Speaker design/test software

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chris661
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Re: Speaker design/test software

Post by chris661 » Fri Nov 01, 2019 10:47 am

Sounds very low.

Here's a test. Open REW, and click the "levels" button at the top. With the mic input gain all the way up on the soundcard, tap on the side of the microphone with a fingernail. You should get red lights flashing on the soundcard to indicate the input is being overloaded, and the level meters on REW should respond accordingly.

If you don't get red lights, you might have the input pad engaged. At full gain, it's easy to overload the input and that's what we're trying to do at the moment.
If you get red lights but the REW meters don't move, you need to double-check the I/O selection under REW settings. You might still be using the laptop's built-in microphones. You can confirm by moving the measurement mic away and tapping on the laptop. The mics on mine are in the bezel above the screen.


Once you're up and running, the test sweep doesn't have to be particularly loud - you want it to be above the background noise (NB - if there is background noise, running multiple sweeps will help, as REW looks for the signals that are common to all sweeps, and ignores one-off events) of the room.
As you push the volume up, you're more likely to induce rattles in the room and hit non-linearities in the speaker. It can be useful to go there at times, but we're not there yet.

Chris
If you can see the cone move regularly, you haven't got enough speaker.

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IslandPink
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Re: Speaker design/test software

Post by IslandPink » Fri Nov 01, 2019 2:48 pm

chris661 wrote:
Fri Nov 01, 2019 10:47 am
Sounds very low.
Here's a test. Open REW, and click the "levels" button at the top. With the mic input gain all the way up on the soundcard, tap on the side of the microphone with a fingernail. You should get red lights flashing on the soundcard to indicate the input is being overloaded, and the level meters on REW should respond accordingly.
I get the bar chart on the right going up to near the top, but not clipping. I do get a red 'Clip' LED on the UMC box.
But I'm not sure I have this correct, how would I do this "With the mic input gain all the way up on the soundcard" ? Is this done via REW or via the Laptop's control panel option ? I have the mic input gain turned up on the pot on the UMC btw.

I might take a couple of screenshots to upload
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Nick
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Re: Speaker design/test software

Post by Nick » Fri Nov 01, 2019 2:52 pm

I get the bar chart on the right going up to near the top, but not clipping. I do get a red 'Clip' LED on the UMC box.
I am guessing the Bar chart is on the laptop? I am thinking that Chris has hit the mark where he wonders if you are using the laptop mike. Disconnect the mike from the soundcard and see if the little input you have goes away or not.
Resistance isn't futile it's V / I.

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IslandPink
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Re: Speaker design/test software

Post by IslandPink » Fri Nov 01, 2019 3:12 pm

No, thanks, but checked that. In fact it's along the same lines as what I found a couple of days ago- in 'Tools' the XLR input to the UMC is defaulted to 'R', which in this case is 'Input 2' on the UMC. I have the microphone plugged into the Input 1 which must be 'L'. Getting a signal now I changed it to 'L' input ; high level on the white noise test - so will see if I can now adjust and get a meaningful test and report back later.
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chris661
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Re: Speaker design/test software

Post by chris661 » Sat Nov 02, 2019 11:07 am

IslandPink wrote:
Fri Nov 01, 2019 2:48 pm

I get the bar chart on the right going up to near the top, but not clipping. I do get a red 'Clip' LED on the UMC box.
But I'm not sure I have this correct, how would I do this "With the mic input gain all the way up on the soundcard" ? Is this done via REW or via the Laptop's control panel option ? I have the mic input gain turned up on the pot on the UMC btw.

I might take a couple of screenshots to upload
When I mention a control on the soundcard, I'm referring to the black box that is the UMC202HD.

Sounds like you've figured out the routing. Set the output levels to something sensible, and use the input gain control on the UMC202HD to set how much level is going back into REW.

FWIW, you can also set up to do impedance sweeps. You'll need a couple of 1/4" patch cables (1-2' should do, you'll need to cut them in half) and a measured 100ohm (or close - you'll tell REW what the value is) resistor.
For now, let's get some frequency response curves done.

Chris
If you can see the cone move regularly, you haven't got enough speaker.

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