Build your own 2x12" TH (The Kraken 212 TH)

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#202
tb46 said:
Hi barco,
At the very low end, below 20Hz it looks like your system may have a low cut filter. Do you have any way of testing for this?
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Maybe, I do have a oscilloscope lying around. I guess I could measure output on my amp on one channel and the output from the laptop on the other channel and see if I can see and reduction in low frequencies. It is a NAD216 (well, actually a NAD319) amplifier.

Also, I dont know how good the measure equipment is on low frequencies. I borrowed it (a ECM 8000 mic and a m-audio mobilepro audiocard). I am using the calibration file for the mic, but still dont know how accurate that is on low frequencies.
Lots of unknowns 🙂

/Anders
 
#204
A bit of red wine, a 12" subwoofer, a bowl of peanut"fingers", a man with a mission and a 140kg 11 piece pussel. Perfect ending of the friday evening (wife and daughter fell asleep together, perfect 🙂 ).

The start of horn nr 2 build 🙂

bygge2_1.jpg
 
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#207
Hi weltersys,

That slope below ~18Hz looks like about 44dB/octave to me, that's why I asked if there may be another filter involved.
Anyway, I like what barco was able to get out ouf the minidsp in Post #199.

Regards,
 
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#208
tb46 said:
Hi weltersys,

That slope below ~18Hz looks like about 44dB/octave to me, that's why I asked if there may be another filter involved.
Anyway, I like what barco was able to get out ouf the minidsp in Post #199.

Regards,
Click to expand...
The response appears to be dropping from -36 to -60(24 dB) in just over 2/3 of an octave (10-17 Hz).

The measurement mic response (or room) could account for several dB loss down that low, my RTA-420 mic has about that much less LF response compared to my B&K 4004.

At any rate, the response is easily equalized, though if the mic is actually reading less LF response than it should (as I suspect) equalizing flat to 20 actually is a slight LF boost.

Nothing wrong with a little "loudness contour" to make up for the ear's lower sensitivity to VLF at low SPL 😉.

Art
 
#209
barco said:
Also, I dont know how good the measure equipment is on low frequencies
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Hi Barco,

Your NAD amp is about -3dB between 3Hz and 8Hz. The Behringer mics have a radical drop after their -3dB point. The -3dB can vary from 18Hz in the best case and 40Hz in the worst case, depending on the production model. At 10Hz they can vary between -6dB in the best case and -14dB in the worst case (a few measured even worse). I don't know about the missmatch in impedance because there is too much variation between the mics. Most M-Audio mic inputs should be flat till about 10Hz.
 
#213
Hi Oliver,

Measurements come from well known German company, so measuring with this mic without knowing its error rate could be qualified that way.

There are a few Dutch DIY sites that provide useful info to build your own with a Sennheiser KE4-211-2i-1 capsule (89 Euro). The Behringer housing could be usefull for that 🙂
 
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#216
Hi Barco,

The link in my earlier post is quiet simple to build and costs about 110 Euro in parts. This Sennheiser capsule is also used in more serious measuring mics. Sennheiser does deliver a measuring chart that is pretty accurate.

The Monacor ECM-40 is a budget measuring mic (70 Euro) that seems to have better production lines and a better capsule compared to the Behringer. But its a fact that budget mics have their limits below 40Hz (for budget SPL meters its the same).


Monacor_ECM-40_80Responses.jpg
 
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