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Old 8th August 2011, 03:02 AM   #501
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Default Weird DACS-ADC calibration result..

Awesome program! I hope this program can dial my 4-way system in the Ridgeline!

I am using a Hp notebook sound card.. I went to calibrate using the DACS-ADC routine and noticed that my frequency response goes out to only ~7khz. This will not do!

Do I have a sound card limitation? How can I verify?

I am using default settings except for selecting the sound card and lowered the signal -6db to eliminate clipping.

Thanks for your help!
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Old 8th August 2011, 04:59 AM   #502
Pano is offline Pano  United States
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Yeah, that's a really bad loop. And it's inverted. (Easy to fix).
No way should it look that bad. Did you use 48Khz as the sample freq? Are all effects turned off in Windows? Is it a line input, or mic?
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Old 8th August 2011, 05:39 AM   #503
NEO Dan is offline NEO Dan  United States
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Quote:
Originally Posted by wintermute View Post
Hi Dan, see the screenshots below for the settings that I've been using to successfully export holm impulse measurements for use in speaker-workshop.
Thanks for the help Tony
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Old 9th August 2011, 03:30 AM   #504
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Quote:
Originally Posted by Pano View Post
Yeah, that's a really bad loop. And it's inverted. (Easy to fix).
No way should it look that bad. Did you use 48Khz as the sample freq? Are all effects turned off in Windows? Is it a line input, or mic?
Thanks for the fast response.. I used 44 KHz, so based on the nyquist I should have recorded more bandwidth. I used a looped line input.

I decided to try my desktop and the sound card must be a lot better since I got a frequency response out to ~20KHz with +/- 6 db. thx.
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Old 9th August 2011, 03:45 AM   #505
adason is offline adason  United States
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I had similar problem once with toshiba laptop, there was somewhere in the software a function "voice only" or something similar
I had to disable that function every time I used that laptop
search the settings....

(I no longer have that laptop, so I can not verify what was it)
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Old 10th August 2011, 01:10 AM   #506
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thank you.
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Old 10th August 2011, 02:43 AM   #507
Pano is offline Pano  United States
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Agree with the above. Dig thru all the Windoze sound settings looking for "features". It may take some digging. You'll know when you've found it because the response will be (nearly) flat. Good luck!
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Old 10th August 2011, 03:52 AM   #508
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Quote:
Originally Posted by Pano View Post
Agree with the above. Dig thru all the Windoze sound settings looking for "features". It may take some digging. You'll know when you've found it because the response will be (nearly) flat. Good luck!
Got it! Turning "voice recording" filter off , solved this issue. thx.
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Old 20th August 2011, 05:24 AM   #509
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Default Update driver rollover issue

Now I have taken few steps more and took measurements on another PC with another soundcard and microphone. However graph looks similar to one posted earlier. Here I am thinking; surely my simple low pass crossover must be working fine. Question is what is it that I am looking at.

Well, I am getting lost in this driver roll-off issue. In a 2 way crossover setup the low pass driver should roll-off at predetermined frequency. Since I am only testing 1st order low pass roll-off only one coil is involved. Simple.

Someone mentioned change in impedance, here I did use 1.0 mH coil that relates to 15 ohm rather than woofer impedance of 8. Pretty much same graph resulted.



Driver tested: Silver Flute W14RC25-08 ohm 5-1/2" Wool Cone: Madisound Speaker Store


Drawing test coil.jpg

holm 50 100 mh.jpg
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Old 21st August 2011, 07:28 PM   #510
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Unhappy Auto detect impulse time window gives funny data

Greetings,

I'm taking my first measurements with HOLM impulse. I've not been able to find any manual or user guide, so I don't know what I'm doing. First, please note the lengths I went to to keep the speaker and microphone far from any reflective surface, seen in the 1st photo. The mic is 1 meter from speaker and over 3 meters off the ground. When I use the auto detect impulse time window feature, I get the responses seen in the second picture. This is the woofer only with no X-over components. The 3 measurements shown are two port lengths, and one with the port sealed. I'm skeptical about the 50cm to 120cm distances. Is this the distance of the nearest reflective surface? Of course, I do not believe the frequency response data. The third picture is with the gating set manually. I just moved the lines around until I got a FR plot that looked like what I expected.

So . . .

Might HOLM be detecting the reflections from my balcony and railings? Can Holm's sensitivity to such reflections be decreased? Can they be compensated for? I don't think I can get my speaker further from reflective surfaces. Is the recording messed up from distant lawnmowers and birds? Am I right to use manual gating in this case?

Any advice from more experienced users would be greatly appreciated.

Also: Yes, I calibrated my sound card, and uploaded my microphone calibration file.
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File Type: jpg 2011-08-21_HOLM_auto gating 2.JPG (252.3 KB, 270 views)
File Type: jpg 2011-08-21_HOLM_25Hz gating.JPG (273.4 KB, 257 views)
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