proid
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Post by proid on Nov 22, 2013 16:19:19 GMT
Hi, Frans, i have just built the filter correction for my t50rp in perfboard, but seem like it just pass the signal and nothing is corrected, the graph i measure after using the filter correction and before is about the same. Components i used:
-C101,C101 2.2uf
-C102,C202 1uf
-C104,C204 0.001uf
-C105,C205 470pF
-C106,C206 0.01uf
-C107,C207 2200pf
All the capacitor are film type except C105,C205 is silver mica. P101,P102,P201,P202 is bourns 3296 type which is multi turn so at first, i turned P101, 201 CW until i heard "tick" but after that, i measure pin 1 and 3 of all these 4 and get about 5k ohm.
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solderdude
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Post by solderdude on Nov 22, 2013 21:32:27 GMT
If these pots are 10k you will get 5k as they are in parallel.
Have you tried turning the pots all the way in the other direction (fully CCW) ?
The wiper (middle leg of the pot) to which pin of IC ICx01 does it have close to 0 Ohm ?
Even when the 2 bandfilters do not work you should at least get more sub lows and a bit less mid-bass, it should not do nothing.
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proid
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Post by proid on Nov 23, 2013 9:11:57 GMT
Here is the graph before and after:   It seem to lift the sub bass a bit and the high significantly. I tried to turn the pot another way but nothing happend with the dip from 2-5Khz, only the high frequency is different. I got near 0R between pin 3 and 2. |
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solderdude
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Post by solderdude on Nov 23, 2013 9:24:29 GMT
It seems your 3.5kHz section is not working.
Maybe an error in chosen values or wiring error.
As you can see the lows section is working as well (that is very subtle) and you should be having more 'air' and better cymbals already.
The 20kHz section seems to work and you need to use some felt in front of the driver to lower the highs or build the filter with only one notch section.
This last filter is better suited for T50's without felt in front of the driver. (the version micmacmo is using)
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proid
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Post by proid on Nov 23, 2013 10:56:03 GMT
It seems your 3.5kHz section is not working. Maybe an error in chosen values or wiring error. As you can see the lows section is working as well (that is very subtle) and you should be having more 'air' and better cymbals already. The 20kHz section seems to work and you need to use some felt in front of the driver to lower the highs or build the filter with only one notch section. This last filter is better suited for T50's without felt in front of the driver. (the version micmacmo is using) I double check but everything seem to be correct, is the 3.5khz section IC102A or IC102B? |
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solderdude
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Post by solderdude on Nov 23, 2013 11:32:25 GMT
the one with Cx06, Cx07
double check the used values
Perhaps the filter circuit on page 37 of the latest manual (was page 35 on the previous manual I believe) is more suited for your T50 as it doesn't seem to have felt in front of the driver.
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Post by micmacmo on Dec 2, 2013 1:19:52 GMT
I setup my REW measurement kit again this weekend. For the sake of completeness, here's the outcome of my K701 active filter. I used an O2/ODAC combination. The REW setup involved the standard Panasonic mics. The filter was built exactly as per the guide.  |
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Post by micmacmo on Dec 2, 2013 1:33:08 GMT
And here's the FR curves for the Page-35 T50RP active filter. The mods are pretty close to BMF's rock wool (not cotton) DBV#3 mods that he posted to head-fi. Again, measured using O2/ODAC combo. The active filter varied from the Page 35 version: Rx03=8.2 kOhms and Rx06 330 ohms. Frans, I'd like to achieve two things. First, I think the peak I need squash is closer to 6 kHz or 7kHz. What replacement resistors should I use in the Rx11 slots? And the top-end lift is too high; what alternative resistors would you recommend in the Rx06 slots? (Frankly, I enjoy the slightly brighter presentation, but it's too hot as it is.)  |
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solderdude
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Post by solderdude on Dec 2, 2013 6:11:58 GMT
The measurements are a bit suspect above 3kHz. Both the filtered K701 nor T50RP drop-off above 6kHz. K701:   did you mount the mics in plastic tubing or under a serious angle or were they tucked in ears mounted on earplugs ? |
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Post by micmacmo on Dec 2, 2013 6:45:44 GMT
Ah. Good point. The mics were mounted into Etymotic triflange plugs from old ER6i earphones. I used silicone as the adhesive. (The plugs were inserted into my ears for the measurements…giving new meaning to the term "dummy head".) You'll note that there's a deep 8kHz chasm in the posted measurements. This is a feature of many (if not all) of my measurements. Any idea on what the problem might be?
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solderdude
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Post by solderdude on Dec 2, 2013 7:05:27 GMT
could not get any accurate readings using ear plugs and as the mics are closer to the driver (as they stick out of your ears) and under an angle the highermids /lower treble is accentuated.
For measuring headphones I found a baffle mounted mic with rubber cell foam to work best.
Also you need to compensate for baffle mounting and the peak the WM61 mics show (a few dB around 16kHz)
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proid
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Post by proid on Dec 2, 2013 17:22:58 GMT
could not get any accurate readings using ear plugs and as the mics are closer to the driver (as they stick out of your ears) and under an angle the highermids /lower treble is accentuated. For measuring headphones I found a baffle mounted mic with rubber cell foam to work best. Also you need to compensate for baffle mounting and the peak the WM61 mics show (a few dB around 16kHz) When i use the mic mount in a foam tip and plug it in my ear, i have the same drop off in hf like you then i make some thing like a dummy head, mount the mic on it and the problem is solved. |
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Post by micmacmo on Dec 9, 2013 1:06:59 GMT
...The active filter varied from the Page 35 version: Rx03=8.2 kOhms and Rx06 330 ohms. Frans, I'd like to achieve two things. First, I think the peak I need to squash is closer to 6 kHz or 7kHz. What replacement resistors should I use in the Rx11 slots? And the top-end lift is too high; what alternative resistors would you recommend in the Rx06 slots? (Frankly, I enjoy the slightly brighter presentation, but it's too hot as it is.) Frans, could you offer some advice on making the above changes? |
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solderdude
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Post by solderdude on Dec 9, 2013 6:02:51 GMT
Is that for the K701 or T50RP ?
For the T50RP I have only seen peaks between 8khz and 10kHz
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Post by micmacmo on Dec 11, 2013 2:32:05 GMT
Frans, it was with the T50RP filter using T50RP modified with rock wool. As you pointed out, my FR measurements look suspect, so I use log sweeps to find any obvious peaks. In this case, I ran increasingly narrow sweeps to pinpoint this one peak that's audible to even my tin ears. It's at roughly 6500-7000 Hz.
BTW, I think this problem is primarily associated with the rock wool mod. It's not as evident with DBV#3. However, with both mods, I find the top end is still a tad hot with the 330 ohm resistors in RX06.
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