Re: Re: Re: No More Re's!!
Unfortunately this statement is not true. F = ma , acceleration not displacement. The force between the voice coil and the frame is constant with frequency. The kinentic energy of the cone decreases with frequency above resonance.
If properly done this energy is all radiated as sound from the speaker.
MJL21193 said:
Unfortunately this statement is not true. F = ma , acceleration not displacement. The force between the voice coil and the frame is constant with frequency. The kinentic energy of the cone decreases with frequency above resonance.
If properly done this energy is all radiated as sound from the speaker.
Simple funny "experiment"
Hold a playing woofer in your hands, and there will be no bass
Then place it on its magnet on the floor, and suddenly there will be pounding bass
btw, if its true that lower frequencies than box plate ressonance wont exite the plates to ressonate...THEN a sub used below 50hz wont need any bracing at all
Hold a playing woofer in your hands, and there will be no bass
Then place it on its magnet on the floor, and suddenly there will be pounding bass
btw, if its true that lower frequencies than box plate ressonance wont exite the plates to ressonate...THEN a sub used below 50hz wont need any bracing at all
I do not think this has been mentioned, but here is an interesting link to add to the debate. It is written by Peter Comeau of " World-Designs ", and you can find it at, " www.speaker-parts.eu/info/ ". Peter is a highly regarded speaker designer with extensive experiance in the commercial sector ( Heybrook Mission ). Here he explains his preference of 3 core particleboard to MDF plus the qualities of Birch ply. Peter now offers DIY designs which have been published in Hi Fi World. He recommends particle board for the main enclosure covered with 4mm mdf for better finishing, and MDF for the front baffle for ease of machining. I am surprised that Dave of " Planet 10 ", has not mentioned this as he took part in the various debates on thier forum, still go and read it.
My interest in " CLD " was recently revived by watching a documentary on the deHavilland Mosquito, the ledgendry WW11 fighter bomber, which I think a lot will know was largly constructed from wood. It was known as the " wooden wonder " or " timber terror ". This was briefly debated in a thread on " Balsa Cabinets " back in Jan 2006
The fuelage and wings were constructed from a Birchply / balsa composite, namely 2mm ply skins with 9mm balsa centre. The strength of the structure allowed minimal bracing for lightness. The wings had a load capacity of 41 tons, each of which carried a 12 cylinder 1620HP engine. Then of course you had the crew, fuel, instrumentation, bomb load, plus the overall stresses and strains, and G forces, all of which shows the strength of the structure.
So perhaps we ought to take an other look at this type of panel. Using say, solid wood edging for attaching the front baffle, etc, some bracing, damping pads ( ? ), this may well be an excellant cabinet material, though obviously not off the shelf. If it is good enough for the above I think it should handle some loudspeakers
Roy
My interest in " CLD " was recently revived by watching a documentary on the deHavilland Mosquito, the ledgendry WW11 fighter bomber, which I think a lot will know was largly constructed from wood. It was known as the " wooden wonder " or " timber terror ". This was briefly debated in a thread on " Balsa Cabinets " back in Jan 2006
The fuelage and wings were constructed from a Birchply / balsa composite, namely 2mm ply skins with 9mm balsa centre. The strength of the structure allowed minimal bracing for lightness. The wings had a load capacity of 41 tons, each of which carried a 12 cylinder 1620HP engine. Then of course you had the crew, fuel, instrumentation, bomb load, plus the overall stresses and strains, and G forces, all of which shows the strength of the structure.
So perhaps we ought to take an other look at this type of panel. Using say, solid wood edging for attaching the front baffle, etc, some bracing, damping pads ( ? ), this may well be an excellant cabinet material, though obviously not off the shelf. If it is good enough for the above I think it should handle some loudspeakers
Roy
Roy Lewis said:
This is a structural sandwich, which will allows an exceptionally strong panel (resists deflection) from relatively light and weak materials.
Hollow core doors are built this way, except they use a cardboard honey comb on the inside.
We talked about this before, on the other thread (linked by Dave at the start of this one).
This method is effective, but is it less complicated than proper bracing techniques used with regular panel material?
If you could make the interior layer for the entire box in one piece and the exterior layer the same way then fill the void between with urethane foam, this would be quite dead, don't you think?
MJL21193 said:
This is what Rockport is doing for their megaBuck speaker.
http://www.stereophile.com/floorloudspeakers/644/
An externally hosted image should be here but it was not working when we last tested it.
dave
There's a more indepth discussion on construction of newer Rockport models here:
http://www.soundstage2.com/tours/rockport_200702/
Not very often I lust after commercial gear but the Rockport Altair is one of the few. They'd have to do something about those dome tweeters though.
http://www.soundstage2.com/tours/rockport_200702/
Not very often I lust after commercial gear but the Rockport Altair is one of the few. They'd have to do something about those dome tweeters though.
Re: Rockport
They are most definitely poor man's Rockport's, I borrowed heavily from their styling cue's.
Be sure you take up Buddhism, you'll need the meditation once you start spraying wood/MDF.
auplater said:And here I thought your latest creations were of devine inspiration...
That high gloss finish is my next addition to the cherry dipoles,btw...as I recently refinished the doors on my sons car with automotive clearcoat...
John L.
They are most definitely poor man's Rockport's, I borrowed heavily from their styling cue's.
Be sure you take up Buddhism, you'll need the meditation once you start spraying wood/MDF.
Re: Re: Rockport
Yes, though I was thinking aluminum, fiberglass or carbon fiber would be better.
The lengths they go to for novelty. Necessary if you expect to sell in that range though.
Your LGT's the sharpest looking thing here Ant.
Probably not nearly as bad on veneer or (in this case?) solid wood. Hard to hide in the cold, reflective solid black.
I've pretty much had it. I re-sanded a portion of the baffle on one of my mains with 2000 paper then polished. This improved the situation a bit (but not really, as I burned through near the edge, so a complete repaint is in order), but the slight texture is still there. This I can't really understand, since I sanded perfectly flat (using a block).
Even though this is the single most impressive finish of all, I'm tempted to scrap it and paint these over egg shell and say to hell with it. At least then I won't be distracted by the imperfection.
planet10 said:
Yes, though I was thinking aluminum, fiberglass or carbon fiber would be better.
The lengths they go to for novelty. Necessary if you expect to sell in that range though.
ShinOBIWAN said:
Your LGT's the sharpest looking thing here Ant.
Probably not nearly as bad on veneer or (in this case?) solid wood. Hard to hide in the cold, reflective solid black.
I've pretty much had it. I re-sanded a portion of the baffle on one of my mains with 2000 paper then polished. This improved the situation a bit (but not really, as I burned through near the edge, so a complete repaint is in order), but the slight texture is still there. This I can't really understand, since I sanded perfectly flat (using a block).
Even though this is the single most impressive finish of all, I'm tempted to scrap it and paint these over egg shell and say to hell with it. At least then I won't be distracted by the imperfection.
Re: Re: Re: Rockport
From one OCD sufferer to another, your too kind John.
Bizarre on the paint situation. It came back good for me after sanding and polishing. I do use different paint products so this is a possibility. Another is that we aren't seeing the same thing and maybe something went bad on your finish? You mentioned that you mixed some coats with differing paint systems? Any chance you could take a photo to illustrate? I'll take a similar shot of the LGT for comparison though I doubt it will tell us much since I polished the imperfections out.
If all is lost then I might have a useful tip - don't use gloss black. You know how I mentioned I'd sanded the cabinets late last year to get rid of what I think your describing. Well I only did the black portions. The baffles, which are pearl white, I didn't bother with at all and they show the same thing. Difference is that you really, really have to look to see it. With the black it just jumped out straight away so I really did have to do something about that but as far as the white goes, not worth the effort because you can't see it.
I'm sure you know this already but white has far less contrast in the reflections than black. So maybe go with a light coloured baffle. This is tough to match with veneer though, black really does go with anything, white or other light colours often don't.
MJL21193 said:Your LGT's the sharpest looking thing here Ant.
Probably not nearly as bad on veneer or (in this case?) solid wood. Hard to hide in the cold, reflective solid black.
I've pretty much had it. I re-sanded a portion of the baffle on one of my mains with 2000 paper then polished. This improved the situation a bit (but not really, as I burned through near the edge, so a complete repaint is in order), but the slight texture is still there. This I can't really understand, since I sanded perfectly flat (using a block).
Even though this is the single most impressive finish of all, I'm tempted to scrap it and paint these over egg shell and say to hell with it. At least then I won't be distracted by the imperfection.
From one OCD sufferer to another, your too kind John.
Bizarre on the paint situation. It came back good for me after sanding and polishing. I do use different paint products so this is a possibility. Another is that we aren't seeing the same thing and maybe something went bad on your finish? You mentioned that you mixed some coats with differing paint systems? Any chance you could take a photo to illustrate? I'll take a similar shot of the LGT for comparison though I doubt it will tell us much since I polished the imperfections out.
If all is lost then I might have a useful tip - don't use gloss black. You know how I mentioned I'd sanded the cabinets late last year to get rid of what I think your describing. Well I only did the black portions. The baffles, which are pearl white, I didn't bother with at all and they show the same thing. Difference is that you really, really have to look to see it. With the black it just jumped out straight away so I really did have to do something about that but as far as the white goes, not worth the effort because you can't see it.
I'm sure you know this already but white has far less contrast in the reflections than black. So maybe go with a light coloured baffle. This is tough to match with veneer though, black really does go with anything, white or other light colours often don't.
Re: Re: Re: Re: Re: No More Re's!!
John,
I think it only illustrates that you didn't quite understand Linkwitz's table.
Note that piston force remains constant, regardless of frequency. Where it changes is in dipole column, but that is only a consequence of equalization (more power dumped into the speaker to make up for the 6dB/oct dipole cancellation). More power = more acceleration = more force.
F = ma, since Sir Isaac.
Bratislav
MJL21193 said:
John,
I think it only illustrates that you didn't quite understand Linkwitz's table.
Note that piston force remains constant, regardless of frequency. Where it changes is in dipole column, but that is only a consequence of equalization (more power dumped into the speaker to make up for the 6dB/oct dipole cancellation). More power = more acceleration = more force.
F = ma, since Sir Isaac.
Bratislav
Re: Re: Re: Re: Re: Re: No More Re's!!
I did take the effort of posting the link to his site where you could read the following:
"A cone type electro-dynamic driver is primarily a generator of mechanical vibration force and heat. It sets air into motion, but the reactive force of the air has insignificant influence on its behavior. For acoustic and mechanical reasons a driver is always mounted to a baffle of some form. Thus the forces generated in the driver try to set the baffle into motion. The resulting whole body movement is usually a small fraction of the cone movement and governed by the relative masses of cone and baffle. Mms vcone = Mbaffle vbaffle. Since the cone velocity vcone decreases with increasing frequency for constant SPL, the whole body motion is usually only noticeable at low frequencies and causes an insignificant reduction in SPL."
This help?
Bratislav said:
I did take the effort of posting the link to his site where you could read the following:
"A cone type electro-dynamic driver is primarily a generator of mechanical vibration force and heat. It sets air into motion, but the reactive force of the air has insignificant influence on its behavior. For acoustic and mechanical reasons a driver is always mounted to a baffle of some form. Thus the forces generated in the driver try to set the baffle into motion. The resulting whole body movement is usually a small fraction of the cone movement and governed by the relative masses of cone and baffle. Mms vcone = Mbaffle vbaffle. Since the cone velocity vcone decreases with increasing frequency for constant SPL, the whole body motion is usually only noticeable at low frequencies and causes an insignificant reduction in SPL."
This help?
Re: Re: Re: Re: Rockport
A picture?? With MY camera????
I didn't even consider a colour change, but now that you mention it, it's got me thinking. I'm trying to picture another, lighter colour on these. The original 3A design has the red Corian baffle and black cab. Come to think of it, I'm getting sick of that veneer too.
Yes, I'm completely put off. I think there is a possibility that maybe the solvent based paint underneath out gassed through the waterbased and funked it up. Like I said, the amp case still looks pristine.
Maybe a 2K automotive topcoat would fix the problem.
ShinOBIWAN said:
A picture?? With MY camera????
I didn't even consider a colour change, but now that you mention it, it's got me thinking. I'm trying to picture another, lighter colour on these. The original 3A design has the red Corian baffle and black cab. Come to think of it, I'm getting sick of that veneer too.
Yes, I'm completely put off. I think there is a possibility that maybe the solvent based paint underneath out gassed through the waterbased and funked it up. Like I said, the amp case still looks pristine.
Maybe a 2K automotive topcoat would fix the problem.
Re: Re: Re: Re: Re: Re: Re: No More Re's!!
No it doesn't.
Please point out where does it say that force increases with decreasing frequency ? All I can see in that table is "Piston force == 6.1N" regardless of frequency.
Stop mixing velocity with acceleration, and force with energy.
MJL21193 said:
No it doesn't.
Please point out where does it say that force increases with decreasing frequency ? All I can see in that table is "Piston force == 6.1N" regardless of frequency.
Stop mixing velocity with acceleration, and force with energy.
Re: Re: Re: Re: Re: Re: Re: Re: No More Re's!!
Why not take up your argument with the man himself. I didn't write that, Linkwitz did. Without going out on a limb here, it's safe to assume that he knows what he's talking about.
Shift your eyes one inch to the right on the chart and you will see another pair of columns, labeled "kinetic energy". Here you will find values that change.
Bratislav said:
Why not take up your argument with the man himself. I didn't write that, Linkwitz did. Without going out on a limb here, it's safe to assume that he knows what he's talking about.
Shift your eyes one inch to the right on the chart and you will see another pair of columns, labeled "kinetic energy". Here you will find values that change.
Re: Re: Re: Re: Re: Re: Re: Re: Re: No More Re's!!
Gedlee is certainly correct and as Bratislav said, you've misinterpreted the chart, but thanks for the link, it provides the supporting data. The chart shows forces generated at a given sound pressure. For a monopole, that force is constant. For a dipole, it must be equalized.
Note the displacement column, the piston Xpeak. At higher frequencies, 226Hz and up, they are equal. Then look at 20Hz. For a closed box it's 27.3mm, for a dipole it's 318mm. For a given frequency, the dipole must have a huge displacement to provide equal SPL, therefore the force applied must be increased at all lower frequencies.
Energy has nothing to do with it, although the equalized dipole driver will undergo far more force variation throughout a cycle, must move faster to reach the higher Xpeak and therefore will have higher energy when producing the same SPL, so the demand on its mechanical integrity is much higher than for the monopole, aside from displacement limitations. The instantaneous value of energy (1/2 *mV^2), when velocity is at its peak (at the zero crossing) will be much higher for the dipole, since it has to reach an Xpeak far greater than that of a monopole. But note that the energy equation has nothing to do with force.
Dave
MJL21193 said:
Gedlee is certainly correct and as Bratislav said, you've misinterpreted the chart, but thanks for the link, it provides the supporting data. The chart shows forces generated at a given sound pressure. For a monopole, that force is constant. For a dipole, it must be equalized.
Note the displacement column, the piston Xpeak. At higher frequencies, 226Hz and up, they are equal. Then look at 20Hz. For a closed box it's 27.3mm, for a dipole it's 318mm. For a given frequency, the dipole must have a huge displacement to provide equal SPL, therefore the force applied must be increased at all lower frequencies.
Energy has nothing to do with it, although the equalized dipole driver will undergo far more force variation throughout a cycle, must move faster to reach the higher Xpeak and therefore will have higher energy when producing the same SPL, so the demand on its mechanical integrity is much higher than for the monopole, aside from displacement limitations. The instantaneous value of energy (1/2 *mV^2), when velocity is at its peak (at the zero crossing) will be much higher for the dipole, since it has to reach an Xpeak far greater than that of a monopole. But note that the energy equation has nothing to do with force.
Dave
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