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

[Mike Sulzer]

Materials that are highly damped - particle board, MDF, panels filled with dry sand like Wharfdale used to use, concrete, etc. - do not add the colorations we're addicted to as guitarists. They also tend to be heavy and may or may not be strong and durable for moving from gig to gig.

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. Looks like an interesting design project. I suppose these days it must be done the dreary way: get some humongous software package and simulate until you understand what effects what and how. No, no. More fun just to use intuition!

[Steve A.]

Materials that are highly damped - particle board, MDF, panels filled with dry sand like Wharfdale used to use, concrete, etc. - do not add the colorations we're addicted to as guitarists. They also tend to be heavy and may or may not be strong and durable for moving from gig to gig.

Viewed in that light, I wonder whether the work on woods from Joseph Nagyvary would help with good acoustic guitars and electric guitar cabs.

I had to google the name Joseph Nagyvary who researched the wood used in Stradivarius violins and has been building copies which rival the originals. One factoid: "Because of the lack of land in Venice, during that period imported [maple] was often stored in the seawater of the Venetian Lagoon, where a type of decomposition had a slight effect on the wood. Nagyvary managed to acquire wood shavings from a Stradivarius violin, and under a microscope he found the natural filter plates in the pores between the tracheids were gone."

Here are some links:

https://en.m.wikipedia.org/wiki/Joseph_Nagyvary

Nagyvary Violins: Violin Shop: Violin Maker: Violins and Cellos

PLOS ONE: Mineral Preservatives in the Wood of Stradivari and Guarneri

Steve Ahola

[J M Fahey]

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. Looks like an interesting design project. I suppose these days it must be done the dreary way: get some humongous software package and simulate until you understand what effects what and how. No, no. More fun just to use intuition!

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.

[Steve A.]

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.

That makes sense but I had a question about acoustic guitars which will have a resonant frequency at which it will feed back. How does that fit in with what you said?

Steve Ahola

[J M Fahey]

That makes sense but I had a question about acoustic guitars which will have a resonant frequency at which it will feed back. How does that fit in with what you said?
Steve Ahola

It fit perfectly, of course.

In the acoustic guitar the sound producer is the "cabinet", a.k.a. the body.
The membrane coupling to air and moving it is basically the guitar front, vibrated by the rigidly attached bridge, in turn moved by guitar strings.
There's a reson it's sometimes called the soundboard.

There is no other piston pusing air, specifically no speaker cone, only the front panel vibrating.

Of course, it must be thin and relatively light to move air efficiently and any resonance which will make it move more will cause a peak at the resonant frequency.

In a speaker, on the contrary, the piston moving air is the speaker cone itself, and it's being driven by voice coil and magnet.
Cones are specially designed to be as light and rigid as possible, if possible they should move as a single unit pushing air.

If , after we move *air* which is a hard task , then we pull energy from said vibrating air by any resonant body nearby which is coupled to it, we lose energy, we have a dip.

So in a nutshell: most people ignore the very important difference that in a musical instrument the "cabinet" is a sound generator , while in a speaker cabinet the speaker (which is absent in the instrument) is the sound generator and the cabinet is a lossy load.

Even if a cabinet vibrating panel moves some air, nobody denies that, that power was *substracted* from a vibration *already* present in the air, and the cabinet panel is a very poor radiator compared with the original speaker cone.

[frus]

I have an acoustic with dead spots, what goes on there then?

[Richard]

I had to google the name Joseph Nagyvary who researched the wood used in Stradivarius violins and has been building copies which rival the originals. One factoid: "Because of the lack of land in Venice, during that period imported [maple] was often stored in the seawater of the Venetian Lagoon, where a type of decomposition had a slight effect on the wood. Nagyvary managed to acquire wood shavings from a Stradivarius violin, and under a microscope he found the natural filter plates in the pores between the tracheids were gone."

Here are some links:

https://en.m.wikipedia.org/wiki/Joseph_Nagyvary

Nagyvary Violins: Violin Shop: Violin Maker: Violins and Cellos

PLOS ONE: Mineral Preservatives in the Wood of Stradivari and Guarneri

Steve Ahola

When I don't have room for something I usually store it in the lagoon.

I don't think comparing a new instrument with one that is nearly 300 years old is the best measure. What did it sound like when new? What will Nagyvery's violins sound like in 300 years? I don't care for holding a particular instrument up as the standard and compare the rest to that. What do I want my guitar to sound like? The originators did really well but there's no reason why the definition needs to be so strict.

[Mick Bailey]

I get the idea that neos lack thermal mass to absorb the heat, a large heavy magnet acts as a heat sink. Is that true?

Interestingly, I see a lot of failed neo speakers. All of them fairly recent manufacture and in situations where any decent ceramic speaker would hold up. Bass cabs seem to be the killer.

[Mike Sulzer]

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.

Selective absorption is one way to emphasize other frequencies, at least in a relative sense. In any case, I doubt that the only effect of the stiffness of the cabinet panels is to soak up energy. For example, a plywood wall transmits some sound. This happens because the wood vibrates.

The front panel, in particular, is directly driven by the speaker, and its vibration, at least at low frequencies, is out of phase with that of the speaker

[Chuck H]

Juan and Mike have it. Most vibration from the cabinet is subtractive. it will be either out of phase with the speaker or absorbing energy. Funny that I've been known to knock on a cabinet anyway to try to hear what it might sound like Considering the various anomalies of speakers that really tells me nothing. I wanted to give a nod to combo and ported cabs though, where some cabinet vibration and air movement from the back of the speaker cone can actually be in a phase relationship other than opposite due to the physical difference those vibrations travel. With this element included I can't imagine trying to reconcile all the variables to design an intentional effect. Which is probably why sound reproduction and reinforcement speakers are usually designed to eliminate the cabinet vibration variable. And a resonant guitar combo cab is mostly a happy accident. I've have experienced situations where a resonant cabinet did seem to sound bad (to me) no matter what speaker or amp was used. With nothing else being unusual about speaker arrangement or cabinet volume. I had to assume that "I" just didn't like the effect that particular cabinets resonance had on the guitar sounds "I" prefer. And changing to less resonant front and rear baffles did improve the sound.

[J M Fahey]

Of course any reasonable wall will vibrate more or less, concrete cabinets are for fixed installations, the point here is that same type of resonance, will make a peak in an active "sound maker" panel, as in an acoustic instrument, but will soak same frequencies in a passive element, which does not take power from amp or vibrating strings (or mallet hits as in a Xylophone) but from sound already produced and radiated by some other element, the speaker.

I have an acoustic with dead spots, what goes on there then?

An acoustic instrument is a true wonder of skillful design, and being that they exist since thousands of years




and of course development has been by ear, by trial and error, no computers or simulators way back then.
Not even modern times Leo had them .

So it's hardbto do things the right way, lotsn of "black magic" involved if you want to call it that way.

So: your guitar has some dead spots?
Sure, why not?
I bet others which *apparently* look the same sound better.

There is a reason similar looking instruments can cost from $100 to $14000 .

You can easily automate electronic stuff manufacturing with excellent results .... solid electric instruments not so much ...... acoustic ones are much harder and require constant control, 2 batches of apparently same wood (which is an organic, not homogeneous material) but different humidity or different byears will not be the same, not sound the same.

[rjb]

Question from a pre-noob

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

[frus]

There is a reason similar looking instruments can cost from $100 to $14000 .

Sure, I was just wondering about the physics of it, since you've said that any resonance will cause a peak at the resonant frequency

[bbsailor]

Sure, I was just wondering about the physics of it, since you've said that any resonance will cause a peak at the resonant frequency

Physics provides an attempt to explain why we like some particular sound characteristic but cannot explain why a particular sound characteristic is better or worse than another. See the link below to see where the varables between bass, mid-range and treble are seemingly defined. https://www.avforums.com/threads/bas...-what.1179209/

Remember, the guitar seems (to human ears) to have a sound that is at twice the primary string frequency due to the harmonic structure of the guitar.

Joseph J. Rogowski

[Mike Sulzer]

Remember, the guitar seems (to human ears) to have a sound that is at twice the primary string frequency due to the harmonic structure of the guitar.

Joseph J. Rogowski

I do not believe that that is correct. I think that the perceived frequency of a guitar note is set by the spacing of the harmonics, and for example, the open low E string has the spacing appropriate for the approximately 82 Hz fundamental, not 164 Hz. Do you have a reference for that statement?


This from your reference:
"So, while we can hear above 5,000hz, there is not much up there to hear. Just harmonic 'echoes' of lower frequencies. Though these harmonics are vitally important to giving an instrument its unique voice."

It is nice that harmonics finally get mentioned, but that statement is ridiculous. 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.