" ... I noticed that you had a question about using heatpipes like they use in cpu towers. Check out the amplifier threads like the Aksa Lender P-Mos Hybrid Alpha 20 or the Alpha Big Boy or the Alpha Nirvana. They all use heatpipe sinks to handle the high dissipation of the Mosfets. These threads were started by xrk971, so search the threads started by xrk971 and enjoy the ride. ..."
Thank you! Will do. jj
Thank you! Will do. jj
" ... This is the most interesting thread I have read in years. Stupid Qs......No....enlightening. I didn't know I needed the information gleaned here until I read it. Keep em comin' jimmyjoe. ps...I am pretty old too. ... "
Thank you for the kind words, Puffin. I appreciate them. I was under the impression that my questions were beneath the notice of the very intelligent and technically-minded people on this site. I'm not very intelligent, and I'm definitely not technically-minded, so there have been questions to which I had sought answers for quite some time. Perhaps I simply wasn't asking them in the correct forum.
I'm a simple man; I believe the best answer to any problem is a simple one. Not simplistic, but not complicated either. I don't understand much math, and I am NOT skilled at the use of computers.
This leaves me outside many of the discussion on this site. That's fine; I believe there are other ways. A person just has to search. Find the answers to small problems. Use those to find the answers to bigger problems.
Other than having simple curiosity about many things audio, I really have only one "problem" that I need to address. I listen to my audio system while I work at a desk; the desk is for my computer as well as a place to construct fishing lures. I have been in love with the nearfield positioning since 1967.
I'm getting old, and my hearing acuity is poor. Paradoxically, my sensitivity to bass characteristics is increasing. I've been looking for a speaker that is nearfield, has decent bass capability, is reasonably directive and doesn't need TOO much power.
Decent bass characteristics? I hate bloated, boomy bass. It irritates me. Gergiev's BBC recording of "St. John's Eve" is a good example. The bass needs to be "clean".
Directivity? Ah, here we come to a real bugaboo. Wide-dispersion speakers can sound more natural because of a more even room response, but literally, that room response may be deleterious to nearfield clarity. So narrow-dispoersion, highly directional speakers CAN suit nearfield requirements better. Notice I said "can", not making it definite. That's why I was asking about the Hafler setup.
Not needing too much power? That one leads back to my ideas of simplicity. My personal feeling is that I dislike speakers that use large amounts of power and current. I simply have a personal dislike of the high heat generated. I believe (unreasonably, perhaps) that this type of speaker, once hot, restricts transient peaks and dynamics in general.
So now you know why I asked SOME of the questions that I asked here. Others were simply things that I didn't understand, and so I asked out of idle curiosity.
I have another question, one about soundfield perception, but I don't know yet how to put it into words so that it will be clear.
I'll work on that. jj
Thank you for the kind words, Puffin. I appreciate them. I was under the impression that my questions were beneath the notice of the very intelligent and technically-minded people on this site. I'm not very intelligent, and I'm definitely not technically-minded, so there have been questions to which I had sought answers for quite some time. Perhaps I simply wasn't asking them in the correct forum.
I'm a simple man; I believe the best answer to any problem is a simple one. Not simplistic, but not complicated either. I don't understand much math, and I am NOT skilled at the use of computers.
This leaves me outside many of the discussion on this site. That's fine; I believe there are other ways. A person just has to search. Find the answers to small problems. Use those to find the answers to bigger problems.
Other than having simple curiosity about many things audio, I really have only one "problem" that I need to address. I listen to my audio system while I work at a desk; the desk is for my computer as well as a place to construct fishing lures. I have been in love with the nearfield positioning since 1967.
I'm getting old, and my hearing acuity is poor. Paradoxically, my sensitivity to bass characteristics is increasing. I've been looking for a speaker that is nearfield, has decent bass capability, is reasonably directive and doesn't need TOO much power.
Decent bass characteristics? I hate bloated, boomy bass. It irritates me. Gergiev's BBC recording of "St. John's Eve" is a good example. The bass needs to be "clean".
Directivity? Ah, here we come to a real bugaboo. Wide-dispersion speakers can sound more natural because of a more even room response, but literally, that room response may be deleterious to nearfield clarity. So narrow-dispoersion, highly directional speakers CAN suit nearfield requirements better. Notice I said "can", not making it definite. That's why I was asking about the Hafler setup.
Not needing too much power? That one leads back to my ideas of simplicity. My personal feeling is that I dislike speakers that use large amounts of power and current. I simply have a personal dislike of the high heat generated. I believe (unreasonably, perhaps) that this type of speaker, once hot, restricts transient peaks and dynamics in general.
So now you know why I asked SOME of the questions that I asked here. Others were simply things that I didn't understand, and so I asked out of idle curiosity.
I have another question, one about soundfield perception, but I don't know yet how to put it into words so that it will be clear.
I'll work on that. jj
Actually, heating a speaker up does cause some of its parameters to drift. The resistance of the voice coil increases, and this changes the impedance and Q of the speaker.
Speakers with excellent dynamic response are typically high efficiency units. One speaker might need 10 watts to reproduce 95 dB SPL, and another might only need 1 watt. You know which one will get hotter. And in my experience, the speakers with the best dynamic response (least power compression) were always very efficient. I'm sure there are exceptions. A speaker with excellent dynamic compression characteristics might have 4-6 dB compression @ 110 dB SPL (very loud); an "average" speaker might be closer to 9-12 dB.
But ambient temperature, atmospheric pressure, and humidity can have a large effect on how a speaker performs in a given enclosure as well. There's a lot of moving parts.
Thank you, Fast Eddie.
This brings to mind another question. (Full of them, aren't I?) Some time ago, there was a speaker system on the market that advertised an advantage using the word "adiabatic". I have no idea what the advantage was, and I also have trouble understanding the term "adiabatic". Not that I haven't tried, mind you. I've looked it up in several texts and on Wikipedia (the warehouse of slight untruths) and I just can't get my head around what the heck they're talking about.
Can anyone explain "adiabatic" in plain, simple language that I can understand? Thank you ahead of time. jj
This brings to mind another question. (Full of them, aren't I?) Some time ago, there was a speaker system on the market that advertised an advantage using the word "adiabatic". I have no idea what the advantage was, and I also have trouble understanding the term "adiabatic". Not that I haven't tried, mind you. I've looked it up in several texts and on Wikipedia (the warehouse of slight untruths) and I just can't get my head around what the heck they're talking about.
Can anyone explain "adiabatic" in plain, simple language that I can understand? Thank you ahead of time. jj
When the air in a sealed enclosure is compressed, its pressure increases. At the same time, the mechanical work done in compressing the air is transformed into heat energy which causes the temperature of the air to increase.
If the heat is allowed to escape then the process is said to be isothermal, meaning the temperature remains the same.
However, rapidly changing the pressure at audio frequencies in a sealed loudspeaker enclosure gives the heat no time to escape. Adiabatic is the name used when heat does not leave a system, so untreated sealed cabinets are classed as adiabatic.
Filling a sealed enclosure with absorbent material allows heat to transfer from the air to the absorbent. This converts the loudspeaker enclosure to isothermal action by stabilising the temperature.
If the heat is allowed to escape then the process is said to be isothermal, meaning the temperature remains the same.
However, rapidly changing the pressure at audio frequencies in a sealed loudspeaker enclosure gives the heat no time to escape. Adiabatic is the name used when heat does not leave a system, so untreated sealed cabinets are classed as adiabatic.
Filling a sealed enclosure with absorbent material allows heat to transfer from the air to the absorbent. This converts the loudspeaker enclosure to isothermal action by stabilising the temperature.
" .... When the air in a sealed enclosure is compressed, its pressure increases. At the same time, the mechanical work done in compressing the air is transformed into heat energy which causes the temperature of the air to increase.
If the heat is allowed to escape then the process is said to be isothermal, meaning the temperature remains the same.
However, rapidly changing the pressure at audio frequencies in a sealed loudspeaker enclosure gives the heat no time to escape. ...."
Aha .... I get it now. I had been thinking along the lines of adiabatic being compression ONLY, and I couldn't see how that related to a loudspeaker system.
And it doesn't, because there's another side of the process that I wasn't seeing; the rarefaction.
So in a loudspeaker system at rest, the air pressure is zero. When a bass note at 40 cycles comes along, the woofer (let's say a bit 15" unit) starts to move. Initially, the cone moves INWARD, compressing the air inside from the zero standard to .... oh, let's say a positive air pressure of +1. But that's only half of the 40 cycle wave; the other half is the woofer coming forward to the zero point, which re-stablizes the air pressure to the zero value, and then commences forward on its path OUTWARD to completing the wave reproduction. At the forward apex of movement, the air pressure might be said to be something like -1 in value.
Air is an insulator, not a good conductor of heat. So in only 1/40th of a second, the heat buildup in the enclosure can't transfer out before the forward movement of the woofer cone causes rarefaction, nullifying the heat buildup. Maybe if the gas inside the enclosure was Freon or some similar gas, the heat transfer would be fast enough that the characteristics would be different. But with air, it's not.
Have I got it correct? jj
If the heat is allowed to escape then the process is said to be isothermal, meaning the temperature remains the same.
However, rapidly changing the pressure at audio frequencies in a sealed loudspeaker enclosure gives the heat no time to escape. ...."
Aha .... I get it now. I had been thinking along the lines of adiabatic being compression ONLY, and I couldn't see how that related to a loudspeaker system.
And it doesn't, because there's another side of the process that I wasn't seeing; the rarefaction.
So in a loudspeaker system at rest, the air pressure is zero. When a bass note at 40 cycles comes along, the woofer (let's say a bit 15" unit) starts to move. Initially, the cone moves INWARD, compressing the air inside from the zero standard to .... oh, let's say a positive air pressure of +1. But that's only half of the 40 cycle wave; the other half is the woofer coming forward to the zero point, which re-stablizes the air pressure to the zero value, and then commences forward on its path OUTWARD to completing the wave reproduction. At the forward apex of movement, the air pressure might be said to be something like -1 in value.
Air is an insulator, not a good conductor of heat. So in only 1/40th of a second, the heat buildup in the enclosure can't transfer out before the forward movement of the woofer cone causes rarefaction, nullifying the heat buildup. Maybe if the gas inside the enclosure was Freon or some similar gas, the heat transfer would be fast enough that the characteristics would be different. But with air, it's not.
Have I got it correct? jj
The 'rarefaction' generates heat in the same way that the compression does, it does not 'nullify' the heat build up.
Work must be done to uncompress the air, which is also transformed to heat.
P.S. The air is a good insulator, but the absorbent is a less good insulator, allowing heat to conduct into the absorbent.
Work must be done to uncompress the air, which is also transformed to heat.
P.S. The air is a good insulator, but the absorbent is a less good insulator, allowing heat to conduct into the absorbent.
To what would the heatsink be connected? If it is to the air in the cabinet, the heat transfer would be minimal, and if it is to the driver, that is in the air that is being heated.
Galu said:
Filling a sealed enclosure with absorbent material allows heat to transfer from the air to the absorbent. This converts the loudspeaker enclosure to isothermal action by stabilising the temperature.
P.S. The air is a good insulator, but the absorbent is a less good insulator, allowing heat to conduct into the absorbent.
If these statements are true, wouldn't a heat sink be more efficient at transferring heat than the absorbent? Just integrate it into the box. Yes? No? jj
Filling a sealed enclosure with absorbent material allows heat to transfer from the air to the absorbent. This converts the loudspeaker enclosure to isothermal action by stabilising the temperature.
P.S. The air is a good insulator, but the absorbent is a less good insulator, allowing heat to conduct into the absorbent.
If these statements are true, wouldn't a heat sink be more efficient at transferring heat than the absorbent? Just integrate it into the box. Yes? No? jj
jimmyjoe asked what 'adiabatic' meant.
Filling an enclosure with absorbent converts low frequency compression/expansion of the air from adiabatic (increasing temperature) to isothermal (equal temperature).
Adiabatic conditions can be useful e.g. in a diesel engine where the rise in temperature due to the compression leads to the ignition of the air/fuel mixture without requiring a spark.
Filling an enclosure with absorbent converts low frequency compression/expansion of the air from adiabatic (increasing temperature) to isothermal (equal temperature).
Adiabatic conditions can be useful e.g. in a diesel engine where the rise in temperature due to the compression leads to the ignition of the air/fuel mixture without requiring a spark.
It looks like you got a physics lesson.
Speaker manufacturers do make efforts to dissipate heat or reduce operating temperature. Using thicker wire in the voice coil is the simplest way to reduce temperature, but it comes with obvious drawbacks. Venting the voice coil helps dissipate heat, a little.
The most effective way to address heat is to make the speaker more efficient.
I've seen tweeters with heat sinks before. Of course, ferrofluid is the most effective way to protect tweeter voice coils from burning up.
Speaker manufacturers do make efforts to dissipate heat or reduce operating temperature. Using thicker wire in the voice coil is the simplest way to reduce temperature, but it comes with obvious drawbacks. Venting the voice coil helps dissipate heat, a little.
The most effective way to address heat is to make the speaker more efficient.
I've seen tweeters with heat sinks before. Of course, ferrofluid is the most effective way to protect tweeter voice coils from burning up.
That's precisely what would be needed to fully explain the meaning of 'adiabatic'!
The air in a sealed enclosure obeys the 'Gas Laws' Gas laws - Wikipedia. Only in an isothermal setting does the product of pressure and volume remain constant, allowing the compression and expansion of the air to remain linear. In an adiabatic setting, the compression and expansion is non-linear
Unfortunately, jimmyjoe wants it kept simple.
P.S. The generation of heat in the voice coil is a separate issue from the generation of heat in the air inside the enclosure due to compression and expansion.
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