Frugal Horm - FH3 - MarkAudio CHR70A

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rbalu72

Active Member
Joined
Jan 29, 2014
Messages
101
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Location
Hyderabad
I just started building my FH3 (Frugal Horn)

Material used : 18mm MDF board

Tools : Manual and carpenter (tried to cut them via CNC but none of the folks ready to do this petty work and I got thoroughly frustrated with their attitude so decided to do myself)

Design:frugel-hornMk3-1v0-250212.pdf (page 7 Sheet FH3.2, Page 9, Sheet FH3.6, Page 17 Sheet C-2)

So far I have managed to cut the individual pieces for both the boxes and the dimensions I got are as below.

1. Internal - 756mm x 140mm - 2 pieces
2. Top - 195mm x 140mm - 2 pieces
3. Baffle - 869mm x 140mm - 2pieces
4. Back - 830mm x 140mm - 2 pieces
5. Bottom - 459mm x 140mm - 2 pieces
5. chokepoint - 18mm x 140mm - 2 pieces
6. Side Panels - 900mm x 459mm x 194mm - 4 pieces

Curve was made using method described in pdf and 4mm plywood by bending it slightly and cutting along the line using circular saw then little sanding..

I am assuming the two 18mm x 140mm pieces are to form the half circle if so, I need help here from FMs who already built this to confirm whether I need 2 more pieces to complete both boxes??) or

It feels like the pictures in the pdf file says the half circle is achieved by half rounding the internal boards then what for these two (18mm x 140mm) are used for?? :confused:

Now to drill hole for Drivers and then start assembling the boxes.. Any review of the sizes, suggestions, best practices, guidance highly appreciated :)


Some pics off woodwork so far:

http://i62.tinypic.com/2ecmzxk.jpg
http://i60.tinypic.com/23v1g75.jpg
http://i61.tinypic.com/vx21bn.jpg
http://i58.tinypic.com/2dl2q1u.jpg
http://i61.tinypic.com/20gb6lt.jpg
http://i62.tinypic.com/14j2t1z.jpg
http://i59.tinypic.com/2nvtqa9.jpg

Drivers:

http://i62.tinypic.com/289kmkw.jpg
http://i60.tinypic.com/am84r6.jpg
http://i59.tinypic.com/muzseb.jpg
 
Just need to assemble the boxes... other things i think are in place :) including better half :D (as what should go on the surface of boxes was left to her like colours etc)

Aiming to complete this week provided nothing urgent pops on office front.
 
I have finally assembled the FH3 boxes with screws and fixed woolenfelt, pillow stuffing wool as stated (like how i understood it :) ) and hooked it to Amp as i was curious
to test how they sing.. voila.. the default output is very good (for my ears as I dont have any other to benchmark) and probably some local expert FM may have to audtion this
and see what fine tuning can be done on top of this.

BTW, I tried to source the woolen felt local in Hyd (thanks for all the folks who helped in this process) and finally I had to disturb the brothers to send that
from Cochin (as I felt cost of roaming around Hyd for it in car is much more than what it actually costs) and as usual they did a fantastic job of dispatching that on time.

One question: Do we need to make the boxes air tight except at the bottom rear side where the vent is available (as these are not cnc cut some very minor gaps i could notice at few places) ?? Please advise.
Also please suggest any improvements of adjusting the stuffings (dencity, placement etc) or otherwise after looking at pictures.. Thanks.


Build and pictures of progress so far:

http://i61.tinypic.com/11gk3tt.jpg
http://i58.tinypic.com/2e3n7h5.jpg
http://i59.tinypic.com/2ito2ab.jpg
http://i58.tinypic.com/23uo9px.jpg
http://i58.tinypic.com/970l6x.jpg
http://i57.tinypic.com/fdw19w.jpg
http://i58.tinypic.com/2q3c5t5.jpg
http://i60.tinypic.com/2ah76ol.jpg
http://i62.tinypic.com/15n2iaa.jpg
http://i61.tinypic.com/mc9h04.jpg
http://i59.tinypic.com/33dxjdw.jpg
http://i60.tinypic.com/2ldddug.jpg
http://i61.tinypic.com/2drc8r7.jpg
http://i59.tinypic.com/ephaw3.jpg
http://i59.tinypic.com/34owk93.jpg




Still to do:

1. fine tuning
2. fixing panels permanently with glue
3. Fixing speaker posts, feet for boxes
4. Finishing with decolam or something similar outside
 
rbalu72 said:
I have finally assembled the FH3 boxes with screws and fixed woolenfelt, pillow stuffing wool as stated (like how i understood it :) ) and hooked it to Amp as i was curious
to test how they sing.. voila.. the default output is very good (for my ears as I dont have any other to benchmark) and probably some local expert FM may have to audtion this
and see what fine tuning can be done on top of this.

BTW, I tried to source the woolen felt local in Hyd (thanks for all the folks who helped in this process) and finally I had to disturb the brothers to send that
from Cochin (as I felt cost of roaming around Hyd for it in car is much more than what it actually costs) and as usual they did a fantastic job of dispatching that on time.

One question: Do we need to make the boxes air tight except at the bottom rear side where the vent is available (as these are not cnc cut some very minor gaps i could notice at few places) ?? Please advise.
Also please suggest any improvements of adjusting the stuffings (dencity, placement etc) or otherwise after looking at pictures.. Thanks.

Still to do:

1. fine tuning
2. fixing panels permanently with glue
3. Fixing speaker posts, feet for boxes
4. Finishing with decolam or something similar outside
Click to expand...

They look very nice and congrats on the job well done :clapping:. Yes the cabinet should be dead air tight. Make use of silicon gel or even mixing fevicol+saw dust for big gaps, will do the job. Make sure to make it air tight especially at the binding post where the chances of air going out is higher. I have used some one sided tape (gasket tape) that you can stick to the rear of the binding post cups and then screw it so that no air escapes from the gaps.
Edit: I think you have not used binding post cups but instead direct speaker wire.
 
Last edited:
Yes, in the final version, i will fix those.. i do have couple of them sourced from diyaudiocart, looking for equipment to put that big hole on back panel :)
 
rbalu72 said:
Yes, in the final version, i will fix those.. i do have couple of them sourced from diyaudiocart, looking for equipment to put that big hole on back panel :)
Click to expand...

Ok good idea, hope you would have seen the pictures of my build with the binding post cup. What I did is measure the internal dimensions of the cup for the cut and mark it on the appropriate place of the cabinets (both internal/external marks). Then use a drill and make holes at all the 4 corners. Use a saw blade (thick metal strip kind) and cut it along the markings. Make sure that you cut it slightly inside the mark and then use a good quality sand paper and rub the extra portion to a fine finish. It takes a bit more time but the end result will be far better. This way you can even make sure that the edges of the holes are curved to fit the cups perfectly. I did this in about couple of hours time. No need to use any fancy tools for this :lol:
 
rbalu72 said:
Actually the postings are round in shape :)
Click to expand...

Hmm, then in that case I think you can get the round bit and if possible the entire set which comes to around 300/-. This set comes with the holder set which can be connected to the drilling machine. If I am not wrong it will have round bits of different sizes with a total set of around 6 to 7 bits. If any of these fits perfectly as per your cup dimensions then well and good otherwise as I mentioned in my earlier post just use a smaller bit and use sand paper to make perfect fit.
 
Sorry rbalu72 ,
Requesting to change the links to the photos to a better hosting sites.
the sites seems very annoying , it shows up all the adv but never the actual image!
 
 
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