nollock

Cheers fellas, Ive decided to buy 12 G clamps and a couple of sash clamps. (Already got 2 of those.) Should be enough by the look of the pictures.

Thanks for the tip of having the sash clamps on both sides, makes good sense that

chris

Hi, i need to get some clamps. I can lay my hands on a couple of sash clamps, would i need more than that? I also need some G Clamps but what sizes shoudl i get? I was thinking of just getting mostly 4 inch ones and a few 6 inch? How many of each should I get assuming I will only ever be building one guitar at a time. I need to cater for glueing the splices of a neck thru guitar, i guess that would be the most clamp intensive job?

cheers,

chris

:edited: should be "flats" not "slab"

What does wedge or a flats mean in respect to bookmatched guitar top woods?

thanks,

chris

Yeah, the frequency response of the speaker sets a bias at the sound source, same for the piezo on the measurement side.  I've thought hard about how to subtract it out; we'll probably just look at relative differences between woods, or maybe use plywood or OSB as a baseline.

Maybe placing the piezo on cone might work; we'll try it and see how it looks.

You've got a good set of montor speakers to have such a flat response; what are they?

I have a set of Yamaha MSP5's, active monitors. But i just checked and I overstated the flatness of the response, i think its 55 to 20kz, give or take 5dbs, so I was only a factor of 10 out

chris

A small speaker attached to the wood could work, but i would attach it so the large metal chunk was in fixed very tightly to the wood. So the cone would act like the vibrating string and the metal frame of the speaker would act like the bridge.

That's a great analogy. The more I think about it, the more I like it better than just hanging the board in front of a cranked speaker. But I think I'd use something that responds well down in the <500 Hz range, like a 12" amp speaker.

Good point, you would have to consider the frequency response of the speaker. And no doubt the frequency response of the piezo pickup. Somhow you will need to factor them out of the equation cause each of those could posibly have more effect on the sound than the wood does.

I think you could take measurements with the piezo attached directly to the back of the speaker. That would in theory give you the response of your test equipment. And then you would need to subtract that from your measurements of the wood. Not sure how well it would work though.

The other option would be to have a referance material, pick one material as a neutral and make all the comparisons against that. So as all your comparisons are relative to the referance material, the effects of the piezo and speaker are canceled out. Mabey just test a bunch of materials and use the one with the most plain or flat response as the referance. Or just forget about a referance and just use your info to make comparisons between the materials rather than absolute statments about them?

To be honest i think a 12" speaker would be overkill, the speakers in my studio monitors are only 5 inch and they are quoted as having flat frquency response from 55hz up to 12k. At least within 0.5db across the range. But certainly cheapo PC speakers are not such a good idea now i think about it

chris

Our thought was that different wood types don't actually enhance certain frequencies; rather, they damp the ones you don't hear.

Yes, it is that the wood damps some frequencys more than others. The vibrations bounce about inside the material and some get attenuated quicker than others.

What you'd want ideally is one big strong piezo to vibrate the board at all frequencies (or sweep through frequencies) and another to measure what is damped and what is not.  I don't know if such a thing exists...

That would be the best way if you want to measure how the wood effects (or should that be affects?) the sound of the string. Some way of transmitting energy into the wood in the same way a string does. A small speaker attached to the wood could work, but i would attach it so the large metal chunk was in fixed very tightly to the wood. So the cone would act like the vibrating string and the metal frame of the speaker would act like the bridge. You could always butcher a set of cheapo pc speakers.

Its a facinating project

chris

Hi Erik, a place you might find helpfull is the music dsp mailing list. Alot of software developers measure the frequency response of tings they are trying to model. I am sure if you asked there they would tell you the best way to go about it. I suspect you would do best to measure the impulse response. Which means a very short blast of noise (hiting the wood with somthing very quickly might be perfecty good enough) and then you measure the response after that. The quick blast will get some wideband noise into the wood and then you measure the response, ie just record what sound it makes. That recorded sound is the impulse response, a spectrum analasis of that will tell you the frequency response of the wood. You could even use the impulse response to filter audio to see how the differant woods sound aplied to an common audio sample.

I am not sure a constant sine wave or noise will give you a very good measurement because inevitably any affect on the sound will be very hard to measure against the sound source. Its like reverb, you dont actaly notice the reverberation in most rooms untill you make a short sharp noise and then listen for the decay afterwards. Alot of rooms the decay is to short to even notice.

Likewise the way software developers model reverbs is by making a short sharp sound and then measuring the response afterwards. Ie measuring the "impulse response".

Personaly i would attach a piezo to the wood to record the sound, and try hitting the wood with somthing quite quickly. I would use the same object to hit all the test woods as that may affect the sound aswell. Chop the actual sound of the hit off the recorded sample and then do an spectrum analasis of the remainder. Mabey even do it 5 or 6 times and mix the sounds together so you get an average.

Anyway here is the music dsp site.

http://www.musicdsp.org/

If you decide to try there I advise you to join the mailing list rather than the web forum cause the forum is very quiet compared to the mailing list.

chris

Hi, ive been looking for a top wood for a carved top guitar and the chap from the shop has recomended Flamed Claro Walnut. I originaly enquired about black limba and then asked what other top woods he had when he said he doesnt have that. I have had a look round the net and I do realy like the look of it. But can anyone tell me what the sound is like, it have been thinking of putting it on a mahogany back and neck.

What kind of finish can be put on it? All the images I found had a natural finish but I was wanting to do a sunburst, or a trasparent color of some sort, would that work on walnut? And I am sort of womdering if puting colour on such nice wood is a bit daft.

thanks

chris

Ok, Ive been looking round the net to help in my (first) guitar design process and I have noticed that bookmatched tops rarely match up (at the join). Whats the deal? Even all the pictues on the PRS site show guitars with bookmatched maple that dont actualy match very well. Quilted maple doesnt seem as bad as flamed maple, and some other woods seem to work better.

So is it just heavily figured wood that doenst match well? Am i right in think this is becuase the figuring changes after a bit of sanding? I assume a carved top would bugger it up all together?

And so if i want a well (at the join ) matched top I should avoid heavly / fine figured wood?

Tbh I dont like seeing the join like down the center of the guitar, somtimes it looks ok but most of the time it spoils the look imo.

cheers,

chris

Just wondering why the majority of guitars have a maple neck?

cheers,

chris

Anyone got a link to a good article on bridges and their effects on teh sound? Do they even effect the sound that much? I dont use a trem at all so my choice would be a TOM but I also quite like this one hipshot hardtail .

Ive kind of got it into my head that the more directly or larger area that is conected to the wood the beter it will sound? Neck throughs have more sustain cause of a larger more solid conection right? So shouldnt a bridge be the same?

help a neewbie in need of enlightenment ;-)

cheers,

chris

litchfield:

Ive havn't been able to find any cheap bobin/spindle sanders in the UK. Cheapest was 160UK about 250USD. And I dont want to spent that much untill I find out if I have the patience to take this up as a serious hobby.

DeanZ:

I think I am going to go the drill press route for now. I found mjyself a washing machine motor today and it needs electronic controll so its to complicated for me. Anyway the drill press sounds like the best way, alot let hassle i just have to find a way to lock the height cause it is a drill pess / mortise combo with no height lock on it.

cheers

chris

Hello, I am in the process of planning for my first guitar, only tool I realy need is a bobin sander. My old fella has most the other stuff, a bandsaw, planner, routers and plenty of clamps ect... Anyway i am thinking about making a bobin sander out of a washing machine motor. My bro who's a mechanic geek reckons that you can get variable speed ones so speed should not be a problem and I found a bobin that will fit on a 5/8 shaft. Might even go as far as fitting a chuck on it. The idea being I can fit it under a bench and poke the bobin through.

Has anyone else tried anything like this or is it a bad idea? I think it needs to run at around 1200 rpm, fairly slow, does that sound right?

cheers, :-)

chris