Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 365 - AVS Forum
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Audio Theory, Setup, and Chat > Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs
HDgaming42's Avatar HDgaming42 11:57 AM 08-08-2014
Quote:
Originally Posted by markus767 View Post
The bugs I had reported to John have been fixed. Now you can use PEQ up to 20kHz. It was limited to 10kHz before.
Thanks--I can't read the release notes right now. I heard there was something to do with greater accuracy when using a miniDSP? Any word on the Room Simulator? I'm dying here! Can't wait to try out the new beta...

artur9's Avatar artur9 09:27 PM 08-08-2014
Quote:
Originally Posted by jim19611961 View Post


In my case, the finishing line keeps moving

As I moved the ETC firstly to -20db, then to -25db, then to -30db, I felt like there were noticeable improvements in sound. Particularly in soundstage and low level detail. Unfortunately, along with this, things got more dead as well, and had to impliment my Haas Kickers to compensate. Just something to keep in mind as you continue to reduce reflection magnitudes.
Isn't the deadness why diffusers are recommended a bit more over absorbers?
jim19611961's Avatar jim19611961 10:22 PM 08-08-2014
Quote:
Originally Posted by artur9 View Post
Isn't the deadness why diffusers are recommended a bit more over absorbers?
Yes. But diffusers have the constraints of 1) minimum distance 2) the timing of their arrival. Many do not like using diffusion for early reflections, leaving the later arriving ones where diffusion is preferred and most often used.

A lot of situations arise, especially in smaller rooms, where you cant employ diffusers without significant intrusion to ones ISD gap. There just isn't the dimensions or space necessary for significantly delayed diffusion via diffusers. And often, you cant get far enough away from them either. In most cases. 5-8 feet away is often the requirement. Add to this, significantly more costly.

I like what diffusion does and how it works. But IMO, their tricky to predict whether their effect will be a welcome one or not. There are more factors than just timing. But this one alone accounts for their limited ability to be effective in a lot of common rooms.
jevansoh's Avatar jevansoh 02:35 AM 08-09-2014
Jerry et al,

When using GIK 244 panels, please note that they have a thin membrane installed over the insulation which will cause reflections above 4khz.

So I'm not sure you need "extra" panels on your back wall. Instead, you need "different" panels.

Remember, the 244 panels are sold as Bass Traps not full band absorbers.

I don't recall if the 242's have this membrane or not. You may want to ask Brian or Glenn.

They have changed the insulation they use recently and I believe they've even changed the fabric they use now, so it is possible they no longer use the membrane, but I've not heard that specifically.

I would try putting some 242's in place on the back wall and also try (even temporarily, since you don't like building them) bare insulation on the back wall, only, instead of in addition to the 244's and see if that still fixes your reflections.

If so, you won't have to use as many panels.

Hope this helps,

--J
AustinJerry's Avatar AustinJerry 09:12 AM 08-09-2014
Thanks a lot, J! I was enjoying my morning coffee when I noticed you had posted in this thread, and I fell out of my chair, spilling coffee everywhere. Seriously, it is good to see you are alive and well. Perhaps you could favor us with an update on your own home theater project, assuming you have had time to move it forward. I'm sure many of us would enjoy hearing some news.

As for the GIK panels, I actually have 242 panels on the back wall. I will ask Brian Pape about whether GIC still is using membranes, which would be good information to know. Regardless, I always appreciate feedback.
AustinJerry's Avatar AustinJerry 09:23 AM 08-09-2014
Quote:
Originally Posted by jim19611961 View Post


In my case, the finishing line keeps moving

As I moved the ETC firstly to -20db, then to -25db, then to -30db, I felt like there were noticeable improvements in sound. Particularly in soundstage and low level detail. Unfortunately, along with this, things got more dead as well, and had to impliment my Haas Kickers to compensate. Just something to keep in mind as you continue to reduce reflection magnitudes.
Now you have me worried, Jim. How were you able to assess that your room had become too dead? Was it with listening tests, or an interpretation of an objective measurement? I believe some use the RT-60 to measure this, but I think I have heard some experts don't consider that it is a useful measurement.

Here is a typical RT60 graph:


jim19611961's Avatar jim19611961 09:30 AM 08-09-2014
Quote:
Originally Posted by AustinJerry View Post
Now you have me worried, Jim. How were you able to assess that your room had become too dead? Was it with listening tests, or an interpretation of an objective measurement? I believe some use the RT-60 to measure this, but I think I have heard some experts don't consider that it is a useful measurement.

Here is a typical RT60 graph:

Im my case, the determination of becoming dead was primarily through listening, therefore completely subjective. As far as RT60 goes, I still don't know whether it tells me (us) anything useful.
AustinJerry's Avatar AustinJerry 10:21 AM 08-09-2014
Well, I'll find out soon enough. The additional ceiling panels arrive Tuesday.
AustinJerry's Avatar AustinJerry 01:35 PM 08-09-2014
Quote:
Originally Posted by AustinJerry View Post
I will ask Brian Pape about whether GIC still is using membranes, which would be good information to know.
Bryan's response:

It’s not going to cause full reflection. It just knocks down the higher frequency absorption from about a 1.0 to about 0.8. Still perfectly fine for reflection duties.

Bryan Pape (bpape)
Lead Acoustician
GIK Acoustics
artur9's Avatar artur9 10:33 AM 08-10-2014
Has anyone had the UMM-6 just fail on them?

Mine is no longer visible via any of the control panels. It did this a few weeks back but eventually I got it to work by plugging into different computers and then plugging it in the measurement laptop.

Now, nothing.

I need a new one regardless as the poor thing fell and broke its crown. But I'm leaning against UMM6 at the moment for a replacement.

Very frustrating as now I won't be able to do my flanking subwoofer experiments or minidsp experiments.
AustinJerry's Avatar AustinJerry 02:02 PM 08-10-2014
Quote:
Originally Posted by artur9 View Post
Has anyone had the UMM-6 just fail on them?

Mine is no longer visible via any of the control panels. It did this a few weeks back but eventually I got it to work by plugging into different computers and then plugging it in the measurement laptop.

Now, nothing.

I need a new one regardless as the poor thing fell and broke its crown. But I'm leaning against UMM6 at the moment for a replacement.

Very frustrating as now I won't be able to do my flanking subwoofer experiments or minidsp experiments.
The USB cable on my UMM-6 failed. At first, I though the mic was bad, but by chance I tried a different cable, and the mic was OK. If you haven't tried yet, switch cables.

I have both the UMM-6 and the UMIK-1. IMO, the barrel of the UMIK-1 is a bit sturdier than the UMM-6. I dropped the UMM-6, and the barrel snapped in two. It is now taped together with gaffer's tape and still functional.

I tested both mics using REW and found them to be functionally equivalent for measurement purposes.
artur9's Avatar artur9 07:31 PM 08-10-2014
Quote:
Originally Posted by AustinJerry View Post
The USB cable on my UMM-6 failed. At first, I though the mic was bad, but by chance I tried a different cable, and the mic was OK. If you haven't tried yet, switch cables.
Too late for that. The mic did fall about 2ft onto a carpeted floor and the barrel snapped as you described. I am not very impressed with its quality.

I don't think it was the cable, though. Sometimes when I plugged it in the LED would blink in 3 times then repeat 3 times. And it was significantly dimmer than it should have been.

Quote:
Originally Posted by AustinJerry View Post
I have both the UMM-6 and the UMIK-1. IMO, the barrel of the UMIK-1 is a bit sturdier than the UMM-6. I dropped the UMM-6, and the barrel snapped in two. It is now taped together with gaffer's tape and still functional.

I tested both mics using REW and found them to be functionally equivalent for measurement purposes.
Those are the only choices for calibrated USB mics?
AustinJerry's Avatar AustinJerry 08:03 PM 08-10-2014
Quote:
Originally Posted by artur9 View Post

Those are the only choices for calibrated USB mics?
Do you have a problem with the UMIK-1? It is a perfectly good mic.

Of course, you could opt for a "legacy" setup using a calibrated EMM-6, which requires phantom power from an external sound card. The SoundBlaster X-Fi is a good choice. Of course, the legacy setup doesn't use HDMI, so you lose the convenience of that connection method. And it's somewhat more difficult to set up and run as well.
artur9's Avatar artur9 08:10 PM 08-10-2014
Quote:
Originally Posted by AustinJerry View Post
Do you have a problem with the UMIK-1? It is a perfectly good mic.
Not at all. Just confirming that those are the choices.

IIRC I got the UMM because the UMIK was out of stock at that time. I see that the UMIK will start shipping from CSL on 8/11.
Martycool007's Avatar Martycool007 06:22 AM 08-11-2014
Would any of you guys happen to have a calibrated UMIK-1 or a calibrated UMM-6 that you would be willing to loan out for a couple of weeks? I will be happy to pay rent!

I have cancer and can't work at the moment, and unfortunately that means that I can't afford to drop $100 on a new one.

If anyone might be willing to loan theirs out, I would be forever greatful!
Saril's Avatar Saril 11:11 AM 08-11-2014
Quote:
Originally Posted by artur9 View Post
Has anyone had the UMM-6 just fail on them?

Mine is no longer visible via any of the control panels. It did this a few weeks back but eventually I got it to work by plugging into different computers and then plugging it in the measurement laptop.

Now, nothing.

I need a new one regardless as the poor thing fell and broke its crown. But I'm leaning against UMM6 at the moment for a replacement.

Very frustrating as now I won't be able to do my flanking subwoofer experiments or minidsp experiments.
I am new to REW but did just recently get my calibrated UMIK-1 from CSL. Using Jerry's guide (awesome BTW - thanks) I wanted to verify my noise floor with a SPL meter. Per the guide, I went online, got the sensitivity value and loaded it into the 90-degree narrow band cal file. I was expecting the SPL meter and REW to be within a few dB of each other at the noise floor range. The UMIK-1 was reading around 40-42 dB C/slow but the SPL was reading around 52 - 54 dB C/slow. The room was very quiet. I remove the sensitivity entry and performed the manual calibration @ 80dB C/slow, but the noise floor results did not change much at all. However, both read very close at values over 65 dB. So I was at the point - is it the UMIK-1 or my new SPL meter. I had an old Radio Shack analog SPL and verified all three at close @80 dB but the RS meter does not go below 50 dB so could not test low range.. The new SPL goes to 30dB according to the specs. So I then tried an IOS app, SPLnFFT which also has 30 - 130 dB range. I installed on both IPhone & IPad. Noise floor reading for both closer to the REW reported value but not exactly the same - IPhone reported 43 dB, IPad reported 39 dB and REW reported around 42ish - all values seem to vary a few dB. I decided to try the SPL and IOS devices inside my wife's very quiet SUV just to see if the SPL meter would indicate a relative change, i.e., a lower value. Inside SUV, IPhone reported 34 dB, IPad reported 37 and the new SPL reported 51 dB. So I was convinced that the problem was the new SPL meter, not the UMIK-1. I returned the SPL meter and got a replacement and it's doing the same exact thing- won't measure noise floor lower than 50 dB C/slow. I am at my wits end. I just don't feel comfortable with a $100 SPL meter not agreeing with REW at the low levels.
Any advice appreciated and sorry for this long post.
AustinJerry's Avatar AustinJerry 12:01 PM 08-11-2014
Quote:
Originally Posted by Martycool007 View Post
Would any of you guys happen to have a calibrated UMIK-1 or a calibrated UMM-6 that you would be willing to loan out for a couple of weeks? I will be happy to pay rent!

I have cancer and can't work at the moment, and unfortunately that means that I can't afford to drop $100 on a new one.

If anyone might be willing to loan theirs out, I would be forever greatful!
Marty, as I have mentioned before, I have both the UMM-6 and the UMIK-1, both CSL-calibrated. I would be willing to loan you the UMM-6 for a while, if you agree to post your measurements here in the thread. PM me with your mailing address and phone number so we can get the mic out to you.
ggsantafe's Avatar ggsantafe 05:56 PM 08-11-2014
Quote:
Originally Posted by AustinJerry View Post
Marty, as I have mentioned before, I have both the UMM-6 and the UMIK-1, both CSL-calibrated. I would be willing to loan you the UMM-6 for a while, if you agree to post your measurements here in the thread. PM me with your mailing address and phone number so we can get the mic out to you.
Nice gesture AJ
jjazdk's Avatar jjazdk 01:57 AM 08-12-2014
Well, it is kind of obvious, isn't it?

Your new cheap SPL meter has a lot of inherent idle noise, and thus cannot measure below a 50dB noise floor.

Anyone manufacturer claiming that their 100 USD SPL meter can measure 30dBSPL is not telling the truth.

Quote:
Originally Posted by Saril View Post
I am new to REW but did just recently get my calibrated UMIK-1 from CSL. Using Jerry's guide (awesome BTW - thanks) I wanted to verify my noise floor with a SPL meter. Per the guide, I went online, got the sensitivity value and loaded it into the 90-degree narrow band cal file. I was expecting the SPL meter and REW to be within a few dB of each other at the noise floor range. The UMIK-1 was reading around 40-42 dB C/slow but the SPL was reading around 52 - 54 dB C/slow. The room was very quiet. I remove the sensitivity entry and performed the manual calibration @ 80dB C/slow, but the noise floor results did not change much at all. However, both read very close at values over 65 dB. So I was at the point - is it the UMIK-1 or my new SPL meter. I had an old Radio Shack analog SPL and verified all three at close @80 dB but the RS meter does not go below 50 dB so could not test low range.. The new SPL goes to 30dB according to the specs. So I then tried an IOS app, SPLnFFT which also has 30 - 130 dB range. I installed on both IPhone & IPad. Noise floor reading for both closer to the REW reported value but not exactly the same - IPhone reported 43 dB, IPad reported 39 dB and REW reported around 42ish - all values seem to vary a few dB. I decided to try the SPL and IOS devices inside my wife's very quiet SUV just to see if the SPL meter would indicate a relative change, i.e., a lower value. Inside SUV, IPhone reported 34 dB, IPad reported 37 and the new SPL reported 51 dB. So I was convinced that the problem was the new SPL meter, not the UMIK-1. I returned the SPL meter and got a replacement and it's doing the same exact thing- won't measure noise floor lower than 50 dB C/slow. I am at my wits end. I just don't feel comfortable with a $100 SPL meter not agreeing with REW at the low levels.
Any advice appreciated and sorry for this long post.

Martycool007's Avatar Martycool007 04:59 AM 08-12-2014
Quote:
Originally Posted by AustinJerry View Post
Marty, as I have mentioned before, I have both the UMM-6 and the UMIK-1, both CSL-calibrated. I would be willing to loan you the UMM-6 for a while, if you agree to post your measurements here in the thread. PM me with your mailing address and phone number so we can get the mic out to you.
Hey Jerry, I just sent you a PM with my shipping and contact information. As I said in the PM, I am so appreciative of your willingness to loan me a mic for these projects that I have been wanting to complete forever!

Guys, we have a real gem here on this forum as Jerry has spent so much time in trying to help those of us who are less knowledgable.

When I receive the mic and start taking measurements I will most definitely be posting them in this forum and thread. Again, I am so greatful for this!
Saril's Avatar Saril 05:42 PM 08-12-2014
Quote:
Originally Posted by jjazdk View Post
Well, it is kind of obvious, isn't it?

Your new cheap SPL meter has a lot of inherent idle noise, and thus cannot measure below a 50dB noise floor.

Anyone manufacturer claiming that their 100 USD SPL meter can measure 30dBSPL is not telling the truth.
You may be right - all I can go by is the published specs. It seems strange that if my iPhone measured below 40 in the SUV then so should a dedicated SPL in the $100 range. Are noise floor values reported by the UMIK-1 reliable below 50dB C weighting? IIRC the USB interface imposes a limit on the lower range. Thanks for any feedback.
Zee-man's Avatar Zee-man 09:15 PM 08-13-2014
Newbie here with a few questions. I have a 2.2 system and I want to measure and find the best spots for my two subs. I've read quite a bit of this post and used AustinJerry's REW guide to get everything fired up, but I still have a few questions based on my specific task of measuring the subs.

What is the best way to measure and graph - L+subs, R+subs, and then L+R+subs? Is it better or even possible to only measure the subs?

Should I run tests with and without Audyssey? When running Audyssey, do I turn off dynamic EQ and dynamic volume?

With my PSA XV15se sub(s) gain set at 2:00, Audyssey set my level to -9. I confirmed with my Umik that the -9 setting matches the SPL of my mains, but I bumped the sub level to -3 to suit my taste. Should I use the -9 or -3 setting when taking measurements?

What specific measurements or graphs are are the most important for subs - waterfall, decay, spectrograms, ETC? I have two possible locations for the subs and one of the options have them placed inside built in cabinets. I've heard this is a big no-no and I'd like to see some measurements to back that up. Is there a specific graph that will show the "boomy bass" that everyone says is going to happen?

Should the Umik with the factory calibration file be set horizontally?

Thanks in advance.
AustinJerry's Avatar AustinJerry 09:53 PM 08-13-2014
Quote:
Originally Posted by Zee-man View Post
Newbie here with a few questions. I have a 2.2 system and I want to measure and find the best spots for my two subs. I've read quite a bit of this post and used AustinJerry's REW guide to get everything fired up, but I still have a few questions based on my specific task of measuring the subs.

What is the best way to measure and graph - L+subs, R+subs, and then L+R+subs? Is it better or even possible to only measure the subs?

Should I run tests with and without Audyssey? When running Audyssey, do I turn off dynamic EQ and dynamic volume?

With my PSA XV15se sub(s) gain set at 2:00, Audyssey set my level to -9. I confirmed with my Umik that the -9 setting matches the SPL of my mains, but I bumped the sub level to -3 to suit my taste. Should I use the -9 or -3 setting when taking measurements?

What specific measurements or graphs are are the most important for subs - waterfall, decay, spectrograms, ETC? I have two possible locations for the subs and one of the options have them placed inside built in cabinets. I've heard this is a big no-no and I'd like to see some measurements to back that up. Is there a specific graph that will show the "boomy bass" that everyone says is going to happen?

Should the Umik with the factory calibration file be set horizontally?

Thanks in advance.
OK, I'll try to address your question, maybe not in the same order as asked. It is nice that you have two subs, because you will likely be able to get better bass response with two vs. one sub.

When approaching a sub placement exercise, there are going to be some obvious placements that should be better than others, based on the characteristics of your listening room. The dimensions of the room will determine the axial standing waves in the room. You can download an Excel worksheet that will calculate your room modes here. Typical sub placements are in the nulls of room modes. The mid-point of a wall is a in a null, as are the 1/4 and 3/4 points along a wall. The placement exercise is to locate a sub in one of these spots and measure the results. Keep experimenting with different placements until you get the best measurements.

When experimenting to find the best location, measure each sub individually, then both subs combined. The main speakers should be turned off (carefully disconnect the wires). Measurements should be taken with Audyssey turned off? Why? Because an Audyssey calibration is good for only one speaker configuration. The minute you move a sub to a potential new location, the calibration is no longer valid. Optimize sub placement first, and then run Audyssey. And if anything changes, re-run the Audyssey calibration. Final measurements should always be taken with DEQ and Dynamic Volume turned off.

The gain setting on the subs does not really matter with respect to the smoothness of the frequency response. Make sure your mic is calibrated, and turn the gain on the subs enough that you are getting a level reading of 85-90dB. It is important, however, to make sure the two subs are gain-matched. If you go to the Audyssey thread, the Audyssey FAQ has an excellent write-up on how to properly gain-match your subs. The trick is to achieve a matched gain that also measures close to 75dB for the Audyssey calibration.

Optimize your sub locations by measuring frequency response. The waterfall graph is useful to assess bass resonance once you have found the best sub locations. If resonance is bad, it can be controlled by treating the room, not by moving the subs around. And the ETC graph is to measure higher frequency reflections, and is of no value in placing the subs. And when measuring, make sure the mic is in the MLP, pointed towards the ceiling, with the mic tip exactly at ear-height. Use the 90-degree calibration file.

There are several poor locations for subs. Inside a cabinet would be near the top of the list. Corner placement is usually not the best location either, although there may be exceptions. So, if you try placing them inside of a cabinet (ugh!), then what does "boomy bass" look like? The frequency response will be poor, and the resonance (waterfall) is probably going to be terrible. And most importantly, it will sound terrible.

So, you need to resign yourself to the fact that the best-sounding location for your subs may not be the most esthetically-pleasing location. Since you didn't comment on what your room looks like, and what freedoms you have in placement, I can't predict how easy this exercise is going to be. Getting good bass is a lengthy exercise--it took me several years before I could say that I had what I was looking for.

Good luck, and report back with progress and questions.
Alan P's Avatar Alan P 10:16 PM 08-13-2014
Quote:
Originally Posted by Zee-man View Post
Newbie here with a few questions. I have a 2.2 system and I want to measure and find the best spots for my two subs. I've read quite a bit of this post and used AustinJerry's REW guide to get everything fired up, but I still have a few questions based on my specific task of measuring the subs.

What is the best way to measure and graph - L+subs, R+subs, and then L+R+subs? Is it better or even possible to only measure the subs?

Should I run tests with and without Audyssey? When running Audyssey, do I turn off dynamic EQ and dynamic volume?

With my PSA XV15se sub(s) gain set at 2:00, Audyssey set my level to -9. I confirmed with my Umik that the -9 setting matches the SPL of my mains, but I bumped the sub level to -3 to suit my taste. Should I use the -9 or -3 setting when taking measurements?

What specific measurements or graphs are are the most important for subs - waterfall, decay, spectrograms, ETC? I have two possible locations for the subs and one of the options have them placed inside built in cabinets. I've heard this is a big no-no and I'd like to see some measurements to back that up. Is there a specific graph that will show the "boomy bass" that everyone says is going to happen?

Should the Umik with the factory calibration file be set horizontally?

Thanks in advance.
Jerry gave some great advice! I just wanted to address a couple points he missed.

Are you using HDMI to connect to your AVR? If so, then you can measure any channel you want (or combination of channels) including LFE only. Just change the output to the channel (in the preferences) you desire. Use the Timing Reference Output for additional channels.

You should measure at whatever sub trim level you plan on listening at.

The most important graphs for bass are; FR, waterfall, decay, spectrogram and distortion. The waterfall and spectrogram will help you most when looking for "boomy-ness". You want your decay to be less than 450ms if at all possible, less is better. Your decay will most likely be highest below 30hz, and there's not much you can do about that.
Saril's Avatar Saril 04:51 AM 08-14-2014
Quote:
Originally Posted by Zee-man View Post
Newbie here with a few questions. I have a 2.2 system and I want to measure and find the best spots for my two subs. I've read quite a bit of this post and used AustinJerry's REW guide to get everything fired up, but I still have a few questions based on my specific task of measuring the subs.

What is the best way to measure and graph - L+subs, R+subs, and then L+R+subs? Is it better or even possible to only measure the subs?

Should I run tests with and without Audyssey? When running Audyssey, do I turn off dynamic EQ and dynamic volume?

With my PSA XV15se sub(s) gain set at 2:00, Audyssey set my level to -9. I confirmed with my Umik that the -9 setting matches the SPL of my mains, but I bumped the sub level to -3 to suit my taste. Should I use the -9 or -3 setting when taking measurements?

What specific measurements or graphs are are the most important for subs - waterfall, decay, spectrograms, ETC? I have two possible locations for the subs and one of the options have them placed inside built in cabinets. I've heard this is a big no-no and I'd like to see some measurements to back that up. Is there a specific graph that will show the "boomy bass" that everyone says is going to happen?

Should the Umik with the factory calibration file be set horizontally?

Thanks in advance.
Jerry mentioned to make sure your UMIK is calibrated. What did you do to ensure calibration? I tried both methods (see my posts above) and am not confident with my results. I also am a newbie trying to get two subs integrated. Good luck!
AustinJerry's Avatar AustinJerry 06:56 AM 08-14-2014
Quote:
Originally Posted by Saril View Post
Jerry mentioned to make sure your UMIK is calibrated. What did you do to ensure calibration? I tried both methods (see my posts above) and am not confident with my results. I also am a newbie trying to get two subs integrated. Good luck!
The Guide mentions the two methods. One is to insert a sensitivity parameter in line 1 of the calibration file. The other method is a manual calibration using an external SPL meter.
AustinJerry's Avatar AustinJerry 07:04 AM 08-14-2014
Quote:
Originally Posted by Saril View Post
You may be right - all I can go by is the published specs. It seems strange that if my iPhone measured below 40 in the SUV then so should a dedicated SPL in the $100 range. Are noise floor values reported by the UMIK-1 reliable below 50dB C weighting? IIRC the USB interface imposes a limit on the lower range. Thanks for any feedback.
My UMIK-1 generally reports a noise floor of approximately 50dB. I am not sure why you are so concerned with noise floor readings anyway. When using REW to measure the audio performance of our systems, we normally are concerned with the shape of the curves, and comparing one curve to another. The absolute dB level of the measurement is rarely important. I would assume that your calibration is "good enough" and move on to actually taking some measurements.
Zee-man's Avatar Zee-man 08:50 AM 08-14-2014
AustinJerry, Alan P, and Saril - thanks for the feedback!

I calibrated my Umik by downloading the file from the mini dsp site (based off the serial number of the umik). I read the Umik was supposed to sit horizontal which was fine for testing LF. AustinJerry suggested a 90 degree calib file, where do I get that? Wouldn't it be a generic file?

I simply can't place the subs in the best locations due to WAF issues - I only have two options. I started the post (link below) which shows info about the room in case anyone wants to see it. My wife's preferred location is putting them in the built in cabinets directly behind the mains. The other option is to custom build end table enclosures and put them in the same position as the current end tables (that have the lamps on top). I've had the subs in both of these locations, and one other location, and the end table locations have been my favorite. My wife seems to think they sound best inside the cabinets....LOL. I just want some data to support what my ears are telling me. Help Needed - dual subs and preferred locations

AustinJerry - you mentioned setting the gain on the subs so they are reading 85-90. What am I playing to test this - pink noise in REW, test tones on the AVR?

I also need to set the phase of the subs. Is that done by playing pink noise or test tones and looking for the highest db level when turning the phase knobs? Should I do this at 75db? Will that have a potential to damage the subs?

Alan P - I tried for hours to get the HDMI connection to work, but my computer would not recognize it as a playback device. After a few hours, I gave up and bought an RCA cable. From AustinJerry's REW pdf file, I understand what to do if I want to test other speakers.

I didn't mention this earlier, but I have a mini dsp 2x4 and will add that into the mix after getting the sub positions nailed down. I assume this is the best way to go (yes - no?) and it will allow me to learn REW first and then dive into the mini dsp process. This stuff is confusing as hell for this mechanical guy and I believe learning one then the other is much better than diving into both at once.

Thanks again, this has been a huge help!
AustinJerry's Avatar AustinJerry 09:36 AM 08-14-2014
Quote:
Originally Posted by Zee-man View Post
AustinJerry, Alan P, and Saril - thanks for the feedback!

I calibrated my Umik by downloading the file from the mini dsp site (based off the serial number of the umik). I read the Umik was supposed to sit horizontal which was fine for testing LF. AustinJerry suggested a 90 degree calib file, where do I get that? Wouldn't it be a generic file?

I simply can't place the subs in the best locations due to WAF issues - I only have two options. I started the post (link below) which shows info about the room in case anyone wants to see it. My wife's preferred location is putting them in the built in cabinets directly behind the mains. The other option is to custom build end table enclosures and put them in the same position as the current end tables (that have the lamps on top). I've had the subs in both of these locations, and one other location, and the end table locations have been my favorite. My wife seems to think they sound best inside the cabinets....LOL. I just want some data to support what my ears are telling me. Help Needed - dual subs and preferred locations

AustinJerry - you mentioned setting the gain on the subs so they are reading 85-90. What am I playing to test this - pink noise in REW, test tones on the AVR?

I also need to set the phase of the subs. Is that done by playing pink noise or test tones and looking for the highest db level when turning the phase knobs? Should I do this at 75db? Will that have a potential to damage the subs?

Alan P - I tried for hours to get the HDMI connection to work, but my computer would not recognize it as a playback device. After a few hours, I gave up and bought an RCA cable. From AustinJerry's REW pdf file, I understand what to do if I want to test other speakers.

I didn't mention this earlier, but I have a mini dsp 2x4 and will add that into the mix after getting the sub positions nailed down. I assume this is the best way to go (yes - no?) and it will allow me to learn REW first and then dive into the mini dsp process. This stuff is confusing as hell for this mechanical guy and I believe learning one then the other is much better than diving into both at once.

Thanks again, this has been a huge help!
The 90-degree calibration file refers to the custom calibration files you would have received if you had purchased the mic from Cross Spectrum Labs. If you purchased elsewhere, then you would not have that file, so using the calibration file you downloaded from the MiniDSP site is fine. The difference is not that great. And the mic should ALWAYS be pointed at the ceiling for the types of measurements we are discussing here.

Too bad your placement options are limited. I guarantee that if you only have two choices, that neither one will be optimal. Place the subs in both locations and pick the lesser of the two evils, based on the REW measurements..

Normally, the sub phase should be set to zero, or if you have a polarity switch, set it to zero as well. You can gain-match the subs by following the link to the procedure that I provided. Did you review that procedure? It is quite detailed.

If HDMI doesn't work, the Guide has instructions for using an RCA cable with a Y-cable at the end. This should not impact your ability to get useful REW measurements, it's just a bit more tedious.

Using a MiniDSP 2x4 is fine (I have experimented with one myself). There are some good discussions here on AVS pertaining to the best ways to implement a MiniDSP. The normal approach would be:

1. Pick the best spot for the subs, based on REW measurements.
2. Use the REW measurements to generate automated filters for the MiniDSP.
3. Load the filters into the MiniDSP and re-run the REW measurements to assess the improvement.
4. Run the Audyssey calibration.
5. Re-run the REW measurements to assess the improvement (DEQ and Dynamic volume off).
6. Measure the output level of the combined subs, compare with the level of the main speakers, and adjust the trim of the combined sub channel upwards or downwards according to your preference. (Always adjust sub trims in the AVR, never adjust the gain on the back of the subs--this would alter the gain-matching!)
7. Sit back and listen--how do they sound?
8. Report progress in this thread.
Alan P's Avatar Alan P 10:12 AM 08-14-2014
Again Jerry nailed it.

You should be aware that the MiniDSP can add significant delay to your signal going to your subs. I would put it in the chain right away so that all your hard work isn't messed up by adding the DSP later on. Just make sure that both channels on the MiniDSP are set to 0 gain, no EQ filters, no added delay and the crossovers are bypassed. It is then basically just a splitter (that adds a bit of delay).
Tags: Dayton , Dayton Audio , Room Equilizer Wizard Rew
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