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Test Tones

Discussion in 'Subwoofers' started by stonking, Apr 28, 2005.

  1. stonking

    stonking
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    Hi all. I have downloaded a file that has test tones from 15hz to 80 hz They rise one at a time and the whole thing lasts for about 5 minutes. Trouble is, my sub plays the 15 hz tone and I can hear it. I can hear all of them. I thought I was not supposed to be able to hear them below about 25hz. Oh before you swoon about in amazement of my powers, the rest of my family can hear them as well. Is this normal for one of these tests?
     
  2. Crustyloafer

    Crustyloafer
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    Which subwoofer have you got? What is the crosssover set to? It's not an MJ Acoustics is it? They have very poor quality crossovers by the way.
     
  3. eviljohn2

    eviljohn2
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    It should be normal, yes. The human hearing range is approximately between 20Hz and 20000Hz pure tone but this varies significantly with age and other factors.

    There are a number of reasons why the tones below 25Hz will be audible:
    * Your hearing reaches down to that level.
    * Harmonics produced by the subwoofer will be at higher levels.
    * Cabinet resonance may be audible at a slightly higher frequency.
    * The sound may be rattling something else in the room that you can hear shaking.
    Amongst many other possible reasons.

    It's really nothing to worry about and don't read too much into it. :)
     
  4. Ian J

    Ian J
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    Did you buy the Velodyne in the end ?
     
  5. stonking

    stonking
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    Ian, No but it was close. Went 150 miles to hear it etc but just before I got there it died so all I could hear was a popping noise from it. Ended up buying a Paradigm PW2200 off this forum. Still setting it up. Hope to finish moving it about this weekend. If anyone wants to compare it let me know. I'm at Junction 6 M25.
     
  6. bob1

    bob1
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    I can hear my sub down to 20hz when i play a 16hz tone i can't hear anything but can feel the pressure crushing my skull ,i would agree with eviljohn2 and its causing other noises.Can you hear the tones change in frequency?
     
  7. stonking

    stonking
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    Yes I think so. Crushing my skull is a good description and I would add that within seconds the wife appears mouthing obsenaties and it could be that she is saying "turn that down" but I cannot be sure. I am guessing that 30hz + is when I notice distinct tone changes. Does anyone know of another test I can do?
     
  8. eviljohn2

    eviljohn2
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    What are you trying to actually test for? :confused: There's far more to a well performing sub than simply how deep it can go.
     
  9. Nimby

    Nimby
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    It rather depends on what you mean by "hearing" a low frequency sound.

    My big SVS cylinder makes a very soft purring noise as it gets down to 20 Hz. There is no real sense of tone at all. More of a soft beating sensation in the room. As the frequency of the tones falls further the purring becomes *very* soft and fluttery until it finally goes completely quiet in my ears but a pulsing pressure can clearly be felt in the room. This occurs at about 18 Hz with me and my sub in my big room.

    Age makes a difference as the ears become less sensitive at the frequency extremes with age.

    At about 16 Hz and below the old bedroom windows are rattling so badly that 2 seconds is about all I'm allowed before I'm told to stop. Even at very low levels on the gain things rattle throughout the house and even out in the greenhouse at these low frequencies. The pressure effects are tremendous as Bob says.

    The degree of audibility of low frequencies is very dependant on the level at which you play these low notes. The louder it is the more you can hear it.

    I think others have already covered the likely causes of audibility of a sub below about 20Hz.

    Harmonic distortion is the most likely culprit if you can hear any tone below 20 Hz. It should be the softest imaginable breathy flutter. Wandering round the room should pinpoint any sympathetic resonance in furniture or glass adding their own noise to the fundamental notes.

    Be careful when playing these low frequencies. You could wreck your driver or burn out the coil in just a second or two on a continuous tone. Remember that most LF effects are very short lived. Not many subs can cope with continuous tones at these very low frequencies.

    Nimby
     
  10. stonking

    stonking
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    Nimby, thanks for the advice. EvilJohn2, Good question. I was hoping to hear a clean tone that I could hang my hat on and say "Yes thats got it" but its as nimby says its more fluttery down low. The description of "clean Bass" that I have read is what I was looking for, not boomy, so I am guessing I need a tone around about 40hz. My cutoff is set at 65hz because my front speakers are MS 815's and they go pretty low.
     
  11. eviljohn2

    eviljohn2
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    There's no way you'll be able to hear "clean" bass using just a test tone - most subs do a decent job with a pure tone.

    You should try playing a fairly slow frequency sweep (high down to low) such as that on the THX Optimiser. Listen out for anywhere that you can hear the volume changing - this is unlikely to be a fault of the subwoofer until you reach the lowest frequencies but will help to indicate any integration problems where you crossover with the main speakers and sub plus how your sub interacts within your room.

    Otherwise, the best test of a sub is really to get down and dirty with the CDs and DVDs that you know well! There's plenty of test material posted on this site and on the internet in general. :)

    EDIT: I should warn you that attempting tests like these may well lead to you onto the path of becoming obsessive!
     
  12. Mroizouk

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    I'd agree with Nimby's description of those sub-20hz tones. You'll get more evident, pleasing 'hang your hat on' tones between 25 and 40hz i'd have thought

    Just play some nice, bassy music. Much more enjoyable than test tones, and you're more likely to experience a 'that's it!' moment with some nice musical bass in context rather than the 'poooooooooooooooooo' of an isolated sine-wave.
     
  13. JBL 4645

    JBL 4645
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    And if you can hear 15Hz which doubt very much…you are feeling it…infersSonics can be, :lesson: and if played at the correct frequency at around 7Hz and if played at very high sound pressure levels will mach the bodies resident frequency and this can result in….

    Feeling dizzy…chest pains…internal damage…and fatal death…. :oops:

    So doesn’t fool around with infersSonics…to much unless you are so incline too do so…?
     
  14. Mroizouk

    Mroizouk
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    Although the PW2200 is a pretty beefy sub, I don't think it will actually produce bass which is lethal. These subsonics which can harm your health- 7hz makes human tissue disintegrate- need to be at a high intensity to have any ill effects on people. There used to be freak occurunces in factories when the air in a chimney started oscillating at the resonant frequency of the chimney, which happened to be 7hz. Many workers took time off work feeling very ill, only to feel fine once they were outside the factory environment and this harmful subsonic noise. 7hz is totally inaudible so no-one noticed it until they figured out what was happening.

    They also played around with giant prototype speakers for playing sub-sonic tones at the enemy trenches in WWI. However, they never managed it. It's very difficult to do. I honestly don't think 'stonking' is at much risk to 'internal damage and fatal death' from his home cinema system.

    JBL: 'fatal death' is a bit of a tautology. Have u heard of any non-fatal deaths recently?
     
  15. JBL 4645

    JBL 4645
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    None recorded as of yet in the home cinema arena…but there is always the possibilities…

    And the Japanese did testing of infersSonics in World War II on human subjects...makes my skin crawl it does…

    Anyway let’s not talk about this any more shall we…

    Ashley…
     
  16. eviljohn2

    eviljohn2
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    Without meaning to be difficult, infrasonics will not make human flesh disintegrate but will certainly make the internal organs (the kidneys in particular I believe) shake about like nobody's business. Ultrasonics are capable of destroying tissue (like in kidney stone treatment) but each require very specialised and expensive equipment.

    There's certainly no need to worry about either in the HC environment. :)
     
  17. Mroizouk

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    Very well, I'm not going to argue the toss. Those were just the words used by the article I read this info from. I've no idea where I came across it.

    I have more recently found an article online which talks about different sub-sonic frequencies as having localised effects on different areas of the body. Quite interesting.

    http://www.rhfweb.com/hweb/shared2/Newrad.html
     
  18. JBL 4645

    JBL 4645
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    Man, that makes my skin crawl…I’m sorry I even looked at this one…

    Some of us sound fairly educated and, ok then it’s a question of science…remember that film called Brainstorm with the late Natalie Wood and Christopher Walken…tapping into the mind…

    That’s how I feel about infersSonics….

    Ashley…
     
  19. alexs2

    alexs2
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    Ultrasonics have long been used in specialised surgical systems for hepatic and neurosurgery,to minimise bleeding in very friable tissues,and given all the comments above regarding the danger of infrasonics,the principle on which a lithotripter(for disrupting kidney stones without resorting to conventional surgery where appropriate) works,is that of focussed shock waves at extremely low frequencies(commonly 1-2Hz)resulting in pressures of up to 400bar at the stone surface.

    Thus despite all of the worries being exhibited above,when used appropriately,both ultra,and infra sound have beneficial uses,even at very high power levels.
     
  20. JBL 4645

    JBL 4645
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    The same technique is used on astronauts and cosmonauts, there long durations in zero gravity, making there legs weak and a fast and useful process using low frequencies as helped in a big way…something we just don’t think about…

    There is a lot of science going on hears…some of us on this forum do this for lots of reasons…

    And placing a sub tower from SVS or making your own design based on there design or something totally different…

    I have been designing what I call the big wave…this will be custom made with one huge enclosure sealed and with one outlet splitting into two sections and placed at ceiling height near to the coving….

    Ashley….
     
  21. alexs2

    alexs2
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    The NASA technique would involve the use of loading the astronaut to a lightly vibrating plate with a harness.
    It should be noted that the research so far applies to rats,and the frequency used is 90Hz....not subsonic.
     
  22. Nimby

    Nimby
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  23. JBL 4645

    JBL 4645
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    Thanks alexs2

    That’s it that plate device…saw this working on tomorrows world a few years ago…what ever happen to the program…

    I wondering about that plate device…I have an idea I’ll keep it under my hay for a while guys like to do some research….

    by the way the image of the SR-71 black bird what is the or Original size of it looking for an image for my profile and a whole lot of them seem to exceed the size for image profile…can I take an image and reduce it’s size on my pc and then forward it to image profile

    Ashley…
     
  24. alexs2

    alexs2
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    Firstly,as I said,it used 90Hz,and not subsonics.

    As to avatars,you would need to refer to the forum rules regarding prior use,as I believe I have the option on that....you would therefore need to choose an alternative.

    Now....back to the original topic please...
     
  25. JBL 4645

    JBL 4645
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    alexs2

    What about all frequencies that can have a propose or a useful meaning ness…
    Which section should I post it on to start a new topic…?

    Ashley…
     
  26. alexs2

    alexs2
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    This is getting silly.....anything on that sort of trail I would suggest you put in general chat.
     
  27. micb3rd

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    Infrasonics an interesting subject.

    Firstly most regular subwoofers don't produce much output below 20hz, SVS's, Velo's, large DIY and IB installs can dig down into the mid teens.

    Some designs even use an extra low pass filter (also know as subsonic or rumble filter) to stop infrosonic frequnecys (20hz and below) getting through and incrasing cone excursion in frequnecys we can't hear.

    Most of the time with smaller cheaper subwoofer when you play tones in the 10-18hz region you hear motor noise from the driver cone moving and sometimes bass harmonics which are really smaller peaks in the upper bass.

    e.g. Play a 15hz tone and you subwoofer may be producing a smaller harmon ic at 30hz which is audible.

    Most subwoofers can't play infrasonic tones at loud enough SPL levels that will damage humans or do anything silly (well mabye the odd room rattle ;) ).
     
  28. Nimby

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    All valid points. Though a decent sub can make you very nauseous with little real output if you hit the right (or wrong) frequency. But this is much more likely using a signal generator on test rather than stepped tones or programe material. At least in my own experience.

    The main thing is not to worry about damaging yourself using a commercial domestic subwoofer. Things do fall off shelves and glass will rattle. So some care is indicated where ornaments are concerned. But death is much more likely to be fatal if you open up your active sub with the power still switched on. :nono:

    Nimby
     
  29. stonking

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    Well I have been trying out the THX optimiser tone sweep and that seems to work pretty well. (Its on most DVD's that have THX on the box). I would say that the space ships arriving on "Attack of the Clones" at the beginning sounds pretty good now. So I am happy with my set up for DVD's now but music I have not settled on a set up.
     
  30. eviljohn2

    eviljohn2
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    That's good news Stonking, setting your equipment up to produce loud explosions is one of the easier aspects though - tuning it so that your sub integrates well with music can be quite a bit more tricky but best of luck with it. :)
     

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