Hi,
I just ordered SoundEasy for my next loudspeaker project and I was wondering if I should get calibrated ECM8000 mic?
At the moment I use ECM8000 with a calibration file which I downloaded from internet, but is this good enough? Should I get another mic with exactly right correction file and sell this one? How big differences are possible?
And where could I get calibrated ecm8000?
I just ordered SoundEasy for my next loudspeaker project and I was wondering if I should get calibrated ECM8000 mic?
At the moment I use ECM8000 with a calibration file which I downloaded from internet, but is this good enough? Should I get another mic with exactly right correction file and sell this one? How big differences are possible?
And where could I get calibrated ecm8000?
Hi Twisted,
a calibration service is done here: http://www.content.ibf-acoustic.com/
Needing a calibrated mic or not is a matter of tollerance, needs. Said this, the generic ECM8000 calibration file is old, maybe now Behringer uses a new capsule, since thew WM60 is no more produced.
Moreover, getting a calibrated mic now doesn't mean that it will stay calibrated forever, unless it's a B&K or similar: that is you shoul calibrate it once a year.
a calibration service is done here: http://www.content.ibf-acoustic.com/
Needing a calibrated mic or not is a matter of tollerance, needs. Said this, the generic ECM8000 calibration file is old, maybe now Behringer uses a new capsule, since thew WM60 is no more produced.
Moreover, getting a calibrated mic now doesn't mean that it will stay calibrated forever, unless it's a B&K or similar: that is you shoul calibrate it once a year.
The ECM8000 is supposedly reasonably flat (+/- 1dB) around where most people crossover in a 2 way (ie. between 2 - 3KHz). Therefore for uncorrected measurement and modeling, the uncalibrated ECM8000 should be fine.
Where the ECM8000 changes is the upper (12KHz+) and lower (say sub60HZ?) frequencies. What I did was measure a well known tweeter and compared the response with what others have measured.
I then found a few calibration files and chose the one that gave the most similar measurment with the known driver.
I would like to get mine calibrated, but no service I've found around here to do it.
Hope that helps.
Cheers,
David.
Where the ECM8000 changes is the upper (12KHz+) and lower (say sub60HZ?) frequencies. What I did was measure a well known tweeter and compared the response with what others have measured.
I then found a few calibration files and chose the one that gave the most similar measurment with the known driver.
I would like to get mine calibrated, but no service I've found around here to do it.
Hope that helps.
Cheers,
David.
I'll have to agree with Dave Bullet and will go a step further.
Just how accurate do you need to be? For a home speaker builder, even an advanced one, this would seem to be flat enough through the midrange.
Do any of use think that we can really get in room bass measurements that are even close to as accurate as this mic? I doubt it.
The main question would be: "Do the mics match the published curves?" How much deviation is there from mic to mic? If it's close, I wouldn't worry much about it. Just take into account the small deviations published.
If you have an anechoic chamber along with tons of software and hardware to really measure right, you probably won't be buying this mic anyway, right?.
(Yes, I have one)
Just how accurate do you need to be? For a home speaker builder, even an advanced one, this would seem to be flat enough through the midrange.
Do any of use think that we can really get in room bass measurements that are even close to as accurate as this mic? I doubt it.
The main question would be: "Do the mics match the published curves?" How much deviation is there from mic to mic? If it's close, I wouldn't worry much about it. Just take into account the small deviations published.
If you have an anechoic chamber along with tons of software and hardware to really measure right, you probably won't be buying this mic anyway, right?.
(Yes, I have one)
Thanks for your replies!
Just by looking at the corretion file(s) I have, the corrections between 200Hz-5KHz seems to be quite small. I have one file that came with TrueRTA and other that I downloaded from internet (which was recommended and I was told it was better) but there is one big difference. The one I downloaded separately doesn't have any phase correction. How accurate the phase correction should be?
For example: I'm planning to make a delay circuit for the tweeter to match the "depth" of the drivers and phase, how much possible difference it could make in the design if I use uncalibrated mic?
I am not an expert speaker builder and this is first time I will use more computer programs in the design process (soundeasy should arrive tomorrow), but I'd really like that the measurements would be accurate, so I can be sure that I have correct data to work with.
Does anyone have any experience comparing calibrated and uncalibrated microphones and does this make any noticeable difference?
At the page claudio linked there seems to be two calibrated mics, the other one is double the price. Any quality differences between these? The more expensive one looks exactly like ECM8000 but is more expensive even without calibration.
I bought some time ago a better soundcard, M-Audio FireWire 410 which has Phantom power for my Behringer mic, how does the less expensive choice "EMM-8 Bias supplied" mic work?
I'm also planning to make a similiar dipole testing baffle which is introduced at zaph's page. How large this should be? The bigger, the lower the data is accurate, right? I've been thinking something between 1,5 to 2meters.
What about the lower frequencys? What is the best or most convenient way to do this at home or yard? Or is this possible without a closed baffle?
Just by looking at the corretion file(s) I have, the corrections between 200Hz-5KHz seems to be quite small. I have one file that came with TrueRTA and other that I downloaded from internet (which was recommended and I was told it was better) but there is one big difference. The one I downloaded separately doesn't have any phase correction. How accurate the phase correction should be?
For example: I'm planning to make a delay circuit for the tweeter to match the "depth" of the drivers and phase, how much possible difference it could make in the design if I use uncalibrated mic?
I am not an expert speaker builder and this is first time I will use more computer programs in the design process (soundeasy should arrive tomorrow), but I'd really like that the measurements would be accurate, so I can be sure that I have correct data to work with.
Does anyone have any experience comparing calibrated and uncalibrated microphones and does this make any noticeable difference?
At the page claudio linked there seems to be two calibrated mics, the other one is double the price. Any quality differences between these? The more expensive one looks exactly like ECM8000 but is more expensive even without calibration.
I bought some time ago a better soundcard, M-Audio FireWire 410 which has Phantom power for my Behringer mic, how does the less expensive choice "EMM-8 Bias supplied" mic work?
I'm also planning to make a similiar dipole testing baffle which is introduced at zaph's page. How large this should be? The bigger, the lower the data is accurate, right? I've been thinking something between 1,5 to 2meters.
What about the lower frequencys? What is the best or most convenient way to do this at home or yard? Or is this possible without a closed baffle?
I use Speaker Workshop for measurement - which uses actual measured phase as opposed to applying some sort of transform, ie. HBT.
In my case, I don't think mic phase matters. After all, if you are measuring 2 drivers with the same mic. If the same setup and mic are used, then it is the relative phase between drivers that counts.
Not sure why you want your own test baffle. If you intend to design crossovers for drivers you have selected looking at others (ie. Zaphs) or manufacturer measurements, it is best to measure drivers on the target baffle in the target enclosure.
You will then see the true effect of baffle step (in combination with the woofer you've selected) plus effects of baffle diffraction.
The size of the baffle will lower the baffle step frequency - true. However, with SpeakerWorkshop you need to gate measurements so you don't pick up room reflections which will colour the driver response. For example - to measure down to 100Hz with speaker workshop - you need a 10ms gate. This requires approx 3 meters clear in all directions (including floor and ceiling) - which in most measurement rooms is the limiting factor.
Therefore use a test baffle and enclosure if you are designing an actual crossover, or if you want to test drivers on a baffle board - be wary of room dimensions/ need for anechoic conditions.
Cheers,
David.
In my case, I don't think mic phase matters. After all, if you are measuring 2 drivers with the same mic. If the same setup and mic are used, then it is the relative phase between drivers that counts.
Not sure why you want your own test baffle. If you intend to design crossovers for drivers you have selected looking at others (ie. Zaphs) or manufacturer measurements, it is best to measure drivers on the target baffle in the target enclosure.
You will then see the true effect of baffle step (in combination with the woofer you've selected) plus effects of baffle diffraction.
The size of the baffle will lower the baffle step frequency - true. However, with SpeakerWorkshop you need to gate measurements so you don't pick up room reflections which will colour the driver response. For example - to measure down to 100Hz with speaker workshop - you need a 10ms gate. This requires approx 3 meters clear in all directions (including floor and ceiling) - which in most measurement rooms is the limiting factor.
Therefore use a test baffle and enclosure if you are designing an actual crossover, or if you want to test drivers on a baffle board - be wary of room dimensions/ need for anechoic conditions.
Cheers,
David.
Dave Bullet said:
My last speaker project was the first I designed by myself. I made a simple 2-way speaker with a waveguide.
http://koti.mbnet.fi/twisted-/kaapit1.jpg
I made measurements with ARTA and made changes by looking at the measurements and listening. I'm very satisfied with both the sound and the measurements.
Today I received a packet from partsexpress which included 4 Dayton RS180-8 drivers and SoundEasy (I also ordered the manual). I'm also going to buy Peerless HDS tweeters from local store and my next project will be 2,5-way floorstanding speakers, tweeters located between the mids.
I though that the best way would be to measure all the drivers in "infinite" baffle and make all the box/crossover simulations and design in SoundEasy, but is this false?
I was also planning that I could make my own comparisons between different drivers. I'm also into car audio, and I would also like to measure different drivers that are designed to work in a car and make comparisons.
How does Zaph make his low frequency measurements?
Here is a quote from his site: "Woofers however have to be done in two steps with close mic (1/4") and no gating, and spaced mic with gating. The gating varies depending on how close I can get the mic."
Advice would be appreciated here.
3meters would mean ~ 6meters from driver to surface and from surface to the mic, is this actually necessary with 10ms gate? (some explanation would be appreciated
)I don't understand why Zaph uses 4'x8' baffle, wouldn't 4x4 serve the same purpose?
I'd really like to everything go right from the beginning of this next project and really make all the measurements as good as I can. I don't even have any use for these speakers (or the 2-way speakers I made) I just want to learn more and more about building speakers
Twisted85 said:
It's called the near field measurement, which is spliced with the gated far field to obtain the total driver response.
For more infos on how to do it, check my home page, it's all written there. Doesn't matter I show it with Speaker Workshop, the procedure is the same, just the software is different.
claudio said:
I read about that from your homepage and from loudspeaker design cookbook.
So, even If I'd want to test 10" drivers I don't need a very big baffle. If I make a 1x1meter baffle, the bafflestep would be around 150Hz, right? And with 10" driver the upper limit with near field measurement would be around 450Hz. So I can then merge these two results?
How does near field measurement work with a driver that has phase plug?
Ok - so my calculations are a bit off, but you have to allow for the initial flight time of the signal (assuming 1m measuring distance from speaker to mic) as the "reflected" signal is already on its way.
Here goes the calcs...
Assuming speed of sound is 344m/sec:
It takes 2.9msec to travel 1m to mic
Add on 10.67msec to give Speaker Workshop a gate resulting in 512 point resolution down to 100Hz
= 13.57msec allowable reflection time (from when the signal first leaves the speaker to when it can hit the mic)
13.57msec = 4.66m distance
To find the vertical distance = assuming a = vertical distance, b = 0.5 m (halfway point between speaker and mic) and c = reflection distance) via good old a^2 + b^2 = c^2
c = 4.66m/2 = 2.33m
b = 0.5
a = ?
c^2 - b^2 = a^2
5.4289 - 0.25 = 5.1789
a = 2.27m
Therefore you need to position the speaker 2.27m above ground. A room with 4.54m ceiling height would be fine.
So my 3m wasn't too far off (but wasn't correct
Cheers,
DAvid.
Twisted85 said:
Yes, around 450Hz if mounted on a large pannel, and a 1x1 meter can be considered large, in my opinion.
It's important to have a wide overlapping range between the NF and FF curves, to better splice them together. That is, the FF should be reliable from 200-250Hz, which means a 4-5 ms of gate window.
Phase plug: just measure the mic distance starting from the plug end. The phase plug acts at high frequencies, not in the NF range.
For you new Soundeasy users the manual under the help tab will answer alot of basic questions. Also download the manual from the website. For a clear explanation of teh basics I HIGHLY recommend John Krevkovsky's (sp?) manual. Well worth the $10.
Before building a testing baffle use the diffraction modeler in SE to develop a baffle with the smoothest response. I'll post some screenshots of my baffle modelling later.
As for the mic calibration debate, I'd suggest doing it. I'll post some results of mine later also so you can see the difference.
Before building a testing baffle use the diffraction modeler in SE to develop a baffle with the smoothest response. I'll post some screenshots of my baffle modelling later.
As for the mic calibration debate, I'd suggest doing it. I'll post some results of mine later also so you can see the difference.
This is the test baffle I developed and then built:
The response is quite smooth until lower in frequency where the gating will ignore anyway. I generally merge nearfield measurement around 400Hz anyway, so the farfield is basically unaffected by the baffle.
As for teh ECM8000 mic calibration here is screenshot of mine, SPL deviation from flat (pink) and phase deviation (green):
Uncorrected there is large rise in the tweeter response that may cause someone to try to make corrections for something that isn't really there. Also high XO points for mid/tweeter could run into trouble. Or if you were using a metal cone woofer and wanted the breakup a minimum of -40s dB down, you won't really have an accurate idea of where the actual breakup really is unless you use the calibration file.
OTOH as has been pointed out, for XO work the relative phase between drivers is what is important and at least the phase is equally incorrect for all of them. For the price of calibration ($40 from Kim G for example) it's worth it for the piece of mind.
The response is quite smooth until lower in frequency where the gating will ignore anyway. I generally merge nearfield measurement around 400Hz anyway, so the farfield is basically unaffected by the baffle.
As for teh ECM8000 mic calibration here is screenshot of mine, SPL deviation from flat (pink) and phase deviation (green):
Uncorrected there is large rise in the tweeter response that may cause someone to try to make corrections for something that isn't really there. Also high XO points for mid/tweeter could run into trouble. Or if you were using a metal cone woofer and wanted the breakup a minimum of -40s dB down, you won't really have an accurate idea of where the actual breakup really is unless you use the calibration file.
OTOH as has been pointed out, for XO work the relative phase between drivers is what is important and at least the phase is equally incorrect for all of them. For the price of calibration ($40 from Kim G for example) it's worth it for the piece of mind.
Thanks for all of your replies!
I think I could build something like this:
http://koti.mbnet.fi/twisted-/baffle.jpg
The dB level would be in +/-0,5dB down to 180Hz.
If the baffle is standing on ground the driver would be only 95cm from the floor surface. How long timegate should be used (1m distance) so that the measurement would be accurate down to 180Hz? I could build a rack that lifts the baffle to upper level from the floor. The ceiling and walls aren't a problem at all.
If I could measure farfield measurements down to 180Hz and nearfield measurements would be accurate to 450Hz with 10" driver and even higher with smaller drivers, this would be more than enough to merge the responses, right? Or do I even have to get to 180Hz, would 250Hz be enough?
I don't still know what to do with the microphone. The cheaper model needs a separate preamplifier and I just got rid off UB802 when I bought a new soundcard which has phantom power supply.
I could send my ECM8000 to them to calibrate, but the cost is 32euros and I guess the shipping would cost quite a lot (back and forth). And the ECM40 is 113euros plus shipping
I received packet from partsexpress to my home after 43 hours of my order, (fastest shipping ever) but I haven't heard anything about the help files which I paid
I think I could build something like this:
http://koti.mbnet.fi/twisted-/baffle.jpg
The dB level would be in +/-0,5dB down to 180Hz.
If the baffle is standing on ground the driver would be only 95cm from the floor surface. How long timegate should be used (1m distance) so that the measurement would be accurate down to 180Hz? I could build a rack that lifts the baffle to upper level from the floor. The ceiling and walls aren't a problem at all.
If I could measure farfield measurements down to 180Hz and nearfield measurements would be accurate to 450Hz with 10" driver and even higher with smaller drivers, this would be more than enough to merge the responses, right? Or do I even have to get to 180Hz, would 250Hz be enough?
I don't still know what to do with the microphone. The cheaper model needs a separate preamplifier and I just got rid off UB802 when I bought a new soundcard which has phantom power supply.
I could send my ECM8000 to them to calibrate, but the cost is 32euros and I guess the shipping would cost quite a lot (back and forth). And the ECM40 is 113euros plus shipping
I received packet from partsexpress to my home after 43 hours of my order, (fastest shipping ever) but I haven't heard anything about the help files which I paid
Twisted85 said:
If the baffle is standing on ground the driver would be only 95cm from the floor surface. How long timegate should be used (1m distance) so that the measurement would be accurate down to 180Hz? I could build a rack that lifts the baffle to upper level from the floor. The ceiling and walls aren't a problem at all.
If I could measure farfield measurements down to 180Hz and nearfield measurements would be accurate to 450Hz with 10" driver and even higher with smaller drivers, this would be more than enough to merge the responses, right? Or do I even have to get to 180Hz, would 250Hz be enough?
I don't still know what to do with the microphone. The cheaper model needs a separate preamplifier and I just got rid off UB802 when I bought a new soundcard which has phantom power supply.
I could send my ECM8000 to them to calibrate, but the cost is 32euros and I guess the shipping would cost quite a lot (back and forth). And the ECM40 is 113euros plus shipping
In my HP, in the download folder, there is an excel file that does the calculations for gating time, minimum frequency, etc.
1000/gated ms= minimum useful frequency. So if you have 5 gated ms, you get 1000/5=200 Hz, that is the measured response is valid from 200 Hz.
To get 180 Hz you need around 5.3 ms of gated window, which means a 1.35 m of free walls areas, with the mic at 1 m from the baffle.
Since you have the M-audio FW410, why not using its pre-mic with the cheaper mic model?
claudio said:
Hi Claudio,
Could you explain what is the purpose of the baffle?
I'd think it will create a pressure zone, which is usually used to eliminate comb filter effect, which in any case would be more pronounced on higher frequencies as a result of phase anomalies due to the floor reflections.
Besides, the baffle will create a LF boost in microphone sensitivity and can be quite unpredictable.
Also, I'd like to point out the fact that it is unclear whether HF ECM8000 response is corrected for free field or diffuse field measurements.
As such, the readings would be different for broadband measurements, as well as there would be obvious differences between near and far field measurements above 5Khz.
Hi Marik,
the baffle holds the driver, separates the front emission from the back one someway, approaches the infinite baffle and follow the IEC standards. To compare different drivers response, all should be measured using the same enviroment, that is at least the same baffle, the IEC baffle.
the baffle holds the driver, separates the front emission from the back one someway, approaches the infinite baffle and follow the IEC standards. To compare different drivers response, all should be measured using the same enviroment, that is at least the same baffle, the IEC baffle.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.