Vaseline - nice trick.
If /when I do another FC project I am going to throw out all that stuff about a quick build. The accuracy of the cuts is very easy to mess up and it can't be checked till the gluing starts. Errors seem to be in the 1/16' to 1/8" area and can result from simply a variance in the blade angle. Easily fixed but "I ain't doin' no more quick builds."
If /when I do another FC project I am going to throw out all that stuff about a quick build. The accuracy of the cuts is very easy to mess up and it can't be checked till the gluing starts. Errors seem to be in the 1/16' to 1/8" area and can result from simply a variance in the blade angle. Easily fixed but "I ain't doin' no more quick builds."
Bob,
How are you cutting the foam core? My accuracy is about +/- 1mm using a long piece of masonite panel as a straight edge and an X-acto. I use a pencil to mark of the cut points at each end of the foam using a ruler to set the width (6.0 in or 8.0 inches or whatever the general main panel widths are). The use the Xacto pressed against the straight edge and with light pressure the first time - score through the paper. Use subsequent cuts with more pressure to go through the foam while keeping the blade vertical. It takes generally 3 to 4 strokes but I get very neat edges that are consistent. The key to keeping a uniform width is to cut the sections from the same long strip. When making the next strip, make sure it is the same width. I actually use a strip of foam core as a ruler I can write on. The measurements don't have to be exact, but they are reproducable which is important. I know it seems long but how much time would you have spent to make this out of wood? I average 3 to 4 hours on a new build. Once I am smarter then next one takes 2 to 3 hrs of the same speaker. You are doing two at a time so double that for what you are doing.
How are you cutting the foam core? My accuracy is about +/- 1mm using a long piece of masonite panel as a straight edge and an X-acto. I use a pencil to mark of the cut points at each end of the foam using a ruler to set the width (6.0 in or 8.0 inches or whatever the general main panel widths are). The use the Xacto pressed against the straight edge and with light pressure the first time - score through the paper. Use subsequent cuts with more pressure to go through the foam while keeping the blade vertical. It takes generally 3 to 4 strokes but I get very neat edges that are consistent. The key to keeping a uniform width is to cut the sections from the same long strip. When making the next strip, make sure it is the same width. I actually use a strip of foam core as a ruler I can write on. The measurements don't have to be exact, but they are reproducable which is important. I know it seems long but how much time would you have spent to make this out of wood?
I average 3 to 4 hours on a new build. Once I am smarter then next one takes 2 to 3 hrs of the same speaker. You are doing two at a time so double that for what you are doing.
Yes, I have said that the plan that I provided on post 1 has been slightly modified to be used efficiently with a sheet of 20 in x 30 in foam core. If you transfer the plan onto a side panel of the build (the critical corners and main geometry points) you will find that the pieces as measured fit well. The problem that Bob had was in going from an untested cut sheet that someone else made. The most accurate way to make it is to draw the plan on the side panel, then measure the length of the piece you need and then cut it. If you do it that way, you are assured a perfect fit.
I've found the same effect with a variety of fullrange speakers I've built. Imaging extends well beyond the speakers. I haven't noticed that yet with multi-way speakers that I have. But will be building some petit onkens soon and will be interested to see if it happens with those.
While I've had the same problems with cutting FC it still has been quite a bit faster for me (panels can flex a little to fudge bad cuts if they aren't too bad - but that's in part b/c I see it mostly as a testing approach. But even more important is that if you fleck up a cut, it isn't very expensive to just cut a new piece. Old scrogged pieces can often be used for other projects or for bracing.
If ya'll remember, way back at the beginning I built a little Styrofoam rig and fence to hold the blade at 90 degrees. It works great but I didn't use it this time. That's what I was referring to when I said no more quick builds. It doesn't take that much more time to be more exact in the cutting phase and surely pays off later.
I may have posted this here earlier but - years ago after spending over an hour trying to show my daughter a slick shortcut on the computer, she stopped me and said " Dad, can't we just do it the hard way, we could save a lot of time." Out of the mouths of babes
Speaking of the hard way. After all that conversation, I didn't put the open foam in, but caught it before the first side panel had set. Might be morning before the music flows.
I may have posted this here earlier but - years ago after spending over an hour trying to show my daughter a slick shortcut on the computer, she stopped me and said " Dad, can't we just do it the hard way, we could save a lot of time." Out of the mouths of babes
Speaking of the hard way. After all that conversation, I didn't put the open foam in, but caught it before the first side panel had set. Might be morning before the music flows.
I may have posted this here earlier but - years ago after spending over an hour trying to show my daughter a slick shortcut on the computer, she stopped me and said " Dad, can't we just do it the hard way, we could save a lot of time." Out of the mouths of babes
As the father of 7 and 10 year olds, I LOVE IT!!!
well it looks like this thread has pushed me down the karlson rabbit hole....
Somewhere on the web I saw a smaller karlson (maybe with a fe126) that the guy said did well on its side?
can anyone with karlson experience comment on the vertical dispersion and the use of the medium sized karlsons on their side?
how does this 0.53x karlsonator perform on its side?
I've got a short but wide space to fill, if anyone is curious btw.
Somewhere on the web I saw a smaller karlson (maybe with a fe126) that the guy said did well on its side?
can anyone with karlson experience comment on the vertical dispersion and the use of the medium sized karlsons on their side?
how does this 0.53x karlsonator perform on its side?
I've got a short but wide space to fill, if anyone is curious btw.
The acoustic lens effect of the Karlson aperture is vertically symmetric. I don't think the dispersion placed on its side will be as uniform. I have not measured it on its side and don't intend to as it is a painful measurement to make. However, I will do a simple listening test and report in my subjective experience. Why do you want to use it on its side? A matter of cabinet aspect ratio I suppose.
xrk971 -- yeah it is the aspect ratio. unfortunately, since this karlson stuff seems to pack much punch into a small space, it has attracted my need to put speakers where speakers aren't welcome... (and just creating a hole to throw any old driver isn't fun is it)
scaled down karlsons might be the way to go however. Just a shame as I have space, just not vertically!
I have also seen pictures of hung PA karlsons that where mirrored pairs on their sides, but I'm sure these where bandpass crossed over (low - midbass?)
scaled down karlsons might be the way to go however. Just a shame as I have space, just not vertically!
I have also seen pictures of hung PA karlsons that where mirrored pairs on their sides, but I'm sure these where bandpass crossed over (low - midbass?)
Standing on one leg
It lives. Got one working and the other about an hour or so away. Very nice. Everything is there short the outside extremes. Hard to tell with just one, but a small sub could help the very very bottom in a big room with big music, but isn't necessary for 95% of what one would play. Placement will be important as tipping the speaker backwards from an arms distance creates a wide variety of high/low mix. Getting the second channel up and both speakers on stands near the room corners is going to be quite impressive. No doubt the single Vifa version would be an excellent build for a desktop system. The mid dynamics are clean with the top end of the kick drum punching through with authority. I do think the Vifas - particularly the upper registers - sound better in this design than in the other two FCs I built.
I found some thin foam rubber and cut strips for the wing seals. Since I have it I applied a small bead of electricians putty (not plumber's) on the driver basket.
Just a few minutes listening but the results are well worth the effort. I'll either build another set or go for one somewhat larger - paying better attention to detail at the cutting phase. Very impressed Mr. X
P.S. The amp is a new monoblock version of the MyRef Fremen Edition. Cant wait to get the other side running.
It lives. Got one working and the other about an hour or so away. Very nice. Everything is there short the outside extremes. Hard to tell with just one, but a small sub could help the very very bottom in a big room with big music, but isn't necessary for 95% of what one would play. Placement will be important as tipping the speaker backwards from an arms distance creates a wide variety of high/low mix. Getting the second channel up and both speakers on stands near the room corners is going to be quite impressive. No doubt the single Vifa version would be an excellent build for a desktop system. The mid dynamics are clean with the top end of the kick drum punching through with authority. I do think the Vifas - particularly the upper registers - sound better in this design than in the other two FCs I built.
I found some thin foam rubber and cut strips for the wing seals. Since I have it I applied a small bead of electricians putty (not plumber's) on the driver basket.
Just a few minutes listening but the results are well worth the effort. I'll either build another set or go for one somewhat larger - paying better attention to detail at the cutting phase. Very impressed Mr. X
P.S. The amp is a new monoblock version of the MyRef Fremen Edition. Cant wait to get the other side running.
Attachments
I tried them sides ways - not bad sounding but I can detect that the sweet spot is not as wide as with the vertical arrangement. Note that the Karlson proper (1955 based design and its variants are band pass multi-chamber reflex alignments and do not scale well below 12 inches). If you want to scale smaller, use the Karlsonator design in this thread.
