# UMIK-1 Mic Measurement Help



## PC620 (Feb 23, 2014)

For some reasons I cannot get UMIK-1 mic to measure above 800hz today. I've taken many measurements of my full-range speakers. I made sure I set the lower and upper limits prior to starting the tests.

Please let me know what I might be doing wrong here:scratch:. Thank you.


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## HifiZine (Feb 7, 2013)

Hi there, what other devices are in the chain? It looks like you have a crossover filter set at ~180 Hz.

Your impulse also looks a bit unusual... Just wondering if you've checked it in the earlier good measurements?


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## PC620 (Feb 23, 2014)

Thanks Hifizine.

I have 4-way speakers and running them in bi-amp mode just started today. For LF drivers, I have Ashly XR-2001 between preamp and mono amp and I set the xover freq at ~350Hz on the Ashly. Not sure why you think the filter is set at ~180Hz. Any suggestions on how I can verify if it's at 180Hz or 350Hz?

Thanks.


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## jtalden (Mar 12, 2009)

PC620 said:


> For some reasons I cannot get UMIK-1 mic to measure above 800hz today. I've taken many measurements of my full-range speakers. I made sure I set the lower and upper limits prior to starting the tests.
> 
> Please let me know what I might be doing wrong here:scratch:. Thank you.


The info on your measurement shows the sweep was set as 20 - 795 Hz for this measurement.

When you open the "measure" dialog box for your next measurement make sure the range is set as you desire.


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## PC620 (Feb 23, 2014)

jtalden said:


> The info on your measurement shows the sweep was set as 20 - 795 Hz for this measurement.
> 
> When you open the "measure" dialog box for your next measurement make sure the range is *set as you desire*.


I got the mic set up for quick check this morning, and you were right that the upper limit was set at 800Hz by default. For this particular case, REW's lower and upper limits are 20Hz to 24KHz and I had been entering values above 24KHz during my tests yesterday. 

Here's what I noticed (on my Win 7 64bit laptop) this morning, REW will not accept any values above 24KHz. I am not sure why that is. 

Does anyone know or can explain this? 

Thank you.


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## Wayne A. Pflughaupt (Apr 13, 2006)

It’s because that’s the limitation written into the program. It will go all the way down to 0 Hz on the low end, though – not sure what you were seeing that limited at 20 Hz.

Regards, 
Wayne


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## PC620 (Feb 23, 2014)

Wayne A. Pflughaupt said:


> It’s because that’s the limitation written into the program. It will go all the way down to 0 Hz on the low end, though – not sure what you were seeing that limited at 20 Hz.
> 
> Regards,
> Wayne


Thanks Wayne. As for the lower end, I didn't try to change to lower than 20 Hz but you are correct of course that it will go down to 0 Hz (just confirmed now). 

*Anyway I can confirm what my actual x-over is at now? * I set the dial on Ashly to ~350 Hz but the last reply I got here was that it looks like it was set at ~180 Hz from the graph and data provided


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## jtalden (Mar 12, 2009)

The max freq we can set half the sample freq.
So if our sample freq is 48k then 24k is the max freq that can be measured. Google "Nyquist frequency" for an explanation.


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## PC620 (Feb 23, 2014)

Here's my latest room measurements with response range from 10 - 24 KHz. These are stereo setup and actively biamping the LF drivers. UMIK-1 mic with calibrated file from CS using narrow band @0 degree.

I am still playing with the adjustments on the Ashly so don't really know what I am doing yet. Setting xover at ~350 Hz right now.

Any input is much appreciated.


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## Wayne A. Pflughaupt (Apr 13, 2006)

That’s a curious crossover frequency. What are you dividing frequencies between?

Regards, 
Wayne


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## PC620 (Feb 23, 2014)

Wayne A. Pflughaupt said:


> That’s a curious crossover frequency. What are you dividing frequencies between?
> 
> Regards,
> Wayne


Here's the FR ranges for my 4-way JBL 250Ti LE. MF driver dia is 8" and 14" for the LF driver but both have exact freq ranges (20 Hz - 1.2 kHz). JBL xover specs for these are: 350 Hz, 1.2 kHz and 5.5 kHz. I set the Ashly to 350Hz for the active bi-amping the LF drivers.

When I get a chance, I will isolate the stock passive network from the active path and see how it sounds. Right now, I am feeding Low output from Ashly through the stock passive network for the LF drivers.

Thanks.


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## HifiZine (Feb 7, 2013)

Hi again, sounds like you're making progress 



PC620 said:


> When I get a chance, I will isolate the stock passive network from the active path and see how it sounds. Right now, I am feeding Low output from Ashly through the stock passive network for the LF drivers.


If you have the stock passive network in place, then the effect on the driver will be the active and passive crossover in series. Perhaps the passive is rolling off earlier than 350 Hz? If you're using an active crossover, you really do need to remove the passive crossover (between the same set of drivers) or you can't really do much. Assuming the goal is to use the active crossover between the bass driver and the mid/high network to replace the passive components, I'd suggest something like the following:

* With the active crossover completely disconnected/removed from play, *separately* measure the LF driver and the mid-high network. That will show you where the designed crossover frequency is.

* Figure out which components are responsible for the filters between the LF and the mid-high drivers. Bypass or remove them, and measure again (separately). You should see a flattish response through the crossover point and then a gradual rolloff.

* Re-introduce the active crossover with the same frequency as determined in step 1.

* Tweak, remeasure, tweak, ...

HTH 

The other point is that your measurements need to try and isolate from the room as much as possible since you're doing speaker design not room acoustics.


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## PC620 (Feb 23, 2014)

HifiZine said:


> Hi again, sounds like you're making progress
> 
> 
> 
> ...


Thanks. There are two pairs of binding posts on back of each enclosure (one for LF and the other for MF/HF/UHF) and they can be setup as full-range or actively bi-amp via two jumpers on binding posts. Removing these jumpers isolate the LF network from the other.

See attached schematic for these 4-way speakers. I will proceed with the plan to isolate the stock passive NW before the drivers so it's purely active bi-amping on for the LF drivers. 

By "isolating the room", you meant measure at close to each driver as possible (like 1-2 feet away)?? Thanks.


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## HifiZine (Feb 7, 2013)

PC620 said:


> By "isolating the room", you meant measure at close to each driver as possible (like 1-2 feet away)?? Thanks.


A foot might be a bit extreme esp when dealing with the mid-high network, usually a meter, give or take. If you can get it all outside that may help. But it sounds like you're on the right track


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