Concrete speaker enclosure

[Eileen Dover]

Hello. I am planning to make some speakers out of 50 mm thick concrete paving slabs. Cutting the slabs to size is not a problem with a circular saw, diamond blade and guide. The bit that troubles me is doing the driver cut outs :scratch: . Any ideas of the best way to get nice clean circles cut out ?

Thanks.

[DiveDeepDog]

I made a slate plinth, used 2 tools. Drilled holes through, then joined the dots up with jig saw. Finished off with angle grinder.

Not pretty and I'd recommend an air fed mask.
Think I'd be getting water jet quotes, and/or looking at casting with the holes already formed.

Good luck.

[joolz]

..what Mark said - use some small re-bar to reinforce and make moulds the correct size for the drivers you intend to use.
Maybe stainless steel re-bar ? or something non magnetic..

[Eileen Dover]

Thanks for the replies. I did not want to really go to the hassle of casting my own baffle but maybe i will give it a go :) It gets tricky with driver rebates as well. It's just that i have a number of slabs available for free and would have preferred to use them if possible.

As the baffle is subject to the most vibration it seems a daft idea to make the baffle out of wood and the rest out of concrete. :doh: The other option is to cut out the hole with drill etc and then stick on a thin layer of wood on the outside so no rebates required :scratch: Cabinet dimensions are getting even bigger then.

[Cycleallday]

A water jet cnc will do the job and many small engineering firms have them. It would probably entail a 2 hour charge which in the south would be £50 an hour but much less up north.

Mel

[Pharos]

I agree with Mark, and also your point about an extra layer of wood to prevent rebating needs.

If you cast I recommend that you include a large amount of PVA in the cement, not only does it increase strength which will be good around the holes,, but it will lower the Q.

[smangus]

Wow , this sounds pretty hardcore :ner:

/coat :D

[ReggieB]

Find a local company that makes stone kitchen tops. They'll often cut stone to order - and if they can cut a hole for a sink - they should be able to cut the sort of hole you're after.

Not Hi-Fi, but a local company sold me a bit of marble offcut - and cut it to a template I gave them. It now nicely fills the gap between the end of my bath and the wall.

[Qwin]

I cast some concrete speakers about 30 years ago with 2 1/2" walls.
They were very very heavy.
They have been stolen 3 times over the years, twice from myself and once from a friend I gave them to. They were recovered a few yards from the property each time, the thieves gave up, yes they were THAT heavy.

I didn't pick up on the size of your cabinets, but weight will be a problem if they are even large stand mount size.
I saw an interesting video on casting some small bookshelf speakers in concrete, the guy used a polystyrene inner core for the volume of the cabinet and after they were cast he melted the Polystyrene out with cellulose thinners, worked well.
Casting might be easier than cutting concrete.

There is always light weight concrete made with Pumice stone as the aggregate, bags of Pumice are available on the internet in various pebble size, I've considered this myself, but it's a major undertaking tackling a project like that.

[Eileen Dover]

Thanks for the reply Ken.

Very useful information. Yes the one good thing about having heavy speakers is that thieves will think twice about taking them or give up like they did with yours. 2 1/2 inch thickness - i am not surprised they weighed a ton. Was that the optimum for your size of speaker ? Mine is going to be a 3 way floor stander with big woofers so quite substantial. Thickest i thought they would need to be was 2 inches.

I haven't got any further with it due to procrastination :rolleyes:

[ianlenco]

Hi Michael,
There is a guy not far from me who's been making concrete speakers using Jordan drivers for many years. It might be worth contacting him for advice/tips. I've met him once and he seems very approachable.

https://sites.google.com/site/matteisloudspeakers/

[Qwin]

Mine were Tannoy M20. A 2-way with an 8" bass. I built the cabinets with the original internal volume and grew externally.

[Pigmy Pony]

May or may not suit the size of hole you're after, but you can hire a core-drilling setup from a tool hire shop. The kind of thing you would use to make a hole in a wall for boiler flues, bog pipes etc :)

[struth]

I used to do diamond coring way back. Plenty water and preferably a rig etc needed for big holes

[Firebottle]

Hatton Garden anyone?

[JohnG]

The Link is to a material I was once keen to Laminate and trial on a OB Speaker.
The link covers a few versions of the material, I believe the material I become familiar with
is the Portland Version.
These materials cut with a Jigsaw with relative ease, as well as can be found in a thickness up to 12mm.
Two or Three sheets can be laminated, to make a Wall thickness of choice.
With a little though in the design of a cabinet, a conventional version of Speaker Enclosure Joinery can be mimiced.
My OB Baffle was going to have a Three Ply Lamination, with Ply Layer Two being different material, so possibly a CLD Type of configuration.
I till have 4 x 15 Bass Drive Units for the project, so maybe one day, I will get there.
My ESL 57's are yet to be championed, by a younger contender.


https://en.wikipedia.org/wiki/Cement_board

[Eileen Dover]

Thanks for the link to cement board. There are several different types it would seem. One is bendable :eyebrows: I wonder about their effectiveness when used for a speaker cabinet. Definitely easier to work with than concrete.

[M6NTL]

My Townshend Glastonburys are Plaster of Paris cabinets poured into a simple steel frame. Easy to work with, and no matter what volume I drive them at there is ZERO cabinet resonance...

Sent from my G8441 using Tapatalk

[JohnG]

The Fibre Cement Board is as easy to work with as any board material.
A cutting tool with carbide or diamond will be best.

If a cabinet is to be made, I would look into a resin like Akemi to check for its compatibility with the material.
If all is good, I have seen this used on massive pieces of granite, and the trust it receives defies belief.
A lamination of the material, with the inner layer produced slightly smaller than the outer,
with a little thought the panels could be arranged so that a crude version of a Cabinet Makers Rabbet Joint could be produced.
The two layers can be bonded with Akemi Stone Glue.
A 40mm X 40mm X 3mm Aluminium Angle used as a picture frame, attached to a few of the panels inner faces, the angle will be internally bonded with Akemi, this will give a framework to create a robust/ rigid enclosure with plenty of bonding surfaces.
As said the cement board is a discarded material in construction, so the base material can be found reasonably easy and free if a cheeky enquiry is made.
Akemi Akepox will set one back about £30.
My original idea for the material was to produce a OB with it, as a cabinet the material will need a little more thought on the achieving air tightness when assembling.

[hornucopia]

On mass in cabinets....
"The same issue of Haute Fidélité recounts how Bernard Salabert of PHY at the time had constructed a personal listening room of the large sort. In total, it employs 144 tons of material (16 tons of sand in the ceiling alone) to be acoustically inert. Yet when he experimented with his 8-inch driver in a 16-ton wall acting as open baffle, the floor vibrated. At regular playback levels. This hexed the notion that high mass was effective at damping. It confirmed the commitment to the deliberately resonant speaker cabinet that would neither deaden, dull, smear nor thicken the sound. "The signal, not the box" gets cornered by "Don't kill the music with the box". This resonated in me as a worthy story waiting to be plucked and told. Again. We're far too late to this party to be third. Even The Absolute Sound has been in on it five years ago when the Ocellia Tilia snagged a 2002 Golden Ear award from Robert E. Greene."
from a (6 Moons) review on my Ocellia Calliopes.

I had Glastonburys too; not only gypsum plaster but also a thick layer of carpet inside, I recall.
Was taken aback, visiting Max on Cyprus, when-unasked - he played Andreas Vollenweider as demo ...the very same as I was using for demo at the time!