Room acoustics null test experiment

Recording two of the same samples of music in a room and differentiating (nulling) them to find the results.
Mail: PO box 362, Vandalia, OH 45377
Thank You!

[Berre]

You could test the influence of speaker cables on the reproduction of the music. Some 'believers' claim they can hear the difference between a cheap, "low quality" cable and an expensive thick "high quality" cable. I am pretty sure there is no audible difference.

[TrystansWorkbench]

That was very interesting John. Fascinating stuff. I've noticed myself when I run a single frequency tone from a single resonant speaker that the acaustic perception is quite pronounce if I move my position in the room. So your experiment is incredibly evocative. Fond greetings from England - I was the chap that sent you that Christmas card to you and Snickers a couple of years ago! Trystan

[stucorbishley]

Love it! Got my mind churning with ideas!

[joshhyyym]

This is interesting, I thought, from your introduction you were going to null out the sound in the room live. i.e. by having a microphone, inverting amp, and speaker. Like with noise cancelling headphones. This was very interesting too. It would be a useful tool to use when setting up acoustic treatments for a home theatre / listening room - I wonder if the mic on a smart phone would be accurate enough for this.

[HillsWorkbench]

I have been using VideoPad making videos where I have two pairs (stereo) of mics to sync up. I can only sync up within one frame but that is still a pretty thin slice of time. If I can't line up the two exactely I have to think which mic was closer to the speaker's mouth. If the speaker or one pair of mics is moved I can see it in changes in that sync. I usually dump or deeply attenuate the in-camera audio in the final video, the noise level of the recorder is drastically lower, but still sync for action and lip-sync.

[e.michaelkessler]

Way back in 1974, Bear Stanley used nulled microphones to create the monitorless "Wall of Sound" PA system for the Grateful Dead. The sound was unmatched for that time period.

[guestwho]

Wow! I've never realized that by zooming way in, Audacity can show individual samples as dots.

[ablebaker]

Check out software called REW. "REW is free room acoustics analysis software for measuring and analysing room and loudspeaker responses."

[pratbrat]

trying to build a preamp circuit using op amps and 12v supply split using voltage divider to take the high impedance signal from my guitar and make it close to stereo line level to be used with stereo amplifiers. I would use j fets but I cant buy them locally. would really appreciate some advice or a dedicated video on the topic if you're interested. anyway love your videos. keep up the good work

[dogbucket]

Chapter 1, 421 of the JAT audio experiment odyssey, in which John first discovers the "Snickers effect", which results in decades of heated argument among audiophiles. Snickers remains blissfully unaware.

[Gersberms]

Very cool idea. What would it take to almost completely null out the higher frequencies? I was surprised how much of that came through in the first null file. Maybe play and record the song on repeat and walk out, open up curtains and blinds, remove things that can move and vibrate.

[danielsanichiban]

Doing it this way, you won’t be able to null out recordings well due to misaligned decimation in the converters and clock drift. You need record and playback simultaneously on the same AD /DA. Shifting samples on the timeline isn’t good enough

[neddyladdy]

Differentiating is completely different thing from what you mean. Differentiating is a procedure used in calculus. You mean taking the difference.

[genebennett]

make you realise how exhausting it is to be a human observing the world....

[russellhltn]

Seems like a challenge to sync when the samples happen at different times. That is, the recording clock and playback clock are not synced. I wonder if you played back from Audacity while recording new tracks with it would help align the samples so they occur in the same place each time.

[nicoras]

A very interesting experiment, this explains why room treatment is really snake oil. This was a very worthwhile experiment, and I am setting up to do the same just out of interest. Maybe try some white noise and a mono signal input.

[MrBrymstond]

For a free program, Audacity is one of the best and easy to use.