G-chang build pioneer bofu

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blrh93

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Joined 2008
#1
im starting this thread to record my build of a pair of chang speakers as in the plans below with a couple of mods

fMxdMRt.jpg


heres a photo of the stands i have had made, i need to drill them to attach to the cabinets and the bases:

T4EAkp1.jpg


im going to remove the top and bottom stepped sections, so the cabinet will look like a trapezoid from the side view

i plan to drill and dowel the sides to the internal box and back/horn sections to add extra strength

i will bolt the metal stands to either some left over 18mm birch ply or some bits of marble, and add some spikes

i have seen people add tweeters to this design, i have bought a pair of Dayton Audio ND16FA-6 5/8'' are these any good?

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along with some 2.2uf Alcap Bipolar Capacitors 50v, will these give a good crossover point between the pioneer drivers and the tweeters?

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im going to cnc the front panel, this is a design i have created:

kHClcfZ.jpg


any advice about the changes in design, the stand material (ply vs stone),internal bracing and damping, and the tweeter and cap arrangement would be greatly appreciated.
 
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#9
#10
blrh93, I think everything looks great and you can proceed as planned. The decorative tweeter baffle is beautiful and you should get a nice full sound from the B20s in this cabinet. Even tho the above comments are valid I believe it is more important to find the right blend between the tweeter and B20 for maximum enjoyment. I'd recommend having additional capacitors to try for blending drivers - you can start with the 2.2uf and work your way up or down with a few .47uf or .33uf to find the best compromise. Nothing is ever perfect but what you have begun will be very musical indeed. The B20 is one of my favorite wide range drivers - I used a cheap piezo with mine and loved the way it sounded.
 
#12
I built a pair of half-changs using bofu's. The bracing and damping were included in the plan. I could scan it and email it to you if you like. Dave should have it also. I believe the driver chamber is the same but just has one mouth. Unfortunately the bofu's did not survive a drunken viewing of Insidious (wife was out of town). Too many db's and Newcastles and what sounded like 60hz square waves put them in an early grave. I replaced them with fe206en's and after a long break-in they sound very nice.
 
#14
Not trying to hijack the thread, but it looks like I could also use a set of the plans for the half-chang and/or the full chang for the BOFU. Should I pm Dave or what process?

Quite a while ago, I picked up 2 pair of BOFU just before they were unavailable, and, I also bought phase plugs from Dave. However, with house sale, moving, etc., I didn't get around to building boxes yet.

I thought I had a copy of the "plan" (i.e. a 1 or 2 page document), but Jimbro's comment - "The bracing and damping were included in the plan" - makes me think there are more complete plans somewhere out there. I don't have those.

Thanks
 
#15
It's been a few years since I built the half-changs so I went through my plans file and couldn't find them. They're here somewhere. From what I remember the bracing was shown but no dims given but easy to figure out and just a sentence or two about the damping. You probably have the same plans. If the plans turn up I'll give you a better answer.
 
#16
Thanks, Jimbro.

From your comments - "no dims given but easy to figure out and just a sentence or two about the damping" - and my recollection, I expect that I do have the same plans. Like you, I'll have to look around a little more to locate them. I haven't unpacked all my boxes yet, so I expect that I'll find them... I know that I made 1 or 2 copies previously (as well as printouts from some build threads/posts). So don't go to too much bother w.r.t. my post.

Of course, I don't know whether or not the op got a copy of the plans.
 
#19
jimbro said:
I built a pair of half-changs using bofu's. The bracing and damping were included in the plan. I could scan it and email it to you if you like. Dave should have it also. I believe the driver chamber is the same but just has one mouth. Unfortunately the bofu's did not survive a drunken viewing of Insidious (wife was out of town). Too many db's and Newcastles and what sounded like 60hz square waves put them in an early grave. I replaced them with fe206en's and after a long break-in they sound very nice.
Click to expand...

I still have my BOFU / half-Changs, as well as the original PDF plan sheets for both half and full Changs. Mine are the R and L for a 4.1 surround system, with two more BOFU's in sealed boxes firing up for the rears.

Bill
 
#20
adason said:
That's way too much trouble for such cheap driver. I hope you are familiar with great article Nelson posted about fullrange speakers and current drive.
Click to expand...

is this the article you are referring to?

xoz4SsD.jpg


i am not familiar with that article

i have just picked up an old cyrus amplifier which is what i am planning to run the speakers with

can anyone explain what nelson is on about, in layman's terms

if i understand correctly, i could get more low end with a current source amp, or an rlc with a standard amp to simulate a current source, am i on the right lines? what does rlc stand for? rated load current??

i have never heard of current source before now, its a bit beyond my level of understanding at the moment

https://www.youtube.com/watch?v=E38u3pLHSOc
 
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