Hmm... I have in mind past posts about possible production variance in such kind of mic. Have a look
Good morning everyone
I have to say that my system with 4 exciters with carbon-nomex panel works well, with the right power amp a really good powersoft, having said that I used a precious and very heavy and stiff wood
so now is the time to understand if I can lighten it both in terms of thickness and perhaps in terms of density of the material itself, the question for those who have experience on systems of this type to manage high powers is if, in your opinion, how can you act if replacing the wood with another material, basically I understand that the frame is crucial but I need to make it as light as possible
I have to say that my system with 4 exciters with carbon-nomex panel works well, with the right power amp a really good powersoft, having said that I used a precious and very heavy and stiff wood
so now is the time to understand if I can lighten it both in terms of thickness and perhaps in terms of density of the material itself, the question for those who have experience on systems of this type to manage high powers is if, in your opinion, how can you act if replacing the wood with another material, basically I understand that the frame is crucial but I need to make it as light as possible
It would be off topic if I elaborated but a project. Results depend on accuracy of the design software. That suggests useful output at 25hz using the oversized box approach that extend bass with a bit of a drop - ~1.5db plateau in my case. The Dayton mic looks like it's flat to 20hz.
The other reason for the change is meaningful spl readings at any audio frequency rather than with the usual weightings. Personal interest as the usual weightings do not match current ideas of human ear equal volume levels with frequency.
Thank you for the link AjohnL. It is what I had in mind about the dispersion of this mic.I came across info like this - part way down the page
https://www.cross-spectrum.com/weblog/2009/07/
I have an interest in building a subwoofer and ideally need a mic that will go lower than the ECM8000 anyway. Testing would have to be done outdoors but I have read of another method where the mic is placed rather close to the speaker. It claims far field predicted to 1dB.
DML I want to look at aspect ratio, size and thickness of rather small panels in as many materials as I can easily get. I don't expect much in the line of a bass response.I now have as much kit as I think I need but still delayed due to a PC problem.
I have a soundblaster usb unit with ~120db dynamic range but have also bought a cheap interface by ESI, range ~100db weighted. What that means can be determined by linking it's inputs to outputs and using the software. Might be £60 wasted but on Linux it has some advantages compared with using the SB as I can't run any of creative's software.
About close mic measurement, it is a method that work well for boxed speaker. In LF, the conic loudspeaker works as a piston, meaning all the points of the membrane move same direction, hopefully same displacement. The limit of this measurement is when the pressure from the furthest points become out of phase (quarter phase). If you search more information, you can have a look to Texas Instrument SLAA641. I used it successfully with standard speakers. With DML, it can give the information of what is going on locally but not of the full result as very soon in the frequency range the points of the membrane don't go in the same direction (DML is a phase mess?). In addition, DML are larger than pistonic speakers. I have doubt also about the applicability to open back speaker. It would be probably intersting to have the feedback of experienced DIYer in OB.
Being also under Linux, I can only encourage it. There are so many technical software available. The difficulty is the one you mention when it is matter of interface. What is this ESI interface? Which Linux do you use?
Christian
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This one but as I said I haven't measured it's quality
https://www.amazon.co.uk/gp/product/B0BMM3MHYV/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
All controls are on it including a clipping indication. Linux level indicators on the SB unit would have to be calibrated to achieve that. Creatives own software will be but
I'm not a fan of their software from using it a long time ago under windows. Lots of bloat.OpenSuse for a very long time. Buying their commercial stuff from PC World started me using Linux ~25years ago. Not cost, just fed up with windows used daily at work. Later switched to the free one. I skipped a couple of releases so time to upgrade. I found some of the packages I regularly use such as the GIMP aren't stable. Installed a couple of experimental apps and had repo problems within a few days. In the past that has only happened with rather obscure stuff and fairly easy to fix maybe with a bit of help from their forum. I'm wondering about certain photo apps I use. They were maintained in Suse's repo's as was the very latest version of Wine. Easily found with their web software search. This search seems to have changed. I need to check that they still are maintained by some one. If not it looks like I will be changing distro. Ubuntu maybe but I'm a KDE user, Gnome doesn't really appeal. Suse has another way of finding software and that may produce better results for some apps as it offers backports etc. This particular search can produce results based on what the app actually does. Useful at times.
I've been a bit of an idiot. As some may be thinking of buying a calibrated mic I'll own up. You want a USB mic. That way calibrated SPL levels can be taken without complication. Go the other way via an interface things aren't so simple. A calibrator is needed to actually calibrate the sound level - another ~£100 and will need using any time the mic amp gain is changed. Rushing without some thought is often a bad idea - guilty as I want to get on with it. So I woke up this morning and had the thought rather late after buying. So far no problems with any amazon return but more delay getting a usb mic. UK's not the best place to be to buy more obscure items.It seems available usb mic's are ok on Linux.
When my mic arrived from Amazon I could have sworn it was the wrong one... so I went back and double-checked my order, and lo-and-behold I had indeed ordered an XLR, phantom-powered mic! Idiot.
So I need to order a USB mic. It's a schlep firing up a whole mixing console just so I can get phantom power and not being able to calibrate it in any way.
A USB mic would be nice but I don't really need a USB mic since I already have the M-Audio interface which is quite nice. I looked around for places that would calibrate the ECM8000 as a service but have not found much yet.
If someone wants to buy me a mic with a calibrated file I am all for it. Let me know and I'll send you my shipping information.
If someone wants to buy me a mic with a calibrated file I am all for it. Let me know and I'll send you my shipping information.
Is it so sure?
It seems available usb mic's are ok on Linux.
USB mic is easy to use. An UMIK1 USB works easily with Linux. With the last update of Linux Manjaro I use, just choose the right source in the preference menu. REW detect even automatically the mic. Only constraint is to plug the USB devices (mic, DAC) before launching REW.
So possible drawback of USB are :
- The signal to noise ratio. The mic capsule makes the performance followed by the preamp.
- In the document if I remember from Virtuix there is something about the problem of timing reference with USB. OK probably not a needed feature for DML but to have in mind.
REW mention no need to calibrate usb mics to do spl measurements in the section where they go through mic calibration.
I'm using OpenSuse 15.1 and that has been offering sound device selection on the desktop since 2019
with a catch though on USB. It may miss devices connected that way during boot but adding Pulse fixes that. If plugged in post boot it picks then up. However for this sort of work ALSA is recommended, Not one I have tried but will be.I'll miss opensuse if I change largely down to software installation but they seem to have changed how their repo's are organised which means I wont get auto updates on ones that they do not support themselves. Those go by the name official releases. They have a rolling release called Tumbleweed which always offers the latest and greatest - good but it may not be completely stable. They also have an unofficial repo. I may need to use that to get the apps I need.
I don't have a clear understanding of the complete software chain working in a laptop on the audio chain so I am just cautious about how the different possible software volumes can be adjusted or even modified from one day to another one by the different apps calling them.
In Manjaro there is as I think for most of the distribution a mixer available but since recently, it seems it no more operates on the selection for REW. I am not expert enough in whole structure but changes occurred (like to new library like pipewire?).
Nevertheless, it works. Just not sure about the full volume chain is Odb. The useful tool might be an USB mic in calibrator. Something like a mic from USB point of view but sending a fixed defined signal.
@AjohnL
About USB mic on REW...
thank you for this exchange AJohnL. Thanks to it, I have verified what is in REW manual for USB mic (long time without going into it...) and so the "volume control" option that would set the volume chain at the desired value. The effect is visible in the desktop mixer but also in the alsamixer window that seems confirm REW is connected directly to the Alsa output not any additional software layer.
Well, I have an; old analog soundmeter in my tool box, I take note to check with it if the level readings are similar in a next measurements
About USB mic on REW...
thank you for this exchange AJohnL. Thanks to it, I have verified what is in REW manual for USB mic (long time without going into it...) and so the "volume control" option that would set the volume chain at the desired value. The effect is visible in the desktop mixer but also in the alsamixer window that seems confirm REW is connected directly to the Alsa output not any additional software layer.
Well, I have an; old analog soundmeter in my tool box, I take note to check with it if the level readings are similar in a next measurements
I just thought dam I need to calibrate the mic to take spl readings. Did some searches and went on to find a calibrator. A REW link popped up on calibration mentioning no need with a calibrated USB mic. Logical as it's a digital train end to end during recording other than the actual sound detector.
Need to look further but it seems Pulse hooks onto ALSA. I wouldn't be aware of that as ALSA would be pulled in when i installed Pulse. it includes a nice graphic equaliser. Also a level meter which I don't have installed. That may make it easier to use the soundblaster for testing amps into resistive loads also using it as source. A lot of the usual ALSA add ons Jack and others are aimed at bands and mixing etc. LOL They tend to look too complicated to me. My USB sound detection problems are probably down to KDE who decided to do their own sound sysrem. Was OK but when USB sound came about it had problems. It still seems to have on the latest release of my distro.
Need to look further but it seems Pulse hooks onto ALSA. I wouldn't be aware of that as ALSA would be pulled in when i installed Pulse. it includes a nice graphic equaliser. Also a level meter which I don't have installed. That may make it easier to use the soundblaster for testing amps into resistive loads also using it as source. A lot of the usual ALSA add ons Jack and others are aimed at bands and mixing etc. LOL They tend to look too complicated to me. My USB sound detection problems are probably down to KDE who decided to do their own sound sysrem. Was OK but when USB sound came about it had problems. It still seems to have on the latest release of my distro.
Thankyou . thats a good bit of hunting.
I didnt see those new posts , but i have picked up 3mm Poplar ply and 1.8 mm Sassafras to do some testing with and also a sheet of Bunnings sourced 10 mm thick / 20 kg3m EPS.
Do you have a clear assembly strategy with the 28 kg3M EPS or still in the stage of manual evaluation so you can map out the design around the initial performance ?
My anticipated framing method for the EPS to get a reasonable visual aesthetic as per sectional drawing below , 6 mm foam glued to the EPS and the quarter round pine trim , quarter round glued and nailed to the 65 x 19 framing.
That framing should work well and will look nicer than setting it on the top edge. And if you decide to clamp both sides of the EPS later on (some do) you can still do it. Be sure there is a nice gap between the edge of the EPS and the inside face of the pine. I'd want something like 3-5mm. I would also make a couple of minor tweaks to the wood, like rounding the edges in red (see below). It is not necessary, just a hedge against edge rubbing and splintering/flaking.
I would also recess the EPS well below the top edge of the pine so the pine frame can be wrapped with speaker cloth later on without the risk of the cloth interfering with the EPS.
I would also recess the EPS well below the top edge of the pine so the pine frame can be wrapped with speaker cloth later on without the risk of the cloth interfering with the EPS.
Goldmund,
Yep. But I assume you mean as the core of a sandwich composite with fiberglass or carbon fiber skins, rather than nomex alone. Nomex alone has virtually no stiffness.
But CF(carbon fiber)/nomex is probably among the best materials to use for DML panels. Tectonics sells DML speakers made with CF/nomex sandwich panels.
For DIY It's hard to find sources of such composites that are not too thick and stiff for DML use, and they are expensive. But pixel1 is using a carbon/nomex sandwich composite that he bought online and seems to be about the right stiffness, and thickness. You can also make one yourself if you have the skills.
Eric
Earborne,My anticipated framing method for the EPS to get a reasonable visual aesthetic as per sectional drawing below , 6 mm foam glued to the EPS and the quarter round pine trim , quarter round glued and nailed to the 65 x 19 framing.
I like it. That's basically the same framing method I used for this pair, only I routed the inside corner rather than add the quarter round. I think recessing the plate a bit like Deude suggested is a good idea to protect the plate (especially if its PS).
What foam are you planning to use?
Eric
