markp said:
That would only be true in a perfect world. Since lasers can track sound coming through a window, we know that any enclosed space transmits sound from inside to outside (and vice versa). The "dead or alive" debate is whether you want the walls of the enclosure to damp the vibrations or not. Based on what has been said, I'm guessing that both Eric and Nelson want their enclosures to be half-alive or barely alive. Me, I like my walls not to have ears.
🙂ensen.
The Air Does not resonate
MarkP,
It is the air pressure or sound waves and the speaker's mechinical connection to the enclosure that cause the cabinet or the panels to resonate. A box will posses a series of resonant mode due to torsion panel flexure and the frequency and magnatuide dependant on the Q of the material and also the thickness and density.
MarkP,
It is the air pressure or sound waves and the speaker's mechinical connection to the enclosure that cause the cabinet or the panels to resonate. A box will posses a series of resonant mode due to torsion panel flexure and the frequency and magnatuide dependant on the Q of the material and also the thickness and density.
The idea is to get rid of said flexures and resonances. The driver and the port (if any) are the only things that should be a source of sound. Yes, in reality cabinets do vibrate, but should they? I say no.
Re: Wood Can Be Good...........
Also my experience.
This issue is very much like the amplifier distortion issue,
with one side saying "If it measures better, it must be better"
and the other saying "I like this sound, so p-off."
I don't want to be misunderstood on this. I have not really
expressed a preference except that I find the acoustically
live mechanical systems more interesting, just as I find simple
circuits more interesting. I am less interested in rigid pistons
(at least not the acoustic kind 😉 ) and dead enclosures
because I understand them much better.
I have heard good and bad from both camps. No matter which
approach you take, there is no substitute for hard work and
good taste.
mrfeedback said:
Also my experience.
This issue is very much like the amplifier distortion issue,
with one side saying "If it measures better, it must be better"
and the other saying "I like this sound, so p-off."
I don't want to be misunderstood on this. I have not really
expressed a preference except that I find the acoustically
live mechanical systems more interesting, just as I find simple
circuits more interesting. I am less interested in rigid pistons
(at least not the acoustic kind 😉 ) and dead enclosures
because I understand them much better.
I have heard good and bad from both camps. No matter which
approach you take, there is no substitute for hard work and
good taste.
purplepeople said:
Actually LASERS used to "Listen" at great distances are not picking up sound but the vibrations of the glass. A timing circuit measures the distance the beam has travelled to the reflecting surface and back. The shorter the time the higher the frequency, this is because the reflecting surface is actually moving closer and further away from the point source as it vibrates with the sound pressure acting upon it.
If your going to abuse the laws of physics at least get the science right. 🙂
Anthony
I have been wondering of late what would happen if I placed a microphone inside a speaker cabinet and used the output to drive a signal 180 Deg. out of phase to another speaker inside the same cabinet, would there be any sound at all. If there were no resonance sound waves acting on the cabinet walls would the construction materials be of any great significance?
Anthony
Anthony
Re: Re: Wood Can Be Good...........
What abuse? Tracking something with radiation usually involves some application of the Doppler principle. Besides, I don't want to debate whether sound is the transmission through some material of frequencies from 20-20kHz or the actual frequencies themselves. That would just lead to the age old question of the hardwood tree falling in the forest...
Okay, sorry for making it seem that way. Do you find them interesting because they are so hard to finesse? IWO, the problem itself is interesting?
🙂ensen.
Coulomb said:
purplepeople said:
What abuse? Tracking something with radiation usually involves some application of the Doppler principle. Besides, I don't want to debate whether sound is the transmission through some material of frequencies from 20-20kHz or the actual frequencies themselves. That would just lead to the age old question of the hardwood tree falling in the forest...
Nelson Pass said:
Okay, sorry for making it seem that way. Do you find them interesting because they are so hard to finesse? IWO, the problem itself is interesting?
🙂ensen.
Hello!
[regarding x. onasis comments]
I think I've stated my reasons for not using hardwoods already, but I'll make a final write up here.
Hardwoods in sheet form lack dimensional stability that MDF has. I'm not saying it cannot be used at all, but there are better choices available. For a number of reasons solid woods like this tend to expand and contract which can introduce cracks and air gaps in the enclosure.
A problem that also poses itself is that of knots/voids. These cause problems as the debris inside them can buzz around and make - a buzzing sound. That's what I'm concerned about with voids mostly, apart from the fact that voids make the wood less stiff to a degree (although this is a minor issue as the voids are usually small enough not to cause any strength problems).
Hardwood's also tend to be less damped and therefore more prone to panel resonance. MDF on the other hand has particle orientation in all directions and bonded with glue so it is less prone to resonance.
Cost is also another factor and large sheets of hardwood costs heaps, more than veneer does. Recently I've built hall table for my house and I had to investigate the prices of many timbers to come to the final decision and hardwood in sheet form is real expensive. I may suggest for loudspeaker enclosures, pre-veneered MDF is available which may be another attractive option for people who want the veneer, but arn't prepared to apply it themselves. Pre-veneered MDF is also cheaper than sheet hardwoods. Of course, it depends what type of hardwood is used. But I've found that the majority are still very expensive.
And the other issue at play is that of weight. Hardwood weighs heaps, a lot more than MDF. That makes it unattractive particularly for larger enclosures.
> Also, you say it has resonance problems that need to
> be "fixed", so what wrong with that? Bracing MDF is fixing a
> problem, certainly _that's_ acceptable, yes?
The point is that hardwoods are more prone to panel resonance than MDF regardless of bracing. Bracing still needs to be used on both materials to stiffen the enclosure so that its out of the range where it can be excited. But the properties of MDF still makes it less prone to panel resonance either way.
[regarding ron's comments]
Certainly, there are numerous musical instruments which rely on resonances to produce the desired note or tone. But it's the loudspeakers job to reproduce it, and not cabinet resonance. If it doesn't sound natural, then it's not up to the cabinet to flex at exactly the right frequency to "make up" for it. Panel resonance will appear as chaotic behaviour in the response, much like cone breakup modes. It's certainly something we don't want, so one can look at it carefully and minimize them from analysis. Typically its rather unpredictable too. But if you want the loudspeaker to faithfully reproduce the musical intrument, then it should be designed to do just that - but panel resonances certainly cannot be viewed as an option to "assit" the driver in whats taking place. Panel resonance is just that, chaotic behaviour, much like a kid behind the wheel of a car with no license. It's "all over the place".
I think I've made it pretty clear why panel resonance is not a good thing, and I've been quite adamant about it. There's no way that panel resonances can be "fiddled" with to make a speaker sound "just right". It's simply not what panel resonances do. Onto the topic of hardwood I think its pretty clear why MDF or plywood should be preferanced first. If one does want to employ a hardwood, then I'd suggest to approach it very carefully and ensure that your making the right selection. But really its counterproductive because other materials are much more suited and cost less too. And if veneer is posing a problem, then pre-veneered MDF can be used instead, or a cabinet maker or somebody with a "better hand" can do the job for you instead.
Adrian
[regarding x. onasis comments]
I think I've stated my reasons for not using hardwoods already, but I'll make a final write up here.
Hardwoods in sheet form lack dimensional stability that MDF has. I'm not saying it cannot be used at all, but there are better choices available. For a number of reasons solid woods like this tend to expand and contract which can introduce cracks and air gaps in the enclosure.
A problem that also poses itself is that of knots/voids. These cause problems as the debris inside them can buzz around and make - a buzzing sound. That's what I'm concerned about with voids mostly, apart from the fact that voids make the wood less stiff to a degree (although this is a minor issue as the voids are usually small enough not to cause any strength problems).
Hardwood's also tend to be less damped and therefore more prone to panel resonance. MDF on the other hand has particle orientation in all directions and bonded with glue so it is less prone to resonance.
Cost is also another factor and large sheets of hardwood costs heaps, more than veneer does. Recently I've built hall table for my house and I had to investigate the prices of many timbers to come to the final decision and hardwood in sheet form is real expensive. I may suggest for loudspeaker enclosures, pre-veneered MDF is available which may be another attractive option for people who want the veneer, but arn't prepared to apply it themselves. Pre-veneered MDF is also cheaper than sheet hardwoods. Of course, it depends what type of hardwood is used. But I've found that the majority are still very expensive.
And the other issue at play is that of weight. Hardwood weighs heaps, a lot more than MDF. That makes it unattractive particularly for larger enclosures.
> Also, you say it has resonance problems that need to
> be "fixed", so what wrong with that? Bracing MDF is fixing a
> problem, certainly _that's_ acceptable, yes?
The point is that hardwoods are more prone to panel resonance than MDF regardless of bracing. Bracing still needs to be used on both materials to stiffen the enclosure so that its out of the range where it can be excited. But the properties of MDF still makes it less prone to panel resonance either way.
[regarding ron's comments]
Certainly, there are numerous musical instruments which rely on resonances to produce the desired note or tone. But it's the loudspeakers job to reproduce it, and not cabinet resonance. If it doesn't sound natural, then it's not up to the cabinet to flex at exactly the right frequency to "make up" for it. Panel resonance will appear as chaotic behaviour in the response, much like cone breakup modes. It's certainly something we don't want, so one can look at it carefully and minimize them from analysis. Typically its rather unpredictable too. But if you want the loudspeaker to faithfully reproduce the musical intrument, then it should be designed to do just that - but panel resonances certainly cannot be viewed as an option to "assit" the driver in whats taking place. Panel resonance is just that, chaotic behaviour, much like a kid behind the wheel of a car with no license. It's "all over the place".
I think I've made it pretty clear why panel resonance is not a good thing, and I've been quite adamant about it. There's no way that panel resonances can be "fiddled" with to make a speaker sound "just right". It's simply not what panel resonances do. Onto the topic of hardwood I think its pretty clear why MDF or plywood should be preferanced first. If one does want to employ a hardwood, then I'd suggest to approach it very carefully and ensure that your making the right selection. But really its counterproductive because other materials are much more suited and cost less too. And if veneer is posing a problem, then pre-veneered MDF can be used instead, or a cabinet maker or somebody with a "better hand" can do the job for you instead.
Adrian
Adrian-
I agree with your concerns about using hardwood panels for cabinets, and am happy this hasn't turned into an argument. My interest is in using _any_ appropriate materials to construct not only great sounding cabs, but attractive ones as well.
As you've noted, when selecting materials for your hall table, pre-veneered MDF wasn't top of your list. My guess is, you wanted to build something resembling fine furniture....well, that's what I want to do as well. I see the aesthetic difference between a veneered table and a solid wood one similarly applicable to speaker cabinets.
This is what I would like this thread to explore, and I believe where it began.
And all-
Using hardwood has it's particular problems and limitations, but it may have advantages. Let's explore them.
One method to eliminate that unattractive and telltale veneer edge joint is to use a solid wood substrate at the corner and rout the veneer back to expose a roundover or other shaped nose. This technique might lend itself to a laminated wood/MDF double thick baffle rather than the side panel, where movement of the wood would be lessened by it's size.
Another design I've been toying with is the endpiece over the sock-covered box idea. Here you make a box of MDF and cover it with fabric using draw strings to pull it tight on opposing sides. Then attach finished wood panels covering the string sides using push-in connectors. This is a very quick and neat finish for a center channel speaker.
I'm imagining this could be expanded to a large and long side panel that could become (or attach to) the stands. This not only would make stands for bookshelf sized speakers, but might lend itself to open ended BI-pole TL's. Finishing four boards and their edges is very easy with common woodworking tools, and the possibilities for shapes is endless.
The attachment could be keyholes routed in either panel or plug covered bolts.
Whadduyathink?
I agree with your concerns about using hardwood panels for cabinets, and am happy this hasn't turned into an argument. My interest is in using _any_ appropriate materials to construct not only great sounding cabs, but attractive ones as well.
As you've noted, when selecting materials for your hall table, pre-veneered MDF wasn't top of your list. My guess is, you wanted to build something resembling fine furniture....well, that's what I want to do as well. I see the aesthetic difference between a veneered table and a solid wood one similarly applicable to speaker cabinets.
This is what I would like this thread to explore, and I believe where it began.
And all-
Using hardwood has it's particular problems and limitations, but it may have advantages. Let's explore them.
One method to eliminate that unattractive and telltale veneer edge joint is to use a solid wood substrate at the corner and rout the veneer back to expose a roundover or other shaped nose. This technique might lend itself to a laminated wood/MDF double thick baffle rather than the side panel, where movement of the wood would be lessened by it's size.
Another design I've been toying with is the endpiece over the sock-covered box idea. Here you make a box of MDF and cover it with fabric using draw strings to pull it tight on opposing sides. Then attach finished wood panels covering the string sides using push-in connectors. This is a very quick and neat finish for a center channel speaker.
I'm imagining this could be expanded to a large and long side panel that could become (or attach to) the stands. This not only would make stands for bookshelf sized speakers, but might lend itself to open ended BI-pole TL's. Finishing four boards and their edges is very easy with common woodworking tools, and the possibilities for shapes is endless.
The attachment could be keyholes routed in either panel or plug covered bolts.
Whadduyathink?
Loudspeakers Are A Subjective Part Of Any System............
Hi Adrian,
I agree with most of what you say, however.............
Like I said much earlier, unless you build a cabinet with panels less than 3" thick you will have to live with some resonances.
We all know that this is expensive, impractical, seldom commercially done etc, so that means in practical terms most of us have to live with panel resonances of some degree.
The key is to choose materials and dimensions to achieve a musical set of resonances, and this is part of what characterises well regarded loudspeakers.
Sure this is a trial and error process, and built on experience as is the violin maker's art.
A badly built violin (or guitar) will never tune up to sounding musically 'right', and this applies to loudspeaker cabinets also, despite endless tweaking like mounting spikes, placement etc.
I have heard very heavy/dead/thick/dense MDF speakers with extremely high quality drivers and that were not musical.
Chipboard as thick as you like is better to my ear, and plywood better again.
Real wood has a different character, and very much dependant on the type of wood used - some woods sound more musical than others.
This is all subjective of course.
In my experience, just as an enclosure can be too lively, too dead can happen too.
Also, the panel material used imparts a sonic signature, and the signature of an MDF only cabinet does not usually please my ears.
The beehive cabinets that I mentioned earlier in this thread with thick chipboard front and rear panels really did sound goodly musical, and a whole bunch of party goers will testify to that.
Eric.
Hi Adrian,
I agree with most of what you say, however.............
Like I said much earlier, unless you build a cabinet with panels less than 3" thick you will have to live with some resonances.
We all know that this is expensive, impractical, seldom commercially done etc, so that means in practical terms most of us have to live with panel resonances of some degree.
The key is to choose materials and dimensions to achieve a musical set of resonances, and this is part of what characterises well regarded loudspeakers.
Sure this is a trial and error process, and built on experience as is the violin maker's art.
A badly built violin (or guitar) will never tune up to sounding musically 'right', and this applies to loudspeaker cabinets also, despite endless tweaking like mounting spikes, placement etc.
I have heard very heavy/dead/thick/dense MDF speakers with extremely high quality drivers and that were not musical.
Chipboard as thick as you like is better to my ear, and plywood better again.
Real wood has a different character, and very much dependant on the type of wood used - some woods sound more musical than others.
This is all subjective of course.
In my experience, just as an enclosure can be too lively, too dead can happen too.
Also, the panel material used imparts a sonic signature, and the signature of an MDF only cabinet does not usually please my ears.
The beehive cabinets that I mentioned earlier in this thread with thick chipboard front and rear panels really did sound goodly musical, and a whole bunch of party goers will testify to that.
Eric.
There is a another similar argument going on with regard
to flute construction, with some scientists insisting that
a flute made of "inert" material, such as concrete or stone
will sound exactly like one of metal.
Meanwhile, flautists (sp?) prize silver as the material of choice.
to flute construction, with some scientists insisting that
a flute made of "inert" material, such as concrete or stone
will sound exactly like one of metal.
Meanwhile, flautists (sp?) prize silver as the material of choice.
Metal vs. wood
It can be said that wind instruments are merely transmission lines for the tone generating mouthpieces. The Bose Waveguide is just another kazoo...
In any case, the scientists are mistaken and may not have the necessary tools to measure the difference.
Case in point: Having played alto sax in high school, I can report that there is a huge difference in "timbre" created by using different mouthpieces. The usual material for these is an ultra-hard high density plasticized rubber and the option is for metal with a chrome over-coat. I don't know what type of metal, maybe brass. In any case, many current jazz sax players use metal mouthpieces to sound more "brassy" like cornets. The orchestral players usually look for a smoother sound and end up choosing the rubber ones.
Even the choice of reed makes difference. I personally used a plastic one because it was unique and didn't require any prep time. The reed clamp makes a difference and I used a leather one (instead of the typical metal clamp) because it sounded smoother and more "romantic."
So, it seems that even with very small acoustic chambers, the material and it's damping characteristics play a part. The leather clamp damped the vibrations of the reed enough for a noticeable smoothness. The metal mouthpieces were "brighter" but I don't know why... maybe due to higher reflectivity.
I have seen quite a number of flutes with wooden mouthpieces, even though the barrel and keys were silver. And, I've seen ultra custom instruments that use a variety of things in combination - metal connecting rods, special pads with weird material under the leather, hardwood mouthpieces and even adhesive damper strips in various locations.
🙂ensen
It can be said that wind instruments are merely transmission lines for the tone generating mouthpieces. The Bose Waveguide is just another kazoo...
In any case, the scientists are mistaken and may not have the necessary tools to measure the difference.
Case in point: Having played alto sax in high school, I can report that there is a huge difference in "timbre" created by using different mouthpieces. The usual material for these is an ultra-hard high density plasticized rubber and the option is for metal with a chrome over-coat. I don't know what type of metal, maybe brass. In any case, many current jazz sax players use metal mouthpieces to sound more "brassy" like cornets. The orchestral players usually look for a smoother sound and end up choosing the rubber ones.
Even the choice of reed makes difference. I personally used a plastic one because it was unique and didn't require any prep time. The reed clamp makes a difference and I used a leather one (instead of the typical metal clamp) because it sounded smoother and more "romantic."
So, it seems that even with very small acoustic chambers, the material and it's damping characteristics play a part. The leather clamp damped the vibrations of the reed enough for a noticeable smoothness. The metal mouthpieces were "brighter" but I don't know why... maybe due to higher reflectivity.
I have seen quite a number of flutes with wooden mouthpieces, even though the barrel and keys were silver. And, I've seen ultra custom instruments that use a variety of things in combination - metal connecting rods, special pads with weird material under the leather, hardwood mouthpieces and even adhesive damper strips in various locations.
🙂ensen
Nelson Pass said:
It's a real stretch to call it a similar argument - a flute is a musical instrument, a speaker is not.
Is it live or is it Memorex?
I will take the bait, Bill.
A speaker is a musical instrument and a musical instrument is a speaker. My mouth is a musical instrument as are my vocal chords. Whether I take the kinetic energy of air moved by my diaphragm and modulate it with a waveguide or play a recording of such out of a PA system, I have created music...well, at least I've made some noise. You have to agree that a synthesizer is considered a musical instrument. I would add that it would just be a lump of silicon and plastic unless it can also transduce the electrical energy into sound that reaches my (or your) ear. Now I'm guessing you will counter with: but the speaker is only part of the whole instrument, not the instrument. That's like saying a tuba without the mouthpiece (tone generator) is not an instrument. Of course, it is, just incomplete. A speaker is a musical instrument and if we use that definition we can apply techniques used in other more "traditional" instruments.
🙂ensen.
I will take the bait, Bill.
A speaker is a musical instrument and a musical instrument is a speaker. My mouth is a musical instrument as are my vocal chords. Whether I take the kinetic energy of air moved by my diaphragm and modulate it with a waveguide or play a recording of such out of a PA system, I have created music...well, at least I've made some noise. You have to agree that a synthesizer is considered a musical instrument. I would add that it would just be a lump of silicon and plastic unless it can also transduce the electrical energy into sound that reaches my (or your) ear. Now I'm guessing you will counter with: but the speaker is only part of the whole instrument, not the instrument. That's like saying a tuba without the mouthpiece (tone generator) is not an instrument. Of course, it is, just incomplete. A speaker is a musical instrument and if we use that definition we can apply techniques used in other more "traditional" instruments.
🙂ensen.
Hi guys!
[regarding x. onasis comments]
> As you've noted, when selecting materials for your hall table,
> pre-veneered MDF wasn't top of your list. My guess is, you
> wanted to build something resembling fine furniture....well,
> that's what I want to do as well. I see the aesthetic difference
> between a veneered table and a solid wood one similarly
> applicable to speaker cabinets.
Actually the reason I didn't use MDF was because I didn't purchase sheet form hardwood. The hall table was made from Jarrah and Western Red Cedar. I had access to an entire wood-workshop for this, which includes a huge variety of tools and machines to make the job 1000 times easier than building it at home with a couple of powersaws. What I actually had done for the tabletop and the bottom supporting piece (because it had two draws as well), was use "planks" of Jarrah - they were about 12cm wide, by the length of my table (cut to size). It was also raw Jarrah, not dressed, which costs more. When its raw it means its like its been cut from a tree sort of - it looks like crap with lots of sharp bits that can give you splinters in your hands. The workshop has a thicknesser machine, which means that I could make it "dressed" myself - that is, it cuts off the outside few mm that is bad until it gets to the real wood. The tabletop was about 55cm deep, so I needed a few of these 12cm wide pieces to make that up. I then used the thicknesser machine to ensure that not only its dressed, but all the pieces were 30mm thick.
Ok. So thats the pieces needed for the table top. 55/12=4.83, so I needed five of the 12cm wide pieces to make up the 55cm depth of the table, except the fifth piece was cut so that its 7cm wide (12+12+12+12+7=55cm). In length it was about 1.2 meters or so, I don't have the worksheet with me. So now I got a stack of planks which are dressed. I used biscuit joints and PVA glue to attach them togethor while clamped. Once dry, thats the tabletop! But there's still little "valleys"in the wood where the planks meet up - so hours and hours of time with a belt sander was used to first get rid of those valleys as best as possible, and then a process of using sandpaper by hand working progressivly from 40grit up to 220grit was used to get the surface exactly smooth. Then... thats the completed tabletop.
But all this means I payed jack-all for the tabletop. And I got the non-dressed Jarrah planks for dirt cheap through a discount deal that the workshop gets, becasue - its a workshop, and I know the guy there. I saved heaps by buying raw hardwood and then dressing it myself. And I saved even more because it wasn't in sheet form, rather it was planks. Further, I got the discount deal through the workshop. All this does mean however that its a lot more work to make the tabletop - but I had the facilities and the ability to use all the machinary there, so I could make the table out of solid hardwood at a really cheap cost.
> One method to eliminate that unattractive and telltale veneer
> edge joint is to use a solid wood substrate at the corner and
> rout the veneer back to expose a roundover or other shaped
> nose.
I guess this is dependant on the ability of the person who is applying the veneer. I think your referring to how veneer can "peel back" at the ends? And how it can peel off or show through where the veneer is on the MDF edge? If so, thats typcially the problem with the glue your using. Contact cement is a poor adhesive for this. Proper veneer glue should be used, such as that from www.veneersystems.com or another commercial supplier. Then the idea is to get the surface of the MDF extremely smooth using a stroke or thickness sander (orbit sanders are typically poor for this). And then use 80grit sandpaper, and work your way up. But be light on all this so as to not remove thickness of the wood, but still get it smooth to remove all the bumps.
Unfortunately I'm not to sure I understand what your last tip was on this. Can you explain it again for me?
[regarding mrfeedback's comments]
> Like I said much earlier, unless you build a cabinet with panels
> less than 3" thick you will have to live with some resonances.
> We all know that this is expensive, impractical, seldom
> commercially done etc, so that means in practical terms most of
> us have to live with panel resonances of some degree.
True. There's going to be resonances for any material used. The point is MDF is less prone to panel resonance than hardwood for reasons I've already described. Furthermore, thats why people can brace each panel to stiffen it up so that panel resonances are shifted to a higher frequency where they arn't as easily excited. If a subwoofer is going to be crossed at 100Hz, then a panel resonance up at 1KHz is going to be far more difficult to excite as the crossover has removed energy from this area. Or you could have a cabinet with a midrange/midbass driver used up to maybe 1.2KHz or so, so cabinet resonances at 3KHz will be less able to be excited because there is little energy in this area because of the crossover.
> The key is to choose materials and dimensions to achieve a
> musical set of resonances, and this is part of what
> characterises well regarded loudspeakers.
Musical resonances?! Haha! Sorry, I just had to say that. I'm not sure I can put this any other way, but the answer is no. Resonances are much like the behaviour of bad breakup modes, port resonances, etc. It's unwanted behaviour that creates spikes in the response set to the resonant frequency of the panel and with Q determined by the amount of damping. A flat response is needed otherwise your getting further and further away from whats been recorded on the disk.
> Sure this is a trial and error process, and built on experience as
> is the violin maker's art.
> A badly built violin (or guitar) will never tune up to sounding
> musically 'right', and this applies to loudspeaker cabinets also,
> despite endless tweaking like mounting spikes, placement etc.
A violen is a musical intrument, and is certainly tweaked up to produce the sound that the violen manufacture wants. But what he ends up with is just what he wants. If it wasn't, then he would design it differently.
But panel resonance in loudspeakers is not what we want. If we intentionally make panel resonance excitable and audible then the frequency response is not flat, and we don't hear an accurate representation of the recording.
So provided high quality parts are used, and its implementation is good too, then that's whats going to be the best for us.
What would happen when we play a recording like a boring speech by Mr Bush on the Iraq war? Or something else that has no wood-type musical instruments, such as a movie. Or perhaps music that has none of these instruments in it. Those spikes are still going to be there, and those are getting you further and further away from whats been recorded. There are lots of these "little resonators" in any physical system, so we can look at them reductionistically and analyze each one. Thats why people use bracing and materials like plywood or MDF to build loudspeakers. A proper implementation of all systematic criteria using these materials for the cabinets does result in a great sounding loudspeaker.
BTW: It's the loudspeakers job to reproduce an accurate and faithful representation of whats on the disk, and not to add any artifacts of its own to the music. If one really does like the idea of chaotic resonances in the system, then prehaps they are better off purchasing a parametric equalizer where they can add as many resonant-like behaviour as they wish.
Adrian
[regarding x. onasis comments]
> As you've noted, when selecting materials for your hall table,
> pre-veneered MDF wasn't top of your list. My guess is, you
> wanted to build something resembling fine furniture....well,
> that's what I want to do as well. I see the aesthetic difference
> between a veneered table and a solid wood one similarly
> applicable to speaker cabinets.
Actually the reason I didn't use MDF was because I didn't purchase sheet form hardwood. The hall table was made from Jarrah and Western Red Cedar. I had access to an entire wood-workshop for this, which includes a huge variety of tools and machines to make the job 1000 times easier than building it at home with a couple of powersaws. What I actually had done for the tabletop and the bottom supporting piece (because it had two draws as well), was use "planks" of Jarrah - they were about 12cm wide, by the length of my table (cut to size). It was also raw Jarrah, not dressed, which costs more. When its raw it means its like its been cut from a tree sort of - it looks like crap with lots of sharp bits that can give you splinters in your hands. The workshop has a thicknesser machine, which means that I could make it "dressed" myself - that is, it cuts off the outside few mm that is bad until it gets to the real wood. The tabletop was about 55cm deep, so I needed a few of these 12cm wide pieces to make that up. I then used the thicknesser machine to ensure that not only its dressed, but all the pieces were 30mm thick.
Ok. So thats the pieces needed for the table top. 55/12=4.83, so I needed five of the 12cm wide pieces to make up the 55cm depth of the table, except the fifth piece was cut so that its 7cm wide (12+12+12+12+7=55cm). In length it was about 1.2 meters or so, I don't have the worksheet with me. So now I got a stack of planks which are dressed. I used biscuit joints and PVA glue to attach them togethor while clamped. Once dry, thats the tabletop! But there's still little "valleys"in the wood where the planks meet up - so hours and hours of time with a belt sander was used to first get rid of those valleys as best as possible, and then a process of using sandpaper by hand working progressivly from 40grit up to 220grit was used to get the surface exactly smooth. Then... thats the completed tabletop.
But all this means I payed jack-all for the tabletop. And I got the non-dressed Jarrah planks for dirt cheap through a discount deal that the workshop gets, becasue - its a workshop, and I know the guy there. I saved heaps by buying raw hardwood and then dressing it myself. And I saved even more because it wasn't in sheet form, rather it was planks. Further, I got the discount deal through the workshop. All this does mean however that its a lot more work to make the tabletop - but I had the facilities and the ability to use all the machinary there, so I could make the table out of solid hardwood at a really cheap cost.
> One method to eliminate that unattractive and telltale veneer
> edge joint is to use a solid wood substrate at the corner and
> rout the veneer back to expose a roundover or other shaped
> nose.
I guess this is dependant on the ability of the person who is applying the veneer. I think your referring to how veneer can "peel back" at the ends? And how it can peel off or show through where the veneer is on the MDF edge? If so, thats typcially the problem with the glue your using. Contact cement is a poor adhesive for this. Proper veneer glue should be used, such as that from www.veneersystems.com or another commercial supplier. Then the idea is to get the surface of the MDF extremely smooth using a stroke or thickness sander (orbit sanders are typically poor for this). And then use 80grit sandpaper, and work your way up. But be light on all this so as to not remove thickness of the wood, but still get it smooth to remove all the bumps.
Unfortunately I'm not to sure I understand what your last tip was on this. Can you explain it again for me?
[regarding mrfeedback's comments]
> Like I said much earlier, unless you build a cabinet with panels
> less than 3" thick you will have to live with some resonances.
> We all know that this is expensive, impractical, seldom
> commercially done etc, so that means in practical terms most of
> us have to live with panel resonances of some degree.
True. There's going to be resonances for any material used. The point is MDF is less prone to panel resonance than hardwood for reasons I've already described. Furthermore, thats why people can brace each panel to stiffen it up so that panel resonances are shifted to a higher frequency where they arn't as easily excited. If a subwoofer is going to be crossed at 100Hz, then a panel resonance up at 1KHz is going to be far more difficult to excite as the crossover has removed energy from this area. Or you could have a cabinet with a midrange/midbass driver used up to maybe 1.2KHz or so, so cabinet resonances at 3KHz will be less able to be excited because there is little energy in this area because of the crossover.
> The key is to choose materials and dimensions to achieve a
> musical set of resonances, and this is part of what
> characterises well regarded loudspeakers.
Musical resonances?! Haha! Sorry, I just had to say that. I'm not sure I can put this any other way, but the answer is no. Resonances are much like the behaviour of bad breakup modes, port resonances, etc. It's unwanted behaviour that creates spikes in the response set to the resonant frequency of the panel and with Q determined by the amount of damping. A flat response is needed otherwise your getting further and further away from whats been recorded on the disk.
> Sure this is a trial and error process, and built on experience as
> is the violin maker's art.
> A badly built violin (or guitar) will never tune up to sounding
> musically 'right', and this applies to loudspeaker cabinets also,
> despite endless tweaking like mounting spikes, placement etc.
A violen is a musical intrument, and is certainly tweaked up to produce the sound that the violen manufacture wants. But what he ends up with is just what he wants. If it wasn't, then he would design it differently.
But panel resonance in loudspeakers is not what we want. If we intentionally make panel resonance excitable and audible then the frequency response is not flat, and we don't hear an accurate representation of the recording.
So provided high quality parts are used, and its implementation is good too, then that's whats going to be the best for us.
What would happen when we play a recording like a boring speech by Mr Bush on the Iraq war? Or something else that has no wood-type musical instruments, such as a movie. Or perhaps music that has none of these instruments in it. Those spikes are still going to be there, and those are getting you further and further away from whats been recorded. There are lots of these "little resonators" in any physical system, so we can look at them reductionistically and analyze each one. Thats why people use bracing and materials like plywood or MDF to build loudspeakers. A proper implementation of all systematic criteria using these materials for the cabinets does result in a great sounding loudspeaker.
BTW: It's the loudspeakers job to reproduce an accurate and faithful representation of whats on the disk, and not to add any artifacts of its own to the music. If one really does like the idea of chaotic resonances in the system, then prehaps they are better off purchasing a parametric equalizer where they can add as many resonant-like behaviour as they wish.
Adrian
Adrian,
Woodworking is my most favorite hobby, second to audio I'm afraid. I have been doing it for a while and agree that contact cement is a poor choice for veneering. The best choice would be plastic resin glue. If you had access to a vacuum press good old yellow glue would be a good choice. If anyone cares my woodworking website is www.woodworkersweb.com and my shop pictures can be seen by clicking on "Guy and Micheles Woodshop". I have been veneering for years and if anyone has had trouble with veneer peeling back it is probably because of using contact cement. I have used both a vacuum press with yellow glue and simple caulls with plastic resin glue and never had peel back to date. I could be be lucky also I guess.
Woodworking is my most favorite hobby, second to audio I'm afraid. I have been doing it for a while and agree that contact cement is a poor choice for veneering. The best choice would be plastic resin glue. If you had access to a vacuum press good old yellow glue would be a good choice. If anyone cares my woodworking website is www.woodworkersweb.com and my shop pictures can be seen by clicking on "Guy and Micheles Woodshop". I have been veneering for years and if anyone has had trouble with veneer peeling back it is probably because of using contact cement. I have used both a vacuum press with yellow glue and simple caulls with plastic resin glue and never had peel back to date. I could be be lucky also I guess.
Adrian,
I think you missed this bit - "Like I said much earlier, unless you build a cabinet with panels less than 3" thick you will have to live with some resonances.
We all know that this is expensive, impractical, seldom commercially done etc, so that means in practical terms most of us have to live with panel resonances of some degree.
Eric.
I think you missed this bit - "Like I said much earlier, unless you build a cabinet with panels less than 3" thick you will have to live with some resonances.
We all know that this is expensive, impractical, seldom commercially done etc, so that means in practical terms most of us have to live with panel resonances of some degree.
Eric.
Re: Is it live or is it Memorex?
I'm not dangling any bait. And I certainly wouldn't counter with the idea that the speaker is PART
of an/the instrument because it isn't.
I do like your bringing up a synthesizer though because an enclosure, unless dead as dead can be,
can act very much like an "event triggered synthesizer." Now, if you want one of these in your system,
that's OK with me. Personally, I don't want a speaker system that burps.
What rankles me about some of the asides in this thread is the suggestion that
flaws ought to be found desirable by all.
purplepeople said:
I'm not dangling any bait. And I certainly wouldn't counter with the idea that the speaker is PART
of an/the instrument because it isn't.
I do like your bringing up a synthesizer though because an enclosure, unless dead as dead can be,
can act very much like an "event triggered synthesizer." Now, if you want one of these in your system,
that's OK with me. Personally, I don't want a speaker system that burps.
What rankles me about some of the asides in this thread is the suggestion that
flaws ought to be found desirable by all.
Hi Guy,
Nice looking shop. Makes me think the next person I hire should be named something like "Michele", the local farm boys work hard and are willing to learn, but they don't clean like that! She'd have a title in a hurry.
Good job with your table Adrian-
Yes, a good shop can make things easier, and "cheap"? Maybe you can be converted. We'll work on the resonance thing later, I know your knowlege will prove invaluable.
When setting up a shop to work with hardwoods, a table saw and jointer are the first necessities, but museums are filled with fine furniture made with hand tools. Let's not forget the (original) Mother of Invention (or the late one for that matter)
In my neck of the woods we refer to this as a planer. A jointer is a planer of sorts, but rather than planing to a set thickness, it uses flat infeed and outfeed tables to make boards flat. To really get boards ready for piano-like flatness before the glueup, surface-joint each one before planing to thickness, then joint one edge straight and square to the face. Rip the board, cutting parallel to the jointed edge, then joint the last edge. This will give you boards square and flat on each face.
In an earlier post I mentioned a "finger" or "glue-joint" style of router (or shaper) bit, that can be used to make stronger edge joints for panels, but for most small projects, a simple butt joint will be strong enough. Another method beside plates (or biscuits) for adding strength and lining up boards for panels is a spline joint, where you cut a groove in each board edge and insert a slat of wood. A dado blade works great, but a couple passes on a table saw will do.
Some of us have access to large planers (even four-sided) and thickness sanders that we can run large glued up panels through, and I highly advise seeking those shops out. I never turn away someone who needs help. (I love DIY'ers, they tend to have appreciation for what I do.)
When you have to flatten a panel by hand, (getting rid of "the little valleys") the surest method is called "cross-hatching." This is an age old method for flattening single boards or glued up panels. Use the longest hand plane you've got, sharpen it up, and cut diagonally across the whole surface of the panel, evenly, and in both directions, until the surface is almost flat, then plane and sand in the direction of the grain. By taking material off in this way, you'll be knocking down the high spots uniformly. I know it's hard at first to get used to cutting wood across the grain, but trust me, it works.
This method will work with hand held belt sanders as well, but the ease of flattening is limited to the size of the flat part of the sander's bottom plate (the platen), it will follow the hills and valleys of the panel more than a longer plane. I've found that using very course grit belts, moving quickly, and cross hatching 2 or 3 times is required, but it'll get the job done.
Not really. I'm referring to how you can just tell it's veneer. The edge gives it away, the difference in grain, the limited possibilities for treatments of the edges.... I'm not saying a good veneer job is bad, I just want to do better. I really like the look of some round-sided cabs, and nothing easy will finish it better than veneer. Actually, a couple projects on my bench right now will be rounded cabs. But aesthetically, it's not everyone's cup of tea.
Are you referring to the snap-on end panels, or the keyhole fastening system? Since no one has commented, was this difficult to understand? Anyone?
Nice looking shop. Makes me think the next person I hire should be named something like "Michele", the local farm boys work hard and are willing to learn, but they don't clean like that! She'd have a title in a hurry.
Good job with your table Adrian-
Yes, a good shop can make things easier, and "cheap"? Maybe you can be converted. We'll work on the resonance thing later, I know your knowlege will prove invaluable.
When setting up a shop to work with hardwoods, a table saw and jointer are the first necessities, but museums are filled with fine furniture made with hand tools. Let's not forget the (original) Mother of Invention (or the late one for that matter)
In my neck of the woods we refer to this as a planer. A jointer is a planer of sorts, but rather than planing to a set thickness, it uses flat infeed and outfeed tables to make boards flat. To really get boards ready for piano-like flatness before the glueup, surface-joint each one before planing to thickness, then joint one edge straight and square to the face. Rip the board, cutting parallel to the jointed edge, then joint the last edge. This will give you boards square and flat on each face.
In an earlier post I mentioned a "finger" or "glue-joint" style of router (or shaper) bit, that can be used to make stronger edge joints for panels, but for most small projects, a simple butt joint will be strong enough. Another method beside plates (or biscuits) for adding strength and lining up boards for panels is a spline joint, where you cut a groove in each board edge and insert a slat of wood. A dado blade works great, but a couple passes on a table saw will do.
Some of us have access to large planers (even four-sided) and thickness sanders that we can run large glued up panels through, and I highly advise seeking those shops out. I never turn away someone who needs help. (I love DIY'ers, they tend to have appreciation for what I do.)
When you have to flatten a panel by hand, (getting rid of "the little valleys") the surest method is called "cross-hatching." This is an age old method for flattening single boards or glued up panels. Use the longest hand plane you've got, sharpen it up, and cut diagonally across the whole surface of the panel, evenly, and in both directions, until the surface is almost flat, then plane and sand in the direction of the grain. By taking material off in this way, you'll be knocking down the high spots uniformly. I know it's hard at first to get used to cutting wood across the grain, but trust me, it works.
This method will work with hand held belt sanders as well, but the ease of flattening is limited to the size of the flat part of the sander's bottom plate (the platen), it will follow the hills and valleys of the panel more than a longer plane. I've found that using very course grit belts, moving quickly, and cross hatching 2 or 3 times is required, but it'll get the job done.
Not really. I'm referring to how you can just tell it's veneer. The edge gives it away, the difference in grain, the limited possibilities for treatments of the edges.... I'm not saying a good veneer job is bad, I just want to do better. I really like the look of some round-sided cabs, and nothing easy will finish it better than veneer. Actually, a couple projects on my bench right now will be rounded cabs. But aesthetically, it's not everyone's cup of tea.
Are you referring to the snap-on end panels, or the keyhole fastening system? Since no one has commented, was this difficult to understand? Anyone?
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