If One Sub is Good, Are Two Better? - Page 3

Actually, they cannot. What is being localized are the mechanical artifacts associated with the sub's moving that air which are at higher frequencies.

I have wondered what would happen should anwaypasible and HiFiFun ever meet within the same thread.

Turns out pretty much what I expected.

FWIW I agree with you: But
when you factor in someone as knowledgeable as Dennis Erskine on this stuff all bets are off

I think you are mixing up a few different ideas here:

1. First, if you are talking about bass in the 60 hz. plus range then I certainly would agree that either two or five sources are best. In this sense I do agreee with the notion of stereo bass.
2. Second, if you are talking about low bass, then directionality is preposterous and a single channel (even if reproduced by at multiple point in the room) will suffice.
3. Third, setting speakers to 'small' can work really well, but you have to be clear about what frequency the cutoff is set for. I'd agree that a higher crossover point is not the way to go, but this is often dictated by the limitations of the speaker. Setting a much lower crossover point can work really well, and this is in fact what I do (set at 30 hz.).
4. Running 'full range with sub' can work - i did this for many years - however, depending upon how high of a frequency the sub is asked to reproduce can add thickness to the sound.

+1 I agree.

see...
this is one of those situations where both can be true.
depends on the setup.

i think what was said above is, the subwoofer's reverb is reflecting off of a surface louder than what can be heard directly from the speaker cone.
i've done this myself with creative's reverb.
the front speakers output was louder off of the rear wall than from the speakers actually in front of me.
when such an instance is true and right there in front of you, the only chance of finding the source is to listen for the mechanical noise of the cone moving in and out.
not always a noise that exists, and even when it does exist.. the noise can be manipulated (or anchored) away by reflections.
if the mechanical noise accumulates in a corner stronger than from the cone, its a dumb guess.
you'd say to yourself 'do i pick the loud location or the soft location?'
either one is hope and could be wrong.

however, longer seperation between reflection and source can change things.
the mechanical noise could be clearer to reveal the source.. or the source could be dirty, and the accumulated reflection sounds cleaner.

i'd say its a bar joke highly dependent on design and instance.

without using the reflections to your advantage, its quite easy to tell where the source is.
sometimes you stand in a position of the room and the sound is equal from all directions, no point trying.
but walking in some direction could reveal amplitude or time domain.

i'd say there are more setups that reveal the source, compared to systems that have made an effort to hide the source.

No. Unless you have a giant head with ears six feet apart, you cannot localize a 20Hz wave (which has a ~56-foot wavelength), regardless of reflections. Even magical reflections that somehow are louder than the source (your second instance of creating energy in this thread alone!).

As Dennis illustrates, the only hope of localizing the source of low frequency waves is via the localization of other higher frequency artifacts.

I can buy that two or more subs have some benefits but what I don't buy is why each needs independent (not summed) EQ. All that matters is the aggregate frequency response at the ear (or test mic).

Think of it this way. Hypothetically, say magically you had three subs, doing a limited range each, with the following in room, ruler flat FR, measured at the ear:

A) 1Hz - 20Hz , and almost completely dead outside this bandpass range
B) 20Hz -40Hz , and almost completely dead outside this bandpass range
C) 40Hz - 80Hz , and almost completely dead outside this bandpass range

Looking at any one sub individually, not knowing about the others, one would say it had a horrible, limited bandpass response and was in desperate need of EQ to fix it (if even possible), right?, yet to the ear (or the test mic) all that matters is that the monophonic sum of the three is a nearly perfect, ruler flat 1Hz - 80Hz.

My point is I don't see the need to EQ subs independently. I think a mono sub EQ addressing the aggregate output only, should suffice.

Can anyone point me to a link, not written by multi sub EQ product maker, that disproves me? Thanks.

you dont have the decency to give which setup you are speaking of, and you are simply being rude by saying 'no' without such example.

people fail to see the walls that are inevitable of a room.
if you are outside and the wave comes across you, then you would have to walk the entire length of the wave to determine where the middle is.. then you could simply point straight ahead to know the source.

when the walls are in place, those waves will hit the wall.
doesnt matter if the walls are 56ft apart or not, they still continue to move forward.
without any attempt of reverb, its very easy to use the walls.. unless those walls are in specific locations to purposefully anchor the sound and create an illusion.

you are holding an arguement of uniformity and whether that soundwave has been purposefully shaped to be uniform hasnt been answered.
i feel that is you bringing nonsensical energy to the thread.

it could be said, any area of air that doesnt contain the bass frequency is thus an area of higher frequency artifact.

thats not gonna happen if the subwoofers are in a box built to be ruler flat in the space they are ment to energize.
the only thing left to say is the imagining of the three subwoofers.
if they are in the same place, no individual EQ would be necessary.
but if the locations are different, simple time delay might not be enough if/when the reverb hasnt been calibrated (or the walls havent been designed to create an illusioned path.)

its about the direct wave, and if that wave makes it to your ears.. or if the reflections have been considered and precisely directed.

ya'll are walking along a path of labyrinth possibilities.

Anwaypasible, that was hilarious!!

Now I get this thread - it's about being ludicrous. I'll just sit back and enjoy the show.

That's what I'm doing.

i shall give you a break, as i have been victimized of the same casual view.
soundwaves outside in the open air are extremely specific to the discussion of 'being able to point out the source'
and it should be said again, when you are outside with no reflections.. you have to walk the entire length of the sound to determine the middle.
if you are anywhere inbetween the edges of the wave, you wouldnt know if the source was directly in front of you or to either side.

anybody can use water for an example.
when a rock drops into the water, the wave spreads out with even magnitude.
there is no point in the wave that has higher energy.. the entire circle is raised equally.
and that means you cant expect the soundwave to have different amounts of energy as you walk along the path of the wave.
when you get to the edge of the wave, you will clearly notice the wave has stopped.
and if you find yourself walking in a complete circle.. then you know the source was omnidirectional.
a 'u' shape would indicate a directional source.
and the smaller the 'u' shape.. the sharper the bend of the speaker cone.

Thank you for giving me and the other readers a break by sparing us from facts, ignoring both interaural time/phase differences and interaural level/pressure differences, the two mechanisms by which the rest of us humans with two working ears localize sounds. This "walking the length of the wave" method seems much more interesting.

And now, back to the show!

Isn't this thread about single versus multiple subs?

i felt that i should have said something about the ground causing a reflection.
talking about interaural has only made the desire stronger.
if the was flat, the relfections would be violent towards the edge of the wave.

getting the wave to sound equal, both in front of you and behind you, is interesting.
you would have to have some sound processing that focused emphasis on the wave ripples hitting the ground.
because then, you would have a very long walk forward/backwards to determine if the amplitude was getting stronger or lesser.

simply standing there and spinning your ears around.. without any wind, the sound would be 360 degrees.
a stupid guess to move in any direction.

whatever the audio processing effect is called.. its worthwhile when it can hide the presence of source by pushing forward from all directions as the wave ripple travels across the earth.
without it, you could hear a rise and fall.. then take a couple steps backwards to stay in the rise or fall of the ripple.
if you walk backwards and the ripple holds, there is a source in front of you.
walking sideways (with a slight curve) means you will expect to hear the ripple with the same time domain (unless your curve was off).

no audio processing = as simple as a fan blowing in one direction.
the wind pushes you back = move forward for the source. (but you may find yourself approaching a reflection)
see.. the ripple hitting the ground will confuse you, but there is still a ripple that is direct and blows normally.
just gotta decipher between the two.

Awesome!

Don't forget to talk about "interaural"!

yeah.. you could change the phase somewhere in the mixing of the ripple hitting the ground and the direct pulse that doesnt hit the ground.

if you change the phase, you can literally reverse the 'pushing' of the direct ripple.
when you manage to create a vacuum suction in front of you, that clearly means there will be a 'push' from behind you.
and that 'push' is enough to trick you into walking the wrong direction.
you wont know you've gone the wrong direction until the amplitude of everything has grown weak.

i think its fantastic talk.. because the military can setup giant speakers to scare the pants off of unwanted visitors.
not only does it seem scary.. it also provides confusion, so if they were simply being curious and wanted to have a look at something.. their curiousity could be tricked by reversing the polarity of the soundwave AND use reflections to trick their curiousity to walking toward some place of little importance.
if they had guards there ready to arrest somebody for being on a 'no trespassing' zone.. those people would be removed before they ever got close enough to see a 'secret'

Well then he should explain himself instead of just saying "um, no that isn't correct"

Every time someone says the world is flat, I am not going to explain why I disagree with that view. Anwaypasible is so far out in left field and clearly has no basic understanding of small room acoustics (nor apparently, basic Physics, I'm not even going to start a course at the Pre-K level).

So, for you, here's your reading assignments, and then, once your homework is done, we can start.

http://www.aes.org/tmpFiles/elib/20110417/13686.pdf
http://www.aes.org/tmpFiles/elib/20110417/12206.pdf
http://www.aes.org/tmpFiles/elib/20110417/6079.pdf
http://www.aes.org/tmpFiles/elib/20110417/6104.pdf
http://www.aes.org/tmpFiles/elib/20110417/13680.pdf
http://www.harman.com/EN-US/OurCompa...s/multsubs.pdf
http://www.harman.com/EN-US/OurCompa...ndRoomsPt3.pdf

Exactly what we use over here Dennis HAA calibrators.

Thankyou

I would encourage any "enthusiast" to take the HAA Level I class. Good stuff.
www.homeacoustics.net

I'd love too but it's on the other side of the country and with work commitment becomes too hard. So I had to hire one a few years ago. It's amazing how important the room is, I used to think equipment first but I was wrong with that assumption.

I agree with you, spend the money on one high quality subwoofer. I prefer nice tight, clean bass over loud rumble any day. Nothing kills music/soundtrack more than over emphasized muddy bass.

If you measure the response from a single sub from your listening position, it will give you a response curve that is far from flat. If you measure from a second listening position, you will get a different response, again far from flat.

Multiple subs aren't (necessarily) about adding more bass, it's about smoothing that response, so that a 20 Hz tone is as loud as a 32 Hz tone, etc, etc, and do so for multiple listening positions.

Properly setting up multiple subs will give you a cleaner, more natural sound in various locations in your listening room because they will be able to give you a much flatter, more uniform response. It should not be muddy nor overemphasized. If so, it's been done wrong.

[edit]

The Welti papers that Dennis has provided above deal primarily with the usage of multiple subs with respect to equalizing levels from seat to seat. Dr. Toole's earlier work at Canada's NRC is also demonstrative of the value of multiple subs when properly positioned.

There has been mention of running all speakers full range. Years ago I did just that. Having 5 identical speakers and 6 subs. The AVR had all channels set to large, with each channel having its own sub. Each of those subs were placed below their respective 3-way tower (24" tall). The sixth sub was connected to the sub out, via coax, and set to LFE only.

The sound was amazing, to say the least.

I thought the banking and mortgage industry had that routine down pat.

sometimes a second sub is for a different portion of the frequency response.
other times a second sub is to fill a different area of the listening room.
and if you are on a budget, two weaker subs can reinforce eachother (and that was the pleasure i was talking about)

the reflections on the walls (or from the walls) need care and attention.

Please stop using water wave terminology, and I'M not an audio expert, but have been boating many years, and the reflected wave is important; it can make the water rougher than the prevailing wind would normally indicate. I assume this applies to audio waves.

Anyway, please keep the discussion going. I am debating a 2nd sub.....

RickMid

He just moved to the bleacher nose bleed seats.