Don, would you be able to share a drawing showing the positions and dimensions of the bass-reflex ports, and a list of the changes in the xover? I might add these details to the OSMC paper, so that everything is available from one document.
M,
Sorry. No drawings. I just followed the recommendations on this thread. The changes were all confirmed by the guru group.
In a nutshell, The changes for the project were:
1. Speaker volume 101L All built into the height dimension.
2. Ports and placement 2 - 4"dia ports 24cm long to start. Placement at volume height midpoint. In my case 433mm. Equally spaced from side to side. That is the distance between the side walls to tubes and space between tubes were all equal.
3. Total xover changes. LM2 .39mH. This is an independent change from original suggested by Matthias. And, CW3 320uF and LW4 18mH Changes recommend for the volume change.
Thats it. All changes came from the thread and were discussed and confirmed (I believe).
Regards,
Don
Hello mbrennwa,
I am planning an adaptation of the OSMT with the baffle size width but standalone cabinet of 80 cm heigth for the Faital. Mid and tweeter will be in a stacked cabinet. Vb of this thread so 107 l without the brassing.
Do you remember please what was the on axis circa 500 hz on axis cut-off with the filter please ? I.e. : after the BSC. I read something near 88,5 dB on axis 2,8V at 1 m on your OSMC paper...but I am not sure!
As I can not affoard the Volt I am trying to find a mid and need the lowest spl efficienty I can choose from a driver that your cut-off permit on axis. I assume if the 88,5/2,8V is ok then such a mid could be chosen with no needs of the mid serie resistor of the mid filter section. Am I correct ? Thinked of the Peereless papyrus ne149W for instance or maybe audioteknology 5" mid.
Thanks for your feeling on that 88.5 db or ? As it is not an entirely OSMT I can if you prefer input elswhere not to pollute ?
I am planning an adaptation of the OSMT with the baffle size width but standalone cabinet of 80 cm heigth for the Faital. Mid and tweeter will be in a stacked cabinet. Vb of this thread so 107 l without the brassing.
Do you remember please what was the on axis circa 500 hz on axis cut-off with the filter please ? I.e. : after the BSC. I read something near 88,5 dB on axis 2,8V at 1 m on your OSMC paper...but I am not sure!
As I can not affoard the Volt I am trying to find a mid and need the lowest spl efficienty I can choose from a driver that your cut-off permit on axis. I assume if the 88,5/2,8V is ok then such a mid could be chosen with no needs of the mid serie resistor of the mid filter section. Am I correct ? Thinked of the Peereless papyrus ne149W for instance or maybe audioteknology 5" mid.
Thanks for your feeling on that 88.5 db or ? As it is not an entirely OSMT I can if you prefer input elswhere not to pollute ?
Hi guys,
On the process to build the OSMT load for the Faital 12PR320. Project going slowly because the mid and treble would differe but that is for another thread (thanks Matthias for the PM on my basic beginner question from above 🙂 ).
So 101 L + 6 litres circa for the two ports space and drivers/sealed mid load if needed. I keep the idea of external passive filter box from the OSMC.
I re read the datasheet from Faital yesterday nigth and saw it changed sligthy : VAS is now 113 liters, the others T&S are the same. Noob question, does it changes the OSMT cabinet liters if Faital sligthy changed their production parameters on that unit ? I purchased mine few weeks ago.
Or should I measure the impedance of my two units with my Arta box and try a T&S measurement after breaking in ? Which is bringing me to another question to @Paul Vancluysen , @mbrennwa and @KaffiMann : Does one design with T&S took from a sligthy hot unit for the box load because when playing back music, the driver will get hot fast anyway ? I assume most Qms change is comming from the speeder annd voice coil get hotter than room temperature. Not knowing if it is cutting hair in 4, but my average target room is 23°/24° Celsius.
But that's maybe off topic here, just want to know, please, if the new VAS of the datasheet changes the 107L cabinet target (so port design too) for cutting the wood first ?
Many thanks for your thougths on this.
On the process to build the OSMT load for the Faital 12PR320. Project going slowly because the mid and treble would differe but that is for another thread (thanks Matthias for the PM on my basic beginner question from above 🙂 ).
So 101 L + 6 litres circa for the two ports space and drivers/sealed mid load if needed. I keep the idea of external passive filter box from the OSMC.
I re read the datasheet from Faital yesterday nigth and saw it changed sligthy : VAS is now 113 liters, the others T&S are the same. Noob question, does it changes the OSMT cabinet liters if Faital sligthy changed their production parameters on that unit ? I purchased mine few weeks ago.
Or should I measure the impedance of my two units with my Arta box and try a T&S measurement after breaking in ? Which is bringing me to another question to @Paul Vancluysen , @mbrennwa and @KaffiMann : Does one design with T&S took from a sligthy hot unit for the box load because when playing back music, the driver will get hot fast anyway ? I assume most Qms change is comming from the speeder annd voice coil get hotter than room temperature. Not knowing if it is cutting hair in 4, but my average target room is 23°/24° Celsius.
But that's maybe off topic here, just want to know, please, if the new VAS of the datasheet changes the 107L cabinet target (so port design too) for cutting the wood first ?
Many thanks for your thougths on this.
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I really do not think so. Most people are likely to hover below 1W max in daily use. Even if you go crazy and break out 10W for each driver to get closer to 103-110dB (pending on local conditions) at listening position a few meters away it is not worth the math to calculate the losses.
If you get wasted on too much cognac and after considerable consumption decide that the volume knob is a switch then the driver might see perhaps 100W provided you have a really big amplifier, remember there's losses from filters and some of the energy also goes to the other drivers, 100W total power to the driver is not really that much in terms of thermal compression. You can't feed the driver much more than this because the design is with only 1x12" driver and it does have limited xmax.
I guesstimate you'd stay below 1db thermal compression loss even after playing quite loud for a longer period of time, if you are really trying to push it hard to extensively test some limits (please go out of the room to protect those wrinkley shaped listening devices attached to your head) then you might approach 70W worth of heat.
Remember that if this driver is getting more power from the amp to "flap about" then it will also have more power to cool itself off because of the "flapping about". It will get a bit warm but not likely too hot to touch.
This driver is very efficient, it is able to produce a lot of sound from just 1W of power from the amplifier. You are not likely to ever get problems with thermal compression is this particular design.
Just eyeballing the spec sheet (no calculations) I am not concerned about the changes in T/S parameters.
It is not significant enough to make changes in the designs IMO.
If you want to build a PA rig for a band or a nightclub then I would advise you to look at other designs.
To sum it up:
Heat loss = Insignificant
Change in T/S parameters = Insignificant
Hey, you guys that have built this, how loud are you playing them?
I sincerely doubt anyone is feeding these drivers much more than perhaps 10W when listening loud, it is not unlikely that the heat generated in the passive filters will have a bigger impact on performance than the heat of the voice coil.
The main temperature effect I observed with the Faital woofer is in the compliance of the surround, which is not related to the motor heat. For more details see the OSMC thread.
Ok, no changes for the volume cab between 98l and 113l new datasheet Vas.
Good to know as I am going for the OMST 107l 38hz fb faital cab.
Anyway I keep the Cognac barel too anyway. Too bad I can not affoard the Volt...I will ask elswhere as OT here.
Thanks guys for the hints.
Good to know as I am going for the OMST 107l 38hz fb faital cab.
Anyway I keep the Cognac barel too anyway. Too bad I can not affoard the Volt...I will ask elswhere as OT here.
Thanks guys for the hints.
Hello, I have gotten some questions on this from time to time.
IMO the interesting bit starts here:
https://www.diyaudio.com/community/threads/open-source-monkey-tower.349736/post-6549477
I am a bit hesitant to give people direct answers to their replies, because I think learning is a crucial and very rewarding experience in itself.
So you will find me giving a nudge here and there, and people managing to find the solutions with a minimum of help, the only thing the previous result in this thread did not incorporate was a slight correction in tuning and they ended up with 24cm double 4" ports rather than my suggested 27cm double 4" ports, not a huge deal but it does have a slight impact on the end result.
If you want me to give you my personal opinion on optimal design for this driver, I can do that.
However, I never liked the forced format of the OSMC project, so you will see the horrible wiggles up top, they are unavoidable because of the other design choices.
If you want the quick and dirty of it, here you go, a tower.
You can smooth it out in your mind, the wrap at 195Hz is a wiggled line in real life, I still don't like it.
Edit:
Thoughts on bracing:
I usually look at the size of the chamber, think where the box resonances might influence the materials of the box along length and width. Calculate how much material I need to place throughout including central bracing structure and some bits to stiffen the long and wide parts of the ply box.
Then I subtract that volume from the cross sectional segments. Don't over complicate it, most people think too hard about bracing.
With a box that has basically dealt with most internal resonances in the design phase you can simplify it quite a bit, you only have to think about the resonances that can make the box materials resonate.
Another aspect is to push the potentially resonant behaviour of the box materials out of the intended passband for the driver. If you're going for a 500hz xo, try to keep it smooth a bit more than that.
Stiffening a box with braces usually push the resonance UP, so for a tweeter or mid it sometimes might be more beneficial to lower or just dampen any resonances.
Thoughts on dampening material:
1. Use loose thick wool felt in the gap between the ports and the "floor" of the box, be sure to have a bit of area around the port aperture to let it breathe. Try to get the ports away from the internal walls, unless you are consciously making a design where you integrate ports as part of the bracing structure.
2. Melamine foam glued to the side walls, 2-3cm is probably enough. FYI the "magic sponge" is commonly melamine foam, and sometimes it can be cheaper to find a place with good discounts on a big bag of those than ordering the proper stuff from a specialty shop or ebay when you calculate shipping etc. Also you get "instant gratification", which can be nice sometimes.
Don't overdo the dampening thing, it should be something you use to apply a minor finishing touch to add a slight refinement, dampening material is not a crutch you can use to save a horrible design.
IMO the interesting bit starts here:
https://www.diyaudio.com/community/threads/open-source-monkey-tower.349736/post-6549477
I am a bit hesitant to give people direct answers to their replies, because I think learning is a crucial and very rewarding experience in itself.
So you will find me giving a nudge here and there, and people managing to find the solutions with a minimum of help, the only thing the previous result in this thread did not incorporate was a slight correction in tuning and they ended up with 24cm double 4" ports rather than my suggested 27cm double 4" ports, not a huge deal but it does have a slight impact on the end result.
If you want me to give you my personal opinion on optimal design for this driver, I can do that.
However, I never liked the forced format of the OSMC project, so you will see the horrible wiggles up top, they are unavoidable because of the other design choices.
If you want the quick and dirty of it, here you go, a tower.
You can smooth it out in your mind, the wrap at 195Hz is a wiggled line in real life, I still don't like it.
Edit:
Thoughts on bracing:
I usually look at the size of the chamber, think where the box resonances might influence the materials of the box along length and width. Calculate how much material I need to place throughout including central bracing structure and some bits to stiffen the long and wide parts of the ply box.
Then I subtract that volume from the cross sectional segments. Don't over complicate it, most people think too hard about bracing.
With a box that has basically dealt with most internal resonances in the design phase you can simplify it quite a bit, you only have to think about the resonances that can make the box materials resonate.
Another aspect is to push the potentially resonant behaviour of the box materials out of the intended passband for the driver. If you're going for a 500hz xo, try to keep it smooth a bit more than that.
Stiffening a box with braces usually push the resonance UP, so for a tweeter or mid it sometimes might be more beneficial to lower or just dampen any resonances.
Thoughts on dampening material:
1. Use loose thick wool felt in the gap between the ports and the "floor" of the box, be sure to have a bit of area around the port aperture to let it breathe. Try to get the ports away from the internal walls, unless you are consciously making a design where you integrate ports as part of the bracing structure.
2. Melamine foam glued to the side walls, 2-3cm is probably enough. FYI the "magic sponge" is commonly melamine foam, and sometimes it can be cheaper to find a place with good discounts on a big bag of those than ordering the proper stuff from a specialty shop or ebay when you calculate shipping etc. Also you get "instant gratification", which can be nice sometimes.
Don't overdo the dampening thing, it should be something you use to apply a minor finishing touch to add a slight refinement, dampening material is not a crutch you can use to save a horrible design.
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Hello again everyone, apologize for the double hammering and lengthy posts...
@gbowling I hope it is allright for me to post some of your pictures, you made up to this date THE BEST variation of the OSMC project.
After a bit of input and a few nudges here and there. he ended up making quite a different design while retaining some crucial key elements.
Gabo did it all himself, absolutely everything, and in my usual style I just gave him a gentle nudge here and there to help his thoughts wander off in the right direction.
He did this as part of a custom solution for a studio. If I remember correctly the tops are built-in the walls, fully integrated.
Here is what he sent me as the results of his process, great guy, great results.
However.....
Because I never gave him anything except a little bit of help, there is still a small amount of performance to squeeze out of this design.
I apologize Gabo, please forgive me, just a bit smoother and a bit deeper, the big difference is the group delay around 40Hz, it makes a big difference in perception of bass articulation.
If you do not care about power handling (that much), and you have about 150 completely squeaky clean watts on tap though you only need a bit over 100 of them, this is what is possible:
I think that is just about the most one can expect out of this membrane area, need more? Maybe you should consider a different project.
For the US population that is "A Hunnerd'nTen deebeez @ thurdy hurtz!" from a single 12" in halfspace, smooth to 1kHz.
I would cross it over around 600Hz.
@gbowling I hope it is allright for me to post some of your pictures, you made up to this date THE BEST variation of the OSMC project.
After a bit of input and a few nudges here and there. he ended up making quite a different design while retaining some crucial key elements.
Gabo did it all himself, absolutely everything, and in my usual style I just gave him a gentle nudge here and there to help his thoughts wander off in the right direction.
He did this as part of a custom solution for a studio. If I remember correctly the tops are built-in the walls, fully integrated.
Here is what he sent me as the results of his process, great guy, great results.
However.....
Because I never gave him anything except a little bit of help, there is still a small amount of performance to squeeze out of this design.
I apologize Gabo, please forgive me, just a bit smoother and a bit deeper, the big difference is the group delay around 40Hz, it makes a big difference in perception of bass articulation.
If you do not care about power handling (that much), and you have about 150 completely squeaky clean watts on tap though you only need a bit over 100 of them, this is what is possible:
I think that is just about the most one can expect out of this membrane area, need more? Maybe you should consider a different project.
For the US population that is "A Hunnerd'nTen deebeez @ thurdy hurtz!" from a single 12" in halfspace, smooth to 1kHz.
I would cross it over around 600Hz.
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Well... Define "huge". I guess you could call my previous speakers "huge", personally I think they were "adequate", perhaps even downright "small" if given a specific perspective.
It is not a tower, that much I can tell you.
It is not a tower, that much I can tell you.
Because you do not have to change anything else if you do it right.
This is for a specific design, the OSMC, and I was asked a specific question through PM, thought it was better to get everything out in the open.
The topic was "optimal design", and it pops up from time to time.
Other than that, I aired that very same question you just asked very early in the design process.
This is for a specific design, the OSMC, and I was asked a specific question through PM, thought it was better to get everything out in the open.
The topic was "optimal design", and it pops up from time to time.
Other than that, I aired that very same question you just asked very early in the design process.
@KaffiMann no worries in posting anything I did. I'm flattered by your comments! I had a great time with this project and you taught me a lot about how to use hornresp, something I struggled with until you helped me understand some of the nuances. I'm still not as comfortable using it as you are, but I can get by doing what I need to do if I have a bit of time.
Those speakers are still in the studio, the owner of the studio absolutely loves them. They get driven very hard every day, this studio does all types of music and film but does do quite a lot of metal and they drive some pretty extreme SPL's for long periods of time.
The speakers were a part of a much bigger overall design that included room treatment, studio console designs, and many other things. Not only does the owner love it all, but I get to do "drum sessions" there a lot and get to enjoy the entire experience. Thanks for the memories.
gabo
Those speakers are still in the studio, the owner of the studio absolutely loves them. They get driven very hard every day, this studio does all types of music and film but does do quite a lot of metal and they drive some pretty extreme SPL's for long periods of time.
The speakers were a part of a much bigger overall design that included room treatment, studio console designs, and many other things. Not only does the owner love it all, but I get to do "drum sessions" there a lot and get to enjoy the entire experience. Thanks for the memories.
gabo
Thank you for sharing Gabo, hope you have a good time over there.
Too busy to build stuff myself right now so the next setup will probably be in collaboration with a local carpenter, it will be more modular but not smaller.
.... Was that looking at the sim or were you talking about my previous 3x15" boxes?
Too busy to build stuff myself right now so the next setup will probably be in collaboration with a local carpenter, it will be more modular but not smaller.
I'm referring to Gabo's bass boxes you posted the photos of with the sims. This is much larger than the original design, yes? And presumably a different port tuning?
To make such a good box without leaks is not for basic wook workers ! 🙂
I wonder if some of the owners had made a THD measurement til H5 of the PR320 in and out the cabinet since ?
How to get rid of that first 200/250 hz wiggle, please ? More damping resistor after the shunt capacitor of a 12 dB low pass ? foam ? passive notch ? Or anyway one will hear it ?
I wonder if some of the owners had made a THD measurement til H5 of the PR320 in and out the cabinet since ?
How to get rid of that first 200/250 hz wiggle, please ? More damping resistor after the shunt capacitor of a 12 dB low pass ? foam ? passive notch ? Or anyway one will hear it ?