What are the characteristics of a better material for enclosure?

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Maybe you could point it out one more time, but still no one will care.

No one will ever build a speaker cab out of steel, so it's kind of dumb to keep writing about it. Just because it's the stiffest, doesn't mean it's the best. What would steel do the speaker magnets, and inductors, if mounted internally?

Tom E
 
Actually, I've built a number of them for the reasons RCW noted and also periodically make the same points to mostly 'deaf ears'........ I did 'cheat' a bit though, using pre-fabbed electrical motor controller boxes.

The steel has no measurable effect on the driver or any other electrical components, though of course you can't be completely clueless about magnetic fields. BTW, make it from cold rolled steel (CRS) and the cab is a very effective magnetic shield.

That said, like with any app you ideally want to use the right 'tool' for the 'job', so choose the material best suited for the speaker's intended BW and system Q. My default recommendation is 11-13 lam, void free plywood as the best compromise between rigidity/damping since it's near ideal for most speaker apps, but for some such as a mids and/or HF only cab or an otherwise high Q system, a low Fs material such as MDF, flakeboard or an even higher damped material may be required.

GM
 
I have contacted a few specialty lumber and exotic wood suppliers all dealing in premium grades of Baltic Birch. I have asked for certified 100% void free plywood. The answer is always the same, there are no Russian mills certfying 100% void free ply.

I have been told that the only ply certified to be 100% void free is Marine ply or possibly arcraft ply (typically Finnish). 3/4" Marine ply is damned expensive.

Do these claims make sense to anyone using Baltic Birch, I know that you would actually have to cut through a void short of x-raying the panels to detect the voids.

Anthony
 
Of course they won't guarantee void free due to the economics of manufacture, unless you pay for it!

I've got through a good few sheets of finnish and russian birch ply, but not marine or aircraft certified, and never found anything significant in the way of manufacturing defects.

I think this is close to a non-issue if you buy sensibly.
 
Hi

I'm also interested in using steel ,the main reason is that I'm geared up to use it ,welders ,panbrakes etc .For me to make cabs out of marine ply or container ply which is void free standard thickness 28mm thin laminates I would need to by new workshop tools .
So to use steel would it come down to just building the cabs and trying different dampering materials ,copper cabs could look at treat .
This is a picture of container ply its 28mm thick with 19plys and void free the adhesive is the same used in marine .
An externally hosted image should be here but it was not working when we last tested it.

Cheers
 
Forming and cutting 3 gauge plate is somewhat beyond the average sheet metal shop gear so I would probably go the gas axe boiler plate route myself.
People who have worked with steel know that it is a wonderfully forgiving material and fat filler welding rods can hide a multitude of sins and still give the type of structural integrity virtually impossible to obtain with wooden construction.
Bracing with quarter by one strip gives the stiffening equivalent to a epoxy glued 2x4 and quarter plate is the equivalent of 32mm. mdf.
rcw.
 
Sandwich

Glad to see this thread is still very much alive :D
Seems there a lot of feelings involved too .... maybe a bit too much ;)

Anyway. Have been thinking about the mass issue. Why is it inherently bad as I have read in some of the last posts.

We want the membrane to move not the cabinet. Therefore the more stable a base for the moving of the membrane the better.
Stone or ceramics, I still think would make a pretty good cabinet, though not that easy to build. It ill have a high resonance freq and a high Q .... maybe to high Q and not so much damping!

Another way would be a sandwich construction. It could be made very stiff and very light, like two layers of ply or glassfiber, with a polystyrene core. If you wanted a better possibility to shape the cabinet form, you could build it of two layers af glassfiber with some space between (inner and outer wall) and fill it with expanding PU foam. ...... can't be much energy stored there.

/Baldin
 
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Re: Sandwich

Baldin said:
It ill have a high resonance freq and a high Q .... maybe to high Q and not so much damping!

If you look at that from the POV of the resonance actually getting excited high Q can be a good thing if it is at high frequency. As frequency increases the available energy to excite a resonance decrease. A high Q resonance will need a lot of sustained energy in a narrow bandwidth. Not likely to happen with music so in effect there is no resonance.

dave
 
An externally hosted image should be here but it was not working when we last tested it.

townshend audio Glastonbury V

Speaker cabinets should not be flimsy; therefore we make ours from extremely stiff gypsum artificial stone in a welded steel shell. The cabinet exhibits extremely low resonance due to it's very high stiffness, weight and rigidity, whilst the sound radiating cones and ribbons are extremely low mass (extremely light). This means that of the two elements of a speaker; the moving parts are very light and the reacting part, the cabinet, is very heavy.

Regards
James
 
planet10 said:


Do you know where that ply comes from? Why i ask is because i'm surrounded by douglas fir (a pine terr BTW). The douglas fir ply around here is 5 ply for 3/4" -- not that great for speakers.

dave


Really thank you for the response, Dave.

It is real solid douglas fir wood, not ply.
Around 20mm thick, enough dry and with straight, thin "lines", without "knobs". ( i dont know the right word... ':xeye:')
 
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chriselm said:
It is real solid douglas fir wood, not ply.
Around 20mm thick, enough dry and with straight, thin "lines", without "knobs". ( i dont know the right word... ':xeye:')

Without knots. One of our friends up island builds boxes out of solid doug fir. He is using recycle from a railway restle that was made 100 years ago. Even thou he is using really stable wood, and really knows what he is doing, he has lost at least one box due to the material cracking.

Finished naturally it turns a lovely orange colour. It makes a very good sounding box, but not quite up to the BB boxes we build & veneer IMHO.

dave
 
planet10 said:


Without knots. One of our friends up island builds boxes out of solid doug fir. He is using recycle from a railway restle that was made 100 years ago. Even thou he is using really stable wood, and really knows what he is doing, he has lost at least one box due to the material cracking.

Finished naturally it turns a lovely orange colour. It makes a very good sounding box, but not quite up to the BB boxes we build & veneer IMHO.

dave

Hey Dave,

What thickness veneer do you laminate over the BB Ply?
If I can only get 3/4" BB Ply locally should I laminate it up with another thickness to increase stiffness?

Anthony
 
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Coulomb said:
What thickness veneer do you laminate over the BB Ply?
If I can only get 3/4" BB Ply locally should I laminate it up with another thickness to increase stiffness?

Veneer is thin, <mm.

We build most of our boxes out of 12 or 15 mm BB, occasionally using 18mm. Sometimes we will double things up, but often it is just to accomodate some cosmetic goal and not in particular to increase stiffness. What are you building?

dave
 
planet10 said:


Veneer is thin, <mm.

We build most of our boxes out of 12 or 15 mm BB, occasionally using 18mm. Sometimes we will double things up, but often it is just to accomodate some cosmetic goal and not in particular to increase stiffness. What are you building?

dave

I have two projects I am cultivating, a pair of line source speakers like the Alpha LS from GR Research or Beta LS from CSS.

A large set of home Theater speakers, Front,Center,Side,Rear, 7 in total 3 to 5 drivers per speaker.

Anthony
 
This is an interesting thread and having read most of the posts I would like to add a couple of thoughts. I think the issue is not so much that of what material but rather how should the enclosure be constructed.

My philosophy about speakers (and am not saying its right) is that we should not be hearing the box at all, it should add or subtract nothing ideally. For this reason I love OBs but I have also built several box speakers.

I know many people do liken the box to a musical instrument and I can well understand this view, but in my probably somewhat rigid view I want to listen to the actual instruments that were recorded not the box, so I will do anything I can to remove the box from the equation.

This includes driver basket damping, very thick baffles, multi layer construction, box within a box, covering the baffle with felt, bracing and more bracing, wrapping the sides with felt and cloth concrete capping and bass blocks and more. Basically as I say it is not so much the material as the method. In truth this is where DIY can probably easily exceed commercial because we don't need to be so worried about speed of manufacture, material costs, shipping weight etc, so why built a box that is just as compromised as your regular commercial offering but I digress...

My DIY home theatre speakers are built this way and to my mind and ears sound great with pretty much any sort of music. Mind you they are very heavy, the mains are at least 80kg each, probably more as they have to be moved by trolley by two people.

An interesting aspect is that a lot of folk feel that such a speaker will sound dead, but franklyI feel they don't, maybe speakers sound dead when the bloom of the box overcomes the upper mid or highs, I don't know but in the end a box that is as inert as possible sounds very good in my opinion.

An interesting little aside is that some friends recently borrowed my smaller rear speakers for a party, on the night I had at least 6 people come and tell me that they sounded amazingly clear and they were stunned at how much volume they put out and how impressive the bass was. Clearly something was right with them and I have since had request for me to built some for other people, which I said I couldn't but I will show them how and give them a hand.

So that's my contribution for what its worth, in the end use what you can afford/work/buy but pay attention to the actual design above all else, even cheap drivers can sound great in the right enclosure.
 
gold would not only look good, but also strike a nice balance between density and rigidity.
there is no 'best material'
lead would be nearly as good, or likely better, than gold. (more malleable/soft/dampening. sometimes drivers 'need' to be tamed, just like a room needs it)
on the other hand, super thin highly resonant material would give up free db, and the 'drum' type speaker would 'bounce' super nice, but then you listen more to the speaker and less to the recording, unless the builder knew how to tune a drum real good-like.
most recording engineers are bozos, and have no idea (just kidding-ish), about the ultimate presentation of their work. i think many landmark recordings are happy accidents.

i know when building walls, the best acoustic isolation occurs when air is used as a dampener. air pretty much takes the punch out of any percussive source. density is more of an issue than rigidity, to my brain. elasticity (rigidity) will allow a wave to retain it's energy, whereas, plasticity (dampening) allows for good energy absorption.

so, then, isn't the true 'battle' between the characteristic of the driver versus the box itself the determining factor which decides whether elasticity or plasticity is the desired effect?

like, i you have metal drivers, than a 'soft' box is better, but if you have fibre drivers, a stiff box is better?
 
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