Patrick Bateman said:
Delete the paradigms, turn out the lights and they'll think that they are at a concert.
Actually, once when I visted Bose, they had a a pair of big speakers out in the room in front a screen. They played some music, then low and behold they pulled back the curtain and therw were these Lil' cubes!! The only prblem was we were all agast at how bad the sound was!! Then when they pulled back the curtain we all went - "Oh, now I understand!!" The demo totally backfired.
Hi Frank
For some time before I was making full range loudspeakers, my job involved making intense sound for Acoustic Levitation experiments.
This was generally at 20 to 24KHz in frequency but was at very high sound levels.
Levitation begins at about 155 dB and array of six of the sound sources I eventually developed could produce about 175dB at the intersection, enough to levitate metals or ceramics, enough light a cigarette with acoustic friction.
I ended up working on that stuff in a weird way, I have no college at all, no math background in fact math is my worst subject but I guess I have gotten a feel for some thing’s.
I worked in electronics repair and loudspeakers my whole life however and got a job doing electronics first. After a few years I was in charge of electro acoustic research had a couple inventions that were important to the company and flown on the shuttle. Speakers were my first love though and had an idea for the Servodrive woofer that my boss let me pursue.
As a DIY’r and an inventor, I observed what happened, got ideas, tried them and revised my understanding of “how it works” based on what I already knew and could observe in experiments. I don’t claim to have “the book” of facts, most of the time it seems like you have to find out for your self in that particular set of conditions.
A few references to that kind of work.
http://books.google.com/books?id=3Y...&hl=en&sa=X&oi=book_result&resnum=2&ct=result
http://www.springerlink.com/content/42375j4148345603/
Anyway, the thing is Earl and I disagree some what about what conditions permit significant levels of higher order modes in a conical horn and I am in no position to argue the math.
The full spherical anechoic measurements we have to have taken for us, required in our industry for room acoustic and architectural design, are not directly comparable to Earls technique.
If you wish to see what a Synergy horn does spatially, down load the CLF file for an SH-50 and get the viewer program. It can provide most any information related to directivity and pattern control etc.
As soon as the trade show is over, I am planning to take measured data for Earl to process, I am curious how the 50’s look plotted that way.
Anyway, for example, from what I have seen with the waveguide loaded levitation sources, I would say in general that it would be difficult under any conditions to propagate any significant energy in higher modes from the throat if that throat is about 1 / 3 to 1 / 4 wavelength across or less. In sound cancellation, where one intentionally places an equal but opposite anti phase source as close as possible, at a quarter wavelength or less distance there is good cancellation and no complex radiation pattern.
Also, I would say that sound acts much like a simple pressure, flowing through ducts and around corners when the acoustic dimensions are small. Sound “waves” do not bounce off the corners in a bass horn at low frequencies, it acts more like a slug of air moving back and forth a tiny bit.
A pressure wavefront reaching a change in angle in a conical horn isn’t a problem unless it happens at an acoustic dimension large enough to be effecting /defining the radiation angle.
In the Conical horns we use, I have found that when using a driver that already produces a diverging wavefront at its exit like the ones we use, an imediate transition to the final angle is often better than a nice graceful looking transition (that shape imparts directivity that is different than the horn itself).
Within a compression driver one can see this. Sound is able to make right angle bends and such IF the dimensions are small enough.
Here is an example of a new invention which takes advantage of this principal.
http://www.vtcproaudio.com/technology/paraline.html
It takes the point source radiation produced by a conical source compression driver and passes the sound through acoustically small passages, then recombines the two halves such that the time of flight between the exit to the driver exit is the same.
This is kind of different than a normal horn too in that in one plane, the dimensions are much too small to have internal reflections while in the other plane, the horn has no physical boundary as the expansion is 360 degrees.
This produces a nice smooth response curve.
Drivers are not all the same;
While the “plane wave” exit behavior may be the tradition, measured drivers show there is a variety of different wavefronts produced depending on the phase plug and internal geometry.
By wavefront here I mean the progress of a pressure change caused by the radiator after some fixed time period.
An eyeball look at most ring type phase plugs shows that most would produce a converging wavefront at the summation point.
Since most horns of interest radiate a diverging wavefront, this condition, when the dimensions are sufficient for any directivity, is a recipe for hom’s or at least self-cancellation.
On the other hand, one can select a driver who’s internal horn is also a conical shape and do not radiate a plane or converging wavefront..
Not all compression drivers use a ring phase plug. Not all compression drivers with ring phase plugs produce an incompatible wavefront for a diverging horn.
Drivers all sound somewhat or very different from each other even when eq’d to the same response partly because of the higher order stuff that adds aural Que’s to the speakers physical location in space which competes with the spatial information in the recording.
Lastly, our horns are square or rectangular for several reasons.
Often these are used in multiples, large-scale sound requires much more output than home.
Conventional speakers interfere when placed side by side, but the horn geometry and source locations permit many of our products to be hard packed against others or a physical boundary with no audible interference (non of the swishy comb filtering that would normally be present).
At acoustic dimensions where the horn is providing directivity, the corners are somewhat shielded from the radiation pressure.
If you ever measured the reflection path into a corner, you know the acoustic path is shorter than the physical path. Sound in effect reaches the “closed end” before the physical boundary.
Anyway, by placing the mid and low frequency holes deep in the corners and making them as small as possible given the low pass filter that the trapped volume forms, they have no visible effect on the radiation pattern, cause no lobes or nulls.
Best,
Tom Danley
For some time before I was making full range loudspeakers, my job involved making intense sound for Acoustic Levitation experiments.
This was generally at 20 to 24KHz in frequency but was at very high sound levels.
Levitation begins at about 155 dB and array of six of the sound sources I eventually developed could produce about 175dB at the intersection, enough to levitate metals or ceramics, enough light a cigarette with acoustic friction.
I ended up working on that stuff in a weird way, I have no college at all, no math background in fact math is my worst subject but I guess I have gotten a feel for some thing’s.
I worked in electronics repair and loudspeakers my whole life however and got a job doing electronics first. After a few years I was in charge of electro acoustic research had a couple inventions that were important to the company and flown on the shuttle. Speakers were my first love though and had an idea for the Servodrive woofer that my boss let me pursue.
As a DIY’r and an inventor, I observed what happened, got ideas, tried them and revised my understanding of “how it works” based on what I already knew and could observe in experiments. I don’t claim to have “the book” of facts, most of the time it seems like you have to find out for your self in that particular set of conditions.
A few references to that kind of work.
http://books.google.com/books?id=3Y...&hl=en&sa=X&oi=book_result&resnum=2&ct=result
http://www.springerlink.com/content/42375j4148345603/
Anyway, the thing is Earl and I disagree some what about what conditions permit significant levels of higher order modes in a conical horn and I am in no position to argue the math.
The full spherical anechoic measurements we have to have taken for us, required in our industry for room acoustic and architectural design, are not directly comparable to Earls technique.
If you wish to see what a Synergy horn does spatially, down load the CLF file for an SH-50 and get the viewer program. It can provide most any information related to directivity and pattern control etc.
As soon as the trade show is over, I am planning to take measured data for Earl to process, I am curious how the 50’s look plotted that way.
Anyway, for example, from what I have seen with the waveguide loaded levitation sources, I would say in general that it would be difficult under any conditions to propagate any significant energy in higher modes from the throat if that throat is about 1 / 3 to 1 / 4 wavelength across or less. In sound cancellation, where one intentionally places an equal but opposite anti phase source as close as possible, at a quarter wavelength or less distance there is good cancellation and no complex radiation pattern.
Also, I would say that sound acts much like a simple pressure, flowing through ducts and around corners when the acoustic dimensions are small. Sound “waves” do not bounce off the corners in a bass horn at low frequencies, it acts more like a slug of air moving back and forth a tiny bit.
A pressure wavefront reaching a change in angle in a conical horn isn’t a problem unless it happens at an acoustic dimension large enough to be effecting /defining the radiation angle.
In the Conical horns we use, I have found that when using a driver that already produces a diverging wavefront at its exit like the ones we use, an imediate transition to the final angle is often better than a nice graceful looking transition (that shape imparts directivity that is different than the horn itself).
Within a compression driver one can see this. Sound is able to make right angle bends and such IF the dimensions are small enough.
Here is an example of a new invention which takes advantage of this principal.
http://www.vtcproaudio.com/technology/paraline.html
It takes the point source radiation produced by a conical source compression driver and passes the sound through acoustically small passages, then recombines the two halves such that the time of flight between the exit to the driver exit is the same.
This is kind of different than a normal horn too in that in one plane, the dimensions are much too small to have internal reflections while in the other plane, the horn has no physical boundary as the expansion is 360 degrees.
This produces a nice smooth response curve.
Drivers are not all the same;
While the “plane wave” exit behavior may be the tradition, measured drivers show there is a variety of different wavefronts produced depending on the phase plug and internal geometry.
By wavefront here I mean the progress of a pressure change caused by the radiator after some fixed time period.
An eyeball look at most ring type phase plugs shows that most would produce a converging wavefront at the summation point.
Since most horns of interest radiate a diverging wavefront, this condition, when the dimensions are sufficient for any directivity, is a recipe for hom’s or at least self-cancellation.
On the other hand, one can select a driver who’s internal horn is also a conical shape and do not radiate a plane or converging wavefront..
Not all compression drivers use a ring phase plug. Not all compression drivers with ring phase plugs produce an incompatible wavefront for a diverging horn.
Drivers all sound somewhat or very different from each other even when eq’d to the same response partly because of the higher order stuff that adds aural Que’s to the speakers physical location in space which competes with the spatial information in the recording.
Lastly, our horns are square or rectangular for several reasons.
Often these are used in multiples, large-scale sound requires much more output than home.
Conventional speakers interfere when placed side by side, but the horn geometry and source locations permit many of our products to be hard packed against others or a physical boundary with no audible interference (non of the swishy comb filtering that would normally be present).
At acoustic dimensions where the horn is providing directivity, the corners are somewhat shielded from the radiation pressure.
If you ever measured the reflection path into a corner, you know the acoustic path is shorter than the physical path. Sound in effect reaches the “closed end” before the physical boundary.
Anyway, by placing the mid and low frequency holes deep in the corners and making them as small as possible given the low pass filter that the trapped volume forms, they have no visible effect on the radiation pattern, cause no lobes or nulls.
Best,
Tom Danley
I've noticed the HOM-killing foam* has a much more audible effect on horns and waveguides which are NOT ideal.
For instance, I've used it on a OS waveguide, on a severely wonky tractrix horn, and on a OS waveguide with mouth termination that was non-existent.
The improvements were very notable with the tractrix horn, less so with the OS waveguide with proper mouth termination.
This is anything but rigorous, but seems to confirm that it's working.
It also indicates that the HOM foam would be very effective on a Unity or Synergy horn, since the throat and mouth are not "perfect."
* Dr Geddes, did you come up with a marketing term for that yet? "HOM killing foam" isn't exactly "catchy."
For instance, I've used it on a OS waveguide, on a severely wonky tractrix horn, and on a OS waveguide with mouth termination that was non-existent.
The improvements were very notable with the tractrix horn, less so with the OS waveguide with proper mouth termination.
This is anything but rigorous, but seems to confirm that it's working.
It also indicates that the HOM foam would be very effective on a Unity or Synergy horn, since the throat and mouth are not "perfect."
* Dr Geddes, did you come up with a marketing term for that yet? "HOM killing foam" isn't exactly "catchy."
Hi Tom
Our understanding and experinces are indeed different as I can measure throat errors in driver matching to the waveguide that are much smaller than you suggest. It may well be that it takes a very low diffraction device to measure low diffraction effects.
I don't see where you sound cancellation example has any relavence.
This statement:
"A pressure wavefront reaching a change in angle in a conical horn isn’t a problem unless it happens at an acoustic dimension large enough to be effecting /defining the radiation angle."
seems ill defined as I'm not sure what you are saying. A significant change in angle of the walls will cause a significant diffraction of the wavefront. The level of "significance" depends on several factors. The diffraction is directly dependent on the second derivative of the surface, which then needs to be integrated over a wavelength to get the level of the aberation. A sharp change in slope would thus have a strong effect on the higher frequencies, but little effect on the low fequencies. A gradual change has a diminished effect in all cases.
The statement:
"... flowing through ducts and around corners when the acoustic dimensions are small. Sound “waves” do not bounce off the corners in a bass horn at low frequencies, it acts more like a slug of air moving back and forth a tiny bit."
Again, I'm not sure what you are saying, but it seems to me to be a contradiction. If the sound flows around the corners then why would it just act like a "slug of air"?
What happens is that at low frequencies this "slug" of air (which is a correct analogy) is very small, while at high frequencies it is actually quite large - its inversly proportional to the wavelength. LFs can have sharp bends, but HFs don't like to bend. Thus, the LF would diffract more at a sharp mouth than the HFs as they wrap around the corner, but the same facts that I raised above apply making the situation pretty complex.
The acoustic dimension argument has its limitations. It can't be applied everywhere and in every situation and it will always be wrong to a certain extent. Where we differ is on when and where these limitations occur and how significant they are. We do agree on the extreme cases, like the small dimensions in a phase plug, but I don't agree on the intermediate cases, like the transition of round to square in a waveguide.
Our understanding and experinces are indeed different as I can measure throat errors in driver matching to the waveguide that are much smaller than you suggest. It may well be that it takes a very low diffraction device to measure low diffraction effects.
I don't see where you sound cancellation example has any relavence.
This statement:
"A pressure wavefront reaching a change in angle in a conical horn isn’t a problem unless it happens at an acoustic dimension large enough to be effecting /defining the radiation angle."
seems ill defined as I'm not sure what you are saying. A significant change in angle of the walls will cause a significant diffraction of the wavefront. The level of "significance" depends on several factors. The diffraction is directly dependent on the second derivative of the surface, which then needs to be integrated over a wavelength to get the level of the aberation. A sharp change in slope would thus have a strong effect on the higher frequencies, but little effect on the low fequencies. A gradual change has a diminished effect in all cases.
The statement:
"... flowing through ducts and around corners when the acoustic dimensions are small. Sound “waves” do not bounce off the corners in a bass horn at low frequencies, it acts more like a slug of air moving back and forth a tiny bit."
Again, I'm not sure what you are saying, but it seems to me to be a contradiction. If the sound flows around the corners then why would it just act like a "slug of air"?
What happens is that at low frequencies this "slug" of air (which is a correct analogy) is very small, while at high frequencies it is actually quite large - its inversly proportional to the wavelength. LFs can have sharp bends, but HFs don't like to bend. Thus, the LF would diffract more at a sharp mouth than the HFs as they wrap around the corner, but the same facts that I raised above apply making the situation pretty complex.
The acoustic dimension argument has its limitations. It can't be applied everywhere and in every situation and it will always be wrong to a certain extent. Where we differ is on when and where these limitations occur and how significant they are. We do agree on the extreme cases, like the small dimensions in a phase plug, but I don't agree on the intermediate cases, like the transition of round to square in a waveguide.
Patrick Bateman said:
Hi Patrick,
As you noted yourself, you're listening to only the midrange of your car system. While diffraction most certainly matters, please don't blindly attribute characteristics of what you heard in your car to those of all seemingly related designs. The shape of the horn used, the geometry of the parts, and crossover for the midrange-tweeter will all have very significant and audible effects. You created some major hurdles in getting adequate response from the midranges, and I would expect some audible oddities, especially without a crossover and a tweeter to mask them.
Hello,
How can we be sure that the only benefit of the foam was in the reduction of the HOMs?
Don't you think that the main effect specially for that "wonky tractrix" was the reduction of reflected waves from mouth to throat?
(BTW you wrote yourself that you are thinking that the foam will be effective "if the mouth termination was not perfect" and this is more related to reflected waves than to HOM.)
Best regards from Paris, France
Jean-Michel Le Cléac'h
How can we be sure that the only benefit of the foam was in the reduction of the HOMs?
Don't you think that the main effect specially for that "wonky tractrix" was the reduction of reflected waves from mouth to throat?
(BTW you wrote yourself that you are thinking that the foam will be effective "if the mouth termination was not perfect" and this is more related to reflected waves than to HOM.)
Best regards from Paris, France
Jean-Michel Le Cléac'h
Patrick Bateman said:
Hi Tom,
Gosh, that's a $100 answer to a $1 question. I do appreciate it very much.
I started out as a an innumerate audio DIY enthusiast in the 1960s when to oblige my Dad (a music nut) I cookbooked a Klipsch horn klone. (The mid-horns are monsters which were vastly improved by Earl's foam device). I have always been interested ever since.
I've always figured that if I thought about really narrow ducts - relative to wavelengths of interest, then - as long as turbulence isn't introduced - I don't have to be concerned about diffraction until the exit. So I figured the ducts for your mids would work nicely.
What brought up my question
was my possible misreading/misinterpretation of Earl's book p136 which has a list of separable coordinate systems of waveguide geometries in which a conical waveguide has an elliptical source aperture.
In my mind's eye I was converting the rectangular horn, including the extra material of the little smoothings at the corners of the throat, to a circular one, and then the aperture was no longer circular, but more elliptical: The extra material had to go somewhere didn't it?
It's possible I was raving at the time.
Your empirical finding here is interesting
In other words, no modification is better than the wrong one.
I think the Paraline device is elegant.
Gosh, that's a $100 answer to a $1 question. I do appreciate it very much.
I started out as a an innumerate audio DIY enthusiast in the 1960s when to oblige my Dad (a music nut) I cookbooked a Klipsch horn klone. (The mid-horns are monsters which were vastly improved by Earl's foam device). I have always been interested ever since.
I've always figured that if I thought about really narrow ducts - relative to wavelengths of interest, then - as long as turbulence isn't introduced - I don't have to be concerned about diffraction until the exit. So I figured the ducts for your mids would work nicely.
What brought up my question
was my possible misreading/misinterpretation of Earl's book p136 which has a list of separable coordinate systems of waveguide geometries in which a conical waveguide has an elliptical source aperture.
In my mind's eye I was converting the rectangular horn, including the extra material of the little smoothings at the corners of the throat, to a circular one, and then the aperture was no longer circular, but more elliptical: The extra material had to go somewhere didn't it?
It's possible I was raving at the time.
Your empirical finding here is interesting
In other words, no modification is better than the wrong one.
I think the Paraline device is elegant.
John, if your new waveguide will be three sides, will you use only two or three midranges? If you tuck the waveguide as close as you can to the corner of the windshield/dash, how do you fit a midrange on the windshield side? Also, if your not designing the midrange enclosures using bandpass enclosures as the model, what driver parameters are you using to find the optimum enclosure? It seems it would not longer be necessary to find a driver FS ~629 Hz (the optimum FS for the crossover points in the first version of your project) if the bandpass model is not the design anymore. Or maybe I am missing something.
Anyone, if you only put midranges on the A-pillar and dash sides of the waveguide (two of three sides), will the midrange performance suffer as the sources are not symmetrically spaced around the waveguide?
Anyone, if you only put midranges on the A-pillar and dash sides of the waveguide (two of three sides), will the midrange performance suffer as the sources are not symmetrically spaced around the waveguide?
Hi Mr. Tom Danley
Congratulations by your iso-path waveguide. Very good, simple and compact idea!
I have used a similar design in small 6.5” loudspeaker for medium frequencies and it works fine; however I did have many problems in extending the concept to Hi-frequencies.
Well… it is the difference between real genius and common mortals, I guess.
However, the way you have implemented the Rig-box-system introduces serious variations in the vertical inter-waveguide output distance!
Must confess that I am really disappointed that you have followed the wrong mechanical solution, compromising a product that otherwise has everything to be a winner.
Congratulations by your iso-path waveguide. Very good, simple and compact idea!
I have used a similar design in small 6.5” loudspeaker for medium frequencies and it works fine; however I did have many problems in extending the concept to Hi-frequencies.
Well… it is the difference between real genius and common mortals, I guess.
However, the way you have implemented the Rig-box-system introduces serious variations in the vertical inter-waveguide output distance!
Must confess that I am really disappointed that you have followed the wrong mechanical solution, compromising a product that otherwise has everything to be a winner.
Jmmlc said:
Jean-Michel
Finally something that we can agree on!!
Yes, you are quite correct that HOM reduction is not the only effect of the foam, there is also a strong reduction in internal resonance from the mouth reflection. And I also hypothesize that there is an effect that goes beyond even the damping of HOM and reflections having to do with a small random perturbation of the wavefront created by the fractal nature of the foam. Which efect is the greatest on audiblity is not know for certain and it may depend on the particular application which effect is the greater. But, for whatever reason, it is certain that anyone who has tried the foam is in absolute agreement that it is a significant improvement. This is measureable and audible. It is undeniable.
Mark Seaton said:
Hi Patrick,
As you noted yourself, you're listening to only the midrange of your car system. While diffraction most certainly matters, please don't blindly attribute characteristics of what you heard in your car to those of all seemingly related designs. The shape of the horn used, the geometry of the parts, and crossover for the midrange-tweeter will all have very significant and audible effects. You created some major hurdles in getting adequate response from the midranges, and I would expect some audible oddities, especially without a crossover and a tweeter to mask them.
The unity clone I did in 2006 was fundamentally screwed up, but it wasn't due to a flaw in the CONCEPT of the unity; it was due to a flaw in my execution.
Ironically, you told me how to fix it in 2006, but I wasn't paying attention! You were the only one in the entire 30 page thread that caught it.
In 2006 you told me to use an enclosure that was as small as possible for the mids. The enclosure that I used for midranges in my first stab at this were way too big.
That was HALF of the problem.
The other half of the problem was that I modeled the midrange response without taking into account what happens to the midrange response when you mount the midrange enclousures to the horn.
What this means is that the measured response WITHOUT the horn was acceptable, but once I mounted the mids to the horn, the response went to hell. I spent HOURS measuring the response of the mids, but I was doing it with the midrange enclosure alone; it wasn't even coupled to the horn.
OOPS.
It could be worse, there are tons of DIYers out there who don't even bother with measurements.
So once I settled on a crossover for the midranges, I mounted the mids to the horn, then couldn't figure out why the response around 1.5khz was just a mess. I tweaked the crossover to compensate for the ragged response around 1.5khz, but the fundamental issue was that the enclosure size was all wrong.
Of course the best solution is what you recommended - use the right midrange, put it in a VERY small enclosure, and use a front chamber for the midranges that's exceptionally small.
Which is exactly what you guys are doing with the Unity and Synergy horns.
loddie said:
It's going to use three - it's all I can fit. Currently I am using two per side in the test mules. Technically they handle 20watts total, but I'm powering them with a 400watt amplifier and they haven't exploded yet. A highpass network is a must to keep excursion from getting out of hand. If I had space for four I would user four.
The mids are attached to the waveguide, just like in a unity. The midrange performance will be far superior to what I did in 2006.loddie [/i]If you tuck the waveguide as close as you can to the corner of the windshield/dash said:
I'll post some pix, I need to find a USB cable for my camera.
If anyone wants to make a unity clone like mine, I've attached the plans for the mold.
Here's how I build my waveguide molds:
http://www.htguide.com/forum/showthread.php4?t=22137
The plans that I've attached are for a waveguide with a 1" throat and a triangular mouth. The coverage angle is fifty degrees IIRC. I'll post some pix of the mold as it's being built; it's about 40% complete. Should take a few days to finish.
Here's how I build my waveguide molds:
http://www.htguide.com/forum/showthread.php4?t=22137
The plans that I've attached are for a waveguide with a 1" throat and a triangular mouth. The coverage angle is fifty degrees IIRC. I'll post some pix of the mold as it's being built; it's about 40% complete. Should take a few days to finish.
part 3 of 3
Note that the first INCH of the waveguide requires layers that 1/8" thick. The rest of the waveguide requires layers that are 1/4" thick. The reason that I do this is that very small defects in the throat cause big problems. But errors which are further from the throat aren't as catastrophic. Therefore I use a very high resolution at the throat, but less so elsewhere.
As noted in the htguide post, I typically use cardboard to lay up the layers.
This time around I'm using wood, mostly because it's sturdier. I've had issues in the past with cardboard molds getting damaged.
Note that the first INCH of the waveguide requires layers that 1/8" thick. The rest of the waveguide requires layers that are 1/4" thick. The reason that I do this is that very small defects in the throat cause big problems. But errors which are further from the throat aren't as catastrophic. Therefore I use a very high resolution at the throat, but less so elsewhere.
As noted in the htguide post, I typically use cardboard to lay up the layers.
This time around I'm using wood, mostly because it's sturdier. I've had issues in the past with cardboard molds getting damaged.
I have 40 square feet of reticulated foam scheduled to arrive today, which I'll be using to create the foam plug for the waveguide. For the last unity I used 1/8" thick; this time around I'm using 1/4" thick.
There are two advantages to using a roll of foam. First, you can create the foam plug the exact same way you create the mold for the waveguide. Basically lay it up layer by layer. Second, a roll of foam is $93, while a solid "bun" of foam is thousands of dollars!
Of course, if you used a solid piece of foam you don't have to figure out a way to seal the layers together. As ghetto as this sounds, I used panty hose last time around LOL
Nylon panty hose is acoustically transparent, and has enough elasticity to bind the layers! Of course it looks completely ridiculous tho
Haven't decided what route I'll go this time around.
There are two advantages to using a roll of foam. First, you can create the foam plug the exact same way you create the mold for the waveguide. Basically lay it up layer by layer. Second, a roll of foam is $93, while a solid "bun" of foam is thousands of dollars!
Of course, if you used a solid piece of foam you don't have to figure out a way to seal the layers together. As ghetto as this sounds, I used panty hose last time around LOL
Nylon panty hose is acoustically transparent, and has enough elasticity to bind the layers! Of course it looks completely ridiculous tho
Haven't decided what route I'll go this time around.
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