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#1
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Speakers Then and Now
I've noticed while doing some research on speakers that the acoustic
suspension design has largely disappeared in favor of bass-reflex design. Also, the newer speakers (dynamic) are using metals or metal sandwiches instead of Kevlar or paper. And the woofer surrounds are butyl rubber instead of foam. I'd appreciate your take on all of this. Thanks. |
#2
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Speakers Then and Now
In , on
01/05/04 at 11:26 PM, "lynsam" said: I've noticed while doing some research on speakers that the acoustic suspension design has largely disappeared in favor of bass-reflex design. "Bass-reflex" has become "ported". Ported designs are more efficient. An acoustic suspension enclosure must eat the backward propagating wave, the ported design uses it. In the overall scheme of things, acoustic suspension design was introduced later than Bass-reflex. Bass-reflex was always tricky to design because the size of the port was "tuned" by hand. It was cut-and-try, swear a bit, cut-and-try, swear some more, cut-and-try, ... Now we have some math that eliminates the cut-and-try tuning. One can purchase a computer program that will design a passable speaker while you watch. There are contract engineers who will design a line of speakers for a fee. It is possible that some of the brands you looked at were designed by the same person. Also, the newer speakers (dynamic) are using metals or metal sandwiches instead of Kevlar or paper. Depends where you hang out. Many believe that speakers still need lots of improving. Some think that: Since the regular materials aren't doing the job, why not try something exotic? I had one speaker sales rep tell me that his brand used special water to make the paper pulp. To a large degree, the choice of materials is whatever is in the design engineers "bag of tricks". Many times the designer comes to this industry because of a love of audio. If the designer used fiber composits in the previous career, Kevlar is the likely choice. Another designer might be more familiar with metal sandwiches. There are a lot of copycats in the speaker design business. And the woofer surrounds are butyl rubber instead of foam. I'd appreciate your take on all of this. Thanks. That foam from the 70's has liquefied, the rubber didn't. A new cottage industry has sprung-up to replace all those old foam surrounds. ----------------------------------------------------------- spam: wordgame:123(abc):14 9 20 5 2 9 18 4 at 22 15 9 3 5 14 5 20 dot 3 15 13 (Barry Mann) [sorry about the puzzle, spammers are ruining my mailbox] ----------------------------------------------------------- |
#3
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Speakers Then and Now
In , on
01/05/04 at 11:26 PM, "lynsam" said: I've noticed while doing some research on speakers that the acoustic suspension design has largely disappeared in favor of bass-reflex design. "Bass-reflex" has become "ported". Ported designs are more efficient. An acoustic suspension enclosure must eat the backward propagating wave, the ported design uses it. In the overall scheme of things, acoustic suspension design was introduced later than Bass-reflex. Bass-reflex was always tricky to design because the size of the port was "tuned" by hand. It was cut-and-try, swear a bit, cut-and-try, swear some more, cut-and-try, ... Now we have some math that eliminates the cut-and-try tuning. One can purchase a computer program that will design a passable speaker while you watch. There are contract engineers who will design a line of speakers for a fee. It is possible that some of the brands you looked at were designed by the same person. Also, the newer speakers (dynamic) are using metals or metal sandwiches instead of Kevlar or paper. Depends where you hang out. Many believe that speakers still need lots of improving. Some think that: Since the regular materials aren't doing the job, why not try something exotic? I had one speaker sales rep tell me that his brand used special water to make the paper pulp. To a large degree, the choice of materials is whatever is in the design engineers "bag of tricks". Many times the designer comes to this industry because of a love of audio. If the designer used fiber composits in the previous career, Kevlar is the likely choice. Another designer might be more familiar with metal sandwiches. There are a lot of copycats in the speaker design business. And the woofer surrounds are butyl rubber instead of foam. I'd appreciate your take on all of this. Thanks. That foam from the 70's has liquefied, the rubber didn't. A new cottage industry has sprung-up to replace all those old foam surrounds. ----------------------------------------------------------- spam: wordgame:123(abc):14 9 20 5 2 9 18 4 at 22 15 9 3 5 14 5 20 dot 3 15 13 (Barry Mann) [sorry about the puzzle, spammers are ruining my mailbox] ----------------------------------------------------------- |
#4
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Speakers Then and Now
In , on
01/05/04 at 11:26 PM, "lynsam" said: I've noticed while doing some research on speakers that the acoustic suspension design has largely disappeared in favor of bass-reflex design. "Bass-reflex" has become "ported". Ported designs are more efficient. An acoustic suspension enclosure must eat the backward propagating wave, the ported design uses it. In the overall scheme of things, acoustic suspension design was introduced later than Bass-reflex. Bass-reflex was always tricky to design because the size of the port was "tuned" by hand. It was cut-and-try, swear a bit, cut-and-try, swear some more, cut-and-try, ... Now we have some math that eliminates the cut-and-try tuning. One can purchase a computer program that will design a passable speaker while you watch. There are contract engineers who will design a line of speakers for a fee. It is possible that some of the brands you looked at were designed by the same person. Also, the newer speakers (dynamic) are using metals or metal sandwiches instead of Kevlar or paper. Depends where you hang out. Many believe that speakers still need lots of improving. Some think that: Since the regular materials aren't doing the job, why not try something exotic? I had one speaker sales rep tell me that his brand used special water to make the paper pulp. To a large degree, the choice of materials is whatever is in the design engineers "bag of tricks". Many times the designer comes to this industry because of a love of audio. If the designer used fiber composits in the previous career, Kevlar is the likely choice. Another designer might be more familiar with metal sandwiches. There are a lot of copycats in the speaker design business. And the woofer surrounds are butyl rubber instead of foam. I'd appreciate your take on all of this. Thanks. That foam from the 70's has liquefied, the rubber didn't. A new cottage industry has sprung-up to replace all those old foam surrounds. ----------------------------------------------------------- spam: wordgame:123(abc):14 9 20 5 2 9 18 4 at 22 15 9 3 5 14 5 20 dot 3 15 13 (Barry Mann) [sorry about the puzzle, spammers are ruining my mailbox] ----------------------------------------------------------- |
#5
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Speakers Then and Now
lynsam wrote:
I've noticed while doing some research on speakers that the acoustic suspension design has largely disappeared in favor of bass-reflex design. After Thiele and Small got the math done it became a lot easier to design bass-reflex cabinets. Also, the newer speakers (dynamic) are using metals or metal sandwiches instead of Kevlar or paper. Metal is as poor as kevlar unless you are very good at making cross-overs. If you are very good at making cross-overs then something that is rigid in the pass band is attractive. And the woofer surrounds are butyl rubber instead of foam. Yes, as it was prior to foam getting intruced and because there are quite many people who will not ever purchase anything with a foam surround for some straaange reason. I'd appreciate your take on all of this. Thanks. My dkk 0.02 above. -- ******************************************* * My site is at: http://www.muyiovatki.dk * ******************************************* |
#6
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Speakers Then and Now
lynsam wrote:
I've noticed while doing some research on speakers that the acoustic suspension design has largely disappeared in favor of bass-reflex design. After Thiele and Small got the math done it became a lot easier to design bass-reflex cabinets. Also, the newer speakers (dynamic) are using metals or metal sandwiches instead of Kevlar or paper. Metal is as poor as kevlar unless you are very good at making cross-overs. If you are very good at making cross-overs then something that is rigid in the pass band is attractive. And the woofer surrounds are butyl rubber instead of foam. Yes, as it was prior to foam getting intruced and because there are quite many people who will not ever purchase anything with a foam surround for some straaange reason. I'd appreciate your take on all of this. Thanks. My dkk 0.02 above. -- ******************************************* * My site is at: http://www.muyiovatki.dk * ******************************************* |
#7
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Speakers Then and Now
lynsam wrote:
I've noticed while doing some research on speakers that the acoustic suspension design has largely disappeared in favor of bass-reflex design. After Thiele and Small got the math done it became a lot easier to design bass-reflex cabinets. Also, the newer speakers (dynamic) are using metals or metal sandwiches instead of Kevlar or paper. Metal is as poor as kevlar unless you are very good at making cross-overs. If you are very good at making cross-overs then something that is rigid in the pass band is attractive. And the woofer surrounds are butyl rubber instead of foam. Yes, as it was prior to foam getting intruced and because there are quite many people who will not ever purchase anything with a foam surround for some straaange reason. I'd appreciate your take on all of this. Thanks. My dkk 0.02 above. -- ******************************************* * My site is at: http://www.muyiovatki.dk * ******************************************* |
#8
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#9
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Speakers Then and Now
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#11
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Speakers Then and Now
On Tue, 06 Jan 2004 13:18:10 +0100, Peter Larsen
wrote: Metal is as poor as kevlar unless you are very good at making cross-overs. If you are very good at making cross-overs then something that is rigid in the pass band is attractive. The B&W Kevlar drivers are not rigid in the pass band, they are *designed* to move into bending mode. -- Stewart Pinkerton | Music is Art - Audio is Engineering |
#12
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Speakers Then and Now
On Tue, 06 Jan 2004 13:18:10 +0100, Peter Larsen
wrote: Metal is as poor as kevlar unless you are very good at making cross-overs. If you are very good at making cross-overs then something that is rigid in the pass band is attractive. The B&W Kevlar drivers are not rigid in the pass band, they are *designed* to move into bending mode. -- Stewart Pinkerton | Music is Art - Audio is Engineering |
#13
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Speakers Then and Now
On Tue, 06 Jan 2004 13:18:10 +0100, Peter Larsen
wrote: Metal is as poor as kevlar unless you are very good at making cross-overs. If you are very good at making cross-overs then something that is rigid in the pass band is attractive. The B&W Kevlar drivers are not rigid in the pass band, they are *designed* to move into bending mode. -- Stewart Pinkerton | Music is Art - Audio is Engineering |
#14
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Speakers Then and Now
Stewart Pinkerton wrote:
On Tue, 06 Jan 2004 13:18:10 +0100, Peter Larsen wrote: Metal is as poor as kevlar unless you are very good at making cross-overs. If you are very good at making cross-overs then something that is rigid in the pass band is attractive. The B&W Kevlar drivers are not rigid in the pass band, they are *designed* to move into bending mode. Yes, yes, yes, kevlar units (x) tend to have a nice smooth drastically rising response because of that well designed breakup, but eventually things do get to steep dips, the major issue is of course the rising response, they are possibly not heavy enough to remain linear when breaking up ... it would be great if somebody could explain this better. (x) those I have seen specs for, I recall - probably Seas - mentioning that they required special care in the cross-over ... the Monacor ones surely are not "exceptionally flat" by any definition of that term. Flatness of response is however a system requirement and not a unit requirement. Stewart Pinkerton | Music is Art - Audio is Engineering Kind regards Peter Larsen -- ******************************************* * My site is at: http://www.muyiovatki.dk * ******************************************* |
#15
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Speakers Then and Now
Stewart Pinkerton wrote:
On Tue, 06 Jan 2004 13:18:10 +0100, Peter Larsen wrote: Metal is as poor as kevlar unless you are very good at making cross-overs. If you are very good at making cross-overs then something that is rigid in the pass band is attractive. The B&W Kevlar drivers are not rigid in the pass band, they are *designed* to move into bending mode. Yes, yes, yes, kevlar units (x) tend to have a nice smooth drastically rising response because of that well designed breakup, but eventually things do get to steep dips, the major issue is of course the rising response, they are possibly not heavy enough to remain linear when breaking up ... it would be great if somebody could explain this better. (x) those I have seen specs for, I recall - probably Seas - mentioning that they required special care in the cross-over ... the Monacor ones surely are not "exceptionally flat" by any definition of that term. Flatness of response is however a system requirement and not a unit requirement. Stewart Pinkerton | Music is Art - Audio is Engineering Kind regards Peter Larsen -- ******************************************* * My site is at: http://www.muyiovatki.dk * ******************************************* |
#16
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Speakers Then and Now
Stewart Pinkerton wrote:
On Tue, 06 Jan 2004 13:18:10 +0100, Peter Larsen wrote: Metal is as poor as kevlar unless you are very good at making cross-overs. If you are very good at making cross-overs then something that is rigid in the pass band is attractive. The B&W Kevlar drivers are not rigid in the pass band, they are *designed* to move into bending mode. Yes, yes, yes, kevlar units (x) tend to have a nice smooth drastically rising response because of that well designed breakup, but eventually things do get to steep dips, the major issue is of course the rising response, they are possibly not heavy enough to remain linear when breaking up ... it would be great if somebody could explain this better. (x) those I have seen specs for, I recall - probably Seas - mentioning that they required special care in the cross-over ... the Monacor ones surely are not "exceptionally flat" by any definition of that term. Flatness of response is however a system requirement and not a unit requirement. Stewart Pinkerton | Music is Art - Audio is Engineering Kind regards Peter Larsen -- ******************************************* * My site is at: http://www.muyiovatki.dk * ******************************************* |
#17
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#18
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#19
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Speakers Then and Now
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#22
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Speakers Then and Now
(Svante) wrote in message om...
(Dick Pierce) wrote in message The efficiency of ANY direct-radiator system (bass reflex, ported, vented, sealed, acoustic suspension, infinite baffle) is determined by the driver. The driver's electrical resistance, its moving mass, its radiating area and its magnet system determine that efficiency, period. The enclosure, in combination with the driver, determines the system response function near the low end cutoff. I agree to your post, except for one little word; the "period" above. The efficiency is also affected by the placement of the speaker. It is doubled if it is mounted in a wall, compared to radiating in free space. Efficiency increases even more if mounted in a corner etc. OK, OK, I'm being picky and maybe that has nothing to do with the design of the speaker. ...or maybe it does? If the speaker is designed for free-field conditions, the speaker will still be radiating in half-space toward higher frequencies, and thus have a lift of +6dB. This should be compensated for. If the same speaker is mounted in the wall, the HF boost will not occur (or rather, an equally large LF boost will occur), so then no compensation is needed. So, the placement of the speaker is something that the designer of the system should consider. Actually, no, the efficiency, specifically, the ratio of total radiated acoustic power to total input electrical power does NOT change. The sound pressure level on axis MAY change, but the efficiency does not. The same power is distributed over a smaller area, and since SPL is a measure of power per unit area, the SPL changes, but the power output does not. However, strictly speaking, the efficiency varies a lot with frequency. When the motion is NOT mass-controlled, the situation is completely different. There is a specific definition for efficiency, which is very clear on the meaning, that is, the efficiency above the system cutoff but below the frequency where the wavelength is equal to the circumference of the radiator. SMall and Thiele and others are quite clear on this definition, and I defer to their definition. For example, the efficiency for the closed box peaks at the system resonance, but since the electrical impedance also does, less power is delivered to the speaker (for a given voltage) and the output is largely the same as for higher frequencies (-3dB for a butterworth design). Well below the resonance it drops by 12 dB/octave. But hardly anyone speaks about efficiency as being varying with frequency, "it is one number, period". In my opinion this adds to the confusion regarding efficiency. As the definition used in the domain is quite clear, no, it in fact removes such confusion. BTW is there a difference between "ported", "bass-reflex" and "vented"? Generally, these terms are synonymous. "Sealed" and "acoustic suspension"? Aren't they synonyms? No, indeed, they are not. While an acoustic suspension enclosure is a sealed enclosure, the converse is not necessarily true. A "sealed" enclosure can be defined broadly a number of ways, but generally refers to any enclosure where the time constant of any "leak" is MUCH longer than the time constant of the system cutoff frequency. Also, any such leak cannot contrinute at all to the total system output. Essentially, the enclosed air looks like a simple acoustical compliance. An "acoustic suspension" is defined as a subset of sealed box systems where the acoustical compliance of the enclosure is substantially smaller than the compliance of the driver suspension, and thus it is the enclosure compliance that cominates the total system compliance. Typically, this means that the enclosure volume is NO MORE than 1/4 the equivalent volume of compliance of the driver, specifically: Vb = Vas / 4 In such an arrangement, the enclosure provides the major portion of the system stuffness seen by the driver, and the amount of stiffness provided by the suspension is relatively insignificant by comparison. |
#23
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Speakers Then and Now
(Svante) wrote in message om...
(Dick Pierce) wrote in message The efficiency of ANY direct-radiator system (bass reflex, ported, vented, sealed, acoustic suspension, infinite baffle) is determined by the driver. The driver's electrical resistance, its moving mass, its radiating area and its magnet system determine that efficiency, period. The enclosure, in combination with the driver, determines the system response function near the low end cutoff. I agree to your post, except for one little word; the "period" above. The efficiency is also affected by the placement of the speaker. It is doubled if it is mounted in a wall, compared to radiating in free space. Efficiency increases even more if mounted in a corner etc. OK, OK, I'm being picky and maybe that has nothing to do with the design of the speaker. ...or maybe it does? If the speaker is designed for free-field conditions, the speaker will still be radiating in half-space toward higher frequencies, and thus have a lift of +6dB. This should be compensated for. If the same speaker is mounted in the wall, the HF boost will not occur (or rather, an equally large LF boost will occur), so then no compensation is needed. So, the placement of the speaker is something that the designer of the system should consider. Actually, no, the efficiency, specifically, the ratio of total radiated acoustic power to total input electrical power does NOT change. The sound pressure level on axis MAY change, but the efficiency does not. The same power is distributed over a smaller area, and since SPL is a measure of power per unit area, the SPL changes, but the power output does not. However, strictly speaking, the efficiency varies a lot with frequency. When the motion is NOT mass-controlled, the situation is completely different. There is a specific definition for efficiency, which is very clear on the meaning, that is, the efficiency above the system cutoff but below the frequency where the wavelength is equal to the circumference of the radiator. SMall and Thiele and others are quite clear on this definition, and I defer to their definition. For example, the efficiency for the closed box peaks at the system resonance, but since the electrical impedance also does, less power is delivered to the speaker (for a given voltage) and the output is largely the same as for higher frequencies (-3dB for a butterworth design). Well below the resonance it drops by 12 dB/octave. But hardly anyone speaks about efficiency as being varying with frequency, "it is one number, period". In my opinion this adds to the confusion regarding efficiency. As the definition used in the domain is quite clear, no, it in fact removes such confusion. BTW is there a difference between "ported", "bass-reflex" and "vented"? Generally, these terms are synonymous. "Sealed" and "acoustic suspension"? Aren't they synonyms? No, indeed, they are not. While an acoustic suspension enclosure is a sealed enclosure, the converse is not necessarily true. A "sealed" enclosure can be defined broadly a number of ways, but generally refers to any enclosure where the time constant of any "leak" is MUCH longer than the time constant of the system cutoff frequency. Also, any such leak cannot contrinute at all to the total system output. Essentially, the enclosed air looks like a simple acoustical compliance. An "acoustic suspension" is defined as a subset of sealed box systems where the acoustical compliance of the enclosure is substantially smaller than the compliance of the driver suspension, and thus it is the enclosure compliance that cominates the total system compliance. Typically, this means that the enclosure volume is NO MORE than 1/4 the equivalent volume of compliance of the driver, specifically: Vb = Vas / 4 In such an arrangement, the enclosure provides the major portion of the system stuffness seen by the driver, and the amount of stiffness provided by the suspension is relatively insignificant by comparison. |
#24
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Speakers Then and Now
(Svante) wrote in message om...
(Dick Pierce) wrote in message The efficiency of ANY direct-radiator system (bass reflex, ported, vented, sealed, acoustic suspension, infinite baffle) is determined by the driver. The driver's electrical resistance, its moving mass, its radiating area and its magnet system determine that efficiency, period. The enclosure, in combination with the driver, determines the system response function near the low end cutoff. I agree to your post, except for one little word; the "period" above. The efficiency is also affected by the placement of the speaker. It is doubled if it is mounted in a wall, compared to radiating in free space. Efficiency increases even more if mounted in a corner etc. OK, OK, I'm being picky and maybe that has nothing to do with the design of the speaker. ...or maybe it does? If the speaker is designed for free-field conditions, the speaker will still be radiating in half-space toward higher frequencies, and thus have a lift of +6dB. This should be compensated for. If the same speaker is mounted in the wall, the HF boost will not occur (or rather, an equally large LF boost will occur), so then no compensation is needed. So, the placement of the speaker is something that the designer of the system should consider. Actually, no, the efficiency, specifically, the ratio of total radiated acoustic power to total input electrical power does NOT change. The sound pressure level on axis MAY change, but the efficiency does not. The same power is distributed over a smaller area, and since SPL is a measure of power per unit area, the SPL changes, but the power output does not. However, strictly speaking, the efficiency varies a lot with frequency. When the motion is NOT mass-controlled, the situation is completely different. There is a specific definition for efficiency, which is very clear on the meaning, that is, the efficiency above the system cutoff but below the frequency where the wavelength is equal to the circumference of the radiator. SMall and Thiele and others are quite clear on this definition, and I defer to their definition. For example, the efficiency for the closed box peaks at the system resonance, but since the electrical impedance also does, less power is delivered to the speaker (for a given voltage) and the output is largely the same as for higher frequencies (-3dB for a butterworth design). Well below the resonance it drops by 12 dB/octave. But hardly anyone speaks about efficiency as being varying with frequency, "it is one number, period". In my opinion this adds to the confusion regarding efficiency. As the definition used in the domain is quite clear, no, it in fact removes such confusion. BTW is there a difference between "ported", "bass-reflex" and "vented"? Generally, these terms are synonymous. "Sealed" and "acoustic suspension"? Aren't they synonyms? No, indeed, they are not. While an acoustic suspension enclosure is a sealed enclosure, the converse is not necessarily true. A "sealed" enclosure can be defined broadly a number of ways, but generally refers to any enclosure where the time constant of any "leak" is MUCH longer than the time constant of the system cutoff frequency. Also, any such leak cannot contrinute at all to the total system output. Essentially, the enclosed air looks like a simple acoustical compliance. An "acoustic suspension" is defined as a subset of sealed box systems where the acoustical compliance of the enclosure is substantially smaller than the compliance of the driver suspension, and thus it is the enclosure compliance that cominates the total system compliance. Typically, this means that the enclosure volume is NO MORE than 1/4 the equivalent volume of compliance of the driver, specifically: Vb = Vas / 4 In such an arrangement, the enclosure provides the major portion of the system stuffness seen by the driver, and the amount of stiffness provided by the suspension is relatively insignificant by comparison. |
#25
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Speakers Then and Now
"Peter Larsen" wrote in message ... Yes, as it was prior to foam getting intruced and because there are quite many people who will not ever purchase anything with a foam surround for some straaange reason. The fact that I have many rubber, paper or cloth surround woofers still working after 30 years or more, and all foam surrounds stuffed in much less time, is probably reason enough for me. TonyP. |
#26
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Speakers Then and Now
"Peter Larsen" wrote in message ... Yes, as it was prior to foam getting intruced and because there are quite many people who will not ever purchase anything with a foam surround for some straaange reason. The fact that I have many rubber, paper or cloth surround woofers still working after 30 years or more, and all foam surrounds stuffed in much less time, is probably reason enough for me. TonyP. |
#27
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Speakers Then and Now
"Peter Larsen" wrote in message ... Yes, as it was prior to foam getting intruced and because there are quite many people who will not ever purchase anything with a foam surround for some straaange reason. The fact that I have many rubber, paper or cloth surround woofers still working after 30 years or more, and all foam surrounds stuffed in much less time, is probably reason enough for me. TonyP. |
#28
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Speakers Then and Now
"Peter Larsen" wrote in message ... Yes, as it was prior to foam getting intruced and because there are quite many people who will not ever purchase anything with a foam surround for some straaange reason. The fact that I have many rubber, paper or cloth surround woofers still working after 30 years or more, and all foam surrounds stuffed in much less time, is probably reason enough for me. TonyP. |
#29
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Speakers Then and Now
(Dick Pierce) wrote in message . com...
(Svante) wrote in message om... (Dick Pierce) wrote in message The efficiency of ANY direct-radiator system (bass reflex, ported, vented, sealed, acoustic suspension, infinite baffle) is determined by the driver. The driver's electrical resistance, its moving mass, its radiating area and its magnet system determine that efficiency, period. The enclosure, in combination with the driver, determines the system response function near the low end cutoff. I agree to your post, except for one little word; the "period" above. The efficiency is also affected by the placement of the speaker. It is doubled if it is mounted in a wall, compared to radiating in free space. Efficiency increases even more if mounted in a corner etc. OK, OK, I'm being picky and maybe that has nothing to do with the design of the speaker. ...or maybe it does? If the speaker is designed for free-field conditions, the speaker will still be radiating in half-space toward higher frequencies, and thus have a lift of +6dB. This should be compensated for. If the same speaker is mounted in the wall, the HF boost will not occur (or rather, an equally large LF boost will occur), so then no compensation is needed. So, the placement of the speaker is something that the designer of the system should consider. Actually, no, the efficiency, specifically, the ratio of total radiated acoustic power to total input electrical power does NOT change. The sound pressure level on axis MAY change, but the efficiency does not. The same power is distributed over a smaller area, and since SPL is a measure of power per unit area, the SPL changes, but the power output does not. I think we had this discussion before, but then the issue was what happens if there are two loudspeakers present. I waited for a final post from you there, but failed to see it. The thread name was "Speaker sensitivity and fs in multiples." Actually I argue the the output power DOES increase. The wall acts as a mirror (in the optical analogy) and the source and its mirror image together double the sound pressure, and thus quadruples the intensity. This leads to a level increase of +6dB. However, since the area hit by this radiation is of half the size, the power is "only" increased by a factor 2. Another way of seing it is that the radiation impedance is doubled. However, strictly speaking, the efficiency varies a lot with frequency. When the motion is NOT mass-controlled, the situation is completely different. There is a specific definition for efficiency, which is very clear on the meaning, that is, the efficiency above the system cutoff but below the frequency where the wavelength is equal to the circumference of the radiator. SMall and Thiele and others are quite clear on this definition, and I defer to their definition. OK, that's what most people do, and I see the benefits of doing so. However, the original definition of efficiency (which can be applied to many things, such as car motors etc) is the ratio between output and input power. For example, the efficiency for the closed box peaks at the system resonance, but since the electrical impedance also does, less power is delivered to the speaker (for a given voltage) and the output is largely the same as for higher frequencies (-3dB for a butterworth design). Well below the resonance it drops by 12 dB/octave. But hardly anyone speaks about efficiency as being varying with frequency, "it is one number, period". In my opinion this adds to the confusion regarding efficiency. As the definition used in the domain is quite clear, no, it in fact removes such confusion. Any person who has heard the word "efficiency" in other contexts may be confused IMO. And I guess those are not few. BTW is there a difference between "ported", "bass-reflex" and "vented"? Generally, these terms are synonymous. "Sealed" and "acoustic suspension"? Aren't they synonyms? No, indeed, they are not. While an acoustic suspension enclosure is a sealed enclosure, the converse is not necessarily true. A "sealed" enclosure can be defined broadly a number of ways, but generally refers to any enclosure where the time constant of any "leak" is MUCH longer than the time constant of the system cutoff frequency. Also, any such leak cannot contrinute at all to the total system output. Essentially, the enclosed air looks like a simple acoustical compliance. An "acoustic suspension" is defined as a subset of sealed box systems where the acoustical compliance of the enclosure is substantially smaller than the compliance of the driver suspension, and thus it is the enclosure compliance that cominates the total system compliance. Typically, this means that the enclosure volume is NO MORE than 1/4 the equivalent volume of compliance of the driver, specifically: Vb = Vas / 4 In such an arrangement, the enclosure provides the major portion of the system stuffness seen by the driver, and the amount of stiffness provided by the suspension is relatively insignificant by comparison. OK, so in my mind they ARE principally the same, it is just a matter of which compliance that dominates (which of course is not insignificant when it comes to the actual design). |
#30
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Speakers Then and Now
(Dick Pierce) wrote in message . com...
(Svante) wrote in message om... (Dick Pierce) wrote in message The efficiency of ANY direct-radiator system (bass reflex, ported, vented, sealed, acoustic suspension, infinite baffle) is determined by the driver. The driver's electrical resistance, its moving mass, its radiating area and its magnet system determine that efficiency, period. The enclosure, in combination with the driver, determines the system response function near the low end cutoff. I agree to your post, except for one little word; the "period" above. The efficiency is also affected by the placement of the speaker. It is doubled if it is mounted in a wall, compared to radiating in free space. Efficiency increases even more if mounted in a corner etc. OK, OK, I'm being picky and maybe that has nothing to do with the design of the speaker. ...or maybe it does? If the speaker is designed for free-field conditions, the speaker will still be radiating in half-space toward higher frequencies, and thus have a lift of +6dB. This should be compensated for. If the same speaker is mounted in the wall, the HF boost will not occur (or rather, an equally large LF boost will occur), so then no compensation is needed. So, the placement of the speaker is something that the designer of the system should consider. Actually, no, the efficiency, specifically, the ratio of total radiated acoustic power to total input electrical power does NOT change. The sound pressure level on axis MAY change, but the efficiency does not. The same power is distributed over a smaller area, and since SPL is a measure of power per unit area, the SPL changes, but the power output does not. I think we had this discussion before, but then the issue was what happens if there are two loudspeakers present. I waited for a final post from you there, but failed to see it. The thread name was "Speaker sensitivity and fs in multiples." Actually I argue the the output power DOES increase. The wall acts as a mirror (in the optical analogy) and the source and its mirror image together double the sound pressure, and thus quadruples the intensity. This leads to a level increase of +6dB. However, since the area hit by this radiation is of half the size, the power is "only" increased by a factor 2. Another way of seing it is that the radiation impedance is doubled. However, strictly speaking, the efficiency varies a lot with frequency. When the motion is NOT mass-controlled, the situation is completely different. There is a specific definition for efficiency, which is very clear on the meaning, that is, the efficiency above the system cutoff but below the frequency where the wavelength is equal to the circumference of the radiator. SMall and Thiele and others are quite clear on this definition, and I defer to their definition. OK, that's what most people do, and I see the benefits of doing so. However, the original definition of efficiency (which can be applied to many things, such as car motors etc) is the ratio between output and input power. For example, the efficiency for the closed box peaks at the system resonance, but since the electrical impedance also does, less power is delivered to the speaker (for a given voltage) and the output is largely the same as for higher frequencies (-3dB for a butterworth design). Well below the resonance it drops by 12 dB/octave. But hardly anyone speaks about efficiency as being varying with frequency, "it is one number, period". In my opinion this adds to the confusion regarding efficiency. As the definition used in the domain is quite clear, no, it in fact removes such confusion. Any person who has heard the word "efficiency" in other contexts may be confused IMO. And I guess those are not few. BTW is there a difference between "ported", "bass-reflex" and "vented"? Generally, these terms are synonymous. "Sealed" and "acoustic suspension"? Aren't they synonyms? No, indeed, they are not. While an acoustic suspension enclosure is a sealed enclosure, the converse is not necessarily true. A "sealed" enclosure can be defined broadly a number of ways, but generally refers to any enclosure where the time constant of any "leak" is MUCH longer than the time constant of the system cutoff frequency. Also, any such leak cannot contrinute at all to the total system output. Essentially, the enclosed air looks like a simple acoustical compliance. An "acoustic suspension" is defined as a subset of sealed box systems where the acoustical compliance of the enclosure is substantially smaller than the compliance of the driver suspension, and thus it is the enclosure compliance that cominates the total system compliance. Typically, this means that the enclosure volume is NO MORE than 1/4 the equivalent volume of compliance of the driver, specifically: Vb = Vas / 4 In such an arrangement, the enclosure provides the major portion of the system stuffness seen by the driver, and the amount of stiffness provided by the suspension is relatively insignificant by comparison. OK, so in my mind they ARE principally the same, it is just a matter of which compliance that dominates (which of course is not insignificant when it comes to the actual design). |
#31
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Speakers Then and Now
(Dick Pierce) wrote in message . com...
(Svante) wrote in message om... (Dick Pierce) wrote in message The efficiency of ANY direct-radiator system (bass reflex, ported, vented, sealed, acoustic suspension, infinite baffle) is determined by the driver. The driver's electrical resistance, its moving mass, its radiating area and its magnet system determine that efficiency, period. The enclosure, in combination with the driver, determines the system response function near the low end cutoff. I agree to your post, except for one little word; the "period" above. The efficiency is also affected by the placement of the speaker. It is doubled if it is mounted in a wall, compared to radiating in free space. Efficiency increases even more if mounted in a corner etc. OK, OK, I'm being picky and maybe that has nothing to do with the design of the speaker. ...or maybe it does? If the speaker is designed for free-field conditions, the speaker will still be radiating in half-space toward higher frequencies, and thus have a lift of +6dB. This should be compensated for. If the same speaker is mounted in the wall, the HF boost will not occur (or rather, an equally large LF boost will occur), so then no compensation is needed. So, the placement of the speaker is something that the designer of the system should consider. Actually, no, the efficiency, specifically, the ratio of total radiated acoustic power to total input electrical power does NOT change. The sound pressure level on axis MAY change, but the efficiency does not. The same power is distributed over a smaller area, and since SPL is a measure of power per unit area, the SPL changes, but the power output does not. I think we had this discussion before, but then the issue was what happens if there are two loudspeakers present. I waited for a final post from you there, but failed to see it. The thread name was "Speaker sensitivity and fs in multiples." Actually I argue the the output power DOES increase. The wall acts as a mirror (in the optical analogy) and the source and its mirror image together double the sound pressure, and thus quadruples the intensity. This leads to a level increase of +6dB. However, since the area hit by this radiation is of half the size, the power is "only" increased by a factor 2. Another way of seing it is that the radiation impedance is doubled. However, strictly speaking, the efficiency varies a lot with frequency. When the motion is NOT mass-controlled, the situation is completely different. There is a specific definition for efficiency, which is very clear on the meaning, that is, the efficiency above the system cutoff but below the frequency where the wavelength is equal to the circumference of the radiator. SMall and Thiele and others are quite clear on this definition, and I defer to their definition. OK, that's what most people do, and I see the benefits of doing so. However, the original definition of efficiency (which can be applied to many things, such as car motors etc) is the ratio between output and input power. For example, the efficiency for the closed box peaks at the system resonance, but since the electrical impedance also does, less power is delivered to the speaker (for a given voltage) and the output is largely the same as for higher frequencies (-3dB for a butterworth design). Well below the resonance it drops by 12 dB/octave. But hardly anyone speaks about efficiency as being varying with frequency, "it is one number, period". In my opinion this adds to the confusion regarding efficiency. As the definition used in the domain is quite clear, no, it in fact removes such confusion. Any person who has heard the word "efficiency" in other contexts may be confused IMO. And I guess those are not few. BTW is there a difference between "ported", "bass-reflex" and "vented"? Generally, these terms are synonymous. "Sealed" and "acoustic suspension"? Aren't they synonyms? No, indeed, they are not. While an acoustic suspension enclosure is a sealed enclosure, the converse is not necessarily true. A "sealed" enclosure can be defined broadly a number of ways, but generally refers to any enclosure where the time constant of any "leak" is MUCH longer than the time constant of the system cutoff frequency. Also, any such leak cannot contrinute at all to the total system output. Essentially, the enclosed air looks like a simple acoustical compliance. An "acoustic suspension" is defined as a subset of sealed box systems where the acoustical compliance of the enclosure is substantially smaller than the compliance of the driver suspension, and thus it is the enclosure compliance that cominates the total system compliance. Typically, this means that the enclosure volume is NO MORE than 1/4 the equivalent volume of compliance of the driver, specifically: Vb = Vas / 4 In such an arrangement, the enclosure provides the major portion of the system stuffness seen by the driver, and the amount of stiffness provided by the suspension is relatively insignificant by comparison. OK, so in my mind they ARE principally the same, it is just a matter of which compliance that dominates (which of course is not insignificant when it comes to the actual design). |
#32
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Speakers Then and Now
(Dick Pierce) wrote in message . com...
(Svante) wrote in message om... (Dick Pierce) wrote in message The efficiency of ANY direct-radiator system (bass reflex, ported, vented, sealed, acoustic suspension, infinite baffle) is determined by the driver. The driver's electrical resistance, its moving mass, its radiating area and its magnet system determine that efficiency, period. The enclosure, in combination with the driver, determines the system response function near the low end cutoff. I agree to your post, except for one little word; the "period" above. The efficiency is also affected by the placement of the speaker. It is doubled if it is mounted in a wall, compared to radiating in free space. Efficiency increases even more if mounted in a corner etc. OK, OK, I'm being picky and maybe that has nothing to do with the design of the speaker. ...or maybe it does? If the speaker is designed for free-field conditions, the speaker will still be radiating in half-space toward higher frequencies, and thus have a lift of +6dB. This should be compensated for. If the same speaker is mounted in the wall, the HF boost will not occur (or rather, an equally large LF boost will occur), so then no compensation is needed. So, the placement of the speaker is something that the designer of the system should consider. Actually, no, the efficiency, specifically, the ratio of total radiated acoustic power to total input electrical power does NOT change. The sound pressure level on axis MAY change, but the efficiency does not. The same power is distributed over a smaller area, and since SPL is a measure of power per unit area, the SPL changes, but the power output does not. I think we had this discussion before, but then the issue was what happens if there are two loudspeakers present. I waited for a final post from you there, but failed to see it. The thread name was "Speaker sensitivity and fs in multiples." Actually I argue the the output power DOES increase. The wall acts as a mirror (in the optical analogy) and the source and its mirror image together double the sound pressure, and thus quadruples the intensity. This leads to a level increase of +6dB. However, since the area hit by this radiation is of half the size, the power is "only" increased by a factor 2. Another way of seing it is that the radiation impedance is doubled. However, strictly speaking, the efficiency varies a lot with frequency. When the motion is NOT mass-controlled, the situation is completely different. There is a specific definition for efficiency, which is very clear on the meaning, that is, the efficiency above the system cutoff but below the frequency where the wavelength is equal to the circumference of the radiator. SMall and Thiele and others are quite clear on this definition, and I defer to their definition. OK, that's what most people do, and I see the benefits of doing so. However, the original definition of efficiency (which can be applied to many things, such as car motors etc) is the ratio between output and input power. For example, the efficiency for the closed box peaks at the system resonance, but since the electrical impedance also does, less power is delivered to the speaker (for a given voltage) and the output is largely the same as for higher frequencies (-3dB for a butterworth design). Well below the resonance it drops by 12 dB/octave. But hardly anyone speaks about efficiency as being varying with frequency, "it is one number, period". In my opinion this adds to the confusion regarding efficiency. As the definition used in the domain is quite clear, no, it in fact removes such confusion. Any person who has heard the word "efficiency" in other contexts may be confused IMO. And I guess those are not few. BTW is there a difference between "ported", "bass-reflex" and "vented"? Generally, these terms are synonymous. "Sealed" and "acoustic suspension"? Aren't they synonyms? No, indeed, they are not. While an acoustic suspension enclosure is a sealed enclosure, the converse is not necessarily true. A "sealed" enclosure can be defined broadly a number of ways, but generally refers to any enclosure where the time constant of any "leak" is MUCH longer than the time constant of the system cutoff frequency. Also, any such leak cannot contrinute at all to the total system output. Essentially, the enclosed air looks like a simple acoustical compliance. An "acoustic suspension" is defined as a subset of sealed box systems where the acoustical compliance of the enclosure is substantially smaller than the compliance of the driver suspension, and thus it is the enclosure compliance that cominates the total system compliance. Typically, this means that the enclosure volume is NO MORE than 1/4 the equivalent volume of compliance of the driver, specifically: Vb = Vas / 4 In such an arrangement, the enclosure provides the major portion of the system stuffness seen by the driver, and the amount of stiffness provided by the suspension is relatively insignificant by comparison. OK, so in my mind they ARE principally the same, it is just a matter of which compliance that dominates (which of course is not insignificant when it comes to the actual design). |
#33
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Speakers Then and Now
"Svante" wrote in message
om... Actually I argue the the output power DOES increase. The wall acts as You can argue all you want but you will be wrong. a mirror (in the optical analogy) and the source and its mirror image together double the sound pressure, and thus quadruples the intensity. This leads to a level increase of +6dB. However, since the area hit by this radiation is of half the size, the power is "only" increased by a factor 2. Another way of seing it is that the radiation impedance is doubled. No. The output power of the driver does not change. The efficiency does not change. It's similar to changing a flashlight focus from a widebeam flood to a narrow beam spot. The light may be directed to a smaller area but the power output and efficiency of the bulb does not change. There is a specific definition for efficiency, which is very clear on the meaning, that is, the efficiency above the system cutoff but below the frequency where the wavelength is equal to the circumference of the radiator. SMall and Thiele and others are quite clear on this definition, and I defer to their definition. OK, that's what most people do, and I see the benefits of doing so. However, the original definition of efficiency (which can be applied to many things, such as car motors etc) is the ratio between output and input power. As it is in this case. Acoustical output of the driver in watts divided by electrical input in watts. You may be changing the radiation pattern but the power output of the driver does not change. Any person who has heard the word "efficiency" in other contexts may be confused IMO. And I guess those are not few. The context is the same in this situation. |
#34
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Speakers Then and Now
"Svante" wrote in message
om... Actually I argue the the output power DOES increase. The wall acts as You can argue all you want but you will be wrong. a mirror (in the optical analogy) and the source and its mirror image together double the sound pressure, and thus quadruples the intensity. This leads to a level increase of +6dB. However, since the area hit by this radiation is of half the size, the power is "only" increased by a factor 2. Another way of seing it is that the radiation impedance is doubled. No. The output power of the driver does not change. The efficiency does not change. It's similar to changing a flashlight focus from a widebeam flood to a narrow beam spot. The light may be directed to a smaller area but the power output and efficiency of the bulb does not change. There is a specific definition for efficiency, which is very clear on the meaning, that is, the efficiency above the system cutoff but below the frequency where the wavelength is equal to the circumference of the radiator. SMall and Thiele and others are quite clear on this definition, and I defer to their definition. OK, that's what most people do, and I see the benefits of doing so. However, the original definition of efficiency (which can be applied to many things, such as car motors etc) is the ratio between output and input power. As it is in this case. Acoustical output of the driver in watts divided by electrical input in watts. You may be changing the radiation pattern but the power output of the driver does not change. Any person who has heard the word "efficiency" in other contexts may be confused IMO. And I guess those are not few. The context is the same in this situation. |
#35
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Speakers Then and Now
"Svante" wrote in message
om... Actually I argue the the output power DOES increase. The wall acts as You can argue all you want but you will be wrong. a mirror (in the optical analogy) and the source and its mirror image together double the sound pressure, and thus quadruples the intensity. This leads to a level increase of +6dB. However, since the area hit by this radiation is of half the size, the power is "only" increased by a factor 2. Another way of seing it is that the radiation impedance is doubled. No. The output power of the driver does not change. The efficiency does not change. It's similar to changing a flashlight focus from a widebeam flood to a narrow beam spot. The light may be directed to a smaller area but the power output and efficiency of the bulb does not change. There is a specific definition for efficiency, which is very clear on the meaning, that is, the efficiency above the system cutoff but below the frequency where the wavelength is equal to the circumference of the radiator. SMall and Thiele and others are quite clear on this definition, and I defer to their definition. OK, that's what most people do, and I see the benefits of doing so. However, the original definition of efficiency (which can be applied to many things, such as car motors etc) is the ratio between output and input power. As it is in this case. Acoustical output of the driver in watts divided by electrical input in watts. You may be changing the radiation pattern but the power output of the driver does not change. Any person who has heard the word "efficiency" in other contexts may be confused IMO. And I guess those are not few. The context is the same in this situation. |
#36
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Speakers Then and Now
"Svante" wrote in message
om... Actually I argue the the output power DOES increase. The wall acts as You can argue all you want but you will be wrong. a mirror (in the optical analogy) and the source and its mirror image together double the sound pressure, and thus quadruples the intensity. This leads to a level increase of +6dB. However, since the area hit by this radiation is of half the size, the power is "only" increased by a factor 2. Another way of seing it is that the radiation impedance is doubled. No. The output power of the driver does not change. The efficiency does not change. It's similar to changing a flashlight focus from a widebeam flood to a narrow beam spot. The light may be directed to a smaller area but the power output and efficiency of the bulb does not change. There is a specific definition for efficiency, which is very clear on the meaning, that is, the efficiency above the system cutoff but below the frequency where the wavelength is equal to the circumference of the radiator. SMall and Thiele and others are quite clear on this definition, and I defer to their definition. OK, that's what most people do, and I see the benefits of doing so. However, the original definition of efficiency (which can be applied to many things, such as car motors etc) is the ratio between output and input power. As it is in this case. Acoustical output of the driver in watts divided by electrical input in watts. You may be changing the radiation pattern but the power output of the driver does not change. Any person who has heard the word "efficiency" in other contexts may be confused IMO. And I guess those are not few. The context is the same in this situation. |
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Speakers Then and Now
On Wed, 7 Jan 2004 03:58:09 -0600, "Rusty Boudreaux"
wrote: "Svante" wrote in message . com... Actually I argue the the output power DOES increase. The wall acts as You can argue all you want but you will be wrong. Betting is still open. . . a mirror (in the optical analogy) and the source and its mirror image together double the sound pressure, and thus quadruples the intensity. This leads to a level increase of +6dB. However, since the area hit by this radiation is of half the size, the power is "only" increased by a factor 2. Another way of seing it is that the radiation impedance is doubled. No. The output power of the driver does not change. The efficiency does not change. It's similar to changing a flashlight focus from a widebeam flood to a narrow beam spot. The light may be directed to a smaller area but the power output and efficiency of the bulb does not change. White light is incoherent and the wavlength of green, say 532 nm is considerably shorter than, say, a 1cm filament. You analogy is ********. There is a specific definition for efficiency, which is very clear on the meaning, that is, the efficiency above the system cutoff but below the frequency where the wavelength is equal to the circumference of the radiator. SMall and Thiele and others are quite clear on this definition, and I defer to their definition. OK, that's what most people do, and I see the benefits of doing so. However, the original definition of efficiency (which can be applied to many things, such as car motors etc) is the ratio between output and input power. As it is in this case. Acoustical output of the driver in watts divided by electrical input in watts. You may be changing the radiation pattern but the power output of the driver does not change. Any person who has heard the word "efficiency" in other contexts may be confused IMO. And I guess those are not few. The context is the same in this situation. |
#38
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Speakers Then and Now
On Wed, 7 Jan 2004 03:58:09 -0600, "Rusty Boudreaux"
wrote: "Svante" wrote in message . com... Actually I argue the the output power DOES increase. The wall acts as You can argue all you want but you will be wrong. Betting is still open. . . a mirror (in the optical analogy) and the source and its mirror image together double the sound pressure, and thus quadruples the intensity. This leads to a level increase of +6dB. However, since the area hit by this radiation is of half the size, the power is "only" increased by a factor 2. Another way of seing it is that the radiation impedance is doubled. No. The output power of the driver does not change. The efficiency does not change. It's similar to changing a flashlight focus from a widebeam flood to a narrow beam spot. The light may be directed to a smaller area but the power output and efficiency of the bulb does not change. White light is incoherent and the wavlength of green, say 532 nm is considerably shorter than, say, a 1cm filament. You analogy is ********. There is a specific definition for efficiency, which is very clear on the meaning, that is, the efficiency above the system cutoff but below the frequency where the wavelength is equal to the circumference of the radiator. SMall and Thiele and others are quite clear on this definition, and I defer to their definition. OK, that's what most people do, and I see the benefits of doing so. However, the original definition of efficiency (which can be applied to many things, such as car motors etc) is the ratio between output and input power. As it is in this case. Acoustical output of the driver in watts divided by electrical input in watts. You may be changing the radiation pattern but the power output of the driver does not change. Any person who has heard the word "efficiency" in other contexts may be confused IMO. And I guess those are not few. The context is the same in this situation. |
#39
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Speakers Then and Now
On Wed, 7 Jan 2004 03:58:09 -0600, "Rusty Boudreaux"
wrote: "Svante" wrote in message . com... Actually I argue the the output power DOES increase. The wall acts as You can argue all you want but you will be wrong. Betting is still open. . . a mirror (in the optical analogy) and the source and its mirror image together double the sound pressure, and thus quadruples the intensity. This leads to a level increase of +6dB. However, since the area hit by this radiation is of half the size, the power is "only" increased by a factor 2. Another way of seing it is that the radiation impedance is doubled. No. The output power of the driver does not change. The efficiency does not change. It's similar to changing a flashlight focus from a widebeam flood to a narrow beam spot. The light may be directed to a smaller area but the power output and efficiency of the bulb does not change. White light is incoherent and the wavlength of green, say 532 nm is considerably shorter than, say, a 1cm filament. You analogy is ********. There is a specific definition for efficiency, which is very clear on the meaning, that is, the efficiency above the system cutoff but below the frequency where the wavelength is equal to the circumference of the radiator. SMall and Thiele and others are quite clear on this definition, and I defer to their definition. OK, that's what most people do, and I see the benefits of doing so. However, the original definition of efficiency (which can be applied to many things, such as car motors etc) is the ratio between output and input power. As it is in this case. Acoustical output of the driver in watts divided by electrical input in watts. You may be changing the radiation pattern but the power output of the driver does not change. Any person who has heard the word "efficiency" in other contexts may be confused IMO. And I guess those are not few. The context is the same in this situation. |
#40
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Speakers Then and Now
On Wed, 7 Jan 2004 03:58:09 -0600, "Rusty Boudreaux"
wrote: "Svante" wrote in message . com... Actually I argue the the output power DOES increase. The wall acts as You can argue all you want but you will be wrong. Betting is still open. . . a mirror (in the optical analogy) and the source and its mirror image together double the sound pressure, and thus quadruples the intensity. This leads to a level increase of +6dB. However, since the area hit by this radiation is of half the size, the power is "only" increased by a factor 2. Another way of seing it is that the radiation impedance is doubled. No. The output power of the driver does not change. The efficiency does not change. It's similar to changing a flashlight focus from a widebeam flood to a narrow beam spot. The light may be directed to a smaller area but the power output and efficiency of the bulb does not change. White light is incoherent and the wavlength of green, say 532 nm is considerably shorter than, say, a 1cm filament. You analogy is ********. There is a specific definition for efficiency, which is very clear on the meaning, that is, the efficiency above the system cutoff but below the frequency where the wavelength is equal to the circumference of the radiator. SMall and Thiele and others are quite clear on this definition, and I defer to their definition. OK, that's what most people do, and I see the benefits of doing so. However, the original definition of efficiency (which can be applied to many things, such as car motors etc) is the ratio between output and input power. As it is in this case. Acoustical output of the driver in watts divided by electrical input in watts. You may be changing the radiation pattern but the power output of the driver does not change. Any person who has heard the word "efficiency" in other contexts may be confused IMO. And I guess those are not few. The context is the same in this situation. |