Particle board cab vs solid and/or ply....your thioughts?

[Mike Sulzer]

For example, here is the spectrum of an open low E string, bridge pickup:
openLowEStringBRPup.pdf
All harmonics present and accounted for.

[eschertron]

Say you want to build light-weight, sturdy, un-colored cabinets (realizing there will be trade-offs).
Would it make sense to build a wooden frame with ABS skin and lined with sound-deadening material like the car stereo people use?

Amazon.com: GTMAT 100 sqft Automotive Sound Deadening 50mil PRO - Acoustic Dampening Installation Kit Includes: 100sqft 2 Rolls (18in X 33ft), Instruction Sheet, Application Roller, Degreaser, GT MAT Decals: Electronics

http://www.amazon.com/Noico-Self-adh.../dp/B00URUIKAK

What effect would this sound deadening treatment have on the overall loudness? I'm not sure what it does, is it a pliable reinforcement or an absorber? The former might be a low-weight alternative to the traditional cab fabrications, the latter might not be so appealing.

edit: and I have a sneaking suspicion its primary use is to keep sh*t from rattling.

[Enzo]

Mike-
Those E string harmonics go way up, but note the real high ones are 40db down, and wouldn;t be heard much at all. Also, the guitar, which I thought was the context, cares little for upper harmonics, otherwise we'd have tweeters.

Richard-
While I agree that it is a valid consideration what the new reproductions will sound like in 300 years, and your other associated points, I think the point of holding the Strad up for comparison is that in the top echelons of violinists, it is highly sought after, and if someone could make something that played the same, it would have a market. On the other hand, no one is clamoring for replicas of a $200 Conn student violin. When it comes to guitars, there is no consensus about just what the ideal one sounds like. I like my Gibson J50, while a friend swears by his Martin.

[rjb]

What effect would this sound deadening treatment have on the overall loudness? I'm not sure what it does, is it a pliable reinforcement or an absorber? The former might be a low-weight alternative to the traditional cab fabrications, the latter might not be so appealing.

I don't know. That's why I asked. I'm guessing they work like 3M vibration damping tape.
http://multimedia.3m.com/mws/media/1...ration-434.pdf

edit: and I have a sneaking suspicion its primary use is to keep sh*t from rattling.

And I was thinking that's a good thing.
In lieu of MDF or concrete walls, use lighter material and damp it so it doesn't vibrate.
What got me thinking along this line was Juan's statement:

Well, it actually works the opposite way : a cabinet wall resonance will make a dip at resonant frequency, not a peak as in an instrument, because it's a lossy "dissipative" load.

It will absorb energy from the speaker and turn it into heat, its own contribution as a piston moving air will be smaller than energy absorbed from the way more efficient speaker.

Maybe I should have asked this question instead:
How would you DIY a relatively "uncolored" PA cabinet that is sturdy enough to transport, yet light enough not to throw out your back or give you a hernia?

[Mike Sulzer]

Mike-
Those E string harmonics go way up, but note the real high ones are 40db down, and wouldn;t be heard much at all. Also, the guitar, which I thought was the context, cares little for upper harmonics, otherwise we'd have tweeters.

Richard-
While I agree that it is a valid consideration what the new reproductions will sound like in 300 years, and your other associated points, I think the point of holding the Strad up for comparison is that in the top echelons of violinists, it is highly sought after, and if someone could make something that played the same, it would have a market. On the other hand, no one is clamoring for replicas of a $200 Conn student violin. When it comes to guitars, there is no consensus about just what the ideal one sounds like. I like my Gibson J50, while a friend swears by his Martin.

Guitar speakers and human hearing, even in healthy young people, both fall fast above 5KHz, so right, the highest harmonics are not needed. In any case all higher harmonics die out very fast; they are the picking transient. So they start out a lot higher than indicated on that plot, which covers a couple of seconds.

[rjb]

Harmonics are far more important than the fundamental. For example, fundamentals on the lower notes of a bass can be completely inaudible, a result of the great difficulties in producing high levels of very low frequencies and the almost incredible lack of sensitivity of human hearing to low frequencies (except at near painful levels), but the note sounds at the proper frequency anyway.

I wish I could find my copy of Horns, Strings, and Harmony.
http://www.amazon.com/Horns-Strings-.../dp/0486273318
Anyways, I do recall Benade citing an early study in which subjects listened to recordings of string bass which had been processed to completely remove the fundamental. No one could tell any difference.

[rjb]

When it comes to guitars, there is no consensus about just what the ideal one sounds like.

That's easy. Martin OM-18.
EDIT:

PS - Round-shouldered, 24.75" scale J45s and J50s are nice - but the square-shouldered, 25.5" ones are just Martin dreadnought wannabes.

- SGM II

[Justin Thomas]

So make the cab out of thinner braced panels with a bracing pattern to emphasize the frequencies you want, and get a lighter cab as well.

Oh, you mean like a Strad or a Martin? Wowza, what a concept!

Justin

[rjb]

Oh, you mean like a Strad or a Martin? Wowza, what a concept!

Hmm, scalloped fan bracing or tone bars? Where should I put the sound post? This is getting surreal.

[Chuck H]

Oh, you mean like a Strad or a Martin? Wowza, what a concept!

Justin

Ah!!! But with either the Strad or Martin the vibration is additive, but with the guitar cab it's subtractive (for the most part). In that case you'd have to tune the cabinets resonance to that end. Intentionally subtracting frequencies. This with the added element of amplification at variable volume and distortion character. I, for one, am overwhelmed by the prospect. I've been lucky a few times building resonant cabinets. Unlucky on two occasions and (I suppose) neutral at other times. It's absolutely a crap shoot. On the other hand, I've never gotten unpredictable results with MDF (and never outstanding either).

[Gingertube]

I don't build many cabs.
The ones I do build are usually 2 x 12 Closed boxes (sometimes with just one speaker loaded and the 2nd hole left open)
I use 18mm MDF with dimensions following the HiFi Golden Ratio (That is 0.618x deep, x wide and 1.618x high), additional bracing across the middle, BUT always use 3/4" Marine Ply for the Baffle.

There is also an acoustic ratio which HiFi guys sometimes use in lieu of the golden ratio which is 0.7937x , x, 1.13x). I've never tried that for a Git Amp Speaker Box.

Yes the boxes are a bit heavy but I've been happy with the sound and longevity.

Cheers,
Ian

[Richard]

Mike-
Those E string harmonics go way up, but note the real high ones are 40db down, and wouldn;t be heard much at all. Also, the guitar, which I thought was the context, cares little for upper harmonics, otherwise we'd have tweeters.

Richard-
While I agree that it is a valid consideration what the new reproductions will sound like in 300 years, and your other associated points, I think the point of holding the Strad up for comparison is that in the top echelons of violinists, it is highly sought after, and if someone could make something that played the same, it would have a market. On the other hand, no one is clamoring for replicas of a $200 Conn student violin. When it comes to guitars, there is no consensus about just what the ideal one sounds like. I like my Gibson J50, while a friend swears by his Martin.

Actually I find it to be an interesting pursuit and Stadivarii are worthy subjects but as a guitar player I end up hearing so much BS about vintage this and that blah blah tonewood blah blah vintage capacitor I want to puke sometimes. Obviously a violin is totally different than a solidbody guitar. An electric guitar has more variables with cables speakers and such.

A couple of interesting links:
https://en.wikipedia.org/wiki/Stradi..._sound_quality

Can you pick the Stradivarius violin from sound alone?
https://www.youtube.com/watch?v=VlJ_DXneJ98

[J M Fahey]

Maybe I should have asked this question instead:
How would you DIY a relatively "uncolored" PA cabinet that is sturdy enough to transport, yet light enough not to throw out your back or give you a hernia?

Oh, I have commercially made flight friendy PA cabinets ,specially for: https://en.wikipedia.org/wiki/Les_Luthiers
Mind you, they are very hard to amplify because they use wild self made instruments:a cello made out of an oil drum, violins made out of Danish Ham cans, a trumpet made out of a water heater, Pan pipes made out of Lab test tubes, a marimba made out of hollowed coconuts, their keyboard is literally a keyboard: a typewriter where hammer-letters hit water filled test tubes and so on.
https://youtu.be/LyCDY5accVU?list=PL...sfi7n3eu-Wd4D1

Since they constantly fly all over the world they needed the lightest cabinets possible, I made them out of 9-10mm (3/8") plywood and JBL speakercomponents, which made them heavy anyway, but less so, a pound saved is a pound saved, no matter where.
Today I would have used Neodymium all over the place.
Knocking on any panel of course was like hitting a drum skin, or so it seemed, but by adding diagonal reinforcements and front to back braces they ended up being quite dead.
Then carpet covering on the outside (for protection more than anything else) also helped.

[Justin Thomas]

So just throw a few random pencil marks into the equation and call them "minus signs..."
I never was very good at math (except Geometry. But that's art.)

I saw all that when I read the entire thread...

Justin

[Leo_Gnardo]

Hmm, scalloped fan bracing or tone bars? Where should I put the sound post? This is getting surreal.

Sound post right smack in the middle, from front to back, in a Marshall 4x12. A piece of 2x2, there it is! As surreal as a flying mallet.

Save the scallops for your surf & turf dinner.