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Old 9th February 2014, 05:45 PM   #661
Loren42 is offline Loren42  United States
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Quote:
Originally Posted by ReggieleeMorton View Post
is there a simulation program using given parameters of loudspeakers, without measuring tools or if I don't have measuring tools?
Yes, just do a search for loudspeaker box design tools. Many are free.

WinIsd is popular.

However, you really need to measure both the driver and the completed loudspeaker to get things right. Simulations only go so far.

You can do this cheaply with an electric condenser mic element and make your own mic or buy a good mic from Parts Express, etc.

You need a sound card that will accept a mic input, but many use a USB interface box that supports phantom power for the electric mic.
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Old 13th February 2014, 08:13 PM   #662
pet007 is offline pet007  Czech Republic
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Hi, please, I'd like to ask you about my measurement attempt in Holm. I'am trying to develop crossover for 2way system with Visaton WS20 and G25 FFL tweeter with Waveguide WG148. Please see the attached photo. I am not sure about the oscillations before the main peak in tweeter measurement. Woofer has nice smooth impulse. But where should be the zero time in this measurement ? Thanks a lot.

Note: (I am using ASIO USB sound card ARES SC4, 48kHz, lowcost Megaton M-1 calibrated mic + 3dB preamp and LineIN).
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Old 13th February 2014, 08:47 PM   #663
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pre-ringing indicatrs a problem with the measurement. strange tha you don't see it on the woofer measurement. I'd try again after a full system shutdown and startup.

If you are measuring on your final baffle, I would set the time zero on the tweeter measurement (make sure you tell it to do it twice, the first time it is slightly off. Then go to the second tab and lock time zero before measuring your woofer. This ensures that your phase data is correct for your crossover modelling.

Tony.
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Old 14th February 2014, 06:45 AM   #664
pet007 is offline pet007  Czech Republic
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Thank you for the reply. Anyway, if you see another attached pic (test measurement during mic calibration); here is quite strange behaviour when calibration is ON or OFF. When it's OFF, pre-ringing amplitude is much smaller then mic cal. is ON. How is it possible ?
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Old 14th February 2014, 07:52 AM   #665
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I suspect that there is some feedback happening. Check your settings to make sure that the sound card is not "monitoring" what is coming in on the line in. Some sound cards have a setting that sends the incoming line in back out the line out. This results in feedback and screwed up measurements.

Also make sure nothing is running that is changing settings on the sound card. particularly problematic are things like itunes.

My guess is that the problem was present when you tried to calibrate, and the adjustments that the calibration file is trying to do are making things worse.

What did your loopback measurement look like for your calibration? It doesn't hurt to do a loopback measurement every time you set up to do measurements just to make sure everything is working properly. If you can get a clean loopback then there shouldn't be any issues related to sound card config.

If the worst comes to the worst, find the holm impulse directory under your user home directory and delete all of the files there (usually a couple of xmls and a zip with the measurements in it (make a backup first). Sometimes something gets corrupted and this is the only way to get it working properly again. Note that all settings will return to defaults if you do this.

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Old 14th February 2014, 08:33 AM   #666
pet007 is offline pet007  Czech Republic
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Thanks, it's possible, that there were some other apk's running during measurement (maybe youtube in IE + SoundForge). I'll try it once again on pure Win7. Anyway. I've stored only this screenshot frm loopback test (I haven't got original Holm data now :/ )
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Old 14th February 2014, 09:03 AM   #667
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Hmmm I definitely thing that something is not right. One of your apps may be turning on EQ on your sound card's dsp. there is a lot of rolloff there from about 5Khz on. I would not expect that at all on a loopback measurement if everything is working properly. maybe 0.2 or 0.3db by 20Khz.

Attached is a loopback measurement of my usb focusrite 2i2 (after calibration) set at 96Khz.

Note that the attached result is VERY flat, and not all cards can be expected to be this good, however I would expect a better result than the one you have shown.

Double check all the settings for your sound card especially any for effects or eq (making sure they are off).

Tony.
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Old 9th April 2014, 01:09 AM   #668
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Tony:
I am guessing that your loop back measurement looks so flat is that you are driving it into clipping. Certainly the way it drops off at low and high frequencies indicates this.
Try re-measuring at a number of different levels and see how the response changes.

AJ
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Old 9th April 2014, 03:50 AM   #669
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Hi Andrew, I don't believe so, but I can retest The graph shows at approx -6db and holm will normally indicate if clipping occurred. I have had that issue once before where I could not believe my measurement of a driver could be so flat. It wasn't

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Old 16th April 2014, 03:08 AM   #670
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For those of us that don't have anechoic chambers, huge baffle boards and mega thousand dollar calibrated measurement mics, what would be be best way to measure the FR of a particular driver? Nearfield?

Of course, an SPL measurement wouldn't be accurate except to ones own measurement parameters. Meaning always use the same gain on the amp and the same distance from the speaker.
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