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What should speakers be built of ?

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Srinath_seshadri

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I have owned and played with several 100 makes and models of speakers. So I thought I'd post about my favorite materials to build speakers out of as well as what I found opening up 1000's of speakers.

1. MDF - AKA particle board. This is nearly what 90% of speakers are made out of. This is a manufacturers dream. MDF is cheap, dimensionally stable machinable, void free, sonically dead and easy to fasten with glue. Its also f-uglllly - and they slap wood grained vinyl over it. Which oddly looks - well fake. For the customer though, its alright, its got toxic glue in the material, but usually you only touch that vinyl covering, and it works fine. Just dont even mention water near the thing. And its not really very strong. But no one expects their speakers to carry some load, like my coffee table sub woofer idea. 95+% of home speakers are made from MDF. Now in the US, at retail prices, MDF is almost as the same price as finished Ply wood. Plus it needs a vinyl cover over it. So its more $$ effectively.

2. Plywood. First there was "Void free plywood". Cos air pockets have a ringing when you hit em with their resonance freq, and if there is multiple voids you get many freq's they ring in. The material is sonically almost dead. It is far stronger than MDF, resists water a lot better, can be stained and sealed and looks pretty good. It however needs to be screwed together, not glued, and its not as perfectly machinable. It has a grain. However 99% of commercial gear is made with plywood. Further, most of the "Big" home speakers from nearly all manufacturers are made of plywood. Altec, Klipsch, EV and every other manufacturer use plywood. And here is the kicker. Not all of it is void free. Its finished plywood, not void free plywood. How do they keep it from ringing. Easy. They are stuffed to the gills with fiberglass, foam or carpet or something, so the sound almost never hits the void to allow it to ring. Excellent material. Works great for big speakers, and I actually loosely define big as anything with a 10" woofer or bigger. LOL, EV's and altec's have that same definition.

3. Wood. Its far more expensive @ retail level, but you can go to a wood mill and buy quantity for close to the same price as plywood. But it is far better and combines the advantages of MDF and plywood and none of the disadvantages. Beautiful looks to boot. If someone showed up with blank check for me to build speakers - I'll be on my way to the wood mill before they left my house. Its a dream material, but your $$ may be the limit.

4. Metal. I have plenty of book shelves. Bang and olufsen, optimus, RCA all of these made speakers out of aluminum. Realistic minimus was made from steel. Great material.

5. Plastic. Not bad, sonically dead, and cheap. Looks like - well plastic, but it does work alright. I guess its water proof. I have an infinity center made of plastic. Pretty decent.

6. Masonite. Yea, its heavy, dimensionally stable, sonically dead. But also $$$ and hard to work with. I have seen a Jamo set made from this.

So that's what I have noticed. Feel free to add to this or to correct me.

Cool.
Srinath.
 

Shivam

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I have once heard speaker made of cement in an old house in Delhi. The owner had built it based on a design by G.A Briggs (of Wharfedale fame) and was actually a part of the room itself. It was a single speaker system (mono) and sounded really good to me.

All the speakers I have made have been with MDF or Marine Plywood. Never tried wood or other materials. Someday I hope to try concrete/cement based speakers too.
 
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Srinath_seshadri

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Actually that masonite - think of it as sheets of concrete. Not quite - but close. There was a guy on diyaudio that made a speaker out of granite.

Bose 901 series 6's are injection moulded plastic. All the wood on them is only for decoration, thay can be removed and it works the same way.

Cool.
Srinath.
 

jls001

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Add carbon fiber to the list. Very involved building process, though, and definitely out of the reach of DIY Joe:)

One could also possibly add CLD-ed composite panels to the list.
 

Srinath_seshadri

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Ha ha, yes. very cool.

Fiber glass has been used, but usually its a coating on plywood. They take the just the poly vinyl alcohol and spray or paint it on the outside and inside it they put some fiber and the alcohol and make a rough surface. I never heard it though.
For me you can stain and seal plywood with lacquer, and that is beautiful. Why you would put fiberglass on that is beyond me.

Cool.
Srinath.
 

Srinath_seshadri

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here you go after alot of analysis the best material for Mid bass and Highs = MDF, For subwoofers Plywood. Plywoods are not seen in subs these days is for mass manufacture its very expensive and long process. Very highend subwoofers use acoustically dead material use Sandwiches of several PLYwood combinations such subs weigh a ton but sound fantastic and yet very expensive. Example: Wilson audio subwoofers

I am planning to build myself a B&W 802 copy. I have the 12" bass bins that I got EV TRX's in. The 12" I am pulling out of my onkyo E53 is going in that.

I actually like a metal cabinet for mids. There is an RCA Linaeum speaker cabinet pair I have, 1 bad woofer in that set and I pulled it apart and sold the rest. The mids are going in that, though I have to make a wood face for it. Its a soft dome mid.

The Tweeter which is a hard dome I am mounting on top in a bullet I will machine up out of wood.

Cool.
Srinath.
 

captrajesh

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AFAIK MDF is different from particle board. While the manufacturing process could be the same, MDF consists of much finer particles than the particle board and thus much more denser than the latter.

As for wood, unless treated heavily, wood has a tendency to warp due to absorption of moisture from the humid air.
 
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Srinath_seshadri

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Yes true ,and I hate both of those LOL, and back in the 70's they had a HDF. My goodmans were made from HDF. What was the difference ??? No clue, I hate it too.

Wood - when you buy from a saw mill, you get furniture grade kiln dried wood.

If you buy from Home depot/Lowes, they sell wood that is far too wet. I know of people who used the thing to build their roof, and because it had weight on it when it was wet, as it dried it bowed. Cost 1000's to repair it. For outdoor use it needs to be under 15% moisture. For indoor use I believe it should be under 8-9%. Anyway, if you ask the saw mill guys they would get you the right wood.

@ Captrajesh - I love your avatar. Twist on DSOTM ??

Cool.
Srinath.
 

captrajesh

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back in the 70's they had a HDF.
They still have it. My carpenter is using it to make boxes for the GR Research 5.1 kit. He says it is similar to MDF but I think it would be denser; well logically speaking.
if you ask the saw mill guys they would get you the right wood.
Yes I know but I've seen many instances where doors made of teak wood getting warped.
@ Captrajesh - I love your avatar. Twist on DSOTM ??

Yes; it's my all time fav Rock band. :)
 

Srinath_seshadri

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Teak wood warped ? Maybe, actually in the US they use Teak wood almost exclusively for furniture in boats. These things are all curved, nothing is straight and square on a boat. Is that a reason for using teak ? Weird thing, tons and tons of Oak in the US, almost the same characterstics as teak. But they dont use it for boats. They import teak form asia.

You try ply wood ? Plywood should be atleast 3/4" thick Preferably 1" (25 mm) is better.

I have to think you can get better than MDF or HDF Or, just frame up steel with angle section, and bolt the wood to it. Any part that warps replace that section once you see that it cant be sealed with glue.

That's the srinath way. LOL. I cant make stuff out of wood.
BTW in that humidity does MDF get water and swell ? In the US houses are dry as a bone, barely 30-40% humidity in houses.

Cool.
Srinath.
 

yogibear

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So whats the conclusion?

30 years back I started using sheesham for many speakers including the pentagonal one. This is the densest available today but am not able to find the right widths, today.

Have been using MDF since last few years after I again got into building. I have come across two varieties of MDF here, the commercial which is kind light pink in color and the "green lam" brand which is light yellow and looks much better quality and is denser.

Altecs were made around particle board as I saw them on net. Guys around here use marine grade 25mm plywood for Altecs.

Would it be a good idea to use the 25mm green lam MDF and line the insides with say 6-8mm particle board? And then line it up from inside with 6mm felt, for damping?
Stuffing or no stuffing will depend on cabinet design, acoustics etc.
 

Srinath_seshadri

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Yea I better get some pics of my VOTT's, I may be trading them away this week.
The VOTT cabs are 1" 8 ply plywood and insides lined with fiberglass insulation. Better not handle it too much, or they will start itching.
The bigger the speaker the more it is likely to be plywood. Altec's used plywood for anything that had a 15, or was for commercial use.
You dont quite need the heaviest wood, but any available wood that wont crack easy, or is too wet will be my choice. Marine grade plywood works too.
Stuffing - Available cheap and easy in large quantity for me (as in tear up a old cheap mattress or something) - low density foam. Someone I know used shredded paper and stapled them onto the walls with a cloth holding it in place.
Cool.
Srinath.
 

navin advani

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I believe in layers of materials having differing densities. I tried making cabinets ultra light using materials like resin bonded fiberglass and woven carbon fibre and found that these materials though stiff also resonate.

Hence any material or mix of materials should be ideally light (so that it does not store energy), non-resonant (so it does not add to the sound) and hardy (plastics and be both light and non-resonant but are not hardy enough, besides for DIY plastics are difficult to work with).

MDF/Marine grade Ply etc. are easiest for DIYers to work with. MDF is good for straight boxes, ply allows for some bending. Solid wood is also an attractive option - see Daedalus Audio.

Fiberglass can also be used for DIY and it has a lovely stiffness to weight ratio and using resin bonded rovings one can control stiffness in areas that need it most but it is also resonant.

Carbon fibre has a look some people like. On a stiffness to weight ratio, it is not a VFM option. So unless you have very deep pockets or want to look of carbon fibre I would avoid using it.

My last pair (about 2 years ago) was made of 3 layers of marine grade ply wood. Sandwiched inside these 3 layers was a layer of lead sheet and a layer of resin bonded fiberglass. Pictures 5 and 6 on post 1 on the link below show a cross-section of this construction. I posted this 2 years ago but have adding a link here for easy reference.
Pictures of Selah designed Tempesta Extreme and RC4 (no subwoofer)

In my past I have used concrete and it is very messy to work with. There is no room for error and when you try to route it for the frame of the woofer it can crack and requires rework. You need a mesh of wire (say 4" x 4" 10GA) as a frame for the cement-concrete to adhere to. There used to be a Swedish company called Rauna that made speakers this way. Google it.

Metals - MS, SS and AL can also be used. JBL's Control 1 are built from metal. Metals require damping usually speciality rubbers and like plastics are best for large volume production. Again I have tried this (using an AL alloy) and found for the DIYer one had to resort to rubbers having different shore hardness. My experiments led me to using 2 layers of 3mm AL alloy with rubber of shore hardness of 60 between them and a softer (shore hardness 40) on the inside of the cabinet. On this inner rubber layer I had to use open cell foam to control resonances. On the outside I sprayed a plastic (PVC) coat.

Glass and stone tiles. Again the challenge is containing and controlling resonances. One option is to stick these tiles on wood on the inside of cabinet. If you visit the DIY forums you will see many loudspeakers with this option. Waterfall, I believe, uses a tempered glass that has reduced resonances.

Hope this help.
 

shafic

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What about 'tar' aka 'dambar' ( between the layers).

I recently got multicell "stephens" truesonic horns. They are 'tar' filled ones and there is absolutely no ring or resonance.

regds,
shafic
 

yogibear

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OK, which is the better of the two options:

25mm MDF or 25mm Ply?

Other things (except wood) are beyond my talents.
 

yogibear

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Navin,

Going by your builds, you do look like a guy with loads of talents and experience and equipments as well. Did you ever try TL's?

Could you help me with the design, layouts, and your comments?

Thanks.
 

Srinath_seshadri

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What about 'tar' aka 'dambar' ( between the layers).

I recently got multicell "stephens" truesonic horns. They are 'tar' filled ones and there is absolutely no ring or resonance.

regds,
shafic

People actually put tar or plumbers putty on the 511 and 811 horns to keep them from ringing as well.
Cool.
Srinath.
 

shafic

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Excuse me for going out of topic.

If any one remembers about India's best vintage speakers 'ARPHI' ( I previously owned their 'Aquarius'), I have heard that they had used 'DAMBAR' on their speaker cones. I think the 'GOOP' used in ALTEC cone surrounds is also like that materiel.

I have a pair of PHILIPS 12' Alnico FR speakers. One of the speakers surround has that 'tar' like 'goop'. This one is giving more 'bass' than its 'goop' less partner.
 
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Rajiv

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Hi,

Sorry for the OT.

I recently got multicell "stephens" truesonic horns. They are 'tar' filled ones and there is absolutely no ring or resonance.

You are 100% sure that the horns are "stephens""trusonic"?

Pictures please.

Regards
Rajiv
 

shafic

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Pictures please.

Hi,

Will post pics soon. Now in 'attic'.

What about my 'Goodmans' 'dew' Alnico FR speakers? You had asked for pics, then did not give your view.Maybe you were busy. I am still waiting.

regds,
shafic
 
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