I recall seeing a Tectonic video where they talk about how the center area between the exciters helps the response by making it act like a larger version of the central area or an exciter, which is what provides the initial transient information. So as they explained it, multiple exciters are beneficial in their design. Of course they have to use multiple exciters to get the power needed, and they would highlight any benefit and maybe not discuss the drawbacks as much.
But one thing I found really spectacular when setting them up in all four corners of the dancefloor is how I could hear the stereo image even when standing very close to one stack, which doesn't really happen with normal speakers. I think that it is possible that effect is more pronounced when multiple exciters, and should then be apparent as better imaging also when using home listening levels.
But one thing I found really spectacular when setting them up in all four corners of the dancefloor is how I could hear the stereo image even when standing very close to one stack, which doesn't really happen with normal speakers. I think that it is possible that effect is more pronounced when multiple exciters, and should then be apparent as better imaging also when using home listening levels.
I beg to differ less speakers equals less room reflections/nodes More speakers equals more room reflections/nodes. Its easier to dial in a pair of speakers then it is multiple pairs. In fact the speaker with the least amount of room nodes/reflections is a "SINGLE MONO SPEAKER".
More exciters used on a single panel the MORE interaction while less exciters used less interaction between waves and you cant get any less interaction then a single exciter.
My main goal with building DML's is high fidelity everything else is secondary. Most single exciters can get pretty loud enough to fill a decent sized room. If you have a really large room and or want concert level volumes then yea multiple exciters is the way to go. The reason why Tetonic uses multiple exciters is because they cater to live CONCERT performances. So if your main goal is live concert performances then it should be suitable for that need. For high fidelity that is different catagory.
Now I am not saying that using multiple exciters on the same panel diaphragm cant or wont sound good as they can sound pretty darn good if built/designed correctly but when using just one exciter per panel its just a bit better in coherency/clarity/detail.
I have tried to many configurations to remember but if I had to guess roughly around 60 different configurations with at most 4 exciters per panel. So far multiple exciters on the same panel cannot beat a single exciter panel when it comes to coherency and detail. Multiple excites on the same panel will play louder and sound fuller but due to comb filtering it loses some coherency and detail.
There are choices which include multiple separate panels with a single exciter on each panel like a 2-4 way or line array. EQ/DSP can also be used to fine tune the sound.
More exciters used on a single panel the MORE interaction while less exciters used less interaction between waves and you cant get any less interaction then a single exciter.
My main goal with building DML's is high fidelity everything else is secondary. Most single exciters can get pretty loud enough to fill a decent sized room. If you have a really large room and or want concert level volumes then yea multiple exciters is the way to go. The reason why Tetonic uses multiple exciters is because they cater to live CONCERT performances. So if your main goal is live concert performances then it should be suitable for that need. For high fidelity that is different catagory.
Now I am not saying that using multiple exciters on the same panel diaphragm cant or wont sound good as they can sound pretty darn good if built/designed correctly but when using just one exciter per panel its just a bit better in coherency/clarity/detail.
I have tried to many configurations to remember but if I had to guess roughly around 60 different configurations with at most 4 exciters per panel. So far multiple exciters on the same panel cannot beat a single exciter panel when it comes to coherency and detail. Multiple excites on the same panel will play louder and sound fuller but due to comb filtering it loses some coherency and detail.
There are choices which include multiple separate panels with a single exciter on each panel like a 2-4 way or line array. EQ/DSP can also be used to fine tune the sound.
DML panels are not fixed baffles.This is an important issue.
One does not have the same problems with DML panels as one has with pistons in fixed baffles.
Pistons invariably have problems with combing, incoherence and lobing with multiple drivers in a fixed baffle. This is unavoidable. Also, a pistonic source MUST have smaller dimensions than the wavelength it is reproducing in order to prevent beaming. Again, this is unavoidable because of the physics involved. It has nothing to do with the quality of the driver.
Multiple pistons in fixed baffles is like shining a projector through multiple holes onto a screen. By the laws of physics, diffraction interference and phasing is unavoidable.
DML does not work like this.
The whole DML panel produces the sound. I see some people battle to understand the concept that the whole panel produces bending waves. It's not a piston!
DML creates diffuse waves with multiple modes. Modes. This means that it's not a simple "ripple-in-a-pond" effect either. Every signal results in chaotic peaks and dips all over the panel. And if it does not do this then it's not DML.
There is no coherent wave-front that propogates from the panel surface. Therefore, there are no phasing and interference issues. The air molecules do not move back-and-forth as they would if driven by a piston, and there can be no diffractions which cause combing.
For this reason, no matter how many drivers are on the panel, the whole panel acts like an acoustic point source. It's not like a projector shining through holes in a grating. it's more like a hologram. One hears the same, point source signal all over the panel.
This can be confirmed by placing your ear next to one end of the panel while scratching the other end with a fingernail. The scratching sound is (should be!) the same all over the panel and cannot be aurally localised. You won't know where the fingernail is scratching if you cannot see it, the sound source will appear to be exactly wherever the ear is placed.
If the panel does not produce this characteristic, then it is probably overdamped.
Multiple drivers cannot cause combing in a DML panel. The perception of "combing" is a misconceptual hangover from issues with pistons in fixed baffles.
Further, comb filtering just cannot be resolved with 1/3rd-octave measurements.
The peaks and dips in the response that appear to move up and down the frequency band with different driver positions are to do with panel resonances and improperly placed drivers, and improper activation of modes. Not combing.
One does not have the same problems with DML panels as one has with pistons in fixed baffles.
Pistons invariably have problems with combing, incoherence and lobing with multiple drivers in a fixed baffle. This is unavoidable. Also, a pistonic source MUST have smaller dimensions than the wavelength it is reproducing in order to prevent beaming. Again, this is unavoidable because of the physics involved. It has nothing to do with the quality of the driver.
Multiple pistons in fixed baffles is like shining a projector through multiple holes onto a screen. By the laws of physics, diffraction interference and phasing is unavoidable.
DML does not work like this.
The whole DML panel produces the sound. I see some people battle to understand the concept that the whole panel produces bending waves. It's not a piston!
DML creates diffuse waves with multiple modes. Modes. This means that it's not a simple "ripple-in-a-pond" effect either. Every signal results in chaotic peaks and dips all over the panel. And if it does not do this then it's not DML.
There is no coherent wave-front that propogates from the panel surface. Therefore, there are no phasing and interference issues. The air molecules do not move back-and-forth as they would if driven by a piston, and there can be no diffractions which cause combing.
For this reason, no matter how many drivers are on the panel, the whole panel acts like an acoustic point source. It's not like a projector shining through holes in a grating. it's more like a hologram. One hears the same, point source signal all over the panel.
This can be confirmed by placing your ear next to one end of the panel while scratching the other end with a fingernail. The scratching sound is (should be!) the same all over the panel and cannot be aurally localised. You won't know where the fingernail is scratching if you cannot see it, the sound source will appear to be exactly wherever the ear is placed.
If the panel does not produce this characteristic, then it is probably overdamped.
Multiple drivers cannot cause combing in a DML panel. The perception of "combing" is a misconceptual hangover from issues with pistons in fixed baffles.
Further, comb filtering just cannot be resolved with 1/3rd-octave measurements.
The peaks and dips in the response that appear to move up and down the frequency band with different driver positions are to do with panel resonances and improperly placed drivers, and improper activation of modes. Not combing.
Team DiyAudio
Noob here.
Feel like i hit the jackpot finding this.
For guitar practice, Im looking to build small ~(6x8inch) dml speakers that will fit in my guitar gig bag and am in search of a substrate.
Doesn't have to be 80hz-20khz...
Would a thin aluminum sheet do the trick? acrylic?
I've already built the mini preamp, usb c power delivery, power bank and dayton exciters.
Sounds good on pillows.
Thank you SO much!
Noob here.
Feel like i hit the jackpot finding this.
For guitar practice, Im looking to build small ~(6x8inch) dml speakers that will fit in my guitar gig bag and am in search of a substrate.
Doesn't have to be 80hz-20khz...
Would a thin aluminum sheet do the trick? acrylic?
I've already built the mini preamp, usb c power delivery, power bank and dayton exciters.
Sounds good on pillows.
Thank you SO much!
If I place me ear next to the panel I can always hear and find where the exciter is located. The further away me ear is from the panel the harder it is to locate the exciters position. I have done this with damped and undamped panels. I believe Spedge can do this also as he has very good ears.
What does the improper activation of resonance modes do? Does it produce peaks and dips? If so they are either being cancelled (dips) or amplified (peaks). Is that not combing?
So which multiple exciter placement produces no improper modes?
How much sound volume do you need?
Are you miking up your amp, or are you playing raw?
Keep in mind that the distortion characteristics of the driver might not allow you to overdrive it much. But I'd be interested in hearing what a DML panel does to a guitar sound. A 6x8" panel of any material might sound very bright.
Rules-of-thumb: the lighter the substrate, the louder it will be. Soft & Floppy=more bass. Stiff=more treble.
If you are measuring indoors then you are going to get much more combing as a result of room reflections than from anything on the panel itself.
The peaks and dips one sees in panel measurements are due to panel resonances, and not phase cancellations. Combing is the result of the phase interference of two waves impinging on each other, and results from two (or more) longitudinal waves alternately adding and subtracting their amplitudes.
Again, DML drivers and panels do not operate in pistonic mode. Therefore the (bending) waves across a DML panel are transverse waves which cause the panel to vibrate in random, chaotic patterns and modes. They have uncorrelated phases which are almost completely immune to phase interference.
Improper placement of a single driver on a panel might, for example, activate only the even modes if placed in one specific position, or only the odd modes if placed in another specific position. And both positions will independently produce peaks and dips when driven by a single driver. But if two drivers are employed at the same time, one activating the even modes, and the other the odd modes, then a better mode spread is achieved and specifically does not cause "combing."
Ok, then your view is contrary to my experience and what I learned when studying sound engineering. Yes, there are more reflections, but there will be less reflections that are not masked by direct sound, so listener will experience less of the longer reflected delays, which will sound cleaner.
So you do not have any issues that you noticed in measurements when using mutliple exciters?
And I am using 16 plates in total with 4 exciters each for a danceflor setup. I wouldn't like to split that up to 64 plates to possibly gain a little fidelty that obviously is too small for me to notice
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Andre and leob.
The sound on a dml panel will always be louder in front of the exciter coil area.
This is the primary drive area ,the first pulse area, this is pistonic in nature and is what drives the first wave through the panel.
If there is a second exciter on the panel these waves will collide with the waves from the second exciter before they reach the edge of the panel causing comb filtering.
I see no problem using multiple exciters for PA pro use ,it makes sense, but for home use it is not necessary and for me not desirable.
It is easy to hear the difference in the small rooms that we have in our homes.
Steve.
The sound on a dml panel will always be louder in front of the exciter coil area.
This is the primary drive area ,the first pulse area, this is pistonic in nature and is what drives the first wave through the panel.
If there is a second exciter on the panel these waves will collide with the waves from the second exciter before they reach the edge of the panel causing comb filtering.
I see no problem using multiple exciters for PA pro use ,it makes sense, but for home use it is not necessary and for me not desirable.
It is easy to hear the difference in the small rooms that we have in our homes.
Steve.
Leob.
You mentioned pond size being a problem ?.
I have made 8ft panels and as small as 4inch panels.
The main difference is the low frequency XO .
The 4inch panel could only go down to about 500hz or 600hz ,I can't remember exactly which.
But with my TLs filling in the frequencies below this they filled the room with sound perfectly.
It all depends on what you want your panel to do ,and what environments it will be playing in.
As you say in another post , tectonic enlarge there primary drive area, but what they do not mention is that they are also enlarging the oil can area also.
I can see this problem in their frequency response measurements.
In their video they do mention using the oil can affect in the centre of the coil to help the response ?
I always try to reduce this effect as much as possible, but it may be useful for PA use?
Steve.
You mentioned pond size being a problem ?.
I have made 8ft panels and as small as 4inch panels.
The main difference is the low frequency XO .
The 4inch panel could only go down to about 500hz or 600hz ,I can't remember exactly which.
But with my TLs filling in the frequencies below this they filled the room with sound perfectly.
It all depends on what you want your panel to do ,and what environments it will be playing in.
As you say in another post , tectonic enlarge there primary drive area, but what they do not mention is that they are also enlarging the oil can area also.
I can see this problem in their frequency response measurements.
In their video they do mention using the oil can affect in the centre of the coil to help the response ?
I always try to reduce this effect as much as possible, but it may be useful for PA use?
Steve.
Canvas panels like artists use to paint on is a good choice. They're light, readily available (like at Walmart) and inexpensive. Be sure to coat it front and back with a 50:50 mix of school glue and water. You can substitute thinned (with water) acrylic paint for the glue. A mix of 1:3 or 4 is good. Cut a thin wooden rounded piece of wood like paneling to glue the exciter to. Glue it to the canvas center with the school glue full strength. A spline is very helpful to keep the canvas from stretching due to the exciter weight. If the canvas does stretch, dampening it with water with restore it to tautness. Spedge reports that gluing the bottom of a drink can to the front center improves mid to high freqs.
directly from effects/preamp 3.5mm output to amp into exciters. Minimalist setup.
need something super flat to slide into case.
I have this all setup and it works and sounds great on my couch pillow!
just need the flat substrate to travel with in guitar case!
Thank You!
Please show us the SPL curves that compare the sound in front of the exciter area to the sound, say, halfway to an (over-damped??) edge. And then do the same for damped edges, and then for undamped edges.
I suspect that only those panels which are incorrectly damped, and with exciters incorrectly placed (on the centre node) will exhibit such a phenomenon.
Keeping in mind that the speed of a bending wave over the surface of a DML panel increases with frequency, please tell us what is the difference in the size of the "first pulse area" at, say 100hz, compared to the size of the "first pulse area" at, say, 10khz.
Where can we find more information regarding this "first pulse area"?
No. I'm afraid that's not how DML works.
If it was true then any single exciter will cause comb filtering with itself when "colliding" with its own reflected waves from panel edges.
frubdoo.
sorry for the delay i have been having problems with my phone and the computer as usual did an update and crashed.
this panel is 11inches x 9inches ,i used a brick wall OX at 100hz to block any low frequencies .
i would use the points i have placed the weights to mount the spine ,probably just the two large weights(areas) will do.
this would be the cheapest and easiest to build for testing and probably more robust than the canvas panel suggested by jaxboy.
but you could always glue it to a panel if more LF is needed t a later date ?
the dog started barking ,but i decided to leave it in as it gives more of an idea as to the volume.
this is the left channel only so may sound a little odd?
it would be interesting to know how you get on, and if it is successful ,which ever type of panel you choose to do.
steve.
sorry for the delay i have been having problems with my phone and the computer as usual did an update and crashed.
this panel is 11inches x 9inches ,i used a brick wall OX at 100hz to block any low frequencies .
i would use the points i have placed the weights to mount the spine ,probably just the two large weights(areas) will do.
this would be the cheapest and easiest to build for testing and probably more robust than the canvas panel suggested by jaxboy.
but you could always glue it to a panel if more LF is needed t a later date ?
the dog started barking ,but i decided to leave it in as it gives more of an idea as to the volume.
this is the left channel only so may sound a little odd?
it would be interesting to know how you get on, and if it is successful ,which ever type of panel you choose to do.
steve.