Test Tones

[stonking]

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?

[Crustyloafer]

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.

[eviljohn2]

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.

[Ian J]

Did you buy the Velodyne in the end ?

[stonking]

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.

[bob1]

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?

[stonking]

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?

[eviljohn2]

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

[Nimby]

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

[stonking]

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.

[eviljohn2]

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!

[Mroizouk]

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.

[JBL 4645]

And if you can hear 15Hz which doubt very much…you are feeling it…infersSonics can be, 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….

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

[Mroizouk]

Originally Posted by JBL 4645

And if you can hear 15Hz which doubt very much…you are feeling it…infersSonics can be, 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….

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

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?

[JBL 4645]

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…