Tom Danley said:
Is there anywhere I could hear them on the west coast?
I was all up in the rave scene in the 90s, and I saw some of your subs at "massives." Definitely saw a set at events thrown by USC in Seattle.
I'm 99% certain I heard a Unity at Club Ra in the Luxor hotel also.
Last November I went to Club Ra's replacement (LAX), and the Unities were gone 🙁
To make a long story short, outside of a few random sightings, I've barely heard a Unity.
Hi Patrick
I am not that up on where our stuff is, but there is a photo album with some installations here;
http://www.danleysoundlabs.com/forum/photos/photo-thumbnails.asp?albumid=1
In Lostwages, Nev, I know subs are in the Beatles tribute and the whole range in the “Chris Angel” show, some others but I don’t recall.
I know there are some “rich folks” that have powerful home theaters using the speakers out west. One fellow, Keith Yates who designs some of those systems (check out his stuff, wow is all I can say) has an out door cinema event every year in California.
http://www.danleysoundlabs.com/forum/photos/show-album.asp?albumid=2&photoid=65
The caption is wrong, those weren’t DTS-20’s but a box made for Keith that is much larger and in the first install he used them in, flat to below 10Hz.
Keith Yates designs (check out the Gallery)
http://www.keithyates.com/gallery.htm
Anyway, wish I knew “where” off the top of my head.
Patrick, keep at it, you are one of the minority who tries things.
Best,
Tom
I am not that up on where our stuff is, but there is a photo album with some installations here;
http://www.danleysoundlabs.com/forum/photos/photo-thumbnails.asp?albumid=1
In Lostwages, Nev, I know subs are in the Beatles tribute and the whole range in the “Chris Angel” show, some others but I don’t recall.
I know there are some “rich folks” that have powerful home theaters using the speakers out west. One fellow, Keith Yates who designs some of those systems (check out his stuff, wow is all I can say) has an out door cinema event every year in California.
http://www.danleysoundlabs.com/forum/photos/show-album.asp?albumid=2&photoid=65
The caption is wrong, those weren’t DTS-20’s but a box made for Keith that is much larger and in the first install he used them in, flat to below 10Hz.
Keith Yates designs (check out the Gallery)
http://www.keithyates.com/gallery.htm
Anyway, wish I knew “where” off the top of my head.
Patrick, keep at it, you are one of the minority who tries things.
Best,
Tom
gedlee said:
I agree - some of optimizations in the latter part of the Morgans thesis might produce Yagi-like radiation patterns - nominally within the specified coverage angle, but with sharp spikes outside the specified angle. We are left to wonder what the frequency response actually looks like towards the edges of the coverage pattern, or if the impulse response becomes degraded from diffraction artifacts.
What I found disappointing was the failure to check the theory with the real world - on pages 60 through 62, we see the results of a quite interesting 2-dimensional measurement system that was used to evaluate the fine structure of the wave coming out of two simple test horns. Unfortunately, the horns that emerged from the optimization routines in the latter part of the thesis do not appear to have been physically built and tested - comparing the real world against the theory would have demonstrated if the optimizations were valid or not. Perhaps I just overlooked it, or the graphics were not scanned with the rest of the paper.
There is also a minor quibble with the measurement apparatus itself - on page 54, we see a photo of the automated traverse system. If this photo represents what was actually used to measure the two test horns, reflections off the frame of the traverse would compromise the HF measurements - worse, the reflections would change as the traverse moves around, collecting data from the 3434 measurement points.
A refined version of the test apparatus, optimized for minimum diffraction, that displayed both impulse and and amplitude data might be quite interesting. I really need to dig up the early-Eighties AES paper that displays impulse data across a horizontal arc, showing a tsunami-like wavefront emerging from several different devices.
Optimisation techniques for horn loaded loudspeakers, Morgans et al, Chapters 1-4.
Optimisation techniques for horn loaded loudspeakers, Morgans et al, Chapter 5-8.
Optimisation techniques for horn loaded loudspeakers, Morgans et al, Bibliography and Appendices.
posted by rcw:
Mongo has thought about this...not much though...his head began to hurt so he stopped.
Would it be reasonable to conclude that a range of frequencies "leaves the wall" from different locations along the wall, dependent on frequency?
Would it be reasonable to conclude that the mouth is "better" terminated with a spiral curve, rather than one that is circular in section?
Tom, thanks for commenting. I can get aspirin for Mongo.
Mongo has thought about this...not much though...his head began to hurt so he stopped.
Would it be reasonable to conclude that a range of frequencies "leaves the wall" from different locations along the wall, dependent on frequency?
Would it be reasonable to conclude that the mouth is "better" terminated with a spiral curve, rather than one that is circular in section?
Tom, thanks for commenting. I can get aspirin for Mongo.
"What also happens is that at a certain frequency the real part of the impedance dominates and the imaginary part becomes very small, and at this point the wavefront can be said to "leave the wall", this is because the acoustic field has become predominantly a potential field that has no curvature. "
And the thing is I don't even understand this. "the acoustic field has become predominantly a potential field that has no curvature." If this is acoustics its nothing that I have ever studied.
And the thing is I don't even understand this. "the acoustic field has become predominantly a potential field that has no curvature." If this is acoustics its nothing that I have ever studied.
Tom
I'm sorry, but I just cannot agree with this statement.
"Think about the midrange drivers, at 1000Hz, there are eight entry holes (sources in the horn) and the horn dimension is about 2 3/4 inches across. With all 8 sources in phase and this dimension, there is no opportunity for them to produce hom’s.
"
I've said this before and I will need to see some data that has the resolution and features that I am looking for to judge if it has any merit. I expect this technique to produce HOMs. Its simply NOT the shape of the required waveform for a conical horn. The small dimensions relative to the wavelength will help, but they will still be generated. You simply cannot say that they won't.
I'm sorry, but I just cannot agree with this statement.
"Think about the midrange drivers, at 1000Hz, there are eight entry holes (sources in the horn) and the horn dimension is about 2 3/4 inches across. With all 8 sources in phase and this dimension, there is no opportunity for them to produce hom’s.
"
I've said this before and I will need to see some data that has the resolution and features that I am looking for to judge if it has any merit. I expect this technique to produce HOMs. Its simply NOT the shape of the required waveform for a conical horn. The small dimensions relative to the wavelength will help, but they will still be generated. You simply cannot say that they won't.
I am still curious as to the magnitude of HOMs compared to the main signal. If it's some 30~40 db down, then we would actually consider other aspects because this might not be dominating. But so far there seems no way of predicting or measuring it.
I understand that a simplifying assumption that is made for audio is that air has no viscosity and is incompressible, if you make this assumption then the acoustic field has no curl or divergence, i.e. it is a potential field that satisfies the Laplace equation.
One might well ask then how can the sound follow the wall of a diverging duct? because as a spherical wave the at small "kr" numbers the pressure is dominated by what Holland et al. in their AES paper call the "stretching" pressure, this allows the wavefront to follow a set of streamlines parallel to the duct wall as well as satisfy a set of equipotential surfaces orthogonal to them.
When the kr number becomes sufficient the non propagating stretching pressure falls to a very low value, but the radiating radial pressure remains and if the duct wall is still curving away at this point the radiating wavefront looses contact with the wall.
This does not happen in a conical horn, the wavefront following the wall all the way to the mouth.
I would not make the mistake that because this description of the physical process does not appear verbatim in any standard acoustic text book it is wrong, it is a conclusion that you can come to by looking at the basic physics, and it is correct.
rcw
One might well ask then how can the sound follow the wall of a diverging duct? because as a spherical wave the at small "kr" numbers the pressure is dominated by what Holland et al. in their AES paper call the "stretching" pressure, this allows the wavefront to follow a set of streamlines parallel to the duct wall as well as satisfy a set of equipotential surfaces orthogonal to them.
When the kr number becomes sufficient the non propagating stretching pressure falls to a very low value, but the radiating radial pressure remains and if the duct wall is still curving away at this point the radiating wavefront looses contact with the wall.
This does not happen in a conical horn, the wavefront following the wall all the way to the mouth.
I would not make the mistake that because this description of the physical process does not appear verbatim in any standard acoustic text book it is wrong, it is a conclusion that you can come to by looking at the basic physics, and it is correct.
rcw
Re: Re: Re: Re: Chapter 6
I don't quite understand "wavelengh of the energy" thing. The total energy for a wave front in the guide/horn should be pretty much constant. However, the energy distribution along a wave front should vary depending on shape of wave front.gedlee said:
Tom Danley said:
Look at Morgan's thesis paper referenced earlier in this thread:
Section 3.2.3 (page 54) describes the method.
Tom Danley said:
I remember. The Unity was being championed pretty heavily at Audio Asylum and in the Pi Speakers forum too. I don't recall if it was you or Mark Seaton, but I do remember the posts about the Unity. It seemed a little over the top to post response charts of a horn with a 10dB notch, saying it was better than everything else. That's what really started the thing between you and I.
I understood what you were trying to do then, just as I do now. I remember at that time thinking incoherent summing must have caused those 10dB on-axis nulls, and I think I said so. I thought perhaps if you skewed the crossover point or slope of a couple of the mids, staggering the null angles, it might have helped remove or reduce that notch. But I doubt I said that to you then.
I do know my four Pi had nice response through its 90x40 pattern, and so in my opinion, it was much better than the Unity was at the time. I am sure you've improved it since then. But in any case, they're for two different applications. My four Pi has nice response through its 90x40 coverage angle, and I'm very proud of it, as I am of all my designs.
I don't know if I ever told you, but I think I have. Regardless, I'll say again now. I think the Unity is a good idea for prosound, where arrayability is of utmost importance. Even if there are some slight anomalies within the pattern, it is definitely worthwhile to reduce the nasties outside the pattern. I think that's the Unity's strongest advantage, and I think it must be a good idea where that is concerned, just by looking at its geometry.
Tom Danley said:
I like Earl's horn very much too. I liked Charlie Hughes' quadratic horn for the same reasons, and I think Earl's goes one step beyond that. He has been meticulous in his studies, and found the OS/PS geometries to be improvements over pure conical, at least for drivers with plane wave radiation. I would still expect pure conical to be best for a driver with spherical radiation.
The only thing is I prefer an asymmetrical pattern for speakers with vertically stacked drivers, for all the reasons I've said in this thread. But an prolate spheroidal horn works just fine for that, and is one of the shapes Earl has mathematically verified just like the oblate spheroidal shape.
Tom Danley said:
I agree with you, but there are two sets of priorities. Each has its own set of difficulties. Many of the priorities are the same, but there are a few that aren't. For example, speakers used in large spaces need to be able to be used with other speakers, so performance in arrays is a priority. Home hifi speakers usually don't need to be arrayable, but directivity is still important because of its relationship to the reverberent field. Large areas need a lot of power and it has to be distributed as evenly as possible throughout the area. Small areas have potential modal problems, so while they don't necessarily need a lot of acoustic power, it does need to be put into the room in a way that averages room modes.
Tom Danley said:
I was in Chicago for several months in 2006/2007 doing a project for Lucent. Great project, by the way, working with some of the best minds of the former Bell Labs. Very interesting work, super guys. But that project was completed, and I don't have plans to return. It can always happen, I could be on a project there next year. But I don't have anything on the horizon that would put me there. I did try to contact you while I was there, as you recall.
As far as my skepticism, please keep in mind that my comments are more of a reaction to you and the way you've treated me than anything else. It all started with the Unity introduction in 2001, where you or Mark Seaton posted all over Audio Asylum and the Pi Speakers forum how much better the Unity was than any old two-way speaker like my four Pi (or now Geddes Summa for that matter). That Unity response chart with the 10dB notch was posted and it made it just plain weird that you guys would attack other speakers when your own speaker had such an obvious and glaring flaw.
Then it just seemed to run away with itself. I've tried to approach you with an olive branch both privately and publically and put this to rest, but so far, no luck. An example is your criticism of the 12Pi basshorn subwoofer. I took a lot of good ideas and put them together in what I think is a great product. The LAB12 woofers are perfect for this application and I saw that I could use a pair of them in push/pull, optimize the front and rear chamber volumes as best I could and conduct heat from the pole pieces to the access panels with conductive plugs to cool the motor cores. These were all useful optimizations, ones I would have expected you to recognize as being worthwhile.
I spent a lot of time modeling, measuring, testing, improving and optimizing the 12Pi basshorn subwoofer. It's not just some casual computer model put to plans, it's the result of several hundred man-hours of testing, refinement and optimization. I thought it was a good thing to position everything inside the box to make the cooling plug compatible with the LABhorn so existing owners could easily bolt one on, leveraging my work and making it useful for them. It was an olive branch, sort of like bringing my Ford to your Chevy track. But what did I get? A lot of critcism about the cooling plug and everything else, I mean, lots and lots of it. I was so frustrated with all the badgering, I eventually proposed a $1000 wager, remember?
I mean, tell Nick McKinney that you think the cooling plug idea is rubbish, see what he thinks. He's doing basically the same thing as my cooling plug in his woofers. My patent on the cooling plug should be just about ready to issue, by the way.
Anyway, there's little point going back over all this but I think you should understand that I'm not so much skeptical of your ideas as I have been skeptical about how you communicated them, particularly when you start comparing other ideas to them. It's natural to see your own ideas in their best light and competing ideas with less enthusiasm, but I think it's important to at least be fair.
This is especially true considering you're a respected authority. All the more reason to be responsible with the comments you make. I'm a hobbyist, after all, one that eventually put kits together for a small fee. But for me, it's always been about the love of music, and I've always offered the plans to my speakers for free, distributed under a GPL.
We're in two entirely different situations and shouldn't ever even have been at odds with one another, at least that's how I've always seen it. I never understood why you and some of your co-workers and supporters seemed to focus on me. Maybe you guys just mistook me for an easy target.
I've been having similar thoughts as rcw. Basically air flow only takes place when the pressure varies. The total energy relates with the total pressure which consists of dynamic pressure and static pressure. If the wave detaches from the wall, then the air at the wall is like a layer of static air where the total pressure is almost equal to the static pressure and the dynamic pressure is close to zero. I do wonder however, if the throat was designed so that the wave dettaches from the wall over a specific frequency range, what would the audible effects and what the performance of a wave guide would be like.
rcw said:
To assume that air is "incompressible" is absurd, no one does that in Acoustics. All acoustic fields have a divergence if they have finite sources. As such the Laplace Equation has no bearing on any acoustics problems. Hence any opinions that follow from such a bad assumption will be incorrect.
You description of the "physical process" is incorrect regardless of its lack of appearance in any text.
Well, there are many cases where people do make such assumptions to simplify math equations. If you don't see a density term in there...MartinQ said:
MartinQ said:
How could it be read any other way? For there to be no divergence and for Laplaces equation to apply the fluid would have to be incompressible. He is either making that assumption or his writting is so unclear that I have no idea what he is talking about.
gedlee said:
I would be interested in some waveguides for a car. If you ever decide to make and sell some how much would they be? How much would you need to sell to make it worth your time? Could maybe get others interested.
Bryce H. said:
Where are you going to mount them? Waveguides/horns for car that I have seen are all wide and very short and to be mounted under the dash.
These are very short and wide to mount under the dash. They require a DE500 driver - its very small. I would have to get at least $100 each with a minimum of six or its not really interesting enough for me. I'm not even sure where the mold is!?
Hi Wayne, Earl
Wayne, the mic array would not be a substitute for being able to measure what the horn is radiating from an acceptable anechoic distance.
Horns should be measured at a significant distance relative to their physical size and WL not at the mouth.
Fwiw, My introduction to you was when Mark S. forwarded a number of your highly inflammatory posts to me, my read was that you (Pi land) felt threatened by Nick’s DIY Unity horn effort, your posts claimed it couldn’t work and I spent many posts unsuccessfully try to explain to you how.
“I think the Unity is a good idea for pro-sound, where array ability is of utmost importance. Even if there are some slight anomalies within the pattern, it is definitely worthwhile to reduce the nasties outside the pattern.”
Is that just an empty Jab or do you mean “Nasties” relative to some actual speaker measured in similar detail?
“I liked Charlie Hughes' quadratic horn for the same reasons,”
Notice that the original Unity horn you had problems with had that basic profile and was introduced over a year and a half before.
Speaking of Charlie Hughes, he is a friend of mine; he is the one who took the 24KHz bw impulse , mag and phase response etc in the Synergy white paper.
“please keep in mind that my comments are more of a reaction to you and the way you've treated me than anything else. It all started with the Unity introduction in 2001, where you or Mark Seaton posted all over Audio Asylum and the Pi Speakers forum how much better the Unity was than any old two-way speaker like my four Pi (or now Geddes Summa for that matter).”
Nick was offering a Unity horn for DIY use (I do like DIY) but that effort and Nick wasn’t part of the company, I became involved directly and in response to your bashing and criticism of the general idea. You argued that it wasn’t important for the time to be correct, for the hf drivers to be behind the LF driver, they couldn’t sum into one source (which based on your imaginary null remarks here are still stuck on) and so on .
“it made it just plain weird that you guys would attack other speakers when your own speaker had such an obvious and glaring flaw.”
Wayne, not that repetition has any effect but listen, We / I didn’t make or sell the DIY version (although I did find and fix the notch) and boy if that isn’t the pot calling the Kettle Black, you initiated this hostility and just what do you mean by “attacking other speakers”. I don’t recall anyone EVER bashing let alone talking about your speakers (other than you bringing them up and even then not bashing)?
You on the other hand have a problem with stuff I do it seems. Even now you still focus on your imaginary nulls (in this very thread) and a notch in a speaker many years ago, that I didn’t even sell. Fwiw, one narrow notch like that old unit had so far as being audible, isn’t “glaring” either as you chose to put it and isn’t present at all, other than at 4Khz and exactly on axis, only in the DIY version.
Funny you bring up the Lab sub too, “back then” you were a critic of the approach and using that un-customary kind of massive /strong (servodrive like) driver that I specified.
I was I admit I was a little miffed when what a year and some later you show up on Live Audio Board Forum promoting your 12pi using the same driver and basic alignment (now the approach was ok I guess) , hyping it as having “solved” the problems of the Lab sub, all by simply ignoring the basic size constraint the group placed on it and by using your undiscovered “distortion reduction miracle” of push pull drivers and of course your rear plug.
Criticism of your plug was actually skepticism of your wild claims, you can’t double the usable power handling by making the center pole a little cooler, it is the coil that needs to be cooled most and when I suggested you try that proven route you weren’t interested.
You mention some wager like I should remember or be interested, please think of what these words mean.
I donated that design to the Live Audio Board for fun years and years ago, I never received a penny from it.
I did it when they started talking about a group project for W bins and I suggested a more modern horn could be made and based on the software I had from designing the Servodrive horns, I thought it could be done relatively easily.
They specified the specific size and low cutoff.
Is it the best I could do the highest output possible?, no, but it had to be good enough to beat essentially all the Pro-sound subs of the day which it did and that was my goal in that “give away” design.
You posture, challenging the Lab sub, riding its coat tails, repeatedly posting / promoting your 12pi and “huge performance gains” on that LAB sub forum (with out ever even building a lab to actually compare to) was very nervy at least and truly ironic in light of history, so you might be able to imagine why I wasn’t jumping on your bandwagon.
Frankly, in this thread there are smatterings of what sounds like you still being evasive and trying to ride Earls coat tails, for instance directly likening your design to his.
“I never understood why you and some of your co-workers and supporters seemed to focus on me. Maybe you guys just mistook me for an easy target.”
“Easy Target”, that is about the last thing I would describe you as, more like evasive, often ending on personal attack and often like here adopting the Jesse Jackson “poor me victim” posture.
I have seen a history of you editing and removing posts, posting attacks under other names on yours and other forums, like happened on PSW last December when the moderator said prove you were not those other people (all with the same ip as yours) and you couldn’t do it.
Our past discussions have often reminded me of trying to trap a pool of mercury under ones thumb, you change your arguments and direction on the fly and revise what you claimed you were supposedly were saying after the fact by editing and pulling posts.
You keep implying I / we / they were attacking you / your Pi speakers, just what the heck are you talking about.
Where did your speakers EVER come up, unless you brought them up and speak up, now that your accusing me, co-workers and “supporters”, exactly who was attacking you when you didn’t provoke it?
I don't see we have much more to say to each other do you?
Hi Earl
“I'm sorry, but I just cannot agree with this statement.
"Think about the midrange drivers, at 1000Hz, there are eight entry holes (sources in the horn) and the horn dimension is about 2 3/4 inches across. With all 8 sources in phase and this dimension, there is no opportunity for them to produce hom’s.
"
I've said this before and I will need to see some data that has the resolution and features that I am looking for to judge if it has any merit. I expect this technique to produce HOMs. Its simply NOT the shape of the required waveform for a conical horn. The small dimensions relative to the wavelength will help, but they will still be generated. You simply cannot say that they won't.”
I have not measured on the turntable with pink noise yet but will be doing that soon.
To get a handle on this part specifically, I will probably also try disconnecting the Low and high sections to see what can be seen from the mid ranges alone as well.
My thought argument (lacking specific measurements for now) is that if one places 8 woofers close together, in a space less than ¼ wl across, that there is no mechanism I see to produce anything but an omni radiation pattern. The source is not large enough to produce directionality and the phase distribution can’t produce nulls or lobes..
The principal issue here appears to me to be a question of “acoustic size” not if it is a woofer, midrange or tweeter etc.
I think there may be two issues too, one is where mathematical “Zero” or extinction point is and at what magnitude is an effect detectable / measurable relative to normal operation.
Given you are vastly more qualified to look at this math, I would ask you a specific math question?
If one had a large straight conical horn, lets say 50 degrees angle and that horn had a 3 inch throat which was driven by a text book plane wave, at about what frequency could this begin to produce HOM’s?
My guess would be that with a 3 inch throat dimension, a plane wave origin and 50 degree angle, that one couldn’t produce any significant HOM’s until the frequency was over about 1500Hz and likely more like an octave higher.
My guess would be that 8 acoustically small “in phase” sources, regardless of being bass, mid or hf, if placed in a group less than 1 /4 wl across would not radiate a complex pattern if placed within a horn of that throat dimension, or at least I have never observed anything like that.
Anyway, in the next couple weeks I have to drag a ton of other stuff out for a couple days of measurements and I’ll do the pink noise test you asked about then.
On a different subject, I have a large scale industrial acoustic idea and I am about as far as I can go short of building and testing a known case.
I was strongly encouraged by Dr. Patronis’s (after a day and a half of pondering) to try it though and “if” it works could be a very big thing and could then use much more help. The problem I have is that I can picture it working well enough and have several first shot design approaches but it is not something I am very confident about.
Before I go to the significant trouble time and expense to build a first guess prototype, I would like to see about having you take a basic theoretical look at it.
If you’re available and interested (and I promise THIS IS a TRULY weird acoustic idea), please e-mail me..
Best,
Tom Danley
Wayne, the mic array would not be a substitute for being able to measure what the horn is radiating from an acceptable anechoic distance.
Horns should be measured at a significant distance relative to their physical size and WL not at the mouth.
Fwiw, My introduction to you was when Mark S. forwarded a number of your highly inflammatory posts to me, my read was that you (Pi land) felt threatened by Nick’s DIY Unity horn effort, your posts claimed it couldn’t work and I spent many posts unsuccessfully try to explain to you how.
“I think the Unity is a good idea for pro-sound, where array ability is of utmost importance. Even if there are some slight anomalies within the pattern, it is definitely worthwhile to reduce the nasties outside the pattern.”
Is that just an empty Jab or do you mean “Nasties” relative to some actual speaker measured in similar detail?
“I liked Charlie Hughes' quadratic horn for the same reasons,”
Notice that the original Unity horn you had problems with had that basic profile and was introduced over a year and a half before.
Speaking of Charlie Hughes, he is a friend of mine; he is the one who took the 24KHz bw impulse , mag and phase response etc in the Synergy white paper.
“please keep in mind that my comments are more of a reaction to you and the way you've treated me than anything else. It all started with the Unity introduction in 2001, where you or Mark Seaton posted all over Audio Asylum and the Pi Speakers forum how much better the Unity was than any old two-way speaker like my four Pi (or now Geddes Summa for that matter).”
Nick was offering a Unity horn for DIY use (I do like DIY) but that effort and Nick wasn’t part of the company, I became involved directly and in response to your bashing and criticism of the general idea. You argued that it wasn’t important for the time to be correct, for the hf drivers to be behind the LF driver, they couldn’t sum into one source (which based on your imaginary null remarks here are still stuck on) and so on .
“it made it just plain weird that you guys would attack other speakers when your own speaker had such an obvious and glaring flaw.”
Wayne, not that repetition has any effect but listen, We / I didn’t make or sell the DIY version (although I did find and fix the notch) and boy if that isn’t the pot calling the Kettle Black, you initiated this hostility and just what do you mean by “attacking other speakers”. I don’t recall anyone EVER bashing let alone talking about your speakers (other than you bringing them up and even then not bashing)?
You on the other hand have a problem with stuff I do it seems. Even now you still focus on your imaginary nulls (in this very thread) and a notch in a speaker many years ago, that I didn’t even sell. Fwiw, one narrow notch like that old unit had so far as being audible, isn’t “glaring” either as you chose to put it and isn’t present at all, other than at 4Khz and exactly on axis, only in the DIY version.
Funny you bring up the Lab sub too, “back then” you were a critic of the approach and using that un-customary kind of massive /strong (servodrive like) driver that I specified.
I was I admit I was a little miffed when what a year and some later you show up on Live Audio Board Forum promoting your 12pi using the same driver and basic alignment (now the approach was ok I guess) , hyping it as having “solved” the problems of the Lab sub, all by simply ignoring the basic size constraint the group placed on it and by using your undiscovered “distortion reduction miracle” of push pull drivers and of course your rear plug.
Criticism of your plug was actually skepticism of your wild claims, you can’t double the usable power handling by making the center pole a little cooler, it is the coil that needs to be cooled most and when I suggested you try that proven route you weren’t interested.
You mention some wager like I should remember or be interested, please think of what these words mean.
I donated that design to the Live Audio Board for fun years and years ago, I never received a penny from it.
I did it when they started talking about a group project for W bins and I suggested a more modern horn could be made and based on the software I had from designing the Servodrive horns, I thought it could be done relatively easily.
They specified the specific size and low cutoff.
Is it the best I could do the highest output possible?, no, but it had to be good enough to beat essentially all the Pro-sound subs of the day which it did and that was my goal in that “give away” design.
You posture, challenging the Lab sub, riding its coat tails, repeatedly posting / promoting your 12pi and “huge performance gains” on that LAB sub forum (with out ever even building a lab to actually compare to) was very nervy at least and truly ironic in light of history, so you might be able to imagine why I wasn’t jumping on your bandwagon.
Frankly, in this thread there are smatterings of what sounds like you still being evasive and trying to ride Earls coat tails, for instance directly likening your design to his.
“I never understood why you and some of your co-workers and supporters seemed to focus on me. Maybe you guys just mistook me for an easy target.”
“Easy Target”, that is about the last thing I would describe you as, more like evasive, often ending on personal attack and often like here adopting the Jesse Jackson “poor me victim” posture.
I have seen a history of you editing and removing posts, posting attacks under other names on yours and other forums, like happened on PSW last December when the moderator said prove you were not those other people (all with the same ip as yours) and you couldn’t do it.
Our past discussions have often reminded me of trying to trap a pool of mercury under ones thumb, you change your arguments and direction on the fly and revise what you claimed you were supposedly were saying after the fact by editing and pulling posts.
You keep implying I / we / they were attacking you / your Pi speakers, just what the heck are you talking about.
Where did your speakers EVER come up, unless you brought them up and speak up, now that your accusing me, co-workers and “supporters”, exactly who was attacking you when you didn’t provoke it?
I don't see we have much more to say to each other do you?
Hi Earl
“I'm sorry, but I just cannot agree with this statement.
"Think about the midrange drivers, at 1000Hz, there are eight entry holes (sources in the horn) and the horn dimension is about 2 3/4 inches across. With all 8 sources in phase and this dimension, there is no opportunity for them to produce hom’s.
"
I've said this before and I will need to see some data that has the resolution and features that I am looking for to judge if it has any merit. I expect this technique to produce HOMs. Its simply NOT the shape of the required waveform for a conical horn. The small dimensions relative to the wavelength will help, but they will still be generated. You simply cannot say that they won't.”
I have not measured on the turntable with pink noise yet but will be doing that soon.
To get a handle on this part specifically, I will probably also try disconnecting the Low and high sections to see what can be seen from the mid ranges alone as well.
My thought argument (lacking specific measurements for now) is that if one places 8 woofers close together, in a space less than ¼ wl across, that there is no mechanism I see to produce anything but an omni radiation pattern. The source is not large enough to produce directionality and the phase distribution can’t produce nulls or lobes..
The principal issue here appears to me to be a question of “acoustic size” not if it is a woofer, midrange or tweeter etc.
I think there may be two issues too, one is where mathematical “Zero” or extinction point is and at what magnitude is an effect detectable / measurable relative to normal operation.
Given you are vastly more qualified to look at this math, I would ask you a specific math question?
If one had a large straight conical horn, lets say 50 degrees angle and that horn had a 3 inch throat which was driven by a text book plane wave, at about what frequency could this begin to produce HOM’s?
My guess would be that with a 3 inch throat dimension, a plane wave origin and 50 degree angle, that one couldn’t produce any significant HOM’s until the frequency was over about 1500Hz and likely more like an octave higher.
My guess would be that 8 acoustically small “in phase” sources, regardless of being bass, mid or hf, if placed in a group less than 1 /4 wl across would not radiate a complex pattern if placed within a horn of that throat dimension, or at least I have never observed anything like that.
Anyway, in the next couple weeks I have to drag a ton of other stuff out for a couple days of measurements and I’ll do the pink noise test you asked about then.
On a different subject, I have a large scale industrial acoustic idea and I am about as far as I can go short of building and testing a known case.
I was strongly encouraged by Dr. Patronis’s (after a day and a half of pondering) to try it though and “if” it works could be a very big thing and could then use much more help. The problem I have is that I can picture it working well enough and have several first shot design approaches but it is not something I am very confident about.
Before I go to the significant trouble time and expense to build a first guess prototype, I would like to see about having you take a basic theoretical look at it.
If you’re available and interested (and I promise THIS IS a TRULY weird acoustic idea), please e-mail me..
Best,
Tom Danley
I have an acoustics text book by Rienstra and Hirschberg that states that acoustics is a first order approximation that assumes the wave equation is linear and that changes in density in the type of acoustic fields we encounter in audio are so small that they can be neglected so that we can assume that divergence is zero.
In his analysis of Websters horn equation in his AES paper Putland also assumes an inviscid and incompressible fluid.
I would also point out that a one parameter spherical wavefront, (what we are trying to get), is an equiphase shell in a radially symmetrical potential field around a pulsating point source.
rcw
In his analysis of Websters horn equation in his AES paper Putland also assumes an inviscid and incompressible fluid.
I would also point out that a one parameter spherical wavefront, (what we are trying to get), is an equiphase shell in a radially symmetrical potential field around a pulsating point source.
rcw