Hi XRK971 - I bet your Beta 8cx XKi, despite going about an octave lower than scaled K15, still has plenty of upward dynamic range - especially compared to some 8" FR whose BL poops out past 1mm of travel.
On another topic, I wonder how baffle tilt affects things vs a K-aperture.
Here's a Karlflex sketch drawn by TB46 with standard baffle vs one with more baffle tilt plus John Karlson's 1951 patent application comments on how he viewed the front chamber (K15 was prototyped, tested and finished in the summer of 1951 and made its commercial debut at the 1952 fall Hotel New Yorker big Hi-Fi show along with many other iconic hi-fi products of that time)
In practice, the old R-J approach (which had very little front cavity) might make the nicest graphs (?) and could use JBL's current lens vs the traditional "lemon". Does the R-J damp cone overshoot at high levels ?
On another topic, I wonder how baffle tilt affects things vs a K-aperture.
Here's a Karlflex sketch drawn by TB46 with standard baffle vs one with more baffle tilt plus John Karlson's 1951 patent application comments on how he viewed the front chamber (K15 was prototyped, tested and finished in the summer of 1951 and made its commercial debut at the 1952 fall Hotel New Yorker big Hi-Fi show along with many other iconic hi-fi products of that time)
In practice, the old R-J approach (which had very little front cavity) might make the nicest graphs (?) and could use JBL's current lens vs the traditional "lemon". Does the R-J damp cone overshoot at high levels ?
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Short xki for a PA130-8
Hi xrk971 (or any other learned member of the forum,)
I have been a lurker but this is my first post.
I am planning to build an xki for a PA130-8 from 5mm foamcore. I need to reduce the height so it will fit in the allocated space. I worked with the plan credited to Thermcul on page 1 of this thread and reduced the internal height to 265mm (10.4",) increased the depth, kept the port dimensions the same and played with the baffle to maintain the front and back volumes. I have attached a plan.
My questions are:
1. What is the internal width of this enclosure? I cannot see that it has been specified anywhere.
2. What would be the best shape for the front aperture? i.e. how far down should the opening start, what width at the top and what radius?
3. Are there any obvious problems with my adaptation of the design?
I could go with the little RS100P-4 version of the xki if there are too many problems with shortening the PA130-8 version, but the PA130-8 would be my preference. They are also $28 cheaper for a pair than the RS100P-4 in Australia.
I previously built some mini Ks and a small xki from cannibalised 2.1 computer speakers using corrugated cardboard, so I have had some practice with score and fold. I will post some photos later.
Thanks,
Jim
Hi xrk971 (or any other learned member of the forum,)
I have been a lurker but this is my first post.
I am planning to build an xki for a PA130-8 from 5mm foamcore. I need to reduce the height so it will fit in the allocated space. I worked with the plan credited to Thermcul on page 1 of this thread and reduced the internal height to 265mm (10.4",) increased the depth, kept the port dimensions the same and played with the baffle to maintain the front and back volumes. I have attached a plan.
My questions are:
1. What is the internal width of this enclosure? I cannot see that it has been specified anywhere.
2. What would be the best shape for the front aperture? i.e. how far down should the opening start, what width at the top and what radius?
3. Are there any obvious problems with my adaptation of the design?
I could go with the little RS100P-4 version of the xki if there are too many problems with shortening the PA130-8 version, but the PA130-8 would be my preference. They are also $28 cheaper for a pair than the RS100P-4 in Australia.
I previously built some mini Ks and a small xki from cannibalised 2.1 computer speakers using corrugated cardboard, so I have had some practice with score and fold. I will post some photos later.
Thanks,
Jim
Funny that dimension is not there. I think is is 7in based on photo with ruler.
I actually said it was 7in internally here:
XKi - X's ab initio Karlson 6th Order Bandpass
I actually said it was 7in internally here:
XKi - X's ab initio Karlson 6th Order Bandpass
Thank very much. Not sure why I didn't see it. I will double check my plan against yours.
In your plan, the top of the K aperture is in line with the bottom of the vent. Should I use that as a starting point and fudge it from there?
Was it worthwhile adding the floor underlayment to your wings on your PA130 build? I don't want to muck around with plywood, but should I make the wings from a double layer of foamcore or just stick to a single layer?
In your plan, the top of the K aperture is in line with the bottom of the vent. Should I use that as a starting point and fudge it from there?
Was it worthwhile adding the floor underlayment to your wings on your PA130 build? I don't want to muck around with plywood, but should I make the wings from a double layer of foamcore or just stick to a single layer?
The design for the W5-2143 is linked on the first page at the very top. Plans are just in words but you can figure it out. I can dig up a drawing - it’s somewhere in this thread I am sure.
I have not done the W8 because the box is huge. Recommended vented cabinet is 2.8 Cu ft. Use a bass reflex calculator and find out vent cross sectional area length for 0.67x the volume of 2.8 Cu ft. Make overall box volume 2.8 Cu ft and make rear chamber 2/3rds volume and front chamber 1/3rd. Tune box to about 41Hz.
I have not done the W8 because the box is huge. Recommended vented cabinet is 2.8 Cu ft. Use a bass reflex calculator and find out vent cross sectional area length for 0.67x the volume of 2.8 Cu ft. Make overall box volume 2.8 Cu ft and make rear chamber 2/3rds volume and front chamber 1/3rd. Tune box to about 41Hz.
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Hi X,
I am refining my plans for my shortened PA130-8 Xki. The internal height will be about 10", so 2" shorter than the original plan. The width will remain at 7" and the depth increased to keep the volumes the same. I have four ideas in the attached jpg.
Option A is the normal design but with the baffle laid over at a greater angle to create the additional space required in the front chamber. The other options are attempts to keep the angle of the driver more or less consistent with the original design.
My questions are:
1. How far can the baffle be angled back before the driver is pointing too high? Does it matter much behind a K-aperture?
2. Does the baffle need to intersect the bottom corner as it does in A and C? In other words, is the triangular shape of the front chamber critical to how it works with the K-aperture?
I have the PA130-8's now. D-Day will be on the last weekend of the month, when my wife is away with her girlfriends, so still plenty of time to make changes.
Cheers,
Jim
I am refining my plans for my shortened PA130-8 Xki. The internal height will be about 10", so 2" shorter than the original plan. The width will remain at 7" and the depth increased to keep the volumes the same. I have four ideas in the attached jpg.
Option A is the normal design but with the baffle laid over at a greater angle to create the additional space required in the front chamber. The other options are attempts to keep the angle of the driver more or less consistent with the original design.
My questions are:
1. How far can the baffle be angled back before the driver is pointing too high? Does it matter much behind a K-aperture?
2. Does the baffle need to intersect the bottom corner as it does in A and C? In other words, is the triangular shape of the front chamber critical to how it works with the K-aperture?
I have the PA130-8's now. D-Day will be on the last weekend of the month, when my wife is away with her girlfriends, so still plenty of time to make changes.
Cheers,
Jim
Attachments
hey X - regarding a ten inch driver XKi with one inch high shelf vent, would you maintain that one inch distance from the front edge of the vent to the aperture plate - or make a "bit" bigger? It would be really cool if the finished height of this cabinet is only 17" - I think it might punch pretty well for a little box.
also, how would you do the aperture?
BEST !
Freddy
also, how would you do the aperture?
BEST !
Freddy
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Question about k-aperture wing size XKI for PA130-8
Hello everyone
I build a XKI with PA130-8 (see pictures) and I was wondering if the aperture is about the right size. I kind of copied it from the other picture attached.
The K aperture opening starts below the top vent and about 2,5 inch from the top, as per instructions from the forum. However, for the width and curve of the wings, is there some guideline to follow?
The wings are not 'just' touching the driver surround but are covering a bigger part of the woofer it seems. Should I widen the wings more?
Also maybe contributing factors (i dont know of they are)
- I think maybe the sound has a 'cupped hands' quality to it.
- I have not yet made the front with a double foamboard layer.
What do you think?
Thanks in advance,
Sam
Hello everyone
I build a XKI with PA130-8 (see pictures) and I was wondering if the aperture is about the right size. I kind of copied it from the other picture attached.
The K aperture opening starts below the top vent and about 2,5 inch from the top, as per instructions from the forum. However, for the width and curve of the wings, is there some guideline to follow?
The wings are not 'just' touching the driver surround but are covering a bigger part of the woofer it seems. Should I widen the wings more?
Also maybe contributing factors (i dont know of they are)
- I think maybe the sound has a 'cupped hands' quality to it.
- I have not yet made the front with a double foamboard layer.
What do you think?
Thanks in advance,
Sam
Attachments
I had kinda missed XRK971's discussion of an XKi for Fane's 12-250TC. At 80 liters internal volume, its about the size of some sealed boxes for that driver.
12-250TC played clearly in a Karlson K12 and without noticeable artifacts, so should be good as an XKi.
Would 12mm Baltic birch suffice for such a build?
For internal box size - how about 15" width, 16 inch depth and about 23 inch height? Would it be OK to make the vent the full 15" width rather than 12" specified in X's Akabak sim ?
Would iit be better to have the internal width 14"?
For a fixed front chamber volume, how does the inner vent coupling vs front aperture change say with internal cabinet width going from say 14" up to 19" width? - seems like that would have some influence upon response (?)
I'm at the mercy of my long distance builder so don't know if can happen or not.
12-250TC played clearly in a Karlson K12 and without noticeable artifacts, so should be good as an XKi.
Would 12mm Baltic birch suffice for such a build?
For internal box size - how about 15" width, 16 inch depth and about 23 inch height? Would it be OK to make the vent the full 15" width rather than 12" specified in X's Akabak sim ?
Would iit be better to have the internal width 14"?
For a fixed front chamber volume, how does the inner vent coupling vs front aperture change say with internal cabinet width going from say 14" up to 19" width? - seems like that would have some influence upon response (?)
I'm at the mercy of my long distance builder so don't know if can happen or not.
