It is an act of balance.
The port provides a resistant coupling between the internal volume and the room, while the driver pumps air, creating vacuum and pressure in both the room and the internal volume constantly. The port has a frequency where it creates such resistance that the driver will hardly move at all, this is fs, the resonace of the port, where the port will create more sound than the driver because of the coupling resonance. The port should not cause the air to move too fast, because like with fluids, air has turbulence, and vortexes, sometimes far away from corners and angles. Creating even more disturbance to the rest of the air, further modifying resistance.
Also the distance from driver to the internal walls of the enclosure should be kept to near-equal distance, this is an alternative to skewing the walls making them un-parallel to reduce internal resonance which can be very difficult to do right. The reason to keep short distance to internal walls, is to push resonant behaviour high enough up in frequency that it is easier to dissipate with damping material, needing less damping material than you would to dampen lower frequencies, sort of "tiring out" the faults of the sound.
These things are very basic, but it's taken me hundreds of hours to understand it, there was no book.
I have had books, and read a lot some times, but really understanding what is going on can be very difficult.
The port provides a resistant coupling between the internal volume and the room, while the driver pumps air, creating vacuum and pressure in both the room and the internal volume constantly. The port has a frequency where it creates such resistance that the driver will hardly move at all, this is fs, the resonace of the port, where the port will create more sound than the driver because of the coupling resonance. The port should not cause the air to move too fast, because like with fluids, air has turbulence, and vortexes, sometimes far away from corners and angles. Creating even more disturbance to the rest of the air, further modifying resistance.
Also the distance from driver to the internal walls of the enclosure should be kept to near-equal distance, this is an alternative to skewing the walls making them un-parallel to reduce internal resonance which can be very difficult to do right. The reason to keep short distance to internal walls, is to push resonant behaviour high enough up in frequency that it is easier to dissipate with damping material, needing less damping material than you would to dampen lower frequencies, sort of "tiring out" the faults of the sound.
These things are very basic, but it's taken me hundreds of hours to understand it, there was no book.
I have had books, and read a lot some times, but really understanding what is going on can be very difficult.
Last edited:
That is entirely up to you.
The 2cm port gives you a flat response to a point you should cross over to a sub.
The 1.5cm port gives you a rolled-off response/gradually less sound to a lower point in frequency, it might be that it's just as easy to cross over to a sub, but you might also be happy without a sub.
Edit:
What melody would it be if it's a song?
The 2cm port gives you a flat response to a point you should cross over to a sub.
The 1.5cm port gives you a rolled-off response/gradually less sound to a lower point in frequency, it might be that it's just as easy to cross over to a sub, but you might also be happy without a sub.
Edit:
What melody would it be if it's a song?
Last edited:
Song
Alanis Morset comes to mind. What’s going on
I am going to try to go for the high r narrower vent. Does it mater if the vent shelf in the back is just squared off or would a round over be better. Laminar flow, smoother transition, etc. I did take fluid power in college (tech drafting and tool design) back in the 70’s but most has been forgotten.
Alanis Morset comes to mind. What’s going on
I am going to try to go for the high r narrower vent. Does it mater if the vent shelf in the back is just squared off or would a round over be better. Laminar flow, smoother transition, etc. I did take fluid power in college (tech drafting and tool design) back in the 70’s but most has been forgotten.
Another final question!
I will probably make it out of 1/2” plywood that is actually .475 thick. I will keep the internal dimensions and adjust the externals for the .475 thickness. Along with the end rounded or squared off-do I need to add in the missing thickness to the vent shelf to get the exact internal volume as in your drawing?
I will try to find true quality 5/8” finished plywood but I don’t recall there being any at the two big box stores? The other reason besides availability is that I am building the GF new kitchen cabinets out of the 1/2” Baltic birch and will be easier to hide the speakers in the cuts for cabinets! She is suspicious, asks me what’s in that box, what did you order NOW when a delivery comes in! Lol, life is a game that is hard won! But worth it
I will probably make it out of 1/2” plywood that is actually .475 thick. I will keep the internal dimensions and adjust the externals for the .475 thickness. Along with the end rounded or squared off-do I need to add in the missing thickness to the vent shelf to get the exact internal volume as in your drawing?
I will try to find true quality 5/8” finished plywood but I don’t recall there being any at the two big box stores? The other reason besides availability is that I am building the GF new kitchen cabinets out of the 1/2” Baltic birch and will be easier to hide the speakers in the cuts for cabinets! She is suspicious, asks me what’s in that box, what did you order NOW when a delivery comes in! Lol, life is a game that is hard won! But worth it
If you want to get really pedantic/anal not all 1/2" veneer core plywood is exactly 12.7mm. I've used the Russian 5x5, "EuroPly" 4x8 and Murphy Multi-ply with maple face veneers- within which group can measure with calipers at between 12.14 - 12.4mm. All less than 1/2", but that'd really only be significant with a manifold designs with a lot of corners where the differences could concatenate to a large fraction of an inch.
One of the advantages of MDF is its precise uniform thickness - until it's exposed to moisture , but always, always measure the actual thickness of veneer core plywood and adjust cut plans as necessary.
One of the advantages of MDF is its precise uniform thickness - until it's exposed to moisture , but always, always measure the actual thickness of veneer core plywood and adjust cut plans as necessary.
You want to hear some funny? In a hurry this morn to figure box size so I can have big box rip to size, I hurriedly wrote up cut list for internal dimensions! Girlfriend was rushing me. Come home, she left for hair cut, I cut up all panels for the K56BR to the internal dimensions!! Now I am short material.
But I have all panels cut for my cPlu-ken7 done except vent spacer and driver cutout. Drivers just came too! She not back from haircut, so covert operation still intact.
But I have all panels cut for my cPlu-ken7 done except vent spacer and driver cutout. Drivers just came too! She not back from haircut, so covert operation still intact.
Why is it that whenever you are in the middle of something, the wife/girlfriend/whatever seem to have some sudden urge to dump a huge completely irrellevant load on you then rush off?
I am planning to get some stuff done after coming home from work today, and I am certain she will start trying to shift my focus to everything else, even though what I am planning to do has the biggest benefit for us all.
Edit:
Measurements, this is why I count 0.5mm extra for each glued joint on external dimensions. It's a "guesstimate" measurement that sort of just works (at least for me) every time. So for instance from outside sidewall to the other outside sidewall add 1mm.
I am planning to get some stuff done after coming home from work today, and I am certain she will start trying to shift my focus to everything else, even though what I am planning to do has the biggest benefit for us all.
Edit:
Measurements, this is why I count 0.5mm extra for each glued joint on external dimensions. It's a "guesstimate" measurement that sort of just works (at least for me) every time. So for instance from outside sidewall to the other outside sidewall add 1mm.
Last edited:
the cat is out of the bag! Hey Kent, yes making sawdust, but not on speakers! She saw the poorly hidden panels of the speakers pilled up in the garage! Tried to say they were scraps but she said, "they look like speaker to me"? I can not tell a lie, so I spilled my guts. She was not happy. I said that they are for computer speakers to replace the ones "you never liked". Did'nt help much-BUT cutting wood for her new kitchen cabinets did! so, I am assembling speaker boxes AND building cabinets. I was glueing up the first one yesterday afternoon and she said..."what are you doing"? I said gluing up a speaker. She said that I should be working on cabinets!!! so, might be a few weeks. Both drivers are being broken in tho.
WHere do I get the 1/2 inch wool felt for dampening from?
WHere do I get the 1/2 inch wool felt for dampening from?
Your entire post is brilliant.
----------------------------------------------
'Skydiving'
Wingsuits, are another matter altogether.
Once the initial fear, subsides, teh fems,
might not be able to stop -
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Last edited:
Some carpet padding, was felt.
May still be, tho I'm not sure that any still is available.
I got really good quality wool felt from a large knitting and sewing equipment shop. They had huge rolls of it in the back, ask around.
Edit:
May be easier to get some open cell foam from a hardware shop somewhere though.
Edit2:
Chrisb: ..... ok. So you want to ride a guy with a wingsuit?
I'm not judging. To each their own.
Edit:
May be easier to get some open cell foam from a hardware shop somewhere though.
Edit2:
Chrisb: ..... ok. So you want to ride a guy with a wingsuit?
I'm not judging. To each their own.
Last edited:
dampening material
ok, can't close up the box until i add dampening material. I don't have a knitting and sewing center here near me. I check online and the wool felt is crazy expensive! I have a ton of polyfill pillow stuffing? can I compact it somehow and line the interior walls with it? I thought about getting wool carpeting? still pricey tho. I did some other speakers with the foam carpet padding but don't know if it was effective or not?
any ideas? specs are for 1/2"wool on the MA enclosure. Kent what do you spec for the TB?
ok, can't close up the box until i add dampening material. I don't have a knitting and sewing center here near me. I check online and the wool felt is crazy expensive! I have a ton of polyfill pillow stuffing? can I compact it somehow and line the interior walls with it? I thought about getting wool carpeting? still pricey tho. I did some other speakers with the foam carpet padding but don't know if it was effective or not?
any ideas? specs are for 1/2"wool on the MA enclosure. Kent what do you spec for the TB?
Wool felt is pricy, yes.
Open cell foam can be had anywhere, this might be a bit thick, but a nice example what to look for:
https://www.walmart.com/ip/12-Pack-Acoustic-Panels-Studio-Foam-Wedges-1-X-12-X-12/162041259
Just find something similar, somewhere between 1/2" to 1" thick sounds about right. 1" may work well, not sure. It's not too expensive to try?
Edit:
Covering: Bottom, sides, 3/4ths of the back should be enough. Experiment.
Open cell foam can be had anywhere, this might be a bit thick, but a nice example what to look for:
https://www.walmart.com/ip/12-Pack-Acoustic-Panels-Studio-Foam-Wedges-1-X-12-X-12/162041259
Just find something similar, somewhere between 1/2" to 1" thick sounds about right. 1" may work well, not sure. It's not too expensive to try?
Edit:
Covering: Bottom, sides, 3/4ths of the back should be enough. Experiment.
Last edited:
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.