Some loose change
Thank you for posting this Freddi,
That front shelf does alter things a little bit
A measurement with the mic on-axis probably would have been smoother but this is still helpful , and i can see that using shelves as a way to semi-divide up the chambers (into 3 or 4 instead of 2) might be worth tinkering around with in Akabak ....... Yes, as you say those shelves must also shift the tuning down by some amount, so the main interchamber vent wouldn't need to be as long .. Hmmm, I might try this with an ML-Transflex script ..
Thank you for posting this Freddi,
That front shelf does alter things a little bit
A measurement with the mic on-axis probably would have been smoother but this is still helpful , and i can see that using shelves as a way to semi-divide up the chambers (into 3 or 4 instead of 2) might be worth tinkering around with in Akabak ....... Yes, as you say those shelves must also shift the tuning down by some amount, so the main interchamber vent wouldn't need to be as long .. Hmmm, I might try this with an ML-Transflex script ..
NOTE
About the drivers recommended for the Karlflex cabinet (from the sketch in posts #1611 , #1631 & #1633).
I thought it was important to point out (something that most of the builders and enthusiasts may already know but) just in case someone may not be aware: The drivers recommended generally have tight suspensions and will require some break-in time in order to sound their best..
A clean 25hz sinewave signal with enough power to get the cone moving can be left overnight or more to get the job done, or at least this is how i have done it in the past, but other DIYaudio members have different methods ...
About the drivers recommended for the Karlflex cabinet (from the sketch in posts #1611 , #1631 & #1633).
I thought it was important to point out (something that most of the builders and enthusiasts may already know but) just in case someone may not be aware: The drivers recommended generally have tight suspensions and will require some break-in time in order to sound their best..
A clean 25hz sinewave signal with enough power to get the cone moving can be left overnight or more to get the job done, or at least this is how i have done it in the past, but other DIYaudio members have different methods ...
your Karlflex is an attractive alternative to reflex and kickbin and a K-flex has plenty of vent area reducing compression effect - I've considered an 80Hz folded horn but its designer thinks the curves with it weren't correct - a re-design would be 100Hz folded hypex using an ~65g mms B&C 12" - that horn would need a sub, midhorn, and tweeter - while the Karlflex could be functional 2-way could & use a horn or K-tube on top.
~5.1 cubic foot bulk for 15" driver Karlflex for B&C 15pzb40
~7.5 cubic foot bulk for 12" driver folded 100Hz hypex horn
~3.5 cubic foot bulk for 12" driver Karlflex for Dayton PA310-8
~5.1 cubic foot bulk for 15" driver Karlflex for B&C 15pzb40
~7.5 cubic foot bulk for 12" driver folded 100Hz hypex horn
~3.5 cubic foot bulk for 12" driver Karlflex for Dayton PA310-8
Value and portability considerations
You could have two 3.5 cubic foot Karlflex cabs and still take up less space than a single 100hz hypex horn .... The Karlflex set would also have much more bandwidth and bass extension ...
The compromise is that the Karlflex wont have the 105db @1w/1m efficiency like a large Front Loaded Midbass Horn might have, however using multiple Karlflex cabs loaded with cheap drivers really starts to stack efficiency and max output quickly as more cabs are added, and can really make a lot of sense in terms of dollar-per-decibel value, packspace and portability especially since you don't need extra subwoofer cabs or tops to go with them ......
I could probably fit up to 8 of the 60 liter Karlflex cabs loaded with Kappalite 3012LF into a compact car if the trunk , back seat and front passenger seat were all utilized ... That would be a formidable portable PA that is easy to handle without the need of a dolly/cart , is "back friendly" , could be powered by a single large stereo amp (if you wanted to) , and is capable of a theoretical 138 decibel output in halfspace!
You could have two 3.5 cubic foot Karlflex cabs and still take up less space than a single 100hz hypex horn .... The Karlflex set would also have much more bandwidth and bass extension
... The compromise is that the Karlflex wont have the 105db @1w/1m efficiency like a large Front Loaded Midbass Horn might have, however using multiple Karlflex cabs loaded with cheap drivers really starts to stack efficiency and max output quickly as more cabs are added, and can really make a lot of sense in terms of dollar-per-decibel value, packspace and portability especially since you don't need extra subwoofer cabs or tops to go with them ......
I could probably fit up to 8 of the 60 liter Karlflex cabs loaded with Kappalite 3012LF into a compact car if the trunk , back seat and front passenger seat were all utilized ... That would be a formidable portable PA that is easy to handle without the need of a dolly/cart , is "back friendly" , could be powered by a single large stereo amp (if you wanted to) , and is capable of a theoretical 138 decibel output in halfspace!
- if you have made or are making a K-tube, you might consider playing with a cardboard baffle at the compression driver plane so the lows from the tube don't fold back as much - tilt the tube up a bit - like the same angle as the woofer baffle - whatever angle blends and sounds the best overall - put something "soft" felt - bonded Dacron on top of the Karlflex to reduce bounce
It works
Freddi ,
That JBL M151 works ... Not as much extension or output as your B&C 15 but it is pretty solid down to 60hz with a shallow roll-off with about -3db to -4db down at 40hz ..... Would likely be best to shift the cabinet's FB up to 47hz-ish (plus or minus a few hertz) , and this is easily done since we have access to the interchamber vent (post build) .....
Due to the lower QTS and very high midrange efficiency it would probably have a somewhat midrange dominant sound ..... This might be a good candidate for use with K-wings and narrow slot above (a closer to classic K-box appearance) , i could say for sure if i could find an on-axis amplitude/response measurement for this driver but i searched google and did not have any luck ..
If you are wanting to go with the classic K-slot with wings (and a very narrow slot above driver reaching to the top of the front panel) I have a few drivers with the rising upper response in mind that could work such as the Kappa15LFA , or Kappalite 3015 or maybe a few others , For the most part these drivers also have the properties that will also result in a higher f3 and a bass contour that is more like the classic Karlson contour with more energy concentrated in the midbass and less output in the subbass range .......
Freddi ,
That JBL M151 works ... Not as much extension or output as your B&C 15 but it is pretty solid down to 60hz with a shallow roll-off with about -3db to -4db down at 40hz ..... Would likely be best to shift the cabinet's FB up to 47hz-ish (plus or minus a few hertz) , and this is easily done since we have access to the interchamber vent (post build) .....
Due to the lower QTS and very high midrange efficiency it would probably have a somewhat midrange dominant sound ..... This might be a good candidate for use with K-wings and narrow slot above (a closer to classic K-box appearance) , i could say for sure if i could find an on-axis amplitude/response measurement for this driver but i searched google and did not have any luck ..
If you are wanting to go with the classic K-slot with wings (and a very narrow slot above driver reaching to the top of the front panel) I have a few drivers with the rising upper response in mind that could work such as the Kappa15LFA , or Kappalite 3015 or maybe a few others , For the most part these drivers also have the properties that will also result in a higher f3 and a bass contour that is more like the classic Karlson contour with more energy concentrated in the midbass and less output in the subbass range .......
the approximate ground plane of this 80 liter 41Hz tuned reflex of M151 vs the B&C gives a rough idea - a K aperture might be a good thing if not too much of the driver is blocked
where is the 100 liter Karlflex tuned with just the top vent piece? both pieces?
where is the 100 liter Karlflex tuned with just the top vent piece? both pieces?
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.
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Freddi's drivers
Freddi,
From looking at these graphs it seems to me like the JBL probably has more motor strength than the Eminence C15CX ....
The JBL M151 also seems to be much louder between 70hz and 1.5khz but does not really have a rising upper-mid response in relation to your B&C ...
If i had to choose between all three of these drivers for usage in the Karlflex i would go with the B&C , especially if the box fundamental was tuned to 40hz ..... With the JBL i would tune higher ...
In the Karlflex (100L and otherwise) the tuning is adjusted by altering the interchamber duct ... (If you pull the driver out it gives you access to the interchamber vent/duct and holes could be cut into the bottom of that duct with a hole saw if you needed to drastically raise tuning , just be sure to avoid cutting right in the center where the brace is located) ....
NOTE ABOUT K-WINGS: You might be able to get away with obscuring the sides of the B&C with K-wings to some extent (more than you could with the JBL) ..
Freddi,
From looking at these graphs it seems to me like the JBL probably has more motor strength than the Eminence C15CX ....
The JBL M151 also seems to be much louder between 70hz and 1.5khz but does not really have a rising upper-mid response in relation to your B&C ...
If i had to choose between all three of these drivers for usage in the Karlflex i would go with the B&C , especially if the box fundamental was tuned to 40hz ..... With the JBL i would tune higher ...
In the Karlflex (100L and otherwise) the tuning is adjusted by altering the interchamber duct ... (If you pull the driver out it gives you access to the interchamber vent/duct and holes could be cut into the bottom of that duct with a hole saw if you needed to drastically raise tuning , just be sure to avoid cutting right in the center where the brace is located) ....
NOTE ABOUT K-WINGS: You might be able to get away with obscuring the sides of the B&C with K-wings to some extent (more than you could with the JBL) ..
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Motor strength comparisons for 12" drivers
Here are some 12" drivers and their respective motor strength values calculated from the BL^2/RE formula... These drivers can be loaded into the 60 liter Karlflex (13.5" width cabinet)...
Drivers with higher motor strength will have more output down near the fundamental tuning of a small cabinet (40hz is the default fundamental tuning in the Karlflex).
Drivers with low motor strength will produce a bump in the midbass response in exchange for some loss in the subbass range, in other words you will end up with a bottom-end contour that is less flat and more closely resembles the classic Karlson contour (higher F3).
Pro Drivers 12" ---------- Motor Strength
Eminence Beta 12a2 ------------23.33
Eminence DeltaliteII 2512 -------24.69 (with very low "Le" figure )
MCM 55-2992 ----------------- 32.00 (measured parameters with DATS)
Dayton PA310 -----------------48.52
Eminence Kappalite 3012LF----- 52.70
Eminence Definimax 4012HO-----73.75
PIONEER TS-W1200PRO ---------89.28 (higher Le)
This Pioneer Pro driver is an oddball, has a higher voicecoil inductance (Le) but not nearly as high as some of the car audio drivers, yet still enough to limit the midrange response (published specs say it is good out to 500hz , but i would like to see a measurement)....Extremely strong motor and extremely tight suspension according to the published parameters.... Might be a very good low-cost alternative to the Definimax, and simulates surprisingly well in a 100L 40hz Tapped Horn or a 60L Karlflex ...
I also have a couple of Car Audio style subwoofers that are good candidates for a bass-only Karlflex but i am going to try to stay focused on wider bandwidth combinations for the moment (if anyone really wants to know about the bass-only driver options just let me know)..
Here are some 12" drivers and their respective motor strength values calculated from the BL^2/RE formula... These drivers can be loaded into the 60 liter Karlflex (13.5" width cabinet)...
Drivers with higher motor strength will have more output down near the fundamental tuning of a small cabinet (40hz is the default fundamental tuning in the Karlflex).
Drivers with low motor strength will produce a bump in the midbass response in exchange for some loss in the subbass range, in other words you will end up with a bottom-end contour that is less flat and more closely resembles the classic Karlson contour (higher F3).
Pro Drivers 12" ---------- Motor Strength
Eminence Beta 12a2 ------------23.33
Eminence DeltaliteII 2512 -------24.69 (with very low "Le" figure
) MCM 55-2992 ----------------- 32.00 (measured parameters with DATS)
Dayton PA310 -----------------48.52
Eminence Kappalite 3012LF----- 52.70
Eminence Definimax 4012HO-----73.75
PIONEER TS-W1200PRO ---------89.28 (higher Le)
This Pioneer Pro driver is an oddball, has a higher voicecoil inductance (Le) but not nearly as high as some of the car audio drivers, yet still enough to limit the midrange response (published specs say it is good out to 500hz , but i would like to see a measurement)....Extremely strong motor and extremely tight suspension according to the published parameters.... Might be a very good low-cost alternative to the Definimax, and simulates surprisingly well in a 100L 40hz Tapped Horn or a 60L Karlflex ...
I also have a couple of Car Audio style subwoofers that are good candidates for a bass-only Karlflex but i am going to try to stay focused on wider bandwidth combinations for the moment (if anyone really wants to know about the bass-only driver options just let me know)..
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A little bit of deceptive marketing being used by Pioneer
Freddi ,
Exactly, and I think that was the idea, it was probably a marketing based decision and a tactful way to cover up the dip in the upper mids...
It also looks like they used the 1/8th space or "in vehicle" sensitivity figure so just subtract 10 decibels from their number , 95db @1w/1m is more like it ...
Another thing that seems out of place is the aluminum voicecoil former which is shown in that marketing diagram ...... A driver with an actual QMS figure of 10+ is probably using a non-conductive voicecoil former (perhaps it is a change that they made later) ...
I would love to put one of these TS-W1200PRO drivers on my DATS to see what is really going on with the T/S parameters .... If anyone in the Phoenix area owns one of these drivers please bring it over so i can measure it!!
An externally hosted image should be here but it was not working when we last tested it.
"if" this is representative then the Pioneer could probably to 500 - too bad the graphic covers the graph
Freddi ,
Exactly, and I think that was the idea, it was probably a marketing based decision and a tactful way to cover up the dip in the upper mids...
It also looks like they used the 1/8th space or "in vehicle" sensitivity figure so just subtract 10 decibels from their number
, 95db @1w/1m is more like it ...Another thing that seems out of place is the aluminum voicecoil former which is shown in that marketing diagram ...... A driver with an actual QMS figure of 10+ is probably using a non-conductive voicecoil former (perhaps it is a change that they made later) ...
I would love to put one of these TS-W1200PRO drivers on my DATS to see what is really going on with the T/S parameters .... If anyone in the Phoenix area owns one of these drivers please bring it over so i can measure it!!
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SO SYNCHRONOUS! (as Jung would say)
TB46,
THANK YOU!! Yes , this idea has come a long long way since this discussion started , and your contributions have helped this thing along for sure
I REALLY like your concept of experimenting with having a Freddi-mod style cavity/stub placed below the driver because it can still serve both purposes of taming harmonics (flattening response) and increasing the volume of the front chamber which i think will be very beneficial Instead of stacking multiple Freddi-Mods on the top of the box we could try the alternative of having one (or more) on top and one (or more) on the bottom.. ..
IT IS VERY SYNCHRONOUS that you suggest this idea, as just the other day Mr Sebastian Schlager showed me that he was experimenting with such a concept in one of his Karlflex scripts .... Maybe it is an idea who's time has come!
To answer your question about the aperture/slot i have tried wings to obscure the sides of the driver and i found that they can be a good thing if your driver has a rising upper-mid response, the result is a very well controlled horizontal dispersion (at the expense of upper-mid output) ... As XRK has stated: the slot forms a sort of acoustic "diffraction lens" ...... I would try the wings with a driver like the Kappalite 3012LF which is a fantastic choice because it has all of the necessary parameters to work well in a Karlflex and it also has the required rising upper-mid response to work well with wings right up to 2khz ...
Hi MMJ,
Amazing progress.
Have you ever tried the reduced size Karlson slot as in the drawing I posted in Post #1188, and can the stub be located at the bottom? See, attached sketch
Regards,
TB46,
THANK YOU!! Yes , this idea has come a long long way since this discussion started , and your contributions have helped this thing along for sure
I REALLY like your concept of experimenting with having a Freddi-mod style cavity/stub placed below the driver because it can still serve both purposes of taming harmonics (flattening response) and increasing the volume of the front chamber which i think will be very beneficial
Instead of stacking multiple Freddi-Mods on the top of the box we could try the alternative of having one (or more) on top and one (or more) on the bottom.. ..IT IS VERY SYNCHRONOUS that you suggest this idea, as just the other day Mr Sebastian Schlager showed me that he was experimenting with such a concept in one of his Karlflex scripts .... Maybe it is an idea who's time has come!
To answer your question about the aperture/slot i have tried wings to obscure the sides of the driver and i found that they can be a good thing if your driver has a rising upper-mid response, the result is a very well controlled horizontal dispersion (at the expense of upper-mid output) ... As XRK has stated: the slot forms a sort of acoustic "diffraction lens" ...... I would try the wings with a driver like the Kappalite 3012LF which is a fantastic choice because it has all of the necessary parameters to work well in a Karlflex and it also has the required rising upper-mid response to work well with wings right up to 2khz
...
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Hi MMJ,
Post #1657: "...I would try the wings with a driver like the Kappalite 3012LF which is a fantastic choice because it has all of the necessary parameters to work well in a Karlflex and it also has the required rising upper-mid response to work well with wings right up to 2khz."
That's good to know, it would also explain why drivers like the Fostex FE206E have been recommended for the general Karlson enclosures.
Regards,
Post #1657: "...I would try the wings with a driver like the Kappalite 3012LF which is a fantastic choice because it has all of the necessary parameters to work well in a Karlflex and it also has the required rising upper-mid response to work well with wings right up to 2khz."
That's good to know, it would also explain why drivers like the Fostex FE206E have been recommended for the general Karlson enclosures.
Regards,
