the whole subject about transarent diaphragms isn't too far from what has been discussed here earlier:
http://members.aon.at/kinotechnik/diyaudio/diy_audio/BDMD/Introducing_BDMD.htm
If you don't like or trust my sims at the beginning - scroll down to my measurements at the end...
[/IMG]http://members.aon.at/kinotechnik/diyaudio/diy_audio/BDMD/Image12.gif[/IMG]
Michael
http://members.aon.at/kinotechnik/diyaudio/diy_audio/BDMD/Introducing_BDMD.htm
If you don't like or trust my sims at the beginning - scroll down to my measurements at the end...
An externally hosted image should be here but it was not working when we last tested it.
[/IMG]http://members.aon.at/kinotechnik/diyaudio/diy_audio/BDMD/Image12.gif[/IMG]
Michael
gedlee said:
Sorry Gedlee, but this one hit me right between the eyes.
You can change the sound of a composite 'loudspeaker' by changing the driver cone - ie. altering its degree of transparency to waves being diffracted/radiated/reflected/resonant etc. from discontinuities and enclosed spaces behind the loudspeaker.
It is also easy to listen to the sound of any baffle/cabinet by tapping newspaper when it is held loosely over the LS aperture. No matter what LS is placed in the aperture similar audible reactions will arise, and some drivers will be more 'acoustically transparent' than others.
Cheers ....... Graham.
Cabinet colouration
First of all Lynn,
Glad you found my Manger post of interest. I have posted a few more of my experiences on the "Full Range" thread under the Manger topic.
Please visit www.eltim.eu and check out their "Twaron" or Angel hair as a back wave energy converter material. I have used it to reduce the back wave of the Manger driver and it really is sonically better than all the usual suspects I have tried over the years.
To All,
On the importance of cabinet colouration I think that it is of major importance in any box design and less but still very significant importance in any minimalist cabinet i.e. open baffle, U frame, H frame and derivatives.
Here is why....
(1) Take a conventional 8 inch or 10 inch bass / mid with a dome / ribbon tweeter in a cabinet 1 meter tall 25cm wide 30cm deep.
Total Sd of drivers = approx 225cm square for the 8 inch & 305 for the 10 inch.
Total Sd of cabinet = 12,500 cm square. So the cabinet has 55 times greater surface area than the 8 inch speaker combo and 41 times the surface area of the 10 inch driver & tweeter.
So if the cabinet vibrates just one 55th or one 41st as much as the driver, the cabinet will be radiating an acoustic output equal to that of the drivers, BUT out of phase with the drivers!
This cabinet Sd to driver Sd ratio is very important and can be improved by increasing driver Sd and or reducing cabinet surface area.
Also choice of cabinet material / mass and damping can be used to increase / decrease the time delay of this "slow release" energy.
(2) How to quantify this problem?
Lets take a best case scenario and imagine a 100 watt power amp driving direct (no "electronic sponges", i.e. resistors, capacitors and inductors) into a top quality PHL 3820
10 inch driver with a great spec (way better than the usual audiophile designer names) and a highly respected sound quality. At 96dB for 1 watt @ 1 meter it is more than two or three times as sensitive than a good audiophile driver. But it is still only 2.3% efficient! (Efficiency measured using the half space method)
This means that 97.3% of your 100 watts of electrical power is being burned off as wasted voice coil heat AND time delayed cabinet resonance! Remembering energy is always conserved, you cant destroy energy only convert it to another form of energy.
So if we measure the thermal out put of the voice coil and add it to the measured acoustic output of the driver that will give us a figure of X. Now our 100 watt amplifier input minus X gives us our total figure for time delayed cabinet energy.
I have no data to hand on the thermal dissipation of voice coils (they will vary greatly from small poorly ventilated 2 inch audiophile coils up to well vented 5 or 6 inch pro driver coils) but I am guessing that there is substantial energy dissipated through vibrating cabinets.
Last thought. Play music (or test tones) into our PHL driver at 200Hz to 1,000Hz at approx 100dB SPL at 1 meter. Try and see the cone move, you cant, not even in bright light. You can feel it easily but not see it. The cone will be moving approx plus or minus 0.1mm. So our cabinet only needs to be vibrating plus or minus one 41st as much, 0.0024mm (24 one thousands of a millimetre!) to have an acoustic output equal to our driver! This cabinet acoustic output is time delayed, that's what makes this distortion so bad in my experience.
Easy cures?
Maximise driver efficiency
Maximise driver Sd to cabinet Sd.
Difficult cure?
Direct floor mount the bass, bass / mid on rigid metal stands. A pair of brass or cold cast bronze strips can be bent and tapped to accept bolts & than clamp the magnet assembly.
Brass poles with threaded ends are then screwed into heavy cast iron "footers"
Use 10mm thick Sorbothane and Neoprene gaskets around the FRONT of the drivers. REAR mount the drivers to the baffle / U frame assembly by gently push sealing together i.e. no bolts or screws to hold the drivers to the baffle, just a push fit to make the seal.
There are now no easy energy paths for the driver energy to be drawn into the cabinet! This is crucial in the low bass and lower midrange. Less so in the high frequencies as the energy involved is much lower.
This is very effective but not very stylish....! Can be made ok though if you use a "motor cycle faring" i.e. a light weight GRP baffle /U frame with a cool paint job. Remember the whole baffle / frame is now just for "aerodynamic" purposes so you can tune the dimensions with VPL, back wave absorbers / converters and even good old EQ...!
Hope this helps.
Cheers
Derek.
First of all Lynn,
Glad you found my Manger post of interest. I have posted a few more of my experiences on the "Full Range" thread under the Manger topic.
Please visit www.eltim.eu and check out their "Twaron" or Angel hair as a back wave energy converter material. I have used it to reduce the back wave of the Manger driver and it really is sonically better than all the usual suspects I have tried over the years.
To All,
On the importance of cabinet colouration I think that it is of major importance in any box design and less but still very significant importance in any minimalist cabinet i.e. open baffle, U frame, H frame and derivatives.
Here is why....
(1) Take a conventional 8 inch or 10 inch bass / mid with a dome / ribbon tweeter in a cabinet 1 meter tall 25cm wide 30cm deep.
Total Sd of drivers = approx 225cm square for the 8 inch & 305 for the 10 inch.
Total Sd of cabinet = 12,500 cm square. So the cabinet has 55 times greater surface area than the 8 inch speaker combo and 41 times the surface area of the 10 inch driver & tweeter.
So if the cabinet vibrates just one 55th or one 41st as much as the driver, the cabinet will be radiating an acoustic output equal to that of the drivers, BUT out of phase with the drivers!
This cabinet Sd to driver Sd ratio is very important and can be improved by increasing driver Sd and or reducing cabinet surface area.
Also choice of cabinet material / mass and damping can be used to increase / decrease the time delay of this "slow release" energy.
(2) How to quantify this problem?
Lets take a best case scenario and imagine a 100 watt power amp driving direct (no "electronic sponges", i.e. resistors, capacitors and inductors) into a top quality PHL 3820
10 inch driver with a great spec (way better than the usual audiophile designer names) and a highly respected sound quality. At 96dB for 1 watt @ 1 meter it is more than two or three times as sensitive than a good audiophile driver. But it is still only 2.3% efficient! (Efficiency measured using the half space method)
This means that 97.3% of your 100 watts of electrical power is being burned off as wasted voice coil heat AND time delayed cabinet resonance! Remembering energy is always conserved, you cant destroy energy only convert it to another form of energy.
So if we measure the thermal out put of the voice coil and add it to the measured acoustic output of the driver that will give us a figure of X. Now our 100 watt amplifier input minus X gives us our total figure for time delayed cabinet energy.
I have no data to hand on the thermal dissipation of voice coils (they will vary greatly from small poorly ventilated 2 inch audiophile coils up to well vented 5 or 6 inch pro driver coils) but I am guessing that there is substantial energy dissipated through vibrating cabinets.
Last thought. Play music (or test tones) into our PHL driver at 200Hz to 1,000Hz at approx 100dB SPL at 1 meter. Try and see the cone move, you cant, not even in bright light. You can feel it easily but not see it. The cone will be moving approx plus or minus 0.1mm. So our cabinet only needs to be vibrating plus or minus one 41st as much, 0.0024mm (24 one thousands of a millimetre!) to have an acoustic output equal to our driver! This cabinet acoustic output is time delayed, that's what makes this distortion so bad in my experience.
Easy cures?
Maximise driver efficiency
Maximise driver Sd to cabinet Sd.
Difficult cure?
Direct floor mount the bass, bass / mid on rigid metal stands. A pair of brass or cold cast bronze strips can be bent and tapped to accept bolts & than clamp the magnet assembly.
Brass poles with threaded ends are then screwed into heavy cast iron "footers"
Use 10mm thick Sorbothane and Neoprene gaskets around the FRONT of the drivers. REAR mount the drivers to the baffle / U frame assembly by gently push sealing together i.e. no bolts or screws to hold the drivers to the baffle, just a push fit to make the seal.
There are now no easy energy paths for the driver energy to be drawn into the cabinet! This is crucial in the low bass and lower midrange. Less so in the high frequencies as the energy involved is much lower.
This is very effective but not very stylish....! Can be made ok though if you use a "motor cycle faring" i.e. a light weight GRP baffle /U frame with a cool paint job. Remember the whole baffle / frame is now just for "aerodynamic" purposes so you can tune the dimensions with VPL, back wave absorbers / converters and even good old EQ...!
Hope this helps.
Cheers
Derek.
Derek
Your analysis is very weak. First, regrading the cabinet area thing, the modes in a cabinet have positive and negative areas associated with them which will be phase relative to the driver in complex ways. This will reduce the actual "effective" radiation area to a small fraction of the total enclosures surface area. ONLY the lowest mode of the cabinet, the pressure mode, if you will, where all the sides etc, are in phase, will have any significant radiation efficiency, the rest will be very small. But this lowest mode is easy to stiffen by cross bracing, thus reducing its amplitude to almost nil.
The low radiation efficiency of a driver INCLUDES energy to the enclosure since its energy loss is non-electrical. Thus your analysis of the thermal loses in the VC would not have anything to do with the energy getting into the enclosure. I would suspect that in terms of energy, the enclosure being much much higher impedance that the drivers cone, the energy getting into the enclousre is only going to be a small fraction of 1%. This all assumes a "decent" enclosure design of course, not some injection molded PVC one.
Your analysis is very weak. First, regrading the cabinet area thing, the modes in a cabinet have positive and negative areas associated with them which will be phase relative to the driver in complex ways. This will reduce the actual "effective" radiation area to a small fraction of the total enclosures surface area. ONLY the lowest mode of the cabinet, the pressure mode, if you will, where all the sides etc, are in phase, will have any significant radiation efficiency, the rest will be very small. But this lowest mode is easy to stiffen by cross bracing, thus reducing its amplitude to almost nil.
The low radiation efficiency of a driver INCLUDES energy to the enclosure since its energy loss is non-electrical. Thus your analysis of the thermal loses in the VC would not have anything to do with the energy getting into the enclosure. I would suspect that in terms of energy, the enclosure being much much higher impedance that the drivers cone, the energy getting into the enclousre is only going to be a small fraction of 1%. This all assumes a "decent" enclosure design of course, not some injection molded PVC one.
Arguments based only on surface area are extreme. Even if you assume the panels all move uniformly (which as Earl points out is not the case). You also need to consider the relative moving mass and the direction of acceleration resulting from force transmission. The box you postulate as having 55 time the area would also have roughly 500 to 1000 times the mass of typical 8" drivers is made from 3/4" MDF. Additionally, all cabinet vibrations must be such that the motion has a component perpendicular to the surface to radiate sound. In the worst case, if all the force applied to accelerate the cone were transfered to the cabinet and resulted in acceleration of the cabinet panels in the direction perpendicular to the surface the radiated sound from the cabinet would be about 20dB below that of the driver for your proposed cabinet. When we consider all the acceleration is not perpendicular to the surfaces things change. For example, the front baffle and rear of the cabinet could potentially accelerate in the same direction of the cone, and this acceleration would be perpendicular to the surfaces and radiate sound. But for the sides, top and bottom of a rectangular cabinet the acceleration would be parallel to the surface and there would be no resulting sound radiated from the sides and top and bottom. So now the potential cabinet radiating area is that of only the front and back, or 5000 cm^2 for an area ratio of 22. So now we are down to -27 to -33dB for the heavy or light cones, respectively. This is basically treating the cabinet as a lumped mass.
We must also consider that not all the force transmitted to the cabinet results in acceleration. The bending of the panels, the propagation of acoustic (force) waves through the carbinet walls, etc, also result in dissipation of the force transmitted to the baffle. And of course, unless the carbinet is suspended in air, the cabinet will be grounded and much of the force will be transfered to the ground as well as you note.
Basically this force transmittal issue is easily address by mass. The more difficult problem (and it really isn't that hard) is panel resonance.
We must also consider that not all the force transmitted to the cabinet results in acceleration. The bending of the panels, the propagation of acoustic (force) waves through the carbinet walls, etc, also result in dissipation of the force transmitted to the baffle. And of course, unless the carbinet is suspended in air, the cabinet will be grounded and much of the force will be transfered to the ground as well as you note.
Basically this force transmittal issue is easily address by mass. The more difficult problem (and it really isn't that hard) is panel resonance.
Cabinet energy effects
Hi Earl,
I am a big fan of your room acoustic theory, multiple subs working with the room not against it and your great work on wave guides, but I have to disagree with you on this one!
(1) Re your first paragraph :
Please expand on what you mean by "phase relative".
We have a simple energy in = energy out equation. A cabinet, braced or otherwise can not magic away energy.
Do we agree that the cabinets complex flexure and resonance uses up energy? i.e. the driver energises the cabinet and the cabinets vibrate. Or are you saying that your cabinet dissipates energy without vibrating?
All cabinet bracing, mass, damping, bolting, tensions, torques and tinsel simply raise or lower the frequencies of these vibrations and slow or speed up the time taken to stop vibrating.
Surely all output from cabinet (and voice coil heat) must be "phase relative" to the acoustic energy out put of the driver? Relative how? Good or bad? Bad if the energy is time delayed.
Are you saying that after all the complex energy paths and cabinet nodes have done their stuff this will be either beneficial or inconsequential to the driver output?
Is our goal not to create a speaker in which as much of energy input (power amp) is emitted exclusively by the driver?
Ignore low frequency loading for a moment and listen to the damage any box cabinet inflicts on a good midrange driver compared to no cabinet at all. Even putting aside the large amount of sound energy that bounces around the box and then re emerges (out of phase!) through the paper cone (they are way more acoustically transparent than the cabinet!) what do you do with " for every action there is an equal and opposite reaction" i.e. the same amount of sound energy is directed back into the cabinet as is directed out to the listener! And as its a very small room inside the box its way louder! Enter the cabinet to suck up and spit out a good chunk of that airborne energy PLUS its structurally borne energy.
Re your second paragraph :
Yes well spotted, the PHL driver efficiency is measured with the driver in a 12 litre ported (what are they thinking!) cabinet. The free air efficiency would be even lower than the 2.3% half space figure as the driver spec includes low frequency cabinet loading.
This point further enhances my side of the debate I believe.
I stand by my point that all we have here is one input and three possible outputs.
Amp in must = Voice coil heat + acoustic output of driver plus mechanical / frictional losses (cabinet & driver vibrations). My guess is that the acoustic output of the driver is third on the list with voice coil heating and cabinet resonance dominating by a mile. They MUST cause the driver is only outputting 2.3% on a good day!
Can anyone help with real driver manufacturer data on voice coil heat dissipation / efficiency?
Cheers
Derek.
Hi Earl,
I am a big fan of your room acoustic theory, multiple subs working with the room not against it and your great work on wave guides, but I have to disagree with you on this one!
(1) Re your first paragraph :
Please expand on what you mean by "phase relative".
We have a simple energy in = energy out equation. A cabinet, braced or otherwise can not magic away energy.
Do we agree that the cabinets complex flexure and resonance uses up energy? i.e. the driver energises the cabinet and the cabinets vibrate. Or are you saying that your cabinet dissipates energy without vibrating?
All cabinet bracing, mass, damping, bolting, tensions, torques and tinsel simply raise or lower the frequencies of these vibrations and slow or speed up the time taken to stop vibrating.
Surely all output from cabinet (and voice coil heat) must be "phase relative" to the acoustic energy out put of the driver? Relative how? Good or bad? Bad if the energy is time delayed.
Are you saying that after all the complex energy paths and cabinet nodes have done their stuff this will be either beneficial or inconsequential to the driver output?
Is our goal not to create a speaker in which as much of energy input (power amp) is emitted exclusively by the driver?
Ignore low frequency loading for a moment and listen to the damage any box cabinet inflicts on a good midrange driver compared to no cabinet at all. Even putting aside the large amount of sound energy that bounces around the box and then re emerges (out of phase!) through the paper cone (they are way more acoustically transparent than the cabinet!) what do you do with " for every action there is an equal and opposite reaction" i.e. the same amount of sound energy is directed back into the cabinet as is directed out to the listener! And as its a very small room inside the box its way louder! Enter the cabinet to suck up and spit out a good chunk of that airborne energy PLUS its structurally borne energy.
Re your second paragraph :
Yes well spotted, the PHL driver efficiency is measured with the driver in a 12 litre ported (what are they thinking!) cabinet. The free air efficiency would be even lower than the 2.3% half space figure as the driver spec includes low frequency cabinet loading.
This point further enhances my side of the debate I believe.
I stand by my point that all we have here is one input and three possible outputs.
Amp in must = Voice coil heat + acoustic output of driver plus mechanical / frictional losses (cabinet & driver vibrations). My guess is that the acoustic output of the driver is third on the list with voice coil heating and cabinet resonance dominating by a mile. They MUST cause the driver is only outputting 2.3% on a good day!
Can anyone help with real driver manufacturer data on voice coil heat dissipation / efficiency?
Cheers
Derek.
Re: Cabinet energy effects
It seems to me that the only things that matter here are mechanical vibrations transmitted to the enclosure, and energy transmitted to the enclosure due to the sound waves generated into the air on either side of the cone.
The former, as already expressed, will be a function of the inertial mass of the cone and air being moved. As the mass of the cone will have some effect on driver efficiency, the efficiency term could enter here. But the only thing that matters is the moving mass. I see no relevance for the other efficiency terms.
The transfer of energy via the sound waves in air, takes place post generation, so the efficiency term is already factored out for this too.
Sheldon
Overkill Audio said:
It seems to me that the only things that matter here are mechanical vibrations transmitted to the enclosure, and energy transmitted to the enclosure due to the sound waves generated into the air on either side of the cone.
The former, as already expressed, will be a function of the inertial mass of the cone and air being moved. As the mass of the cone will have some effect on driver efficiency, the efficiency term could enter here. But the only thing that matters is the moving mass. I see no relevance for the other efficiency terms.
The transfer of energy via the sound waves in air, takes place post generation, so the efficiency term is already factored out for this too.
Sheldon
Cabinet resonance
Hi John K,
Good points well made, especially the mass ratio you are right a 20 dB reduction assuming 25g 8 inch / 45 g 10 inch cone Mms compared to a 25Kg 45 Kg cabinet mass ....but!
Re your point that the baffle / back panel might move in the same direction, I would suggest the following is actually occurring.
(1) "For every action there is an equal opposite reaction" so when the cone pumps out the baffle moves back.
Then two things happen to this energy, it causes flexure / vibration in the baffle and some energy will be transmitted to adjoining surfaces.
It is the fact that this energy dissipation / transmission is time delayed that, in my opinion, negates your directional point. i.e. even if all the baffle energy was to be cleanly converted into one pistonic pulse in the same direction as the driver, it would still be out of phase.
A general observation here.
I personally don't object to tonal distortion i.e. some lumps and bumps in the frequency domain. But time smearing gives me a headache and make music sound like Hi Fi. I my be overly obsessing about time domain issues but this is where I am coming from with conventional box loading cabinets.
Its also why I have fallen in love with the Manger as you can kiss goodbye 90% of time domain issues above 300Hz or 400 Hz with an open baffle Manger. If you get the chance to play with a pair try suspending the drivers from 1mm thick stainless steel wire fixed at floor and ceiling. Go full range no crossover subs or DSP and play vocals, strings and simple stuff with NO BASS (or it gets expensive!).
The trick is to then maintain that purity from a few hundred hertz up in a full range system capable of 125dB peaks.
Earl have you ever designed a wave guide for a Manger?
I use a shallow oval WG and its fabulous, I believe you could really do something special for the Manger and you will have a few thousand ready made customers, me first!
All the best
Derek.
Hi John K,
Good points well made, especially the mass ratio you are right a 20 dB reduction assuming 25g 8 inch / 45 g 10 inch cone Mms compared to a 25Kg 45 Kg cabinet mass ....but!
Re your point that the baffle / back panel might move in the same direction, I would suggest the following is actually occurring.
(1) "For every action there is an equal opposite reaction" so when the cone pumps out the baffle moves back.
Then two things happen to this energy, it causes flexure / vibration in the baffle and some energy will be transmitted to adjoining surfaces.
It is the fact that this energy dissipation / transmission is time delayed that, in my opinion, negates your directional point. i.e. even if all the baffle energy was to be cleanly converted into one pistonic pulse in the same direction as the driver, it would still be out of phase.
A general observation here.
I personally don't object to tonal distortion i.e. some lumps and bumps in the frequency domain. But time smearing gives me a headache and make music sound like Hi Fi. I my be overly obsessing about time domain issues but this is where I am coming from with conventional box loading cabinets.
Its also why I have fallen in love with the Manger as you can kiss goodbye 90% of time domain issues above 300Hz or 400 Hz with an open baffle Manger. If you get the chance to play with a pair try suspending the drivers from 1mm thick stainless steel wire fixed at floor and ceiling. Go full range no crossover subs or DSP and play vocals, strings and simple stuff with NO BASS (or it gets expensive!).
The trick is to then maintain that purity from a few hundred hertz up in a full range system capable of 125dB peaks.
Earl have you ever designed a wave guide for a Manger?
I use a shallow oval WG and its fabulous, I believe you could really do something special for the Manger and you will have a few thousand ready made customers, me first!
All the best
Derek.
Re: Cabinet energy effects
Also discussed around here (and in an outspin thread) not so long ago:
http://members.aon.at/kinotechnik/diyaudio/diy_audio/TD/Introducing_TD.htm
http://members.aon.at/kinotechnik/diyaudio/diy_audio/TD/SPICE_modelling_TD.htm
Michael
Overkill Audio said:
Also discussed around here (and in an outspin thread) not so long ago:
http://members.aon.at/kinotechnik/diyaudio/diy_audio/TD/Introducing_TD.htm
http://members.aon.at/kinotechnik/diyaudio/diy_audio/TD/SPICE_modelling_TD.htm
Michael
Re: Cabinet energy effects
Clearly I am saying that it is inconsequential. Its there, the cabinet vibrates, it absorbs energy from the driver, all true, but inconsequential as it would all be very low in output. Worst case it could be audible, but simple techniques reduce it below significance.
Equal and opposite FORCE but clearly not energy. The energy depends on the impedance levels of the two "equal and opposite" systems and one, the cabinet, is orders of magnitude greater than the other, the freely suspended cone. So one gets a lot of energy from the force and the other gets very little.
Your guess is way off of the mark because the acoustic output from the driver would be second and driver cabinet resonance energy loss would be a fraction of the sound radiation. Your numbers just don't add up to the energy of cabinet vibration being significant. You have two paths for the force from the voice coil to go 1) into the cone and hence mostly into radiated sound and 2) into the enclosure which can be either disipated structurally (most likely) or radiated as sound energy (least likely). But the IMPEDANCE of these two paths is far far from equal and so the "current" (to use an electrical analogy) goes dominately into the cone vibration and sound output. Very little goes into the cabinet unless is it very light and flexible.
Overkill Audio said:
Clearly I am saying that it is inconsequential. Its there, the cabinet vibrates, it absorbs energy from the driver, all true, but inconsequential as it would all be very low in output. Worst case it could be audible, but simple techniques reduce it below significance.
Overkill Audio said:
Equal and opposite FORCE but clearly not energy. The energy depends on the impedance levels of the two "equal and opposite" systems and one, the cabinet, is orders of magnitude greater than the other, the freely suspended cone. So one gets a lot of energy from the force and the other gets very little.
Overkill Audio said:
Your guess is way off of the mark because the acoustic output from the driver would be second and driver cabinet resonance energy loss would be a fraction of the sound radiation. Your numbers just don't add up to the energy of cabinet vibration being significant. You have two paths for the force from the voice coil to go 1) into the cone and hence mostly into radiated sound and 2) into the enclosure which can be either disipated structurally (most likely) or radiated as sound energy (least likely). But the IMPEDANCE of these two paths is far far from equal and so the "current" (to use an electrical analogy) goes dominately into the cone vibration and sound output. Very little goes into the cabinet unless is it very light and flexible.
Re: Cabinet resonance
Derek
I can agree that delayed time energy in the impulse response is a potential problem for audibility, but I'm not sure that your view of how to achieve this matchs mine. I don't see "box" issues in the late impulse response and from what I know of the Manger it doesn't really have that good an impulse response either. I do obsess over these issues too, but only the only that have been proven to make a clear difference audibly and through measurements. Otherwise its just folklore.
Overkill Audio said:
Derek
I can agree that delayed time energy in the impulse response is a potential problem for audibility, but I'm not sure that your view of how to achieve this matchs mine. I don't see "box" issues in the late impulse response and from what I know of the Manger it doesn't really have that good an impulse response either. I do obsess over these issues too, but only the only that have been proven to make a clear difference audibly and through measurements. Otherwise its just folklore.
Re: Re: Cabinet energy effects
Hi Michael
I still think that you ought to try those noise wav files that I posted to try and quantify the effect. I've been meaning to, but never did, get back to this topic as I think that its quite important. (Although I don't see how it fits into any of the enclosure discussions here.)
mige0 said:
Hi Michael
I still think that you ought to try those noise wav files that I posted to try and quantify the effect. I've been meaning to, but never did, get back to this topic as I think that its quite important. (Although I don't see how it fits into any of the enclosure discussions here.)
Re: Re: Cabinet energy effects
Energy can be seen as to be split into action and the reaction - at least as long we are talking about the energy thats needed to accellerate the mass of the cone in its mass controlled frequency region.
There are two extremes:
If you suspend the driver freely (my imaginary example in outer space) you dump the "reaction energy" into the movement of the basket and magnet structure by moving it in the oposite direction according to the ratio of masses.
If you perfectly ground a driver to the floor, you dump the "reaction energy" into the acceleration of mother earth (again by moving it in the oposite direction according to the ratio of masses)
The case in between is that you transform part of the "reaction energy" to heat due to material kneading on its way to whatever mass that acts as counterpart.
Last note
As the "acting energy" and the "reaction energy" (wow what silly terms) is
(mass multiplied by velocity^2) / 2
- and movement / velocty is in the ratio of masses its easy to see that from an energy point of view the diaphragm benefits by large ratio of masses involved (bolt it down if you can and shake mother earth).
On the other hand - suspending the driver freely does have advantiges that outperform by far the minimal efficiency increase you get by heavily bolting it down to mother earth - my word for it.
http://members.aon.at/kinotechnik/diyaudio/diy_audio/CIC/Introducing_CIC.htm
Michael
gedlee said:
Energy can be seen as to be split into action and the reaction - at least as long we are talking about the energy thats needed to accellerate the mass of the cone in its mass controlled frequency region.
There are two extremes:
If you suspend the driver freely (my imaginary example in outer space) you dump the "reaction energy" into the movement of the basket and magnet structure by moving it in the oposite direction according to the ratio of masses.
If you perfectly ground a driver to the floor, you dump the "reaction energy" into the acceleration of mother earth (again by moving it in the oposite direction according to the ratio of masses)
The case in between is that you transform part of the "reaction energy" to heat due to material kneading on its way to whatever mass that acts as counterpart.
Last note
As the "acting energy" and the "reaction energy" (wow what silly terms) is
(mass multiplied by velocity^2) / 2
- and movement / velocty is in the ratio of masses its easy to see that from an energy point of view the diaphragm benefits by large ratio of masses involved (bolt it down if you can and shake mother earth).
On the other hand - suspending the driver freely does have advantiges that outperform by far the minimal efficiency increase you get by heavily bolting it down to mother earth - my word for it.
http://members.aon.at/kinotechnik/diyaudio/diy_audio/CIC/Introducing_CIC.htm
Michael
Re: Re: Re: Cabinet energy effects
Only very little time for my hobby right now - but thanks for your cheer up!
++++
The relevance to the topc at hand was that Overkill wanted to know about voice coil heating - I guess I have outlined all he needs to calculate whatever he wants - though its only a small part of whats coverd in my paper....
Michael
gedlee said:
Only very little time for my hobby right now - but thanks for your cheer up!
++++
The relevance to the topc at hand was that Overkill wanted to know about voice coil heating - I guess I have outlined all he needs to calculate whatever he wants - though its only a small part of whats coverd in my paper....
Michael
Cabinet resonance
Hi Earl,
We are going to have to agree to disagree on the amount of and significance of driver generated cabinet energy.
Maybe we can pick it up another time as I have a more to say....!
BUT what about Michael's Thermal compression white paper, WOW!
What are we doing wasting our time on box cabinet resonance issues (a VPL U frame negates 80% of the problem anyway, and who knows a 50Kg to 100Kg massive damped cabinet with huge effort and expense might as well!) when we have not addressed TC?
I am going to read the TC document a few times tonight and then de-frag...!
Cheers
Derek.
Hi Earl,
We are going to have to agree to disagree on the amount of and significance of driver generated cabinet energy.
Maybe we can pick it up another time as I have a more to say....!
BUT what about Michael's Thermal compression white paper, WOW!
What are we doing wasting our time on box cabinet resonance issues (a VPL U frame negates 80% of the problem anyway, and who knows a 50Kg to 100Kg massive damped cabinet with huge effort and expense might as well!) when we have not addressed TC?
I am going to read the TC document a few times tonight and then de-frag...!
Cheers
Derek.
Re: Cabinet resonance
Excuse me, but I have not been "wasting my time on box cabinet resonance" I've been ignoring it as unimportant while I address things like the thermal issues!!! Michaels paper came about mainly to address a discussion that he and I had some time ago. I have been chasing thermal modulation for years and even have measured data from several years ago comparing my designs with conventional designs for thermal modulation. This is my whole point! Box resonance problems just do not rate in my book. Polar response, thermal modulation, diffraction those are worth worrying about as they make a significant difference. Don't deal with those problems and a box made of steel and welded to the floor won't matter.
Overkill Audio said:
Excuse me, but I have not been "wasting my time on box cabinet resonance" I've been ignoring it as unimportant while I address things like the thermal issues!!! Michaels paper came about mainly to address a discussion that he and I had some time ago. I have been chasing thermal modulation for years and even have measured data from several years ago comparing my designs with conventional designs for thermal modulation. This is my whole point! Box resonance problems just do not rate in my book. Polar response, thermal modulation, diffraction those are worth worrying about as they make a significant difference. Don't deal with those problems and a box made of steel and welded to the floor won't matter.