Frugel-Horn Mk3 Builds & Build Questions

frugal-phile™
Joined 2001
Paid Member
There's a small inconsistency in the latest docs in the stuffing info on pg. 6: "1.2" (12mm) cotton or wool felt"

fixed the typo

Also: Is the green fluff denser than the orange fluff?

There is still a lot of work on figuring out the best damping strategies. The green & orange are intended to be part of a continuum. The differnt colours represent different areas to fill (as does the red cloud). As results for various drivers come in, i'll keep adding these as starting points (amps & room placement will also fill a role, as will how much bass an individual likes)

dave
 
Today I found I was in posession of several 4" no-name drivers that came from Meniscus a couple years ago. I had not given them any attention at all.
I hooked one up to gather parameters and then compared them to those of the candidate drivers mentioned here. Hmmm...within range.

f(s)= 75 Hz
V(as)=6.9 liters
R(e)= 6.92 ohms
S(d)=70 cm*2
Q(ms)=2.9
Q(es)=1.07
Q(ts)=0.78
L(e)=0.8 mH
BL=3.78
SPL=86.2 dB/w/m

The driver looks a lot like this:

https://www.madisound.com/store/product_info.php?products_id=8802

Well...I'll be knocking an FH Mk3 together over the next few weeks. I'll tweek the dimensions to match the driver.

I'm thinking to use an oval supra baffle with the driver off set and back mounted.

What type of wood??? Hmmm...

Should I consider phase plugs for this?
 
i have put 0.3lb of polyfill in each speaker, equal amounts in each chamber. this less than i started with (about 0.4lb+) and dropped the damping a couple of inches lower in the second chamber, i'll let them play like this till they are well and truly run in.
well pleased with them, more base than i imagined, but then this my first taste of full-range.
going to make deflectors and suprabaffles as per originals would this be ok using same dimensions?
 
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Is there an alternate download of the plans from post 8? Mac.com seems to be down.

Thanks!

On the subject of baffles, perhaps this is something? – A superelliptical suprabaffle. I haven't found the look of suprabaffles appealing to my tastes. I've given it some thought, and a superellipse was suggested to me. The superellipse seems to work with the shapes of both the cabinet and driver. What do you think?:

D0xUx.jpg
 
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When you consider supraBaffles, you need to consider the affect of the edge termination. This famous page from Olson gives a good foundation.

Thank you! I remember seeing that one before; It didn't stick.

Just to clarify - the flat superelliptical baffles wouldn't be worth it, then? Or would they be an improvement over a suprabaffle-less setup, only not as optimal as an SB can be?



Another thing - What effect if any does the cabinet have on the driver efficiency? Is the system efficiency the same as the driver's, or higher or lower?
 
An externally hosted image should be here but it was not working when we last tested it.


A profile called "thumbnail" is often used on table edges. The radius of curvature varies through a 90 degree arc.
I'll back mount my driver and use a part of this profile @~45 degree tangent around the driver. When I use a larger bearing with the bit above the point of contact along the cutting edge is changed to accomplish this.

I'll also use the full profile on the supra-baffle edge...maybe backed up with a large roundover?...:rolleyes:

I'll also offset the driver between edges to avoid the "point source" ripple shown for the cylinder on the left, above.
 
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frugal-phile™
Joined 2001
Paid Member
Just to clarify - the flat superelliptical baffles wouldn't be worth it, then? Or would they be an improvement over a suprabaffle-less setup, only not as optimal as an SB can be?

It may be. Just be aware that the abrupt edge will bring new issues to the table.


Another thing - What effect if any does the cabinet have on the driver efficiency? Is the system efficiency the same as the driver's, or higher or lower?

The box only affects the band in which it operates. With a horn, the idea is to lift the bottom (where the horn operates) so as to keep up with the mid/top range, as well as eliminate any ** filter which would attenuate the mid/top.

So the efficiency of a rear-loaded horn is typically the rated efficiency as opposed to often a lower efficiency with a more pedestrian box.

dave
 
Thank you for the info, Dave. As a beginner, I'll be putting any baffle ideas pretty low on the list of things to think about.

Regarding the required cuts – As far as I can tell, there cabinet tilt and horn folding require some ~4.8 degree cuts on the ends of some pieces. I know hardly anything about woodworking :shy: ... I tried searching for the best method for these cuts, but I came up short. Are there any good resources that show how to do this?
 
By loading the Sketchup model and using the tape measure tool, I'm seeing that the tilt back from vertical is 3" at the top front edge, and the rear edge of the top of the cabinet side is 10.25" back from the vertical axis. I'd hold off cutting until you get that confirmation from the designers. You beat me to this question. :)
 
Planet 10,
What speaker are you prepping this design for. What kind of distance from the wall should be considered with these. May be willing to be a beta builder.

Was originally targeted for 3-4" drivers; most notably the Fostex FE126en, Mark Audio Alpair 7, CHR70 (and paper coned sibling the CSSEL70)

As noted in another thread on the subject, I'm not sure how many beta builds have been undertaken or completed ( this is a very quick and easy build compared to the FH-one), or with which drivers.


Dave - perhaps time for a log or builder's gallery on the FH site?


As for distance from wall / corner, that's quite room / driver / amp dependent. With the highly modified Dyna ST70, I personally preferred the FE126En closer to the wall and driven in triode mode, and the Mark Audio drivers further away and with the amp in U/L mode.

of course YMMV
 
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frugal-phile™
Joined 2001
Paid Member
As for distance from wall / corner, that's quite room / driver / amp dependent. With the highly modified Dyna ST70, I personally preferred the FE126En closer to the wall and driven in triode mode, and the Mark Audio drivers further away and with the amp in U/L mode.

Part of that is down to more optimumal damping for the FE126. As i try a bit more damping with the MA drivers i expect they will want to get closer to the wall.

dave
 
frugal-phile™
Joined 2001
Paid Member
By loading the Sketchup model and using the tape measure tool, I'm seeing that the tilt back from vertical is 3" at the top front edge, and the rear edge of the top of the cabinet side is 10.25" back from the vertical axis. I'd hold off cutting until you get that confirmation from the designers. You beat me to this question. :)

5 degree cuts are probably close enuff... careful full scale layout is suggested.

With this question, i will adjust the origin of the side panel on the grid drawings and re-insert them into the beta doc. Some key cartesian points will also be noted, to make layup easier.

dave
 
frugal-phile™
Joined 2001
Paid Member
Planet 10,
What speaker are you prepping this design for. What kind of distance from the wall should be considered with these. May be willing to be a beta builder.

We have tried it with, and shown that it works, with a wide range of (4-4.5") drivers. Now up to builders to try their favorites.

I hope to see a broad sweep of drivers implemented.

Versions of FH for larger drivers is premature at this time.

dave
 
I got a pair of cabinets roughed up today. I'll add stuffing and attach the sides tomorrow. Since I plan to use a supra-baffle, I made the opening for the driver oversize and back chamfered.
In my impatience I selected a sheet of veneered red oak...bad choice...I should have driven the next 25 miles to get baltic birch. The lack of quality in the veneer made the cross cuts a splintery mess. I am now reminded not to try that again for awhile. :headbash: