Are we talking about low freqs?, like below 200hz? Gedlee says nothing about using tbe futton for low freq. he actualy says at low freqs you have to consider all the surfaces because its the modal range and its all about standing waves. Why dont you ask him? How you extrapolate his futton on the floor to low freq. reflections is hard to swallow. And I didnt even read the second one because the title says its above 200hz.
A standing wave is a steady state description that simplifies the acoustic phenomenon. I do agree that below -say- 200Hz the importance of single reflections isn’t that big in auditory perception. But it’s not that they are not there. In as far as you could define the time-place-pressure variations close to a boundary as a ‘reflection’, you could also call it a ‘standing wave’
I didnt make up the definitions, this is all standard acoustics. A reflection is not the same as a standing wave, look it up.
If your measuring low freqs. than you need low freqs, and these cause standing waves. Chirps have none so how does that work? You should read a book about room acoustics.
What is wave like behavior? There are traveling waves and standing waves, which one has wave like behavior? No, Ive never heard double bass arrays in a 15' by 20' room.
Dig somewhat deeper into acoustics. If you grasp the wave equation get back here.
"I'd also caution talking about woofers in the modal region as if they are in free space (i.e. directivity, 1/2 space loading, etc.) In the modal region the woofers see ALL of the walls, not just the nearby ones. That makes the problem much more complex to consider and simple thought experiments are usually not very accurate."
What that means is its just as efective to reduce low freq. "floor bounce" with a cieling absorber, or back wall absorber as a floor absorber, in other words its not a "bounce" (reflection) its a mode. And simple thought experiments, like yours, are usually not very acurate.
What that means is its just as efective to reduce low freq. "floor bounce" with a cieling absorber, or back wall absorber as a floor absorber, in other words its not a "bounce" (reflection) its a mode. And simple thought experiments, like yours, are usually not very acurate.
Standing waves happen at what we call “modes ”
Reflections can cause modes...anytime we are dealing with multiple signal paths, a mode could occur, somewhere...a mode is a standing wave; when two sounds traveling in opposite direction...propagate...which results in either a null or peak...
This can happen at any frequency in any room or without a room, only two signal paths are needed for the possibility...standing wave equates to resonate notes and cancellations of various magnitudes and compliance....the harmonic aspects I don’t know 100% other than there will be main “notes” attached to specific sources of standing wave and a repeat but less sever standing wave at the harmonic locations derived from the dominate standing wave
No multiple signal...no modes
No reflections in a room (room eats them magically with acoustic treatment from aliens)
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No multiple redundant sources = no standing waves
Due to room reflections and multi redundant sources within crossover band, or multiple channels covering the same spectrum...we have standing waves.
Reflections can cause modes...anytime we are dealing with multiple signal paths, a mode could occur, somewhere...a mode is a standing wave; when two sounds traveling in opposite direction...propagate...which results in either a null or peak...
This can happen at any frequency in any room or without a room, only two signal paths are needed for the possibility...standing wave equates to resonate notes and cancellations of various magnitudes and compliance....the harmonic aspects I don’t know 100% other than there will be main “notes” attached to specific sources of standing wave and a repeat but less sever standing wave at the harmonic locations derived from the dominate standing wave
No multiple signal...no modes
No reflections in a room (room eats them magically with acoustic treatment from aliens)
+
No multiple redundant sources = no standing waves
Due to room reflections and multi redundant sources within crossover band, or multiple channels covering the same spectrum...we have standing waves.
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So your saying standing waves are the same as traveling waves? And room acoustics dont cahge at low freqs? I did the wave equations years ago in EE. Can you show me how you use it for low freqs in a room?
Wow. All you need is one source playing a single freq in a ("small") room to get standing waves. Do just make this stuff up?
Where did you get that impression? I did not even state that from sound pressure variations in a point of space you cannot derive the wave pattern. Which I could have done.
The other way around though, presuming reflections from boundaries, can bring you standing waves. There the wave equation comes in. Standing waves are solutions of that equation when regarding multiple sources (yes, kinda reflections from boundaries also) in a physically defined space with its boundaries. But if you are really into wave equations, read Beranek.
OK, I don't know where those specific dimensions came from, but anyway, in a DBA you have (in theory) complete cancellation of room modes by destructive interference of the sound coming from the source (front) array. That is accomplished by having the signal delayed by the distance of the room depth, and inverted in phase. This works even below the Schroeder frequency and in fact is especially effective as the frequency goes down.
If you can understand that, why can't you understand that a floor bounce can exist at low frequencies?
DBA’s to me are a specific solution of the multisub approach. You’d have to apply it in more than one dimension. IIRC DBA’s ideally have floor-to-ceiling cabinets with line array bass speakers. That, with the stereo setup and the phase-shifted back speakers, resembles a multisub approach in two dimensions. The setup brings the possibility of a sound field that could be compared to a traveling wave in a tube.
I for myself think the ‘traditional’ multisub approach brings you the same, with less effort. But hey, that’s just me.
I for myself think the ‘traditional’ multisub approach brings you the same, with less effort. But hey, that’s just me.
I'm only using it as an example to show that sound still exhibits "traveling" wave behavior even at very low frequencies. Which means, of course, that a floor bounce can still effect interference at listening position.
I agree with you that the arrays needs to be two-dimensional, with a minimum element density, but it's been shown before that even 2x2 arrays on each wall can give excellent results below ~80 Hz (IIRC). Of course, as the density goes up, the effective frequency range goes up as well.
EDIT: I think this was the resource I was referring to: Double Bass Array (DBA) - The modern bass concept! | AVS Forum
I agree with you that the arrays needs to be two-dimensional, with a minimum element density, but it's been shown before that even 2x2 arrays on each wall can give excellent results below ~80 Hz (IIRC). Of course, as the density goes up, the effective frequency range goes up as well.
EDIT: I think this was the resource I was referring to: Double Bass Array (DBA) - The modern bass concept! | AVS Forum
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The dimensions are proportional to the Schroeder freq. For concert halls its usually below 20hz so room modes don't apply. We are talking about residential rooms. I don't deny energy bouncing of the floor at low freqs, I have a problem when people think its the same as high freq reflections, and the solutions are the same. Neither is true. Thinking a futton on the floor between you and the speakers will cure this low freq "bounce" is wrong, you can't think of the sound as a ray that only gets to you in straight lines. The low freqs "bounce" off all of every wall before reaching you. So a futton on the ceiling would have just as much effect, not much. Your absorbing 20sq feet of 1600sq feet of bounce.
And I also agree that the multi sub solution is best.
"Floor bounce" refers specifically to the sound bouncing off the floor in the same vertical plane as the speaker and listener, which is usually the first (earliest), and almost always strongest, non-direct source. If you had a gaping hole in the floor that prevented this reflection from occurring, you would absolutely prevent the measurable null (and progressively weaker comb filtering) that happens in bass or mid-bass from it.
Sure, maybe a futon is not going to fully absorb the floor bounce, but it sure as heck is the right idea. None of the other room reflections are going to cause the floor bounce null. That's why it's specifically referred to as "floor bounce".
Do you want to explain why the math behind this is wrong: Floor/Ceiling Reflection Calculator
Sure, maybe a futon is not going to fully absorb the floor bounce, but it sure as heck is the right idea. None of the other room reflections are going to cause the floor bounce null. That's why it's specifically referred to as "floor bounce".
Do you want to explain why the math behind this is wrong: Floor/Ceiling Reflection Calculator
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You’ve modified your argument to where I no longer disagree. However, that was not your original claim:
And to answer your question in regards to *which frequencies*:
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