or Connect
AVS › AVS Forum › Audio › Audio theory, Setup and Chat › Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs
New Posts  All Forums:Forum Nav:

Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How... - Page 136

post #4051 of 9577
Quote:
Originally Posted by AustinJerry View Post


Looking at the frequency response graphs you posted several days ago, there is a serious issue in what looks like the 55-65Hz range. This issue exists on all three rows.

Based on the Harman approach, you should place subs in the nulls associated with the peaks you are seeing. Unfortunately, the mode calculator shows a 61Hz mode associated with the room length. The advice would be to place subs at the 1/4 and/or 3/4 points along the side wall. However, you say that this placement is not acceptable.

There is a 58Hz mode associated with the room's height. By placing one or more subs at the mid-point of the rear wall's height might alleviate this null. If there is a way to elevate the subs temporarily and take some measurements, that would be something you might consider.

Will you have a chance to post the Decay graphs?

Jerry,
I moved the two rear Velodynes from the two outer seats in the back row to the two inner seats in the centre of the room. After running XT32 I realised the sound was much smoother, and pleasing to the ear, it just seemed more refined. The move also produced approx. +2dbs when setting up for +75db sub setup.

I will do another REW and lets see if the 50/60Hz range has been improved, I believe so.

Gear mentioned in this thread:

post #4052 of 9577
Very interesting, Murray. Looking forward to the new measurements.
post #4053 of 9577
Quote:
Originally Posted by wse View Post

There are no ASIO files
 for the mac?

Not that I am aware of, unfortunately. My understanding is that Mac users run the laptop in a special mode (Bootcamp?). Not being a Mac person, I can't provide any guidance. Is your Mac an Intel-based system?
post #4054 of 9577
Quote:
Originally Posted by AustinJerry View Post

It is hard to say what is going on with your ASIO. In my experience, it can take a bit of effort to get ASIO to recognize everything. By effort, I mean stopping and re-starting REW, rebooting the laptop, and toggling back and forth between ASIO and Java. If you still have no success, REW is normally completely functional using the Java drivers. The only thing you can't do is select the surround speakers for measurements, and who needs to do that?
That is the part I didn't know. I didn't know if by using java + hdmi out to my reciever, that I would be getting false/incorrect readings. Are you saying this isn't so and that it is ok for me to just use java with my USB mic and hdmi out cable if all I'm going to measure is LC and Sub?

Could my problem with asio be with my hardware, and by that I mean that I'm running this whole thing off a windows bootcamped Mac mini?
post #4055 of 9577
Quote:
Originally Posted by wse View Post

Ok, here we go anyone lives in Southern California who could teach me REW! I would love to learn from a master, then that teacher could experience a 7.2 movie with (3) B&W 800D2, (4) 802D1, (2)JLAudio Fathom F113, and a 10 feet wide 2:35 Stewart Film Screen with a JVC RS-35U

If interested please PM me smile.gif
I'm no master but I'd love to listen to your setup biggrin.gif
post #4056 of 9577
Quote:
Originally Posted by DotJun View Post

That is the part I didn't know. I didn't know if by using java + hdmi out to my reciever, that I would be getting false/incorrect readings. Are you saying this isn't so and that it is ok for me to just use java with my USB mic and hdmi out cable if all I'm going to measure is LC and Sub?

Could my problem with asio be with my hardware, and by that I mean that I'm running this whole thing off a windows bootcamped Mac mini?

Sorry, I have no experience with Mac's running Boot Camp. However, I can say that a Windows PC works OK when using the Java drivers. It is documented in the guide. My recommendation would be to follow the guide since my understanding is that a Mac running Boot Camp on an Intel CPU is functionally equivalent to a Windows PC.
post #4057 of 9577
Quote:
Originally Posted by AustinJerry View Post

Sorry, I have no experience with Mac's running Boot Camp. However, I can say that a Windows PC works OK when using the Java drivers. It is documented in the guide. My recommendation would be to follow the guide since my understanding is that a Mac running Boot Camp on an Intel CPU is functionally equivalent to a Windows PC.
I followed the guide, which is insanely easy to understand btw, until I hit the problem of not being able to get my mic active on the asio control panel but if you say that the java drivers are good then I might have no choice. Just to clarify one more time though, it's ok for me to use java with USB mic AND hdmi out?
post #4058 of 9577
Quote:
Originally Posted by AustinJerry View Post

Not that I am aware of, unfortunately. My understanding is that Mac users run the laptop in a special mode (Bootcamp?). Not being a Mac person, I can't provide any guidance. Is your Mac an Intel-based system?

Yes, my mac os an intel- based processor, and yes I use boot camp and windows 7
post #4059 of 9577
Jerry,

Since I have the four subs up front in pairs at 96Hz positions of the graph, would it be better if I keep one each in the same position and move two to the centre of the room to help with 48Hz?


The two rear subs I mentioned I moved to the centre in the back row sit approx 2 feet higher from the lower floor due to the risers. You mentioned 5' up looked the best place, but probably since Im 2' up from the floor level, maybe this is why the bass is much better in the back row, its very reduced. I will have a new REW reading for you tomorrow.
post #4060 of 9577
Murray,

First you should say goodbye to the notion that you'll get optimum bass response in every seat. Concentrate on optimizing one seat.

The process is to measure, move subs, measure, move subs, measure, ...you get the point. Measure multiple points within the listening area. I would do at least 3 (center and 6" to the left and the right). Then choose the configuration that a) has the lowest difference between the measured points and b) doesn't show wide and deep dips. Don't be concerned about peaks, they can be removed with EQ in the last step of the optimization process.

If your goal is to get smooth bass response across the whole room a different approach is necessary, e.g. http://www.avsforum.com/t/837744/double-bass-array-dba-the-modern-bass-concept
Some interesting additional information from Todd Welti (Harman): http://www.whatsbestforum.com/showthread.php?3320-Comparison-of-Double-Bass-Array-to-Sound-Field-Management-Overview
post #4061 of 9577
Quote:
Originally Posted by RapalloAV View Post

Jerry,

Since I have the four subs up front in pairs at 96Hz positions of the graph, would it be better if I keep one each in the same position and move two to the centre of the room to help with 48Hz?


The two rear subs I mentioned I moved to the centre in the back row sit approx 2 feet higher from the lower floor due to the risers. You mentioned 5' up looked the best place, but probably since Im 2' up from the floor level, maybe this is why the bass is much better in the back row, its very reduced. I will have a new REW reading for you tomorrow.

There are never any guarantees. Move and measure, pick the best result. Same goes with the sub elevation. In a multi-tiered room, the results could be different than in a conventional room.
post #4062 of 9577

Well, I'm back to chasing several pesky room reflections today, after taking a couple of weeks off.  Trust me, there is such a thing as REW-burnout, and it's not pleasant.

 

Anyway, I have made significant progress after the short vacation.  Here is what I was observing at the start:

 

 

I have three significant reflections above -20dB.  I know that the first one is caused by ceiling fan blade reflections.  However, if I turn the fan on, the measurement changes:

 

 

The fan blade reflection is reduced significantly.  I don't know how this translates into audio reality, because I'm sure there are still reflections, and that REW just isn't capturing them because of timing anomalies with the blades rotating.  Regardless, the fan is here to stay, and in the current hot summer, the blades are always rotating when I am in the listening room.

 

On to the last remaining reflection, shown above at 11.3ms.  Time to use the Blocking Method again!  First, block left:

 

 

No joy--the reflection is still there.  Same joyless result with block right and block behind.  However, block above (ceiling reflections) yielded this:

 

 

The reflection is gone!  After taking a few minutes to calm my excitement, I thought, how can this be?  I just installed two GIK 244 panels on the ceiling at the first reflection points with very good results.  Where on the ceiling could these reflections be coming from?  After all, the rule of "angle of incidence=angle of reflection" suggests that the first point of reflection is the only logical place the reflections could be originating from.

 

Wait a minute!  I recall advice given to me last year by our friend and thread participant, Markus.  He advised me to be aware of multiple-point reflections, and that he suspected a reflection bouncing off the ceiling, onto the back wall, and then down into the MLP.  But I treated my back wall--could this really be possible?  Here is the back wall:

 

 

Three 24x48 GIK 242 panels would seem to be enough to block any back wall reflections..However, there is the smallest sliver of open drywall at the very top of the picture.  Could this be the source?  Let's try a temporary treatment:

 

 

Note that I had to slide the 24x24 temporary panel way to the right (it's the maroon panel hanging half off the top GIK panel).  Here is the result:

 

 

 

The reflection is completely OK now!  Not only that, almost all reflections are down to very close to the -20dB level, which is my objective.

 

This exercise has shown me several things.  First, the importance of never giving up.  Second, the effectiveness of the blocking method.  And third, always listen to the advice of the experts (thanks again, Markus).

 

It's Miller Time!!!   biggrin.gif

 

 

Edit:  Keith, do you have an equivalent phrase to "It's Miller Time" over there?

post #4063 of 9577
Quote:
Originally Posted by AustinJerry View Post

There are never any guarantees. Move and measure, pick the best result. Same goes with the sub elevation. In a multi-tiered room, the results could be different than in a conventional room.

When you move subs, do you have to do XT32 each time before you measure again with REW?
post #4064 of 9577
Well done Jerry!

I think a substantial part of your remaining reflections in the 1-2.5ms range is floor reflections. A thick natural fiber rug should help a lot there.
post #4065 of 9577
Quote:
Originally Posted by AustinJerry View Post

 

It's Miller Time!!!   biggrin.gif

 

 

Edit:  Keith, do you have an equivalent phrase to "It's Miller Time" over there?

 

Good job, Jerry. Persistence is often the key to success.

 

We don't really, although my friends will often look at the clock after a busy day and exclaim, "Ah, it's beer 'o'clock!"

post #4066 of 9577
Quote:
Originally Posted by RapalloAV View Post

When you move subs, do you have to do XT32 each time before you measure again with REW?

I usually measure new locations with Audyssey off. Once you find the best position without Audyssey, then run the calibration. This saves a lot of time. Calibration rarely makes things worse.
post #4067 of 9577
T
Quote:
Originally Posted by jim19611961 View Post

Well done Jerry!

I think a substantial part of your remaining reflections in the 1-2.5ms range is floor reflections. A thick natural fiber rug should help a lot there.

Thanks, Jim. I actually have thick wall-to-wall carpeting. My subs are very close behind the mains. Could that be the source?
post #4068 of 9577
Quote:
Originally Posted by AustinJerry View Post

T
Thanks, Jim. I actually have thick wall-to-wall carpeting. My subs are very close behind the mains. Could that be the source?

I am sure your wall to wall carpet is synthetic, not excessively thick and not natural fiber. It makes a difference.

If you do some ETC slicing, you should be able to determine the frequency range and thus deduce if the subs are responsible or not.
Edited by jim19611961 - 7/15/13 at 12:39pm
post #4069 of 9577
Quote:
Originally Posted by jim19611961 View Post

So, not a USB problem per say, but a mic quality issue then?
That's right. You can get superb fidelity out of USB. You just need to be careful to isolate the digital side/noise from the very low level mic signal.
Quote:
The USB mic I use I dont consider a pricy one. So much difference?
I am not sure they even bothered to measure the performance of these units. With some careful engineering (simple things like separating sections better) at the same cost one could do better. So it is not surprising that you have a different one without this problem.
post #4070 of 9577
Starting my journey "Down the Rabbit Hole"
So several years ago I tinkered with REW and had some limited success with external mixers, etc...

However; since then and with a SPECIAL thanks to everyone here who has provided an excellent guide >> I am revisiting REW (this time with a UMIK USB mic).
I believe the proper way to start his journey is to provide some background:

-My HT is an open floor plan (open to the left, with an open doorway to the rear), space is about 16' wide by 19' deep.
-Seating and MLP is 10.5' back from my LR mains and about 12' back from my center channel.

-Mains and center are DIY sound group sealed SEOS12's.

-Subs are 3 SVS 16 Hz cylinders arranged as follows:
-The front two are16-46s; one is visible in the front left corner, and the other is roughly equidistant hidden behind the curtain to the right of the right main channel speaker
-3rd one is an SVS20-39 with a matching 12.3 driver tuned to 16Hz centered on the back wall.

The following should help explain:



I recently acquired a 4311, the front two cylinders are on sub channel1, and the rear is on sub channel 2

Room treatments include floor-ceiling super-chunk traps in the front corners, and bass trapping in the overhead soffit above the screen
Also have a sealed panel absorber (as per Ethan Winner's website) on the back wall.

My first Audyssey run was done after dragging the subs individually to the center of the room for some matching measurements.
Next up is to run REW, capture some graphs, and experiment with settings (Ie.crossover level & subwoofer distance) related to the crossover splice
post #4071 of 9577
Nice setup, Cousin Ed! We are looking forward to your measurements. Thanks for the write-up.
post #4072 of 9577
Will just struck out after 2hrs trying to use a WINXP laptop. Kept getting soundcard error messages and REW input "too low" messages. I'll post error photos tomorrow.
post #4073 of 9577
Yes, let's have a look at the error messages. You were following the guide closely, correct?

No offense, but it amazes me that XP laptops are still around and running. It makes it hard to separate hardware and OS issues from REW issues.
post #4074 of 9577
Jerry - have you, or anyone, used a Redmere cable? USB 3.0?
post #4075 of 9577
Sorry, never used one.
post #4076 of 9577
Quote:
Originally Posted by pdxrealtor View Post

Jerry - have you, or anyone, used a Redmere cable? USB 3.0?

I have Redmere USB cables in my setup including between my laptop to my prepro. But an Amazon USB extension between the umm-6 and the laptop.
post #4077 of 9577
Apologies if this has been discussed already, but are the UMIK units fixed now? I believe there was an issue with mic consistency and accuracy with measurements. Is it the preferred USB mic to use with REW right NOW or is the Dayton UMM-6 a better unit at the moment? I don't know which one to go for.

I live in a flat and my only worry is that my SPL levels need to be obscenely high for measurements to be taken cleanly given the noise floor issues with these USB mics. Are my worries unfounded? Again, apologies for bringing this up here, but you guys use these mics all the time and I'm not sure if there has been any recent developments since I last perused the thread. Your experience and advice would be most appreciated . Thanks and sorry for the hijack.
post #4078 of 9577

I have both the UMIK-1 and the UMM-6.  Both are available from Cross Spectrum Labs with custom calibration files.  The lack of the calibration files was the original issue with the UMIK-1, which has now been removed.  As far as I know, the initial quality issues with the UMIK-1 have been addressed.  I find no functional difference between the two mics, and feel that either is a good choice to use with REW.

 

As far as the sensitivity of these inexpensive USB mics, both yield a noise floor measurement of approximately 50dB, compared with an EMM-6 calibrated mic, which measures a noise floor of approximately 40dB.  I live in a detached home in a quiet neighborhood, so these measurements are in a very quiet environment.  I usually calibrate to 85-90dB for my measurements, which I would not characterize as obscenely high, although if I lived in an apartment, my neighbors might not be very happy.
 

post #4079 of 9577

Jerry:  Is your UMM-6 mic still functional?  As one of the few (if not only?) members with both mics, I was curious if you've tried a side by side measurement to compare any differences between the two?  IIRC, you got the UMIK-1 because your UMM-6 finally gave out so even a comparison from your extremely precise mic placements from different measurement sessions might be interesting (assuming you've also documented the precise location of all your treatments given the recent experimentation!).

post #4080 of 9577
Quote:
Originally Posted by AustinJerry 
I live in a detached home in a quiet neighborhood, so these measurements are in a very quiet environment. I usually calibrate to 85-90dB for my measurements, which I would not characterize as obscenely high, although if I lived in an apartment, my neighbors might not be very happy.

How long does the measurement process take? 2-3 seconds or more and if the noise floor of these USB mics are 50 dB, would 70-75 dB be sufficiently high volume or must the SPL level be over 80? Yes, I don't want to irritate the neighbors if I don't have to.
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: Audio theory, Setup and Chat

Gear mentioned in this thread:

AVS › AVS Forum › Audio › Audio theory, Setup and Chat › Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs