Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs - Page 220 - AVS Forum
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post #6571 of 11306 Old 11-09-2013, 02:40 PM
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Originally Posted by AustinJerry View Post

So, forgetting for a moment the cost, is anyone seeing a worthwhile improvement, or should I, like Jim recommends, re-measure without moving the mic?

Remember, I can still return the product, although I would incur a $240 shipping expense.

 

I'd remeasure without moving the mic just to be sure what effect they are actually having.

 

I’d try to negotiate the return cost on a 50-50 basis - you are a good customer and the traps haven’t exactly performed as described...

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post #6572 of 11306 Old 11-09-2013, 02:48 PM
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Ok, I' ll try and re-measure tonight.
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post #6573 of 11306 Old 11-09-2013, 02:53 PM
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Very good point. When you put it like that... 

I think it means I won't bother with them. I only have physical room for 4 at the most and for the difference they appear to make I don't think they are worth the price. I know we are chasing ever more diminishing returns, but for $1,000 I'd be wanting more than they appear to be able to do. Even if I had space for more, at what price would any improvement come? 2 grand, 3 grand??

I wouldn't spend $3K on this given the entire "even if it works there's diminishing returns" aspect, but how different is this in spirit from moving from two to four HSUs or replacing relatively capable subs with Seatons to go to 10 Hz? Although I will argue that more even bass FR response looks like it's doing more LOL on a graph....

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post #6574 of 11306 Old 11-09-2013, 03:11 PM
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Quote:
Originally Posted by AustinJerry View Post

So, forgetting for a moment the cost, is anyone seeing a worthwhile improvement, or should I, like Jim recommends, re-measure without moving the mic?
I do see the small improvement you pointed out, but I don't think it's worthwhile. Since you already have the traps, do what Jim suggests. IF trying them at other locations doesn't yield improvements, then...
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...return the product, although I would incur a $240 shipping expense.
BTW, have you mentioned any of this to GIK? They must be aware of how many people read your posts.

Sanjay
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post #6575 of 11306 Old 11-09-2013, 03:53 PM
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Originally Posted by kbarnes701 View Post

I'd remeasure without moving the mic just to be sure what effect they are actually having.

I’d try to negotiate the return cost on a 50-50 basis - you are a good customer and the traps haven’t exactly performed as described...

That was what I was thinking. If you have followed Brian's direction and they haven't performed as advertised then...
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post #6576 of 11306 Old 11-09-2013, 04:42 PM
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Quote:
Originally Posted by kbarnes701 View Post

Very good point. When you put it like that... 

I think it means I won't bother with them. I only have physical room for 4 at the most and for the difference they appear to make I don't think they are worth the price. I know we are chasing ever more diminishing returns, but for $1,000 I'd be wanting more than they appear to be able to do. Even if I had space for more, at what price would any improvement come? 2 grand, 3 grand??

I wouldn't spend $3K on this given the entire "even if it works there's diminishing returns" aspect, but how different is this in spirit from moving from two to four HSUs or replacing relatively capable subs with Seatons to go to 10 Hz? Although I will argue that more even bass FR response looks like it's doing more LOL on a graph....

 

I don't think it's a good analogy. Buying my Submersives made a vast improvement not an incremental one. And not only wrt to digging down to 10Hz, but for the entire bass range they handle, not to mention other benefits right through the frequency spectrum. I think SubMs have to be heard (and felt) to be truly appreciated. I’d happily spend 5 grand to get that sort of improvement - but to spend 1 grand for the small difference the Scopus traps have made to Jerry's room is not cost-beneficial IMO. I suspect that if Jerry had spent $1,000 on 'conventional' treatments he'd have made a bigger improvement.

 

Having said all this, I would like to take a moment to say how much I admire Jerry's determination and his persistence of approach. He has been a genuine inspiration to me (and to others I am sure).

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post #6577 of 11306 Old 11-09-2013, 04:54 PM
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Originally Posted by kbarnes701 View Post

I don't think it's a good analogy. Buying my Submersives made a vast improvement not an incremental one. And not only wrt to digging down to 10Hz, but for the entire bass range they handle, not to mention other benefits right through the frequency spectrum. I think SubMs have to be heard (and felt) to be truly appreciated. I’d happily spend 5 grand to get that sort of improvement - but to spend 1 grand for the small difference the Scopus traps have made to Jerry's room is not cost-beneficial IMO. I suspect that if Jerry had spent $1,000 on 'conventional' treatments he'd have made a bigger improvement.

Having said all this, I would like to take a moment to say how much I admire Jerry's determination and his persistence of approach. He has been a genuine inspiration to me (and to others I am sure).

Joking aside, his comtinued experimentation and commitment to measuring, as well as finding new areas to tweak, is a role model for us all. Without the two of you to flesh out J's initial ideas, many more of us would just be enjoying our systems, sadly...biggrin.gif

Stuart

 

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post #6578 of 11306 Old 11-09-2013, 04:57 PM
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Quote:
Originally Posted by kbarnes701 View Post

I don't think it's a good analogy. Buying my Submersives made a vast improvement not an incremental one. And not only wrt to digging down to 10Hz, but for the entire bass range they handle, not to mention other benefits right through the frequency spectrum. I think SubMs have to be heard (and felt) to be truly appreciated. I’d happily spend 5 grand to get that sort of improvement - but to spend 1 grand for the small difference the Scopus traps have made to Jerry's room is not cost-beneficial IMO. I suspect that if Jerry had spent $1,000 on 'conventional' treatments he'd have made a bigger improvement.

Having said all this, I would like to take a moment to say how much I admire Jerry's determination and his persistence of approach. He has been a genuine inspiration to me (and to others I am sure).

Joking aside, his comtinued experimentation and commitment to measuring, as well as finding new areas to tweak, is a role model for us all. Without the two of you to flesh out J's initial ideas, many more of us would just be enjoying our systems, sadly...biggrin.gif

 

LOL - yeah - we don't want that, do we!  Not when there is measuring to be done.... :)

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post #6579 of 11306 Old 11-09-2013, 05:19 PM
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Ok, we have a plan:
- re-run the measurements, being careful not to move the mic.
- Publish the results tomorrow for feedback.
- If improvements are not significant (whatever that means), report disappointment to GIK for comments/advice.
- if still no satisfaction, return the product for credit.
- Apply credit to upgrade to Submersives (just kidding...)
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post #6580 of 11306 Old 11-09-2013, 05:58 PM
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ok here is what was requested:

waterfall with updated ms and R L SW for sub frequencies:




thoughts...fyi completely untreated room

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http://www.avsforum.com/forum/15-general-home-theater-media-game-rooms/1596161-sadiemax-theater-build-thread.html
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post #6581 of 11306 Old 11-09-2013, 06:15 PM
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post #6582 of 11306 Old 11-09-2013, 06:17 PM
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Not bad at all, Brian!
Sweet smile.gif thanks!!

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post #6583 of 11306 Old 11-09-2013, 07:23 PM
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My experience--tuned membrane traps.

Background:  My room is already heavily treated for bass resonances, but there are still resonances around the 40Hz range that have been difficult to control.  I have been interested in tuned membrane traps because they are designed to tame a very specific and narrow frequency band.  Having done a lot of business with GIK, I researched their Scopus product, which is a tuned membrane trap coming in three standard models, the T-40, T-70, and T-100, targeted for 40Hz, 70Hz, and 100Hz, respectively.  Each is a 2'x2' panel, varying in thickness from 4.5" for the T-70 and T-100, and 10.25" for the T-40.  GIK will build special-order Scopus traps that target any frequency at no additional cost.

I have limited space left in my listening room, and felt that I could accommodate no more then four panels.  I ordered them, and they arrived earlier this week:




The traps are a plywood box, sealed in back, and covered with the typical GIK fabric. The traps are heavy, 30lbs each.  Build quality is good.

I have received differing recommendations regarding where to place the traps to maximize effectiveness.  Some have recommended placing the traps according to which room dimension is creating the standing wave.  Others recommended generating a standing wave at the target frequency using REW's signal generator, and then measuring the SPL at various potential mounting locations. looking for the highest SPL.  I decided on the latter method.  As expected, locations at boundaries between walls, wall and floor, and wall and ceiling produced the highest SPL readings.  The highest reading, by almost 10dB, was along the front wall on the floor.  That is where I placed the traps:




I took careful measurements before and after installing the traps, being careful to place the mic in the same spot.  results:



































So, how effective are the membrane traps?  A slight frequency response at 48Hz is several dB's better.  It's hard to say, but the Waterfalls may show a slight improvement below 40Hz.  The Spectrogram, our new favorite measurement, shows a decrease in ringing at 40Hz, from 620ms to 490ms, which isn't bad.

So, given the expense of the four Scopus traps, did I get my money's worth?  Not sure.  Feedback would be appreciated.
Very interested in the results after remeasuring.

At first, I was as disappointed as Sanjay and Markus as the after results look worse than the before. When I examined the graphs more closely though, I began to notice a few more things.

I'm not sure when you took the before graphs vs the after, or how, but the Before graphs seem to have different SPL levels vs the After along with different frequency responses, so it's not an apples to apples comparison (the After graphs appear to have an at least ~5db higher overall SPL that extends all the way to the top of the frequency range (which the Scopus traps definitely shouldn't be affecting.

While the waterfalls, on cursory inspection, appear to show worse results, I couldn't figure out why the first 2 and last 2 looked quite different. I'm assuming it might be mic placement, but once again, flipping between the Before and After graphs seems to show a increased SPL level overall with the After graphs. The decay appears to be worse in the After graphs in the 40Hz region though, which is disappointing. If you look closely at the 40Hz region in the waterfalls though, there are different things going on in the first 2 vs last 2 waterfalls. The 3rd waterfall seems to indicate some kind of artifact at 40Hz that doesn't seem to decay into the noise floor. Not sure what's going on there.

It's the spectrograms that I find interesting though, as the After seems to show less ringing below 50Hz than the Before.


Jerry,

if you haven't done so already, could you try taking the Before and After measurements at the current Scopus placements with the mic at the MLP with the same SPL levels, and then try again with the traps propped up mid-wall on the length and then width walls? I'm interested to see how these factors affect the results.


Max
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post #6584 of 11306 Old 11-09-2013, 07:33 PM
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if you haven't done so already, could you try taking the Before and After measurements at the current Scopus placements with the mic at the MLP with the same SPL levels, and then try again with the traps propped up mid-wall on the length and then width walls? I'm interested to see how these factors affect the results.


Max

Max, not sure I understand. What do you me by "propped up"? The traps are currently on the width wall. I don't really have room anywhere on the length wall to place the traps, certainly not at the midpoint. I am open to suggestions if you could be more clear.
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post #6585 of 11306 Old 11-09-2013, 09:10 PM
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I'm pretty sure he means having the traps placed at a point on the wall above the floor. But I think we all concur that the best placement is where SPL is highest.
HST, if you have time to spare and a means of raising the traps, why not!

I do agree that the SPL appears to be different in your before and afters though.
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post #6586 of 11306 Old 11-09-2013, 09:25 PM
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I'm pretty sure he means having the traps placed at a point on the wall above the floor. But I think we all concur that the best placement is where SPL is highest.
HST, if you have time to spare and a means of raising the traps, why not!

I do agree that the SPL appears to be different in your before and afters though.

 

I have identified several alternate locations where I will place the traps tomorrow morning.  WRT the SPL levels, was difficult with the initial measurements to keep the SPL the same.  In between the "before" and "after" measurements, the laptop was used for an Audyssey Pro calibration and, of course, the REW mic was removed during the calibration.  It is difficult to establish the same SPL when using an RS SPL to calibrate the mic.

 

For tomorrow's exercise, the mic will never move, and the REW calibrated mic level will remain the same.  This should eliminate the SPL issue that was observed.

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post #6587 of 11306 Old 11-09-2013, 09:32 PM
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I have identified several alternate locations where I will place the traps tomorrow morning.  WRT the SPL levels, was difficult with the initial measurements to keep the SPL the same.  In between the "before" and "after" measurements, the laptop was used for an Audyssey Pro calibration and, of course, the REW mic was removed during the calibration.  It is difficult to establish the same SPL when using an RS SPL to calibrate the mic.

For tomorrow's exercise, the mic will never move, and the REW calibrated mic level will remain the same.  This should eliminate the SPL issue that was observed.
Sounds good. The consistency will help isolate the resulting differences.
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if you haven't done so already, could you try taking the Before and After measurements at the current Scopus placements with the mic at the MLP with the same SPL levels, and then try again with the traps propped up mid-wall on the length and then width walls? I'm interested to see how these factors affect the results.


Max

Max, not sure I understand. What do you me by "propped up"? The traps are currently on the width wall. I don't really have room anywhere on the length wall to place the traps, certainly not at the midpoint. I am open to suggestions if you could be more clear.
Yes, I meant trying them propped up height-wise about mid-wall as opposed to the wall-floor intersection to see if that has any effect. As for the length wall, is there any way you can try placing them on your rear wall just to test the results out?


Max

P.S. Just looked at your room pics again. If you placed the Scopus traps under your TV, isn't that the length wall? To avoid confusion where we might not know (or might have forgotten) what dimensions the room is and which walls are longer, I'm using Sanjay's convention of labeling the front and rear walls relative to the MLP, the 'length', and the walls to your sides being width (to avoid confusion of length vs width where some folks might have rooms that are wider than they are deep, or vice-versa).

That said, if you've tried the under the TV placement (which I consider a room length placement), could you try a width placement on the right side of the room where those panels above the low cabinet with the lamp are?
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post #6588 of 11306 Old 11-09-2013, 09:39 PM
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es, I meant trying them propped up height-wise about mid-wall as opposed to the wall-floor intersection to see if that has any effect. As for the length wall, is there any way you can try placing them on your rear wall just to test the results out?

While I agree that it can't hurt to try different positions, there needs to be a way to determine the "why", either before or after trying a new mounting position.

Advice for placing membranes (as the thread moves forward) should involve more then, "try here".
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post #6589 of 11306 Old 11-09-2013, 09:50 PM
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Sounds good. The consistency will help isolate the resulting differences.
es, I meant trying them propped up height-wise about mid-wall as opposed to the wall-floor intersection to see if that has any effect. As for the length wall, is there any way you can try placing them on your rear wall just to test the results out?


Max

P.S. Just looked at your room pics again. If you placed the Scopus traps under your TV, isn't that the length wall? To avoid confusion where we might not know (or might have forgotten) what dimensions the room is and which walls are longer, I'm using Sanjay's convention of labeling the front and rear walls relative to the MLP, the 'length', and the walls to your sides being width (to avoid confusion of length vs width where some folks might have rooms that are wider than they are deep, or vice-versa).

 

The wall where the display is mounted is what I call the width, and it is 19.5'.  The length of the room is the side walls, and they are 16.5'.  There is no back wall--it is open to the rest of the ground floor, with only a 48" wide piece of wall, which is currently covered with broadband panels, with two ULS-15 subs at the base.

 

As I said, I have identified a couple of other spots.  One involves elevating the Scopus traps about 30" above the ground along one side wall.  The other is on the opposite side wall, towards the front, with the traps stacked two high, making a 48"x48" square.  Other alternatives would be to mount the traps on the wall, which I don't want to do for this exercise.  Mounting 30 lb. panels is not a trivial exercise.

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post #6590 of 11306 Old 11-09-2013, 09:51 PM
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While I agree that it can't hurt to try different positions, there needs to be a way to determine the "why", either before or after trying a new mounting position.

Advice for placing membranes (as the thread moves forward) should involve more then, "try here".

 

I chose the original location based on max SPL for a 40Hz sine wave, which I thought was a reasonable approach.

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post #6591 of 11306 Old 11-09-2013, 09:52 PM
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es, I meant trying them propped up height-wise about mid-wall as opposed to the wall-floor intersection to see if that has any effect. As for the length wall, is there any way you can try placing them on your rear wall just to test the results out?

While I agree that it can't hurt to try different positions, there needs to be a way to determine the "why", either before or after trying a new mounting position.

Advice for placing membranes (as the thread moves forward) should involve more then, "try here".
Although the general convention is that membrane type traps are pressure-based and are most effective placed in regions where you see the highest pressures at the targeted frequencies, I've seen some discussion about effective placements for them being centered on flat walls vs in corners, hence the request to try mid-height placement. I suppose that's something that GIK should be able to answer seeing as they designed and built these specific traps and would have experience with their effective placement.

As for trying the width vs his initial length placements, That is to see if the ringing in the particular frequency range is due to bouncing between the side walls.
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post #6592 of 11306 Old 11-09-2013, 10:13 PM
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Sounds good. The consistency will help isolate the resulting differences.

es, I meant trying them propped up height-wise about mid-wall as opposed to the wall-floor intersection to see if that has any effect. As for the length wall, is there any way you can try placing them on your rear wall just to test the results out?



Max


P.S. Just looked at your room pics again. If you placed the Scopus traps under your TV, isn't that the length wall? To avoid confusion where we might not know (or might have forgotten) what dimensions the room is and which walls are longer, I'm using Sanjay's convention of labeling the front and rear walls relative to the MLP, the 'length', and the walls to your sides being width (to avoid confusion of length vs width where some folks might have rooms that are wider than they are deep, or vice-versa).

The wall where the display is mounted is what I call the width, and it is 19.5'.  The length of the room is the side walls, and they are 16.5'.  There is no back wall--it is open to the rest of the ground floor, with only a 48" wide piece of wall, which is currently covered with broadband panels, with two ULS-15 subs at the base.

As I said, I have identified a couple of other spots.  One involves elevating the Scopus traps about 30" above the ground along one side wall.  The other is on the opposite side wall, towards the front, with the traps stacked two high, making a 48"x48" square.  Other alternatives would be to mount the traps on the wall, which I don't want to do for this exercise.  Mounting 30 lb. panels is not a trivial exercise.
The bolded part is why I asked if you could prop them up as opposed to trying to mount them.

I looked at my post and I still didn't address it clearly.

Sanjay (and I) find that a convention of labeling the front-to-back dimension the room 'length' and the side-to-side dimension the room 'width' a less confusing convention than basing it on the room's dimensions.

For example, if we use the convention of labeling the longest wall 'length', with 2 different setups where A's room is setup so that their front and rear walls are 20 feet and their side walls are 15 feet, and B has a room the exact same size, but B's setup is oriented so their front and rear walls are the 15' walls and the side walls are 20', it can be confusing to know who means what when talking about length vs width, and with the number of participants in the thread, it gets more confusing needing to recall whose setup is oriented which way. Sticking to calling the front-to-rear dimension the room length and the side-to-side dimension the room width avoids that confusion, i.e. some rooms can be wider than they are long, and some rooms can be longer than they are wide, but the label of width as the distance/dimension from side wall to side wall remains the same.

Your last paragraph detailing the extra positions is what I was asking. I'm assuming when you mentioned the position with the traps elevated 30", you might be talking about the placing them on the sideboard on the right side of the room that I mentioned in the post above? The position on the forward left side wouuld be near the front corner on the left wall? Those would be what I consider width placements in you room and I'm interested to see the results of those.

The other placement I was wondering about, is related to the discussions I've encountered elsewhere about placing membrane traps at plane intersections vs in the middle of the plane/wall, and is where your rear broadband panels are, if you could place them there on a bench or stools etc. as we're trying to see what effect it would have on the problematic frequency region. If this placement tends to show better results than the under the TV placement, then it might be conceivable that mounting them above the TV could also work, but I would think it's a lot more trouble trying that than propping them mid-height on the back wall.


Max

P.S. One last suggestion is to use the same, light-colors for the before and after waterfall graphs. The lighter colors are easier to see and using the same color makes comparison of the before and after easier.
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Keeping the labeling of length and width consistent is well advised. smile.gif

Wouldn't mounting pressure based traps freestanding on their own, clearly diminish their effectiveness?
I would assume that even just leaning them against a rigid wall would increase their working ability. Any minor movements in the device, even those not noticeable to the naked eye would reduce their effectiveness?
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post #6594 of 11306 Old 11-10-2013, 12:16 AM
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Why measure only the sub+left unsmoothed?  Do you have sub+left+right un-smoothed?

Audyssey is a single speaker optimization so it makes sense to measure single speakers. They also claim to optimize the crossover to the subs so it makes sense to measure single speaker plus sub.
In order to check how good Audyssey's optimization approach works with signals that are present in more than one speaker (e.g. bass is typically mixed to the center, i.e. it is in the L and R channel), measure any combination of speakers, e.g. L+R+Sub.

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Ok, we have a plan:
- re-run the measurements, being careful not to move the mic.
- Publish the results tomorrow for feedback.
- If improvements are not significant (whatever that means), report disappointment to GIK for comments/advice.
- if still no satisfaction, return the product for credit.
- Apply credit to upgrade to Submersives (just kidding...)

In order to see if those 4 lonely traps do anything substantial I would place the mic into a room corner where all modes can be measured at their max. One measurement with the traps in the room, one measurement without the traps.

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Max, I think Jerry is using length & width the way most of us do. When he says his front wall spans the width of the room, he means width as in left to right.

Sanjay
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post #6597 of 11306 Old 11-10-2013, 01:41 AM
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Quote:
Originally Posted by Audionut11 View Post

Keeping the labeling of length and width consistent is well advised. smile.gif

Wouldn't mounting pressure based traps freestanding on their own, clearly diminish their effectiveness?
I would assume that even just leaning them against a rigid wall would increase their working ability. Any minor movements in the device, even those not noticeable to the naked eye would reduce their effectiveness?
Yes, I wasn't advocating having them freestanding in the open, but placed against the walls. Since they're 10.25" thick and 30lbs, instead of hanging them in various placement locations, I suggested placing/propping them there temporarily.


Max
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P.S. One last suggestion is to use the same, light-colors for the before and after waterfall graphs. The lighter colors are easier to see and using the same color makes comparison of the before and after easier.

 

Max,

 

I am running the new measurements now.  Before I publish, what do you mean by "light colors"?  I usually select red or blue.  I will use the same color for each graph this time.

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Quote:
Originally Posted by djbluemax1 View Post

P.S. One last suggestion is to use the same, light-colors for the before and after waterfall graphs. The lighter colors are easier to see and using the same color makes comparison of the before and after easier.

Max,

I am running the new measurements now.  Before I publish, what do you mean by "light colors"?  I usually select red or blue.  I will use the same color for each graph this time.
You can select the colors from the color palette, and even with red for example, you can select a shade of red that is lighter (more like an orange or salmon). It makes the waterfall contour lines much easier to see vs something like a dark blue. Even the light yellows which I normally stay away from for FR graphs show up well for waterfalls.


Max
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Scopus Tuned Bass Trap Placement Measurements

 

I have completed the exercise in which I placed the four Scopus traps at several alternative locations around the room and measured effectiveness at each location.

 

Notes on the testing process:

 

- The REW mic was placed at the MLP at ear level and not moved during the testing.

- The mic was calibrated once at the beginning of the testing and not changed during the testing.

- Audyssey RC was turned off during testing.

- Five measurements were taken for each location:  Left Front, Right Front, Left+right, Center (all 15-20000Hz), and 4 subs only (15-300Hz)

- At none of the locations were the panels "tightly coupled" with the wall, if this makes a difference.

 

The locations were:

 

Front wall below flat panel:

 

 

Back wall, 26" off the floor, stacked two high:

 

 

Left wall towards front of the room, on the floor, stacked two high:

 

 

 

Right wall, midpoint, 26" off the floor, stacked two high:

 

 

A fifth set of measurements was taken with the traps completely removed.

 

To avoid expectation bias, measurements will be presented identified only as "Position 1", "Position 2", etc., without saying which position is which.  Please review the measurements and opine WRT which looks better and why.

 

 

 

 

 

 

Spectrogram cursor was placed at the highest "peak":

 

 

 

 

 

 

 

For anyone who might want to slice the data differently, I have uploaded the MDAT file here:  https://dl.dropboxusercontent.com/u/78476446/All%20five%20positions.mdat

 

Open for comments....

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