Hi Y'all,
Looking @ the chart MMJ posted in #1354, it would not surprise me to find, that the amplifier (signal chain) used for the measurement had a build-in HP filter set @ ~20Hz. The step from 35Hz to 30Hz is the first one that shows some excursion reduction v. the simulation, and from then on it's down hill. That would be pretty normal for e.g.: a 2nd order 20Hz HP. Anyway, w/o at least a simultaneously recorded voltage input preferrably measured @ the driver I would not trust this information.
MMJ, do you have a link to where you found the data?
Regards,
Looking @ the chart MMJ posted in #1354, it would not surprise me to find, that the amplifier (signal chain) used for the measurement had a build-in HP filter set @ ~20Hz. The step from 35Hz to 30Hz is the first one that shows some excursion reduction v. the simulation, and from then on it's down hill. That would be pretty normal for e.g.: a 2nd order 20Hz HP. Anyway, w/o at least a simultaneously recorded voltage input preferrably measured @ the driver I would not trust this information.
MMJ, do you have a link to where you found the data?
Regards,
David , Bjorno , TB46
Hi David!
I had not seen Bjorn Kolbrek's work before, i will have to check that out ...
and Hello Bjorno ! I admire your designs! ...
TB46 , Yes a high pass filter in his signal chain would explain the discrepancy ....... I ran across that comparison here on Diyaudio recently and decided to get a screenshot and make a note of it since these measurements seem to deviate so much from the virtual model .... Here is a link to the post & discussion:
http://www.diyaudio.com/forums/subw...-18-pa-drivers-b-c-copies-10.html#post3878009
Hi David!
I had not seen Bjorn Kolbrek's work before, i will have to check that out ...
and Hello Bjorno ! I admire your designs! ...
TB46 , Yes a high pass filter in his signal chain would explain the discrepancy ....... I ran across that comparison here on Diyaudio recently and decided to get a screenshot and make a note of it since these measurements seem to deviate so much from the virtual model .... Here is a link to the post & discussion:
http://www.diyaudio.com/forums/subw...-18-pa-drivers-b-c-copies-10.html#post3878009
BeauB,
Took me forever to get started too ..... It feels good to make sawdust though, i promise!
PM sent
Hi MMJ,
You might like to visit Bjørn's website - lots of very interesting stuff there, particularly under the "Publications" tab.
Home
Bjørn is currently working on his PhD. The focus of his research is horn loudspeakers
.Kind regards,
David
Hi MMJ,
You might like to visit Bjørn's website - lots of very interesting stuff there, particularly under the "Publications" tab.
Home
Bjørn is currently working on his PhD. The focus of his research is horn loudspeakers
Kind regards,
David
David ,
Sounds like a resource! I am going there right now to take a look, i plan to glean some tasty things for my brain
I'd love to see Bjørn design a "Karlson"
No problem at all Freddi!
Yep , the cab depth could be further reduced and it would drive FB and F10 upwards ... S1 section could be squeezed down so that the driver's motor still has plenty of room ... Something like this might be interesting with a 12" driver that has a higher free-air resonance (FS) of 60hz to 80hz ... This box would be like an ultra wideband miniature kick-bin
Brian in Texas is building a Mass Loaded Transflex
Brian (SynesthesiaAudio) from Texas is building the Mass Loaded Transflex (ML-TP) version 3.1 for the Lab15-4 (special run) .... He should be done in the next few days, and he mentioned that he managed to source the Special run 4 ohm Lab 15s even though they are no longer listed on Ebay!
I provided a few extra sketches to give him some ideas for bracing and stuffing/lining .... There are more braces than what is necessary in that "suggested bracing" sketch , the most vital are the three that stabilize the the top, bottom and back panels.
Brian (SynesthesiaAudio) from Texas is building the Mass Loaded Transflex (ML-TP) version 3.1 for the Lab15-4 (special run) .... He should be done in the next few days, and he mentioned that he managed to source the Special run 4 ohm Lab 15s even though they are no longer listed on Ebay!
I provided a few extra sketches to give him some ideas for bracing and stuffing/lining .... There are more braces than what is necessary in that "suggested bracing" sketch , the most vital are the three that stabilize the the top, bottom and back panels.
Attachments
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Lab15-Special-35hz-ML-TRANSFLEX-DOUBLE-FOLD-149L--DETAILED-COLLAGE.JPG
It just worked out this way i suppose ....
He contacted me a while back letting me know he wanted to build one of these boxes, and i asked him to take some pictures along the way ... Last week he sent pictures to me and i decided to post them here since it was a design that was developed in this discussion (albeit dated at this point), i didn't think it was terribly off-topic even though we have moved on to higher bandwidth configurations ...
I will have some pictures of my own to post in the next few days because i have been working on the Karlflex again, I have chopped up the Labyrinthine prototype , and i am adding Freddi's tuned cavity for testing , along with trying out some cardboard K-slots until i find a contour that works..
Such a great value =)
Lab15-4s (special run) are back up on ebay!
Eminence Lab 15 2 Pack 4 Ohm Special Run | eBay
Lab15-4s (special run) are back up on ebay!
Eminence Lab 15 2 Pack 4 Ohm Special Run | eBay
FREDDI'S EXCELLENT IDEA !
Based upon Freddi's Sketch from post #1320 i decided to model Freddi's tuned cavity in Akabak and it looked absolutely great(seems to be very useful in taming the ill-mannered midbass response
) so i went ahead and began to figure out a way to add this to the Karlflex prototype cabinet that i already have built sitting on my porch ..
The solution was pretty simple, it just required cutting out 3.5 inches worth of panel directly above the main vent and then glue the new chamber on top of the box .......
I made the new chamber out of some scrap ply i had laying around so the color & grain do not precisely match, and together with the Karlflex cab the whole thing does look a little hacked and chopped
but what the heck do i care, this is prototype for testing and learning purposes ..... I never claimed to have aesthetically pleasing woodworking skills, it doesn't have to look pretty, this is SCIENCE!
NOTE: This modification also increases the size of the Karflex's undersized front chamber, which is a nice bonus!
The portion of the Karlflex top panel that had to be removed
Where the new Freddi-Chamber will be placed, getting ready to glue it down
Then after gluing it in place and stuffing , it looks like this You can see i added an additional wire which leads out to the front chamber area, just in case i decide i want to mount a midrange and or tweeter driver into one of the K-slot wings ...
Oh , and by the way (flashing back to before i glued the side panel on) , I added some additional stuffing internally .... The S1 section is fully stuffed and it spills out towards the S2 section ...... Secured in place with adhesive (spray adhesive works) along with some industrial staples..... ........ "Mr Boo" The ghostly white cat (you can see him in the background) supervised this operation to make sure i did it properly ...
NOTE: I am thinking a little bit of lining on the bare side of the S1 panel might also be a good idea..
This cat also approves ... We are not sure what her name is, she is feral and just shows up to eat our food sometimes
...................................................................................................................................................................
Ok , now it is time to load the PA310 back into the box and experiment with an aperture ....
Based upon Freddi's Sketch from post #1320 i decided to model Freddi's tuned cavity in Akabak and it looked absolutely great
(seems to be very useful in taming the ill-mannered midbass response) so i went ahead and began to figure out a way to add this to the Karlflex prototype cabinet that i already have built sitting on my porch .. The solution was pretty simple, it just required cutting out 3.5 inches worth of panel directly above the main vent and then glue the new chamber on top of the box .......I made the new chamber out of some scrap ply i had laying around so the color & grain do not precisely match, and together with the Karlflex cab the whole thing does look a little hacked and chopped
but what the heck do i care, this is prototype for testing and learning purposes ..... I never claimed to have aesthetically pleasing woodworking skills, it doesn't have to look pretty, this is SCIENCE! NOTE: This modification also increases the size of the Karflex's undersized front chamber, which is a nice bonus!
The portion of the Karlflex top panel that had to be removed
Where the new Freddi-Chamber will be placed, getting ready to glue it down
Then after gluing it in place and stuffing , it looks like this
You can see i added an additional wire which leads out to the front chamber area, just in case i decide i want to mount a midrange and or tweeter driver into one of the K-slot wings ...
Oh , and by the way (flashing back to before i glued the side panel on) , I added some additional stuffing internally .... The S1 section is fully stuffed and it spills out towards the S2 section ...... Secured in place with adhesive (spray adhesive works) along with some industrial staples..... ........ "Mr Boo" The ghostly white cat (you can see him in the background) supervised this operation to make sure i did it properly ...
NOTE: I am thinking a little bit of lining on the bare side of the S1 panel might also be a good idea..
This cat also approves ... We are not sure what her name is, she is feral and just shows up to eat our food sometimes
...................................................................................................................................................................
Ok , now it is time to load the PA310 back into the box and experiment with an aperture ....
Last edited:
wild creatures , and some listening tests
Yeah, she is a cutie ..... We may keep her as long as she doesn't scratch up the furniture and make a mess
I took another picture for Freddi the other day before gluing the mod onto the box, here is the feral cat again with her friend from the neighborhood .. .
We live right in the middle of a college town here, and our house has become a sort of communal hangout for creative types over the years (which is a mixed bag of good and bad to be honest) ...... That combined with the fact that we have a swimming pool on the property which attracts creatures like these especially right now since the temperatures here in the Phoenix area have just risen to a high level of thermal brutality, people wear less clothing, i am not complaining ....
I am doing listening tests with this modified Karlflex cabinet now, i am hearing a huge improvement in the quality of midbass and midrange ... It is smoother , and much more pleasant to listen to, there is even much less reverberant ugliness in the midrange (even with this simple plank aperture) ..... Freddi's idea is sounding like a breakthrough! There is also something interesting going on with the bass extension, something good, I will post more about it soon after i verify a few things 
...
Yeah, she is a cutie ..... We may keep her as long as she doesn't scratch up the furniture and make a mess
I took another picture for Freddi the other day before gluing the mod onto the box, here is the feral cat again with her friend from the neighborhood .. .
An externally hosted image should be here but it was not working when we last tested it.
We live right in the middle of a college town here, and our house has become a sort of communal hangout for creative types over the years (which is a mixed bag of good and bad to be honest) ...... That combined with the fact that we have a swimming pool on the property which attracts creatures like these especially right now since the temperatures here in the Phoenix area have just risen to a high level of thermal brutality, people wear less clothing, i am not complaining ....
I am doing listening tests with this modified Karlflex cabinet now, i am hearing a huge improvement in the quality of midbass and midrange ... It is smoother , and much more pleasant to listen to, there is even much less reverberant ugliness in the midrange (even with this simple plank aperture) ..... Freddi's idea is sounding like a breakthrough!
There is also something interesting going on with the bass extension, something good, I will post more about it soon after i verify a few things ...
MMJ,
Thank you for the tip on that Abletec power supply! That supply and a pair of IRS2092 200 watt amps rocks! Very powerful, clean and clear. Anyone looking for a cost effective ($60) low distortion 200w/ch amp for a sub should check this out.
http://www.diyaudio.com/forums/class-d/275915-200w-irs2092-amp-20-a-7.html#post4364274
PS here: Abletec Switch Mode Power Supply +53V at 1.4A, -53V at 1.4A, +7.5V at 1.6A, +5.6V 1A
Amp here: IRS2092 200W Class D mono amplifier board-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group
Thank you for the tip on that Abletec power supply! That supply and a pair of IRS2092 200 watt amps rocks! Very powerful, clean and clear. Anyone looking for a cost effective ($60) low distortion 200w/ch amp for a sub should check this out.
http://www.diyaudio.com/forums/class-d/275915-200w-irs2092-amp-20-a-7.html#post4364274
PS here: Abletec Switch Mode Power Supply +53V at 1.4A, -53V at 1.4A, +7.5V at 1.6A, +5.6V 1A
Amp here: IRS2092 200W Class D mono amplifier board-in Amplifier from Consumer Electronics on Aliexpress.com | Alibaba Group
Hooray for good value!
XRK ,
I am really glad that you like it!
Has high quality high efficiency amplification ever been this affordable?? This set is one heck of a value!
You are running it at 8 ohms right now? Do you suppose it could operate at 4 ohms per channel for 400w total output with the single supply, or would a person need to use a two separate supplies in that case? (one supply per amplifier board) ....... I was looking at the PDF for that power supply recently trying to figure it out and as far as i can tell it should be able to pull it off as long as a person's music is dynamic and not just full scale sines for 5+ minutes straight (the rating is 4.13a at 54v * 2= 446 watts for 5 minutes before needing a second to catch it's breath!, and that is damned impressive for 20 dollars!)
So all in all it could potentially be 400w output at less than 60 dollars or less than 15 cents a watt for some high quality class D amplification
I see the guys in the other discussion about this set (in the class D forum) seeming a little skeptical about this power supply, almost as if they think it is too good to be true or something, and so instead are suggesting the other brand which costs three times as much .... Screw the naysayers!
If this supply holds up you have the deal of the century!
XRK ,
I am really glad that you like it!
Has high quality high efficiency amplification ever been this affordable?? This set is one heck of a value!
You are running it at 8 ohms right now? Do you suppose it could operate at 4 ohms per channel for 400w total output with the single supply, or would a person need to use a two separate supplies in that case? (one supply per amplifier board) ....... I was looking at the PDF for that power supply recently trying to figure it out and as far as i can tell it should be able to pull it off as long as a person's music is dynamic and not just full scale sines for 5+ minutes straight
(the rating is 4.13a at 54v * 2= 446 watts for 5 minutes before needing a second to catch it's breath!, and that is damned impressive for 20 dollars!) So all in all it could potentially be 400w output at less than 60 dollars or less than 15 cents a watt for some high quality class D amplification
I see the guys in the other discussion about this set (in the class D forum) seeming a little skeptical about this power supply, almost as if they think it is too good to be true or something, and so instead are suggesting the other brand which costs three times as much .... Screw the naysayers!
If this supply holds up you have the deal of the century! 
Not to make light of Freddy's many contributions, but RCA's Harry Olson came up with this tweak to smooth out his patented BLH and compound horn studio monitors before WWII, though not sure exactly when.
Not much truly new in speaker system design since the early '40s other than through materials, manufacturing advances.
GM
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