hardwood for stereo speakers

[greenie512]

Can’t resist this, basically I would agree with Soundman. Remember hardwood is exactly that – hard – hit it with a hammer and it’ll resonate at a certain frequency. So along with stability issues you will find a hardwood cabinet will “add” its own overall sound/characteristic to such a system.

Now I recently read somewhere (dam sort term memory) that from the overall sound of a system 20% can be generated by cabinet resonance – now that seems a large number to me, so I’m not prepared to argue about that but I can imagine that a poorly built cabinet of the wrong material could add (and degrade) the overall sound of the system.

As suggested built boxes of good quality ply or mdf and mount your hardwood on the surface by one method or another to allow h/w to expand/contract naturally.

[stolar]

snip, snip ...

I have never seen a respected commercialy produced studio monitor with sand in it or cement blocks or cement sheet or any of the dosens of crackkpot things that " enthusiasts" enjoy fiddling with.

keep it real fellas.
cheers

Could not agree more with you that the most important factor is quality of workmanship and choice of appropriate materials. Nothing can make up for failure in either of the two.

I also absolutelly agree that one shoudl keep it sensible but disagree with the implication that the esoteric designs are bad because they are not comercially available or do not appear in profesional use. Comercial and in particular profesional designs are constrained by cost and manufacturing process and are mostly produced to "good enough for the target market" level of audio quality. Comercial designs deneraly do not produce audibly better results then esoteric designs. Profesional equipment generaly, as a rule of thumb, produce audilby inferior results to the equaly priced audiofile equipment. On the other hand profesional equipment will withstand rigors of constant use without failing.

Admitedly not all ezoteric designs will produce audibly better results, particularly if they rely on design and neglect the first two factors (workmanship and material).
Most ezoteric designs are only an attempt to improve (in a small increment i might add) on the already well known and accepted principles of speaker box building and as such are not bad in priciple. Some are misguided and some are waste of effort. Some will produce audibly better results and some will not.

One thing to keep in mind also is that most traditional studio monitors were designed as "near field" monitors which does not make them ideal choice for decent size living room.

The beauty of a "home baked" speaker system is that that you can encompass all the known and accepted principles of good box design without care about being sensible or comercially viable.

[Harry72]

"Admitedly not all ezoteric designs will produce audibly better results, particularly if they rely on design and neglect the first two factors (workmanship and material).
Most ezoteric designs are only an attempt to improve (in a small increment i might add) on the already well known and accepted principles of speaker box building and as such are not bad in priciple. Some are misguided and some are waste of effort. Some will produce audibly better results and some will not."

True words... like most things, once you get to a certain point an extra 1000% effort may only get you a .1% increase.

IMHO I get annoyed with a lot of the misinformation audiophile crap on the internut its pedantic procrastinating BS, a newbie gets so confused by this they just give up because these people make it sound all so hard to do.

Its not hard to make a accurate solid box with some sensible bracing, any more than that your gaining very little... you only got to move that speaker 2cm in its room postition and the sound can vary wildly more than that extra 1000% of effort!

Its easy to start with a sensible design using reasonable quality speakers and xovers, there are some very good designs to be had for free if you look, us being WW'ers a set of speakers are a very good project... we'd probably be able to make and dress the boxes better than 99% of these pedantic procrastinating BS'ers.

[soundman]

I do not wish to infer that esoteric design is not a valid or worthy persuit.
However the word of HIFI is to a large portion populated by types who look to strange and esoteric reasons and solutions first rather than dealing with the simple basics first.

I disagree that traditional studio monitors are designed for near field unless you also consider a large lounge room near field also.

Traditionaly monitors were placed at least 2 to 3 metres away from the operators position... hell 15 years ago a decent recording console was 5 feet from armrest to connector panel and 9 feet wide at least.... in recent times however controll rooms have become a lot smaller and yess many monitors are now designed as near field.

If 20% of your speakers sound is from panel resonance, the materials and construction methods must be pretty damn poor.


Norply gone... bugger, they made some nice stuff. their Structrual CD was close to being BC and had very few voids. Certaily good enough for rock & roll.

I've been reading, building speakers since I was a lad & have seen quite a bit of absolute rubbish touted in the name of better results.

There are a few out there who achieve very good results ( and usualy without foolishness) and have truly got good ears, the inteligence and knoweledge to know what they are doing.
But there are plenty out there who like to spiel on and fiddle about.... frankly lots of them simply don't understand basic physics and don't understand the difference between "different and better".

All you have to do is look at the long string of HIFI con's perpitrated over the years from directional copper cables, coloured markers for CD's and the latest "high end digital interconects for better clarity and warmth:confused: "

Soundman's HIFI reality check.
If you

Selected your speaker components carefully from a good manufacturer with reference to each other and your aims.

Used appropriate maths & physics, either manualy or from a computer sim to design your cabinet amd you understood the process. or you used a proven design.

Built your cabinet from appropriate materials, using good structrual methods.

Used adequiate and properly designed crossovers and good quality wiring.

Placed and supported your speakers properly in a good room

and

Connected your speakers to " decent" equipment using respectable cables of reasonable length.

Then you should start looking at "other things" to improve the situation.
Even then you should be looking for simple reasons why you aren't happy with the performance.

Sorry getting a bit religeous & carried away.

cheers

[TassieKiwi]

Wo needs nancy-boy birch? This is plywood:

http://www.zeta.org.au/~kardon/Bridgewood.html

Resonate that! With 155mm H/W ply, you'll need good castors!

[soundman]

I have actualy seen bridgewood.... seriously beefy stuff..... but it might have a few voids in it

A box made of 25mm ply or 32mm mdf dosn't have much resonance...... but that is getting borderline silly.

In the proportions of the domestic speaker now in vogue 18mm properly braced is pretty damn good.

cheers

[Harry72]

Depends, if its a powerful sub you need thickness.
My sub is 36mm(18x2)thick and weighs a ton as its a 100ltr enclosure, still after 12mths since I last shifted it, its moved nearly 50mm from vibration!

[soundman]

I have built quite a number of twin 15" 600 watt rms sub cabinets out of 15mm ply sleectivly braced. We have frequently stacked them 4 in a block and mid high boxes on top. They have a 3db down point at about 35Hz.
I can lift one on my own (just) very little vibration can be felt on the outside of the box running at full tilt and they don't seem to wander about.

For any speaker box rigidity is more important than weight.

cheers

[woodbe]

For any speaker box rigidity is more important than weight.
cheers

Except... in the case of a down-firing subwoofer

My Brother has one of these, and on a polished floor, it needs to be anchored in heavy bass or it walks across the floor, and it's no lightweight.

[soundman]

Except... in the case of a down-firing subwoofer

My Brother has one of these, and on a polished floor, it needs to be anchored in heavy bass or it walks across the floor, and it's no lightweight.

Exactly how much air mass do you think you are mooving?

I would be looking for other reasons why the "vibration" is causing the box to move.

My expectation is that the box itself is insufficiently rigid and/or mechanicaly damped.... thus it vibrates.....thus it walks.

If the box is sufficiently rigid and mechanicaly damped the only vibrations will be sound comming out of the speaker cone or the ports.

Unless the mooving mass of the speaker cone is "significant" in comparison to the box mass and it is a very high compliance design.

Yep I have seen speakers walk (and big ones) and in most cases simply placing a hand on the box will show that the box is vibrating.

If you are looking to weight and or thickness of material to solve the problem alone, lots of weight and thickness is required to achieve significant results.
Judicious bracing and non resonant, mechanicaly damped design will get significantly better results.

examples of techinques to minimise panle resonance and vibration.

avoid square or symetrical structures.
brace any flat open areas of panel.
when placing braces try to avoid making geometricaly regular shapes when dividing the panel with the brace.
the front bafle is very weak, you've probably chopped more than half of it away cutting speaker holes, brace between speaker cut outs to restore strength.
bracing diagonaly can be very good it tends to make less regular shapes.
boxes that aren't cuboid tend to have less panel resonance problems but stay away from realy obtuse shapes they can do weird things too
Tension or compression braces that run front to back, top to bottom or side to side have value but tying oposite sides of boxes together does not help with panel rigidity they only resist the ballooning effect.

With a typical twin 15" box ( arround 600 x 700 x 900 typical)
I would fit a 100mm brace (edge on ply 20mm thick) across the baffle between the drivers to restore baffle strength, slightly diagonal if I could.

I would place one or two similar braces across the back panel avoiding the 1/2, 1/4 or 1/3 points.

Then two similar diagonal braces on the sides opposite diagonals on oposite sides.

because the top and bottom are usualy shorter boards and in pro audio they will usualy be sitting on the ground with anoter box on top. I dont usulay brace top & bottom.
but a brace here would be good too.
If I was to get keen I woud tie some of the braces across to the other side. But I usulay wouldn't because you have other work to do in there & too much going on in there is a pain.

Using these methods I can achieve better panel stifness from 15mm ply than would be achieved with unbraced 20mm, I would argue better than unbraced 25mm on a big box.
Believe me that weight and cost saving is important when its your back and your wallet.

the same principles can be scaled for smaller drivers and boxes.

Very commonly neglected is bracing the baffle where the strength has been greatly reduced by cutting the speaker holes.
I Have seen very few speakers apart from my own with braced baffles.

It has been my observation that as boxes move from 4", 6" 8" sort of sizes up to the 12", 15" 18" sort of area, the structural strength and rigidity of ply becames more attractive that the deadness and weight of MDF.

I would have no problems with a small box for a 6" driver say 8 to 12 litres made out of 18mm MDF being unbraced but geting up into 80 to 120 litre boxes the panels will realy start to be flexible unless you are working in 32mm.
get up in the 200 litre area I don;t care what you are working in you need bracing.

cheers

[Harry72]

Yes thats why mines 36mm thick and radially X braced, the reason it moves has nothing to do with the box "vibrating"... its the floor boards underneath it the whole floor is resonating, I cant turn the level up much as it bumps/resonates the DVD disc... and the windows of the neighbors across the road!
Not bad for a single 12" driver(adire shivaIII)and only 350wrms, its a HT sub so its tuned to 20hz for LFE its not much good for traditional music styles but ok for bass heavy stuff like MuDvAyNe or that teckno stuff.

[soundman]

Well harry, theres your problem right there......... you need to fix your floor .

In sufficient rigidity and mechanical damping in your floor.


cheers

[normanjr]

I've built a number of cabinets out of timber and mdf and found mdf produced better results for all the reasons identified above.

I dont think you really need the whole vacuum kit to do the veneering, you can achieve very good results with just a sturdy roller and patience.

Precise construction and correctly sizing the enclosure for the driver/s are important. Spending time planning the design and construction of your enclosure will pay off later on when it comes to listening, but I think you'll find after successfully building your first set of speakers, you'll be looking for excuses to build more! I'm already up to my 5th subwoofer iteration, and have far too many idle speakers around...good luck!

[woodbe]

Exactly how much air mass do you think you are mooving?

I would be looking for other reasons why the "vibration" is causing the box to move.

This was a big name big-ass sub. 15" driver. Dead to touch. It's always been a problem child, rattles even on concrete. I think the boffins in the backroom out did themselves

[Petebass]

Except... in the case of a down-firing subwoofer

My Brother has one of these, and on a polished floor, it needs to be anchored in heavy bass or it walks across the floor, and it's no lightweight.

lol... soundman is right, that thing is vibrating. That's a massive loss of acoustic power.........

Trouble is, you'd be amazed at how many commercially made pro-sound cabs can be made to walk across the room. Most commercial cabs aren't braced. The theory is that it's cheaper to make cabs unbraced, and to compensate for any loss of rigidity they just make the ply thicker. That's why a lot of pro sound cabs are made from ply that's an inch or more thick. I've made cabs out of 12mm ply and went to the trouble if bracing it properly. The result is a lightweight cab that can't be made to walk across the room. No vibrations. Properly braced, ply can work brilliantly. And as point out by Harry, any losses in the compromise are easily accounted for with a comon sense approach to speaker placement.

Speaker design is full of compromises. In pro,sound, you're constantly juggling with the Rigid Vs portability equation. Let's face it, the ultimate speaker enclosure would be concrete. That's completely impractical, especially for pro sound cabs get picked up and moved several times a week. That's why most pro sound cabs are Ply and home Hi-Fi is often MDF.