DIY sculptured foam grilles: you can do this!!!

[turboyam]

I tried my luck on making loudspeaker grilles reproductions myself.
Now, i am NOT trying to "steal" business from Sonofagon ( Foamspeakergrilles.com) or others.
A few years back, i bought some absolutely awesome JBL L-100 Quadrex foam grilles, in blue,
that were nothing short of perfect!. These guys sell them for quite a bit of $ but i know why now!!!.
I have no clue what method they use (CNC milling or hot wire cutting) but it IS a challenge.
Perfectly doable tho, if you have a minimum of tools and patience.

I fabricated a hot wire cutting "tool" myself and i must say that it performs very well. I will post
pictures of the tool i made and the inspirational video link i used, to make this.
For my first try, i bought 1.5inch thick open cell foam, which is "rated" at 20PPI (20 Pores Per Inches). I DO NOT recommend using this PPI rating, this was a mistake on my part, the place from where i got that foam had the 1.5inch thick i needed altho, 1.25 inches would be ok.
The 20PPI foam i used is NOT acoustically transparent enough. It also is availlable in grey only
(open cell Reticulated foam is not availlable in a lot of colors it seems), so you'll have to paint it
with the color you want. Painting that 20PPI makes it even less transparent acoustically.

I know that vintage (and modern replacement) foam is closer to 10PPI and that is WAY better
acoustically, lends itself way better to painting and, looks better.
The best way to color the foam would be to use clothes Die, but i doubt that it's going to work
as the foam won't absorb the die (someone tried to die foam???).
JBL, Altec, Marantz, B.I.C. and every one else probably all painted the foam ( i know that JBL did).
The fun part is that you can paint them any colors you'd want!, even black if retro-colors is not your thing.
I made the "jiggs" to cut the foam using MDF and Masonite as, using plastics (would melt), or metals (would cool- down the wire). In the linked video, the guy uses thin aluminum so, it might work...

To power my hot wire cutter, i used my DC power supply. It is adjustable from 0 to 20VDC but using too much voltage, gives worsening results (wire is too hot). I found that for a 22inch long wire, 12volts DC is working best, making this doable with a car battery maybe? or a car battery charger...
On my power supply, the power needed was 3amps@ 12 volts. Some wallwarts can supply that,
YMMV. The Hot cutting wire i used is: Temco RW0036 26 guage Nichrome60 wire. I bought a 25 ft rool and it is in-expensive. You could use a different guage but the smaller-the better i think.
This special wire is made to be heated. I imagine you could try stainless steel wire but i did not try.
After every cuts, i cleaned the wire with fine steel wool.

Cutting slots in the foam is very easy!, cutting large, flat surfaces (like the B.I.C. Venturi Formula 3 grilles sides) is more challenging. You need practice on a scrap piece of the same foam, to check the voltage and speed at which you "feed" your cutting tool.

Someone knows a source for thick (depending on the grilles you need to make) reticulated 10PPI open cell foam???.
Ideally, grey foam for black, brown grilles and white foam for vibrant, burnt orange, blue and light colors... The grilles pictured are grey still. I have to chose the color, maybe blue!?...
I will post more pictures and details soon.

 

[turboyam]

 

[turboyam]

 

[turboyam]

Sorry about double picture post and image quality.
The name of the game is patience!. The more time you spend on making the "jigg" and be steady and precise, handling the cutting tool, the better the results.
No doubt that, with a propper jigg, you could do JBL L-100 Quadrex or nice vintage copies or, your own designs!.
I will post pictures of the grilles i made once painted.
I had some inexpensive B.I.C. emblems made (plastified white printed cardboard) that look good too!, to install on the grilles.
Here's the Venturi's i copied;

 

[turboyam]

The inspiration video that i used to copy the cutting tool.

 

[turboyam]

Fabricating the tool: i used an old steel broom stick and mdf ( the 'arc' has to be non-conductive). I made it so it can be adjustable in lengt, to acomodate different grilles sizes.
Of course, if you fabricate this tool, you can use it to do whatever with air foam OR styrofoam sculptures and all!.
Having a switch on the tool is nice and looong wires (i used 16guage).
Make one end of the cutting wire adjustable to put tension on the wire and the other end, with a tension spring to take-up the slack from wire heating expension.

If you have the right voltage and go to a nice slow pace, it will cut foam like butter.
I used planks (pictures) on top of the foam, to old it down, and the "jig" to hold it sideways so it stays put.

Here is the type of foam i should have used;https://www.foamparts.com/materials/1790/
This is to give you an idea, i did not use this particular one. For the B.I.C. Venturi type grills, i needed 1.5inch thick for the center section. The sides are bevelled.

Anyone here has suggestions on a reticulated, 10PPI foam supplier?. One that can provide thickness options?.

 

[turboyam]

Decided to paint one pair (i made 2 pairs now), in orange, to copy JBL's burnt orange grilles. Yes, they are orange all right!. The pictures don't do them justice tho, they look all-right. I made a vacuum "box" to avoid excess paint just "pooling" on top of the too small 2PPI foam i had. I was afraid thay the paint would just block- off the surface pores. The system works great!. I simply cut a hole in a cardboard box, that fits the grills in size and used my thrusty ShopVac, to create a vacuum underneat the foam. The airflow seems to pull the paint droplets (from a rattle can), thru a good part of the foam thickness and there is no build-up on the foam's surface.
This step is probably pointless if we were to use 10PPI foam tho.

This week, i will paint the second pair ( they are better made), in blue and see the results.

 

[gizzyman47]

Nice! Thanks for the time to show and explain the process.

 

[The Fuxtor]

Pretty cool stuff! Love diy

 

[totem]

Well done, nice DIY project.

 

[doctorolds]

Thanks for sharing your project and information @turboyam! I have no need at the moment, but I may create some grills in the future for custom cabinets.

 

[turboyam]

In blue: They look really nice in person, i'm happy!.
The orange paint i used: Krylon Pumpkin Orange # 45532 (color Maxx)
The blue i used; Home Hardware Beauti-Tone in New Holland Blue # 1823-020

 

[turboyam]

A lot of other manufacturers had models with foam grilles back then; JBL, Altec Lansing, B.I.C., Acoustic Research, Cerwin Vega (HED), Marantz, and more. From the models i've seen, (in pictures), the Marantz HD series seems the most challenging to DIY.
The Acoustic Research ( AR10?), HED H-10, 12 and 15 are very easy, all B.I.C Venturi Formulas, Altec five, seven and nine, look easy ( need to cut a "cone" for the badge).
The challenge is to get the right measurments and make the Jigs with the sculpture profiles, the hot wire will do the rest!.

I did not paint the back of my grilles, and i do not recomend painting that part too (acoustical transparency).
Good luck if you try this out, i certainly don't regret it!!!

 

[turboyam]

Found this seller; New England Foam. They have a standard 118" X 48" X1.5 sheet of 10PPI charcoal color reticulated foam. They can cut these to custom sizes. The idea tho is to buy a bit more then what's needed and hot-wire cut it to match what you need.
Not all grilles need a 1.5inches thick foam tho!!!, buy the Maximum thickness you need only.

 

[revox-b77]

Pulling paint fumes through a shop vac could lead to an explosion.

Your grills look very good!

 

[turboyam]

Pulling paint fumes through a shop vac could lead to an explosion.

Your grills look very good!

Thank you!. Contrary to popular belief, the motor in vacuum cleaners, is isolated from the bag/ container exactly to prevent this. Even the Myth Busters proved it!.

 

[djnagle]

Too funny. I read the title of the tread as gorillas not grills. I read through the whole thread and not once saw gorillas mentioned.

 

[markkb]

Great information, thanks for posting.

 

[RoundRock]

I tried my luck on making loudspeaker grilles reproductions myself.
Now, i am NOT trying to "steal" business from Sonofagon ( Foamspeakergrilles.com) or others.
A few years back, i bought some absolutely awesome JBL L-100 Quadrex foam grilles, in blue,
that were nothing short of perfect!. These guys sell them for quite a bit of $ but i know why now!!!.
I have no clue what method they use (CNC milling or hot wire cutting) but it IS a challenge.
Perfectly doable tho, if you have a minimum of tools and patience.

I fabricated a hot wire cutting "tool" myself and i must say that it performs very well. I will post
pictures of the tool i made and the inspirational video link i used, to make this.
For my first try, i bought 1.5inch thick open cell foam, which is "rated" at 20PPI (20 Pores Per Inches). I DO NOT recommend using this PPI rating, this was a mistake on my part, the place from where i got that foam had the 1.5inch thick i needed altho, 1.25 inches would be ok.
The 20PPI foam i used is NOT acoustically transparent enough. It also is availlable in grey only
(open cell Reticulated foam is not availlable in a lot of colors it seems), so you'll have to paint it
with the color you want. Painting that 20PPI makes it even less transparent acoustically.

I know that vintage (and modern replacement) foam is closer to 10PPI and that is WAY better
acoustically, lends itself way better to painting and, looks better.
The best way to color the foam would be to use clothes Die, but i doubt that it's going to work
as the foam won't absorb the die (someone tried to die foam???).
JBL, Altec, Marantz, B.I.C. and every one else probably all painted the foam ( i know that JBL did).
The fun part is that you can paint them any colors you'd want!, even black if retro-colors is not your thing.
I made the "jiggs" to cut the foam using MDF and Masonite as, using plastics (would melt), or metals (would cool- down the wire). In the linked video, the guy uses thin aluminum so, it might work...

To power my hot wire cutter, i used my DC power supply. It is adjustable from 0 to 20VDC but using too much voltage, gives worsening results (wire is too hot). I found that for a 22inch long wire, 12volts DC is working best, making this doable with a car battery maybe? or a car battery charger...
On my power supply, the power needed was 3amps@ 12 volts. Some wallwarts can supply that,
YMMV. The Hot cutting wire i used is: Temco RW0036 26 guage Nichrome60 wire. I bought a 25 ft rool and it is in-expensive. You could use a different guage but the smaller-the better i think.
This special wire is made to be heated. I imagine you could try stainless steel wire but i did not try.
After every cuts, i cleaned the wire with fine steel wool.

Cutting slots in the foam is very easy!, cutting large, flat surfaces (like the B.I.C. Venturi Formula 3 grilles sides) is more challenging. You need practice on a scrap piece of the same foam, to check the voltage and speed at which you "feed" your cutting tool.

Someone knows a source for thick (depending on the grilles you need to make) reticulated 10PPI open cell foam???.
Ideally, grey foam for black, brown grilles and white foam for vibrant, burnt orange, blue and light colors... The grilles pictured are grey still. I have to chose the color, maybe blue!?... View attachment 2269454
I will post more pictures and details soon.

Found the text below on http://www.troelsgravesen.dk/JBL_L100.htm regarding how the JBL L100 foam grilles were originally shaped/cut. ----------------------------------------------------------------------------------------------------------------------------------------------------------- Dear Mr. Gravesen. I truly admire the work you have done to upgrade the JBL L100 Loudspeaker. It’s sort of like you’ve given an old man a new heart. I am retired now, but I worked in the audio/consumer electronics manufacturing industry for forty years – from 1960 – 2000. During the 1960’s I was Vice-President of Engineering Administration at JBL. I am not an engineer – but I did direct the L100 development program. L100 Design Engineer Ed May was a very dear and close friend. I coordinated the work of industrial design consultant, Arnold Wolf – who, with Doug Warner, was responsible for the visual design. Arnold later went on to become President of JBL and my boss. Larry Phillips created maybe the best audio promotion program ever: “Wednesday for Trombones, Thursday for Drums.” Years later, when I was introduced to Mark Levinson engineer, Tom Colangelo – Tom – smiling when he heard about my past JBL work experience, simply smiled and spoke that now famous marketing phrase. The best L100 story “never told” is that of JBL draftsman/audio enthusiast Carl Davis from Ottumwa, Iowa. Ed May told us all that microphone wind screen foam material would make an acceptable grille material. Arnold Wolf gave us stunning designs. The problem was that the foam industry was basically the packaging and filtering industry. Pressure cutting foam tolerance was about +/- .25 inch. No foam vendor could meet Arnold’s design requirements. Carl Davis, without degree, without assignment and working on weekends – was the first – in the entire industry – to discover that foam could be hot wire cut – and with the required precision. The L100 project had lingered more than six months in limbo while we struggled with the grille design problem. Meanwhile, the L100 market got off to a head start when studios began ordering 50 to 100 pairs of walnut 4310’s. We all knew an unauthorized distribution process was under way. Thanks for giving me a reason to look back, Jim Barthell -----------------------------------------------------------------------------------------------------------------------------------------------------------