[jedi.night]

I see alot of posts saying that so and so sub handled 25hz scene in (insert movie here).


How are you measuring the observed Frequency? A computer program etc...


Thanks.

 

[trapez]

I was fixing to post the exact same question. I thought at first it may be published somewhere like a rating for the movie, but I have yet to read anything like that. I think most just play it by ear and say 'yea thats a 22.5Hz.'


However, I found a listing that says these movies play 10hz and below! How they know this beats me. Maybe they can set the crossover to 20hz and below, if the bass moves then it must be in the 20Hz! http://www.eminent-tech.com/main.html


What im looking for is a test CD that plays 20Hz and below for about a minute or so. The Digital Video Essentials contains a Buzz & Rattle Test, 15 Hz to 300 Hz. The only problem is that the test starts at 15Hz then sweeps up to 20Hz and higher to quickly. I would prefer the signal to stay at around 16 for at least a minute, not one second. Regardless, it seems I can 'hear' the signal at 17Hz or 18Hz and I think im hearing it at 16Hz also, its kinda hard to tell.


However, by listening to the DVE CD will help train your ears at to what 20Hz, 25 Hz and so on sounds like. Then maybe after a while you can spot a 25Hz.

 

[b curry]

Use a DVD/CD with specific frequency tones for calibration for SPL. Be careful as sustained tones can cause damage to a driver; overheats the voice coil.


There are dB meters with selectable filters to measure selected frequencies.


What is being reported here for movies is a spectrum sweep done with PC software, microphone, sound card, etc.


The threshold for human hearing is considered to be 20Hz with an upper limit of 20kHz. Few can hear much below 20Hz, younger people mostly, as age and noise exposure causes hearing degeneration. If you do hear in the 15-20Hz range you will no doubt lose the ability with age and exposure. Lower levels are more of a feeling.

 

[ephemere]

I'm not sure you want something that plays LF for a minute. Risk of thermal damage. Linkwitz has an excellent toneburst CD for diagnosing bass down to 10Hz. I have it and it works well for detecting room modes and so forth. Here's the link: Linkwitz tone burst test disc

 

[cneely8]

>What im looking for is a test CD that plays 20Hz and below for about a minute or so.


Realtraps.com has a downloadable set of tones, in 1 Hz increments, from 10 Hz to 100 or something. They each last 10 seconds. Very useful for plotting room response...

 

[trapez]



Quote:
Originally Posted by ephemere /forum/post/0


Risk of thermal damage.

thanks for the heads-up, I didnt relaized that...might explain why its hard to find and most play for 5-10 seconds.

 

[Speedskater]

They run the audio track into an audio editing computer program like old "Cool Edit Pro".

The program's have frequency analyzing tools.