Keep in mind that the only two variables here are temperature and humidity.
Although humidity isn't even directly related to the pressure of a gas in a certain volume.
It only changes composition of the gas in a certain volume (the mix so to speak).
Difference in temperature is directly proportional to the pressure of a gas inside a specific volume.
Speaker cones are VERY poor heat/temperature insulators, so we can assume that temperature within the cabinet is the same as the temperature outside the cabinet.
In fact, aluminum cones are very good in transferring heat 😉
It is just a matter of time to bring that to a equilibrium.
I very much doubt if that process is slower than (slow) temperature changes during the day/in your room.
So the only other variable could be humidity.
Although a part would be already absorbed by the wood as well as the cone/surround (and be evaporated on the other side).
Even if we leave the porosity out of the equation, this would only be a problem when you mount the speaker (assuming it is a perfect seal), in a totally different environment and than all of a sudden bring it to your room.
Although in that case a much lower temperature would also effect a lot of other things as well.
So in a perfect seal situation with perfect insulation, this could only cause an issue when you assemble your speaker in a VERY cold shed and immediately bring it into a nice toasty warm room or vice versa.
It has been ages that I directly worked with thermodynamic equations, but we can even estimate and calculate that offset, assuming a certain difference in pressure.
It does leave a very different question that has not been raised (also not by Linkwitz).
When we put out a lot of SPL, the motor/speaker warms up and therefor the air inside the cabinet warms up.
This temperature can be a lot higher than the temperature outside the cabinet (the living room).
Especially because there is no forced air coming in/going out, so it all has to go trough convection.
So that basically means that the pressure within the cabinet goes up, putting a theoretical offset on the cone (again, assuming it's a perfect seal). A tiny pin hole is also not gonna help with that.
Interesting how quickly you can get into a rabbit hole, hahaha 😀 😀 😀
Although humidity isn't even directly related to the pressure of a gas in a certain volume.
It only changes composition of the gas in a certain volume (the mix so to speak).
Difference in temperature is directly proportional to the pressure of a gas inside a specific volume.
Speaker cones are VERY poor heat/temperature insulators, so we can assume that temperature within the cabinet is the same as the temperature outside the cabinet.
In fact, aluminum cones are very good in transferring heat 😉
It is just a matter of time to bring that to a equilibrium.
I very much doubt if that process is slower than (slow) temperature changes during the day/in your room.
So the only other variable could be humidity.
Although a part would be already absorbed by the wood as well as the cone/surround (and be evaporated on the other side).
Even if we leave the porosity out of the equation, this would only be a problem when you mount the speaker (assuming it is a perfect seal), in a totally different environment and than all of a sudden bring it to your room.
Although in that case a much lower temperature would also effect a lot of other things as well.
So in a perfect seal situation with perfect insulation, this could only cause an issue when you assemble your speaker in a VERY cold shed and immediately bring it into a nice toasty warm room or vice versa.
It has been ages that I directly worked with thermodynamic equations, but we can even estimate and calculate that offset, assuming a certain difference in pressure.
It does leave a very different question that has not been raised (also not by Linkwitz).
When we put out a lot of SPL, the motor/speaker warms up and therefor the air inside the cabinet warms up.
This temperature can be a lot higher than the temperature outside the cabinet (the living room).
Especially because there is no forced air coming in/going out, so it all has to go trough convection.
So that basically means that the pressure within the cabinet goes up, putting a theoretical offset on the cone (again, assuming it's a perfect seal). A tiny pin hole is also not gonna help with that.
Interesting how quickly you can get into a rabbit hole, hahaha 😀 😀 😀
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Thanks 🙂
In the other thread [ https://www.diyaudio.com/community/threads/compact-low-cost-active-3-way-speaker.402812/post-7440893 ] I will soon be requesting thoughts/advice/experience on drivers... In my previous projects, the selection of available drivers with the required performance was so limited, the drivers almost selected themselves... But with this project there are a LOT of options, so I will be getting (and appreciating) many opinions.
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Joined 2003
Unfortunately Scan-Speak Discovery 22W increased in price 30% this year. Great woofer though., I used in a TL for the bottom end of a 3-way, details here: https://www.htguide.com/forum/forum/mission-possible-diy/947504-disco-on-the-floor-p
8” with a full copper sleeve:
https://sbacoustics.com/product/8in-sb20frpc30-8-paper/
Based on impedance curve, and inductance control, H3 and higher order harmonics including IMD, I would use it from 150 Hz to ~800Hz with confidence.
Bottom 3 octaves in an extensible 3 way?
Use them in parallel or series parallel to increase Vd and sensitivity. Or use the non-full range model (no demodulation device)
https://www.madisoundspeakerstore.c...sb20pfcr30-4-8-paper-cone-woofer-4-ohm-round/
https://sbacoustics.com/product/8in-sb20frpc30-8-paper/
Based on impedance curve, and inductance control, H3 and higher order harmonics including IMD, I would use it from 150 Hz to ~800Hz with confidence.
Bottom 3 octaves in an extensible 3 way?
Use them in parallel or series parallel to increase Vd and sensitivity. Or use the non-full range model (no demodulation device)
https://www.madisoundspeakerstore.c...sb20pfcr30-4-8-paper-cone-woofer-4-ohm-round/
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They sound good actually. I have used these extensively over the past few months and can say they are generally liked well by the people who listen to them. They measure quite well too, and are quite tolerant to crossover design flaws. Here is the picture of a speaker I am working on currently using 4 sds 6.5 inches woofers per side, and early measurements shows a fairly decent graph with spl over 100 overall, and a pleasing sound stage. Currently I am running these active and once I am able to design a passive crossover and finish it to a high gloss polish, will perhaps start a thread on these. The boxes are curved double layered and weigh over a 100 kg each, and I had professional help from carpenters, so cannot say these are really easily diy. But I guess they will not sound bad in a flat rectangular box too. The mtm is sds 5.5inches and a peerless tweeter.
SDS-160F25PR01-08, NLA it seems. Though I have 4x to play with still. Thinking to try them isobaric to fill the bottom end of a compact 3-way tower.
Also just acquired an additional pair of mcm 55-5670s for two pair total, Possibly to combine with some Dayton PM180s and Peerless DX25BG60s. 😈
Also just acquired an additional pair of mcm 55-5670s for two pair total, Possibly to combine with some Dayton PM180s and Peerless DX25BG60s. 😈