so true! If you drag this out as 3 on 1 compounded and drive it from each end at 1/3 and 1/9… you’re golden to whatever area the acoustical shape can’t help ? This straight off our very own time domain and planet. The secret is in a 33 x 33cm x33cm (think 33/7) cube that fits a sphere in it from the start at each end as 0.5236:1 including the exit ‘end ‘. ?Man, you should use that paper for isometric drawings ONLY!
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With typical iir EQ you can't this is true.
But with time domain manipulation you can now solve some issues ( but not all):
Audiolense Digital Loudspeaker and Room Correction Software Walkthrough - CA Academy - Audiophile Style
But with time domain manipulation you can now solve some issues ( but not all):
Audiolense Digital Loudspeaker and Room Correction Software Walkthrough - CA Academy - Audiophile Style
I referred to the echo as the phenomenon of the traveling wave in 3D. Not as the SPL sum at the original source. Good luck with FIR on that one.
This has been researched. Up to a room with all walls covered with loudspeakers. Cannot recall that now, but it might have been supported by Harman or Philips quite a while ago at the time when dsp became available.
We must all agree that a multichannel approach is best for good sound reproduction in small to medium rooms. Not only for low frequencies.
Mark sorry but i don't get your comment.
Have you read the link i gave? Mitchba performed a fir correction to compensate for what he call a low freq early reflection ( his loudspeakers are off wrt the optimal symmetric layout of loudspeakers within the room we target for stereo set up).
In this paper he do not give evidence of the efficiency over a relatively large area but in his ebook he gives measurements prooving the efficiency over a couch area.
For me it is a 3d issue and correction is efficient over a much wider area than what theory predict.
That said i didn't say it is a cure for all or that multisub approach isn't appropriate, i think it is quite the opposite in fact, but there is now other way to approach this too.
Have you read the link i gave? Mitchba performed a fir correction to compensate for what he call a low freq early reflection ( his loudspeakers are off wrt the optimal symmetric layout of loudspeakers within the room we target for stereo set up).
In this paper he do not give evidence of the efficiency over a relatively large area but in his ebook he gives measurements prooving the efficiency over a couch area.
For me it is a 3d issue and correction is efficient over a much wider area than what theory predict.
That said i didn't say it is a cure for all or that multisub approach isn't appropriate, i think it is quite the opposite in fact, but there is now other way to approach this too.
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Yep, thx for the link.
I’m aware of the possibilities to correct sound fields at given points in space. Any noise cancelling headphone does so and does a pretty good job. And since a given room has it’s proporties, correcting the reflections and modal discontinuities with (what one could call ‘antisound’) some kind of feedforward signal processing can do pretty well. I recall car manufacturers that have done research on this to get in-cabin engine, wind an tyre sound levels down, it wouldn’t surprise me to find that Boeing and Airbus have done the same.
Bottom line (for me, while I’m no HT expert at all) is that multichannel approach is best for masking (and partially damping) reflected sound (including modal behavior) in a small room. I bet no one could argue with that, the research on it is quite extensive and ‘theories haven’t been falsified’ to my knowledge. And in that sense I’m not totally convinced by the need for elaborate signal processing at one given point in space, the cost to get that right competes with the cost of a reasonable multichannel setup. Nothing stands in the way of combining both approaches btw. But we are drifting off topic (sorry TS).
I’m aware of the possibilities to correct sound fields at given points in space. Any noise cancelling headphone does so and does a pretty good job. And since a given room has it’s proporties, correcting the reflections and modal discontinuities with (what one could call ‘antisound’) some kind of feedforward signal processing can do pretty well. I recall car manufacturers that have done research on this to get in-cabin engine, wind an tyre sound levels down, it wouldn’t surprise me to find that Boeing and Airbus have done the same.
Bottom line (for me, while I’m no HT expert at all) is that multichannel approach is best for masking (and partially damping) reflected sound (including modal behavior) in a small room. I bet no one could argue with that, the research on it is quite extensive and ‘theories haven’t been falsified’ to my knowledge. And in that sense I’m not totally convinced by the need for elaborate signal processing at one given point in space, the cost to get that right competes with the cost of a reasonable multichannel setup. Nothing stands in the way of combining both approaches btw. But we are drifting off topic (sorry TS).
I believe not. The room is still the room, so that even though the subwoofers might counteract the soundwave - the room will still reflect some energy more at certain frequencies, than others - because of its construction/dimensions/material/"reflectiveness". Adding more subwoofers will just smooth out the response, but will not reduce the time of how quickly the response dies out - here we need damping.
A speaker in a room, is like a box in a box - and would you build a speaker with no damping material inside?
Then it might be argued that there is not much damping material in a subwoofer - it just needs to be stiff and "dead"- Fair enough. But most rooms certainly are not closed, stiff and acoustically dead.
In a speaker you also heavily brace all surfaces and avoid longer wavelengths to build up. Again rather impractical in a listening room I would say
A simple thought experiment.
Imagine two parallel boundaries, spaced -say- 6m apart in an further open space, normal atmospheric conditions. Add one sound point source, producing random (pink) noise. At -say- 2m from one of both walls. What can one observe? A standing wave pattern with lowest mode at 29Hz, following modes on multiples of that 29Hz, right?
Now add a second, coherent point source (exactly the same signal) at pi/2 meters from the other wall. What happens to the standing waves we observed earlier?
Imagine two parallel boundaries, spaced -say- 6m apart in an further open space, normal atmospheric conditions. Add one sound point source, producing random (pink) noise. At -say- 2m from one of both walls. What can one observe? A standing wave pattern with lowest mode at 29Hz, following modes on multiples of that 29Hz, right?
Now add a second, coherent point source (exactly the same signal) at pi/2 meters from the other wall. What happens to the standing waves we observed earlier?
Same thing as 0.5236 in qw pipes to 1.0476,1.57…. The 3x 1/4 harmonic void is filled from excitation further down at 30 outa 90. Instead of 0 outta 90 at the closed end . In a compounded pipe that has a recipe for ultimate phase and it’s the same interval and numbers off 0.5236. Pi/6 or pi /12… square root of 4 I guess? Multiplied by the Golden ratio (phi)^2?? Weird? Maybe
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I thought Earl used one channel for all his subs, though that doesn't truly hold when using specific EQ on each one.
Sorry for being so cryptic. I simply wanted to highlight that the geometry of multiple drivers is acoustics. Newbies should not infer that "acoustical solution" implies only passive treatment.
That's ok
It's a big subject and bass is really important to great sound. I could never live without subwoofers again Yes - you might be able to imitate an acoustical room treatment, with active subwoofers - but do people really do that? and how much would it cost to set up? Not cheap I think.
I mean, having your mains running as deep as possible and then add 2-3 subwoofers, can really get you very very far into audio nirvana - without FIR, special damping, complicated software and heavy theory - or expensive DSP's, amplifiers, subwoofers or fancy anything.
Then if we want the pinnacle of sound quality, then it might require the icing on the cake..... but to get 90% of the way... I would say - don't make it anymore complicated than it has to be
I think that there are cases to be made for both active and passive solutions to LF problems. And, as I said before, the ideal is to do both, just as I do. If you can't do both then it's hard to say which is going to work better. It depends on the specifics.
Multiple subs get expensive and pose space problems. But LF absorption is notoriously difficult to get to really effect levels. So neither is easy, cheap or space saving.
Multiple subs get expensive and pose space problems. But LF absorption is notoriously difficult to get to really effect levels. So neither is easy, cheap or space saving.
Not quite. I have six 12"(1) and 15"(5) drivers to cover the modal range. Three play from the LFE channel which combines all LFs into one channel. But the other three (L,C,R) are still independent channels. Hence, almost stereo, but not quite.
The levels change of course, but what does that imply? The modal pattern is still the same. I don't see what you are getting at.
I wondered if all here grab it. That wasn’t obvious to me anyway.
The levels do change indeed. In a sense that almost all decrease quite a bit. In the given example the 29Hz would be stronger though. Always found it fascinating the modal sound field changes that much, while the properties defined by boundaries do not.
The levels do change indeed. In a sense that almost all decrease quite a bit. In the given example the 29Hz would be stronger though. Always found it fascinating the modal sound field changes that much, while the properties defined by boundaries do not.
Not really, all depends on SP Levels, but one can get like three or four 8 - 10 inch subs for around 150-500 bucks.
They will fit in around 15-20 liter each and in most cases is enough to give you permanent hearing damage.
For those who really want to get the best, go find some affordable 12-18 inch.
There are 15-18 inch woofers out there for around 150 euro or so.
As amplification, just use one of these PA amplifiers, something like a Behringer A800 or so.
But with some creativity one can get much better deals and make all of this even cheaper.
That's an awful lot cheaper than putting down dome huge helmholtz resonators.
Which can be difficult to construct without proper experience, and more over are a lot less predictable.
And for most, the rest of the family mostly doesn't appreciate such big renovation, while 3 subs can be extremely easily be hidden somewhere.
DSP are as cheap as 20-30 bucks these days, or just use some old computer (which can be doubled as a streaming thing, for movies, music, media center/HTPC) with a decent soundcard (which perform better than most CD players out there)
To be clear. we are talking steady state, with some kind of signal that contains 29 Hz - the fundamental resonance. That's my assumption. The levels everywhere could be higher or lower depending on the positions of the sources and their relative phase. Some phase will cancel completely and some will double the amplitude, and everything in between. The boundary properties do change all of this, in very complex ways. Reactive boundaries will shift the frequency peak and amplify any frequencies at that frequency. Absorption will decrease the standing wave portion, but the steady state sound will still be present. Simple "thought experiments" are anything but simple.