question on hollows

General Discussion
1

for all the hollow kook-box builders out there can anyone tell me what how they resonate and whether they can be tuned?

Way back shwuz mention about the intonation he experience tapping on his makore veneered EPS cored fish and I know Paul has mentioned something more on the edge of resonance feel but I haven’t heard whether the construction method would allow for actual skin vibration like a classic wooden instrument with a bent and supported face.

been thinking of a project to make some dual use hollow woodies that could be used as wall hanging or in stand speakers when not being surfed.

Spruce tops are common in guitars as is cedar for some spanish made classical guitars…

the bracing and support would have to be thought out but I’m sure the curved deck as a sound face and a roy stewart type vent plug could be used a base port sound hole.

All it would take is the waterproof and ideal mounting of a soundpad vibrator and the establishing of a waterproofed banana plug on the opposite skin to make it work.

That is if any of the hollow woodie owners can confirm here that by tapping on their stick they can produce some decent intonation.

Those that have played around with NXT soundpads have confirmed that the best sound was created from those 2’x3’x 0,25" foam core panels you get in art store.

I was in the process of mounting some behind the 4’x6’ whiteboard in our conference room to convert it into a giant sound generation point source when it dawned on me that I could just prop up or hang two hollows on the sides of project screen/whiteboard for the same effect. As it would be a better looking approach in getting the same effect.

if it works it could be a niche concept for the home and office.

so to all kook-box builders and owners what’s your board sound like when tapped?

mahalo

just another crazy idea from a red dirt encrusted rock crab…

must be the heat and auto exhaust out here…

2

Actually, the most significant effect I’ve found on my compsands isn’t just from tapping them, but from finding their resonant frequency by singing to them…

I try to do this by myself, for obvious reasons.

Unfortunately, I can’t take my guitar out in the lineup with me, but I’ve found with my limited vocal skills that they have a primary note that resonates most strongly, then secondary notes that resonate with less intensity. The notes that resonate are different depending on if I am sitting on the board in the water, or holding it at arm’s length in the garage.

What practical application does all this have? None at all, as far as I can tell… But it sure makes for some interesting solo sessions when I can find a tune to hum that has my board buzzing under my junk every couple of measures. :slight_smile:

3

Hey Oneula,

You would have to have speakers less than 3" deep to accomodate them on a surfable board.

There are calculators on Sound System focus webites that can give you calculated box areas for the size of the speakers you’ll be using. Try this, scroll down the page for the calculator…

My HWS resonates but the amount of glass you’d put on in would stiffen up the vibrations…

Generally the entire skeleton system is joined with holes across the ribs, so the entire board would have air circulating throughout, you may not need to port the speakers at all…

Sounds like a fun job, the hardest bit about it would be making 2 boards the same…

Let us know how you get on…

4

Hi Bernie -

http://www.phys.unsw.edu.au/jw/violintro.html

The resonant quality of various materials in surfboards is often overlooked.

Simply tapping boards made of polyurethane foam core, EPS foam core, chambered balsa, solid balsa, solid Redwood and plank-on-frame hollows should give a rough idea of resonant quality. In the case of compsands, thickness and type of veneer along with density of the core would be the main variables.

In a conversation I had with a local board shop manager, it was revealed that Tom Curren claimed that he felt the difference between Surftech and Pu/Pe boards right “here.” (Pointed to chest) We agreed it probably had more to do with resonant qualities than the actual performance of the boards.

Even one board (of any material) will differ widely in feel depending on chop and surface texture. A solid wood board would provide the most solid feel while a light EPS or hollow would be the most resonant. Fine tuning beyond that could be quite a project.

5

actual Grant they aren’t speakers but are sound resonators for flat panel or solid surfaces like a white board or glass conference table etc etc…

Quote:
Soundpads create speakers into whatever you affix them to! Peel and Stick backing lets you convert almost anything into a speaker.

SoundPads stick-on speakers convert and transfer sound to most high density thin walled surfaces you put them on. Converts poster art, bookcases, thin tables, door panels and ceiling tiles into permanent stereo speakers. You cannot get a better quality speaker for the price.

Sound quality will vary from excellent to awesome depending on the surface you peel and stick them on. SoundPads let you literally feel the sound. They will blow your mind!

Simply connect them as you would any conventional speaker to your existing stereo using the amplifier or tuner. Once attached they are permanent.

picture

http://www.si5.com/products.php?pID=4024

based on this review it appears like you could turn a hollow surfboard onto a point sound source like a speaker if the skin can produce the resonancew I’m assuming it can…

Quote:
They sound better than they should!,

By Russell Edward Button (Alameda, CA USA)

I’ve been an audiophile since the Nixon administration. I first heard about the Sound Pads from a friend who is an accomplished loudspeaker system designer. I went over to his shop the other day and sat down to listen to his latest system configuration. It wasn’t quite what I was used to hearing there, but I figured he’d been fooling around with his digital equalizer. He typically runs some very esoteric high frequency horns along with some enormous sub-woofers. What I was hearing was pretty good, but not quite up to his usual grade. Hanging from his ceiling next to his prototype loudspeakers were a pair of 2 foot by 3 foot pieces of foam core, the stuff that artists use. I figured he was doing some sort of acoustic room treatment with them. I was more than surprised when I went up to examine his speakers and found that they were not playing at all, but that the sound was coming from the hanging pieces of foam core!

The foam core pieces each had two Sound Pads taped to their backs. He was using two Sound Pads for each side to get more efficiency. The foam core was 1/2" thick. We talked about what materials he was experimenting with for use with the Sound Pads and it was agreed that light and stiff materials worked best.

No, this wasn’t truly high end audio, but it was miles better than the usual dreck you get from places like Circuit City, Good Guys, and the like. It was good enough that I could have enjoyed myself listening to that all night. You’d have to spend a good $1500/pair for speakers that would be any better than these things!

Now mind you, the idea of hanging 2 foot by 3 foot pieces of foam core from your ceiling, and draping speaker wire along with it, probably won’t go over very well with your wife. But if you do your listening in a college dorm or co-op, wood shop, auto shop, or some other less tidy environment, this could really work well for you. These things sound GOOD!

I was planning on displaying a couple of my compsand boards on vertical stands in the office as personal artwork anyway which is why this idea popped up… A couple of 6’ classic hollow cedar fishes might be call here with these soundpads epoxied underneath to the skins inside the boards…

crazy as mullet I guess

a blind mullet maybe…

6

thats is totally wiked man

bass response should be good on all balsa

7

there was a proffesor of music at the fish fry teaching Tom Wegener and Paul Joske about the sounds and resonance of wood… heres a pic http://www.diversesurf.com.au/index.php?categories=fish%20fry

8

Hi Oneula!

Great idea! You could play the sounds of big dolphinbulls while paddling, and the sharks will be happy to take the rear seats in the audience…

I´ll have to be shortly nonsurftopic in trying to help you to get a better sound out of your work.

Basically the hi-end-hi-fi-goal is always to get a most linear sound reproduction of the source over all audible frequencies.

The above mentioned resonance therefore has to be free of peaks in certain frequency-bands.

Roughly speaking: a loudspeaker usually works with a membrane and a shell, both of them ideally designed without the flaws of frequency-peaks, which would destroy linearity.

The important thing about the sound pad mentioned above is, that it turns some flat piece of hard and light material into a membrane only.

The thought behind the loudspeakershell now, is basically to shut off the membrane´s countermovements on the backside soundwise, because if reflected to the listeningspot, they will mix with the sound of the frontside in all kinds of annihilating interferences, thus disturbing linearity.

That said, the difficulties in getting a good sound out of a HWS as a shell might be clear to see.

Closed shells are stuffed with damping materials, and bass-reflex shells, as well as transmissionlines are hard to controll.

The idea of a pure membrane naturally gets rid of all the tremendous difficulties in making a shell out of a flat surfboard. For a membrane flatness is an advantage, and if the bass is not strong enough, there is always the possibility to use a hidden subwoofer, of which the better one´s cannot be located by the human ear.

Actually eps must be the better choice for a membrane, as hardness and lightness would be the key qualities together with some ability to smoothe out funny resonance-peaks inside.

One of the worlds finest passive bass speakers, the “Kef B139” uses an eps membrane.

Have fun experimenting in the world of “high fiddling” or what was it called!

Cheers - D.

9

Hi Oneula,

This was such a fun idea that I had to try it.

I don’t know anything about real speakers but I do have a cd player and I listen to a lot of music.

So I bought a pair of the Sound Pads you mentioned and stuck them on a pair of 5’11" Red Fir Fish that I had left from last year. These were boards that I had glassed in polyester instead of epoxy (Schwuz questioned me on that and I insisted that I knew what I was doing - famous last words). They delammed after a few months of hard riding. Pretty boards though.

My review: My new 5’11" fish speakers look cool and sound fine. Definitely better than the little speakers that originally came with my system. The only catch is that now I am going to have to sell them on Craigslist or something - they are too big for my little house!

Anyway, thanks for the cool idea.

Lars

10

If you can make a guitar into a surfboard…you can make a surfboard into a guitar.

11

Hi Oneula -

Have you heard of positioning two front speakers in conventional “stereo” configuration combined with one big rear speaker that is fed by one “+” lead from each of the fronts? Supposedly it creates an interesting third channel to the mix.

I guess it’s a pretty old technique now rendered obsolete by the theater sound amps commonly available in many systems.

12

yup John did all that back in the 70’s - 80’s

actually when I was on the mainland I used to be a big poop head audiophile drooling over all the british high end and tube mono amp stuff.

We’ve actually just gave away our 40 year old Grundig tube stereo console we bought in the 60’s in germany(my dad was a stereo fanatic as well) to our mailman cause he wanted to play aorund with tube electronics. When I busted out some specially recorded super high fidelity vinyl I brought back and played it through the this old tube stereo I was blown away of the sounds it brought out from the recording… Unfortunately the console took up half the room (way different than the minimalist british stuff).

I was just thinking about how to decorate my office and our conference room when I came up with this crazy idea. I guess it works…

Jay

From what I understand about solid body electric seems like you would want something super heavy and superdense like a les paul to get the best sound compare to a violin, cello or spanish guitar design… Infact I think some of the new ukulele design like the faceboard thin and stiff. The Rainbird(sp?) carbon fiber dreadnaught guitars are popular here on Maui as are the 12 string Ovations for a working mans bang around gig partner…