401 Plinth

The Stratmangler · Post by **The Stratmangler** » Wed Sep 23, 2009 3:08 pm

Nick wrote:Wonder what the best way of exciting the material is? a tap is not very repeatable.

Ball bearing and a tube, maybe ?

Chris

Dave the bass · Post by **Dave the bass** » Wed Sep 23, 2009 3:10 pm

Nick wrote:
Wonder what the best way of exciting the material is? a tap is not very repeatable.

How about exposing the piece under test to a loud audio signal? Say like via the probe of a sonicator, or some other way to mechanically connect the slab to a driven audio source.

Afterall its the effect on audio that were intersted in I I think isn't it?.... so it makes sense to test it under real audio 'induced' frequencies yes? Maybe? I'm waffling...

DTB

pre65 · Post by **pre65** » Wed Sep 23, 2009 3:11 pm

Strap a vibrating device to the slate ?

No No No--not one of them.

Cant think of anything that would fit the bill.

The Stratmangler · Post by **The Stratmangler** » Wed Sep 23, 2009 3:13 pm

Dave the bass wrote:Maybe? I'm waffling...DTB

So what's new, fellah ?

Chris

Dr Bunsen Honeydew · Post by **Dr Bunsen Honeydew** » Wed Sep 23, 2009 3:18 pm

Why create an artificial situation, it is music you are worrying about not bonks!

Just put your turntable on top of your speaker and place the stylus in a record groove with the platter stationery. Play music though a cd into the speakers and take the lead out from your phono stage to a 'scope. Incease volume of cd until you register a signal then you will see the nodes imposed on the music of the whole TT system not just the plinth. Experiment with design and set up until you get the smallest and least number of nodes and suck outs. You are also reading the nodes of the speaker cabinet but you can null that by always using the same speaker in your tests.

Dave the bass · Post by **Dave the bass** » Wed Sep 23, 2009 3:22 pm

Dr Bunsen Honeydew wrote:Why create and artificial situation, it is music you are worrying about not bonks!

Thats what I was alludin' to Dr B, 'real world' scenario = Music.

Good idea with just strapping it to the top of a loudspeaker cab, that what I was getting at, mechanically coupling the slab to an audio source.

Good idea's flowing team.

@Chris Mangler <big rasperberry!!!>

DTB

Mike H · Post by **Mike H** » Wed Sep 23, 2009 3:23 pm

Dave the bass wrote:Emergency thread recovery program initiated...

OK, if we were to attach a piezo pickup onto the lumps of slate and tap them....

What are we looking for? The ringing after the initial 'donk'?

DTB

Occurs to me if you had two pieces of slate with different resonances, it might make sense to sandwich them together. With some kind of rubbery type layer in between.

.

The Stratmangler · Post by **The Stratmangler** » Wed Sep 23, 2009 3:24 pm

After my initial alarm about Phil's vibrational response, I actually think he's on the right path.

Something that vibrates at say, 50 hz (thinking of Garrard motors here).

Chris

Dr Bunsen Honeydew · Post by **Dr Bunsen Honeydew** » Wed Sep 23, 2009 3:32 pm

The Stratmangler wrote:After my initial alarm about Phil's vibrational response, I actually think he's on the right path.

Something that vibrates at say, 50 hz (thinking of Garrard motors here).

Chris

So you dictate the node

Dr Bunsen Honeydew · Post by **Dr Bunsen Honeydew** » Wed Sep 23, 2009 3:44 pm

Resonant frequency exploration can be fun and I was involved in it in the 70's after meeting a New York acid head audio engineer at CES New York called Ken Sheaffer (SP). His first experiment was to calculate the resonant frequency of the human bowl and at a rock concert at Madison Sq Gdns during the interval he put it out through a Cerwin Vega PA rig from a sig gen. This was a new type PA with folded bass bins with wings that folded out and he wanted to see how low they went. Well the outcome was people didn't hear it but several people were injured in the rush to the loos and there were a few "accidents" to be cleared up. This got the police and authorities involved but he was never prosecuted just introduced to the CIA.

His second exploration was the resonant frequency of the clitorus (which interestingly doesn't depend on size) and he developed a product that he was trying to market but it never happened for some reason. It was a vibrator that you plugged into the tape out of your hi-fi and it resonated the music beat and amplitude with that frequency.

Would have been an interesting product, I have often thought about retrying to produce and sell it, definitely a Muppet Labs project in concept, Miss Piggy would love it. But I lost contact with Ken late 70's, probably died of a drug overdose if I know him.

shane · Post by **shane** » Wed Sep 23, 2009 3:46 pm

Dr Bunsen Honeydew wrote:Why create an artificial situation, it is music you are worrying about not bonks!

you will see the nodes imposed on the music of the whole TT system not just the plinth. Experiment with design and set up until you get the smallest and least number of nodes and suck outs.

That could take quite a while. Wouldn't breaking the process down into manageable chunks be more productive? Also, by concentrating on a part of the design (eg a slate armboard) would we not get a better idea of how different materials behave?

pre65 · Post by **pre65** » Wed Sep 23, 2009 3:47 pm

Dr Bunsen Honeydew wrote:
His second exploration was the resonant frequency of the clitorus (which interestingly doesn't depend on size) and he developed a product that he was trying to market but it never happened for some reason. It was a vibrator that you plugged into the tape out of your hi-fi and it resonated the music beat and amplitude with that frequency.

That made me laugh !

shane · Post by **shane** » Wed Sep 23, 2009 3:55 pm

Dr Bunsen Honeydew wrote: His second exploration was the resonant frequency of the clitorus

That would be a well damped resonance then...

Post by **Nick** » Wed Sep 23, 2009 3:56 pm

Yep, it was the variation between different material that I was interested in. I know its all been done before by every Mech Eng department in the country, but still fun to think about.

Dr Bunsen Honeydew · Post by **Dr Bunsen Honeydew** » Wed Sep 23, 2009 6:28 pm

The 401 with the Torlyte plinth is owned by Jim Kempton and I just browsed our members list and I have found - coincidence beyond coincidence - that he joined this group the day before I did.

His forum nom is jimkempton, so PM him those interested.

audio-talk

401 Plinth

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