KeithL
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Post by KeithL on Feb 24, 2022 9:49:50 GMT -5
The short answer is no... If you want to design your own filter, that does exactly what you want, from scratch, then this is how you do it...
And it's not gibberish... it's all perfectly clear and concise...
(Not to me... I don't understand all of that math either... which is why we either hire someone to do it for us or buy one that's already been done for us).
More to the point, the MiniDSP does come with a selection of "canned" filters, so most of the people who buy and use the MiniDSP don't understand all of that math either...
And, even more to the point, there's no such thing as "perfect room correction", or even "perfect woofer alignment"... There is no possible setting that will be perfect at more than a single point in 3D space in the room... if even that is possible at all frequencies. So it's kind of like asking: "What do I have to do to create the perfect painting?"
The answer being that such a thing isn't possible... so all you can do is decide what will satisfy your needs... and what you need to get there.
(What's nice about something like the MiniDSP is that you can use the canned filters... Or, if you do understand that math, it actually enables you to USE it in the real world... (There are plenty of programmers and engineers who understand the math but wouldn't even consider sitting down and building the hardware required to use it.)
You may also be shocked to know that there were people who thought their systems sounded great even before DSP filters existed...  (And, for that matter, even before subwoofers existed...)
And, just for the record, there ARE simple filters, that you can design using plain math...
Here's a page where you can design a 2-way second-order 12 dB/octave Linkwitz-Riley crossover - just by plugging in the numbers. (They give all the formulas... and all it takes to understand them is a bit of high-school algebra.)
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Post by donh50 on Feb 24, 2022 10:15:01 GMT -5
There are other articles targeting more of a lay audience. That one says "technical article" for a reason, and is actually a pretty good description after a quick skim. All About Circuits targets a different audience than your average audiophile... In additional to some undergrad signal processing courses (including continuous and discrete time courses after the basics), I had two graduate courses in DSP and digital filters, so it is not necessarily a simple subject. If you are designing them from scratch you do need to understand the math behind them. Fortunately, there are a lot of programs now that do it for you. Here are a few articles after a quick search: dspguru.com/dsp/faqs/fir/basics/eclipseaudio.com/fir-filter-guide/Wikipedia gets fairly deep into math: en.wikipedia.org/wiki/Finite_impulse_responseIIR filters are usually based on conventional analog filter topologies so are easier to understand. There are pros and cons of either, natch. Back before DSP was widely available, I designed an analog (op-amp based) servo sub circuit including crossover and feedback (servo) circuit. I included analog all-pass filters to provide adjustable delay after the crossover to help dial it all in. So there are ways to do it "old school", but I would not do it that way now -- DSPs are easier, have greater dynamic range, are more stable, etc. Things like miniDSP have made it fairly easy to get into DSP without breaking (much of) a sweat and without having to deal with all the math. HTH - Don Edit: Keith pretty much said it all; I did not see his post before I responded. |
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Post by p4t on Feb 25, 2022 8:25:57 GMT -5
Nope. But these are very interesting! They remind me of subwoofer arrays I've read about, mainly for arenas and theaters, whereby subs are arranged in patterns to create specific dispersion patterns. A stack of three subs with top and bottom facing frontwards and the middle facing rearwards creates a cardioid pattern. This is useful for a stage where the sound engineer doesn't want to overload the musicians onstage with excess bass. The bass propagates out to the audience in a horizontal cardioid pattern. Something that's pointed out in some of the array layout articles I've read is that when subs are stacked vertically the sound is propagated horizontally. With subs lined up side by side they propagate the sound more vertically. So if placing subs on the floor, unless you want the sound to be squeezed width-wise, place them far enough apart so that they don't interact as an array.   The DXD-12012, according to the review, has very low distortion by way of its design. Not much to look at, but seems like a great performer, especially when quad-stacked!! Four stacks of four is only $50,000.  I own two DXD 12012’s and wish I had two more so I could stack two sets! They are also impressive when not stacked. Very quick sounding and exceptional for music. I plan to use them with a pair of Magneplanar 3.7i’s. It should be interesting. In stacks of two, the subs are address room modes because of the height of the subs. I would imagine a stack of four would be eye opening. How significant the sound difference between stacked and not? I just realized that these already discontinued for dxd 12012 and dxd 808. Because I also interested to try this KK subwoofer. I can get 4 dxd 808 used one. What do you think? |
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Post by marcl on Feb 25, 2022 9:01:27 GMT -5
I found a very good video for "aligning" multiple subs together using REW. For "normal" setups with multiple subs connected to a miniDSP, one input from the processor, multiple outputs to all the subs, the procedure is very well explained. It looks to be quite a bit easier than how I've been doing things, so I'll try it out this weekend. I spent most of yesterday and this morning using this method to align my subs to each other, and also to align my front L/R 3.7 speakers to their corresponding DWM woofer modules and summed sub output. I had previously tried to use the Alignment Tool's automated functions to align phase at crossover points. I really didn't have much success with that in my configuration. But the method described in this video that uses the simulation of the combined response and the slider to introduce delay to one speaker worked really well! I was able to realize a significant improvement to the response of the subs alone playing LFE, as well as my front L/R playing through each 3.7, DWM and summed sub output. Then this morning I took a second step and tried repositioning the DWMs to see if I could improve response further and eliminate a cancellation at 90Hz. The DWMs play 40-300Hz and are only 2x2ft so they are easily repositioned to fill in nulls. This was also successful, and I repeated the measurements and adjustments with the Alignment Tool and realized a bit more improvement on the left channel. In addition to the frequency response improvements, I also found that phase was much better aligned between the L/R channels and Group Delay for each was much improved, eliminating some significant peaks below 100Hz. I expect all of this will correlate to better imaging. Excess Group Delay in each channel correlates exactly with the 60Hz dip ... but I have no idea how to correct that since it can't be EQ'ed. Here's the response of each channel before the Alignment Tool optimization, after initial optimization, and after DWM reposition and final optimization. The 60Hz dip is impossible to eliminate with these methods but after a Dirac calibration its effect will be minimized. <button disabled="" class="c-attachment-insert--linked o-btn--sm">Attachment Deleted</button> + fbczar leonski ttocs Having done this alignment with no Dirac, I had to do a full Dirac calibration. But before doing this I experimented with All Pass filters on both DWMs using the standard filters in miniDSP HD. First, the right channel had a curious dip at 340Hz which is right at the upper end of the DWM range. In this case the AP filter at 340Hz with Q=1 worked and took the dip right out. Both channels showed a dip at 60Hz but the AP filter did nothing, or made it worse. Trial and error ... not sure why it works sometimes and not others. But the Group Delay plots all showed Excess Group Delay right at 60Hz. So I completed Dirac cal with my usual pattern of 13 points, Volume levels set to -18db for Center Sub and -27db for all other speakers. My same flat target curves as before, with the left curtain pulled just slightly left of 16Hz to the point that it didn't affect the predicted response at the 16Hz corner. Here's a comparison of the Feb 2 calibration, and then the one Feb 24 after all the sub delay tweak with the Alignment Tool, physical DWM rearrangement to eliminate the 90Hz dip, and final DWM delay tweak with the Alignment Tool. Especially impressive to be this good in the bass with Variable Smoothing! And look how the Phase anomalies are gone.    Notice the 300Hz dip in the center channel. There is no dip there in the Dirac measurement so it must be some interaction after bass management is applied to the center channel. Center crosses over at 100Hz to the L/R. This dip can't be corrected in Dirac by adding a reverse bump in the target curve ... it's a non-minimum phase anomaly like the 60Hz dip. If I had the center channel running through a miniDSP I might be able to fix it with an AP filter ... but alas. |
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Post by marcl on Feb 25, 2022 9:30:37 GMT -5
I own two DXD 12012’s and wish I had two more so I could stack two sets! They are also impressive when not stacked. Very quick sounding and exceptional for music. I plan to use them with a pair of Magneplanar 3.7i’s. It should be interesting. In stacks of two, the subs are address room modes because of the height of the subs. I would imagine a stack of four would be eye opening. How significant the sound difference between stacked and not? I just realized that these already discontinued for dxd 12012 and dxd 808. Because I also interested to try this KK subwoofer. I can get 4 dxd 808 used one. What do you think? + fbczar ttocs As ttocs and I have discussed the stacked sub idea over the past few months, I've wondered if this technique works in rooms the way it does in sound reinforcement. I researched a bit and didn't find much on using it in rooms. But the reason I wonder is that with bass wavelengths being so long there might not be enough "room in a room" for the lobes to settle out into the predicted response. That's not to say it wouldn't do anything ... ttocs has made it work after a lot of experimentation. But in sound reinforcement the goals are different ... trying to put a cancellation node on the stage so as not to explode the performers, and then uniformly spreading bass over a distance in a such a way that its not 140db 20ft from the stage in order to get 95db 150ft back. Just sayin'  |
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KeithL
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Post by KeithL on Feb 25, 2022 10:56:05 GMT -5
There's another interesting thing to consider there...
In a large venue, with high ceilings, you can probably consider stacked subs as being in a single location VERTICALLY. (If you have twenty foot ceilings, whether you have one or two 24" cabinets, stacked vertically, won't make much difference.)
However, in a typical home environment, if one sub is sitting on the floor, the one on top of it is 20% of the way between the floor and the ceiling. Therefore you now have a third dimension to consider... and nodes and nulls in the vertical dimension. Moving a sub up from the floor is exactly analogous to moving one away from any other "corner" or "boundary".
It's also worth remembering that looking at the three dimensions separately is a convenient simplification... And you are going to get the most reflections and resonant buildup between parallel surfaces... But, at low frequencies in particular, sound travels in all directions. A bass note isn't three waves, traveling neatly in three dimensions...
It's really a "spherical wave" at relatively higher frequencies...
And, at frequencies where the wavelength is longer than the room dimension, it acts more like a propagating pressure wavefront...
Now, if you really want to get extreme, how about a subwoofer line source?
A vertical column of subs extending fully from floor to ceiling.
(Theoretically, the sound should propagate better horizontally, and you more or less eliminate that third dimension consideration.)
How significant the sound difference between stacked and not? I just realized that these already discontinued for dxd 12012 and dxd 808. Because I also interested to try this KK subwoofer. I can get 4 dxd 808 used one. What do you think? + fbczar ttocs As ttocs and I have discussed the stacked sub idea over the past few months, I've wondered if this technique works in rooms the way it does in sound reinforcement. I researched a bit and didn't find much on using it in rooms. But the reason I wonder is that with bass wavelengths being so long there might not be enough "room in a room" for the lobes to settle out into the predicted response. That's not to say it wouldn't do anything ... ttocs has made it work after a lot of experimentation. But in sound reinforcement the goals are different ... trying to put a cancellation node on the stage so as not to explode the performers, and then uniformly spreading bass over a distance in a such a way that its not 140db 20ft from the stage in order to get 95db 150ft back. Just sayin'  |
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Post by marcl on Feb 25, 2022 11:29:49 GMT -5
There's another interesting thing to consider there...
In a large venue, with high ceilings, you can probably consider stacked subs as being in a single location VERTICALLY. (If you have twenty foot ceilings, whether you have one or two 24" cabinets, stacked vertically, won't make much difference.)
However, in a typical home environment, if one sub is sitting on the floor, the one on top of it is 20% of the way between the floor and the ceiling. Therefore you now have a third dimension to consider... and nodes and nulls in the vertical dimension. Moving a sub up from the floor is exactly analogous to moving one away from any other "corner" or "boundary".
It's also worth remembering that looking at the three dimensions separately is a convenient simplification... And you are going to get the most reflections and resonant buildup between parallel surfaces... But, at low frequencies in particular, sound travels in all directions. A bass note isn't three waves, traveling neatly in three dimensions...
It's really a "spherical wave" at relatively higher frequencies...
And, at frequencies where the wavelength is longer than the room dimension, it acts more like a propagating pressure wavefront...
Now, if you really want to get extreme, how about a subwoofer line source?
A vertical column of subs extending fully from floor to ceiling.
(Theoretically, the sound should propagate better horizontally, and you more or less eliminate that third dimension consideration.)
+ fbczar ttocs As ttocs and I have discussed the stacked sub idea over the past few months, I've wondered if this technique works in rooms the way it does in sound reinforcement. I researched a bit and didn't find much on using it in rooms. But the reason I wonder is that with bass wavelengths being so long there might not be enough "room in a room" for the lobes to settle out into the predicted response. That's not to say it wouldn't do anything ... ttocs has made it work after a lot of experimentation. But in sound reinforcement the goals are different ... trying to put a cancellation node on the stage so as not to explode the performers, and then uniformly spreading bass over a distance in a such a way that its not 140db 20ft from the stage in order to get 95db 150ft back. Just sayin' Yes and to the last point ... Maggies that go down to 40Hz like the 3.7 or into the 20's like the 30.7 ... not quite floor to ceiling but 6-7ft tall and much more line-ish than any conventional speaker (other than maybe the OB dipoles with three drivers). |
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KeithL
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Post by KeithL on Feb 25, 2022 12:34:46 GMT -5
That's not a naive question at all... (The naive ones are the folks who think that the simplified models we all use tell the whole story.)
The short answer is that... there really isn't a complete and accurate short answer.
At high frequencies sound waves act somewhat like light... so you can envision how the waves travel by thinking about a light bulb and mirrors.. or water waves in a bathtub. But, in another sense, you can sort of think of it as if the speaker is "launching the wave into the room", like throwing a rubber ball.
The waves travel out, hit surfaces, either reflect as "a sharp reflection" or "a diffuse reflection", are absorbed more or less by different surfaces, and eventually end up being totally absorbed. (Where, to be technical, they eventually end up pretty much as heat.)
However, with bass notes, which have wavelengths in the same range as the dimensions of a room, or perhaps even much longer, it gets FAR more complicated. Essentially, since the entire wave "doesn't fit in the dimension of the room", as the woofer moves forward, it tries to "launch" the wave into the room, but the air pressure in the room pushes back. (To use the previous analogy imagine trying to "throw" a ten foot diameter foam rubber ball in a phone booth.)
So, at VERY low frequencies, where the wavelength is a lot larger than the room dimension, it acts more like a change in pressure than a wave. The woofer moves forward, the inside of the woofer cabinet gets a bit bigger, the remaining volume of the air in the room gets a bit smaller, the air pressure in the room goes up, then it all happens in reverse, back and forth. (Think about it as if the room was sealed and one of the walls was moving in and out.)
Of course, it all gets VERY tricky at the point in between, where it acts sort of like a wave, and sort of like a change in pressure.
This is one of the things that makes "accurately calibrating a subwoofer" so tricky... And one of the reasons why there is no specific absolute way to "get it right".
From the point of view of "pure physics" it isn't all that complicated. The reason "sound acts like a wave" is that, as the speaker moves forward, it raises the pressure of the air in front of it, and vice versa. However the "effect" of that increase in pressure only propagates through air at around 1100 feet per second. So, if the speaker moves forward now, because of the -physical characteristics of air, the increase in pressure takes about 1/100 of a second to reach a point ten feet away from it.
(And that movement is what we call a pressure wave or, in terms of audio, "a sound wave".)
The closest SIMPLE way to think of it would probably be to imagine dropping several bowling balls into a swimming pool one after the other.
(But your swimming pool is really a pond, with oddly shaped edges, lined with different sorts of materials, and it's all happening in three dimensions instead of two.)
Now you know why, even with all we know, there always ends up being a lot of trial and error in order to get the best results in a certain situation.
And, to answer your final question, about "interfering with all the other frequencies".... Excluding some really complicated details which aren't especially significant for our purposes... Sound waves at various frequencies will generally travel through each other without "interfering" with each other... If you look at the air pressure at a given point it will be the SUM of all the sound waves going through that point at that moment... (So, if you were listening at that point, you would hear the sum of the sounds they represent.)
But each individual "sound wave" will continue on its way without being significantly affected by the others. A "node" is simply a point where, at a certain frequency and location, the high and low points from two waves tend to arrive at the same time, and so add together... And a "null" is just a point where, at a certain frequency and location, the high points from one wave tend to arrive at the same time as the low points from another, and so they cancel out...
If you have two sound waves, at two different frequencies, they will tend to add and cancel at random locations, which change from moment to moment... And, since this doesn't create any specific long-term pattern, we don't notice it.... (Much as you usually don't notice distinct sharp patterns on your walls from two lamps with "soft white light bulbs".)
However, when two waves at the same or similar frequencies are involved, you tend to end up with "fixed patterns" of "bright and dark spots", which tend to be noticeable. (You get the same effect if you light something with two LASER beams of similar frequencies rather than two light bulbs...)
There's another interesting thing to consider there... In a large venue, with high ceilings, you can probably consider stacked subs as being in a single location VERTICALLY. (If you have twenty foot ceilings, whether you have one or two 24" cabinets, stacked vertically, won't make much difference.) However, in a typical home environment, if one sub is sitting on the floor, the one on top of it is 20% of the way between the floor and the ceiling. Therefore you now have a third dimension to consider... and nodes and nulls in the vertical dimension. Moving a sub up from the floor is exactly analogous to moving one away from any other "corner" or "boundary". It's also worth remembering that looking at the three dimensions separately is a convenient simplification... And you are going to get the most reflections and resonant buildup between parallel surfaces... But, at low frequencies in particular, sound travels in all directions. A bass note isn't three waves, traveling neatly in three dimensions...
It's really a "spherical wave" at relatively higher frequencies...
And, at frequencies where the wavelength is longer than the room dimension, it acts more like a propagating pressure wavefront...
Now, if you really want to get extreme, how about a subwoofer line source?
A vertical column of subs extending fully from floor to ceiling.
(Theoretically, the sound should propagate better horizontally, and you more or less eliminate that third dimension consideration.) Kindly excuse my naivety, but what does a 28' long (diameter?) 40hz bass 'bubble/sphere' do when it hits the boundaries of my 14' x 22'x7' room? Does it bounce off/reverberate or dissipate in some way or generally interfere with all the other frequencies? My Princeton's 😕 |
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Post by marcl on Feb 25, 2022 13:27:49 GMT -5
That's not a naive question at all... (The naive ones are the folks who think that the simplified models we all use tell the whole story.)
The short answer is that... there really isn't a complete and accurate short answer. .......... Kindly excuse my naivety, but what does a 28' long (diameter?) 40hz bass 'bubble/sphere' do when it hits the boundaries of my 14' x 22'x7' room? Does it bounce off/reverberate or dissipate in some way or generally interfere with all the other frequencies? My Princeton's 😕 + Old Blevins And also there are simulators, some real expensive and some free (i.e. REW), to try to model a room by entering dimensions, speaker types and locations, listening positions and some other variables. They can't be 100% accurate in an absolute sense, but they can be relatively accurate to show the effect of a change. I've used it to play with speaker locations. With the experimenting I did this week with the REW Alignment Tool I came up with new delays for my subs. I can put those delays into REW Room Sim and see at least at a high level did it get better or worse? Then measure the response and see how it correlates. So it got better, then I reran Dirac and measured the results vs my last calibration ... and it got better still. Absolute 100% correlation? No. But relatively accurate and useful? Yes, I think so. And speaking of how the waves interact - excellent description Keith! - we can look at room dimensions and as a first pass know that there will be resonances at even multiples of certain frequencies as a function of each dimension .... (1100ft/sec)/2(dimension)=the fundamental resonance for that dimension as the frequency whose half wavelength is that dimension. The 14x22x7 room has resonances at multiples of 39.3, 25 and 78.6Hz respectively. That is, up to the transition frequency which is probably around 200Hz. And noting that the width and ceiling are multiples, some of those resonances will stack up. And resonances may end up as nodes or nulls, as Keith said. This is about the dimensions where the waves DO fit evenly, but you can see how all these multiples can end up very close to each other. And these are just the two-surface resonances ... there are more complex resonances that combine non-parallel surfaces. I'll stick my neck out and say even though simulations and measurements have their limitations, I really don't think an actual audible result will end up OPPOSITE what the simulations and measurements indicate ... just maybe a little more or less in the same direction. |
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Post by leonski on Feb 25, 2022 16:00:19 GMT -5
However, in a typical home environment, if one sub is sitting on the floor, the one on top of it is 20% of the way between the floor and the ceiling. Therefore you now have a third dimension to consider... and nodes and nulls in the vertical dimension. Moving a sub up from the floor is exactly analogous to moving one away from any other "corner" or "boundary" Ceiling bounce modes are THERE if you consider them or NOT..... www.mcsquared.com/modecalc.htmA room mode calculator MAY be helpful to visualize just what you have going on.......But keep in mind that the more 'bounces', the more attenuation and the less important that mode becomes.... A Floor-Wall-Ceiling 'bounce' may be interesting to view or think about, but is of lesser importance than any of the 'straight' reflections. And while it is very true that 'no short answer' will usually suffice, knowledge of the principles MAY prevent too many blind 'rabbit hole' solutions.... |
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ttocs
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Post by ttocs on Feb 25, 2022 17:08:26 GMT -5
There's another interesting thing to consider there... In a large venue, with high ceilings, you can probably consider stacked subs as being in a single location VERTICALLY. (If you have twenty foot ceilings, whether you have one or two 24" cabinets, stacked vertically, won't make much difference.)
I agree.
However, in a typical home environment, if one sub is sitting on the floor, the one on top of it is 20% of the way between the floor and the ceiling. Therefore you now have a third dimension to consider... and nodes and nulls in the vertical dimension.
Yes and not quite. See next answer.
Moving a sub up from the floor is exactly analogous to moving one away from any other "corner" or "boundary".
Kind of. Something to consider here is that when the drivers are as close together as can be that they become "sort of" one driver, and not so much two distinct drivers as if the second one had no interaction with the first.
It's also worth remembering that looking at the three dimensions separately is a convenient OVER-simplification... And you are going to get the most reflections and resonant buildup between parallel surfaces... But, at low frequencies in particular, sound travels in all directions. A bass note isn't three waves, traveling neatly in three dimensions...
It's really a "spherical wave" at relatively higher frequencies...
And, at frequencies where the wavelength is longer than the room dimension, it acts more like a propagating pressure wavefront...
Now, if you really want to get extreme, how about a subwoofer line source?
A vertical column of subs extending fully from floor to ceiling.
(Theoretically, the sound should propagate better horizontally, and you more or less eliminate that third dimension consideration.)
This is something I've been wanting to try for a very long time, and that time might be within the next couple weeks.
+ fbczar ttocs As ttocs and I have discussed the stacked sub idea over the past few months, I've wondered if this technique works in rooms the way it does in sound reinforcement. It doesn't work the same way, but it can help a little with the boundary effect. I played with this a bit, but finally settled on placing the subs with the speakers where I wanted the speakers to be based upon a slight compromise in performance. This is why I have a subwoofer at the rear of the room to help with EACH front speaker and also BOTH front speakers.I researched a bit and didn't find much on using it in rooms. It's almost impossible to find info on this, especially from Rel. Mums the word.But the reason I wonder is that with bass wavelengths being so long there might not be enough "room in a room" for the lobes to settle out into the predicted response. That's not to say it wouldn't do anything ... ttocs has made it work after a lot of experimentation. My original goal was to find out what Rel was talking about because nothing is written about what the actual effect is supposed to be. The result of stacking subs next to a speaker is more dynamic bass. All the drivers are working with less effort, and each is tuned differently to cover less and less of the frequency spectrum so that one sub is only playing the lowest frequencies in a very limited range.My stacks are only in pairs. I tried a 3 stack and it was an improvement all around, but I didn't have enough subwoofers to have two 3-stacks, and frankly, I'd already achieved more than I expected with just the pair of 2-stacks. It's the same old diminishing returns issue. Yes, more is an improvement, but is it worth the effort, expense, and complexity? The answers are yes, maybe, yes. The sub line array will be a really fun experiment! |
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Post by fbczar on Feb 25, 2022 22:03:13 GMT -5
I own two DXD 12012’s and wish I had two more so I could stack two sets! They are also impressive when not stacked. Very quick sounding and exceptional for music. I plan to use them with a pair of Magneplanar 3.7i’s. It should be interesting. In stacks of two, the subs are address room modes because of the height of the subs. I would imagine a stack of four would be eye opening. How significant the sound difference between stacked and not? I just realized that these already discontinued for dxd 12012 and dxd 808. Because I also interested to try this KK subwoofer. I can get 4 dxd 808 used one. What do you think? The DXD12012 is much more powerful than the 808. the 12012 has two 12' drivers vs the 808's two 8" drivers. However, they do work in the same manner. it depends on the size of your room and how low you require the subwoofer to play. Stacking creates a 6db boost so it does have has significant impact. However, it is possible to achieve a somewhat similar co-location effect depending on your room so stacking is not critical. If you had four 808 and created two stacks of two or one stack of four they could be pretty serious. What main speakers would you be using them with? |
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Post by leonski on Feb 25, 2022 23:15:01 GMT -5
Before building a subwoofer skyscraper? Read the WhiePaper from Harman International.......These guys did a LOT of work www.harman.com/documents/multsubs_0.pdfThe object is not necessarily the 6db boost of stacking, but to EVEN OUT the response across the listening area. If you are concerned with a Single Seat? Stack to your hearts content. |
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Post by p4t on Feb 26, 2022 9:25:51 GMT -5
How significant the sound difference between stacked and not? I just realized that these already discontinued for dxd 12012 and dxd 808. Because I also interested to try this KK subwoofer. I can get 4 dxd 808 used one. What do you think? + fbczar ttocs As ttocs and I have discussed the stacked sub idea over the past few months, I've wondered if this technique works in rooms the way it does in sound reinforcement. I researched a bit and didn't find much on using it in rooms. But the reason I wonder is that with bass wavelengths being so long there might not be enough "room in a room" for the lobes to settle out into the predicted response. That's not to say it wouldn't do anything ... ttocs has made it work after a lot of experimentation. But in sound reinforcement the goals are different ... trying to put a cancellation node on the stage so as not to explode the performers, and then uniformly spreading bass over a distance in a such a way that its not 140db 20ft from the stage in order to get 95db 150ft back. Just sayin' Hi Marcl. What I mean is, I am very curious how the sound character of of this sub, because the way this subs design for stacking. Especially the sound character when 4 of these subs stacked. |
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Post by marcl on Feb 26, 2022 9:48:02 GMT -5
+ fbczar ttocs As ttocs and I have discussed the stacked sub idea over the past few months, I've wondered if this technique works in rooms the way it does in sound reinforcement. I researched a bit and didn't find much on using it in rooms. But the reason I wonder is that with bass wavelengths being so long there might not be enough "room in a room" for the lobes to settle out into the predicted response. That's not to say it wouldn't do anything ... ttocs has made it work after a lot of experimentation. But in sound reinforcement the goals are different ... trying to put a cancellation node on the stage so as not to explode the performers, and then uniformly spreading bass over a distance in a such a way that its not 140db 20ft from the stage in order to get 95db 150ft back. Just sayin' Hi Marcl. What I mean is, I am very curious how the sound character of of this sub, because the way this subs design for stacking. Especially the sound character when 4 of these subs stacked. Yes I think the idea is interesting for two reasons .... the idea of a nearly line source because you could stack four or five in an 8ft ceiling; and that the 808 is 8" drivers which should have less inertia than 12" or larger drivers. Quite a lot of money for four 808's and you'd want two stacks, right? And the Harman principles still apply ... you'd put the stacks front and rear, not left and right (I know, I said it, but nobody would do that ) To the idea of a stack of smaller drivers .... a couple years ago I heard a demo of a concept that Magnepan has been working on, the "30.7 for condos". The 30.7 has huge planar woofers, but this concept used open baffle woofer modules that were about 3ft tall and triangular (apex toward the front and open back) with four 7" drivers on each face, a 1000W amp, and DSP to smooth it out. Paired with a 4x1ft Magnepan midrange with ribbon tweeter, this 3ft tall module sounded as good or better than the $30,000 6 1/2x4ft 30.7. So in an acoustically small room (where we all live) I could see a stacked solution with smaller drivers, and maybe even better ... open baffle design. The key with stacking those 808's would be getting the DSP right as - from what I could find on the subject from sound reinforcement - there's a specific way phase has to be handled at each level off the floor. + ttocs |
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Post by msimanyi on Feb 26, 2022 10:00:10 GMT -5
marcl I’m envious that you had a chance to hear those! I’m holding off on replacing my main speakers, hoping those come to the product line when we’re over the worst of Covid.
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Post by marcl on Feb 26, 2022 10:24:14 GMT -5
marcl I’m envious that you had a chance to hear those! I’m holding off on replacing my main speakers, hoping those come to the product line when we’re over the worst of Covid. It was very fortunate. A snowy week night and I drove an hour and a half to North Jersey with a friend. Very small room in an old building that the dealer had. Front half FILLED with Vicoustic Multifusers, also on the back wall, and wooden 1D diffusers on the front wall ... no bass traps that I could see. Wendell had his usual white curtain up so we wouldn't be distracted by anything but the sound. He did let us look behind, briefly. Steve Guttenberg, Jules Coleman and Herb Reichert got the first demo so Steve could record an episode of his podcast. The rest of us got to eat the pizza while we waited. No official announcement, but I have heard rumors that the concept has progressed. I have a theory - totally unconfirmed - that maybe the reason Magnepan is on the exhibitor list for the April AXPONA MIGHT be ... www.youtube.com/watch?v=AzPBz3SOT4Awww.enjoythemusic.com/magazine/equipment/0120/Magnepan_307_Panel_Loudspeakers_For_Condos_Review.htmp.s. I was mistaken, the mid-tweeter panel was more like 6ft tall. p.p.s in the photo of guys sitting on the couch talking with the store owner, you'll see me with the black shirt and white hair and beard  |
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Post by fbczar on Feb 26, 2022 17:03:53 GMT -5
Hi Marcl. What I mean is, I am very curious how the sound character of of this sub, because the way this subs design for stacking. Especially the sound character when 4 of these subs stacked. Yes I think the idea is interesting for two reasons .... the idea of a nearly line source because you could stack four or five in an 8ft ceiling; and that the 808 is 8" drivers which should have less inertia than 12" or larger drivers. Quite a lot of money for four 808's and you'd want two stacks, right? And the Harman principles still apply ... you'd put the stacks front and rear, not left and right (I know, I said it, but nobody would do that ) To the idea of a stack of smaller drivers .... a couple years ago I heard a demo of a concept that Magnepan has been working on, the "30.7 for condos". The 30.7 has huge planar woofers, but this concept used open baffle woofer modules that were about 3ft tall and triangular (apex toward the front and open back) with four 7" drivers on each face, a 1000W amp, and DSP to smooth it out. Paired with a 4x1ft Magnepan midrange with ribbon tweeter, this 3ft tall module sounded as good or better than the $30,000 6 1/2x4ft 30.7. So in an acoustically small room (where we all live) I could see a stacked solution with smaller drivers, and maybe even better ... open baffle design. Check this link: www.avforums.com/reviews/kreisel-sound-dxd-12012-and-quattro-stack-review.388The key with stacking those 808's would be getting the DSP right as - from what I could find on the subject from sound reinforcement - there's a specific way phase has to be handled at each level off the floor. + ttocs Relative to phase for the Kreisel 808's, each sub has a series of of default settings that should be used when stacking the subs. You can see this in the Kreisel literature and in the manuals that are downloadable. Anyway, the setup for a stack could not be more simple. The Kreisel stack should be EQ's as if it were one subwoofer. Please note the 808's fire from one side and from the bottom and are a push /pull design. They are inverted relative to each other as they are stacked. Check This link: www.avforums.com/reviews/kreisel-sound-dxd-12012-and-quattro-stack-review.388 |
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Post by leonski on Feb 26, 2022 17:42:38 GMT -5
Lots of info at the Kreisel site, not all of which I agree with.
No mention made of ISOBARIC which is the starting point for these kinds of designs......
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ttocs
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Post by ttocs on Feb 26, 2022 19:37:18 GMT -5
Lots of info at the Kreisel site, not all of which I agree with. No mention made of ISOBARIC which is the starting point for these kinds of designs...... This particular design is not ISOBARIC. Both drivers push outward together, and pull inward together. The internal air volume is not a constant pressure or volume. The drivers are inverted from each other relative to the box, but the phase is also inverted relative to each other. So one is in a forward motion, and the other is in reverse, hence, why both move out together and in together. If you look at the animation you can see the action of both drivers (you may need to click it to see the animation).  |
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