For T/S parameters I always measure free-air, including Vas. I use the added mass method for Vas, with small weights taped to the dustcap with blue painter's tape.
For the FR/HD tests, I use a small test box atop a small table in order to "isolate" from surfaces as much as possible. Nothing special.
For the FR/HD tests, I use a small test box atop a small table in order to "isolate" from surfaces as much as possible. Nothing special.
Results from my measurements for the Beyma 10G40 and Beyma 10MC700Nd.
Conditions identical as before to keep the measurements as meaningful as possible. Same electronics. Same 0.5 ft³ box stuffed with ½lbs of polyfill. Different room because I moved houses, that's about the only difference.
Beyma 10G40 Frequency response. 2.83V/1meter.
Beyma 10G40 Harmonic Distortion.
I think on this test one of the screws was loose and there was a good size airleak getting past the gasket, hence why the distortion below 100Hz looks really high. It is of no consequence since I wouldn't be using it below 100Hz anyways.
Beyma 10MC700Nd Frequency Response
So, it turns out, that ALL of these harmonic distortion tests are a little "off". Turns out, SPL levels should be kept under 120dB for distortion sweeps, but with the mic so close to the speaker it ended up reading approximately 125 dB for the tests. Didn't see that part in the OmniMic Help file, oops, lol. But, I don't feel that it detracts from the validity of the results because they were all done identically. In reality, all of these speakers would have lower harmonic distortion levels that what these graphs would represent. I played around with the microphone distances while testing the 10MC700Nd, and sure enough percentage levels were definitely lower. One day I might re-do all of these with more attention to this part, but none the less the relative levels allow meaningful comparisons, even if the absolute numbers might not be 100% accurate.
Here is a summary of all midbasses tested:
Obviously, there's many ways to dissect the data. The last chart just uses a made-up formula to compare the values, where the rest are more direct value-derived.
Conditions identical as before to keep the measurements as meaningful as possible. Same electronics. Same 0.5 ft³ box stuffed with ½lbs of polyfill. Different room because I moved houses, that's about the only difference.
Beyma 10G40 Frequency response. 2.83V/1meter.
Beyma 10G40 Harmonic Distortion.
I think on this test one of the screws was loose and there was a good size airleak getting past the gasket, hence why the distortion below 100Hz looks really high. It is of no consequence since I wouldn't be using it below 100Hz anyways.
Beyma 10MC700Nd Frequency Response
So, it turns out, that ALL of these harmonic distortion tests are a little "off". Turns out, SPL levels should be kept under 120dB for distortion sweeps, but with the mic so close to the speaker it ended up reading approximately 125 dB for the tests. Didn't see that part in the OmniMic Help file, oops, lol. But, I don't feel that it detracts from the validity of the results because they were all done identically. In reality, all of these speakers would have lower harmonic distortion levels that what these graphs would represent. I played around with the microphone distances while testing the 10MC700Nd, and sure enough percentage levels were definitely lower. One day I might re-do all of these with more attention to this part, but none the less the relative levels allow meaningful comparisons, even if the absolute numbers might not be 100% accurate.
Here is a summary of all midbasses tested:
Obviously, there's many ways to dissect the data. The last chart just uses a made-up formula to compare the values, where the rest are more direct value-derived.
Yes, at some point I've listened to all of them; but I will not be including subjective analysis here.
They are all excellent drivers. Once you factor in the standard deviation of the drivers' frequency response, it may or may not make a difference because "lumpy" drivers will need more equalization to tame them, thus necessitating more xover components if going passive. That's why I made the last chart that takes THD, THD standard deviation, and FR std deviation to make a sort of ranking for them. Those composite in the last chart numbers don't mean much, but it serves as a way of looking at the drivers in terms of which one I ranked "better" then the others when looking at all those factors.
The sub-100Hz THD before these two Beyma speakers may be disregarded because there were lots of screw holes since not all of these had the exact same bolt hole pattern, so there were likely air leaks contaminating the sub-100Hz sound signals. When I tested the Beyma's I added foam gasket, but even then it was not exactly optimum. I did not make an effort to rectify that aspect because I will not need them to perform much below 100Hz.
After I tested the 10G40, I knew those Spanish bastards are really on to something over there. As I mentioned in that post, "all conditions identical, except for the room because I changed houses".
After I tested the 10G40, I knew those Spanish bastards are really on to something over there. As I mentioned in that post, "all conditions identical, except for the room because I changed houses".
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Yeah 10mc700 distortion looks superior and 10g40 not far behind. I was wondering how much difference there is by ear between all the drivers, do you have a clear winner for your self or multiple (don't have to reveal which)? Offaxis frequency responses would be cool, but thats more work and might be too much to wish for 
thanks for these already!
thanks for these already!Hi OscarS
That is indeed a lot of work that you did for this comparison.
In order to check for consistency I would at least re-measure one of the drivers that you tested before because your measuring-environment/setup seems to have changed in the meantime (if I got this right).
Regards
Charles
That is indeed a lot of work that you did for this comparison.
In order to check for consistency I would at least re-measure one of the drivers that you tested before because your measuring-environment/setup seems to have changed in the meantime (if I got this right).
Regards
Charles
Yeah 10mc700 distortion looks superior and 10g40 not far behind. I was wondering how much difference there is by ear between all the drivers, do you have a clear winner for your self or multiple (don't have to reveal which)? Offaxis frequency responses would be cool, but thats more work and might be too much to wish for
What's crazy is that the actual distortion levels are lower in reality, since I accidentally went over the recommended SPL level for those tests. The 10MC700Nd average is likely 10% lower in actuality, as will all the other ones be.
Good to see my results do correlate with top-notch products out there! I've read their available white-papers and they do some pretty good R&D in that Spanish factory!. Although I do wonder why they chosen to not implement certain other technologies like silicone-sandwiched spiders or damping compounds within the valley of the surrounds; which is rather surprising given how well they perform!
Yeah 10mc700 distortion looks superior and 10g40 not far behind. I was wondering how much difference there is by ear between all the drivers, do you have a clear winner for your self or multiple (don't have to reveal which)? Offaxis frequency responses would be cool, but thats more work and might be too much to wish for
As of right now, I am leaning towards the Beyma's. The 10G40 has a smooth response that would need very little xover components, which is very attractive, but the 10MC700Nd is just so clean at what I would already call ear-splitting levels for it's frequency range. But the 10PLB76 is very attractive for the price it can be had! Choices!
Good to see my results do correlate with top-notch products out there! I've read their available white-papers and they do some pretty good R&D in that Spanish factory!. Although I do wonder why they chosen to not implement certain other technologies like silicone-sandwiched spiders or damping compounds within the valley of the surrounds; which is rather surprising given how well they perform!
As of right now, I am leaning towards the Beyma's. The 10G40 has a smooth response that would need very little xover components, which is very attractive, but the 10MC700Nd is just so clean at what I would already call ear-splitting levels for it's frequency range. But the 10PLB76 is very attractive for the price it can be had! Choices!Yeah 10mc700 distortion looks superior and 10g40 not far behind. I was wondering how much difference there is by ear between all the drivers, do you have a clear winner for your self or multiple (don't have to reveal which)? Offaxis frequency responses would be cool, but thats more work and might be too much to wish for
Late edit: Big thanks to Jay @ Loudspeakers Plus for hooking it up with many of these drivers! Fast email communication, best prices, quick delivery (it isn't 2-day Amazon Prime, but it still ships quick, LOL), and of course full warranty as he is an authorized dealer for pretty much all pro audio brands.
The reason they say to keep the level that low for THD tests is to avoid introducing the mic distortions into the data set. The THD values for all drivers other than the recent Beyma are a compound of the driver and mic distortions, so can’t really be trusted. Even though conditions were the same, the SPL at each frequency was not, so the distortion from the mic will vary at all frequencies across all drivers. If you can retest, that would be great!
Some years ago Lynn Olson and Dick Olsher made a BIG deal of the 12 inch Alnico Tone Tubby--implying it's a combination of Alnico Magnet and hemp cone reach a level of performance on par with the very best midbass drivers. However, the 12 TT needs appreciable correction via passive eq. I'd imagine the 10 is perhaps better/smoother but with 2db or so less efficiency. The pros (JBL, 18SOUND, et al) KNOW about engineering magnetic circuit improvements equal to or better than Alnico, so what do THEY also think of hemp cone material and it's a reduced resonant breakup modes? Why aren't they using it also, since it's clearly in the public domain? Beyma does "seem" to be one major pro manufacturer that is into minimal cone breakup--it's Beyma who's published FR curves on a number of its major drivers seem distinctly smoother than the competitions. The 12GA50 (a full range using ferrite but corrected via a copper shorting cap that's smoother and more extended than the TT12), 12G40, 10G40, 10MI100 and others perhaps. The latter Beyma's DON'T use copper shorting though.
As posted Tone Tubby Alnico 12
Driver Properties
Name: TT Alnico 10
Type: Standard one-way driver
Fs = 107.32 Hz
Fsa = 52.36 Hz
BWs = 12.72 Hz
Vas = 24.5 Liters
Cms = 1.28E-04 m/N
Mmd = 16.8 g
MMr = 5.4 g
BL = 6.78 Tesla/m
Efficiency 94.64 dB lw/lm
Qms = 11.13
Qes = 1.58
Qts = 1.39
Re = 6.5 Ohms
Zmaxs = 130.2 Ohms
2.83-V SPL = 94.64 dB
1-W SPL = 95.1 dB
Kr = 0.000
Xr = 0.000
Ki = 0.000
Xi = 0.000
As posted Tone Tubby Alnico 12
Driver Properties
Name: TT Alnico 10
Type: Standard one-way driver
Fs = 107.32 Hz
Fsa = 52.36 Hz
BWs = 12.72 Hz
Vas = 24.5 Liters
Cms = 1.28E-04 m/N
Mmd = 16.8 g
MMr = 5.4 g
BL = 6.78 Tesla/m
Efficiency 94.64 dB lw/lm
Qms = 11.13
Qes = 1.58
Qts = 1.39
Re = 6.5 Ohms
Zmaxs = 130.2 Ohms
2.83-V SPL = 94.64 dB
1-W SPL = 95.1 dB
Kr = 0.000
Xr = 0.000
Ki = 0.000
Xi = 0.000
Also some more damping material would be good to add because the distortion from the back wave that is reflecting back from the box and through the cone is not drivers fault.
And if the time is limited, it would be good just at least to test the tree best drivers to find the winner.