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In late 2006 – ’07 a small group of enthusiasts collaborated to develop a compact, inexpensive<br />
corner-horn design for the DIY community. This project became the very successful<br />
<strong>Frugel</strong>-<strong>Horn</strong>, which even spawned an extremely expensive commercial adaptation.<br />
The <strong>Frugel</strong>-horn <strong>Mk3</strong> [FH3] is a ground-up new design, with the objectives of improving upon<br />
the performance of the original box in a substantially simpler cabinet that would be tolerant<br />
of a wide range of drive units. Topologically, it is a tapped hypex corner-horn (approximated<br />
by 2 conical sections) with an internal choke serving as a low pass filter. The curved terminus is<br />
carried over from Ron Clarke’s contribution to the original cabinet, and helps the wavefront<br />
exiting the horn mouth to return to its more natural spherical shape.<br />
The cabinet has to date been successfully tested with Fostex FE126En, FE126e, FE127e,<br />
FE138eSR*, Mark Audio CHR-70, CHP-70, Alpair7, CSS EL70, and Tangband W5-1611. Suitable<br />
drivers should fall into, or be near the envelope of parameters defined by this set of drivers.<br />
Additional drivers will be added to the above list as and when they are tested. Adjustment &<br />
tuning of the cabinet is accomplished with varying amounts of damping, and proximity to rear<br />
boundary walls / corners.<br />
* (this driver does bass really well in FH3, but has other issues which preclude it being recommended)<br />
FH3 is made freely available for DIY builders to make their own cabinets; we see it as an<br />
introduction to back-loaded horns, from which people may wish in future to move on to larger<br />
and / or more complicated designs.<br />
Use of deflectors & supraBaffles yet to be explored.<br />
<strong>Frugel</strong>-<strong>Horn</strong> <strong>Mk3</strong><br />
25-february-2012 | © 2010, 2012 Frugal-<strong>Horn</strong>.com<br />
Note: any commerical entity intent on manufacturing complete speakers or flat-paks for<br />
resale will need to follow the guidelines on the Frugal-<strong>Horn</strong> site:<br />
www.frugal-horn.com/use.html<br />
This project’s contributors:<br />
DIYers who went ahead, assisted in beta testing, offered comment and suggestions<br />
diyAudio: host for interactive discussion threads<br />
Scott Lindgren design & documentation<br />
Ron Clarke: the curved mouth<br />
Chris Bobiak: Original test builds & drawing contribution<br />
Colin Topps: drawing contribution<br />
Your name here: you can help with FAQ, assembly diagrams & pictures, photo gallery.<br />
Probably more.<br />
Local cottage industry to make & distribute flat-paks encouraged, please contact Dave<br />
(david@planet10-hifi.com)<br />
Drawings/Contents (provisional)<br />
i0/ Intro<br />
i1/ Pictures<br />
i2/ Notes<br />
FH3-0/ Plan 15mm<br />
FH3-0.1/ Details 15mm<br />
FH3-1/ Plan 15mm + 18mm baffle<br />
FH3-2/ Plan 18mm<br />
FHx/ Plan 5/8”<br />
FHx/ Plan 3/4”<br />
FH3-5/ Alternate Choke Point Execution<br />
FH3-6/ Side pattern creation<br />
FH3-7/ Side template (metric 15mm)<br />
FH3-8/ Side template (imperial 15mm)<br />
FH3-9/ swappable supraBaffle (updated)<br />
D-0/ Damping<br />
D-1/ full size side felt template (15mm)<br />
C-0/ 5x5 15mm cut plan<br />
C-1/ 4x8 15mm cut plan<br />
C-2/ 4x8 18mm simple cut plan<br />
C-3/ 4x8 18mm cut plan (updated)<br />
C-4/ 4x8 18mm alternate cut plan (updated)<br />
please email me with<br />
corrections & suggestions to make this document<br />
more useful<br />
Major Sponsors<br />
& Cheerleaders
Pictures<br />
25-february-2012<br />
more pictures at http://www.diyaudio.com/forums/full-range/199849-fh3-build-gallery.html
Notes<br />
———————————————————————————————<br />
'/ quality multi#ply/plywood is recommended& In general" void free"<br />
the greater number of plies the better<br />
,/ reference build is ,6mm plywood" to allow rebate for some drivers<br />
,%mm ba7es recommended 0ie Alpair 81<br />
+/ if MDF or particle board used a minimum panelthickness of ,%mm"<br />
good multi#ply minimum ,+mm<br />
)/ the most di9cult detail in the build is the joint at the bottom of<br />
back" inside divider& A number of means to achieve this are detailed<br />
$/ a removable vestigial supraBa7e is shown that allows<br />
experimentation with di-erent drivers<br />
6/ a full size supraBa7e can be added as shown in the <strong>Frugel</strong>#<strong>Horn</strong><br />
Mk, document<br />
*/ A full height rear de.ector based on that shown in the <strong>Frugel</strong>#<strong>Horn</strong><br />
Mk, document can be added<br />
8/ a stealthWoofer based on a full#height de.ector is under<br />
development&<br />
Donations<br />
————————————————————————————<br />
<strong>Frugel</strong>#<strong>Horn</strong>s have always been free for DIY builders to<br />
construct& We received many inquiries by buiders who wanted<br />
to send some money& For this iteration we would encourage you<br />
to pay it forward with a donatation of money or time to some<br />
charitable organization& Listed below are some choosen by the<br />
three main contributors to the design & documentation&<br />
Quite literally" every little helps&<br />
Royal British Legion: www&britishlegion&org&uk<br />
Alzheimer!s Research UK: www&alzheimersresearchuk&org<br />
Cancer Research UK: www&cancerresearchuk&org<br />
Donor!s Choose: www&donorschoose&org<br />
Save The Children: www&savethechildren&org<br />
Big Brothers Big Sisters: www&bbbs&org<br />
Chris ,<br />
Chris +<br />
Chris )<br />
———————————————————————————————<br />
for those without major woodworking kit" a growing number of<br />
independent .at#pak vendors ar ecoming on#line& Canada 0North<br />
America1" Netherlands & UK 0Europe1 & Australia as of this document<br />
revision<br />
Notes<br />
)'#september#+',,<br />
Comments & tips pulled form forum posts<br />
———————————————————————————————<br />
Bob Brines:<br />
Taking Colin!s diagram !sheet C"#$" here is how I would one#man it<br />
out of a $x% panel&<br />
'& Build yourself a T#square cutting guide out of scrap material& You<br />
can (nd the instructions out there on the Internet&<br />
''& I have a )!x*! sacri(cial table top on a pair of saw horses& I can still<br />
manage to get a $x% sheet of plywood on it" but I can no longer get a<br />
sheet of MDF on it& For MDF" I just drop the sheet on the driveway<br />
and put $ +x$!s under it&<br />
,& With a circular saw" cut o- the $ ,$'mm pieces&<br />
+& Cut between the remaining doubled pieces&<br />
)& Now you can rip the individual pieces on a table saw as long as you<br />
can rig some kind of out.ow table& I have a jig that (ts my router<br />
table so that it can double as an out.ow table for the table saw& Of<br />
course" if you don!t have a table saw" you can do this with a circular<br />
saw and the rip fence you made above&<br />
You can get the two cross cuts done at Lowes!/HD 0speaking to the<br />
USA now1" but my experience is that their panel saws are not square<br />
in any axis and I have to re#cut the ends& Also" the utility blade in their<br />
saw really tears up the cut& I have a *' tooth blade in my circular saw<br />
that does an acceptable job& Not as good as the %' tooth blade in my<br />
table saw" but acceptable&<br />
That!s my technique& YMMV&<br />
Bob<br />
———————————————————————————————<br />
PDRCanada:<br />
Another tip for cutting sheet goods on saw horses&&&&&&<br />
Go to your nearest hardware store buy a +!x$! pc of + or )2 white<br />
styrofoam and a roll of duct tape&<br />
Cut the stryo to match the top of your saw horses&&&&&&use the duct<br />
tape to fasten it around the top of the horse&<br />
You can now cut your sheets with out hanging them over the saw<br />
horses& Just cut thru the styro&&&&&make sure your styro is deeper than<br />
your saw cut&<br />
When the styro gets beat up&&&remove and replace&<br />
This method is used on jobsites all over to cut large panels&<br />
———————————————————————————————<br />
Poultrygeist:<br />
A3er much frustration in searching for ,/+ 4 0 ,+mm 1 cotton or wool<br />
felt I found an unlimited supply at my local auto junk yard& The carpet<br />
backing from ,55'!s Fords is ,/+ inch thick" works great and costs<br />
nothing& Had it not been up for sale I would have scavenged my own<br />
Mustang but instead I found a F,6' donor which surrendered enough<br />
felt for a herd of horns&
'<br />
6$ &"07<br />
!/#& mm<br />
radius 1-234<br />
/'<br />
6$ &"07<br />
0*2°<br />
&5<br />
6! !"$7<br />
002<br />
6!/ !!"!-7<br />
Notes:<br />
!" drawn with !#mm material<br />
$" optional %&'' mm wide"diameter supra(ba)e not<br />
shown* Its purpose is to move the ba)e(step drop o+ to<br />
where the horn action starts ,attening lower midrange FR<br />
&" intended for Fostex FE!$-En. CHR(/'. Alpair /. EL/'<br />
0" damping will di+er for each driver<br />
!/!<br />
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sheet FH&(' 8 !#mm Plan<br />
designed by S Lindgren 9 drawn by dld<br />
$/(september($'!!<br />
© $'!'. $'!! Frugal(<strong>Horn</strong>*com<br />
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sheet FH'.(/! % details !#mm<br />
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angle cut on the inside of rear panel can be cut on table saw<br />
with tenoning jig and blade set to #deg or carefully sanded<br />
!#mm radius<br />
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where the horn action starts ,attening lower midrange FR<br />
&" intended for Fostex FE!$-En. CHR(/'. Alpair /. EL/'<br />
0" damping will di+er for each driver<br />
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<strong>Frugel</strong>(<strong>Horn</strong> Mk& !v'<br />
sheet FH&(! 8 !#mm Plan w !5mm<br />
ba)e<br />
designed by S Lindgren 9 drawn by dld<br />
$/(september($'!!<br />
© $'!'. $'!! Frugal(<strong>Horn</strong>*com<br />
!/'<br />
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Notes:<br />
!" drawn with !#mm material<br />
$" optional %&'' mm wide"diameter supra(ba)e not<br />
shown* Its purpose is to move the ba)e(step drop o+ to<br />
where the horn action starts ,attening lower midrange FR<br />
&" intended for Fostex FE!$-En. CHR(/'. Alpair /. EL/'<br />
0" damping will di+er for each driver<br />
!20<br />
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sheet FH&($ 8 !5mm Plan<br />
designed by S Lindgren 9 drawn by dld<br />
$/(september($'!!<br />
© $'!'. $'!! Frugal(<strong>Horn</strong>*com<br />
!/-<br />
6- !#"!-7<br />
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6# !"$7
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$% &%'(&)<br />
Note: example uses !%mm material<br />
As originally designed<br />
A di*cult piece to cut<br />
Modi+ed for easier build<br />
Adds an additional piece, not all that tolerent<br />
of thicker material<br />
Alternateeasier build<br />
Overcomes material thickness issues-<br />
Requires extra material . !'& round with<br />
radius of build material<br />
<strong>Frugel</strong>/<strong>Horn</strong> Mk( !v0<br />
sheet FH(/% . alternate choke point<br />
execution<br />
designed by S Lindgren 1 drawn by dld<br />
&#/september/&0!!<br />
© &0!0, &0!! Frugal/<strong>Horn</strong>-com
!""<br />
#$% $&!'<br />
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<strong>Frugel</strong>2<strong>Horn</strong> Mk$ )v4<br />
sheet FH$2( 5 curve chord & height<br />
designed by S Lindgren 6 drawn by dld<br />
*32september2*4))<br />
© *4)4+ *4)) Frugal2<strong>Horn</strong>1com<br />
To fabricating a side panel template by<br />
hand+ the curve can easily be drawn<br />
using a narrow ,exible board -)&./ MDF<br />
works great0 and the . points as<br />
dimensioned1<br />
Mark points A+B -chord ends0+ C -chord<br />
centre line0 and D -segment height0<br />
on the work2piece1 Use a square to draw a<br />
perpendicular line -C2D0<br />
Clamp or screw a wood block straddling the<br />
centreline at D+ clamp the<br />
,exible board to this block and each end of<br />
the chord - A & B0 then draw<br />
the curve1<br />
Cut to the outside with jig or band saw+ and<br />
carefully sand to line
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sheet FH('* / side pattern 0&cm grid1<br />
designed by S Lindgren 2 drawn by dld<br />
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<strong>Frugel</strong>-<strong>Horn</strong> <strong>Mk3</strong> 1v0<br />
sheet FH3-9 – removable supraBaffle<br />
(15mm)<br />
designed by C Bobiak | drawn by dld<br />
26-november-2011<br />
© 2010, 2011 Frugal-<strong>Horn</strong>.com<br />
Notes:<br />
0/ drawn with 18mm panels<br />
1/ shown on FH3 in 15mm material<br />
2/<br />
these dimensions allow for a small gap<br />
to accomodate veneer,laminate etc, if<br />
needed the wings can be made tight to<br />
the sides and the vertical edges can be<br />
sanded flush.<br />
85<br />
[3 11/32]<br />
86<br />
[3 3/8]<br />
cut out on backside of sB is<br />
20mm down from the top<br />
(15mm pnels, would be<br />
23mm down with 18mm<br />
panels)<br />
200<br />
[7 7/8]<br />
BaffleCutout<br />
175<br />
[6 7/8]<br />
115<br />
[4 17/32]<br />
208<br />
[8 3/16]<br />
120<br />
[4 23/32]<br />
70<br />
[2 3/4]<br />
165<br />
[6 1/2]<br />
110<br />
[4 11/32]
!"#$ %!#mm& cotton or wool felt<br />
!" FE!#3En blue 4 orange<br />
#" CHR5, blue 4 orange 4 #,.2,g<br />
+" EL5, blue 4 orange 4 #,.2,g<br />
2" A5 blue 4 orange 4 #,.2,g<br />
starting point 8 +,<br />
grams of poly(u) -<br />
average ,'9 lbs'01+<br />
%yellow 4 green&<br />
poly.(u) %BAF/ acoustistu)/ pillow stu6ng .. di)erent<br />
colours represent di)erent 7zones$ to add stu6ng too&<br />
increasing density as you approach<br />
the point' Take the equal density<br />
(u) on the right and squeeze it into<br />
the point %*+,g - ! oz &<br />
<strong>Frugel</strong>.<strong>Horn</strong> Mk+ !v,<br />
sheet D., 8 damping plan<br />
designed by S Lindgren : drawn by dld<br />
#5.september.#,!!<br />
© #,!,/ #,!! Frugal.<strong>Horn</strong>'com<br />
walls lined around driver to minimize<br />
re(ections<br />
this is the area subject<br />
to additional poly.(u)<br />
damping/ depends on<br />
driver<br />
see notes page ix for<br />
driver.by.driver<br />
%at !"# lb"01+ this<br />
volume would need<br />
*2,g %!'2 oz& of (u)
!*&<br />
+, !.%/&-<br />
Full Size when printed at !""#<br />
Remember these need to be mirror image pairs<br />
Note:<br />
speci$cally for !%&' felt material as relevant to planet!"(hi$ )atpak kits<br />
!,*<br />
+0 !%!0-<br />
<strong>Frugel</strong>(<strong>Horn</strong> Mk/ !v"<br />
sheet D(! 1 Side felt template 2!,mm3<br />
designed by S Lindgren 4 drawn by dld<br />
&5(september(&"!!<br />
© &"!"6 &"!! Frugal(<strong>Horn</strong>7com<br />
!*"<br />
+, !%&-
$/%<br />
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Notes:<br />
$( 'mm kerf & trim allowance<br />
)( very tight cut plan<br />
1$'<br />
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*/$<br />
-)2 '(#)0<br />
internal<br />
internal<br />
back<br />
back<br />
bottom top<br />
ba!e<br />
<strong>Frugel</strong>"<strong>Horn</strong> Mk# $v%<br />
Sheet C"% & 'x' $'mm cut sheet<br />
layout by Chris Bobiak<br />
drawn by dld ( )*"sept")%$$<br />
© )%$%+ )%$$ Frugal"<strong>Horn</strong>,com<br />
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Sheet C!# % &x'( #)mm cut sheet<br />
layout by David Dlugos<br />
drawn by dld * +,!sept!+$##<br />
© +$#$- +$## Frugal!<strong>Horn</strong>.com<br />
Notes:<br />
#* )mm kerf & trim allowance<br />
+* room to increase kerf for CNC<br />
"* works for #++$x+&&$mm sheets
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Cut !<br />
Cut '<br />
Cut *<br />
Cut "<br />
Cut %<br />
Cut 5<br />
Then cut out the<br />
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sides out of<br />
<strong>Frugel</strong>)<strong>Horn</strong> Mk* !v#<br />
Sheet C)' + "x,- !,mm simple cut<br />
layout by Colin Topps<br />
drawn by dld & '.)sept)'#!!<br />
© '#!#/ '#!! Frugal)<strong>Horn</strong>0com<br />
Notes:<br />
!& %mm kerf & trim allowance<br />
'& minimal cuts to break up the sheet 1ie<br />
at the lumber shop2 Dimensions<br />
rounded up to the closest higher mm or<br />
!&,3
869<br />
[34 3/16]<br />
baffle<br />
baffle<br />
195<br />
[7 11/16]<br />
140<br />
[5 1/2]<br />
830<br />
[32 11/16]<br />
back back<br />
top<br />
top<br />
459<br />
[18 1/16]<br />
bottom<br />
bottom<br />
internal<br />
internal<br />
756<br />
[29 3/4]<br />
140<br />
[5 1/2]<br />
<strong>Frugel</strong>-<strong>Horn</strong> <strong>Mk3</strong> 1v0<br />
Sheet C-4 – 4x8’ 18mm alt cut<br />
layout by David Dlugos<br />
drawn by dld / 25-february-2012<br />
© 2010 – 2012 Frugal-<strong>Horn</strong>.com<br />
Notes:<br />
1/ 5mm kerf & trim allowance<br />
2/ room to increase kerf for CNC<br />
3/ works for 1220x2440mm sheets
459<br />
[18 1/16]<br />
195<br />
[7 11/16]<br />
top<br />
top<br />
bottom<br />
bottom<br />
baffle<br />
140<br />
[5 1/2]<br />
baffle<br />
back<br />
optional parts for a 36mm<br />
tall stabalization base<br />
back<br />
406<br />
[16]<br />
internal<br />
279<br />
[11]<br />
internal<br />
460<br />
[18 1/8]<br />
140<br />
[5 1/2]<br />
756<br />
[29 3/4]<br />
830<br />
[32 11/16]<br />
869<br />
[34 3/16]<br />
<strong>Frugel</strong>-<strong>Horn</strong> <strong>Mk3</strong> 1v0<br />
Sheet C-3 – 4x8’ 18mm cut sheet<br />
layout by David Dlugos<br />
drawn by dld / 25-feb-2012<br />
© 2010, 2011, 2012 Frugal-<strong>Horn</strong>.com<br />
Notes:<br />
1/ 5mm kerf & trim allowance<br />
2/ room to increase kerf for CNC<br />
3/ works for 1220x2440mm sheets<br />
4/ optimized for maximum offcut not<br />
easiest cutting & maintaining grain<br />
matching