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.
Last edited:
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.