No sound @ 25Hz

[leif]

An audiophile man passed by the other day. He brought test sample records and stuff. Among the things he tested out, was a 25Hz signal on my stereo.
I was very surprised: The woofer on my sub was really moving, but there were no sound at all. I did not hear anything. He did not hear anything.
Shouldn`t a B460 (2245H) make sound at 25Hz?

Leif

[HipoFutura]

Is is possible your hearing isn't what it used to be? LF & HF are very difficult to hear as you age. Your question makes me wonder! When I have time I'll hook up my signal generator and see where my hearing cuts out.

Don

[Zilch]

http://en.wikipedia.org/wiki/Infrasound

If it shows on your RTA or SPL meter, the B460 is making it.

Surprising what a test disk or signal generator will reveal about hype....

[Anthony L100]

An audiophile man passed by the other day. He brought test sample records and stuff. Among the things he tested out, was a 25Hz signal on my stereo.
I was very surprised: The woofer on my sub was really moving, but there were no sound at all. I did not hear anything. He did not hear anything.
Shouldn`t a B460 (2245H) make sound at 25Hz?

Leif

Same deal here Leif, 30Hz I can just about hear, 20Hz I can only feel:D, yes, a lot of hype. Can anyone confirm HipoFutura's comment about LF hearing diminishing with age? I am very aware my HF isn't as good as it used to be, but not too sure about LF.

[BMWCCA]

I always figured almost anything below 50Hz you just feel anyway. Did stuff fall off your shelves and cracks form in the plaster while you heard nothing?

[leif]

I went to an ear specialist a while ago, and got my ears tested. My hearing was exellent. But I guess he did not test as deep as that.
But still, 25Hz should be hearable, shouldn`t it?
The man visiting me have quite a impressing gear himself. Unfortunately nothing from JBL. But take a look anyway: http://avforum.no/minhjemmekino/show.php/Flageborg

[Robh3606]

Well guess it depends on the levels you are getting. Do you have a subsonic filter inline?? I do test sweeps from 150Hz down to 20Hz and right about 23Hz is when I can't hear it in my room. I can see it on the RTA but can't hear it.

Rob:)

[leif]

I always figured almost anything below 50Hz you just feel anyway. Did stuff fall off your shelves and cracks form in the plaster while you heard nothing?

Nothing was shaking, nothing sounded, and I could not feel anything on my body. But it was obvious that the woofer was working hard. That could be seen.

[Robh3606]

What about on a different floor of the house?? Could be a room mode. Is there a pair? The only time I have experienced that was with out of phase bass drivers. Is the phase OK with the mains, if the mains have any output that low??

Rob:)

[mbd7]

When I ran a 25 Hz tone thru my 4343's I heard a whistling sound from one of them. When I investigated its source I discovered that one of the screws on the back was missing and the whistling sound was generated by all the air moving through such a small hole!

[Ducatista47]

What about the size of the room? If the diagonal of the room is less than half the wavelength (I think), the wave will not propagate. Air being pushed around, but no sound. My room, for instance, cuts off at 23hz.

Here is a very cool tool from the Harmon website:
http://www.harman.com/about_harman/technology_leadership.aspx
Click on White Papers > Calculators > Room Mode Calculator Read

It is a tiny tool, 128 kb, but it requires Excel.

Clark in Peoria

[scott fitlin]

Below 30hz, the sound becomes very inaudible. I have run test tones through my system, and 30hz I hear plenty, 28hz still quite audible, at 25hz, I feel air moving but dont hear much, very faint sound. At 20hz, you can feel the rumbling, and hear the room vibrating, but I cant hear anything audible from the speakers.

At a recone shop, they once showed me how they run test sweeps through a woofer, checking for rattles, and centering of the VC, he ran sine wave test tone through JBL woofer, a 2226H, 40hz was really loud, 30hz was audible but considerably lower in volume, 20hz was completely inaudible and the cone was moving alot. Then he ran a 10hz test tone through the woofer, totally inaudible, BUT, the JBL 2226H made no rattling noises, and the cone moved more than I have ever seen any woofer cone move, ever. That it could take this and not make any noise in protest was quite impressive.

[Rolf]

Nothing was shaking, nothing sounded, and I could not feel anything on my body. But it was obvious that the woofer was working hard. That could be seen.

Hi. Do you have a floor/walls made of wood or concrete? If it is made of wood, something should be moving and making sound(s).

Also remember that almost no woofer is capable of reproducing much under 30Hz. At 25Hz most woofers is down 10db or more. The room also have a limit of how deep the sounds is possible to hear.

There is also possible to figure out how much a e.g. 15" woofer must move to reproduce a 25Hz tone on a certain level compared to the same level at 40Hz. If you do this you will probably understand why there is so few (if any) woofers actually do it.

[leif]

My room has wood floor and it is hard to describe the shape of it. It is a rather large room.
I changed the position of the sub just now, and put it in a corner. standing uprised next to one of the 4430`s. It looked really cool standing uprised. Picture coming soon.
I put on Yello`s The Eye, track 5. A cool song to test bass. When playing really loud, the floor is shaking very much. And I guess that can be the reason for lack of physical punch. But guess what I saw while playing? The woofer was working hard, but it had cracked in the foam. I did not see that the other day when that guy was here, so I guess it happened now. Arghhhh....
Well, the speaker is old, and I have been waiting for it to happen. Phuhh.....
That one is NOT cheap to recone.
Perhaps I slould try to refoam? I did it with the 4430`s and it worked fine.


Leif

[SEAWOLF97]

Also remember that almost no woofer is capable of reproducing much under 30Hz. At 25Hz most woofers is down 10db or more. If you do this you will probably understand why there is so few (if any) woofers actually do it.

I have a pair of AR3's . rated at doing mid 20's. On some audio material, I can feel , but not hear the bass. Could never really verify what they can do. Ugly looking, looks like they've been buried (they all look that way), but put signal to them and.......

[Rolf]

I have a pair of AR3's . rated at doing mid 20's. On some audio material, I can feel , but not hear the bass. Could never really verify what they can do. Ugly looking, looks like they've been buried (they all look that way), but put signal to them and.......

I had a pair of AR3A Improved myself in the mid 70's, but they did not do any better job than the 4333/4343 in the very low frq. Nice speaker tho.

Yes you can hear/feel frq. under 30Hz. I have tested my 4343's, and I can feel as low as 16Hz, but testing is one thing.

Music has a lot of energy normally from about 50Hz and up. At 50Hz a speaker needs a certain amount of power to reproduce it at a given SPL. Because the speaker is down a lot of db at e.g. 25Hz the SPL will be much lower, and you will probably not notice the 25Hz.

If a woofer is to reproduce 25Hz as loud as 50Hz it will have t move a lot (more than most woofers can) and it will take huge amount of power.

Anybody else with more knowledge than me want to step in?

[whizzer]

I remember seeing a chart somewhere that illustrated the degree by which frequencies must be increased in amplitude to "sound" as loud as higher frequencies as a result of the increasing insensitivity of the human ear to lower frequencies. It's one of those "psycho-acoustic" effects. While a dB meter might register a 40 Hz tone at, for example, 100 dB at a meter from the loudspeaker producing the sound, it will not "sound" as loud as a 200 Hz tone played through the same loudspeaker at a measured 100 dB level. The degree of perceived difference increases as the frequency decreases. I believe the fundamental frequency of the brass "Napoleons" used in authentic renditions of the 1812 Overture, for example, is 6 Hz. Most loudspeakers cannot produce such a frequency at all, let alone at a volume level approaching that of an actual cannon firing, yet even if a given subwoofer even triples the frequency, the 18Hz "underpinning" provides a visceral impact altogether lacking in loudspeakers incapable of providing much response below 40 Hz--oh--it will sound loud and give the ear the "idea" of a cannon shot, but it's not like being there, which is not an altogether bad thing in an enclosed space. Gun handlers would emerge from the CSS Virginia (widely known as the Merrimack) with blood running from their ears, an effect I'm not all that eager to reproduce in my living room....

[Steve Schell]

Leif, several things could be at work here. Your cabinet could be tuned higher than 25Hz., and the system response could be quite a few decibels down by 25Hz. A sealed box system rolls off at 12dB per octave below resonance, and a bass reflex system unloads even faster (I think) below resonance. Even a mighty 2245H can't move much air when it is unloaded, though the excursions may be large as it flails back and forth. It is not good to apply signal below resonance, as the driver can be damaged by the wild swings.

A horn can provide the best load by far to the driver, but the size becomes huge if designed for 25Hz. or lower loading. The horn subwoofers I have built have a 15Hz. exponential flare, and a single 15" driver will produce over 100dB at 20Hz. with a one watt input. The downside is of course the box size, over 100 cubic feet.

As has been pointed out, the reflections in a small room can harm the low frequency response. A 25Hz. wavelength is 44' long, so it needs some space to develop. A room with somewhat flexible walls can actually help here, as the long wavelengths pass through them rather than being reflected back into the space.

Whizzer correctly points out that our hearing is very insensitive to low frequencies at low levels, as can be seen in the Fletcher Munson curves:

http://en.wikipedia.org/wiki/Fletcher%E2%80%93Munson_curves

Speaker engineer Tom Danley recently made an outdoor recording of July 4th fireworks. It contains phenomenal low frequency information, and may give you a better indication of how well your sub is working. This one is best played at low levels the first time through, while watching for excessive woofer excursions. He has made this recording available as a free .wav file download here:

http://www.danleysoundlabs.com/knowledge%20baSE.htm

The recording was discussed on a thread on the Audio Asylum:

http://www.audioasylum.com/scripts/t.pl?f=hug&m=110920

Last night my friend Rich brought over a burned CD of the recording. I posted my comments to the Asylum here:

http://www.audioasylum.com/forums/HUG/messages/112216.html

P.S. I just reread your post, where you mentioned that your sub is a B460. It's been a while since I read the Timbers/Kramer article, but I would think that your driver should be well loaded by the enclosure at 25Hz.

[mrbluster]

B460 Cabinet is tuned to 26Hz with boost from the BX63 centered at same 26 Hz...... falling 12db per octave above and below.

[moldyoldy]

The low note on a fullsize piano is 27.5Hz.