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Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How... - Page 24

post #691 of 9570

^ I don't have an issue with your suggestion and will work on revising the guide to provide better guidance for both HDMI and non-HDMI users.

Gear mentioned in this thread:

post #692 of 9570
Quote:
Originally Posted by AustinJerry View Post

^ I don't have an issue with your suggestion and will work on revising the guide to provide better guidance for both HDMI and non-HDMI users.

+1. Oh yeah! smile.gifsmile.gifsmile.gif
post #693 of 9570
Jkasanic, it looks like you have some serious room nulls at 40 Hz (-10dB) and between 60 - 80 HZ (-20dB!).That is part of the good chest thumping zone. I would try repositioning your sub. It may only have to be moved a foot or two. I did make the assumption that you have a single sub. A second could help smooth out you room response. I use a SMS-1 to help with my in room response and it helps immensely.
post #694 of 9570

 

Quote:
Originally Posted by jkasanic View Post


I certainly would appreciate any feedback on my mdat files! Thanks again for all of your support!

 

I have reviewed the measurements, and have some observations.

 

The measurements taken with Audyssey off seem to have an output level that is approximately 15dB low, i.e. the measurements are centered around 60-65dB, not at 75dB where they should be.  This could be because the mic was not properly calibrated.  Not to worry--for the purpose of my evaluation, I simply added a 15dB offset to the measurements without Audyssey. 

 

Focusing on the low frequency range below 200Hz, all graphs with no smoothing.

 

Here is the first comparison, left channel without Audyssey (blue) and with Audyssey (red). I see issues at 40Hz, ~70Hz, and ~110Hz.  Audyssey does a nice job below 40Hz, has made a minor adjustment to the dip at 40Hz, and has done some correction at 110Hz.  70Hz is still an issue.

 

 

Here is the second comparison, right channel, same colors.  Same issue at 40Hz, with some correction by Audyssey.  There is a huge issue at 70Hz.  The response above 80Hz looks reasonably good.

 

 

Here is the center channel, same colors.  There is that darn 40Hz dip again!  Audyssey did a nice job on the 70Hz dip.  Audyssey introduced something bad at 105Hz.

 

 

Finally, subs only, same colors.  Same story--issue at 40Hz and at 70Hz.

 

 

General conclusions:  I see correctable issues in the bass region.  Audyssey is making it better, so I suspect your system sounds better with Audyssey on, correct?  In the upper frequencies, everything looks quite normal, with Audyssey actually boosting the high frequencies somewhat, perhaps compensating either for your speakers' HF response, or compensating for a slightly dead room.

 

Other comments:

 

We are missing a key measurement--left+right+sub.  It is important to see how the left and right speakers interact with each other, although I don't think they will address the 40Hz issue.

 

What are your room dimensions?  We need to see if 40Hz is caused by a room mode.  Is one of your dimensions 14ft? 28ft?

 

What is the crossover between the sub and the mains?  Between sub and center?  The issues around 70Hz could be a phase issue with the splice between the sub and the mains, especially if you are running an 80Hz crossover.  We can address these issues by the so-called "sub distance tweak", whic involves adjusting the subs distance in small increments, re-measuring to see if the 70Hz issue changes, and continuing until the smoothest response is achieved.

 

Finally, you have only one sub?  The easy advice is to purchase a second, identical sub, and then experiment with different placements.  At a minimum, you should move the one sub around to see if the 40Hz issue changes (it may not if it is a room mode).

 

Here is what we would like to see for your room (multiple subs, no smoothing, Audyssey on).  We'll get there!

 

post #695 of 9570
Quote:
Originally Posted by AustinJerry View Post

^ I don't have an issue with your suggestion and will work on revising the guide to provide better guidance for both HDMI and non-HDMI users.

 

I am re-considering this offer.  After reviewing the Guide, having different instructions for non-HDMI users would require a significant re-write, and will add 50% to the length of the document, not to mention adding complexity and confusion.  For example, all the screen shots in the Windows audio configuration section show the HDMI connection as the preferred connection.  If not using HDMI, the "Speakers: High Definition Audio Device" becomes the default, so all new screen shots would be needed.

 

This is going to be more confusing than it is worth, in my opinion.   I think the original objective of having a guide specifically for using REW with USB mics and HDMI connections will result in a cleaner, simpler guide.  Other thoughts?

post #696 of 9570
Quote:
Originally Posted by AustinJerry View Post

Quote:
Originally Posted by AustinJerry View Post

^ I don't have an issue with your suggestion and will work on revising the guide to provide better guidance for both HDMI and non-HDMI users.

 

I am re-considering this offer.  After reviewing the Guide, having different instructions for non-HDMI users would require a significant re-write, and will add 50% to the length of the document, not to mention adding complexity and confusion.  For example, all the screen shots in the Windows audio configuration section show the HDMI connection as the preferred connection.  If not using HDMI, the "Speakers: High Definition Audio Device" becomes the default, so all new screen shots would be needed.

 

This is going to be more confusing than it is worth, in my opinion.   I think the original objective of having a guide specifically for using REW with USB mics and HDMI connections will result in a cleaner, simpler guide.  Other thoughts?

 

FWIW, I agree. The thread title specifically refers to HDMI connection, so anything else is OT anyway.

 

If the thread title was amended to refer just to USB mics, then there would be a very strong case for including RCA connections.  

 

If you were going to address it in the guide, I would make it a separate Addendum, keeping it well away from the HDMI section. There is considerable potential for confusion when restricting the guide to just HDMI (as we have seen so far) - to try to cover HDMI and RCA at the same time would increase that potential exponentially IMO.

post #697 of 9570
So let me get this straight, if I purchase the Dayton UMM-6 from CSL, it is just plug and play with the 3.5mm headphone jack in my laptop? Why would I need an external sound card for the Behringer ECM-8000 and Xenyx502 but not with the UMM-6? Speaking of which, I will probably purchase an external sound card anyway, if I can find a cheap one that has HDMI, as that is how I want to do my measurements.
post #698 of 9570
Quote:
Originally Posted by Martycool007 View Post

So let me get this straight, if I purchase the Dayton UMM-6 from CSL, it is just plug and play with the 3.5mm headphone jack in my laptop? Why would I need an external sound card for the Behringer ECM-8000 and Xenyx502 but not with the UMM-6? Speaking of which, I will probably purchase an external sound card anyway, if I can find a cheap one that has HDMI, as that is how I want to do my measurements.

 

REW requires a full-duplex audio system to run, i.e. the audio system must be able to support simultaneous output (generating test tones) and input (measuring the test tone results using a microphone).  The typical laptop internal soundcard does not support duplex operation, which is why "legacy" REW kits required an external soundcard.  The new USB mics do not use the same internal audio circuitry that a microphone plugged into the 3.5mm jack uses, so full duplex is no longer a requirement.  Simply use the USB mic for the input side, and the headphone mini-jack for the output (or the HDMI cable, for those laptops that support HDMI).

 

For the same reason, if you were to use the ECM8000 connected to the Xenyx mixer, the mixer needs to plug into the input side of the audio system.  Since the laptop doesn't support full-duplex, the external soundcard is required.

 

There is nothing wrong with purchasing an external soundcard, if your laptop doesn't support HDMI, and you want to use an HDMI connection.  The external soundcard would only be used for the output side, and the USB mic would still be plugged into the laptop.

post #699 of 9570
Quote:
Originally Posted by kbarnes701 View Post

 

FWIW, I agree. The thread title specifically refers to HDMI connection, so anything else is OT anyway.

 

If the thread title was amended to refer just to USB mics, then there would be a very strong case for including RCA connections.  

 

If you were going to address it in the guide, I would make it a separate Addendum, keeping it well away from the HDMI section. There is considerable potential for confusion when restricting the guide to just HDMI (as we have seen so far) - to try to cover HDMI and RCA at the same time would increase that potential exponentially IMO.

 

Good input.  Let me go back to the drawingboard.

post #700 of 9570
Quote:
Originally Posted by Martycool007 View Post

So let me get this straight, if I purchase the Dayton UMM-6 from CSL, it is just plug and play with the 3.5mm headphone jack in my laptop? 

The UMM-6 is a USB mic.

post #701 of 9570
Quote:
Originally Posted by AustinJerry View Post



Here is what we would like to see for your room (multiple subs, no smoothing, Audyssey on).  We'll get there!



If only.smile.gif Not in my room. Short of stacking subs from floor to ceiling, (I've thought about it biggrin.gif)I will never not have a dip (null) at about 90hz from the ceiling bounce. And I have 4 identical subs placed to optimize the room response. We may want to think about using a sample that is this ruler flat as I would suggest that this graph might set unrealistic expectations. It might work in a few rooms, but not all, regardless of the number of subs.
post #702 of 9570
Quote:
Originally Posted by audioguy View Post

Quote:
Originally Posted by AustinJerry View Post



Here is what we would like to see for your room (multiple subs, no smoothing, Audyssey on).  We'll get there!


If only.smile.gif Not in my room. Short of stacking subs from floor to ceiling, (I've thought about it biggrin.gif)I will never not have a dip (null) at about 90hz from the ceiling bounce. And I have 4 identical subs placed to optimize the room response. We may want to think about using a sample that is this ruler flat as I would suggest that this graph might set unrealistic expectations. It might work in a few rooms, but not all, regardless of the number of subs.

 

While a ruler flat response is nice to aim for, it isn't really necessary. What matters is what can actually be heard and AIUI there is much evidence to suggest that 'flat' to +/- 3dB will give you more or less the same audible experience as perfectly flat.

 

Here's mine for example - it doesn't look nearly as good as Jerry's, but it probably sounds very similar in real life. I think we can obsess too much ;)

 

 

post #703 of 9570
Quote:
Originally Posted by AustinJerry View Post

Quote:
Originally Posted by kbarnes701 View Post

 

FWIW, I agree. The thread title specifically refers to HDMI connection, so anything else is OT anyway.

 

If the thread title was amended to refer just to USB mics, then there would be a very strong case for including RCA connections.  

 

If you were going to address it in the guide, I would make it a separate Addendum, keeping it well away from the HDMI section. There is considerable potential for confusion when restricting the guide to just HDMI (as we have seen so far) - to try to cover HDMI and RCA at the same time would increase that potential exponentially IMO.

 

Good input.  Let me go back to the drawingboard.

 

Jerry:  I'd be more than happy to assist with any screenshots required as well as a write-up for the steps involved with RCA connections.  Perhaps we should take this to PM so I understand your concerns more clearly?  As the guide is currently written, I feel only a minor change is required for those without an HDMI connection.  Perhaps I'm missing something though?

post #704 of 9570
Quote:
Originally Posted by jkasanic View Post

 

Jerry:  I'd be more than happy to assist with any screenshots required as well as a write-up for the steps involved with RCA connections.  Perhaps we should take this to PM so I understand your concerns more clearly?  As the guide is currently written, I feel only a minor change is required for those without an HDMI connection.  Perhaps I'm missing something though?

 

Thanks for the offer, let's get back to that a little later.  In the meantime, I am more interested in your answers to my questions.

post #705 of 9570
Quote:
Originally Posted by kbarnes701 View Post

 

While a ruler flat response is nice to aim for, it isn't really necessary. What matters is what can actually be heard and AIUI there is much evidence to suggest that 'flat' to +/- 3dB will give you more or less the same audible experience as perfectly flat.

 

Here's mine for example - it doesn't look nearly as good as Jerry's, but it probably sounds very similar in real life. I think we can obsess too much ;)

 

 

 

I certainly agree, Keith.  Neither of our response curves shows any significant peaks or dips in the low frequencies.  And, IIRC, you induce the slight emphasis in the ultra low end by changing the DSP setting on those wonderful Submersives.  It's a wonder that the mortar in your walls hasn't cracked by now!  tongue.gif

post #706 of 9570
Quote:
Originally Posted by AustinJerry View Post

Quote:
Originally Posted by kbarnes701 View Post

 

While a ruler flat response is nice to aim for, it isn't really necessary. What matters is what can actually be heard and AIUI there is much evidence to suggest that 'flat' to +/- 3dB will give you more or less the same audible experience as perfectly flat.

 

Here's mine for example - it doesn't look nearly as good as Jerry's, but it probably sounds very similar in real life. I think we can obsess too much ;)

 

 

 

I certainly agree, Keith.  Neither of our response curves shows any significant peaks or dips in the low frequencies.  And, IIRC, you induce the slight emphasis in the ultra low end by changing the DSP setting on those wonderful Submersives.  It's a wonder that the mortar in your walls hasn't cracked by now!  tongue.gif

 

LOL. I would really love to have a curve like yours though, Jerry... just because. Probably no audible difference but for us obsessives when has that ever been an issue :)  Once I get going with REW maybe I can tweak and improve...

 

Yes, that emphasis at the bottom end  is a result of using Pgm 2 on the SubMs - if I switched it to Pgm 1 it would flatten that curve more. Walls are holding up good (so far) :)

post #707 of 9570
Quote:
Originally Posted by kbarnes701 View Post

Quote:
Originally Posted by audioguy View Post

Quote:
Originally Posted by AustinJerry View Post



Here is what we would like to see for your room (multiple subs, no smoothing, Audyssey on).  We'll get there!


If only.smile.gif Not in my room. Short of stacking subs from floor to ceiling, (I've thought about it biggrin.gif)I will never not have a dip (null) at about 90hz from the ceiling bounce. And I have 4 identical subs placed to optimize the room response. We may want to think about using a sample that is this ruler flat as I would suggest that this graph might set unrealistic expectations. It might work in a few rooms, but not all, regardless of the number of subs.

 

While a ruler flat response is nice to aim for, it isn't really necessary. What matters is what can actually be heard and AIUI there is much evidence to suggest that 'flat' to +/- 3dB will give you more or less the same audible experience as perfectly flat.

 

Here's mine for example - it doesn't look nearly as good as Jerry's, but it probably sounds very similar in real life. I think we can obsess too much ;)

 

 

 

Guys, thanks for the feedback thus far on my measurements and I look forward to improving my results (hell, I'd take Jerry's curve WITH some smoothing!).  I should have my UMM-6 mic later this week or early next week at the latest.  I will redo the measurements with my avr and mic calibrated in REW as well as perform another sub crawl.  In the meantime, you might recall that I did post some results of a crawl using OM in the Audyssey thread here.

 

The room dimensions are as follows:

 

18' 3" long on right side and 17' 1/4" on left x 14' 3" wide x 8' 8" high with two door size openings on the right side of the room for the stairway at bottom right and access to the unfinished portion near the top right).  LCR's are MKSound S150's, mids are Speakercraft AIM Wide Ones and rears are Speakercraft AIM8 Ones.  The subwoofer is an older Infinity SSW-212 300W dual 12" woofers that is right corner loaded behind the false wall.  I just added the LCR's and was planning to upgrade the surrounds and subs as (time and money) permits.  As you can see from the pics below, this is not a dedicated theater space.  MLP is approx. 13' from the false wall.  Also, I can add surround speaker locations if anyone thinks that's relevant (guessing not at this point):

 

 

 

 

I know it's hard to tell because I only have a full range graph with the OM measurement but would you categorize my results as "consistent" between OM and REW based on these two graphs (full range, 1/24th smoothing applied) of sub only with no Audyssey (and offset added to REW graph to adjust output at 20Hz to be approx. 75 dB to match OM results since mic calibration was not performed during my REW measurements):

 

 

 

I think it's fairly consistent given the fact that 2 setups were involved but I was curious what others might think?  The OM mic is going back today so I'll be a dedicated REW user from this point forward.

post #708 of 9570
Quote:
Originally Posted by audioguy View Post

If only.smile.gif Not in my room. Short of stacking subs from floor to ceiling, (I've thought about it biggrin.gif)I will never not have a dip (null) at about 90hz from the ceiling bounce. And I have 4 identical subs placed to optimize the room response. We may want to think about using a sample that is this ruler flat as I would suggest that this graph might set unrealistic expectations. It might work in a few rooms, but not all, regardless of the number of subs.

I've read that raising a subwoofer up off the floor can address the floor ceiling mode. Apparently rooms are 3-dimensional under current understanding which is why Geddes approach is 3 subs.
post #709 of 9570
Quote:
Originally Posted by kbarnes701 View Post

While a ruler flat response is nice to aim for, it isn't really necessary. What matters is what can actually be heard and AIUI there is much evidence to suggest that 'flat' to +/- 3dB will give you more or less the same audible experience as perfectly flat.

Here's mine for example - it doesn't look nearly as good as Jerry's, but it probably sounds very similar in real life. I think we can obsess too much wink.gif




Is that 1/12th smoothing, Keith? Pretty darned good if we 'settled' for this in the 15 to 200 Hz range (or should I say 5 Hz with your Submersives LOL)
Edited by sdrucker - 1/28/13 at 10:04am
post #710 of 9570
Quote:
Originally Posted by dstew100 View Post

Quote:
Originally Posted by audioguy View Post

If only.smile.gif Not in my room. Short of stacking subs from floor to ceiling, (I've thought about it biggrin.gif)I will never not have a dip (null) at about 90hz from the ceiling bounce. And I have 4 identical subs placed to optimize the room response. We may want to think about using a sample that is this ruler flat as I would suggest that this graph might set unrealistic expectations. It might work in a few rooms, but not all, regardless of the number of subs.

I've read that raising a subwoofer up off the floor can address the floor ceiling mode. Apparently rooms are 3-dimensional under current understanding which is why Geddes approach is 3 subs.

 

I read this somewhere too but I don't recall any method for determining just how high it should be?  Is there a general rule based on the distance from floor to ceiling?  I suppose measuring is the only surefire way to know.

post #711 of 9570
Quote:
Originally Posted by RickD1225 View Post

Jkasanic, it looks like you have some serious room nulls at 40 Hz (-10dB) and between 60 - 80 HZ (-20dB!).That is part of the good chest thumping zone. I would try repositioning your sub. It may only have to be moved a foot or two. I did make the assumption that you have a single sub. A second could help smooth out you room response. I use a SMS-1 to help with my in room response and it helps immensely.

 

Thanks for the suggestions!  You are correct in that I currently have only one sub.  Additional info was posted a few posts above.  I've been looking at dual Submersives as well as the new Ken Kreisel offering (dual DXD-12012's) but I think my upgraditis is going to have to wait at least another year.  I just redid my basement and upgraded the 60" plasma to a 126" front projector plus added a false wall as well as an AV rack to house all of my gear in the unfinished portion of my basment.

post #712 of 9570
Quote:
Originally Posted by AustinJerry View Post

 

General conclusions:  I see correctable issues in the bass region.  Audyssey is making it better, so I suspect your system sounds better with Audyssey on, correct?  Correct

 

Other comments:

 

We are missing a key measurement--left+right+sub.  It is important to see how the left and right speakers interact with each other, although I don't think they will address the 40Hz issue.

I will measure this once my UMM-6 mic arrives.

 

What are your room dimensions?  We need to see if 40Hz is caused by a room mode.  Is one of your dimensions 14ft? 28ft?

18' 3" x 14' 4" x 8' 8" so yes, the width of the room is VERY close to 14'.

 

What is the crossover between the sub and the mains?  Between sub and center?

All crossovers are set at 90Hz.  Audyssey recommended 70Hz for the center and 90Hz for the L and R.  40Hz for the surrounds.  I bumped the center and surrounds to 90 Hz.

 

The issues around 70Hz could be a phase issue with the splice between the sub and the mains, especially if you are running an 80Hz crossover.  We can address these issues by the so-called "sub distance tweak", whic involves adjusting the subs distance in small increments, re-measuring to see if the 70Hz issue changes, and continuing until the smoothest response is achieved.

 

Finally, you have only one sub?  Correct

 

The easy advice is to purchase a second, identical sub, and then experiment with different placements.

My current sub is an older Infinity SSW-212.  It was a fairly capable sub back in the early '90's and there seems to be avid interest in it on E-bay as some are going for at or near their original MSRP.  I haven't done enough research to understand why though and would plan to buy 2 new subs once I'm ready to upgrade.

 

At a minimum, you should move the one sub around to see if the 40Hz issue changes (it may not if it is a room mode).

See what you think of my OM results posted previously.  I believe you already commented in the Audyssey thread about the optimal location but I suppose we should wait until I can redo the measurements with REW to draw any final conclusions.

 

 

Jerry, I saw your post on specific responses to your questions so even though some of this is repetitive from my previous post, I thought the least I could do is collect all of your questions and answers into one post!  Thanks again for your help!


Edited by jkasanic - 1/28/13 at 10:12am
post #713 of 9570
Quote:
Originally Posted by sdrucker View Post

Quote:
Originally Posted by kbarnes701 View Post

While a ruler flat response is nice to aim for, it isn't really necessary. What matters is what can actually be heard and AIUI there is much evidence to suggest that 'flat' to +/- 3dB will give you more or less the same audible experience as perfectly flat.

Here's mine for example - it doesn't look nearly as good as Jerry's, but it probably sounds very similar in real life. I think we can obsess too much wink.gif



Is that 1/12th smoothing, Keith? Pretty darned good if we 'settled' for this in the 15 to 200 Hz range (or should I say 5 Hz with your Submersives LOL)

I can't remember, Stuart. And unlike REW, OM doesn't automatically add the smoothing to the graph. I usually make my graphs with 1/24th smoothing but that looks way too smooth to be 1/24th. Sorry I can't be more specific and I don't want to run any more measurements now until I get my new mic and start using REW. It will be a big help when we are all suing consistent graph parameters I think.

post #714 of 9570
Quote:
Originally Posted by jkasanic View Post

 

Jerry, I saw your post on specific responses to your questions so even though some of this is repetitive from my previous post, I thought the least I could do is collect all of your questions and answers into one post!  Thanks again for your help!

 

Now that you mention it, I recall seeing your posts in the Audyssey thread.  Sorry, I monitor too many threads, but I should have remembered.  The advice you received from Roger Dressler is good advice, so I have nothing to add at this time.

 

I plugged in your dimensions in the Room Mode Calculator:

 

 

 

 

The primary resonant frequency associated with the width of the room is ~40Hz.  If your MLP is halfway between the left and right walls, this would place you directly in the null associated with 40Hz, which the measurements seem to support.  One way to address this would be to move the MLP to the right or left a bit and re-measure to see if there is an improvement.

 

The secondary resonant frequency associated with the width is 80Hz, and the secondary for the length is 62Hz, and the primary for the height is 65Hz.  I don't see anything associated with room modes that might be causing the issue at ~75Hz.  You should experiment with the sub/mains phase adjustments.

 

I think we should wait for Jason's opinion regarding whether bass treatments might be a solution for you.  For example, I have 96 sq ft of bass traps (eight 4x2 velocity traps, half from RealTraps, the other half from GIK).  Even though the treatments are not in a dedicated HT room, I am single and don't have WAF issues to deal with.

post #715 of 9570
Quote:
Originally Posted by AustinJerry View Post

I think we should wait for Jason's opinion regarding whether bass treatments might be a solution for you.  For example, I have 96 sq ft of bass traps (eight 4x2 velocity traps, half from RealTraps, the other half from GIK).  Even though the treatments are not in a dedicated HT room, I am single and don't have WAF issues to deal with.

 

Isn't 8 x 4 x 2, 64 sq ft, Jerry? Or am I missing something?  Is the 'missing' 32 sq feet the edges of the traps? I am not asking to be a pedantic clot, but because I would like to work out the sq footage of my own traps (GIK) in relation to the room size.

post #716 of 9570
Quote:
Originally Posted by kbarnes701 View Post

 

Isn't 8 x 4 x 2, 64 sq ft, Jerry? Or am I missing something?  Is the 'missing' 32 sq feet the edges of the traps? I am not asking to be a pedantic clot, but because I would like to work out the sq footage of my own traps (GIK) in relation to the room size.

 

You pedantic clot, of course it is 64 sq ft.  redface.gif   And I had a minor in math when I went to college....

post #717 of 9570
Quote:
Originally Posted by AustinJerry View Post

Quote:
Originally Posted by jkasanic View Post

 

Jerry, I saw your post on specific responses to your questions so even though some of this is repetitive from my previous post, I thought the least I could do is collect all of your questions and answers into one post!  Thanks again for your help!

 

Now that you mention it, I recall seeing your posts in the Audyssey thread.  Sorry, I monitor too many threads, but I should have remembered.  The advice you received from Roger Dressler is good advice, so I have nothing to add at this time.

 

I plugged in your dimensions in the Room Mode Calculator:

 

 

 

 

The primary resonant frequency associated with the width of the room is ~40Hz.  If your MLP is halfway between the left and right walls, this would place you directly in the null associated with 40Hz, which the measurements seem to support.  One way to address this would be to move the MLP to the right or left a bit and re-measure to see if there is an improvement.

 

The secondary resonant frequency associated with the width is 80Hz, and the secondary for the length is 62Hz, and the primary for the height is 65Hz.  I don't see anything associated with room modes that might be causing the issue at ~75Hz.  You should experiment with the sub/mains phase adjustments.

 

I think we should wait for Jason's opinion regarding whether bass treatments might be a solution for you.  For example, I have 96 sq ft of bass traps (eight 4x2 velocity traps, half from RealTraps, the other half from GIK).  Even though the treatments are not in a dedicated HT room, I am single and don't have WAF issues to deal with.

 

Ok, I will take some measurements with the MLP shifted to the left approx. 18-24" as this is where I usually sit.  I was using the mid point of the room as MLP with the hope of getting a more even calibration across the couch but your point about the null is duly noted.  I can go to town on the front wall (behind the false wall) but the first reflections could be problematic unless I go GIK with some artwork or maybe even a plain color that "works" with the room (so I've been told!).

 

What exactly do you mean by experimenting with the sub/mains phase adjustment?  Is this just modifying the distance setting for the sub in Audyssey or do you also mean experimenting with the LCR's?  Audyssey calculated the distance of the sub to approx. 18' 6" while the actual distance is somewhere between 13'-14'.  I know this isn't atypical for Audyssey so I didn't give it much thought but in a different room with the same sub, my DHC-80.3 pretty much pegged the sub distance to the physical distance.  The only other variable that I didn't mention is my left and right channels are hooked up to a McIntosh 2205 stereo amp.  This particular amp has separate gain controls for each channel (as well as an input voltage selector 2.5 or 0.75V) .  I did use OM's built-in SPL to gain match the LCR's to each other as well as the sub prior to running Audyssey.  I was wondering why Audyssey set the crossover of the center to 70 Hz but the left and right to 90 Hz and so then I was wondering if the amp difference had anything to do with it?  I also have a 5 channel McIntosh 7205 amp (for center and 4 surrouds) so if anyone recommends a different configuration for the 2 + 5 channels let me know.  I was thinking I could take advantage of using the 2205 in stereo mode with the current configuration but TBH, I'm heavily movie biased in my content and most music I listen to is mch.

 

I was wondering if you played around at all with generating waterfalls as this is completely new for me and I'm just getting my arms around understanding FR curves?  I have been reading a ton lately though and I'm beginning to understand the significance of the time domain.

post #718 of 9570
Quote:
Originally Posted by jevansoh View Post

Hi Nyal,

We haven't had the pleasure of meeting or speaking before. Although I don't know you and am not familiar with your work, I know Jeff and his work very well and respect him very much.

I'd love to have further conversations with you since we don't exactly have the largest pool of acousticians and acoustical consultants to pick from when seeking new friends with our common interests.

With that being said and with all due respect, I must humbly disagree with several recommendations your white paper recommends, though.

Hi, I do not want to derail this thread, but I would like to answer some of your specific questions and also provide some more on where we are coming from.

The main thing to bear in mind is that our perspective is that acoustical model are just imperfect representations of reality. Each model is a by product of a particular time in history. As acousticians learn more and have better tools available to them the models change. I do not think you have to design a room based on any one acoustical model.

The white paper represents a 'stake in the ground' by Jeff and I and is a statement of our current knowledge, understanding and real world experience in designing and implementing room acoustic solutions for two channel systems. The targets describe a room that has good spectral balance in the direct and reflected sounds in the midrange/treble and reasonably flat response with low modal ringing in the bass frequencies. Many of the room models do not cover all the aspects of room acoustics that Jeff and I think are important. For example LEDE focuses nearly exclusively on the use of ETC, to the detriment of a lot of other things, and without covering the potential issues in general use of the ETC.

The targets are NOT easy to achieve in the context of a two channel system. I have measured many rooms and none meet the targets in the white paper without effort and acoustic treatment. Like I said earlier I believe that with EQ and subs the low frequency targets can be substantially tightened up for home theater applications. We think that if the targets are met and / or exceeded then your room will not be a detriment your overall reproduction experience. This is based on our real world experience of many hundreds of two channel rooms.

There are many ways to meet the targets without having to be forced into designing to meet a LEDE, NE, or other type of room.

With the above high level overview of our position on acoustic models etc let me just briefly comment on some of your particulars...
Quote:
Originally Posted by jevansoh View Post

First, why do you feel the ETC should show "10db reduction by 40ms?" Do you not believe in an ISD Gap? Do you not believe early reflections high in amplitude are destructive? Do you not believe in the termination of the ITG?

LEDE standards are pretty clear that energy should not be above -20db from 0 to "around" 20ms or so to create an effectively anechoic gap which is then strongly terminated to increase the apparent size of the room and so the direct signal has time to form free of clutter. This will reduce muddiness and improve the listening experience with absolutely no argument against doing this from most well respected people in the field. What would the purpose of having a ton of high energy reflections all the way out to 40ms only 10db down be?

- 10dB reduction is to ensure that the precedence effect does not break down and that reflected sounds are not audible as echos. You should read the target as 'AT LEAST' 10dB, not 'JUST' 10dB.
- I do not believe all 'strong early reflections' are destructive. I am in the 'Toole' camp when it comes to that.
- I do not believe in designing LEDE rooms for reproduction so any discussion of ISD is not relevant to me. LEDE was to me a product of a particular age of studio building and the use of particular speakers with poor off axis performance in that era.
Quote:
Originally Posted by jevansoh View Post


Second, you reference RT60, 30, 20 yet there is absolutely NO REVERB TIME in Small Acoustical Spaces!! I'm SURE you know this. You stated these targets you set were for two-channel and you may amend them for home theater so this paper was obviously not written for concert halls, yet you reference taking RT measurements!

While looking at modal decay times and insuring they are even and contained to the appropriate range for the size of the room and the actual proven acoustical model targeted is necessary you won't find it by looking at the RT60 nor will that measurement help for the mid-hi frequencies either.

You can simply use the ETC and Cumulative Spectral Decay plot to find decay times and setting specific decay targets without taking into consideration the model, the room, etc, in my opinion is far from ideal.

You suggest targeting between .2 and .5 seconds with not much more explanation than that, but that is a HUGE difference. A room that has an overall average decay time of .2 seconds will sound quite dead no matter the size, especially considering you stated this document was created with two channel in mind, whereas with HT you'd at least have the surrounds so .2 wouldn't be so dead and dry, yet .5 in small rooms can be WAY too long. So have you defined specific targets for specific rooms in this new model of yours? What are the "why's" behind these numbers or are they just arbitrary limits you selected?

- Of course I know there is no RT in small rooms.
- The main use of the 'T' measures is to look at how sound is decaying across different frequency bands. It's another way of looking at the spectral balance in the room.
- You are wrong that a room of 0.2s will sound dry. Small rooms with a lot of diffusion can have 0.2s and sound normal.
Quote:
Originally Posted by jevansoh View Post


Next, you suggest a +/- 10db FR in the low frequencies at 1/24th smoothed! That isn't much of a goal! First, low frequencies should NEVER be smoothed at all. We need to see all the resolution possible here. Second, a 20db swing is worse than most people that have taken 5 minutes to "try" will ever see, especially now that RC software like Audyssey is now so popular. Anybody that would actually be reading your paper or this post is not going to accept a 20db swing in the most important frequency band in the audible spectrum whether 1/24th, 1/48th, or totally unsmoothed, which is the only way the FR should be viewed in this range.

- our intent for the target was a 10dB window rather than +/-10dB. This needs revising. In the context of a two channel WITH NO SUBS OR ROOM CORRECTION this is a hard target to achieve.
- of course low frequencies should be smoothed. We don't hear the unsmoothed frequency response. It's only relevance is to precisely identify the frequency of peaks or dips.
Quote:
Originally Posted by jevansoh View Post


As for decay times, should not the target be simply as even throughout the entire audible spectrum as possible with as little deviation as possible?

Again, it may not be likely that everyone will be able to get to within 10% of the full spectrum regarding decay times like the BBC demands for its rooms, but if you don't set the goal and understand the importance of ringing and vastly different decay times, especially in the lower frequencies, then your "critical" listening room is going to sound pretty bad.

--J

- the targets for the time decay are relaxed in the ultra low bass for a number of reasons including general lack of musical content <35Hz (remember this is two channel, not HT) and the difficulty of achieving the targeted decay time targets in the low bass.
Edited by Nyal Mellor - 1/28/13 at 12:22pm
post #719 of 9570
Quote:
Originally Posted by AustinJerry View Post

Quote:
Originally Posted by kbarnes701 View Post

 

Isn't 8 x 4 x 2, 64 sq ft, Jerry? Or am I missing something?  Is the 'missing' 32 sq feet the edges of the traps? I am not asking to be a pedantic clot, but because I would like to work out the sq footage of my own traps (GIK) in relation to the room size.

 

You pedantic clot, of course it is 64 sq ft.  redface.gif   And I had a minor in math when I went to college....

 

Hahaha. I've read that with traps of the GIK design, you can take into account the edges too as they allow bass absorption, thus increasing the effective area of the trap. I was (genuinely) wondering whether you were including that. The 4 inch edge of the trap adds another 4 sq ft to the overall area, which across 8 traps is the 32 you mentioned. Maybe we're both right ;)

post #720 of 9570
Quote:
Originally Posted by jkasanic View Post

What exactly do you mean by experimenting with the sub/mains phase adjustment?  Is this just modifying the distance setting for the sub in Audyssey or do you also mean experimenting with the LCR's?  Audyssey calculated the distance of the sub to approx. 18' 6" while the actual distance is somewhere between 13'-14'.  I know this isn't atypical for Audyssey so I didn't give it much thought but in a different room with the same sub, my DHC-80.3 pretty much pegged the sub distance to the physical distance.  

 

Yes - experiment with the sub distance while measuring the effect. The sub 'distance' is really a delay, so changing the delay changes the phase relationship between the mains and the sub. There may be a delay setting that provides a better integration of the subs + mains. In fact I can't recall anyone who has tried it who didn't find an improvement, except Jeff (pepar). It made a substantial difference for me.  This is one of Audyssey's weaknesses which we can overcome with independent measuring - Audyssey measures the speakers separately, and the sub(s) separately but never measures the combined result of the mains plus subs together.

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