Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 294 - AVS Forum
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post #8791 of 13328 Old 02-15-2014, 11:27 AM
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Originally Posted by jim19611961 View Post
 
Quote:
Originally Posted by kbarnes701 View Post

LOL. No way, Jim. I didn’t realise you already had the other sub when I made my first post on this subject.  Remember you are talking to the guy who is not using his HT at all right now, because of my Submersive amp failure. I'd rather not use the HT at all than use it with just one sub! wink.gif

New HP+ amp master/slave is being shipped to me Monday.... 4000 watts of woofage...

Mains = 350w x2
Sub 1 = 250w
Sub 2 = 100w

I think your wattage Rabbit hole is much deeper than mine smile.gif


FYI, all the wattage disparity works out in my case because of efficiency and attenuation differences. Sub 1 is more efficient than my mains. Sub 2 is attenuated compared to Sub 1.

 

I am sure that 4,000 watts of woofage is overkill here, in my small room. Headroom is one thing, but headroom is another ;) But that's the amp Mark offers these days with the SubMs. If you have one HP+ in each sub, then it's 2,400 watts per sub. But if you use the master/slave arrangement (which is massively less costly) then the combined woofers drop to a 2 ohm load, so the amp delivers 4000 watts, but has to power two subs (4 x 15 inch drivers).

 

On the rest of the (7) speakers I have a combined 1,650 watts. 

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post #8792 of 13328 Old 02-15-2014, 11:57 AM
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Originally Posted by artur9 View Post

Given this is the measurement thread, how would one go about measuring the headroom?

I "measured" what I was lacking in headroom (w/Iron Man) by the amount I needed to reduce the master volume from my typical level until the bottoming stopped. I doubled up on subs and was able to listen at my typical MVP level. The deficit was about 4dB.

Jeff
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post #8793 of 13328 Old 02-15-2014, 02:32 PM
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I am working to get REW setup and am having some difficulty. I am using a UMIK-1 and everything looked to be set up normal. When I select Measure I get the error "SPL meter audio input not available"

Any ideas?

The Moving Pictures Theater Construction Thread:
http://www.avsforum.com/t/1462881/th...ruction-thread

Houston GTG - Summer 2014
http://www.avsforum.com/forum/61-are...l#post26079610
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post #8794 of 13328 Old 02-15-2014, 02:53 PM
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Originally Posted by markus767 View Post

How do other locations within the listening area look like? Is that graph smoothed?

The graph is 250ms gate, 1/24th oct smoothed.

I haven't done readings for other seating positions.

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post #8795 of 13328 Old 02-15-2014, 03:02 PM
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Originally Posted by jim19611961 View Post

The graph is 250ms gate, 1/24th oct smoothed.

I haven't done readings for other seating positions.

I wasn't talking about "other seating positions" but your listening area. You do have two ears separated by about 15cm, don't you? I always measure multiple points around the left and right ear even if the goal is to optimize just a single seat.
1/24 smoothing should be ok but to be sure I'm always looking at unsmoothed data too.
250ms is too short. I'm using 500ms and more for low frequencies.

Markus

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post #8796 of 13328 Old 02-15-2014, 03:21 PM
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Originally Posted by markus767 View Post

I wasn't talking about "other seating positions" but your listening area. You do have two ears separated by about 15cm, don't you? I always measure multiple points around the left and right ear even if the goal is to optimize just a single seat.
1/24 smoothing should be ok but to be sure I'm always looking at unsmoothed data too.
250ms is too short. I'm using 500ms and more for low frequencies.

Good points. I will get to multiple positions eventually.

I did look at ungated unsmoothed responses, and they were not much different. Omnimic only allows no gate, 250ms, and continuously variable 75ms-0.

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post #8797 of 13328 Old 02-15-2014, 09:02 PM
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Originally Posted by pepar View Post

reduce the master volume from my typical level until the bottoming stopped
Jeff

Seems like you did it by ear? I don't know what bottoming out sounds like.
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post #8798 of 13328 Old 02-16-2014, 06:50 AM
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Originally Posted by artur9 View Post

Seems like you did it by ear? I don't know what bottoming out sounds like.

It is a terribly disturbing mechanical knocking sound that you do not want to heard from a speaker. You can measure improvements from adding subs, i.e. additional headroom, smoothing of response. But I don't know of any way to measure, in advance, that you need more headroom. So "by ear" is the only indication.

Jeff
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post #8799 of 13328 Old 02-16-2014, 08:39 AM
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People sometimes recommend making measurements of preamp outputs in order to find out exactly what corrections are being made by EQ software or processors so that the corrections can be compared to the measured results. Unfortunately, I can't find any mention of this procedure in the Guide provided at the top of this thread.

What procedure is recommended and what devices are needed to do this?

Selden

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post #8800 of 13328 Old 02-16-2014, 08:49 AM
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Originally Posted by Selden Ball View Post

People sometimes recommend making measurements of preamp outputs in order to find out exactly what corrections are being made by EQ software or processors so that the corrections can be compared to the measured results. Unfortunately, I can't find any mention of this procedure in the Guide provided at the top of this thread.

What procedure is recommended and what devices are needed to do this?

The pre-out measurement process is described, starting on page 81.
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post #8801 of 13328 Old 02-16-2014, 08:51 AM
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Quote:
Originally Posted by AustinJerry View Post

Quote:
Originally Posted by Selden Ball View Post

People sometimes recommend making measurements of preamp outputs in order to find out exactly what corrections are being made by EQ software or processors so that the corrections can be compared to the measured results. Unfortunately, I can't find any mention of this procedure in the Guide provided at the top of this thread.

What procedure is recommended and what devices are needed to do this?

The pre-out measurement process is described, starting on page 81.

Thanks! Found it. I was searching for the word "preamp" which isn't used in the document. frown.gif

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post #8802 of 13328 Old 02-16-2014, 10:56 AM
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Is anyone here using jriver with HTPC? If so, can you show how to use REW to measure jriver parametric eq? I added 3db gain at 46hz with bandwidth Q of 4 with jriver pEq to flatten my respond further but I just don't know what REW graph looks like. Thanks.

This graph is without jriver peq.
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post #8803 of 13328 Old 02-16-2014, 11:37 AM
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Quote:
Originally Posted by tvuong View Post

Is anyone here using jriver with HTPC? If so, can you show how to use REW to measure jriver parametric eq? I added 3db gain at 46hz with bandwidth Q of 4 with jriver pEq to flatten my respond further but I just don't know what REW graph looks like. Thanks.

This graph is without jriver peq.
You have 3 options; wasapi loopback, asio line in or an RTA method. I think you need to search on interact for more details though, seems a bit O/T for this thread. One example thread -http://yabb.jriver.com/interact/index.php?topic=80035.0
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post #8804 of 13328 Old 02-16-2014, 12:02 PM
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Quote:
Originally Posted by AustinJerry View Post
 

The pre-out measurement process is described, starting on page 81.

 

Jerry, for the first time, today I thought I would enter my UMM-9 sensitivity factor into my cal file. Following the advice in the Guide, I clicked through to the Dayton site and located the place where one enters the serial number of the mic. I then removed my mic from its case to check for the Serial No and guess what?  My mic doesn't have one!  There is a space for it on the label but it is blank. I have no idea why. It may be worth mentioning next time you revise the Guide that some UMM-6 mics (mine was supplied by Herb which may be something to do with it) do not have a Serial No, in which case one needs to use the (perfectly acceptable) manual SPL calibration procedure you describe.

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post #8805 of 13328 Old 02-16-2014, 12:14 PM
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Interesting that the SN is missing, Keith. Did you check the set of calibration files you received from Herb? AFAIK, Herb includes the SN of the calibrated mic in the report he sends along with the calibration files (usually a PDF file showing the measurement graph).
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post #8806 of 13328 Old 02-16-2014, 12:28 PM
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Originally Posted by AustinJerry View Post

Interesting that the SN is missing, Keith. Did you check the set of calibration files you received from Herb? AFAIK, Herb includes the SN of the calibrated mic in the report he sends along with the calibration files (usually a PDF file showing the measurement graph).

 

Ah - no I didn't in fact, Jerry. I will check it later and report back. Thanks.

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post #8807 of 13328 Old 02-16-2014, 12:35 PM
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Maybe CS buys them in bulk, un-serialized (and un-calibrated), and then calibrates?
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post #8809 of 13328 Old 02-16-2014, 01:05 PM
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Originally Posted by 3ll3d00d View Post

You have 3 options; wasapi loopback, asio line in or an RTA method. I think you need to search on interact for more details though, seems a bit O/T for this thread. One example thread -http://yabb.jriver.com/interact/index.php?topic=80035.0
Thanks for link.
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OK gang I got my REW up and working and this is my first measurement. 

I am using the UMIK-1 and a Display port adapter to HDMI from a PC for output.

The current room has no treatments and no carpet.

 

Thoughts?   Why does it fall off so quickly after 4K

 

Edited pic for format

 


The Moving Pictures Theater Construction Thread:
http://www.avsforum.com/t/1462881/th...ruction-thread

Houston GTG - Summer 2014
http://www.avsforum.com/forum/61-are...l#post26079610
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post #8811 of 13328 Old 02-17-2014, 04:33 AM
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Maybe CS buys them in bulk, un-serialized (and un-calibrated), and then calibrates?

 

My thoughts tambien.

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post #8812 of 13328 Old 02-17-2014, 08:42 AM
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My thoughts tambien.

Did you check to see if the SN is recorded in the file name of the calibration report?
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post #8813 of 13328 Old 02-17-2014, 09:49 AM
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Quote:
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Quote:
Originally Posted by kbarnes701 View Post

My thoughts tambien.

Did you check to see if the SN is recorded in the file name of the calibration report?

 

I did thanks, Jerry, and it is.  I think I will continue to use the manual method though as there seems to be some doubt with the UMM-6 wrt to the accuracy of the sensitivity file (according to the Guide). It is only the work of a moment to check the mic against the SPL meter, and at least then I know it has been done properly. Or am I missing something?

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post #8814 of 13328 Old 02-17-2014, 10:08 AM
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Originally Posted by kbarnes701 View Post

I did thanks, Jerry, and it is.  I think I will continue to use the manual method though as there seems to be some doubt with the UMM-6 wrt to the accuracy of the sensitivity file (according to the Guide). It is only the work of a moment to check the mic against the SPL meter, and at least then I know it has been done properly. Or am I missing something?

I continue to advocate a manual calibration as being the most reliable approach.
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post #8815 of 13328 Old 02-17-2014, 10:18 AM
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Quote:
Originally Posted by kbarnes701 View Post

I did thanks, Jerry, and it is.  I think I will continue to use the manual method though as there seems to be some doubt with the UMM-6 wrt to the accuracy of the sensitivity file (according to the Guide). It is only the work of a moment to check the mic against the SPL meter, and at least then I know it has been done properly. Or am I missing something?

I continue to advocate a manual calibration as being the most reliable approach.

 

That's good enough for me then, Jerry.  

 

There was much fuss about it back in the thread IIRC but I never really understood why. It literally takes less than 30 seconds and you know it's been done right. 

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What is the difference between the UMIK-1 sold by MiniDSP vs. the version sold by Cross Spectrum? Both provide the calibration file, but there is a $20 difference in price.

Thanks.
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post #8817 of 13328 Old 02-17-2014, 11:40 AM
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Cross Spectrum provides calibrations specific to the microphone that you buy instead of a generic calibration. It also includes a calibration for use with "grazing incidence" audio i.e. for using the microphone with a 90 degree orientation: with the microphone pointed toward the ceiling and speakers distributed around the room.

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post #8818 of 13328 Old 02-17-2014, 12:08 PM
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What is the difference between the UMIK-1 sold by MiniDSP vs. the version sold by Cross Spectrum? Both provide the calibration file, but there is a $20 difference in price.

Thanks.

 

I encourage you to read the Guide (link in my sig).  Note 3 on page 3 answers your question.  There are two other sections that describe the microphones and their differences.

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post #8819 of 13328 Old 02-17-2014, 12:53 PM
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I encourage you to read the Guide (link in my sig).  Note 3 on page 3 answers your question.  There are two other sections that describe the microphones and their differences.

Ah, correct. I had that downloaded on my laptop but haven't read through it. Thanks for the reminder.
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post #8820 of 13328 Old 02-17-2014, 12:55 PM
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Quote:
Originally Posted by Selden Ball View Post

Cross Spectrum provides calibrations specific to the microphone that you buy instead of a generic calibration. It also includes a calibration for use with "grazing incidence" audio i.e. for using the microphone with a 90 degree orientation: with the microphone pointed toward the ceiling and speakers distributed around the room.

Thanks Selden. Will head to your site and place an order. Much appreciated.
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