This past weekend I did a talk on how to get good measurements when you don't have somewhere good to do it.
I designed and build a small sealed reference speaker in the UK using a B&C 12NDL88
I got some measurements outside fully calibrated in half space:
I then measured it at 8.49v to account for the 3m and 1w at 8 ohm
This got me this result:
I wish I had done more sweeps and a bit slower to get it a little smoother but I was in a bit of a rush getting prepared to come over to Berlin for the Hackathon.
I also measured a duel 12" reflex box outside in half space to compare it to.
On the following graph there is one very uncalibrated measurement of the duel 12" reflex which is the purple at the top, one measurement that is the half space measurement of the duel 12 reflex (half space so +6db) then the final lower purple measurement is the corrected measurement from above with the reference box.
As you can see from the graph above it gets you very close using the reference speaker to calibrate but the space I measured it in wasn't too bad.
When I got to berlin I borrowed a 12NDL88 and rebuilt the reference box.
In the workshop I used possibly the worst space I could find to do a measurement to see what results I could get using a 12" tapped horn:
These were the uncalibrated results:
As you can see there isn't much you could do with these measurements as the room was tiny and there was a lot of reflections.
After processing the results using my outdoor half space measurement:
As you can see the measurement has been cleaned up to the point of being extremely usable, it would be possible to EQ this flat and time align it to other speakers measured in the same place.
I think after testing this with the other measurement it is very important to get the measurement environment as similar as possible, measuring indoors without the background noise and other things changing seems to work really well.
Another factor is I found a sub to measure with a similar baffle size whereas that could add some distortion to the measurement, the duel 12 reflex was cleaned up reasonably well just off by a few DB, which I think was from me rushing and not measuring it properly. I thought I had calibrated it all but in my rush it was a good 15db too high haha.
Over the next few days I will release my outdoor measurement for this box and the dimensions of the sealed box for anyone else to build. This should allow anyone to get really good measurements without needing to find a massive space outdoors.
You can do this in your living room and get to within +-1db
Also using this subtractive method will allow you to in theory use any microphone and not calibrate anything and as long as you keep it all the same between tests it will calibrate it to my measurement
Another note is I had been messing around with REW before this and forgot to reapply my mic calibration, it doesn't adjust it too much but I will try and get a better measurement of my reference box, it won't change it too much though as it is already pretty flat.
All the presented measurements have no smoothing or windowing.
Another note would be that the 12ndl88 isn't the best for this but it was a driver that I owned and someone I knew in berlin owned so we could test this.
I was given this Idea by Kyle from Neuron AV but I couldn't find his profile on here to tag
I designed and build a small sealed reference speaker in the UK using a B&C 12NDL88
I got some measurements outside fully calibrated in half space:
I then measured it at 8.49v to account for the 3m and 1w at 8 ohm
This got me this result:
I wish I had done more sweeps and a bit slower to get it a little smoother but I was in a bit of a rush getting prepared to come over to Berlin for the Hackathon.
I also measured a duel 12" reflex box outside in half space to compare it to.
On the following graph there is one very uncalibrated measurement of the duel 12" reflex which is the purple at the top, one measurement that is the half space measurement of the duel 12 reflex (half space so +6db) then the final lower purple measurement is the corrected measurement from above with the reference box.
As you can see from the graph above it gets you very close using the reference speaker to calibrate but the space I measured it in wasn't too bad.
When I got to berlin I borrowed a 12NDL88 and rebuilt the reference box.
In the workshop I used possibly the worst space I could find to do a measurement to see what results I could get using a 12" tapped horn:
These were the uncalibrated results:
As you can see there isn't much you could do with these measurements as the room was tiny and there was a lot of reflections.
After processing the results using my outdoor half space measurement:
As you can see the measurement has been cleaned up to the point of being extremely usable, it would be possible to EQ this flat and time align it to other speakers measured in the same place.
I think after testing this with the other measurement it is very important to get the measurement environment as similar as possible, measuring indoors without the background noise and other things changing seems to work really well.
Another factor is I found a sub to measure with a similar baffle size whereas that could add some distortion to the measurement, the duel 12 reflex was cleaned up reasonably well just off by a few DB, which I think was from me rushing and not measuring it properly. I thought I had calibrated it all but in my rush it was a good 15db too high haha.
Over the next few days I will release my outdoor measurement for this box and the dimensions of the sealed box for anyone else to build. This should allow anyone to get really good measurements without needing to find a massive space outdoors.
You can do this in your living room and get to within +-1db
Also using this subtractive method will allow you to in theory use any microphone and not calibrate anything and as long as you keep it all the same between tests it will calibrate it to my measurement
Another note is I had been messing around with REW before this and forgot to reapply my mic calibration, it doesn't adjust it too much but I will try and get a better measurement of my reference box, it won't change it too much though as it is already pretty flat.
All the presented measurements have no smoothing or windowing.
Another note would be that the 12ndl88 isn't the best for this but it was a driver that I owned and someone I knew in berlin owned so we could test this.
I was given this Idea by Kyle from Neuron AV but I couldn't find his profile on here to tag
