No sound @ 25Hz

[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/Fletche...3Munson_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/HU...es/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.