Per the audibility of loud very low frequencies - certainly you can hear them.
At one time I lived in California and experienced two prize earthquakes.
In an earthquake begun as a rapid shear, a front wave travels through hard at a very low frequency below the established limits of hearing. If you are close enough and indoors, that sound is for sure picked up by the eardrums. It is a pressure wave that pushes up the foundation. It, and the low frequency waves that follow, turns the walls and ceiling into (popping and cracking) diaphrams. You couldn't miss the deep sound. Truly awesome.
A wide bank of juiced 15" subwoofer cabinets could approximate the same indoors, and without rolling up the floor.
patch
At one time I lived in California and experienced two prize earthquakes.
In an earthquake begun as a rapid shear, a front wave travels through hard at a very low frequency below the established limits of hearing. If you are close enough and indoors, that sound is for sure picked up by the eardrums. It is a pressure wave that pushes up the foundation. It, and the low frequency waves that follow, turns the walls and ceiling into (popping and cracking) diaphrams. You couldn't miss the deep sound. Truly awesome.
A wide bank of juiced 15" subwoofer cabinets could approximate the same indoors, and without rolling up the floor.
patch
patch said:
...that's the key. Unfortunately.
In order to make such infrasonic signals really impressive you need unsaint volume displacement.... I always have the silly dream of a home theater with several 'sub walls' (something like 100 modular sub cubes with 12" or 15" high excursion drivers) and DSP phase shift control+filtering in order to overcome the room modes.
Did you ever knock on a rock sheet panel?
You can use granite, marble etc., but you have install a clever damping system inside the boxes in order to calm down the natural bell like ringing properties of these materials.
And why not installing an array?
My simple reasons: Money, size & available space, weight, time.
You can use granite, marble etc., but you have install a clever damping system inside the boxes in order to calm down the natural bell like ringing properties of these materials.
And why not installing an array?
My simple reasons: Money, size & available space, weight, time.
Having room walls made like the bass drum used in marching brass bands should work well. Certainly a practical choice anywhere. Here is a possibly...make a false wall extending a few inches out in that drum design...active or passive. The Foster corp is always looking for new vibrating-device designs, they have an open invitation to inventors, I bet they have this one on disk somewhere.
I'm guessing that a subwoofer designed like an air-powered hammer, driving a strong floor base or even earth below a room, would get the super-deep effect indoors. Something like those floor-installed subwoofers I'm sure we've all seen pics of - only in this case one would be using a raw shaker, content confined to percussion waves. I've been impressed at the low frequency power, at a distance, of earth-compators, the type used by construction crews. A sub designed along those lines and probably cheap, would turn friendly neighbors into enemies a half-mile around.
patch
I'm guessing that a subwoofer designed like an air-powered hammer, driving a strong floor base or even earth below a room, would get the super-deep effect indoors. Something like those floor-installed subwoofers I'm sure we've all seen pics of - only in this case one would be using a raw shaker, content confined to percussion waves. I've been impressed at the low frequency power, at a distance, of earth-compators, the type used by construction crews. A sub designed along those lines and probably cheap, would turn friendly neighbors into enemies a half-mile around.
patch
I recall seeing a review of the Wilson Audio "XS" subwoofer, which uses two 18" in a ported, 8' tall enclosure.
The reviewer made similar comments to what ScottG mentioned above about the acoustic signature of the room being "discovered" with the addition of the XS sub.
The reviewer also mentioned that he was trying this "XS" subwoofer in conjunction with the Wilson Wilson X-1, which uses both a Focal 15" and 12" drivers to reproduce the bass. Also, the X-1 is supposed to have "exceptional" bass.
The reviewer said that the XS opened up new windows of listening (my words) - even when using large drivers already.
The point I gleaned from the review is that it seems as though there will be incremental gains from going to more and more bass drivers until you reach a point of no improvement, which apparently might review a lot of Sd.
I don't know this for fact, I'm simply sharing what I've read in hopes this helps.
You might do a web search on Wilson XS sub.
The reviewer made similar comments to what ScottG mentioned above about the acoustic signature of the room being "discovered" with the addition of the XS sub.
The reviewer also mentioned that he was trying this "XS" subwoofer in conjunction with the Wilson Wilson X-1, which uses both a Focal 15" and 12" drivers to reproduce the bass. Also, the X-1 is supposed to have "exceptional" bass.
The reviewer said that the XS opened up new windows of listening (my words) - even when using large drivers already.
The point I gleaned from the review is that it seems as though there will be incremental gains from going to more and more bass drivers until you reach a point of no improvement, which apparently might review a lot of Sd.
I don't know this for fact, I'm simply sharing what I've read in hopes this helps.
You might do a web search on Wilson XS sub.
It looks like the Opal 4 home setup takes advantage of the ceiling bounce. In the right room, that can give a powerful bass, even with full-range speakers.
I experimented with high-mount speakers in a smallish rectangular room (approx. 10'w 15'l 8'h) used for critical listening. This was at a fine arts college some years ago, the school had standardized on the AR-2ax. I set them horizontally and flush with the ceiling, maybe a yard away from the side and front walls.
The bass was big and clean in that room, much better than I had with other placements of the same type ARs in identical rooms. With quality rock LPs it brought out the slam effect, as if we were using a really large speaker. Music majors studying on pipe organ liked that room.
I've since used full-range speakers set for ceiling bounce (in the home) with some success.
No its physics, there is a difference to making a noise and the perfect formation of a huge bass wave. This is the difference between experiencing live music in a large room and reproducing it at home. To me its all about natural and undistorted sound.
Its no secret that today most amps / audio sources have tiny distortion figures and that most of the distortion heard in hi fi comes from speakers, mainly in the bass range.
Personally I have found that mounting bass speakers flush in a solid wall sounds different (and more impressive) than a speaker in a box and that the concept behind this makes sense. The speaker is a piston, its job is to move air to create sound waves. With the air controled by the wall, the sound is different than when the sound waves are warped as they wrap around the box.
The same applies to adding wings to the sides of speakers. If the total width of the wings and speakers is 10ft, the quarter
wavelength of a 32hz note (aprox) you will hear a increase of both the quantity and quality of the sound.
Another factor I find interesting is the use of tubes for the shape of the sub bass. I find the slight upwards resonance far more natural and musical than the boxy sound.
The nice thing about diy is that there are so many things to try!
The use of a bass speaker at the top and bottom is actually more for looks than theory. John LENARD Bernett prefers the woofers to be mounted together, but as most of the opal range involve each componant with its own box, its up to the owner how they want it to look! His grand daddy 28" woofer system as featured on the website and recently on the cover of australian hi fi, was customed designed for a very rich organ music lover, -3db down at 16hz and absolutely no bass refex port. The picture implies corner loading.
I have no doubt that ceiling bounce can create a impressive bass!
Tell me if I'm wrong.
Seems to me, we should only attempt to recreate the sound in proportion to the room and the size of the screen. In other words, we can't (and don't want to) reproduce the sound of a bomb exploding 20 feet away from the camera. We may never hear anything again! So with HT we would want to keep the sound relative to the size of the picture. Anything more would take away from the presentation, in my opinion.
With music we would want to keep the sound relative to the stage and image of the speakers. This is why I like to listen to small jazz combos often. You can actually "re-create" the performance as it were in your room.
JMHO
Seems to me, we should only attempt to recreate the sound in proportion to the room and the size of the screen. In other words, we can't (and don't want to) reproduce the sound of a bomb exploding 20 feet away from the camera. We may never hear anything again! So with HT we would want to keep the sound relative to the size of the picture. Anything more would take away from the presentation, in my opinion.
With music we would want to keep the sound relative to the stage and image of the speakers. This is why I like to listen to small jazz combos often. You can actually "re-create" the performance as it were in your room.
JMHO
Rob,
Please realize that I am not being argumentative when I ask the questions below. I know hardly anything about commercial HT. The pic at the bottom is my version of HT. It's all DIY. I could easily go 5.1 but, see no point in it in a 14x14 room.
OK?
How is this reference made? Who determines the level? Does it allow for size of room? Size of screen?
Sorry if these seem like really stupid questions. I watch movies with no bass or treble boost and volume is set usually so that you hear normal conversation (on the movie) comfortably.
My 72" DIY projection set up.
Please realize that I am not being argumentative when I ask the questions below. I know hardly anything about commercial HT. The pic at the bottom is my version of HT. It's all DIY. I could easily go 5.1 but, see no point in it in a 14x14 room.
OK?
How is this reference made? Who determines the level? Does it allow for size of room? Size of screen?
Sorry if these seem like really stupid questions. I watch movies with no bass or treble boost and volume is set usually so that you hear normal conversation (on the movie) comfortably.
My 72" DIY projection set up.
Attachments
The quick answer is the industry decided. Home theater amps / processors all have a calibration feature where it plays each channel in turn, and you use a spl meter to calibrate. At listening positon the spl meter will measure 75dB (sometimes 85dB depending on make / model). When done you set the volume to what it was at calibration and that is reference level.
Due to the level being set at listening that accounts for room size.
I should state that reference is 85dB per channel, though some argue that it should be 75dB for home listening. Depends on what source you look at. I set mine at 85dB per channel, and generally watch films between reference and - 5dB.
I use Avia dvd to calibrate my system (I also have digital video essentials to check DTS)
Screen size is unimportant as far as the audio side of things go. Your setup looks great and in no way needs the sound turned down as far as I can see.
BTW I don't use a centre channel either as I just don't have the space right now. If I had the space I'd definitely use one. (my room is 20 x 10)
Rob.
Due to the level being set at listening that accounts for room size.
I should state that reference is 85dB per channel, though some argue that it should be 75dB for home listening. Depends on what source you look at. I set mine at 85dB per channel, and generally watch films between reference and - 5dB.
I use Avia dvd to calibrate my system (I also have digital video essentials to check DTS)
Screen size is unimportant as far as the audio side of things go. Your setup looks great and in no way needs the sound turned down as far as I can see.
BTW I don't use a centre channel either as I just don't have the space right now. If I had the space I'd definitely use one. (my room is 20 x 10)
Rob.
SMPTE set the standards, THX raises the standards.
Films are mixed for cinemas, cinemas are set up to a reference level, the dial on the dolby processor is set 7 for a 85db playback level through eq, which allows a wide dynamic range.
DVDs are almost identical to the film versions
Size of screen is only a recomendation, but smpte suggest that the ideal seats are between 2 to 5 x the image hight away from the screen.
I guess I'll give up trying to explaining the concept of the plain wave front, the basis of the thx baffle wall, which seems to be found in most cinema mixing suites, which strangely uses a minimum of 3 layers of gyprock and a steel frame as big as the screen, to mount the speaker boxes in. The lenard k4 horn loaded cinema system also states to aim for this ideal.
These concepts seem to have been around a lot longer than home computers. The use of wings in pa was pioneered by Altec lansing in the 1940's