I have been greatly amused at this thread and find the arguments on both sides educational. I am proponent of heavy -- 3/4" MDF>Liquid Nails>1/4" Hardibacker -- though I have been beaten down by public opinion and have gone stiff -- 1" Baltic birch. I must interject that Dave is correct about power/frequency distribution. It has been shown time and again the the power distribution in real music, particularly anything acoustic, is very close to pink noise -- equal power/octave. You can demonstrate this to yourself by running a spectrogram with a linear X-axis.
Some day, I'm going to do the experiment for myself: Build a box with a removable panel. Change out the removable panel with various materials. Measure the panel vibration with a surface pick-up.
Bob
Some day, I'm going to do the experiment for myself: Build a box with a removable panel. Change out the removable panel with various materials. Measure the panel vibration with a surface pick-up.
Bob
Hi Dave, Bob,
Okay, I completely agree with you that energy in music decreases as the frequency as raised. That's never been an issue of contention at all. If this wasn't the case, tweeters would be very impressive structures!
Now that we have that out of our system, can we refrain from confusing the issue that Dave and I were debating? I mean, never once during this exchange was the topic of music brought up. No, we were discussing what makes a better box construction and materials. I'm somewhat at a loss to understand why the direction is being driven off course here, because that is exactly what this last detour was all about.
No one I know of in the industry uses music to locate problem areas in a speaker prototype or design. They use music as part of the testing, but once they feel there is a problem, guess what they use? In fact, what do many responsible speaker driver manufacturers use to test raw drivers on or at the end of a production line? It ain't music, that's for sure. No, they run swept tone or specific frequencies. What do people use as a signal to test driver linearity? Tone(s), usually at the resonant frequency. A non-linear driver will create a Lissajous pattern that opens up or create some other interesting pattern.
So, Dave. Can you answer this without throwing in extraneous factoids and situations? I'm posting with the cleanest of intent, and I'm serious about what I'm saying.
Hi Bob,
Liquid nails is marvelous stuff! I for one do agree with your previous choice of building material. A short opinion from me is that stiff and dead makes the best enclosure or board to hang drivers in. Heavy really helps to make the enclosure non-reactive to whatever it is you are listening to.
All,
I'll advance another thought which seems to make sense to me. If you can hear the difference between various boxes, they are not dead and basically represent an unfinished design. The entire question of whether or not someone likes the sound of a box (given the proper internal dimensions and tuning) or not is a matter of personal taste. That's completely fine, but it does not prove that a box is built properly or not. All that means is that someone likes that box.
Boxes that are in fact built properly have been proved to be accepted by most people - given a choice over others that are not. No way am I going to attempt to repeat all the findings over several years, that stuff is out there for the reading. Yes, the listening tests have agreed with the measured figures. Horrors!
-Chris
Okay, I completely agree with you that energy in music decreases as the frequency as raised. That's never been an issue of contention at all. If this wasn't the case, tweeters would be very impressive structures!
Now that we have that out of our system, can we refrain from confusing the issue that Dave and I were debating? I mean, never once during this exchange was the topic of music brought up. No, we were discussing what makes a better box construction and materials. I'm somewhat at a loss to understand why the direction is being driven off course here, because that is exactly what this last detour was all about.
No one I know of in the industry uses music to locate problem areas in a speaker prototype or design. They use music as part of the testing, but once they feel there is a problem, guess what they use? In fact, what do many responsible speaker driver manufacturers use to test raw drivers on or at the end of a production line? It ain't music, that's for sure. No, they run swept tone or specific frequencies. What do people use as a signal to test driver linearity? Tone(s), usually at the resonant frequency. A non-linear driver will create a Lissajous pattern that opens up or create some other interesting pattern.
So, Dave. Can you answer this without throwing in extraneous factoids and situations? I'm posting with the cleanest of intent, and I'm serious about what I'm saying.
Hi Bob,
Liquid nails is marvelous stuff! I for one do agree with your previous choice of building material. A short opinion from me is that stiff and dead makes the best enclosure or board to hang drivers in. Heavy really helps to make the enclosure non-reactive to whatever it is you are listening to.
All,
I'll advance another thought which seems to make sense to me. If you can hear the difference between various boxes, they are not dead and basically represent an unfinished design. The entire question of whether or not someone likes the sound of a box (given the proper internal dimensions and tuning) or not is a matter of personal taste. That's completely fine, but it does not prove that a box is built properly or not. All that means is that someone likes that box.
Boxes that are in fact built properly have been proved to be accepted by most people - given a choice over others that are not. No way am I going to attempt to repeat all the findings over several years, that stuff is out there for the reading. Yes, the listening tests have agreed with the measured figures. Horrors!
-Chris
I'm about to collapse for the night but FWIW, a couple of general thoughts:
-The concept of 'dead' enclosures is somewhat misleading, because the issue is simply how the panels of an enclosure can be rendered ~acoustically innocuous. While most people assume the term 'dead enclosure' to refer to high-mass panels, in fact it could equally be said to apply to a cabinet with very light, stiff panels, because the box is acoustically benign / 'dead' within its functional bandwidth, as their natural resonant frequency is above this region, and little or no energy exists to excite them.
-Although MDF is often described as being a stiff material, it requires substantially greater thicknesses and / or greater bracing to ~equal the stiffness of a decent grade of void free plywood, as clearly shown in average MOE specs.
-If we accept that it is impractical to push panel Fs & harmonic structure sufficiently far below the functional BW of the enclosure to be easily damped out (i.e. rendered acoustically ~innocuous), and that pushing it upward is likely to be the more viable proposition (esp. given that energy available to excite panels rapidly falls away as frequency increases, as noted above), then logic suggests that it makes sense to deploy a material that has a higher Fs in the first place.
-The concept of 'dead' enclosures is somewhat misleading, because the issue is simply how the panels of an enclosure can be rendered ~acoustically innocuous. While most people assume the term 'dead enclosure' to refer to high-mass panels, in fact it could equally be said to apply to a cabinet with very light, stiff panels, because the box is acoustically benign / 'dead' within its functional bandwidth, as their natural resonant frequency is above this region, and little or no energy exists to excite them.
-Although MDF is often described as being a stiff material, it requires substantially greater thicknesses and / or greater bracing to ~equal the stiffness of a decent grade of void free plywood, as clearly shown in average MOE specs.
-If we accept that it is impractical to push panel Fs & harmonic structure sufficiently far below the functional BW of the enclosure to be easily damped out (i.e. rendered acoustically ~innocuous), and that pushing it upward is likely to be the more viable proposition (esp. given that energy available to excite panels rapidly falls away as frequency increases, as noted above), then logic suggests that it makes sense to deploy a material that has a higher Fs in the first place.
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For building backloaded horns, yes plywood is a very fine choise, in many ways
And it may be one of the best you can buy, easy to use and ready to go, so to speak
But as said, there are other ways that might prove even better
Like using a mix of several materials
I wouldnt just stick to narrowing it down to either MDF or plywood, but also look at other options
Anyone know those boards that are used in bottom of small trailers
Dark brown, exstremely tough, heavy, hard, and waterproof
I think its a kind plywood too
Hell, polyfoam with 6mm plywood on each side could show to be the best ever
and if you think it wont be very stiff, better think again
And it may be one of the best you can buy, easy to use and ready to go, so to speak
But as said, there are other ways that might prove even better
Like using a mix of several materials
I wouldnt just stick to narrowing it down to either MDF or plywood, but also look at other options
Anyone know those boards that are used in bottom of small trailers
Dark brown, exstremely tough, heavy, hard, and waterproof
I think its a kind plywood too
Hell, polyfoam with 6mm plywood on each side could show to be the best ever
and if you think it wont be very stiff, better think again Actually the peak is at 200Hz. But are you saying the Pencil enclosure is flawed?
I'm sorry, but I strongly disagree with you here.
You said:OK so far, but...
If you only change the mass, "the amount of energy transferred to the enclosure as a system" does not change.
Quite a few years ago, it was fairly common practice for low-end speaker enclosure manufacturers to glue the woofer cutout disc to the inside of the back panel. One would like to think they did it to attempt to reduce the panel resonance, but I suspect it had more to do with reducing the waste wood disposal problem and making the enclosure appear heavier (sales appeal). Whatever, I used to smile when I saw it, because it usually made the resonance worse (increase in mass, no decrease in compliance equals lower resonant frequency and thus more readily excited by the higher energy levels at lower frequencies.)
.......with its wider BW (longer decay time) that makes the cab 'colorful', not to mention robs the speaker of some efficiency, something point source drivers can ill afford.
GM
You were the one leading us off-course. The box (with the speaker driver) has the job of reproducing music. It is the source that provides the energy that causes the problems. Elegant design takes that into consideration. It works much better than brute force.
It isn't a problem if the music doesn't make it an issue. Keeping in mind what energy the box will be exposed to in use is just smart design. Saying a high frequency resonance that you can excite with your sine wave generator is a problem, when in actual fact, if it is never excited because music cannot supply the energy to excite it is just silly, especially if you use that as an argument to put the resonance somewhere where it is more likely to be excited.
It is nice to know where it is, so that you can make sure you have placed it high enuff that it won't be a problem.
And i have read much of it. Then built stuff using what i read. Then revised based on what i learned from the build.
dave
Very high quality plywood. The Mercedes stuff i have here has a layer of textured non-slip platic/rubber on it.
There is no question that a constrained layer/multilayer construction is a good choice for speaker building... a good multiply is, in essence, a minimalist, premade instance of such a material.
dave
I was wondering if tinitus was referring to Crezone, or form plywood. (concrete forms, that is)
I've used it on trailer decks, &c.
If so, you wouldn't want it in the house!!
Don
I think you answered that question yourself
http://www.diyaudio.com/forums/markaudio/165297-pencil-7-alpair-7-a-3.html#post2196837
You will note that bracing is recommended for maximum performance (this has been explained more thoroughly in the lastest iteration of the plans document, still in QC).
This is not an issue with the Pensil, but with any loudspeaker panel of a certain size & stiffness (or lack of).
But given that the bracing can be as much or more work than the box, sometimes it comes down to build the box with no braces or don't build a box at all... the 1st will have an edge.
dave
Hi Don,
I agree with you completely. Just for the record, my stance does not exclude plywood or anything else that is reasonable to use. My entire point is that MDF and HDF are also suitable for creating good boxes.
The changing amount energy applied to the system thing was Dave's contribution. However, there is a major point that I think is being missed here. There is also a coupling efficiency at work. That operates in two ways, both energy into storage in the enclosure materials, and coupling that energy back out into the medium (air). This is the entire concept behind the horn loaded loudspeaker. The basic idea is to couple energy from an acoustically high impedance device, the driver, into a low acoustic impedance medium, air. The horn structure operates as a mechanical transformer to better match the two disparate acoustic impedances.
I think a corrected statement could be worded as "If you only change the mass, "the amount of energy transferred to the enclosure as a system" does in fact change. Italics mine.
The reason is that although the system with added mass is exposed to the same energy sources (so that remains constant), less of that energy can be coupled to the box. Even if exactly the same amount of energy had been stored inside the box system, the free motion of the panels will be less than in the case of a lighter material.
Look at the equation F=ma. Force = (mass) X (acceleration). So for any instant in time, the force being fixed at each comparison point, added mass must decrease the available acceleration. That means less movement of any parts of the box system that are heavier. The source of this force is both air and a reactionary force applied directly to the mounting surface of the box due to the force the driver applies to the air. Is this correct, or is there a reasonable argument contrary to what I've just posted?
Okay, the air is a low acoustic impedance medium, compare to liquid water for example. This moving air as a pressure wave acts on the interior walls of our box. Being heavier with equivalent stiffness to any other material, the MDF or HDF is displaced a shorter distance. That means that unless the material is being compressed (not likely for any magnitude that should concern us), less displacement internally equates to less displacement of any panel externally. Even if you were to suspend equivalent sized objects in a vacuum, the heavier of the two will be moved less than the lower mass object when pushed by equal forces. This example has very, very low stiffness - excluding stiffness as a factor for that experiment. Yeah, I know. No one listens to music in a vacuum. Never mind that sound would not be created in a perfect vacuum. Everyone got that out of their system now?
This discussion bring to mind a well known "high end" speaker brand. B&W used what can only be described as LDF, low density fiber board. There was no surface treatment used and the chip board was thirsty. Now a page from the light and stiff proponents, the baffle was injection molded plastic, and not Lexan either. It was butt jointed to the front edge of the sides, top, bottom and back. Spared no expense, no glue either. Well, that front baffle went ahead and did what many people would expect it to do. It shook itself free in varying degrees as the years passed. The screws holding this plastic wonder went into the "end grain" of the light particle board. The woofer was an odd basket size as well. The molded plastic mounting area meant that a blown woofer could only be replaced with an identical driver. I'm pretty sure that was one reason for the light, plastic baffle. The other was a huge reduction in labor to assemble these little monsters. Granted, this is an extreme case that does not represent the opposing view that others have argued.
Another example for you. How many people have heard of a product called "Dynamat"? That's the stuff they started applying to the metal panels in cars to prevent the metal from vibrating and reduce the amount of acoustic contribution from those metal panels. The link is to their web site, but read on people. The product works by adding mass and laminating a dissimilar thickness of material to those light and very stiff metal panels. According to some of you, this product shouldn't work, and yet it has for 21 years!
In closing, the only thing I have said is that MDF and HDF both work very well for speaker boxes. This is true for many types of materials. If the material used to make a box tends to store and release energy, surface damping will be required to kill off surface waves and also to reduce energy transmitted into the material. In the case of any wood used in speaker boxes (indeed, in anything) needs to be sealed to prevent long term damage due to water vapor or mist. Even if you used a metallic material for the box, protection from water is required. Although in some cases you may only see light surface corrosion.
-Chris
I agree with you completely. Just for the record, my stance does not exclude plywood or anything else that is reasonable to use. My entire point is that MDF and HDF are also suitable for creating good boxes.
Agreed to a point.
The changing amount energy applied to the system thing was Dave's contribution. However, there is a major point that I think is being missed here. There is also a coupling efficiency at work. That operates in two ways, both energy into storage in the enclosure materials, and coupling that energy back out into the medium (air). This is the entire concept behind the horn loaded loudspeaker. The basic idea is to couple energy from an acoustically high impedance device, the driver, into a low acoustic impedance medium, air. The horn structure operates as a mechanical transformer to better match the two disparate acoustic impedances.
I think a corrected statement could be worded as "If you only change the mass, "the amount of energy transferred to the enclosure as a system" does in fact change. Italics mine.
The reason is that although the system with added mass is exposed to the same energy sources (so that remains constant), less of that energy can be coupled to the box. Even if exactly the same amount of energy had been stored inside the box system, the free motion of the panels will be less than in the case of a lighter material.
Look at the equation F=ma. Force = (mass) X (acceleration). So for any instant in time, the force being fixed at each comparison point, added mass must decrease the available acceleration. That means less movement of any parts of the box system that are heavier. The source of this force is both air and a reactionary force applied directly to the mounting surface of the box due to the force the driver applies to the air. Is this correct, or is there a reasonable argument contrary to what I've just posted?
Okay, the air is a low acoustic impedance medium, compare to liquid water for example. This moving air as a pressure wave acts on the interior walls of our box. Being heavier with equivalent stiffness to any other material, the MDF or HDF is displaced a shorter distance. That means that unless the material is being compressed (not likely for any magnitude that should concern us), less displacement internally equates to less displacement of any panel externally. Even if you were to suspend equivalent sized objects in a vacuum, the heavier of the two will be moved less than the lower mass object when pushed by equal forces. This example has very, very low stiffness - excluding stiffness as a factor for that experiment. Yeah, I know. No one listens to music in a vacuum. Never mind that sound would not be created in a perfect vacuum. Everyone got that out of their system now?
Actually, that was done so that the terminal area could be recessed into the rear panel. The fact that the excess material was shipped out with the box is quite beside the fact. I think they may not do that often these days as it creates a weight penalty when shipping. Not much, but the have trimmed everything down as far as possible. If I were directing a speaker manufacturing line and was required to have inset speaker terminals, I would most definitely use the woofer cut out waste. Wouldn't you? Oh, and almost everyone did that, not just the "low end manufacturers". The other point I should make is that there wasn't all that much weight to these cutouts. But the true plus in doing this was probably unintentional. It laminated a small section that did increase the stiffness in that location and changed the resonant frequencies on that rear panel. Note that very seldom did many manufacturers use effective bracing or stiffening ribs. I used to love Cerwin Vega boxes. They would completely disassemble themselves. The brace front to back was hot glued in - as were all the other panels. It was almost always found detached at the bottom of the box behind the loose baffle.
This discussion bring to mind a well known "high end" speaker brand. B&W used what can only be described as LDF, low density fiber board. There was no surface treatment used and the chip board was thirsty. Now a page from the light and stiff proponents, the baffle was injection molded plastic, and not Lexan either. It was butt jointed to the front edge of the sides, top, bottom and back. Spared no expense, no glue either. Well, that front baffle went ahead and did what many people would expect it to do. It shook itself free in varying degrees as the years passed. The screws holding this plastic wonder went into the "end grain" of the light particle board. The woofer was an odd basket size as well. The molded plastic mounting area meant that a blown woofer could only be replaced with an identical driver. I'm pretty sure that was one reason for the light, plastic baffle. The other was a huge reduction in labor to assemble these little monsters. Granted, this is an extreme case that does not represent the opposing view that others have argued.
Another example for you. How many people have heard of a product called "Dynamat"? That's the stuff they started applying to the metal panels in cars to prevent the metal from vibrating and reduce the amount of acoustic contribution from those metal panels. The link is to their web site, but read on people. The product works by adding mass and laminating a dissimilar thickness of material to those light and very stiff metal panels. According to some of you, this product shouldn't work, and yet it has for 21 years!
In closing, the only thing I have said is that MDF and HDF both work very well for speaker boxes. This is true for many types of materials. If the material used to make a box tends to store and release energy, surface damping will be required to kill off surface waves and also to reduce energy transmitted into the material. In the case of any wood used in speaker boxes (indeed, in anything) needs to be sealed to prevent long term damage due to water vapor or mist. Even if you used a metallic material for the box, protection from water is required. Although in some cases you may only see light surface corrosion.
-Chris
Hi Dave,
Dave, I'm sorry. You have no way to quantify any problems in a box, nor any effective way to solve those problems if you refuse to use sine wave excitation and measurements. The continual comments about listening to speakers with music has been an effective way to muddy the waters and attempt to explain how you seem to hand tune an enclosure by ear alone. I'm sorry Dave, but that clearly will not cut it in the real world with millions riding on how good your speakers sound. However, I should have seen this coming as a result of your other acoustic activities, such as treating loudspeaker cones - again by ear alone.
Using test equipment and scientific procedures in developing an audio product does not occur in place of listening tests. They support listening tests and help to keep you on track, to know what changes are better, and what constitutes a personal preference. Measurements allow you to quantify a problem so that you can actually see how you are progressing in a solution. They also alert you to a situation where a fix in one area creates trouble in another. Much the same way as listening tests work to keep the measurements honest, again keeping you on the right track.
I don't know about you, but I've found that testing speakers, enclosure response and finding vibrations has improved my end results. The better the equipment I get usually allows me to create better speaker systems. When I hear something in a listening test, measurements help me to locate what I heard and address the issue. The other thing I've found is that my ears are not always right. Too much depends on external factors and I'm not so arrogant to believe I can't be wrong with my ears.
To post any more with you on this topic is a completely useless exercise and a total waste of my time. Dave, it is you who pushed things off topic. It's also you who is being exclusionary, both with materials and even the idea that measurements can help out. Accusing me of running this discussion off topic doesn't fit with the facts as I can see, but it clearly shows the futility in discussing things with you.
-Chris
You have got to be kidding me! Still with the music and listening to find and document problems?
Dave, I'm sorry. You have no way to quantify any problems in a box, nor any effective way to solve those problems if you refuse to use sine wave excitation and measurements. The continual comments about listening to speakers with music has been an effective way to muddy the waters and attempt to explain how you seem to hand tune an enclosure by ear alone. I'm sorry Dave, but that clearly will not cut it in the real world with millions riding on how good your speakers sound. However, I should have seen this coming as a result of your other acoustic activities, such as treating loudspeaker cones - again by ear alone.
Using test equipment and scientific procedures in developing an audio product does not occur in place of listening tests. They support listening tests and help to keep you on track, to know what changes are better, and what constitutes a personal preference. Measurements allow you to quantify a problem so that you can actually see how you are progressing in a solution. They also alert you to a situation where a fix in one area creates trouble in another. Much the same way as listening tests work to keep the measurements honest, again keeping you on the right track.
I don't know about you, but I've found that testing speakers, enclosure response and finding vibrations has improved my end results. The better the equipment I get usually allows me to create better speaker systems. When I hear something in a listening test, measurements help me to locate what I heard and address the issue. The other thing I've found is that my ears are not always right. Too much depends on external factors and I'm not so arrogant to believe I can't be wrong with my ears.
To post any more with you on this topic is a completely useless exercise and a total waste of my time. Dave, it is you who pushed things off topic. It's also you who is being exclusionary, both with materials and even the idea that measurements can help out. Accusing me of running this discussion off topic doesn't fit with the facts as I can see, but it clearly shows the futility in discussing things with you.
-Chris
Not without more work... in some cases a lot more.
But only that vibrational energy within the bandwidth of the resonance is useful for exciting the resonance.
All that does is tell us that the more massive panel will have a lower frequency resonance, since acceleration is proportional to frequency.
dave
But i do. I use them to make sure my resonances are up high enuff that they won;t get excited by the music. If they are not ever excited it is as if they don't exist.
What do we use speakers for but to listen to music?
And you are the one suggesting that my enclosures are hand-tuned. Straight forward physics and simple measurements are what i use to design my enclosures (that, 45 years of experience and thinking about the essence of the problems at hand so as to apply the physics eleganty*)
*(all panels resonate, music is the source of energy, if we can't eliminate the resonances where can we put them so as to make them as little problem as possible, everything follows from that (tempered by being a frugal-phile (tm)))
As to the other slurs, i will just be happy with the smiles of pleasure on those who have built my designs or bought my drivers. Oh, and my ear-to-ear grin when i sit down to listen to the music (after all, in the end, the whole point is to enjoy the music).
dave
Hi Dave,
Look, no way is anything intelligent going to come from posting with you. Too many variables get thrown in after they are assumed to be constant for a particular point. If that won't work, you thrown in listening. Something completely off target when trying to come up with something along the lines of construction materials and best practices. I have clearly stated when listening tests are of use, and any dummy can figure out that home speakers are usually used for listening to music.
As for performing measurements, I can't tell one way or the other how you go about things. You are making statements that say to me that they may either be cursory, or perhaps not terribly important to you. Whatever the truth is, it matters not to me. Since you haven't explained your methods to anyone in this thread, it only appears that you listen to wood and go by ear. That was my impression.
If you feel that MDF or HDF is inferior material, and it's clear that you do, then I feel your position is not helpful to anyone reading this thread. In fact, this quote from you early on in this thread kinda says it all ...
Dave, it comes down to your opinion, which I strongly disagree with. Of course I also have an opinion that clearly you disagree with also. But that is no reason to play around with answering or talking about the subject clearly. Also remember. Both of us have a great deal of experience with sound reproduction. There are plenty of other members around here that have similar experience, yet you seem to be of the opinion that no one else's direct experience may have some truth to them. I find that disrespectful in the extreme. My personal suggestion to you would be to re-evaluate how MDF is used and the proper ways of working with it. Also, you really might want to do some in depth testing of your own box construction and look for internal vibration modes and released energy. To be honest with you, plywood (no voids) or solid wood (yes, I've used that as well) can be more difficult to tame than MDF is. Either way, you have to work to make whatever material you use perform properly. I wouldn't say that MDF is more difficult, and I have had good success using ply. The only person here with a problem is you. I don't think you've considered using a good MDF since perhaps a poor experience with it years ago. I don't know how you work with MDF, but I strongly suspect your unhappiness with it is a result of your own ways of building with it.
Look, no way is anything intelligent going to come from posting with you. Too many variables get thrown in after they are assumed to be constant for a particular point. If that won't work, you thrown in listening. Something completely off target when trying to come up with something along the lines of construction materials and best practices. I have clearly stated when listening tests are of use, and any dummy can figure out that home speakers are usually used for listening to music.
Maybe for you. I've built so many different designs over the years that doesn't bear that out it's silly. In actual fact, I find things to be opposite to what you just made a claim for. I will concede that any box requires a fair amount of work to build correctly. But somewhere along the line, you dragged out the argument that a defective box is better than having no box. That comment doesn't hold water when we are talking about DIY and home builders that simply want to know the best way, or acceptable ways to build a good speaker box.
As for performing measurements, I can't tell one way or the other how you go about things. You are making statements that say to me that they may either be cursory, or perhaps not terribly important to you. Whatever the truth is, it matters not to me. Since you haven't explained your methods to anyone in this thread, it only appears that you listen to wood and go by ear. That was my impression.
If you feel that MDF or HDF is inferior material, and it's clear that you do, then I feel your position is not helpful to anyone reading this thread. In fact, this quote from you early on in this thread kinda says it all ...
What you have said there is a good view into your thinking about this. Really, you should have left it at that, or if you wanted to comment further, answer directly. In particular, the last comment you made in that quote is pure nonsense put in the form of a fact. This is your belief, and I know you are incorrect. The only thing this tells me is that you don't know how to properly use MDF. Of course, HDF is a completely different animal, but you should know that - right?
Dave, it comes down to your opinion, which I strongly disagree with. Of course I also have an opinion that clearly you disagree with also. But that is no reason to play around with answering or talking about the subject clearly. Also remember. Both of us have a great deal of experience with sound reproduction. There are plenty of other members around here that have similar experience, yet you seem to be of the opinion that no one else's direct experience may have some truth to them. I find that disrespectful in the extreme. My personal suggestion to you would be to re-evaluate how MDF is used and the proper ways of working with it. Also, you really might want to do some in depth testing of your own box construction and look for internal vibration modes and released energy. To be honest with you, plywood (no voids) or solid wood (yes, I've used that as well) can be more difficult to tame than MDF is. Either way, you have to work to make whatever material you use perform properly. I wouldn't say that MDF is more difficult, and I have had good success using ply. The only person here with a problem is you. I don't think you've considered using a good MDF since perhaps a poor experience with it years ago. I don't know how you work with MDF, but I strongly suspect your unhappiness with it is a result of your own ways of building with it.
Listening only comes into it as far as defining the source of the energy available to excite a resonance. If you have extropolated that to imply that the structural box designs come about by listening that is your mistake.
I've tried to be very clear. I do find myself trying over & over again to make the same point...
Been there, done that. And continue to.
dave
I'm with Dave on this MDF.
The BBC commisioned a study on the best material for a speaker enclosure and MDF was the worst. ( BBC RD 1977/3 - Factors in the design of loudspeaker cabinets, January 1977).
I've build 12 and 15" Karlson enclosures and they always worked best with ply. With MDF they would reverb tremendously, particle board was better and ply was the best. However many manufacturers love MDF because it machines so easily.
Another item to consider is that speakers are often made as cheap as possible and great improvements can be achieved by mounting the speaker by the magnet and have a flexible seal between baffle and speaker.
IMHO one of the biggest mistakes is to overlook transient response and/or dynamics in favour of frequency extension or the flatness of the response. The latter will most definitely not be flat once introduced into a living room. In the case it is not flat it better to use a good equalizer up-stream to achieve this (rather than using passive components and introduce phase issues) and focus on the other aspects.
One of my pet faves is the "beaming" and "critical placement" of speakers and although the Karlson's are poo-poo'd by a lot of people they have a lot of good things going for them when build well.
AM
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HDF is certainly quite a bit better than MDF, but doesn't offer as attractive set of positives as similarily priced plywood. It is worth using if you can't find good ply.
dave
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