Foam Core Board Speaker Enclosures?

Founder of XSA-Labs
Joined 2012
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Has anyone tried using foam board (paper laminated with foam core) as quick and dirty speaker enclosures? There is something really satisfying in using nothing more than an x-acto knife and a hot melt glue gun to build transmission lines, horns, etc to try out designs on smaller 3 in and 2 in low power full range drivers. Interestingly, they actually sound pretty good and weigh nothing compared to mdf. I am just wondering if I am the only trying this sort of stuff before cutting real wood. My latest build is a stereo pair transmission line that is very flat and hangs like a picture on a wall. Lots of fun and very quick and clean. The foam core actually has built in damping capabilities. I do find that it sometimes resonates like a guitar body but that is not necessarily bad.

I am editing this first post to show what is possible with foam core and hot melt glue - the elusive Cornu spiral horn.... Read on if you are interested in this wonderful speaker and have a day or two to try building it.

For folks in France, FC board is called "carton ou de mousse"

Erreur 404

In Germany, try here:

Attention Required! | Cloudflare


Cornu spiral BLH original vs Smooth Curve Ever think of building a Cornu Spiral horn? Now you can! - Page 3 - diyAudio

pdf plan for Cornu spiral by Planet10 can be found here: Foam Core Board Speaker Enclosures? - Page 23 - diyAudio

Micro 14in Cornu with 2in driver from Logitech S120 (Dec 2012):
Ever think of building a Cornu Spiral horn? Now you can! - Page 6 - diyAudio

Flat wall mount stereo MLTL with Vifa TC9FD

Flat BIB or FIB with Vifa

FIB alternate without V channel

Folded bookshelf MLTL with Vifa

FH3 Inspired Floorstanding Back Horn with Vifa FH3-inspired Foam Core Mini Build and here

Mini Karlsonator (0.53x Scale) with dual Vifa TC9FD's

Mini Karlsonator (0.4x Scale) with single Vifa TC9FD

Nautaloss spiral sealed-end TL Reference Monitor (200 Hz to 20 kHz) with Vifa TC9FD
The Nautaloss Ref Monitor

Teardrop Shaped Sealed Monitor (200 Hz to 20 kHz) with Vifa TC9FD

Nautaloss sealed quad driver push-pull sub:

XPS Foam & Foam Core MLTL using PE's 6.5 in Polycone Woofer (Buyouts):

The simplest FC speaker ever - "The Dual Exciter OB Cheap Thrills" speaker:

Dual Chamber Reflex with Curvy Walls - Viva la Vifa! - nice desktop monitor speaker:
Viva la Vifa! Curvy Cabinet DCR with TC9FD

Single Speaker Stereo (SSS) - matrix 3 channel:

A real 40 Hz (-3dB) 113dB SPL capable sub woofer (slot loaded band pass) that weighs less than a pound (excluding driver weight):
Light as Air Slot Loaded Band Pass Sub

A 175Hz 28in wide x 17in tall x 22in deep tractrix horn for the 5MR450NDY, a full range horn capable of 300Hz to 15kHz and +125dB:

A tractrix synergy horn - the Trynergy, the best sounding speaker I have built out of foam core to date. Perhaps my most ambitious speaker but surprisingly easy to build:

The Hypercube speaker with a TC9FD - nice 150Hz to 18kHz speaker good for HT satellites or desktop FAST:

Mass-damped Hypercube with PRV 5MR450NDY - 250Hz to 15kHz 95dB sensitive tops for a FAST:

Lance TL with RS100-4 (Dec 21, 2014):

DCR stereo Bluetooth speaker with RS100P-4 (Jan. 6. 2015):

The Dagger short TL - a very open sounding hifi FAST top (Jan 20, 2015):

XKi - X's ab initio Karlson 6th order band pass with RS100 (Jan 24, 2015):

XKi - Dual Tangband W5-876SE subwoofer (Feb 16, 2016):
XKi - X's ab initio Karlson 6th Order Bandpass

KaZba (Karlson aperture Z-baffle) Dipole FAST (March 25, 2015):

10F/8424 and RS225-8 FAST Ref Monitor (April 24, 2015)
10F/8424 & RS225-8 FAST Ref Monitor

XKi with 5in Dayton PA130-8 (Aug. 23, 2015):

Plans for Daytonator here:

FF105WK TL with trapezoidal curved baffle (Sept. 8, 2015): EVA foam for performance speaker enclosures and here
FF105WK TL for Desktop/Bookshelf

0.44x/0.55x Wide mini Karlsonator for FE103 - works great with RS40-1197 and CHN-70 (Sept. 23, 2015):

FR58EX/AC130F1 micro FAST (Sept. 28, 2015) - uses a foam core Dagger for the full range mid/tweeter:

Wall Mounted A7.3 MLTL (Oct. 4, 2015):

PMC inspired TL Monitor with DC28F and DC130A (Oct. 30, 2015):
Low-Cost PMC-inspired TL Monitor with DC130A and DC28F

GR Research X-LS 2-way speaker (Dec. 5, 2015):
Foam Core Board Speaker Enclosures?

Micro Trynergy with SB65WBAC25 and dipole bass (Dec. 22, 2015):
Presenting the Trynergy - a full range tractrix synergy.

Curvy wall Tabaq with P830986 (Dec 23, 2015):

XPS 10F/RS225 FAST TL (Dec 22, 2019):
10F/8424 & RS225-8 FAST / WAW Ref Monitor

Nano Trynergy tractrix point source with RAAL ribbon and 3FE22 (Apr. 20, 2020):
Nano-Trynergy - a Compact Tractrix RAAL Ribbon Point-Source Horn

Homage to LS3/5A (August 23, 2020):
RST28F and DC130A Foamcore Homage to LS3/5A
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Founder of XSA-Labs
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Perhaps for accuracy it is bad, but for normal listening like enjoying music in most situations it works quite well. I want to challenge the notion that speaker enclosure movement or resonance is always bad based on the fact that many music sources that listen to generate their sound from resonance and movement of the body walls: acoustic guitars, violins, cellos, etc. If you think about it, even a speaker diaphragm makes sound by moving. If the speaker cabinet moves somewhat and generates some of the sound energy, why is that bad? Why does a speaker cabinet have to be ultra dense, stiff, and weigh 20 to 100 lbs to be considered good sounding? I agree that if the cabinet resonates and rattles or hums, that is bad. But what if it moves and essentially acts as sort of a passive radiator? Just a thought because I am having a lot of good listening to some speaker cabinets that weigh ounces instead of pounds. For bass reflex or applications where significant bass pressure needs to be contained, it would not be good, but for low power applications like back loaded horns or transmission lines with full range drivers meant for less than 5 W of power, I think there is real potential here for trying things quickly, cleanly, low budget, and most of all, for having fun.
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"Has anyone tried using foam board (paper laminated with foam core) as quick and dirty speaker enclosures?"

Yes, for small enclosure prototypes I think it works good enough. I have built dozens of various experimental waveguide/transmission line designs. I braced internally for larger spans and used white gorilla glue, dries fast and strong (plus expands).:)
In the case of some musical instruments the vibrations of the enclosures do play a significant role in the sound that they produce. However, *all* examples of say guitars are not equal. So merely having vibrating parts does not insure quality. In the case of a high quality guitar a lot of effort and time, selection of materials is required.

In the case of a speaker, the goal is to reproduce the input signal at the output. Anything that adds or subtracts from that is defined as "distortion". You can have pleasant or unpleasant distortion.

Also, box losses play a role in the the way that the speaker will perform in a given enclosure.

Folks have built speakers with a variety of materials having a similar concept - the walls of the speaker playing a role in the output via vibration/resonance.

It's fine to do this, but it's what it is, not something else. :D

with respect to styrofoam and speakers i remember hearing a pair of for the lack definition planars that where made of a styrofoam back plane and a mylar membrane i don't remember what the drive assembly was if memory serves it was a coil magnet arrangement.
also has anyone else here ever checked out Jose Pino's making a speaker out of a styrofoam plate

i really gotta learn cut/paste kung fu!
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Founder of XSA-Labs
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Wall hanging foam core transmission line

I have started my stereo transmission line hanging picture speaker project. This was inspired by a design from: VIFAntastisch ! Der Wandlautsprecher, Projekte der Nutzer / Eigenentwicklungen - HIFI-FORUM which is for a single speaker and is made of particle board and pine strips. I decided to make it out of 20 in x 30 sheets of foam core board. The pathlength had to be reduced from 1.2 m to 1.0 m to allow me to fit two speakers side-by-side on a single foam core board. This tuning is for about 87 Hz. Now I await the Vifa TC9D speakers to arrive and finish assembly.


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For laminates the core isn't really the issue. Layered cardboard
varnished with polyurethane is very strong and light, and some
cheap furniture (storage boxes mainly) is made this way.

For paper foam board I'd suggest a varnish layer on the outside and
when its very near dry adding a layer of heavy duty aluminium foil.

Or varnish and let it dry, then add the foil with contact adhesive.

rgds, sreten.
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Has anyone considered or tried using a 'smart' material like a non-newtonian liquid (cornstarch and water) as damping material in speakers? It responds by stiffening up like a hard solid when subjected to rapid time-varying shear stress. Silly putty (or Dow Corning 3179 dilitant compound) is a nice silicone based version of this type of material. It can be made to solid-like properties by combining with polyurethane foam so that it doesn't flow like a liquid under gravity, a commercially made material called D3O uses 3179 as the core ingredient in armor pads for crash protection. A laminate of thinner MDF or aluminum and D3O would be an interesting cabinet material. It would preferentially absorb higher frequencies and can be tuned by varying composition. A simple DIY test with silly putty would be interesting though.
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Wall hanging stereo TL's finished

I finally installed the VifaTC9FD's into the wall hanging 'picture' speakers. I hooked it up to the Lepai amp and iPod and tested with a variety of tracks. They sound fantastic, I mean really good. The bass is really nice, and the mids and highs have really good detail. The biggest surprise was the imaging given that they are mounted only about 2 feet apart in the same box as a stereo set. It is my first full range point source speaker and I just can't get over how good a pair of tiny 3.5 inch $12 dollar speakers and a box made of foam core paper and old pillow stuffing can sound. I am a true believer in full range drivers and TL's now. I am hearing details and sounds that I never knew were there before. The Vifa drivers are super in case anyone else hasn't heard them. Here is a photo of the new speaker propped onto some stools for testing. I need to have them decorated and put a picture frame wire for hanging on the back.


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Founder of XSA-Labs
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Back loaded horn bookshelf speaker

My next project for the Vifa TC9FD is a back loaded horn. This design is tuned for about 70 Hz based on a 48 in path length. I am using the plumbers putty in a sandwich between foam core for the front baffle to reduce any high frequencies that may re-radiate from the front. The enclosure is 5 in wide by 10 in deep by 15 in tall, as usual, the size is chosen to maximize cuts based on 20 x30 foam core stock. I am lightly stuffing some bends to clean out the highs from leaking thru. The driver chamber is heavily stuffed and has a throat area equal to the driver piston area, the expansion is modest, only about 5.7 to 1 but that is all the room I had in a bookshelf design. I pre installed some lamp cord straight thru - no binding posts for these cheapy projects.


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