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5

I use Cold Gold, a few other hand-made ones, and the rubber contact-mic adapter for the Aquarian Audio H2a hydrophone. The C-Ducers sound pretty compelling - high noise floors are common with cheap piezos - but the H2a is a stellar contact mic...provided you can attach its heavy bulk to something effectively. Tim Prebble and others also like the Barcus Berry ...


4

Ruben, You mention that you don't wan't to incorporate phase at all—I'm guessing that you mean you don't want to design a kind of phase shift based on delay? Keep in mind that, unless your two mics are placed in the exact same point in space, there will be some difference in time arrival (aka, a phase difference) between the two signals. This is a very good ...


4

The simple answer is no - there are some misunderstandings that I need to clear up for you: The audio and video frequencies you have coupled in an old fashioned TV signal are so far apart that there is no overlap. (Audio 20Hz to 20kHz, and video is up around 4MHz) When the signal goes to the TV, the audio frequencies are decoupled, then the horizontal and ...


4

Consider using an anechoic chamber from others. Every microphone and speaker manufacturer will have one, most Universities have huge EMI measurement chambers (working perfectly). They might let you use it for an hour at a time, or you can rent it for a day for some more money. If you need to build one by your self, start with a noise floor measurement box. ...


3

There are a number of factors involved here but mainly frequency response, transient response, signal to noise ratio (S/N) and total harmonic distortion (THD). Frequency response is largely dependent on the size, shape and mass of a speaker cone and there is no such thing as a speaker with perfect frequency response. But most significantly, the size of a ...


3

Quite an interesting project indeed. The paper towel roll and cups are are working as an acoustic megaphone, also called (in ancient times) speaking trumpet. Directional focus of the radiating sound waves is part of the way the megaphone works, but that's not all, as, as you have noticed, there is also amplification in other directions, not just the front ...


3

Here is a nifty preamp circuit that provides a FET buffer and balances the signal, which deals with all the issues you are discussing. The circuit is based on the work of Alex Rice.) You attach the piezo to the circuit with a length of shielded mic cable, then run a mic cable from the circuit to a male XLR. This plugs into your recorder which supplies ...


3

contact mics are pretty cheap. I own some cold gold ones as well, but I never use them anymore. Now I roll with my Jez Riley French C series ones. here's some classic laser stuff I did with them: [soundcloud]rcoronado/guy-wire-contact-mics-huge[/soundcloud] I run them through (inexpensive) hosa MIT-129 impedance transformers to get them matched up ...


2

Though I don't own any, Barcus Berry contact mics sound awesome. I use the Aquarian Audio H2a contact mic adapter. I also bought a contact mic a couple of years back from these guys. Don't think they sell their mics anymore, but there is a useful guide on how to build your own. I'm also looking forward to hearing more about the new Trance Audio stereo set ...


2

They can definitely be tricky to get usable material out of but with some experimentation can yield some amazing source. I have a bunch of various contact mics from these guys: Cold Gold http://contactmicrophones.com/ They make an interesting and affordable selection of various transducers. They also sell some of the bare parts for making your own ...


2

The key to a good contact mic lies more in the preamp than in the transducer itself. Contact mics will inherently pick up sound from a very unique perspective, but you need preamp circuitry that will not only keep noise low but will also provide the necessary impedance to match the high load of the mic itself. Because impedance is a frequency-dependent ...


2

Traditionally, it was called "grille-cloth" and it was made from a coarse-weave of rather thick plastic filaments. It is still available in many places, particularly those vendors who supply people restoring vintage equipment. Modern speakers tend to use more conventional material similar to (or identical as) common, inexpensive polyester double-knit. It ...


2

It's actually a complicated thing, how much space to put behind a driver. The air mass behind the driver actually affects how the driver moves. If you put the right volume of air behind the driver, you can even out the low end. If you put the right volume of air and the right size port, you can change the frequency response of the system (with a few ...


2

There are pre-existing facilities that regularly measure the frequency response of microphones. you should call one of them (try pcb) and talk to them about your project... A chamber might not be the best way to measure this. But if you do want to build a chamber, a lot depends on what the lowest frequency you want to measure. If you have a quiet space, ...


2

In response to Colin, I too am curious about the stereo Trance Audio rig, so I wrote them. They responded with the following specs: The stereo Inducer is a custom-built specially designed low-noise high-definition stereo system that's aimed towards sound designers. The Inducer runs 2 Acoustic Lens transducers, the heart of the system. The Lenses, which ...


2

Schizomorph makes a solid answer for all the technical details, but I'm going to break it down more basically. Sound consists of pressure changes. A speaker makes sound by moving a diaphragm that pushes air to make pressure changes. The volume of a sound is determined by how much air moves and how fast it moves. Small speakers can only move so much air....


1

Yes, you can shunt (short-circuit) the two signal conductors of the stereo cable and connect the output from the VCR to that cable with fear of damaging your equipment. This is a common quick fix for this type of situations. frcake's comment about a signal splitter (by which I suppose it is meant an active device with a preamplifier) has some justification, ...


1

Pitch content that roughly matches the resonance tendencies of the shape will also get a boost relative to the other frequency content. The resonance frequencies of the tube are probably very limited, hence the sound will continue to be unbalanced in terms of EQ. The flare of the old phonographs have a wider range of resonant frequencies. The vibrations of ...


1

It is no practical problem to use a 75mm diameter instead of 80mm. It could even be that you have the correct size already, as (for the loudspeaker as such) it is the inner diameter that is relevant. In case you were talking about the inner diameter and you want to obtain a "super accurate" result :-) , the relative reduction of area (75²/80²=0.88) leads to ...


1

The Specs on the Brookstone Big Blue Party speaker: 4 speaker drivers, subwoofer and passive radiator Power: 72 watts (18 watts per channel, 36-watt sub) Frequency response: 40Hz-20kHz Dimensions: 6.3"w x 6.3"d x 15.8"h The frequency range of the the speakers you linked go down to 70HZ and up to 20kHZ, The Brookstones go down to 40hz, I do not know if ...


1

Generally speaking a shield should not carry signal. It should be grounded at one end, usually the source but in this case probably at the input. That would mean connecting the hot signal line to the tip and the return signal line plus the shield to the 1/4" sleeve, assuming that the sleeve is at ground on the input, and leaving the shield unconnected at the ...


1

Unfortunately "small" and "anechoic" are mutually exclusive, at least at low frequencies. The length of the wedge absorbers needs to be at least a quarter of a wave length plus some extra space for the field dissipate. If you need to do less-echoic measurements, your best shot may be to find a large open space, get as far away from reflecting surfaces as ...


1

I'm afraid for that budget you're not going to get it any better than a single stationary mic. Both flute and violin are rather easier to mic and bring out in a PA mix than acoustic guitars, mandolins etc., so if that's the context, you have no drums, electric guitars etc., I'd stay with a single mic. Of course, you need to set it up right! First, you ...


1

Cellotape - I think it would sound very christmas-like if you layer some bell jingling with cellotape being stretched out for gift wrapping :) For the gift shaking I would use a shoe box and fill it with various types of objects for example:- plastic toys, DVD cases, coins etc. Then shake the box with various degrees of excitement! In terms of tree ...


1

I am curious what specific wire did the metalwork artist recommend to you? To join bronze rods to stainless steel I would try one of two different ways: silver soldering via torch or bronze brazing via TIG. I've used regular Silicon Bronze extensively to braze weld steel using TIG, but have read that you need a flux to braze/braze weld to stainless due to ...


1

Well, with the material prices you are quoting + plus the research/development that must have gone into the originals, the cost of a Waterphone is entirely reasonable I'd say. I do lust for one myself (just listen to the Tom Waits song "Shoreleave" to understand why). I guess getting all the individual elements of the instrument together in just one package ...


1

Found this http://blog.makezine.com/2011/12/20/collins-lab-diy-contact-mic/


1

I've succesfully build some mics using electret caps. I began with the panasonic wm61a soldered on a rugular 3,5mm plug cable running on pip. It was ok. I attempted the Alice build, but got stuck as the my circuit wasn't working. I've set it aside a haven't picked it up since. My most recent build is a dummy head for binaural recoding using the Primo em-...


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