Re: more subtleties of line arrays
Something didn't quite seem right about this statement.
Here is a plot of the comparison of open & closed pipes 23.5" long, 4" diameter (using TB W3-871S since we didn't have the Sammi data). Note that the line has no damping to better show off the harmonics the line produces. As well the pipe is not necessarily optimum in either configuartion, particularily the open (quarter wave) situation -- the purpose is to see where the harmonics fall.
You can see in the case of the closed line we have twice as many resonances in the line as in the open case (ignore that the open case it is larger -- as can be seen be the deviation from the blue line it is far from optimum). So while it is true that the closed tube only resonants on the even harmonics, becasue it is half-wave there are twice as many. You can also see that the primamry resonance in the closed pipe causes the 1st null, and in the quarter wave pipe the bottom peak. Further the dip at just over 500 Hz is going to be a lot easier to damp than the one an octave lower.
I'm thinking that an appropriate size hole(s) drilled in the back cap of the pipe might have some real positive benefits and allow more progressive stuffing... At the density used it is going to be somewhat reflective at higher frequencies causing some time smear.
dave
Zarathu said:
Something didn't quite seem right about this statement.
Here is a plot of the comparison of open & closed pipes 23.5" long, 4" diameter (using TB W3-871S since we didn't have the Sammi data). Note that the line has no damping to better show off the harmonics the line produces. As well the pipe is not necessarily optimum in either configuartion, particularily the open (quarter wave) situation -- the purpose is to see where the harmonics fall.
You can see in the case of the closed line we have twice as many resonances in the line as in the open case (ignore that the open case it is larger -- as can be seen be the deviation from the blue line it is far from optimum). So while it is true that the closed tube only resonants on the even harmonics, becasue it is half-wave there are twice as many. You can also see that the primamry resonance in the closed pipe causes the 1st null, and in the quarter wave pipe the bottom peak. Further the dip at just over 500 Hz is going to be a lot easier to damp than the one an octave lower.
I'm thinking that an appropriate size hole(s) drilled in the back cap of the pipe might have some real positive benefits and allow more progressive stuffing... At the density used it is going to be somewhat reflective at higher frequencies causing some time smear.
dave
Attachments
How big a hole?
I think I understand your diagram. But if the even harmonics are just greater or doubled, it doesn't change my reasoning that evens introduce clarity(which in too much sounds like screeching) which, again in my reasoning, would augment the clarity of the speaker as a whole.
Since I've experienced this with the tubes, perhaps you could suggest another scenario if this one doesn't work for you.
Actually I have it wrong, its the odd ordered harmonics that are produced in a closed tube. I can never remember this for some reason.
Zarathu
I think I understand your diagram. But if the even harmonics are just greater or doubled, it doesn't change my reasoning that evens introduce clarity(which in too much sounds like screeching) which, again in my reasoning, would augment the clarity of the speaker as a whole.
Since I've experienced this with the tubes, perhaps you could suggest another scenario if this one doesn't work for you.
Actually I have it wrong, its the odd ordered harmonics that are produced in a closed tube. I can never remember this for some reason.
Zarathu
No, you had it right first time. A closed line produces even-order standing waves, while an open-ended line produces odd-order.
I'm not sure I quite follow the reasoning that even-order harmonics introduce clarity though. Assuming that the harmonics (which we surely don't want in the first place) are supressed by proper driver placement in the line and judicious damping, it shouldn't make much difference if they're positive or negative. FWIW, I've never experienced it myself at any rate, though as ever, YMMV.
I'm not sure I quite follow the reasoning that even-order harmonics introduce clarity though. Assuming that the harmonics (which we surely don't want in the first place) are supressed by proper driver placement in the line and judicious damping, it shouldn't make much difference if they're positive or negative. FWIW, I've never experienced it myself at any rate, though as ever, YMMV.
maybe its not a big deal
Which ever it is.......I'm learning disabled on this little point.
The assumption comes from how either of the two sound when deliberately produced by amplifiers and played in speakers.
Tube amps when driven into clipping produce more of one which is described as soft, warm and full, but at the same time a bit muddy. Solid State when driven into clipping produces the other, and its often described as shrill, and screechy, but at the same time not muddy but extreme clarifying(too much of either is obviously detrimental to good listening). And, I have done my darnest to make sure that very little of either gets back into the back of the speaker.
My PVC tubes are intense filled with very dense fiberglass insulation, and because I am using arrays, each speaker is only caring 5.8% of the total that a single midrange would carry, reducing the distortion way down. So not a lot of sound gets back through the speaker after having to traverse 47 inches of 4 lb/cu in + dense packed fiberglass insulation.
Its just perfectionism at work. But nobody knows how much this effect might be.
Zarathu
Which ever it is.......I'm learning disabled on this little point.
The assumption comes from how either of the two sound when deliberately produced by amplifiers and played in speakers.
Tube amps when driven into clipping produce more of one which is described as soft, warm and full, but at the same time a bit muddy. Solid State when driven into clipping produces the other, and its often described as shrill, and screechy, but at the same time not muddy but extreme clarifying(too much of either is obviously detrimental to good listening). And, I have done my darnest to make sure that very little of either gets back into the back of the speaker.
My PVC tubes are intense filled with very dense fiberglass insulation, and because I am using arrays, each speaker is only caring 5.8% of the total that a single midrange would carry, reducing the distortion way down. So not a lot of sound gets back through the speaker after having to traverse 47 inches of 4 lb/cu in + dense packed fiberglass insulation.
Its just perfectionism at work. But nobody knows how much this effect might be.
Zarathu
Re: maybe its not a big deal
Do keep in mind that due to the density of your stuff -- assumming it is uniform, the highest frequencies are going to see it as solidand bounce back much sooner,
If you can give us the parameters of the Sammis it would be possible to see if the existing tubes could be turned into ML-TLs that work... without that info any suggesttion as to what size holes in the end would be SWAG.
dave
Zarathu said:
Do keep in mind that due to the density of your stuff -- assumming it is uniform, the highest frequencies are going to see it as solidand bounce back much sooner,
If you can give us the parameters of the Sammis it would be possible to see if the existing tubes could be turned into ML-TLs that work... without that info any suggesttion as to what size holes in the end would be SWAG.
dave
MJL,
I don't see how you get the effect of an individual stuffed pipe for every speaker by putting them in a box with all the other speakers.
Unless you are thinking of something I'm not seeing.
Zarathu
I don't see how you get the effect of an individual stuffed pipe for every speaker by putting them in a box with all the other speakers.
Unless you are thinking of something I'm not seeing.
Zarathu
"Do keep in mind that due to the density of your stuff -- assumming it is uniform, the highest frequencies are going to see it as solidand bounce back much sooner,"
What frequencies consist of "the highest frequencies"
Zarathu
What frequencies consist of "the highest frequencies"
Zarathu
1MGHZ + 🙄
I still don't understand at all what your "tubes" are supposed to do ...
what was YOUR plan/math for the tubes ??
and why not OB/dipole ?
I still don't understand at all what your "tubes" are supposed to do ...
what was YOUR plan/math for the tubes ??
and why not OB/dipole ?
Jin,
I already explained the tubes. If you want more information, email me. Or Go to PE forum:
http://www.pesupport.com/cgi-bin/config.pl?read=349242
Where i spent 90 minutes writing out an explanation for someone else.
Zarathu
I already explained the tubes. If you want more information, email me. Or Go to PE forum:
http://www.pesupport.com/cgi-bin/config.pl?read=349242
Where i spent 90 minutes writing out an explanation for someone else.
Zarathu
Actually, they are TLs. They entirely supress and damp the rear wave of the driver, and will present an ~flat impedence curve to the amplifier. By definition, that's a TL. I don't think Dave was suggesting turning them into MLTLs for you though -he's just interested in the drivers, and other ways they can work.
With 4lbs ft^3 of stuffing, the tubes will be doing very little as that back wave will be completely eaten -that's the heaviest damping I've ever heard of. The highest I've ever used, for a completely aperiodic TL was 0.75lbs ft. As Dave pointed out, in general terms, you have to be very careful at very high densities as the material will be near solid, and behave like one.
I see what you mean about the harmonics now -you're talking about predominantly 2nd harmonic & 3rd harmonic distortion, right? The latter can make an amp sound subjectively sharp. That said, if the harmonics are supressed in the first place, I can't see there being any differences. No harm it it of course. I think you've got a very creative set of speakers there. Very nice job indeed.
I fluctuate with arrays from loving them to cursing them -I can hear the spectacular benefits they can bring, such as their more linear wavefront & I like them. Problem is, like Dave, I find some of the downsides bug me a bit too, like the necessity of having a crossover slap-bang in the most critical hearing region (not that they're alone in that of course). We all value different things. My personal favourites are horns and dipoles. Give me an Altec VOTT or similar and I'm in heaven. 😉 Not everyone's cup of tea of course, and I wouldn't pretend they are.
With 4lbs ft^3 of stuffing, the tubes will be doing very little as that back wave will be completely eaten -that's the heaviest damping I've ever heard of. The highest I've ever used, for a completely aperiodic TL was 0.75lbs ft. As Dave pointed out, in general terms, you have to be very careful at very high densities as the material will be near solid, and behave like one.
I see what you mean about the harmonics now -you're talking about predominantly 2nd harmonic & 3rd harmonic distortion, right? The latter can make an amp sound subjectively sharp. That said, if the harmonics are supressed in the first place, I can't see there being any differences. No harm it it of course. I think you've got a very creative set of speakers there. Very nice job indeed.
I fluctuate with arrays from loving them to cursing them -I can hear the spectacular benefits they can bring, such as their more linear wavefront & I like them. Problem is, like Dave, I find some of the downsides bug me a bit too, like the necessity of having a crossover slap-bang in the most critical hearing region (not that they're alone in that of course). We all value different things. My personal favourites are horns and dipoles. Give me an Altec VOTT or similar and I'm in heaven. 😉 Not everyone's cup of tea of course, and I wouldn't pretend they are.
Thanks, Scott Moose.
I really had to think out of the box in order to build them. And I had to do research covering every area of the design, sometimes extrapolating the research a bit to hit what I wanted.
People often don't see it.
Most line arrays are not using my design. I deliberately avoided as much of the extreme human sensitivity for the cross as possible, in that I crossed at 165 and 2650. Almost all line arrays that do cross at all cross at around 1200 - 1600. Plus i use electronic crossovers so there isn't that huge impedance kick right at the crossover. The amps drive the speakers directly and the only impedance variances are those of the speaker itself, not a passive crossover. Additionally, the damping factor is whatever the amps are capable of, so they have electrical control over the speakers, something that is impossible in passive crossovers.
My version REQUIRES electronic crossovers and Tri-amping. It will be a pale shadow of itself otherwise.
As to the 4 lb/cu ft, Vance Dickason in his 6th Edition of the Loudspeaker Cookbook starting on page 35, discusses empirical study of box stuffing materials, and concluded that that density of fiberglass was the best for attenuation of the sound. According to his graphs, the high absorption ranges is between 150 to 5000, gradually rising 100db to 110db to about 4500hz, and then falling to 103 at 5000, and dropping like a rock after that.
Obviously I am completely in the range for complete absorption.
Zarathu
I really had to think out of the box in order to build them. And I had to do research covering every area of the design, sometimes extrapolating the research a bit to hit what I wanted.
People often don't see it.
Most line arrays are not using my design. I deliberately avoided as much of the extreme human sensitivity for the cross as possible, in that I crossed at 165 and 2650. Almost all line arrays that do cross at all cross at around 1200 - 1600. Plus i use electronic crossovers so there isn't that huge impedance kick right at the crossover. The amps drive the speakers directly and the only impedance variances are those of the speaker itself, not a passive crossover. Additionally, the damping factor is whatever the amps are capable of, so they have electrical control over the speakers, something that is impossible in passive crossovers.
My version REQUIRES electronic crossovers and Tri-amping. It will be a pale shadow of itself otherwise.
As to the 4 lb/cu ft, Vance Dickason in his 6th Edition of the Loudspeaker Cookbook starting on page 35, discusses empirical study of box stuffing materials, and concluded that that density of fiberglass was the best for attenuation of the sound. According to his graphs, the high absorption ranges is between 150 to 5000, gradually rising 100db to 110db to about 4500hz, and then falling to 103 at 5000, and dropping like a rock after that.
Obviously I am completely in the range for complete absorption.
Zarathu
Scottmoose said:
This would make sense if it was 2nd or 3rd harmonic distortion that was being caused by the natural pipe resonances. A good no feedback SE amp produces primamry 2nd order distrortion which the ear/brain is quite tolerant of. 3rd order as long as it is not at a higher level then the 3rd is not bad... higher harmonics get obnoxious pretty quick.
But in the pipes we are talking about time-delayed sound that is at the same frequency as has generated it, and rotates phase such as to cause FR ripple. It is always best to start with as low a level as possible from the line geometry 1st and then use as little damping as possible. It is also always a good idea to make it progressive -- very desnse at the far end and non-existant behind the driver (except maybe for a ring of natural felt on the walls to kill 1st reflections.
If you can post the Sammi's T/S parameters we can do a virtual experiment on how much damping is actually needed to make the box look sealed wrt FR (ie all the ripple (and therefore the rear emergy is absorbed as intended)
dave
Zarathu said:
In my opinion that is pretty much the case with all multi-way speakers. Crossovers tend towards evil, and passive ones can be real evil.
For the price of some of premium components used in some of the complex XOs i see, you could make a couple extra amps.
dave
NOPE....Don't want to know
I'm not posting the Sammi T/S data because I'm not taking them apart to change the stuffing ratio. Its way too much a pain to do that. It took me ten long hours to measure, weigh and put the stuffing in, in the first place. I'm notinterested in knowing what your simulation says. It would make me want to change it.
If I make another one some time, or I should go commercial, then I will, but we are still looking at your simulations. No offense to you or Martin King, but I have Vance Dickason's empirical data used with sealed boxes to go on, in regards to the frequencies absorbed and at what densities and at what decibel attenuation.
Zarathu
I'm not posting the Sammi T/S data because I'm not taking them apart to change the stuffing ratio. Its way too much a pain to do that. It took me ten long hours to measure, weigh and put the stuffing in, in the first place. I'm notinterested in knowing what your simulation says. It would make me want to change it.
If I make another one some time, or I should go commercial, then I will, but we are still looking at your simulations. No offense to you or Martin King, but I have Vance Dickason's empirical data used with sealed boxes to go on, in regards to the frequencies absorbed and at what densities and at what decibel attenuation.
Zarathu
Be that as it may, when you decide to go with simulations over empirical data(empirical data is required to make simulations), then that is where we part company.
I'll take empirical data, the source of simulations, over simulations that are mathematical extrapolations of actual data.
Sorry. I guess I'm more of a data guy than a simulation guy. Simulations do not cover all the available data, only what has been included from the original empirical data. WINisD is a great simulation program, but many times its just plain wrong.
You can't change my opinion on this.
And I don't share your incredible acceptance of King, partly because of my views of simulations, partly because he's the only one who is providing it since he won't allow anyone else to replicate it(since its now too expensive for me to buy for just one or two projects, and it wouldn't help me anyhow since i had the free one before and couldn't figure that one out either), and partly because I myself am not able to figure out his spread sheets despite several months of trying and have to rely on others who may or may not be able to accurately use them, and finally because I'm not even sure that TL's are appropriate for what I'm doing with my midranges anyhow, since I'M CROSSING quite a bit above any real bass.
Dave and perhaps you too are really into TL's. I'm not. I looked into them and decided not to use them. I'm not changing my frame of reference after I'm done; that would be just plain dumb.
Finally, and this is not a real bearing on what I use, I've had some rather disagreeable arrogant cross communications with King, that left a bad taste in my mouth for interacting with him, and thus with his work. I'm sure he gives even less than a whale crap at the bottom of the ocean about that and probably doesn't even have a clue who I might be, but it unfortunately colors my views on his work. Using his work after that makes me just plain uncomfortable.
Sorry. End of discussion.
I'll take empirical data, the source of simulations, over simulations that are mathematical extrapolations of actual data.
Sorry. I guess I'm more of a data guy than a simulation guy. Simulations do not cover all the available data, only what has been included from the original empirical data. WINisD is a great simulation program, but many times its just plain wrong.
You can't change my opinion on this.
And I don't share your incredible acceptance of King, partly because of my views of simulations, partly because he's the only one who is providing it since he won't allow anyone else to replicate it(since its now too expensive for me to buy for just one or two projects, and it wouldn't help me anyhow since i had the free one before and couldn't figure that one out either), and partly because I myself am not able to figure out his spread sheets despite several months of trying and have to rely on others who may or may not be able to accurately use them, and finally because I'm not even sure that TL's are appropriate for what I'm doing with my midranges anyhow, since I'M CROSSING quite a bit above any real bass.
Dave and perhaps you too are really into TL's. I'm not. I looked into them and decided not to use them. I'm not changing my frame of reference after I'm done; that would be just plain dumb.
Finally, and this is not a real bearing on what I use, I've had some rather disagreeable arrogant cross communications with King, that left a bad taste in my mouth for interacting with him, and thus with his work. I'm sure he gives even less than a whale crap at the bottom of the ocean about that and probably doesn't even have a clue who I might be, but it unfortunately colors my views on his work. Using his work after that makes me just plain uncomfortable.
Sorry. End of discussion.
Every speaker I've ever modelled on winISD and then gone on to build and measure groundplane has measured excellent to the simulation. All have been sealed boxes though. I'd imagine ported stuff has a bigger margin for error.
Rob.
fwiw I'd trust Dave and many others on this forum for their experiences. Dickinsons book is good (I own it) but only covers the very basics. (hence the 'cookbook')
Rob.
Rob.
fwiw I'd trust Dave and many others on this forum for their experiences. Dickinsons book is good (I own it) but only covers the very basics. (hence the 'cookbook')
Rob.
Zarathu said:
Who said anything about just going with simulations? Or are you just making an assumption ?
Dave has around 30 years worth of practical experience, designing, building and measuring inumerable speakers. Whilst I can't exactly match that, I've been doing this for a while myself too. Do you honestly believe that either of us (or anyone else here) view simulations as an end in themselves? If you do, you are seriously mistaken. Simulations are just that: simulations. They can help you refine a design without wasting time, money and effort. As Rob points out, WinISD can be very accurate indeed for some cabinets. Software does not, or should not, design a speaker for you -a common and erroneous assumption. That's where knowledge comes in -knowing basic principles of enclosure design & the room's effect, what software will help you with, & also what it's limitations are etc. If you lack the basic knowledge, it'll go wrong. I you have it, it's another very useful tool.
My acceptance of Martin King's models and math comes from the fact that I've compared their predicted responses innumerable times to physical measurements, both of my designs, back-engineered designs, and other instances too, the measurements coming from a variety of sources. Their accuracy within their extremely broad remit is proven, and they are accepted as such by designers such as George Augsperger, Peter Comeau, Tom Danley, Greg Monfort etc., to name but four. They can't do everything, and don't pretend to, as noted above, but they are one of the most powerful tools available for modelling an enclosure design. You do know that the math used has a basis in physical measurements (your favourite 'empirical data')? I might add that Martin also happens to be a friend of mine, and has done a massive amount for the DIY community.
Considering the fact that I stated above that my personal favourite speakers are horns and dipoles, I'm not sure where you get the notion that I'm 'really into TLs'. I like them, design quite a few (for other people's benefit 99.99% of the time, as I like to help when I can -it makes the world a nicer place. Dave does the same -he hosts the TL speaker site and Frugal horn site, for no personal gain), and know a reasonable amount about them. Nobody is trying to change your point of reference -simply trying to offer comments. For example, both Dave & I have pointed out that your midrange enclosure
Scott