Virtual machines can be easier now than they used to be. Especially interesting if you use multiple monitors and/or multiple desktop switching.
Do you have music coming from your re vamped speakers?
Alternatively are you in the chirps, white and pink noise measurement phase?
Just being nosey. 🙂
Alternatively are you in the chirps, white and pink noise measurement phase?
Just being nosey. 🙂
I have the old drivers removed - not as easy as it sounds. I have measured the out-of-cabinet impedance of both tweeters and both woofers. The matches are quite good. I have measured the in-cabinet impedance of the woofer. Next are SPL's of woofers and then tweeters. I had a minor setback with some mounting screws and had to purchase others. The new ones arrive this week. As a consequence, my woofer is leaking a bit around its flange, so I figured my numbers would be poor. I have one other problem, that's going to be tough: the thickness (Z-axis) of the woofer flange is great enough that the rubber around the driver bumps into the cloth covering. I have to have a fix for that. My I'll post some results as I have them.
Thank you for the update, its good to hear you are making progress.
Can you use some shims to move the cover out by a few millimetres, or are they glued to a mounting baffle?
Good luck with finding a workable solution.
Can you use some shims to move the cover out by a few millimetres, or are they glued to a mounting baffle?
Good luck with finding a workable solution.
I'll consider the shims. I have some felt of 3-4mm thickness I use for chair legs. I could place these on the surrounding felt to raise the cloth cover. Another method would be to use a router and rabbet bit to set the flange down a few millimeters. I don't have a router or the bit, so I'm investigating that approach. X figure Xmax is 5mm and the rubber will move perhaps half that, so about 3mm would be about right.
I suffered a bit of a setback. I had purchased an iAudioInterface2 for this task. I had hoped it would allow me to do measurements I need to do. Today I boxed it up for return. The system was to run on my ipad (with a bluetooth keyboard) and was to provide signal generation, software, and an interface with an included calibrated mic using a balanced interface. I was never able to get signal generation to work well enough - the volume was too low even with fairly efficient drivers, so a measurement with a decent signal to noise ratio was not possible. I then tried my own amplifier and sent iAudioInterface2 software's signals to it, but that was a can of worms. My amplifier puts a delay into the signal, and I could find no way to align time domain information. I tried using the iAudioInterface2 with my Mac. It would identify it but would not allow input from or output to the device. Lastly, the iAudioInterface2 had intermittent connections to both power and the controlling computer (mac or ipad). Trying to deal with all of these problems while trying to figure out Vituixcad2 and REW made it impossible for me to trust any measurement. Today I gave up.
I won't be doing anything until I find test gear I can trust.
I'm trying to follow this: https://kimmosaunisto.net/Software/VituixCAD/VituixCAD_Measurement_REW.pdf
But it starts with gear completely different than my own - iAudioInterface2 and AudioTools. I'm on a Mac running Parallels. Under Parallels is Vituixcad. REW is running directly under MacOS.
I have to say that I don't trust REW and Vituixcad2 either. The problem with a thousand capabilities is that a user does not know what is going on behind his back. For a particular test, which of the thousand settings matter, which don't, when is information shared from one software interface to another, and what precisely is being shared? Of the many user interfaces, what order does one procede through them?
I also need to be able to phase-align my drivers. I could not get past the multitude of problems in my test gear to address this.
I could really use a tutorial of getting a standard SPL measurement of my drivers and feeding it back into Vituixcad2 for simulation - I think already I have good impedance measures. When taking SPL measurements my thinking was 1W @ 1meter directly in front of the driver, but that didn't work at all. Okay impedance changes with frequency, so this idea wasn't good. But what is the standard way to take that measure, and what, if any weighting (flat, a, c, etc) is to be used? I need Vituixcad2 software reading SPL graphs of my woofer and tweeter, that improve the the correctness of simulation. I think mine are making it worse. After that, I'll need SPL's at angles. The joys of being a beginner.
I would love to hear the minimum set of test gear I should have that is absolutely trustworthy.
I won't be doing anything until I find test gear I can trust.
I'm trying to follow this: https://kimmosaunisto.net/Software/VituixCAD/VituixCAD_Measurement_REW.pdf
But it starts with gear completely different than my own - iAudioInterface2 and AudioTools. I'm on a Mac running Parallels. Under Parallels is Vituixcad. REW is running directly under MacOS.
I have to say that I don't trust REW and Vituixcad2 either. The problem with a thousand capabilities is that a user does not know what is going on behind his back. For a particular test, which of the thousand settings matter, which don't, when is information shared from one software interface to another, and what precisely is being shared? Of the many user interfaces, what order does one procede through them?
I also need to be able to phase-align my drivers. I could not get past the multitude of problems in my test gear to address this.
I could really use a tutorial of getting a standard SPL measurement of my drivers and feeding it back into Vituixcad2 for simulation - I think already I have good impedance measures. When taking SPL measurements my thinking was 1W @ 1meter directly in front of the driver, but that didn't work at all. Okay impedance changes with frequency, so this idea wasn't good. But what is the standard way to take that measure, and what, if any weighting (flat, a, c, etc) is to be used? I need Vituixcad2 software reading SPL graphs of my woofer and tweeter, that improve the the correctness of simulation. I think mine are making it worse. After that, I'll need SPL's at angles. The joys of being a beginner.
I would love to hear the minimum set of test gear I should have that is absolutely trustworthy.
The impedance and frequency response data are exported from REW as text files. You can open them up and view them if you want before importing them into VituixCAD.
The standard is to set the output voltage of the amplifier to 2.83V, which is 1W for an 8ohm load and 2W for a 4ohm load. The drivers' impedances do change with frequency, that is the nature of the beast. The important factor is that your amplfier is able to maintain the same voltage across the frequency sweep, which any decent amplifier will do. The current will vary at different frequencies due to the changing impedance, but that does not matter with regard to the frequency response measurements. In that regard, the commonly used parameter 1W/1m really only is accurate for a purely resistive load, and just an estimation when it comes to real world speakers.
The standard way to take the measurements is to measure on axis (0 degrees), and at varying degrees off axis horizontally. At a minimum I recommend measuring at least at 0, 15, 30, 45 and 60 degrees. But, the more measurements the better VituixCAD will be at predicting off axis performance and directivity indexes. Measuring from 0 - 90 degrees at 10 degree increments would be great if you don't mind spending the time to do so.
Since you are not using an anechoic chamber for your measurements, you should measure at 1m and use IR Windows in REW to filter out sound reflections off of the floor, walls, etc., which distort your data. In anechoic chambers they typically measure at 2m, but at that distance reflections off of the floor, walls, etc. become problematic if you are not in an anechoic chamber.
When I took my frequency response measurements I placed the speaker on an 8 ft. ladder in my backyard, well away from the house. I set the IR window to close before the first floor reflection was received. (Do it on a calm day - I had problem with noise from the wind). The IR window will limit the low frequency of your measurement. With an 8ft. latter it probably will give you data down to about 400Hz or so. That should be fine. If you want to get a frequency response measurement below that frequency, you probably will need to do a ground plane measurement for the lower frequencies. I didn't bother with that for my project.
You can look into ARTA and use that instead of REW. It is inexpensive, but not free. Also, it is more complicated to use that REW, and for highest accuracy you need a 2-channel audio interface (I use a Steinberg UR22 mkII) and an ARTA Box (which you build yourself). If you are curious, you can look into it. Given how much you already are having to learn, though, I would keep it simple for now and just use REW. When I took my outdoor measurements I used both REW and ARTA and modelled both sets of data in VituixCAD. If I remember correctly they were pretty close.
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Or a near-field measurement, applying baffle correction as provided by Vituixcad.
You don't need to do that as the different time of flying from mic to the driver is already included in the measurement: just carry out a dual channel measurement with mic on axis for every driver. Set then the x,y,z coordinates in the crossover tab (z=0, unless you have a stepped baffle).
If do not like REW, Arta is now free, but I don't know if will run on mac.
I finally have my test gear working. With the delay, I hope I haven't lost the interest of all who have helped.
I thought I might invite comments upon the measurements I've taken. Below is the Vituixcad2 graph of how the woofer and tweeter were expected to perform without a crossover. After that are two graphs follow from REW, one without smoothing and one with it, representing SPL sweeps taken indoors. There are, of course, room modes affecting the graphs, so I gated the empirical data. This helped somewhat, however, there is a pronounced dip at 100Hz which I hope is a room anomaly. With my little experience, I'm not sure if I should be happy with the measurements or not. I'm trying to figure out how to modify the crossover given actual SPLs.
I am doing additional measures of +/-15, 30, and 45 degrees. I'm not yet sure how to use that data to get a directivity graph (baby steps).
I thought I might invite comments upon the measurements I've taken. Below is the Vituixcad2 graph of how the woofer and tweeter were expected to perform without a crossover. After that are two graphs follow from REW, one without smoothing and one with it, representing SPL sweeps taken indoors. There are, of course, room modes affecting the graphs, so I gated the empirical data. This helped somewhat, however, there is a pronounced dip at 100Hz which I hope is a room anomaly. With my little experience, I'm not sure if I should be happy with the measurements or not. I'm trying to figure out how to modify the crossover given actual SPLs.
I am doing additional measures of +/-15, 30, and 45 degrees. I'm not yet sure how to use that data to get a directivity graph (baby steps).
Attachments
that's very probably the case.
What gating times did you use?
Getting response down to 100 Hz is usually not possible when excluding reflections.
Usual gating times for anechoic results will be around 5 ms.
Did you use the impulse response graph to set your gating?
@stv I used the IR graph to set a gate time of 23.2msec past the peak. When I used a point closer to the peak I began losing the lower frequencies output in the SPL graph. I haven't thought that through, so I don't know why these frequencies disappear when the gate time is closer to the peak. I didn't change the left parameter, only the right.
Its good that you are back on the measurement path.
Loosing low frequency data information does seem a bit strange, Maybe the gate moves as you adjust one parameter? I wonder can the gate can be locked somewhere just in front of the impulse at approx 300mS for a microphone positioned at 1metre.
I often use a overall viewing window of 10mS for indoor type work. I have a small room, and the reflections come back within that viewing window setting.
Moving the right hand window cursor closer to the first cursor at 3mS I loose low frequency data which is to be expected. Typically crossing to a tweeter at 2KHz and above its not an issue as you are using the hi resolution data from the 1-4kHz and higher, with its associated minimum phase data to show you how the drivers and crossovers interact.
Good luck with the next stage of measurements.
Loosing low frequency data information does seem a bit strange, Maybe the gate moves as you adjust one parameter? I wonder can the gate can be locked somewhere just in front of the impulse at approx 300mS for a microphone positioned at 1metre.
I often use a overall viewing window of 10mS for indoor type work. I have a small room, and the reflections come back within that viewing window setting.
Moving the right hand window cursor closer to the first cursor at 3mS I loose low frequency data which is to be expected. Typically crossing to a tweeter at 2KHz and above its not an issue as you are using the hi resolution data from the 1-4kHz and higher, with its associated minimum phase data to show you how the drivers and crossovers interact.
Good luck with the next stage of measurements.
That's why you either just disregard the low frequencies with your measurements and rely on simulation of your woofer enclosure or you do a nearfield measurement of driver and eventual port, merge those using the correct ratio, apply baffle step simulation and splice the measurement.
See vituixcad manual for details!
@raymondj, @stv, @TerryForsythe, @shadowplay62
I'm having a problem with my woofer. I believe it's caused by interactions with the box dimensions. There is a dip at about 100Hz that seems to causes additional dips and rises with its harmonics. Given its low frequency, I'm not sure how to best dampen it within the box? Can anyone suggest the best way to approach this? The box internal dimensions are: 8"x10"x16" or 203mm x 254mm x 406mm. The baffle is the 8"x16" surface. The Dayton SIG180-4 woofer I'm using is vented on its backside and perhaps this contributes to the problem, however, opposite its vent is two inches of fiberglass insulation. The box is ported with a vent sized: 2"ID x 3.3" length or 51mm x 84mm. I believe that it's tuned for about 57Hz and wonder if it might be a little longer? Remember, I'm stuck with this box size. I have fiberglass and sheets of aluminum/bitumen 3mm thick dampening materials. I could purchase other materials but I'm not sure what to do.
I have attached empirically measured SPL curves as they appear in REW and Vituixcad2. Measurements were take outdoors with a calibrated mic from 1M at 2Vrms with the speaker elevated such that the woofer was about 1.2 meters about the lawn. The Vituixcad2 image is without a crossover. I'm not sure why it does not better match the REW image since it is using that as input. Comments on how to address the issue would be very much appreciated. Thank you.
I'm having a problem with my woofer. I believe it's caused by interactions with the box dimensions. There is a dip at about 100Hz that seems to causes additional dips and rises with its harmonics. Given its low frequency, I'm not sure how to best dampen it within the box? Can anyone suggest the best way to approach this? The box internal dimensions are: 8"x10"x16" or 203mm x 254mm x 406mm. The baffle is the 8"x16" surface. The Dayton SIG180-4 woofer I'm using is vented on its backside and perhaps this contributes to the problem, however, opposite its vent is two inches of fiberglass insulation. The box is ported with a vent sized: 2"ID x 3.3" length or 51mm x 84mm. I believe that it's tuned for about 57Hz and wonder if it might be a little longer? Remember, I'm stuck with this box size. I have fiberglass and sheets of aluminum/bitumen 3mm thick dampening materials. I could purchase other materials but I'm not sure what to do.
I have attached empirically measured SPL curves as they appear in REW and Vituixcad2. Measurements were take outdoors with a calibrated mic from 1M at 2Vrms with the speaker elevated such that the woofer was about 1.2 meters about the lawn. The Vituixcad2 image is without a crossover. I'm not sure why it does not better match the REW image since it is using that as input. Comments on how to address the issue would be very much appreciated. Thank you.
Attachments
Probably a ground reflection. Move the woofer to 2m height and see if the frequency of the dip changes. If so, that confirms it. In REW you can narrow the impulse response window to filter out reflections.
@TerryForsythe, @stv, @phreepie
You are correct. I did the measurements at 2M and the 100Hz dip went away.
It's very unnerving seeing a speaker precariously perched so high. My neighbors don't really know what I'm doing - I think I'll put on an aluminum foil hat for their benefit.
After tuning the port to 41Hz, and getting new impedance values, I took the new SPL measurements elevated to 2M, on-axis, +/-15 degrees, and +/-30 degrees. I had a technical difficulty doing +/-45 degrees, the speaker sitting on a small perch, when turned to 45 degrees, could fall. I loaded these measures from REW to Vituixcad2 and came up with the attached results. What do you think?
You are correct. I did the measurements at 2M and the 100Hz dip went away.
It's very unnerving seeing a speaker precariously perched so high. My neighbors don't really know what I'm doing - I think I'll put on an aluminum foil hat for their benefit.
After tuning the port to 41Hz, and getting new impedance values, I took the new SPL measurements elevated to 2M, on-axis, +/-15 degrees, and +/-30 degrees. I had a technical difficulty doing +/-45 degrees, the speaker sitting on a small perch, when turned to 45 degrees, could fall. I loaded these measures from REW to Vituixcad2 and came up with the attached results. What do you think?
