Nicolas ojala
This recording on page 180 was made on my surround sound system with the front speakers replaced with small card panels.
The sound was amazing, sounding so realistic.
Steve.
Hello Christian.
I treat every type of panel differently, I cannot generalise as to the sound or response of varying dml panels.
The same is for bending wave, bmr, and dml ,with all the problems of bleed through from one type to another .
It all starts from pistonic action in the coil area, I use all of these three modes to produce the best possible panels.
Different methods are used to tame different panels and types of panels.
It all depends on what you are trying to achieve.
A used to use pink noise and music to find the best places for exciter mounting.
But now I either place the exciter in the NXT position or the centre, depending on the panel.
Supposedly the NXT position gives a good spread of modes with a good central position, which I prefer mostly, depending on panel size.
Steve.
I treat every type of panel differently, I cannot generalise as to the sound or response of varying dml panels.
The same is for bending wave, bmr, and dml ,with all the problems of bleed through from one type to another .
It all starts from pistonic action in the coil area, I use all of these three modes to produce the best possible panels.
Different methods are used to tame different panels and types of panels.
It all depends on what you are trying to achieve.
A used to use pink noise and music to find the best places for exciter mounting.
But now I either place the exciter in the NXT position or the centre, depending on the panel.
Supposedly the NXT position gives a good spread of modes with a good central position, which I prefer mostly, depending on panel size.
Steve.
Hello Eric,
Good reading! The methods described by both papers (BMR vs Biphonic) are different... In BMR, the mass are at nodal lines starting by the highest mode as you pointed it while in the Biphonic patent, it is at anti-nodes of the frequency (which is low) that creates the dip in the FR (anti-resonance in the text).
Well.. the link between both is not created...
From M Cohen's patent :
Mister Audio,
Where does your 395 Hz Fs come from? The spec sheet for that exciter reports 160 Hz for Fs.
I agree that a subwoofer is warranted in combination with most DML's. But that said, I don't think you can interpret the stated Fs figure for an exciter the same way as you would interpret it for a conventional cone speaker. As you correctly pointed out, the panel mass (and stiffness and mounting) will influence Fs, but perhaps a lot more than you might expect! In fact, I've found that all the 20-ish watt DA exciters behave similarly, that is, exhibiting an "Fs" of 20-40 Hz when mounted to an actual plate, despite a stated Fs (spec sheet) in the range of 200 Hz.
The 32u and similar Dayton exciters can easily produce strong and undistorted bass down to 50 Hz and perhaps lower. In my experience with DML, the resonance that determines the bottom end of the frequency range is generally not that of the exciter, but rather that of the fundamental frequency of the panel, as mounted. The real (and fun) challenge in designing a good DML (in my mind, anyway), is finding a way to get smooth bass response starting from the panel's fundamental though the next four octaves or so.
Eric
This is my spec. information.
As I haven't yet built my first DML , I was guessing that Fs with panel might get down to
perhaps 200Hz, but I was purely guessing. I'll have to wait and see what I measure. 🙂
As I haven't yet built my first DML , I was guessing that Fs with panel might get down to
perhaps 200Hz, but I was purely guessing. I'll have to wait and see what I measure. 🙂
How exactly does one find this frequency? I've seen some complicated suggestions throughout this epic thread, but is there a concise method?
I've built DMLs with 3/32" aircraft basswood ply, 24" x 24" & 12x12" ... they sound good! (still need sub). But I'm struggling to find the right support structure -- I'd like to keep them open like Spedge's but this means a hanging installation, which isn't ideal for me.
As my parts & equipment (some on back order) slowly come together for my DML's
I will post description and weight of the panel, both without and with the twin exciters.
I will also post impedance/resonance information.
Re. the support of my panels >
The top is going to be HUNG - basically using ladies flexible hair-ties. (x2)
However, the bottom is to be restrained & controlled (anti-flap) by 2 long rubber strips.
(note: there will be an open baffle 12" woofer below my panels)
The 2 long rubber strips, roughly 550mm long, will go down to the 'base plate'.
I will post description and weight of the panel, both without and with the twin exciters.
I will also post impedance/resonance information.
Re. the support of my panels >
The top is going to be HUNG - basically using ladies flexible hair-ties. (x2)
However, the bottom is to be restrained & controlled (anti-flap) by 2 long rubber strips.
(note: there will be an open baffle 12" woofer below my panels)
The 2 long rubber strips, roughly 550mm long, will go down to the 'base plate'.
You could hang them from a clothes rack like these. Or make your own frames.
https://www.walmart.com/ip/Oukaning...1?wmlspartner=wlpa&selectedSellerId=101001636
Hello Monosuna,
I don't know such a method. There are trials in this thread to approach some elements and to build a more technical approach but nothing mature enough. From the elements I see, even if such method exists, it wouldn't be very simple as the main drivers are the characteristics of the panel material which cant be provided. There are too big differences in what is locally supplied.
You have 2 options. The hanging method that keeps free the panel. I have no experience on it but I think you can find some inspiration from other realizations (see here the answer from twocents or on youtube). I have made the choice for now for a more mechanically secure way which is a frame and a suspension like a weather strip.
Christian
@monosuna, the other way would be to fix the panels to some base along the bottom edge. See Burntcoil's Tall Blondes post #1165.
Seeing that you are into ambient music, have look at these DML panels:
Seeing that you are into ambient music, have look at these DML panels:
@twocents yes I remember that installation posted here waaaay back! This is pretty similar to my current setup, which uses 8" aluminum "stand-offs" clamped on the bottom two corners & placed on floor. Seems the best compromise so far.
DML is great for ambient & piano music imo. I've been picking my piano tuner's brain about the acoustics of piano soundboards -- he claims that the (usually maple) hardwood ribs help distribute the resonances evenly across the spruce soundboard. I can't recall if someone here has tested ribs like that?
DML is great for ambient & piano music imo. I've been picking my piano tuner's brain about the acoustics of piano soundboards -- he claims that the (usually maple) hardwood ribs help distribute the resonances evenly across the spruce soundboard. I can't recall if someone here has tested ribs like that?
Twocents.
I too would, and have mounted ply panels in this way especially if they were tall ,like the ones in the video.
I would also have an angle at the bottom to stop the low frequency resonance from bouncing up and down forever and a day and probably at the top as well.
Obviously only if you are using the panels down into those frequencies.
I have posted this type of panel with frequency responses somewhere on this forum.
Interesting video 👍
Steve.
I too would, and have mounted ply panels in this way especially if they were tall ,like the ones in the video.
I would also have an angle at the bottom to stop the low frequency resonance from bouncing up and down forever and a day and probably at the top as well.
Obviously only if you are using the panels down into those frequencies.
I have posted this type of panel with frequency responses somewhere on this forum.
Interesting video 👍
Steve.
Soundimports have a new 40w exciter from a new brand: https://www.soundimports.eu/en/xcite-xt32-4.html
Leob.
I wonder how they got the Fs of 40hz?
That exciter also seems to have a plastic housing, which through past experience I would be a little hesitant about.
Steve.
I wonder how they got the Fs of 40hz?
That exciter also seems to have a plastic housing, which through past experience I would be a little hesitant about.
Steve.
It is presented with a lot of hyperbole, but I'm also not sure what is so great about it. No mounting hole is also a concern.
But interesting with a new manufacturer which at least on the surface looks like it is not one of usual designs from the regular Chinese suppliers.
But interesting with a new manufacturer which at least on the surface looks like it is not one of usual designs from the regular Chinese suppliers.
Steve,
Note that they actually report two different results for Fs: 40 Hz under the heading "Magnet" and 312 Hz under the heading "Coil". I suspect strongly that they got the "Magnet" result by holding the voice coil fixed and letting the magnet move freely, while the "Coil" result they got by fixing the magnet and letting the voice coil move freely.
I get similar results when I test the Dayton exciters those two ways. For example, the plots below shows my two tests on a DAEX25VT-4, where the Fs (impedance peak) is around 36 Hz with the magnet free, and 213 hz with the voice coil free.
Interestingly, Dayton Audio specs only ever report the higher (voice coil free) result. But my own experience is that the lower (magnet free) result is more meaningful as an indicator of how low it's possible to go with a particular exciter. For example, (with the right panel and mounting) I can definitely get strong SPL output down to 50 Hz (maybe less) with the VT-4, which is a lot closer to 36 hz than it is to 213 Hz.
Eric
Note that they actually report two different results for Fs: 40 Hz under the heading "Magnet" and 312 Hz under the heading "Coil". I suspect strongly that they got the "Magnet" result by holding the voice coil fixed and letting the magnet move freely, while the "Coil" result they got by fixing the magnet and letting the voice coil move freely.
I get similar results when I test the Dayton exciters those two ways. For example, the plots below shows my two tests on a DAEX25VT-4, where the Fs (impedance peak) is around 36 Hz with the magnet free, and 213 hz with the voice coil free.
Interestingly, Dayton Audio specs only ever report the higher (voice coil free) result. But my own experience is that the lower (magnet free) result is more meaningful as an indicator of how low it's possible to go with a particular exciter. For example, (with the right panel and mounting) I can definitely get strong SPL output down to 50 Hz (maybe less) with the VT-4, which is a lot closer to 36 hz than it is to 213 Hz.
Eric
monosuna,
Actually, yes, there is a simple way to find this frequency, assuming you have a microphone and a spectrum analyzer (like REW or similar). Typically, all you have to do is place your mic close to the panel (within a few millimeters ideally) near the center of the panel surface, then give the panel a tap (also near the center) with a striker (I use a rubber ball on the end of a stick). The spectrum analyzer will display a series of sharp peaks, each corresponding to a different natural frequency of the panel (in that mounting). The lowest frequency in the series of natural frequencies is the fundamental.
The one gotcha is that if the panel is large enough and/or thin enough, the fundamental could be lower than the mic or spectrum analyzer can detect.
In my experience, If you want to get the most bass possible from your panels, you should mount them to a sturdy frame around the perimeter using insulation foam (or similar) sandwiched between the frame and the panel. The frame can be open in the back and need not be very deep. With the right mounting foam it will also minimize SPL spikes and "ringing" that can happen at the panels natural frequencies. But if don't really need the extra bass, and don't hear or don't mind the ringing, hanging could be fine for you. Not all panels "ring" as much. Plywood panels are pretty well internally damped, and may not need damping as much as some others do.
Eric
Another way is modeling, if you have the capability (FEA software) and know or can estimate the properties of the panel well enough. The result below is what my model predicts for the fundamental frequency of a 12x12 basswood panel hanging freely. That is, 52 Hz. In this model, I assumed the elastic moduli and density of your basswood is similar to that of a 3 ply birch that I have tested. It may or may not be a good assumption.
Nice find, Leob.
The manufacturer seems to be https://xcite.eu/ , but the website is inaccessible.
In comparison to the DAEX30HESF-4 this Xcite XT32-4 driver seems pretty much similar price/power-wise. Soundimports claims it as a 35-17hz bandwidth, but they claim that the Dayton driver has a 70-20khz bandwidth! and some of us know how accurate that claim is...
Xcite XT-32 claims a 0.13mH coil inductance vs 0.31mH for the Dayton. Interesting.
The XT-32 claims a 'double magnet'?? 🤔
The XT-32 Vc has an Fs of 312Hz. But its magnet apparently has an Fs of 40.5Hz. That's weird, but it does imply a rather tight suspension, much like the DAEX Megabass (which is a waste of money IMO.)
The Fs I get out of the DAEXHESF's magnet is around 20Hz by measuring the displacement of the magnet when the voice coil is anchored to a solid surface. I wonder if that's how Xcite measured theirs.
Xcite claims "a design preventing displacements over 3.5mm ..." (7mm p-p?) Does that mean the spider limits the Vc Xmax-mech before hitting the bottom of the magnet? I've got an Xmax measurement somewhere of the 30HESF, and, fwiw, I get an absolute Xmax of 6mmp-p.
The Xcite motor depth is around 19.7mm, the DAEX30HESF motor is only 14mm deep, so there appears to be truth to the claim that the XT-32 has a better-controlled linear excursion.
When I get funding again, I'll get three of the Xcite units; two for listening tests, and one to take apart to see what's inside.