could be an excellent material to work with. Well, sreten, my degree was in Physics not engineering. I cannot claim to be any sort of engineer. Not that it is a good excuse. I agree, I should have known. Maybe MSI was happy to let me fail. They were not noobs like I was.
I think that this shape and volume may work very well for a pro stage monitor as it is compact and points up at 45deg. An 6.5in or 8in coaxial may work very well as a sealed or even a vented configuration. Who is to say you can't use this with a vent?
Interesting point xrk971. I am pretty sure they would make great stage monitors. With regard to venting, we had some anomalous experiences in that area that could make me sound wacky to the pros. Or more wacky than I already sound to many. I'd prefer not to present those experiences until I can explain what happened. However, I'm sure you can do some interesting prototyping there if you want to.
Hi,
The idea you can be good at physics and not be a good engineer
is way beyond me, as no good engineer can have poor physics.
(Engineers stop being engineers when they don't have the physics.)
Which suggests your intepretation of Physics is very dubious,
if you don't don't know how to use it, you don't really know it.
Which fits in with your nebulous interpretations of the enclosure.
rgds, sreten.
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"The difference between theory and practice is always bigger in practice than it is in theory."
last warning: another post discussing messengers instead of the message and this thread gets locked...that is a promise...- Status
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