KeithL
Administrator 
Posts: 10,274
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Post by KeithL on Nov 23, 2022 15:58:36 GMT -5
I've heard of those active bass traps... and they seem like a very cool technology. (They're basically "an anti-subwoofer" that "eats" low frequency resonances by actively cancelling out their energy.) Paul makes a GOOD point. But going forward? How MANY persons can manage 165 measurements? That's gonna be HOURS of meticulous work and record keeping....... And there MAY BE choices to make. This is good here.....but another measure is is better THERE. And IF the Interior Decorator visits while you are out at the movies? Much work got shot to hell.... I did computer aided process design for semiconductor manufacture. ONE process.....With I don't remember how many variables. The program spit out what amounts to a research PHD worth of work. Well over 100 'requested' runs covering all variables and a RANGE of each. runs, counting setup and measure were maybe 4 hours EACH. Working SOLID 50 hour weeks? Works out to 8 weeks UNINTERUPTED. And what happens if you LATER add some of those floor-to-ceiling triangle shaped corner BASS TRAPS.......Or Clouds on the ceiling? In movies, you or I have a DSP (RMC-1) in chain - for Reference Stereo not, but every room has standing waves on specific frequencies.
I do not have a sub (not enough space, neighbors in the house etc.) to integrate in my system but standing waves.
I bought 2 active bass traps which did help me out of this. PSI Audio ACAA C20. You can read about the technology behind it hereThey work completely standalone, and work in every room - no setup. Just put in the corner, power on - they work. |
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Post by leonski on Nov 23, 2022 17:18:43 GMT -5
Distributor / Dealer located a convenient 3000km away.......I'll drop by at lunch......
You might call it a Plug-In Helmholtz.....
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Post by webmst007 on Nov 23, 2022 19:37:45 GMT -5
Active bass traps from Bagend have been around for a while in the studio world bagend.com/products/series/active-bass-trap-by-bag/The usual barrier to their wide spread implementation has been the costs. The Bagend units are not cheap and the psi's are around US$3K each or more I think ( although I could be wrong and they be more like 4K or more). That's a lot of traditional room treatment !! |
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Post by leonski on Nov 24, 2022 0:56:07 GMT -5
Actually? If you could locate a maximum pressure area and frequency? A tuned sub.....left UNPowered would resonate and soak up energy..... Of course, you'd need a properly 'tuned' sub with it's peak response being the frequency in question...... You may have better luck with a Helmholtz resonator. see link: www.sciencedirect.com/science/article/abs/pii/S096599781730635Xthis is the AUDIO application while the physics guys get WAY out on a limb and past my ability to even Pretend to understand....... Fact is? My DEN seemed to act in this fashion. My sub was located 15 to 18 feet away, in a corner across the room.......My DEN was hell to sit in when music played. It was like being in a 55 gallon DRUM being beaten.....the DRUM, not ME! When I moved the sub across that back wall and away from the corner? It all straightened out. Sub became musical and was now maybe 4 or 5 feet from the door......Sub was moved 12 to 14 feet, maybe.....I can now sit IN the den without discomfort while music or movies play..... It is possible to construct such devices IN the ceiling.....slot loaded, maybe, while if you are willing to give up a CLOSET in an adjacent room, you could use THAT approach..... |
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Post by aswiss on Nov 24, 2022 8:21:16 GMT -5
and the good thing is, that they do not impact the Bass signal or volume.
you get rid of all distortion created by standing waves.
They are not cheap (not for everyone's budget) - but on the other side, they fit perfect in a living room.
they work in every room without doing anything to the sound signal at all. I'm very happy with them.
I've heard of those active bass traps... and they seem like a very cool technology. (They're basically "an anti-subwoofer" that "eats" low frequency resonances by actively cancelling out their energy.) In movies, you or I have a DSP (RMC-1) in chain - for Reference Stereo not, but every room has standing waves on specific frequencies.
I do not have a sub (not enough space, neighbors in the house etc.) to integrate in my system but standing waves.
I bought 2 active bass traps which did help me out of this. PSI Audio ACAA C20. You can read about the technology behind it hereThey work completely standalone, and work in every room - no setup. Just put in the corner, power on - they work. |
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Post by aswiss on Nov 24, 2022 8:25:57 GMT -5
Distributor / Dealer located a convenient 3000km away.......I'll drop by at lunch...... You might call it a Plug-In Helmholtz..... Same is for me as I'm living in Switzerland, and having to sent back the RMC-1 for the Exchange to Emotiva next year (if no other solution is showing up next year).  |
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Post by PaulBe on Nov 24, 2022 9:46:51 GMT -5
Actually? If you could locate a maximum pressure area and frequency? A tuned sub.....left UNPowered would resonate and soak up energy..... Of course, you'd need a properly 'tuned' sub with it's peak response being the frequency in question...... You may have better luck with a Helmholtz resonator. see link: www.sciencedirect.com/science/article/abs/pii/S096599781730635Xthis is the AUDIO application while the physics guys get WAY out on a limb and past my ability to even Pretend to understand....... Fact is? My DEN seemed to act in this fashion. My sub was located 15 to 18 feet away, in a corner across the room.......My DEN was hell to sit in when music played. It was like being in a 55 gallon DRUM being beaten.....the DRUM, not ME! When I moved the sub across that back wall and away from the corner? It all straightened out. Sub became musical and was now maybe 4 or 5 feet from the door......Sub was moved 12 to 14 feet, maybe.....I can now sit IN the den without discomfort while music or movies play..... It is possible to construct such devices IN the ceiling.....slot loaded, maybe, while if you are willing to give up a CLOSET in an adjacent room, you could use THAT approach..... Any speaker that is unpowered is a tuned trap that soaks up energy at its resonant frequencies. Put an adjustable zobel/resonant-circuit across its terminals and you can tune it a bit. Short the terminals, like when turning ON the amplifer, and the speaker becomes detuned and benign – the cone becomes more stiff; resistant to movement. Having multiple speakers in a room, like in HT, becomes problematic when limiting amp-speaker usage; like when using 2 channel L&R stereo and the rest of the amps are turned off. DS will not do anything for this situation. A HT is like a speaker showroom in this case, where one pair of speakers is being auditioned among many speakers in the room. The best listening situation is to short all the unused speakers – the only practical way to do this at home is leave all the amps turned on, using the damping factor of the amps to soak up back EMF. (Now I’m waiting for someone to give a lecture about saving the planet). DS will have to utilize all speakers even when a limited number are playing any sound. Dipoles will offer no benefit – no box to trap the sound. DS will try to make broadband active traps like with the PSI device, but won’t be in the right locations. The PSI looks like the most interesting active device and quite a step up from the Bagend device. IIRC Nelson Pass made something like the Bagend device using a Sonotube type enclosure. Now on to rooms – Proscenium – each opening in a room is a kind of proscenium with a box/space behind it. The space behind is a tank/resonant circuit. If the space behind is in the right location, it can be a great benefit and soak up resonances – like if they are in the corners of a modal room. Many great diffuse concert halls have numerous devices like this. They are called box seats – tuned by the size, number of people in them, the door way to them, and the space/hallway behind them. My listening room has openings in 3 of 4 corners. One of them is a bathroom and can resonate like leonski’s den. I can adjust the resonance – tune the room - by how much I open or close the door. It still has a fundamental frequency determined by the volume of the bathroom. The other 2 corner openings lead to larger and more irregular spaces with additional openings and more broadband characteristics. The room makes fairly even bass with no additional treatments or room correction. An active fine tune correction could be the PSI Audio ACAA C20, as posted by aswiss, placed in the one closed corner. The most even bass in a modal room, with or without multi-subs, is in a room that has damped floppy floating walls, with insulation behind them. The wall behind should be stiff; not the wall facing the HT enclosure. This makes broadband bass damping and tends to enlarge the room to bass frequencies – a good thing. A damped wall is just a normal ½”sheetrock wall with 2x4s, floating, and insulation behind that wall. The stiff wall should be the wall on the adjacent space. Slot loading all the corners, if there are no corner openings, is an interesting idea to me. Could be effective, architecturally decorative, and have no negative impact on the room use. The perforations could be different sizes and shapes as desired. This is a multi-subject discussion. Leonski's link to "Several explanations on the theoretical formula of Helmholtz resonator" is a good base for discussion. Not sure what thread to put it all in. I think the “XMC … RMC … G3P … G4P? Processors — The Next Generation” is Not the best place. |
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Post by PaulBe on Nov 24, 2022 10:40:32 GMT -5
and the good thing is, that they do not impact the Bass signal or volume.
you get rid of all distortion created by standing waves.
They are not cheap (not for everyone's budget) - but on the other side, they fit perfect in a living room.
they work in every room without doing anything to the sound signal at all. I'm very happy with them.
I've heard of those active bass traps... and they seem like a very cool technology. (They're basically "an anti-subwoofer" that "eats" low frequency resonances by actively cancelling out their energy.) This PSI device is the most interesting active device I have seen. Costly, but the right after-market active tool for professional and home user alike. |
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Post by monkumonku on Nov 24, 2022 10:59:01 GMT -5
and the good thing is, that they do not impact the Bass signal or volume.
you get rid of all distortion created by standing waves.
They are not cheap (not for everyone's budget) - but on the other side, they fit perfect in a living room.
they work in every room without doing anything to the sound signal at all. I'm very happy with them. This PSI device is the most interesting active device I have seen. Costly, but the right after-market active tool for professional and home user alike. What's the price for something like that? Apparently there's no U.S. dealers. |
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Post by PaulBe on Nov 24, 2022 11:07:38 GMT -5
This PSI device is the most interesting active device I have seen. Costly, but the right after-market active tool for professional and home user alike. What's the price for something like that? Apparently there's no U.S. dealers. aswiss has information above in his posts. Appears to be about 3-4K a piece and no dealership in the USA. Edit - Oops. My price is about 1K too high. |
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Post by leonski on Nov 24, 2022 16:39:00 GMT -5
Actually? If you could locate a maximum pressure area and frequency? A tuned sub.....left UNPowered would resonate and soak up energy..... Of course, you'd need a properly 'tuned' sub with it's peak response being the frequency in question...... You may have better luck with a Helmholtz resonator. see link: www.sciencedirect.com/science/article/abs/pii/S096599781730635Xthis is the AUDIO application while the physics guys get WAY out on a limb and past my ability to even Pretend to understand....... Fact is? My DEN seemed to act in this fashion. My sub was located 15 to 18 feet away, in a corner across the room.......My DEN was hell to sit in when music played. It was like being in a 55 gallon DRUM being beaten.....the DRUM, not ME! When I moved the sub across that back wall and away from the corner? It all straightened out. Sub became musical and was now maybe 4 or 5 feet from the door......Sub was moved 12 to 14 feet, maybe.....I can now sit IN the den without discomfort while music or movies play..... It is possible to construct such devices IN the ceiling.....slot loaded, maybe, while if you are willing to give up a CLOSET in an adjacent room, you could use THAT approach..... Any speaker that is unpowered is a tuned trap that soaks up energy at its resonant frequencies. Put an adjustable zobel/resonant-circuit across its terminals and you can tune it a bit. Short the terminals, like when turning ON the amplifer, and the speaker becomes detuned and benign – the cone becomes more stiff; resistant to movement. Having multiple speakers in a room, like in HT, becomes problematic when limiting amp-speaker usage; like when using 2 channel L&R stereo and the rest of the amps are turned off. DS will not do anything for this situation. A HT is like a speaker showroom in this case, where one pair of speakers is being auditioned among many speakers in the room. The best listening situation is to short all the unused speakers – the only practical way to do this at home is leave all the amps turned on, using the damping factor of the amps to soak up back EMF. (Now I’m waiting for someone to give a lecture about saving the planet). DS will have to utilize all speakers even when a limited number are playing any sound. Dipoles will offer no benefit – no box to trap the sound. DS will try to make broadband active traps like with the PSI device, but won’t be in the right locations. The PSI looks like the most interesting active device and quite a step up from the Bagend device. IIRC Nelson Pass made something like the Bagend device using a Sonotube type enclosure. Now on to rooms – Proscenium – each opening in a room is a kind of proscenium with a box/space behind it. The space behind is a tank/resonant circuit. If the space behind is in the right location, it can be a great benefit and soak up resonances – like if they are in the corners of a modal room. Many great diffuse concert halls have numerous devices like this. They are called box seats – tuned by the size, number of people in them, the door way to them, and the space/hallway behind them. My listening room has openings in 3 of 4 corners. One of them is a bathroom and can resonate like leonski’s den. I can adjust the resonance – tune the room - by how much I open or close the door. It still has a fundamental frequency determined by the volume of the bathroom. The other 2 corner openings lead to larger and more irregular spaces with additional openings and more broadband characteristics. The room makes fairly even bass with no additional treatments or room correction. An active fine tune correction could be the PSI Audio ACAA C20, as posted by aswiss, placed in the one closed corner. The most even bass in a modal room, with or without multi-subs, is in a room that has damped floppy floating walls, with insulation behind them. The wall behind should be stiff; not the wall facing the HT enclosure. This makes broadband bass damping and tends to enlarge the room to bass frequencies – a good thing. A damped wall is just a normal ½”sheetrock wall with 2x4s, floating, and insulation behind that wall. The stiff wall should be the wall on the adjacent space. Slot loading all the corners, if there are no corner openings, is an interesting idea to me. Could be effective, architecturally decorative, and have no negative impact on the room use. The perforations could be different sizes and shapes as desired. This is a multi-subject discussion. Leonski's link to "Several explanations on the theoretical formula of Helmholtz resonator" is a good base for discussion. Not sure what thread to put it all in. I think the “XMC … RMC … G3P … G4P? Processors — The Next Generation” is Not the best place. Shorting out the speaker terminals is a great way to simulate a very HIGH damping factor....Which I'd think, using a sub as a 'bass management tool'.....would be a good idea. That energy has to go SOMEWHERE and if the VoiceCoil is a short......it turns into heat. But not much, since the amount of energy is VERY low, as such things go. A big-box speaker Might be 5% or even 6% 'efficient' which as such things go, is not a big value.... As an example? My Magnepans are probably LESS than 2% efficient. Maybe lower. Using (basically) the subs surround to absorb energy is not best use. At the point of NO connection to anything? Magnet / Voice coil are out of the picture. BTW, Paul?? NOBODY around her speaks Any Latin. |
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Post by aswiss on Nov 24, 2022 16:41:24 GMT -5
This PSI device is the most interesting active device I have seen. Costly, but the right after-market active tool for professional and home user alike. What's the price for something like that? Apparently there's no U.S. dealers. I paid around 2300 swiss francs/each (this includes 7.7% taxes) - so around 2450$/each. I have 2 in use in the front left and right corners
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Post by webmst007 on Nov 24, 2022 17:36:14 GMT -5
Paul - your comment " experience with PA Cardioid Arrays is not applicable to small room management " is not correct . The Cardioid bass management process is based on delay and volume together with physical placement used together essentially designed to reduce stage bass bleed and allows the use of accurate beam-forming designs for bass. These principles are exactly the same methods as proposed Dirac Spatial using speaker co- optimisation with frequency and impulse response. Dirac refers to this as "super speakers" See
"DS will try to make broadband active traps like with the PSI device, but won’t be in the right locations."
P - based on Dirac's own paper (see link above) I think that assessment is too simplistic a description of how Dirac Spatial will employ a large array of speakers to interact with each other in the sound field.
I do not see any evidence as yet Dirac intends to use "speaker boxes" for anything other than sound reproduction (unless we count ported designs of course)
So a typical DS install will employ larger full range arrays in the base layer Probably joining a full sub array. Height and ceiling speakers will be an interesting design area for DS as well. |
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KeithL
Administrator
Posts: 10,274
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Post by KeithL on Nov 25, 2022 2:46:43 GMT -5
The idea of using a speaker as a bass trap is sort of interesting... but it is generally not a good idea.
As Leonski said, if you short the terminals, you are effectively applying a near-infinite damping factor (actually limited by the internal impedance of the voice coil). However, since this "applies braking force to the cone", it makes it more difficult for the cone to move. (And this means that a smaller percentage of the acoustic energy striking the cone will be absorbed, and so more of it will be reflected.) (If the cone really were "perfectly damped" you would simply have a solid box.)
Either way, however, the issue is that the cone has a very limited surface area compared to the room. And it can only passively absorb energy that strikes it - so only over its actual area. Even if such a cone could be "a perfect absorber" it would produce no more effect than simply cutting a hole of the same size in the wall.
(So you would need to have a whole bunch of them, covering a relatively large area, to be very effective.)
Those active bass traps are not just a driver with some passive load attached to them. They are a powerful subwoofer, with its own amplifier, and a DSP that actually calculates an active out-of-phase signal to CANCEL OUT the undesired energy.
If I remember correctly, they actually have a microphone, rather than using sound striking the driver itself. In effect they work like giant sound cancelling headphones...
However, in this case, rather than mix their signal with the incoming audio electronically, they generate it acoustically using their own amplifier and driver.
(Assuming that the microphone is back against the wall they can calculate a sort of negative feedback signal to "null out the node at the wall"... )
Any speaker that is unpowered is a tuned trap that soaks up energy at its resonant frequencies. Put an adjustable zobel/resonant-circuit across its terminals and you can tune it a bit. Short the terminals, like when turning ON the amplifer, and the speaker becomes detuned and benign – the cone becomes more stiff; resistant to movement. Having multiple speakers in a room, like in HT, becomes problematic when limiting amp-speaker usage; like when using 2 channel L&R stereo and the rest of the amps are turned off. DS will not do anything for this situation. A HT is like a speaker showroom in this case, where one pair of speakers is being auditioned among many speakers in the room. The best listening situation is to short all the unused speakers – the only practical way to do this at home is leave all the amps turned on, using the damping factor of the amps to soak up back EMF. (Now I’m waiting for someone to give a lecture about saving the planet). DS will have to utilize all speakers even when a limited number are playing any sound. Dipoles will offer no benefit – no box to trap the sound. DS will try to make broadband active traps like with the PSI device, but won’t be in the right locations. The PSI looks like the most interesting active device and quite a step up from the Bagend device. IIRC Nelson Pass made something like the Bagend device using a Sonotube type enclosure. Now on to rooms – Proscenium – each opening in a room is a kind of proscenium with a box/space behind it. The space behind is a tank/resonant circuit. If the space behind is in the right location, it can be a great benefit and soak up resonances – like if they are in the corners of a modal room. Many great diffuse concert halls have numerous devices like this. They are called box seats – tuned by the size, number of people in them, the door way to them, and the space/hallway behind them. My listening room has openings in 3 of 4 corners. One of them is a bathroom and can resonate like leonski’s den. I can adjust the resonance – tune the room - by how much I open or close the door. It still has a fundamental frequency determined by the volume of the bathroom. The other 2 corner openings lead to larger and more irregular spaces with additional openings and more broadband characteristics. The room makes fairly even bass with no additional treatments or room correction. An active fine tune correction could be the PSI Audio ACAA C20, as posted by aswiss, placed in the one closed corner. The most even bass in a modal room, with or without multi-subs, is in a room that has damped floppy floating walls, with insulation behind them. The wall behind should be stiff; not the wall facing the HT enclosure. This makes broadband bass damping and tends to enlarge the room to bass frequencies – a good thing. A damped wall is just a normal ½”sheetrock wall with 2x4s, floating, and insulation behind that wall. The stiff wall should be the wall on the adjacent space. Slot loading all the corners, if there are no corner openings, is an interesting idea to me. Could be effective, architecturally decorative, and have no negative impact on the room use. The perforations could be different sizes and shapes as desired. This is a multi-subject discussion. Leonski's link to "Several explanations on the theoretical formula of Helmholtz resonator" is a good base for discussion. Not sure what thread to put it all in. I think the “XMC … RMC … G3P … G4P? Processors — The Next Generation” is Not the best place. Shorting out the speaker terminals is a great way to simulate a very HIGH damping factor....Which I'd think, using a sub as a 'bass management tool'.....would be a good idea. That energy has to go SOMEWHERE and if the VoiceCoil is a short......it turns into heat. But not much, since the amount of energy is VERY low, as such things go. A big-box speaker Might be 5% or even 6% 'efficient' which as such things go, is not a big value.... As an example? My Magnepans are probably LESS than 2% efficient. Maybe lower. Using (basically) the subs surround to absorb energy is not best use. At the point of NO connection to anything? Magnet / Voice coil are out of the picture. BTW, Paul?? NOBODY around her speaks Any Latin. |
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Post by leonski on Nov 25, 2022 20:38:09 GMT -5
A 'shorted' cone woofer in an enclosure will have max absorption of bass energy at its resonant frequency? Isn't that the max amplitude of response?
If that's true, than the response AND absorbtion of sound will fall at 6 or 12 db/octave below that frequency. I don't see that being particularly useful.
Keith's 'hole in the wall' COULD turn into a helmholtz.......
Using an active response model, like noise canceling headphones? I can see this actually working, for those who are comfortable with yet MORE system feedback....
My ONLY Latin? "Illegitimi non carborundum" good advice, any way you read it!
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Post by PaulBe on Nov 26, 2022 9:40:19 GMT -5
A 'shorted' cone woofer in an enclosure will have max absorption of bass energy at its resonant frequency? Isn't that the max amplitude of response? If that's true, than the response AND absorbtion of sound will fall at 6 or 12 db/octave below that frequency. I don't see that being particularly useful. Keith's 'hole in the wall' COULD turn into a helmholtz....... Using an active response model, like noise canceling headphones? I can see this actually working, for those who are comfortable with yet MORE system feedback.... My ONLY Latin? "Illegitimi non carborundum" good advice, any way you read it! Are you responding to a post or just throwing questions into the wind? It’s hard to know. Maybe that’s the point. Since you added another bit about Latin, I’ll assume at least part of your post is for me. A speaker/driver will have max amplitude at resonance, within its passband, If the Qtc is above .7. Minimum response fall below resonance is 12dB/Oct, and that is with a closed box. The fall is generally greater with other alignments. The fall is mitigated with room rise at very low frequencies. Room rise tends to be useless for ported and dipole systems. Who wrote “A 'shorted' cone woofer in an enclosure will have max absorption of bass energy at its resonant frequency?” I didn’t. A shorted cone has no, or little, resonant frequency. A short can be a wire across the speaker terminals, or, an attached and powered amplifier. An open cone is a passive radiator with a specific mass; put it into a box, and it will move more at a specific frequency; sort of like a port; a reactive load. A small number of devices like this in a room will have little impact. Increase the number and driver sizes, and it will affect the room response; like with un-driven speakers in a speaker show room. DS intends large driver sizes, and greater numbers. I’m having a little trouble reconciling their Mission Statement with their plans – “Our Mission - Enable superior sound experiences across content and devices, for the many, not the few, through pioneering digital audio solutions”… SMH. www.dirac.com/the-arrival-of-spatial-room-correction-technology/Concerning your comment on an ‘active response model’ – Try rereading how the PSI device works. Their model reminds me of how Sabine reduces microphone feedback in a concert hall. alter.com/trademarks/sabine-adaptive-audio-75378471 - Looks like the Sabine company no longer exists. BTW, your Magneplanar MG1.6QR speakers have a sensitivity of 86 dB (2.83V/500Hz/1 M). That translates to an efficiency of about .3%; not anywhere near 2%. As efficiencies rise above .5-1 %, the speaker list grows much shorter. Since you are still focused on Latin: Quod-Sumus Hoc Ecitis – “Such as we are, you will be”. Good bye. |
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Post by leonski on Nov 26, 2022 16:53:56 GMT -5
I knew maggies are VERY low efficiency. The rest is WASTE.....and using
when I worked semiconductor manufactor (in 'fab') the measure at probe was RdOn....resistance of the device when ON.....Not quite zero, of course, but generally, lower better.....
DS has good BS in its advertising....trying to convince that the cost is 'nominal' or not out of reach.....
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Post by webmst007 on Nov 26, 2022 20:32:33 GMT -5
Regarding Dirac Spatial and Dipoles: sorry I don't see dipole speaker design prohibiting the use of DS at all.
I think this is misconstrues how this technology actually works.
That said it will be far more dependant on how well a speaker can perform and it has to be said - some dipoles are less than stellar - especially some electrostatics I've played with.
Cheers
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Post by PaulBe on Nov 27, 2022 4:55:32 GMT -5
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Post by davidl81 on Nov 27, 2022 10:32:42 GMT -5
My RMC-1 does everything that I need it to do so I don’t “need” a G4 processor. That being said at the price point that Emotiva is letting these get traded in for I will be getting a G4 unit. It’s too good of a deal just to get the new hardware and be 5 year more recent of a unit.
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Paul makes a GOOD point.
