Frugel-Horn Mk3 Builds & Build Questions

I've gotten in touch with Ben and I'm sure it was just a slipup as I asked him to do me a custom baffle for the 7.3's without the plastic trim (he normally supplies them rebated to include the trim). I reckon he just stuck the wrong wood in the mill as he has the stock 7.3 + trim baffles ready to go.
 
That will stiffen, but it won't provide the thickness needed with a rebate and enuff material left to support the drivers.

dave

Yikes!!! I'd forgotten how big/thick MA's bezels were/are! Still, I'd do these same as I did with the EL70/FR125S/RS 40-1354 MLTLs: surface mount and use a 1/2" thick felt pad to damp its and the baffle's eigenmodes and add significant weight to the top/bottom to vertically mass load the line as well as make it bottom heavy enough to counterbalance it.

GM
 
I surface mounted my 7.3s, since I didn't know to reinforce the baffle. It wouldn't be too late to add something behind the driver, but I could also surround with felt? I may just try that.

I'm still playing around with the build, having not yet glued the bottom nor the top to allow access to stuffing. I could glue a backer, except I already chamfered the baffle. I also still have the issue with one speaker's back extending too far down. I may just let it be, on closer measurement it is 3/16" off, or maybe sand it down just a bit. Solid oak takes a lot of sanding though.
 
Correct, just make sure the felt is a little thicker than the driver's height off the baffle.

Scott hasn't got back to us about it yet [you still have wisdom teeth?!], but I doubt it makes an audible difference in room, but if it's something that will 'eat away' at you, then beg/borrow a small Dremel or similar rotary grinder with a coarse sanding drum or wood rasp and/or an inexpensive Surform file to whittle it down a bit before sanding it ~smooth.

GM
 
I finally got back to finishing these up for once and for all. I was able to sand down the bottom of the V to get to the proper opening using 60 grit on my random orbital sander. It didn't even take long, and I did it with the roundover. If I go back down to my work area, maybe I'll have it all done by the time the Super Bowl starts, I just need to glue the top and bottom. The only reason I'm even on the forum is to check the general wisdom on the stuffing for the A7.3. I have in the back, but not the front. Maybe some in the front too I guess.
 
Sorry -completely forgot :bawling: Will get onto it 1st thing in the morning.

Yes -still got the wisdom teeth so far. Good job -about the only wisdom I'm likely to have. ;) Not sure for how long -three have come through completely & the dentist isn't overly thrilled about that. Presumably she thinks I'm some kind of crocodile.

If this is for my glue-up mistake, don't worry. I already adjusted so that it would be back to spec.

Btw, my wife's name is Lindgren.
 
I have searched for the plans for the more 'advanced' Frugel-Horn Mk3, but can only find the basic plans.

Have I overlooked something on the FH website?

The SketchUp plans only have the basic configuration.

The other thing I don't understand is the comment that you need a 5-Axis CNC to make these. Is that in relation to the tapered edges that butt-join the interior panels?

If that's the case, I was going to make a series of corner pieces to join them at the right angles on the table saw, but leave the bulk of the panels cut square on the CNC.

Can anyone see an issue with that? (feel free to call out 'Dummy!' or whatever - I am a complete novice to speaker building).

I was also tossing up some advanced jointing - I've been dying to use some of the joints in this: 50 Digital Wood Joints | Flexible Stream
 
frugal-phile™
Joined 2001
Paid Member
Full plans are on the same webpage as the SketchUp download. The Frugel-Horn

It seems sully to me to make additional pieces to "fill-in" for right=angle ends on the panels. Makes much more sense touse the CNC to rough cut the pieces and then run them thru the table saw. But we have also found that it is quicker & easier (& cheaper if you are paying CNC time) to just cut them with the CNC.

dave
 
Hi Dave,

Do you have a 5-axis CNC? (It was you that said you can't make these on a 3-axis... that you needed a 5-axis). And if not, do you just step-cut them at 1mm (or less) steps?

And the plans I was looking for were for these:

build-levelsB.gif


http://p10hifi.net/tlinespeakers/FH/images-fh/build-levelsB.gif

(but I suspect I had an old link, and these are now superceded?)
 
What exactly do you mean by "more advanced" FH3? In addition to the scores of flat pack kits and fully assembled pairs of these I've fabricated, there have been a substantial number of kits by others, and DIY builds, but hopefully all have complied to the configuration of the original plans.

As for requiring a 5 axis CNC machine for these - while that wouldn't hurt, it's not at all mandatory. The commercial millwork shop that's been my day job for 22yrs ships over $4M a year, including much more elaborate assemblies than the FH, and while we're on our second CNC point to point machining centre, the need for more than 3axis work has not been sufficient to justify the added cost.

I digress


The kits that Planet10 distributes uses dados on side panels for capture of the five lateral panels including front baffle, and a small scarf joint on the back panel. Along with a small tapered gluing block located near the apex of the folded horn path, that joint provides substantial glue surface area, and when properly assembled ensures an airtight joint. The scarf joint is easily cut with the use of a tenoning jig on table saw, set to the same 5dg as required on at least one end of 4 of the 5 lateral panels. I've cut literally hundreds of pieces for the FH3 and FHXL exactly this way - all on an at least 50yr old Rockwell table saw. When all cued up, I'd even wager it'd be just as fast on this operation as a 5axis CNC - not as sexy of course.

Insetting the lateral panels into dados aids in assembly, and particularly ensures alignment, tight joint at apex, and rigid final assembly, but even those are not absolutely essential. I can see no structural reason to use any more elaborate joinery for these enclosures.

Edit- PS. - yes the design in you post above has been superseded, The current version is found here
http://www.frugal-horn.com/fh3-plans.html
 
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Ok - the 'more advanced' are shown in pictures above... they are from your site. They are pretty self-explanatory. Instead of one single baffle piece (apart from the front and rear), there are 5 or 6 other panels.

Also, it was you that said - pretty clearly and emphatically - that you couldn't make these on a 3-Axis CNC - not me.

...Do note that unless you have a 5-axis CNC, a CNC is only useful for doing the sides and the baffle rebates.

dave

Unless it is some insider knowledge known to advanced speaker builders.

Don't forget - as I said before, I am a complete rookie at this. All I have to go on is the combined wisdom of the very experienced people contributing to this thread, and as the designer, I placed a great deal of value on your statement.

I am just the poor sap asking the question, that seems to have gone down some rabbit hole to another dimension where questions become something other than questions and statements made seem to have a meaning other than what I think they mean.

Maybe I'll just make a cube and stick a speaker in it.

Thanks for your help.
 
Read my post above

Dave and Scott are great designers, and Dave can draft with the best of them but I'm the poor sap who gets to actually fabricate and assemble most their designs from Proof of concept ( not all make it), to rationalizing those that do for ease of build by DIYers without access to higher capability CNC machinery. I happen to be blessed with access to such, but in the case of the newer - perhaps that's what you meant by " more advanced" FH3? a 3 axis CNC is used only to route the shapes of side panels, dados, and rebated cutouts for drivers front baffle and input terminal cup on rear.

Don't assume that the design with more internal parts and convoluted path is the superior performer - I've built multiple pairs of each, and can attest that the FH3 wins that test. It's also a much simpler build - sometimes less is more.

As I mentioned earlier, Dave's reference to 5 axis was that 4 of the 5 lateral panels ( all but the vertical internal fold panel) require an approx 5dg bevel cut on at least one end, and I described our reasoning behind the scarf joint at apex. A 5 axis CNC a can be a very accurate "saw", but all of those can easily be cut with a sled and tenoning jig on basic table saw. The investment in a high quality, high tooth count carbide blade for this will ensure clean cross grain cut on the grade of multi-ply that these designs recommend
 
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Doh! I am confused by all you Canadians... :eek:

It's been a huge learning curve and reading through hundreds of forum pages has gotten me sideways'd.

Sorry Chris (and Dave) for getting it all muddled and coming across as an *** - I'm not really (unless you are Australian, then rugby dictates that I maintain a level of ribbing rated at 'Dick').

I think I geddit now.

I have a 110T plywood-specific narrow-kerf blade on my table saw, a range of bits on my 8x4 CNC router and I think I can (now) work out what I need to do.

I agree, using a sled and a table saw/drop saw is going to be a lot easier than trying to generate the g-code necessary to make included angles so things fit. I am having a ball with the look of finger-jointed tenons in ply right now and may go that way, with a round-over bit in my hand router to clean it up and a generous dollop of silicone to seal it.

It seems that the 'advanced' (or more correctly 'more complicated') designs I was looking at are old - the FHMk3 is the simplest and only current design.

As all my ply is hardwood (we do a nice line in removing Orang Utan habitats here :rolleyes:), I may play with 15mm rather than 18mm/24mm thicknesses - the price is massively different.

Thanks for your forbearance and I will try and discern one Canadian from another in future - I don't suppose 'You guys all look the same to me' works?